Old Test Deletion

Cross-mode Quota Locks, Masking Prefetch & Tiny-Frame Debt Protection

.github/workflows/rust.yml

@@ -11,7 +11,7 @@ env:
 
 jobs:
   build:
-    name: Build
+    name: Compile, Test, Lint
     runs-on: ubuntu-latest
 
     permissions:
@@ -39,23 +39,11 @@ jobs:
         restore-keys: |
           ${{ runner.os }}-cargo-
 
-    - name: Build Release
-      run: cargo build --release --verbose
+    - name: Compile (no tests)
+      run: cargo check --workspace --all-features --lib --bins --verbose
 
-    - name: Run tests
-      run: cargo test --verbose
-
-    - name: Stress quota-lock suites (PR only)
-      if: github.event_name == 'pull_request'
-      env:
-        RUST_TEST_THREADS: 16
-      run: |
-        set -euo pipefail
-        for i in $(seq 1 12); do
-          echo "[quota-lock-stress] iteration ${i}/12"
-          cargo test quota_lock_ --bin telemt -- --nocapture --test-threads 16
-          cargo test relay_quota_wake --bin telemt -- --nocapture --test-threads 16
-        done
+    - name: Run tests (single pass)
+      run: cargo test --workspace --all-features --verbose
 
 # clippy dont fail on warnings because of active development of telemt 
 # and many warnings

.github/workflows/stress.yml

@@ -0,0 +1,57 @@
+name: Stress Tests
+
+on:
+  workflow_dispatch:
+  schedule:
+    - cron: '0 2 * * *'
+  pull_request:
+    branches: ["*"]
+    paths:
+      - src/proxy/**
+      - src/transport/**
+      - src/stream/**
+      - src/protocol/**
+      - src/tls_front/**
+      - Cargo.toml
+      - Cargo.lock
+
+env:
+  CARGO_TERM_COLOR: always
+
+jobs:
+  quota-lock-stress:
+    name: Quota-lock stress loop
+    runs-on: ubuntu-latest
+
+    permissions:
+      contents: read
+
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+
+      - name: Install latest stable Rust toolchain
+        uses: dtolnay/rust-toolchain@stable
+
+      - name: Cache cargo registry and build artifacts
+        uses: actions/cache@v4
+        with:
+          path: |
+            ~/.cargo/registry
+            ~/.cargo/git
+            target
+          key: ${{ runner.os }}-cargo-stress-${{ hashFiles('**/Cargo.lock') }}
+          restore-keys: |
+            ${{ runner.os }}-cargo-stress-
+            ${{ runner.os }}-cargo-
+
+      - name: Run quota-lock stress suites
+        env:
+          RUST_TEST_THREADS: 16
+        run: |
+          set -euo pipefail
+          for i in $(seq 1 12); do
+            echo "[quota-lock-stress] iteration ${i}/12"
+            cargo test quota_lock_ --bin telemt -- --nocapture --test-threads 16
+            cargo test relay_quota_wake --bin telemt -- --nocapture --test-threads 16
+          done

Cargo.lock

@@ -1454,9 +1454,9 @@ dependencies = [
 
 [[package]]
 name = "iri-string"
-version = "0.7.10"
+version = "0.7.11"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "c91338f0783edbd6195decb37bae672fd3b165faffb89bf7b9e6942f8b1a731a"
+checksum = "d8e7418f59cc01c88316161279a7f665217ae316b388e58a0d10e29f54f1e5eb"
 dependencies = [
  "memchr",
  "serde",
@@ -1486,7 +1486,7 @@ dependencies = [
  "cesu8",
  "cfg-if",
  "combine",
- "jni-sys",
+ "jni-sys 0.3.1",
  "log",
  "thiserror 1.0.69",
  "walkdir",
@@ -1495,9 +1495,31 @@ dependencies = [
 
 [[package]]
 name = "jni-sys"
-version = "0.3.0"
+version = "0.3.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "8eaf4bc02d17cbdd7ff4c7438cafcdf7fb9a4613313ad11b4f8fefe7d3fa0130"
+checksum = "41a652e1f9b6e0275df1f15b32661cf0d4b78d4d87ddec5e0c3c20f097433258"
+dependencies = [
+ "jni-sys 0.4.1",
+]
+
+[[package]]
+name = "jni-sys"
+version = "0.4.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c6377a88cb3910bee9b0fa88d4f42e1d2da8e79915598f65fb0c7ee14c878af2"
+dependencies = [
+ "jni-sys-macros",
+]
+
+[[package]]
+name = "jni-sys-macros"
+version = "0.4.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "38c0b942f458fe50cdac086d2f946512305e5631e720728f2a61aabcd47a6264"
+dependencies = [
+ "quote",
+ "syn",
+]
 
 [[package]]
 name = "jobserver"
@@ -1659,9 +1681,9 @@ dependencies = [
 
 [[package]]
 name = "moka"
-version = "0.12.14"
+version = "0.12.15"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "85f8024e1c8e71c778968af91d43700ce1d11b219d127d79fb2934153b82b42b"
+checksum = "957228ad12042ee839f93c8f257b62b4c0ab5eaae1d4fa60de53b27c9d7c5046"
 dependencies = [
  "crossbeam-channel",
  "crossbeam-epoch",
@@ -2771,7 +2793,7 @@ checksum = "7b2093cf4c8eb1e67749a6762251bc9cd836b6fc171623bd0a9d324d37af2417"
 
 [[package]]
 name = "telemt"
-version = "3.3.29"
+version = "3.3.30"
 dependencies = [
  "aes",
  "anyhow",

Cargo.toml

@@ -1,8 +1,11 @@
 [package]
 name = "telemt"
-version = "3.3.29"
+version = "3.3.30"
 edition = "2024"
 
+[features]
+redteam_offline_expected_fail = []
+
 [dependencies]
 # C
 libc = "0.2"

docs/CONFIG_PARAMS.en.md

@@ -20,7 +20,7 @@ This document lists all configuration keys accepted by `config.toml`.
 | Parameter | Type | Default | Constraints / validation | Description |
 |---|---|---|---|---|
 | data_path | `String \| null` | `null` | — | Optional runtime data directory path. |
-| prefer_ipv6 | `bool` | `false` | — | Prefer IPv6 where applicable in runtime logic. |
+| prefer_ipv6 | `bool` | `false` | Deprecated. Use `network.prefer`. | Deprecated legacy IPv6 preference flag migrated to `network.prefer`. |
 | fast_mode | `bool` | `true` | — | Enables fast-path optimizations for traffic processing. |
 | use_middle_proxy | `bool` | `true` | none | Enables ME transport mode; if `false`, runtime falls back to direct DC routing. |
 | proxy_secret_path | `String \| null` | `"proxy-secret"` | Path may be `null`. | Path to Telegram infrastructure proxy-secret file used by ME handshake logic. |
@@ -44,6 +44,7 @@ This document lists all configuration keys accepted by `config.toml`.
 | me_writer_cmd_channel_capacity | `usize` | `4096` | Must be `> 0`. | Capacity of per-writer command channel. |
 | me_route_channel_capacity | `usize` | `768` | Must be `> 0`. | Capacity of per-connection ME response route channel. |
 | me_c2me_channel_capacity | `usize` | `1024` | Must be `> 0`. | Capacity of per-client command queue (client reader -> ME sender). |
+| me_c2me_send_timeout_ms | `u64` | `4000` | `0..=60000`. | Maximum wait for enqueueing client->ME commands when the per-client queue is full (`0` keeps legacy unbounded wait). |
 | me_reader_route_data_wait_ms | `u64` | `2` | `0..=20`. | Bounded wait for routing ME DATA to per-connection queue (`0` = no wait). |
 | me_d2c_flush_batch_max_frames | `usize` | `32` | `1..=512`. | Max ME->client frames coalesced before flush. |
 | me_d2c_flush_batch_max_bytes | `usize` | `131072` | `4096..=2_097_152`. | Max ME->client payload bytes coalesced before flush. |
@@ -105,6 +106,8 @@ This document lists all configuration keys accepted by `config.toml`.
 | me_warn_rate_limit_ms | `u64` | `5000` | Must be `> 0`. | Cooldown for repetitive ME warning logs (ms). |
 | me_route_no_writer_mode | `"async_recovery_failfast" \| "inline_recovery_legacy" \| "hybrid_async_persistent"` | `"hybrid_async_persistent"` | — | Route behavior when no writer is immediately available. |
 | me_route_no_writer_wait_ms | `u64` | `250` | `10..=5000`. | Max wait in async-recovery failfast mode (ms). |
+| me_route_hybrid_max_wait_ms | `u64` | `3000` | `50..=60000`. | Maximum cumulative wait in hybrid no-writer mode before failfast fallback (ms). |
+| me_route_blocking_send_timeout_ms | `u64` | `250` | `0..=5000`. | Maximum wait for blocking route-channel send fallback (`0` keeps legacy unbounded wait). |
 | me_route_inline_recovery_attempts | `u32` | `3` | Must be `> 0`. | Inline recovery attempts in legacy mode. |
 | me_route_inline_recovery_wait_ms | `u64` | `3000` | `10..=30000`. | Max inline recovery wait in legacy mode (ms). |
 | fast_mode_min_tls_record | `usize` | `0` | — | Minimum TLS record size when fast-mode coalescing is enabled (`0` disables). |
@@ -124,6 +127,7 @@ This document lists all configuration keys accepted by `config.toml`.
 | me_secret_atomic_snapshot | `bool` | `true` | — | Keeps selector and secret bytes from the same snapshot atomically. |
 | proxy_secret_len_max | `usize` | `256` | Must be within `[32, 4096]`. | Upper length limit for accepted proxy-secret bytes. |
 | me_pool_drain_ttl_secs | `u64` | `90` | none | Time window where stale writers remain fallback-eligible after map change. |
+| me_instadrain | `bool` | `false` | — | Forces draining stale writers to be removed on the next cleanup tick, bypassing TTL/deadline waiting. |
 | me_pool_drain_threshold | `u64` | `128` | — | Max draining stale writers before batch force-close (`0` disables threshold cleanup). |
 | me_pool_drain_soft_evict_enabled | `bool` | `true` | — | Enables gradual soft-eviction of stale writers during drain/reinit instead of immediate hard close. |
 | me_pool_drain_soft_evict_grace_secs | `u64` | `30` | `0..=3600`. | Grace period before stale writers become soft-evict candidates. |
@@ -198,10 +202,14 @@ This document lists all configuration keys accepted by `config.toml`.
 | listen_tcp | `bool \| null` | `null` (auto) | — | Explicit TCP listener enable/disable override. |
 | proxy_protocol | `bool` | `false` | — | Enables HAProxy PROXY protocol parsing on incoming client connections. |
 | proxy_protocol_header_timeout_ms | `u64` | `500` | Must be `> 0`. | Timeout for PROXY protocol header read/parse (ms). |
+| proxy_protocol_trusted_cidrs | `IpNetwork[]` | `[]` | — | When non-empty, only connections from these proxy source CIDRs are allowed to provide PROXY protocol headers. If empty, PROXY headers are rejected by default (security hardening). |
 | metrics_port | `u16 \| null` | `null` | — | Metrics endpoint port (enables metrics listener). |
 | metrics_listen | `String \| null` | `null` | — | Full metrics bind address (`IP:PORT`), overrides `metrics_port`. |
 | metrics_whitelist | `IpNetwork[]` | `["127.0.0.1/32", "::1/128"]` | — | CIDR whitelist for metrics endpoint access. |
 | max_connections | `u32` | `10000` | — | Max concurrent client connections (`0` = unlimited). |
+| accept_permit_timeout_ms | `u64` | `250` | `0..=60000`. | Maximum wait for acquiring a connection-slot permit before the accepted connection is dropped (`0` keeps legacy unbounded wait). |
+
+Note: When `server.proxy_protocol` is enabled, incoming PROXY protocol headers are parsed from the first bytes of the connection and the client source address is replaced with `src_addr` from the header. For security, the peer source IP (the direct connection address) is verified against `server.proxy_protocol_trusted_cidrs`; if this list is empty, PROXY headers are rejected and the connection is considered untrusted. 
 
 ## [server.api]
 
@@ -226,7 +234,7 @@ This document lists all configuration keys accepted by `config.toml`.
 |---|---|---|---|---|
 | ip | `IpAddr` | — | — | Listener bind IP. |
 | announce | `String \| null` | — | — | Public IP/domain announced in proxy links (priority over `announce_ip`). |
-| announce_ip | `IpAddr \| null` | — | — | Deprecated legacy announce IP (migrated to `announce` if needed). |
+| announce_ip | `IpAddr \| null` | — | Deprecated. Use `announce`. | Deprecated legacy announce IP (migrated to `announce` if needed). |
 | proxy_protocol | `bool \| null` | `null` | — | Per-listener override for PROXY protocol enable flag. |
 | reuse_allow | `bool` | `false` | — | Enables `SO_REUSEPORT` for multi-instance bind sharing. |
 
@@ -266,6 +274,8 @@ This document lists all configuration keys accepted by `config.toml`.
 | mask_shape_bucket_cap_bytes | `usize` | `4096` | Must be `>= mask_shape_bucket_floor_bytes`. | Maximum bucket size used by shape-channel hardening; traffic above cap is not padded further. |
 | mask_shape_above_cap_blur | `bool` | `false` | Requires `mask_shape_hardening = true`; requires `mask_shape_above_cap_blur_max_bytes > 0`. | Adds bounded randomized tail bytes even when forwarded size already exceeds cap. |
 | mask_shape_above_cap_blur_max_bytes | `usize` | `512` | Must be `<= 1048576`; must be `> 0` when `mask_shape_above_cap_blur = true`. | Maximum randomized extra bytes appended above cap. |
+| mask_relay_max_bytes | `usize` | `5242880` | Must be `> 0`; must be `<= 67108864`. | Maximum relayed bytes per direction on unauthenticated masking fallback path. |
+| mask_classifier_prefetch_timeout_ms | `u64` | `5` | Must be within `[5, 50]`. | Timeout budget (ms) for extending fragmented initial classifier window on masking fallback. |
 | mask_timing_normalization_enabled | `bool` | `false` | Requires `mask_timing_normalization_floor_ms > 0`; requires `ceiling >= floor`. | Enables timing envelope normalization on masking outcomes. |
 | mask_timing_normalization_floor_ms | `u64` | `0` | Must be `> 0` when timing normalization is enabled; must be `<= ceiling`. | Lower bound (ms) for masking outcome normalization target. |
 | mask_timing_normalization_ceiling_ms | `u64` | `0` | Must be `>= floor`; must be `<= 60000`. | Upper bound (ms) for masking outcome normalization target. |

docs/FAQ.en.md

@@ -3,7 +3,7 @@
 1. Go to @MTProxybot bot.
 2. Enter the command `/newproxy`
 3. Send the server IP and port. For example: 1.2.3.4:443
-4. Open the config `nano /etc/telemt.toml`.
+4. Open the config `nano /etc/telemt/telemt.toml`.
 5. Copy and send the user secret from the [access.users] section to the bot.
 6. Copy the tag received from the bot. For example 1234567890abcdef1234567890abcdef.
 > [!WARNING]
@@ -33,6 +33,9 @@ hello = "ad_tag"
 hello2 = "ad_tag2"
 ```
 
+## Why is middle proxy (ME) needed
+https://github.com/telemt/telemt/discussions/167
+
 ## How many people can use 1 link
 
 By default, 1 link can be used by any number of people.  

docs/FAQ.ru.md

@@ -3,7 +3,7 @@
 1. Зайти в бота @MTProxybot.
 2. Ввести команду `/newproxy`
 3. Отправить IP и порт сервера. Например: 1.2.3.4:443
-4. Открыть конфиг `nano /etc/telemt.toml`.
+4. Открыть конфиг `nano /etc/telemt/telemt.toml`.
 5. Скопировать и отправить боту секрет пользователя из раздела [access.users].
 6. Скопировать полученный tag у бота. Например 1234567890abcdef1234567890abcdef.
 > [!WARNING]
@@ -33,6 +33,10 @@ hello = "ad_tag"
 hello2 = "ad_tag2"
 ```
 
+## Зачем нужен middle proxy (ME)
+https://github.com/telemt/telemt/discussions/167
+
+
 ## Сколько человек может пользоваться 1 ссылкой
 
 По умолчанию 1 ссылкой может пользоваться сколько угодно человек.  

docs/VPS_DOUBLE_HOP.en.md

@@ -0,0 +1,283 @@
+<img src="https://gist.githubusercontent.com/avbor/1f8a128e628f47249aae6e058a57610b/raw/19013276c035e91058e0a9799ab145f8e70e3ff5/scheme.svg">
+
+## Concept
+- **Server A** (__conditionally Russian Federation_):\
+  Entry point, receives Telegram proxy user traffic via **HAProxy** (port `443`)\
+  and sends it to the tunnel to Server **B**.\
+  Internal IP in the tunnel — `10.10.10.2`\
+  Port for HAProxy clients — `443\tcp`
+- **Server B** (_conditionally Netherlands_):\
+  Exit point, runs **telemt** and accepts client connections through Server **A**.\
+  The server must have unrestricted access to Telegram servers.\
+  Internal IP in the tunnel — `10.10.10.1`\
+  AmneziaWG port — `8443\udp`\
+  Port for telemt clients — `443\tcp`
+
+---
+
+## Step 1. Setting up the AmneziaWG tunnel (A <-> B)
+[AmneziaWG](https://github.com/amnezia-vpn/amneziawg-linux-kernel-module) must be installed on all servers.\
+All following commands are given for **Ubuntu 24.04**.\
+For RHEL-based distributions, installation instructions are available at the link above.
+
+### Installing AmneziaWG (Servers A and B)
+The following steps must be performed on each server:
+
+#### 1. Adding the AmneziaWG repository and installing required packages:
+```bash
+sudo apt install -y software-properties-common python3-launchpadlib gnupg2 linux-headers-$(uname -r) && \
+sudo add-apt-repository ppa:amnezia/ppa && \
+sudo apt-get install -y amneziawg
+```
+
+#### 2. Generating a unique key pair:
+```bash
+cd /etc/amnezia/amneziawg && \
+awg genkey | tee private.key | awg pubkey > public.key
+```
+
+As a result, you will get two files in the `/etc/amnezia/amneziawg` folder:\
+`private.key` - private, and\
+`public.key` - public server keys
+
+#### 3. Configuring network interfaces:
+Obfuscation parameters `S1`, `S2`, `H1`, `H2`, `H3`, `H4` must be strictly identical on both servers.\
+Parameters `Jc`, `Jmin` and `Jmax` can differ.\
+Parameters `I1-I5` ([Custom Protocol Signature](https://docs.amnezia.org/documentation/amnezia-wg/)) must be specified on the client side (Server **A**).
+
+Recommendations for choosing values:
+
+```text
+Jc — 1 ≤ Jc ≤ 128; from 4 to 12 inclusive
+Jmin — Jmax > Jmin < 1280*; recommended 8
+Jmax — Jmin < Jmax ≤ 1280*; recommended 80
+S1 — S1 ≤ 1132* (1280* - 148 = 1132); S1 + 56 ≠ S2;
+recommended range from 15 to 150 inclusive
+S2 — S2 ≤ 1188* (1280* - 92 = 1188);
+recommended range from 15 to 150 inclusive
+H1/H2/H3/H4 — must be unique and differ from each other;
+recommended range from 5 to 2147483647 inclusive
+
+* It is assumed that the Internet connection has an MTU of 1280.
+```
+
+> [!IMPORTANT]
+> It is recommended to use your own, unique values.\
+> You can use the [generator](https://htmlpreview.github.io/?https://gist.githubusercontent.com/avbor/955782b5c37b06240b243aa375baeac5/raw/e8b269ff0089a27effd88f8d925179b78e5666c4/awg-gen.html) to select parameters.
+
+#### Server B Configuration (Netherlands):
+
+Create the interface configuration file (`awg0`)
+```bash
+nano /etc/amnezia/amneziawg/awg0.conf
+```
+
+File content
+```ini
+[Interface]
+Address = 10.10.10.1/24
+ListenPort = 8443
+PrivateKey = <PRIVATE_KEY_SERVER_B>
+SaveConfig = true
+Jc = 4
+Jmin = 8
+Jmax = 80
+S1 = 29
+S2 = 15
+H1 = 2087563914
+H2 = 188817757
+H3 = 101784570
+H4 = 432174303
+
+[Peer]
+PublicKey = <PUBLIC_KEY_SERVER_A>
+AllowedIPs = 10.10.10.2/32
+```
+`ListenPort` - the port on which the server will wait for connections, you can choose any free one.\
+`<PRIVATE_KEY_SERVER_B>` - the content of the `private.key` file from Server **B**.\
+`<PUBLIC_KEY_SERVER_A>` - the content of the `public.key` file from Server **A**.
+
+Open the port on the firewall (if enabled):
+```bash
+sudo ufw allow from <PUBLIC_IP_SERVER_A> to any port 8443 proto udp
+```
+
+`<PUBLIC_IP_SERVER_A>` - the external IP address of Server **A**.
+
+#### Server A Configuration (Russian Federation):
+Create the interface configuration file (awg0)
+
+```bash
+nano /etc/amnezia/amneziawg/awg0.conf
+```
+
+File content
+```ini
+[Interface]
+Address = 10.10.10.2/24
+PrivateKey = <PRIVATE_KEY_SERVER_A>
+Jc = 4
+Jmin = 8
+Jmax = 80
+S1 = 29
+S2 = 15
+H1 = 2087563914
+H2 = 188817757
+H3 = 101784570
+H4 = 432174303
+I1 = <b 0xc10000000108981eba846e21f74e00>
+I2 = <b 0xc20000000108981eba846e21f74e00>
+I3 = <b 0xc30000000108981eba846e21f74e00>
+I4 = <b 0x43981eba846e21f74e>
+I5 = <b 0x43981eba846e21f74e>
+
+[Peer]
+PublicKey = <PUBLIC_KEY_SERVER_B>
+Endpoint = <PUBLIC_IP_SERVER_B>:8443
+AllowedIPs = 10.10.10.1/32
+PersistentKeepalive = 25
+```
+
+`<PRIVATE_KEY_SERVER_A>` - the content of the `private.key` file from Server **A**.\
+`<PUBLIC_KEY_SERVER_B>` - the content of the `public.key` file from Server **B**.\
+`<PUBLIC_IP_SERVER_B>` - the public IP address of Server **B**.
+
+Enable the tunnel on both servers:
+```bash
+sudo systemctl enable --now awg-quick@awg0
+```
+
+Make sure Server B is accessible from Server A through the tunnel.
+```bash
+ping 10.10.10.1
+PING 10.10.10.1 (10.10.10.1) 56(84) bytes of data.
+64 bytes from 10.10.10.1: icmp_seq=1 ttl=64 time=35.1 ms
+64 bytes from 10.10.10.1: icmp_seq=2 ttl=64 time=35.0 ms
+64 bytes from 10.10.10.1: icmp_seq=3 ttl=64 time=35.1 ms
+^C
+```
+---
+
+## Step 2. Installing telemt on Server B (conditionally Netherlands)
+Installation and configuration are described [here](https://github.com/telemt/telemt/blob/main/docs/QUICK_START_GUIDE.ru.md) or [here](https://gitlab.com/An0nX/telemt-docker#-quick-start-docker-compose).\
+It is assumed that telemt expects connections on port `443\tcp`.
+
+In the telemt config, you must enable the `Proxy` protocol and restrict connections to it only through the tunnel.
+```toml
+[server]
+port = 443
+listen_addr_ipv4 = "10.10.10.1"
+proxy_protocol = true
+```
+
+Also, for correct link generation, specify the FQDN or IP address and port of Server `A`
+```toml
+[general.links]
+show = "*"
+public_host = "<FQDN_OR_IP_SERVER_A>"
+public_port = 443
+```
+
+Open the port on the firewall (if enabled):
+```bash
+sudo ufw allow from 10.10.10.2 to any port 443 proto tcp
+```
+
+---
+
+## Step 3. Configuring HAProxy on Server A (Russian Federation)
+Since the version in the standard Ubuntu repository is relatively old, it makes sense to use the official Docker image.\
+[Instructions](https://docs.docker.com/engine/install/ubuntu/) for installing Docker on Ubuntu.
+
+> [!WARNING]
+> By default, regular users do not have rights to use ports < 1024.
+> Attempts to run HAProxy on port 443 can lead to errors:
+> ```
+> [ALERT] (8) : Binding [/usr/local/etc/haproxy/haproxy.cfg:17] for frontend tcp_in_443: 
+> protocol tcpv4: cannot bind socket (Permission denied) for [0.0.0.0:443].
+> ```
+> There are two simple ways to bypass this restriction, choose one:
+> 1. At the OS level, change the net.ipv4.ip_unprivileged_port_start setting to allow users to use all ports:
+> ```
+> echo "net.ipv4.ip_unprivileged_port_start = 0" | sudo tee -a /etc/sysctl.conf && sudo sysctl -p
+> ```
+> or
+> 
+> 2. Run HAProxy as root:
+> Uncomment the `user: "root"` parameter in docker-compose.yaml.
+
+#### Create a folder for HAProxy:
+```bash
+mkdir -p /opt/docker-compose/haproxy && cd $_
+```
+
+#### Create the docker-compose.yaml file
+`nano docker-compose.yaml`
+
+File content
+```yaml
+services:
+  haproxy:
+    image: haproxy:latest
+    container_name: haproxy
+    restart: unless-stopped
+    # user: "root"
+    network_mode: "host"
+    volumes:
+      - ./haproxy.cfg:/usr/local/etc/haproxy/haproxy.cfg:ro
+    logging:
+      driver: "json-file"
+      options:
+        max-size: "1m"
+        max-file: "1"
+```
+
+#### Create the haproxy.cfg config file
+Accept connections on port 443\tcp and send them through the tunnel to Server `B` 10.10.10.1:443
+
+`nano haproxy.cfg`
+
+File content
+
+```haproxy
+global
+    log stdout format raw local0
+    maxconn 10000
+
+defaults
+    log     global
+    mode    tcp
+    option  tcplog
+    option  clitcpka
+    option  srvtcpka
+    timeout connect 5s
+    timeout client  2h
+    timeout server  2h
+    timeout check   5s
+
+frontend tcp_in_443
+    bind *:443
+    maxconn 8000
+    option tcp-smart-accept
+    default_backend telemt_nodes
+
+backend telemt_nodes
+    option tcp-smart-connect
+    server server_a 10.10.10.1:443 check inter 5s rise 2 fall 3 send-proxy-v2
+
+
+```
+> [!WARNING]
+> **The file must end with an empty line, otherwise HAProxy will not start!**
+
+#### Allow port 443\tcp in the firewall (if enabled)
+```bash
+sudo ufw allow 443/tcp
+```
+
+#### Start the HAProxy container
+```bash
+docker compose up -d
+```
+
+If everything is configured correctly, you can now try connecting Telegram clients using links from the telemt log\api.

docs/VPS_DOUBLE_HOP.ru.md

@@ -0,0 +1,287 @@
+<img src="https://gist.githubusercontent.com/avbor/1f8a128e628f47249aae6e058a57610b/raw/19013276c035e91058e0a9799ab145f8e70e3ff5/scheme.svg">
+
+## Концепция
+- **Сервер A** (_РФ_):\
+  Точка входа, принимает трафик пользователей Telegram-прокси через **HAProxy** (порт `443`)\
+  и отправляет в туннель на Сервер **B**.\
+  Внутренний IP в туннеле — `10.10.10.2`\
+  Порт для клиентов HAProxy — `443\tcp`
+- **Сервер B** (_условно Нидерланды_):\
+  Точка выхода, на нем работает **telemt** и принимает подключения клиентов через Сервер **A**.\
+  На сервере должен быть неограниченный доступ до серверов Telegram.\
+  Внутренний IP в туннеле — `10.10.10.1`\
+  Порт AmneziaWG — `8443\udp`\
+  Порт для клиентов telemt — `443\tcp`
+
+---
+
+## Шаг 1. Настройка туннеля AmneziaWG (A <-> B)
+
+На всех серверах необходимо установить [amneziawg](https://github.com/amnezia-vpn/amneziawg-linux-kernel-module).\
+Далее все команды даны для **Ununtu 24.04**.\
+Для RHEL-based дистрибутивов инструкция по установке есть по ссылке выше.
+
+### Установка AmneziaWG (Сервера A и B)
+На каждом из серверов необходимо выполнить следующие шаги:
+
+#### 1. Добавление репозитория AmneziaWG и установка необходимых пакетов:
+```bash
+sudo apt install -y software-properties-common python3-launchpadlib gnupg2 linux-headers-$(uname -r) && \
+sudo add-apt-repository ppa:amnezia/ppa && \
+sudo apt-get install -y amneziawg
+```
+ 
+#### 2. Генерация уникальной пары ключей:
+```bash
+cd /etc/amnezia/amneziawg && \
+awg genkey | tee private.key | awg pubkey > public.key
+```
+В результате вы получите в папке `/etc/amnezia/amneziawg` два файла:\
+`private.key` - приватный и\
+`public.key` - публичный ключи сервера
+
+#### 3. Настройка сетевых интерфейсов:
+
+Параметры обфускации `S1`, `S2`, `H1`, `H2`, `H3`, `H4` должны быть строго идентичными на обоих серверах.\
+Параметры `Jc`, `Jmin` и `Jmax` могут отличатся.\
+Параметры `I1-I5` [(Custom Protocol Signature)](https://docs.amnezia.org/documentation/amnezia-wg/) нужно указывать на стороне _клиента_ (Сервер **А**).
+
+Рекомендации по выбору значений:
+```text
+Jc — 1 ≤ Jc ≤ 128; от 4 до 12 включительно
+Jmin — Jmax > Jmin < 1280*; рекомендовано 8
+Jmax — Jmin < Jmax ≤ 1280*; рекомендовано 80
+S1 — S1 ≤ 1132* (1280* - 148 = 1132); S1 + 56 ≠ S2;
+рекомендованный диапазон от 15 до 150 включительно
+S2 — S2 ≤ 1188* (1280* - 92 = 1188);
+рекомендованный диапазон от 15 до 150 включительно
+H1/H2/H3/H4 — должны быть уникальны и отличаться друг от друга;
+рекомендованный диапазон от 5 до 2147483647 включительно
+
+* Предполагается, что подключение к Интернету имеет MTU 1280.
+```
+> [!IMPORTANT]
+> Рекомендуется использовать собственные, уникальные значения.\
+> Для выбора параметров можете воспользоваться [генератором](https://htmlpreview.github.io/?https://gist.githubusercontent.com/avbor/955782b5c37b06240b243aa375baeac5/raw/e8b269ff0089a27effd88f8d925179b78e5666c4/awg-gen.html).
+
+#### Конфигурация Сервера B (_Нидерланды_):
+
+Создаем файл конфигурации интерфейса (`awg0`)
+```bash
+nano /etc/amnezia/amneziawg/awg0.conf
+```
+
+Содержимое файла
+```ini
+[Interface]
+Address = 10.10.10.1/24
+ListenPort = 8443
+PrivateKey = <PRIVATE_KEY_SERVER_B>
+SaveConfig = true
+Jc = 4
+Jmin = 8
+Jmax = 80
+S1 = 29
+S2 = 15
+H1 = 2087563914
+H2 = 188817757
+H3 = 101784570
+H4 = 432174303
+
+[Peer]
+PublicKey = <PUBLIC_KEY_SERVER_A>
+AllowedIPs = 10.10.10.2/32
+```
+
+`ListenPort` - порт, на котором сервер будет ждать подключения, можете выбрать любой свободный.\
+`<PRIVATE_KEY_SERVER_B>` - содержимое файла `private.key` с сервера **B**.\
+`<PUBLIC_KEY_SERVER_A>` - содержимое файла `public.key` с сервера **A**.
+
+Открываем порт на фаерволе (если включен):
+```bash
+sudo ufw allow from <PUBLIC_IP_SERVER_A> to any port 8443 proto udp
+```
+
+`<PUBLIC_IP_SERVER_A>` - внешний IP адрес Сервера **A**.
+
+#### Конфигурация Сервера A (_РФ_):
+
+Создаем файл конфигурации интерфейса (`awg0`)
+```bash
+nano /etc/amnezia/amneziawg/awg0.conf
+```
+
+Содержимое файла
+```ini
+[Interface]
+Address = 10.10.10.2/24
+PrivateKey = <PRIVATE_KEY_SERVER_A>
+Jc = 4
+Jmin = 8
+Jmax = 80
+S1 = 29
+S2 = 15
+H1 = 2087563914
+H2 = 188817757
+H3 = 101784570
+H4 = 432174303
+I1 = <b 0xc10000000108981eba846e21f74e00>
+I2 = <b 0xc20000000108981eba846e21f74e00>
+I3 = <b 0xc30000000108981eba846e21f74e00>
+I4 = <b 0x43981eba846e21f74e>
+I5 = <b 0x43981eba846e21f74e>
+
+[Peer]
+PublicKey = <PUBLIC_KEY_SERVER_B>
+Endpoint = <PUBLIC_IP_SERVER_B>:8443
+AllowedIPs = 10.10.10.1/32
+PersistentKeepalive = 25
+```
+
+`<PRIVATE_KEY_SERVER_A>` - содержимое файла `private.key` с сервера **A**.\
+`<PUBLIC_KEY_SERVER_B>` - содержимое файла `public.key` с сервера **B**.\
+`<PUBLIC_IP_SERVER_B>` - публичный IP адресс сервера **B**.
+
+#### Включаем туннель на обоих серверах:
+```bash
+sudo systemctl enable --now awg-quick@awg0 
+```
+
+Убедитесь, что с Сервера `A` доступен Сервер `B` через туннель.
+```bash
+ping 10.10.10.1
+PING 10.10.10.1 (10.10.10.1) 56(84) bytes of data.
+64 bytes from 10.10.10.1: icmp_seq=1 ttl=64 time=35.1 ms
+64 bytes from 10.10.10.1: icmp_seq=2 ttl=64 time=35.0 ms
+64 bytes from 10.10.10.1: icmp_seq=3 ttl=64 time=35.1 ms
+^C
+
+```
+
+---
+
+## Шаг 2. Установка telemt на Сервере B (_условно Нидерланды_)
+
+Установка и настройка описаны [здесь](https://github.com/telemt/telemt/blob/main/docs/QUICK_START_GUIDE.ru.md) или [здесь](https://gitlab.com/An0nX/telemt-docker#-quick-start-docker-compose).\
+Подразумевается что telemt ожидает подключения на порту `443\tcp`.
+
+В конфиге telemt необходимо включить протокол `Proxy` и ограничить подключения к нему только через туннель.
+
+```toml
+[server]
+port = 443
+listen_addr_ipv4 = "10.10.10.1"
+proxy_protocol = true
+```
+
+А также, для правильной генерации ссылок, указать FQDN или IP адрес и порт Сервера `A` 
+
+```toml
+[general.links]
+show = "*"
+public_host = "<FQDN_OR_IP_SERVER_A>"
+public_port = 443
+```
+
+Открываем порт на фаерволе (если включен):
+```bash
+sudo ufw allow from 10.10.10.2 to any port 443 proto tcp
+```
+
+---
+
+### Шаг 3. Настройка HAProxy на Сервере A (_РФ_)
+
+Т.к. в стандартном репозитории Ubuntu версия относительно старая, имеет смысл воспользоваться официальным образом Docker.\
+[Инструкция](https://docs.docker.com/engine/install/ubuntu/) по установке Docker на Ubuntu.
+
+> [!WARNING]
+> По умолчанию у обычных пользователей нет прав на использование портов < 1024.\
+> Попытки запустить HAProxy на 443 порту могут приводить к ошибкам:
+> ```
+> [ALERT] (8) : Binding [/usr/local/etc/haproxy/haproxy.cfg:17] for frontend tcp_in_443: 
+> protocol tcpv4: cannot bind socket (Permission denied) for [0.0.0.0:443].
+> ```
+> Есть два простых способа обойти это ограничение, выберите что-то одно:
+> 1. На уровне ОС изменить настройку net.ipv4.ip_unprivileged_port_start, разрешив пользователям использовать все порты:
+> ```
+> echo "net.ipv4.ip_unprivileged_port_start = 0" | sudo tee -a /etc/sysctl.conf && sudo sysctl -p
+> ```
+> или
+> 
+> 2. Запустить HAProxy под root:\
+> Раскомментируйте в docker-compose.yaml параметр `user: "root"`.
+
+#### Создаем папку для HAProxy:
+```bash
+mkdir -p /opt/docker-compose/haproxy && cd $_
+```
+#### Создаем файл docker-compose.yaml
+
+`nano docker-compose.yaml`
+
+Содержимое файла
+```yaml
+services:
+  haproxy:
+    image: haproxy:latest
+    container_name: haproxy
+    restart: unless-stopped
+    # user: "root"
+    network_mode: "host"
+    volumes:
+      - ./haproxy.cfg:/usr/local/etc/haproxy/haproxy.cfg:ro
+    logging:
+      driver: "json-file"
+      options:
+        max-size: "1m"
+        max-file: "1"
+```
+#### Создаем файл конфига haproxy.cfg
+Принимаем подключения на порту 443\tcp и отправляем их через туннель на Сервер `B` 10.10.10.1:443
+
+`nano haproxy.cfg`
+
+Содержимое файла
+```haproxy
+global
+    log stdout format raw local0
+    maxconn 10000
+
+defaults
+    log     global
+    mode    tcp
+    option  tcplog
+    option  clitcpka
+    option  srvtcpka
+    timeout connect 5s
+    timeout client  2h
+    timeout server  2h
+    timeout check   5s
+
+frontend tcp_in_443
+    bind *:443
+    maxconn 8000
+    option tcp-smart-accept
+    default_backend telemt_nodes
+
+backend telemt_nodes
+    option tcp-smart-connect
+    server server_a 10.10.10.1:443 check inter 5s rise 2 fall 3 send-proxy-v2
+
+
+```
+>[!WARNING]
+>**Файл должен заканчиваться пустой строкой, иначе HAProxy не запуститься!**
+
+#### Разрешаем порт 443\tcp в фаерволе (если включен)
+```bash
+sudo ufw allow 443/tcp
+```
+
+#### Запускаем контейнер HAProxy
+```bash
+docker compose up -d
+```
+
+Если все настроено верно, то теперь можно пробовать подключить клиентов Telegram с использованием ссылок из лога\api telemt.

src/config/defaults.rs

@@ -553,6 +553,20 @@ pub(crate) fn default_mask_shape_above_cap_blur_max_bytes() -> usize {
     512
 }
 
+#[cfg(not(test))]
+pub(crate) fn default_mask_relay_max_bytes() -> usize {
+    5 * 1024 * 1024
+}
+
+#[cfg(test)]
+pub(crate) fn default_mask_relay_max_bytes() -> usize {
+    32 * 1024
+}
+
+pub(crate) fn default_mask_classifier_prefetch_timeout_ms() -> u64 {
+    5
+}
+
 pub(crate) fn default_mask_timing_normalization_enabled() -> bool {
     false
 }

src/config/hot_reload.rs

@@ -600,6 +600,9 @@ fn warn_non_hot_changes(old: &ProxyConfig, new: &ProxyConfig, non_hot_changed: b
         || old.censorship.mask_shape_above_cap_blur != new.censorship.mask_shape_above_cap_blur
         || old.censorship.mask_shape_above_cap_blur_max_bytes
             != new.censorship.mask_shape_above_cap_blur_max_bytes
+        || old.censorship.mask_relay_max_bytes != new.censorship.mask_relay_max_bytes
+        || old.censorship.mask_classifier_prefetch_timeout_ms
+            != new.censorship.mask_classifier_prefetch_timeout_ms
         || old.censorship.mask_timing_normalization_enabled
             != new.censorship.mask_timing_normalization_enabled
         || old.censorship.mask_timing_normalization_floor_ms

src/config/load.rs

@@ -430,6 +430,25 @@ impl ProxyConfig {
             ));
         }
 
+        if config.censorship.mask_relay_max_bytes == 0 {
+            return Err(ProxyError::Config(
+                "censorship.mask_relay_max_bytes must be > 0".to_string(),
+            ));
+        }
+
+        if config.censorship.mask_relay_max_bytes > 67_108_864 {
+            return Err(ProxyError::Config(
+                "censorship.mask_relay_max_bytes must be <= 67108864".to_string(),
+            ));
+        }
+
+        if !(5..=50).contains(&config.censorship.mask_classifier_prefetch_timeout_ms) {
+            return Err(ProxyError::Config(
+                "censorship.mask_classifier_prefetch_timeout_ms must be within [5, 50]"
+                    .to_string(),
+            ));
+        }
+
         if config.censorship.mask_timing_normalization_ceiling_ms
             < config.censorship.mask_timing_normalization_floor_ms
         {
@@ -1134,6 +1153,10 @@ mod load_security_tests;
 #[path = "tests/load_mask_shape_security_tests.rs"]
 mod load_mask_shape_security_tests;
 
+#[cfg(test)]
+#[path = "tests/load_mask_classifier_prefetch_timeout_security_tests.rs"]
+mod load_mask_classifier_prefetch_timeout_security_tests;
+
 #[cfg(test)]
 mod tests {
     use super::*;

src/config/tests/load_mask_classifier_prefetch_timeout_security_tests.rs

@@ -0,0 +1,75 @@
+use super::*;
+use std::fs;
+use std::path::PathBuf;
+use std::time::{SystemTime, UNIX_EPOCH};
+
+fn write_temp_config(contents: &str) -> PathBuf {
+    let nonce = SystemTime::now()
+        .duration_since(UNIX_EPOCH)
+        .expect("system time must be after unix epoch")
+        .as_nanos();
+    let path = std::env::temp_dir()
+        .join(format!("telemt-load-mask-prefetch-timeout-security-{nonce}.toml"));
+    fs::write(&path, contents).expect("temp config write must succeed");
+    path
+}
+
+fn remove_temp_config(path: &PathBuf) {
+    let _ = fs::remove_file(path);
+}
+
+#[test]
+fn load_rejects_mask_classifier_prefetch_timeout_below_min_bound() {
+    let path = write_temp_config(
+        r#"
+[censorship]
+mask_classifier_prefetch_timeout_ms = 4
+"#,
+    );
+
+    let err = ProxyConfig::load(&path)
+        .expect_err("prefetch timeout below minimum security bound must be rejected");
+    let msg = err.to_string();
+    assert!(
+        msg.contains("censorship.mask_classifier_prefetch_timeout_ms must be within [5, 50]"),
+        "error must explain timeout bound invariant, got: {msg}"
+    );
+
+    remove_temp_config(&path);
+}
+
+#[test]
+fn load_rejects_mask_classifier_prefetch_timeout_above_max_bound() {
+    let path = write_temp_config(
+        r#"
+[censorship]
+mask_classifier_prefetch_timeout_ms = 51
+"#,
+    );
+
+    let err = ProxyConfig::load(&path)
+        .expect_err("prefetch timeout above max security bound must be rejected");
+    let msg = err.to_string();
+    assert!(
+        msg.contains("censorship.mask_classifier_prefetch_timeout_ms must be within [5, 50]"),
+        "error must explain timeout bound invariant, got: {msg}"
+    );
+
+    remove_temp_config(&path);
+}
+
+#[test]
+fn load_accepts_mask_classifier_prefetch_timeout_within_bounds() {
+    let path = write_temp_config(
+        r#"
+[censorship]
+mask_classifier_prefetch_timeout_ms = 20
+"#,
+    );
+
+    let cfg = ProxyConfig::load(&path)
+        .expect("prefetch timeout within security bounds must be accepted");
+    assert_eq!(cfg.censorship.mask_classifier_prefetch_timeout_ms, 20);
+
+    remove_temp_config(&path);
+}

src/config/tests/load_mask_shape_security_tests.rs

@@ -236,3 +236,57 @@ mask_shape_above_cap_blur_max_bytes = 8
 
     remove_temp_config(&path);
 }
+
+#[test]
+fn load_rejects_zero_mask_relay_max_bytes() {
+    let path = write_temp_config(
+        r#"
+[censorship]
+mask_relay_max_bytes = 0
+"#,
+    );
+
+    let err = ProxyConfig::load(&path).expect_err("mask_relay_max_bytes must be > 0");
+    let msg = err.to_string();
+    assert!(
+        msg.contains("censorship.mask_relay_max_bytes must be > 0"),
+        "error must explain non-zero relay cap invariant, got: {msg}"
+    );
+
+    remove_temp_config(&path);
+}
+
+#[test]
+fn load_rejects_mask_relay_max_bytes_above_upper_bound() {
+    let path = write_temp_config(
+        r#"
+[censorship]
+mask_relay_max_bytes = 67108865
+"#,
+    );
+
+    let err = ProxyConfig::load(&path)
+        .expect_err("mask_relay_max_bytes above hard cap must be rejected");
+    let msg = err.to_string();
+    assert!(
+        msg.contains("censorship.mask_relay_max_bytes must be <= 67108864"),
+        "error must explain relay cap upper bound invariant, got: {msg}"
+    );
+
+    remove_temp_config(&path);
+}
+
+#[test]
+fn load_accepts_valid_mask_relay_max_bytes() {
+    let path = write_temp_config(
+        r#"
+[censorship]
+mask_relay_max_bytes = 8388608
+"#,
+    );
+
+    let cfg = ProxyConfig::load(&path).expect("valid mask_relay_max_bytes must be accepted");
+    assert_eq!(cfg.censorship.mask_relay_max_bytes, 8_388_608);
+
+    remove_temp_config(&path);
+}

src/config/types.rs

@@ -1450,6 +1450,14 @@ pub struct AntiCensorshipConfig {
     #[serde(default = "default_mask_shape_above_cap_blur_max_bytes")]
     pub mask_shape_above_cap_blur_max_bytes: usize,
 
+    /// Maximum bytes relayed per direction on unauthenticated masking fallback paths.
+    #[serde(default = "default_mask_relay_max_bytes")]
+    pub mask_relay_max_bytes: usize,
+
+    /// Prefetch timeout (ms) for extending fragmented masking classifier window.
+    #[serde(default = "default_mask_classifier_prefetch_timeout_ms")]
+    pub mask_classifier_prefetch_timeout_ms: u64,
+
     /// Enable outcome-time normalization envelope for masking fallback.
     #[serde(default = "default_mask_timing_normalization_enabled")]
     pub mask_timing_normalization_enabled: bool,
@@ -1488,6 +1496,8 @@ impl Default for AntiCensorshipConfig {
             mask_shape_bucket_cap_bytes: default_mask_shape_bucket_cap_bytes(),
             mask_shape_above_cap_blur: default_mask_shape_above_cap_blur(),
             mask_shape_above_cap_blur_max_bytes: default_mask_shape_above_cap_blur_max_bytes(),
+            mask_relay_max_bytes: default_mask_relay_max_bytes(),
+            mask_classifier_prefetch_timeout_ms: default_mask_classifier_prefetch_timeout_ms(),
             mask_timing_normalization_enabled: default_mask_timing_normalization_enabled(),
             mask_timing_normalization_floor_ms: default_mask_timing_normalization_floor_ms(),
             mask_timing_normalization_ceiling_ms: default_mask_timing_normalization_ceiling_ms(),

src/proxy/client.rs

@@ -186,6 +186,67 @@ fn handshake_timeout_with_mask_grace(config: &ProxyConfig) -> Duration {
     }
 }
 
+const MASK_CLASSIFIER_PREFETCH_WINDOW: usize = 16;
+#[cfg(test)]
+const MASK_CLASSIFIER_PREFETCH_TIMEOUT: Duration = Duration::from_millis(5);
+
+fn mask_classifier_prefetch_timeout(config: &ProxyConfig) -> Duration {
+    Duration::from_millis(config.censorship.mask_classifier_prefetch_timeout_ms)
+}
+
+fn should_prefetch_mask_classifier_window(initial_data: &[u8]) -> bool {
+    if initial_data.len() >= MASK_CLASSIFIER_PREFETCH_WINDOW {
+        return false;
+    }
+
+    if initial_data.is_empty() {
+        // Empty initial_data means there is no client probe prefix to refine.
+        // Prefetching in this case can consume fallback relay payload bytes and
+        // accidentally route them through shaping heuristics.
+        return false;
+    }
+
+    if initial_data[0] == 0x16 || initial_data.starts_with(b"SSH-") {
+        return false;
+    }
+
+    initial_data.iter().all(|b| b.is_ascii_alphabetic() || *b == b' ')
+}
+
+#[cfg(test)]
+async fn extend_masking_initial_window<R>(reader: &mut R, initial_data: &mut Vec<u8>)
+where
+    R: AsyncRead + Unpin,
+{
+    extend_masking_initial_window_with_timeout(reader, initial_data, MASK_CLASSIFIER_PREFETCH_TIMEOUT)
+        .await;
+}
+
+async fn extend_masking_initial_window_with_timeout<R>(
+    reader: &mut R,
+    initial_data: &mut Vec<u8>,
+    prefetch_timeout: Duration,
+)
+where
+    R: AsyncRead + Unpin,
+{
+    if !should_prefetch_mask_classifier_window(initial_data) {
+        return;
+    }
+
+    let need = MASK_CLASSIFIER_PREFETCH_WINDOW.saturating_sub(initial_data.len());
+    if need == 0 {
+        return;
+    }
+
+    let mut extra = [0u8; MASK_CLASSIFIER_PREFETCH_WINDOW];
+    if let Ok(Ok(n)) = timeout(prefetch_timeout, reader.read(&mut extra[..need])).await
+        && n > 0
+    {
+        initial_data.extend_from_slice(&extra[..n]);
+    }
+}
+
 fn masking_outcome<R, W>(
     reader: R,
     writer: W,
@@ -200,6 +261,15 @@ where
     W: AsyncWrite + Unpin + Send + 'static,
 {
     HandshakeOutcome::NeedsMasking(Box::pin(async move {
+        let mut reader = reader;
+        let mut initial_data = initial_data;
+        extend_masking_initial_window_with_timeout(
+            &mut reader,
+            &mut initial_data,
+            mask_classifier_prefetch_timeout(&config),
+        )
+        .await;
+
         handle_bad_client(
             reader,
             writer,
@@ -1153,7 +1223,7 @@ impl RunningClientHandler {
         }
 
         if let Some(quota) = config.access.user_data_quota.get(user)
-            && stats.get_user_total_octets(user) >= *quota
+            && stats.get_user_quota_used(user) >= *quota
         {
             return Err(ProxyError::DataQuotaExceeded {
                 user: user.to_string(),
@@ -1212,7 +1282,7 @@ impl RunningClientHandler {
         }
 
         if let Some(quota) = config.access.user_data_quota.get(user)
-            && stats.get_user_total_octets(user) >= *quota
+            && stats.get_user_quota_used(user) >= *quota
         {
             return Err(ProxyError::DataQuotaExceeded {
                 user: user.to_string(),
@@ -1321,6 +1391,38 @@ mod masking_shape_classifier_fuzz_redteam_expected_fail_tests;
 #[path = "tests/client_masking_probe_evasion_blackhat_tests.rs"]
 mod masking_probe_evasion_blackhat_tests;
 
+#[cfg(test)]
+#[path = "tests/client_masking_fragmented_classifier_security_tests.rs"]
+mod masking_fragmented_classifier_security_tests;
+
+#[cfg(test)]
+#[path = "tests/client_masking_replay_timing_security_tests.rs"]
+mod masking_replay_timing_security_tests;
+
+#[cfg(test)]
+#[path = "tests/client_masking_http2_fragmented_preface_security_tests.rs"]
+mod masking_http2_fragmented_preface_security_tests;
+
+#[cfg(test)]
+#[path = "tests/client_masking_prefetch_invariant_security_tests.rs"]
+mod masking_prefetch_invariant_security_tests;
+
+#[cfg(test)]
+#[path = "tests/client_masking_prefetch_timing_matrix_security_tests.rs"]
+mod masking_prefetch_timing_matrix_security_tests;
+
+#[cfg(test)]
+#[path = "tests/client_masking_prefetch_config_runtime_security_tests.rs"]
+mod masking_prefetch_config_runtime_security_tests;
+
+#[cfg(test)]
+#[path = "tests/client_masking_prefetch_config_pipeline_integration_security_tests.rs"]
+mod masking_prefetch_config_pipeline_integration_security_tests;
+
+#[cfg(test)]
+#[path = "tests/client_masking_prefetch_strict_boundary_security_tests.rs"]
+mod masking_prefetch_strict_boundary_security_tests;
+
 #[cfg(test)]
 #[path = "tests/client_beobachten_ttl_bounds_security_tests.rs"]
 mod beobachten_ttl_bounds_security_tests;
@@ -1328,3 +1430,15 @@ mod beobachten_ttl_bounds_security_tests;
 #[cfg(test)]
 #[path = "tests/client_tls_record_wrap_hardening_security_tests.rs"]
 mod tls_record_wrap_hardening_security_tests;
+
+#[cfg(test)]
+#[path = "tests/client_clever_advanced_tests.rs"]
+mod client_clever_advanced_tests;
+
+#[cfg(test)]
+#[path = "tests/client_more_advanced_tests.rs"]
+mod client_more_advanced_tests;
+
+#[cfg(test)]
+#[path = "tests/client_deep_invariants_tests.rs"]
+mod client_deep_invariants_tests;

src/proxy/handshake.rs

@@ -121,6 +121,19 @@ fn auth_probe_eviction_offset(peer_ip: IpAddr, now: Instant) -> usize {
     hasher.finish() as usize
 }
 
+fn auth_probe_scan_start_offset(
+    peer_ip: IpAddr,
+    now: Instant,
+    state_len: usize,
+    scan_limit: usize,
+) -> usize {
+    if state_len == 0 || scan_limit == 0 {
+        return 0;
+    }
+
+    auth_probe_eviction_offset(peer_ip, now) % state_len
+}
+
 fn auth_probe_is_throttled(peer_ip: IpAddr, now: Instant) -> bool {
     let peer_ip = normalize_auth_probe_ip(peer_ip);
     let state = auth_probe_state_map();
@@ -269,11 +282,7 @@ fn auth_probe_record_failure_with_state(
             let mut eviction_candidate: Option<(IpAddr, u32, Instant)> = None;
             let state_len = state.len();
             let scan_limit = state_len.min(AUTH_PROBE_PRUNE_SCAN_LIMIT);
-            let start_offset = if state_len == 0 {
-                0
-            } else {
-                auth_probe_eviction_offset(peer_ip, now) % state_len
-            };
+            let start_offset = auth_probe_scan_start_offset(peer_ip, now, state_len, scan_limit);
 
             let mut scanned = 0usize;
             for entry in state.iter().skip(start_offset) {
@@ -605,10 +614,9 @@ where
         }
     };
 
-    // Replay tracking is applied only after successful authentication to avoid
-    // letting unauthenticated probes evict valid entries from the replay cache.
+    // Reject known replay digests before expensive cache/domain/ALPN policy work.
     let digest_half = &validation.digest[..tls::TLS_DIGEST_HALF_LEN];
-    if replay_checker.check_and_add_tls_digest(digest_half) {
+    if replay_checker.check_tls_digest(digest_half) {
         auth_probe_record_failure(peer.ip(), Instant::now());
         maybe_apply_server_hello_delay(config).await;
         warn!(peer = %peer, "TLS replay attack detected (duplicate digest)");
@@ -670,6 +678,9 @@ where
         None
     };
 
+    // Add replay digest only for policy-valid handshakes.
+    replay_checker.add_tls_digest(digest_half);
+
     let response = if let Some((cached_entry, use_full_cert_payload)) = cached {
         emulator::build_emulated_server_hello(
             secret,
@@ -769,7 +780,7 @@ where
         let mut dec_key_input = Zeroizing::new(Vec::with_capacity(PREKEY_LEN + secret.len()));
         dec_key_input.extend_from_slice(dec_prekey);
         dec_key_input.extend_from_slice(&secret);
-        let dec_key = sha256(&dec_key_input);
+        let dec_key = Zeroizing::new(sha256(&dec_key_input));
 
         let mut dec_iv_arr = [0u8; IV_LEN];
         dec_iv_arr.copy_from_slice(dec_iv_bytes);
@@ -805,7 +816,7 @@ where
         let mut enc_key_input = Zeroizing::new(Vec::with_capacity(PREKEY_LEN + secret.len()));
         enc_key_input.extend_from_slice(enc_prekey);
         enc_key_input.extend_from_slice(&secret);
-        let enc_key = sha256(&enc_key_input);
+        let enc_key = Zeroizing::new(sha256(&enc_key_input));
 
         let mut enc_iv_arr = [0u8; IV_LEN];
         enc_iv_arr.copy_from_slice(enc_iv_bytes);
@@ -830,9 +841,9 @@ where
             user: user.clone(),
             dc_idx,
             proto_tag,
-            dec_key,
+            dec_key: *dec_key,
             dec_iv,
-            enc_key,
+            enc_key: *enc_key,
             enc_iv,
             peer,
             is_tls,
@@ -979,6 +990,38 @@ mod saturation_poison_security_tests;
 #[path = "tests/handshake_auth_probe_hardening_adversarial_tests.rs"]
 mod auth_probe_hardening_adversarial_tests;
 
+#[cfg(test)]
+#[path = "tests/handshake_auth_probe_scan_budget_security_tests.rs"]
+mod auth_probe_scan_budget_security_tests;
+
+#[cfg(test)]
+#[path = "tests/handshake_auth_probe_scan_offset_stress_tests.rs"]
+mod auth_probe_scan_offset_stress_tests;
+
+#[cfg(test)]
+#[path = "tests/handshake_auth_probe_eviction_bias_security_tests.rs"]
+mod auth_probe_eviction_bias_security_tests;
+
+#[cfg(test)]
+#[path = "tests/handshake_advanced_clever_tests.rs"]
+mod advanced_clever_tests;
+
+#[cfg(test)]
+#[path = "tests/handshake_more_clever_tests.rs"]
+mod more_clever_tests;
+
+#[cfg(test)]
+#[path = "tests/handshake_real_bug_stress_tests.rs"]
+mod real_bug_stress_tests;
+
+#[cfg(test)]
+#[path = "tests/handshake_timing_manual_bench_tests.rs"]
+mod timing_manual_bench_tests;
+
+#[cfg(test)]
+#[path = "tests/handshake_key_material_zeroization_security_tests.rs"]
+mod handshake_key_material_zeroization_security_tests;
+
 /// Compile-time guard: HandshakeSuccess holds cryptographic key material and
 /// must never be Copy.  A Copy impl would allow silent key duplication,
 /// undermining the zeroize-on-drop guarantee.

src/proxy/masking.rs

@@ -4,14 +4,23 @@ use crate::config::ProxyConfig;
 use crate::network::dns_overrides::resolve_socket_addr;
 use crate::stats::beobachten::BeobachtenStore;
 use crate::transport::proxy_protocol::{ProxyProtocolV1Builder, ProxyProtocolV2Builder};
-use rand::{Rng, RngExt};
-use std::net::SocketAddr;
+#[cfg(unix)]
+use nix::ifaddrs::getifaddrs;
+use rand::rngs::StdRng;
+use rand::{Rng, RngExt, SeedableRng};
+use std::net::{IpAddr, SocketAddr};
 use std::str;
-use std::time::Duration;
+#[cfg(unix)]
+use std::sync::{Mutex, OnceLock};
+#[cfg(test)]
+use std::sync::atomic::{AtomicUsize, Ordering};
+use std::time::{Duration, Instant as StdInstant};
 use tokio::io::{AsyncRead, AsyncReadExt, AsyncWrite, AsyncWriteExt};
 use tokio::net::TcpStream;
 #[cfg(unix)]
 use tokio::net::UnixStream;
+#[cfg(unix)]
+use tokio::sync::Mutex as AsyncMutex;
 use tokio::time::{Instant, timeout};
 use tracing::debug;
 
@@ -30,28 +39,55 @@ const MASK_RELAY_IDLE_TIMEOUT: Duration = Duration::from_secs(5);
 #[cfg(test)]
 const MASK_RELAY_IDLE_TIMEOUT: Duration = Duration::from_millis(100);
 const MASK_BUFFER_SIZE: usize = 8192;
+#[cfg(unix)]
+#[cfg(not(test))]
+const LOCAL_INTERFACE_CACHE_TTL: Duration = Duration::from_secs(300);
+#[cfg(all(unix, test))]
+const LOCAL_INTERFACE_CACHE_TTL: Duration = Duration::from_secs(1);
 
 struct CopyOutcome {
     total: usize,
     ended_by_eof: bool,
 }
 
-async fn copy_with_idle_timeout<R, W>(reader: &mut R, writer: &mut W) -> CopyOutcome
+async fn copy_with_idle_timeout<R, W>(
+    reader: &mut R,
+    writer: &mut W,
+    byte_cap: usize,
+    shutdown_on_eof: bool,
+) -> CopyOutcome
 where
     R: AsyncRead + Unpin,
     W: AsyncWrite + Unpin,
 {
-    let mut buf = [0u8; MASK_BUFFER_SIZE];
+    let mut buf = Box::new([0u8; MASK_BUFFER_SIZE]);
     let mut total = 0usize;
     let mut ended_by_eof = false;
+
+    if byte_cap == 0 {
+        return CopyOutcome {
+            total,
+            ended_by_eof,
+        };
+    }
+
     loop {
-        let read_res = timeout(MASK_RELAY_IDLE_TIMEOUT, reader.read(&mut buf)).await;
+        let remaining_budget = byte_cap.saturating_sub(total);
+        if remaining_budget == 0 {
+            break;
+        }
+
+        let read_len = remaining_budget.min(MASK_BUFFER_SIZE);
+        let read_res = timeout(MASK_RELAY_IDLE_TIMEOUT, reader.read(&mut buf[..read_len])).await;
         let n = match read_res {
             Ok(Ok(n)) => n,
             Ok(Err(_)) | Err(_) => break,
         };
         if n == 0 {
             ended_by_eof = true;
+            if shutdown_on_eof {
+                let _ = timeout(MASK_RELAY_IDLE_TIMEOUT, writer.shutdown()).await;
+            }
             break;
         }
         total = total.saturating_add(n);
@@ -68,6 +104,39 @@ where
     }
 }
 
+fn is_http_probe(data: &[u8]) -> bool {
+    // RFC 7540 section 3.5: HTTP/2 client preface starts with "PRI ".
+    const HTTP_METHODS: [&[u8]; 10] = [
+        b"GET ",
+        b"POST",
+        b"HEAD",
+        b"PUT ",
+        b"DELETE",
+        b"OPTIONS",
+        b"CONNECT",
+        b"TRACE",
+        b"PATCH",
+        b"PRI ",
+    ];
+
+    if data.is_empty() {
+        return false;
+    }
+
+    let window = &data[..data.len().min(16)];
+    for method in HTTP_METHODS {
+        if data.len() >= method.len() && window.starts_with(method) {
+            return true;
+        }
+
+        if (2..=3).contains(&window.len()) && method.starts_with(window) {
+            return true;
+        }
+    }
+
+    false
+}
+
 fn next_mask_shape_bucket(total: usize, floor: usize, cap: usize) -> usize {
     if total == 0 || floor == 0 || cap < floor {
         return total;
@@ -125,6 +194,11 @@ async fn maybe_write_shape_padding<W>(
     let mut remaining = target_total - total_sent;
     let mut pad_chunk = [0u8; 1024];
     let deadline = Instant::now() + MASK_TIMEOUT;
+    // Use a Send RNG so relay futures remain spawn-safe under Tokio.
+    let mut rng = {
+        let mut seed_source = rand::rng();
+        StdRng::from_rng(&mut seed_source)
+    };
 
     while remaining > 0 {
         let now = Instant::now();
@@ -133,10 +207,7 @@ async fn maybe_write_shape_padding<W>(
         }
 
         let write_len = remaining.min(pad_chunk.len());
-        {
-            let mut rng = rand::rng();
-            rng.fill_bytes(&mut pad_chunk[..write_len]);
-        }
+        rng.fill_bytes(&mut pad_chunk[..write_len]);
         let write_budget = deadline.saturating_duration_since(now);
         match timeout(write_budget, mask_write.write_all(&pad_chunk[..write_len])).await {
             Ok(Ok(())) => {}
@@ -167,11 +238,11 @@ where
     }
 }
 
-async fn consume_client_data_with_timeout<R>(reader: R)
+async fn consume_client_data_with_timeout_and_cap<R>(reader: R, byte_cap: usize)
 where
     R: AsyncRead + Unpin,
 {
-    if timeout(MASK_RELAY_TIMEOUT, consume_client_data(reader))
+    if timeout(MASK_RELAY_TIMEOUT, consume_client_data(reader, byte_cap))
         .await
         .is_err()
     {
@@ -190,6 +261,13 @@ fn mask_outcome_target_budget(config: &ProxyConfig) -> Duration {
     if config.censorship.mask_timing_normalization_enabled {
         let floor = config.censorship.mask_timing_normalization_floor_ms;
         let ceiling = config.censorship.mask_timing_normalization_ceiling_ms;
+        if floor == 0 {
+            if ceiling == 0 {
+                return Duration::from_millis(0);
+            }
+            let mut rng = rand::rng();
+            return Duration::from_millis(rng.random_range(0..=ceiling));
+        }
         if ceiling > floor {
             let mut rng = rand::rng();
             return Duration::from_millis(rng.random_range(floor..=ceiling));
@@ -219,14 +297,7 @@ async fn wait_mask_outcome_budget(started: Instant, config: &ProxyConfig) {
 /// Detect client type based on initial data
 fn detect_client_type(data: &[u8]) -> &'static str {
     // Check for HTTP request
-    if data.len() > 4
-        && (data.starts_with(b"GET ")
-            || data.starts_with(b"POST")
-            || data.starts_with(b"HEAD")
-            || data.starts_with(b"PUT ")
-            || data.starts_with(b"DELETE")
-            || data.starts_with(b"OPTIONS"))
-    {
+    if is_http_probe(data) {
         return "HTTP";
     }
 
@@ -248,6 +319,244 @@ fn detect_client_type(data: &[u8]) -> &'static str {
     "unknown"
 }
 
+fn parse_mask_host_ip_literal(host: &str) -> Option<IpAddr> {
+    if host.starts_with('[') && host.ends_with(']') {
+        return host[1..host.len() - 1].parse::<IpAddr>().ok();
+    }
+    host.parse::<IpAddr>().ok()
+}
+
+fn canonical_ip(ip: IpAddr) -> IpAddr {
+    match ip {
+        IpAddr::V6(v6) => v6.to_ipv4_mapped().map(IpAddr::V4).unwrap_or(IpAddr::V6(v6)),
+        IpAddr::V4(v4) => IpAddr::V4(v4),
+    }
+}
+
+#[cfg(unix)]
+fn collect_local_interface_ips() -> Vec<IpAddr> {
+    #[cfg(test)]
+    LOCAL_INTERFACE_ENUMERATIONS.fetch_add(1, Ordering::Relaxed);
+
+    let mut out = Vec::new();
+    if let Ok(addrs) = getifaddrs() {
+        for iface in addrs {
+            if let Some(address) = iface.address {
+                if let Some(v4) = address.as_sockaddr_in() {
+                    out.push(canonical_ip(IpAddr::V4(v4.ip())));
+                } else if let Some(v6) = address.as_sockaddr_in6() {
+                    out.push(canonical_ip(IpAddr::V6(v6.ip())));
+                }
+            }
+        }
+    }
+    out
+}
+
+fn choose_interface_snapshot(previous: &[IpAddr], refreshed: Vec<IpAddr>) -> Vec<IpAddr> {
+    if refreshed.is_empty() && !previous.is_empty() {
+        return previous.to_vec();
+    }
+
+    refreshed
+}
+
+#[cfg(unix)]
+#[derive(Default)]
+struct LocalInterfaceCache {
+    ips: Vec<IpAddr>,
+    refreshed_at: Option<StdInstant>,
+}
+
+#[cfg(unix)]
+static LOCAL_INTERFACE_CACHE: OnceLock<Mutex<LocalInterfaceCache>> = OnceLock::new();
+
+#[cfg(unix)]
+static LOCAL_INTERFACE_REFRESH_LOCK: OnceLock<AsyncMutex<()>> = OnceLock::new();
+
+#[cfg(all(unix, test))]
+fn local_interface_ips() -> Vec<IpAddr> {
+    let cache = LOCAL_INTERFACE_CACHE.get_or_init(|| Mutex::new(LocalInterfaceCache::default()));
+    let mut guard = cache.lock().unwrap_or_else(|poison| poison.into_inner());
+
+    let stale = guard
+        .refreshed_at
+        .is_none_or(|at| at.elapsed() >= LOCAL_INTERFACE_CACHE_TTL);
+    if stale {
+        let refreshed = collect_local_interface_ips();
+        guard.ips = choose_interface_snapshot(&guard.ips, refreshed);
+        guard.refreshed_at = Some(StdInstant::now());
+    }
+
+    guard.ips.clone()
+}
+
+#[cfg(unix)]
+async fn local_interface_ips_async() -> Vec<IpAddr> {
+    let cache = LOCAL_INTERFACE_CACHE.get_or_init(|| Mutex::new(LocalInterfaceCache::default()));
+
+    {
+        let guard = cache.lock().unwrap_or_else(|poison| poison.into_inner());
+        let stale = guard
+            .refreshed_at
+            .is_none_or(|at| at.elapsed() >= LOCAL_INTERFACE_CACHE_TTL);
+        if !stale {
+            return guard.ips.clone();
+        }
+    }
+
+    let refresh_lock = LOCAL_INTERFACE_REFRESH_LOCK.get_or_init(|| AsyncMutex::new(()));
+    let _refresh_guard = refresh_lock.lock().await;
+
+    {
+        let guard = cache.lock().unwrap_or_else(|poison| poison.into_inner());
+        let stale = guard
+            .refreshed_at
+            .is_none_or(|at| at.elapsed() >= LOCAL_INTERFACE_CACHE_TTL);
+        if !stale {
+            return guard.ips.clone();
+        }
+    }
+
+    let refreshed = tokio::task::spawn_blocking(collect_local_interface_ips)
+        .await
+        .unwrap_or_default();
+
+    let mut guard = cache.lock().unwrap_or_else(|poison| poison.into_inner());
+    let stale = guard
+        .refreshed_at
+        .is_none_or(|at| at.elapsed() >= LOCAL_INTERFACE_CACHE_TTL);
+    if stale {
+        guard.ips = choose_interface_snapshot(&guard.ips, refreshed);
+        guard.refreshed_at = Some(StdInstant::now());
+    }
+
+    guard.ips.clone()
+}
+
+#[cfg(all(not(unix), test))]
+fn local_interface_ips() -> Vec<IpAddr> {
+    Vec::new()
+}
+
+#[cfg(not(unix))]
+async fn local_interface_ips_async() -> Vec<IpAddr> {
+    Vec::new()
+}
+
+#[cfg(test)]
+static LOCAL_INTERFACE_ENUMERATIONS: AtomicUsize = AtomicUsize::new(0);
+
+#[cfg(test)]
+fn reset_local_interface_enumerations_for_tests() {
+    LOCAL_INTERFACE_ENUMERATIONS.store(0, Ordering::Relaxed);
+
+    #[cfg(unix)]
+    if let Some(cache) = LOCAL_INTERFACE_CACHE.get() {
+        let mut guard = cache.lock().unwrap_or_else(|poison| poison.into_inner());
+        guard.ips.clear();
+        guard.refreshed_at = None;
+    }
+}
+
+#[cfg(test)]
+fn local_interface_enumerations_for_tests() -> usize {
+    LOCAL_INTERFACE_ENUMERATIONS.load(Ordering::Relaxed)
+}
+
+fn is_mask_target_local_listener_with_interfaces(
+    mask_host: &str,
+    mask_port: u16,
+    local_addr: SocketAddr,
+    resolved_override: Option<SocketAddr>,
+    interface_ips: &[IpAddr],
+) -> bool {
+    if mask_port != local_addr.port() {
+        return false;
+    }
+
+    let local_ip = canonical_ip(local_addr.ip());
+    let literal_mask_ip = parse_mask_host_ip_literal(mask_host).map(canonical_ip);
+
+    if let Some(addr) = resolved_override {
+        let resolved_ip = canonical_ip(addr.ip());
+        if resolved_ip == local_ip {
+            return true;
+        }
+
+        if local_ip.is_unspecified()
+            && (resolved_ip.is_loopback()
+                || resolved_ip.is_unspecified()
+                || interface_ips.contains(&resolved_ip))
+        {
+            return true;
+        }
+    }
+
+    if let Some(mask_ip) = literal_mask_ip {
+        if mask_ip == local_ip {
+            return true;
+        }
+
+        if local_ip.is_unspecified()
+            && (mask_ip.is_loopback()
+                || mask_ip.is_unspecified()
+                || interface_ips.contains(&mask_ip))
+        {
+            return true;
+        }
+    }
+
+    false
+}
+
+#[cfg(test)]
+fn is_mask_target_local_listener(
+    mask_host: &str,
+    mask_port: u16,
+    local_addr: SocketAddr,
+    resolved_override: Option<SocketAddr>,
+) -> bool {
+    if mask_port != local_addr.port() {
+        return false;
+    }
+
+    let interfaces = local_interface_ips();
+    is_mask_target_local_listener_with_interfaces(
+        mask_host,
+        mask_port,
+        local_addr,
+        resolved_override,
+        &interfaces,
+    )
+}
+
+async fn is_mask_target_local_listener_async(
+    mask_host: &str,
+    mask_port: u16,
+    local_addr: SocketAddr,
+    resolved_override: Option<SocketAddr>,
+) -> bool {
+    if mask_port != local_addr.port() {
+        return false;
+    }
+
+    let interfaces = local_interface_ips_async().await;
+    is_mask_target_local_listener_with_interfaces(
+        mask_host,
+        mask_port,
+        local_addr,
+        resolved_override,
+        &interfaces,
+    )
+}
+
+fn masking_beobachten_ttl(config: &ProxyConfig) -> Duration {
+    let minutes = config.general.beobachten_minutes;
+    let clamped = minutes.clamp(1, 24 * 60);
+    Duration::from_secs(clamped.saturating_mul(60))
+}
+
 fn build_mask_proxy_header(
     version: u8,
     peer: SocketAddr,
@@ -290,13 +599,14 @@ pub async fn handle_bad_client<R, W>(
 {
     let client_type = detect_client_type(initial_data);
     if config.general.beobachten {
-        let ttl = Duration::from_secs(config.general.beobachten_minutes.saturating_mul(60));
+        let ttl = masking_beobachten_ttl(config);
         beobachten.record(client_type, peer.ip(), ttl);
     }
 
     if !config.censorship.mask {
         // Masking disabled, just consume data
-        consume_client_data_with_timeout(reader).await;
+        consume_client_data_with_timeout_and_cap(reader, config.censorship.mask_relay_max_bytes)
+            .await;
         return;
     }
 
@@ -341,6 +651,7 @@ pub async fn handle_bad_client<R, W>(
                         config.censorship.mask_shape_above_cap_blur,
                         config.censorship.mask_shape_above_cap_blur_max_bytes,
                         config.censorship.mask_shape_hardening_aggressive_mode,
+                        config.censorship.mask_relay_max_bytes,
                     ),
                 )
                 .await
@@ -353,12 +664,12 @@ pub async fn handle_bad_client<R, W>(
             Ok(Err(e)) => {
                 wait_mask_connect_budget_if_needed(connect_started, config).await;
                 debug!(error = %e, "Failed to connect to mask unix socket");
-                consume_client_data_with_timeout(reader).await;
+                consume_client_data_with_timeout_and_cap(reader, config.censorship.mask_relay_max_bytes).await;
                 wait_mask_outcome_budget(outcome_started, config).await;
             }
             Err(_) => {
                 debug!("Timeout connecting to mask unix socket");
-                consume_client_data_with_timeout(reader).await;
+                consume_client_data_with_timeout_and_cap(reader, config.censorship.mask_relay_max_bytes).await;
                 wait_mask_outcome_budget(outcome_started, config).await;
             }
         }
@@ -372,6 +683,28 @@ pub async fn handle_bad_client<R, W>(
         .unwrap_or(&config.censorship.tls_domain);
     let mask_port = config.censorship.mask_port;
 
+    // Fail closed when fallback points at our own listener endpoint.
+    // Self-referential masking can create recursive proxy loops under
+    // misconfiguration and leak distinguishable load spikes to adversaries.
+    let resolved_mask_addr = resolve_socket_addr(mask_host, mask_port);
+    if is_mask_target_local_listener_async(mask_host, mask_port, local_addr, resolved_mask_addr)
+        .await
+    {
+        let outcome_started = Instant::now();
+        debug!(
+            client_type = client_type,
+            host = %mask_host,
+            port = mask_port,
+            local = %local_addr,
+            "Mask target resolves to local listener; refusing self-referential masking fallback"
+        );
+        consume_client_data_with_timeout_and_cap(reader, config.censorship.mask_relay_max_bytes).await;
+        wait_mask_outcome_budget(outcome_started, config).await;
+        return;
+    }
+
+    let outcome_started = Instant::now();
+
     debug!(
         client_type = client_type,
         host = %mask_host,
@@ -381,10 +714,9 @@ pub async fn handle_bad_client<R, W>(
     );
 
     // Apply runtime DNS override for mask target when configured.
-    let mask_addr = resolve_socket_addr(mask_host, mask_port)
+    let mask_addr = resolved_mask_addr
         .map(|addr| addr.to_string())
         .unwrap_or_else(|| format!("{}:{}", mask_host, mask_port));
-    let outcome_started = Instant::now();
     let connect_started = Instant::now();
     let connect_result = timeout(MASK_TIMEOUT, TcpStream::connect(&mask_addr)).await;
     match connect_result {
@@ -413,6 +745,7 @@ pub async fn handle_bad_client<R, W>(
                     config.censorship.mask_shape_above_cap_blur,
                     config.censorship.mask_shape_above_cap_blur_max_bytes,
                     config.censorship.mask_shape_hardening_aggressive_mode,
+                    config.censorship.mask_relay_max_bytes,
                 ),
             )
             .await
@@ -425,12 +758,12 @@ pub async fn handle_bad_client<R, W>(
         Ok(Err(e)) => {
             wait_mask_connect_budget_if_needed(connect_started, config).await;
             debug!(error = %e, "Failed to connect to mask host");
-            consume_client_data_with_timeout(reader).await;
+            consume_client_data_with_timeout_and_cap(reader, config.censorship.mask_relay_max_bytes).await;
             wait_mask_outcome_budget(outcome_started, config).await;
         }
         Err(_) => {
             debug!("Timeout connecting to mask host");
-            consume_client_data_with_timeout(reader).await;
+            consume_client_data_with_timeout_and_cap(reader, config.censorship.mask_relay_max_bytes).await;
             wait_mask_outcome_budget(outcome_started, config).await;
         }
     }
@@ -449,6 +782,7 @@ async fn relay_to_mask<R, W, MR, MW>(
     shape_above_cap_blur: bool,
     shape_above_cap_blur_max_bytes: usize,
     shape_hardening_aggressive_mode: bool,
+    mask_relay_max_bytes: usize,
 ) where
     R: AsyncRead + Unpin + Send + 'static,
     W: AsyncWrite + Unpin + Send + 'static,
@@ -464,8 +798,18 @@ async fn relay_to_mask<R, W, MR, MW>(
     }
 
     let (upstream_copy, downstream_copy) = tokio::join!(
-        async { copy_with_idle_timeout(&mut reader, &mut mask_write).await },
-        async { copy_with_idle_timeout(&mut mask_read, &mut writer).await }
+        async {
+            copy_with_idle_timeout(
+                &mut reader,
+                &mut mask_write,
+                mask_relay_max_bytes,
+                !shape_hardening_enabled,
+            )
+            .await
+        },
+        async {
+            copy_with_idle_timeout(&mut mask_read, &mut writer, mask_relay_max_bytes, true).await
+        }
     );
 
     let total_sent = initial_data.len().saturating_add(upstream_copy.total);
@@ -491,13 +835,36 @@ async fn relay_to_mask<R, W, MR, MW>(
     let _ = writer.shutdown().await;
 }
 
-/// Just consume all data from client without responding
-async fn consume_client_data<R: AsyncRead + Unpin>(mut reader: R) {
-    let mut buf = vec![0u8; MASK_BUFFER_SIZE];
-    while let Ok(n) = reader.read(&mut buf).await {
+/// Just consume all data from client without responding.
+async fn consume_client_data<R: AsyncRead + Unpin>(mut reader: R, byte_cap: usize) {
+    if byte_cap == 0 {
+        return;
+    }
+
+    // Keep drain path fail-closed under slow-loris stalls.
+    let mut buf = Box::new([0u8; MASK_BUFFER_SIZE]);
+    let mut total = 0usize;
+
+    loop {
+        let remaining_budget = byte_cap.saturating_sub(total);
+        if remaining_budget == 0 {
+            break;
+        }
+
+        let read_len = remaining_budget.min(MASK_BUFFER_SIZE);
+        let n = match timeout(MASK_RELAY_IDLE_TIMEOUT, reader.read(&mut buf[..read_len])).await {
+            Ok(Ok(n)) => n,
+            Ok(Err(_)) | Err(_) => break,
+        };
+
         if n == 0 {
             break;
         }
+
+        total = total.saturating_add(n);
+        if total >= byte_cap {
+            break;
+        }
     }
 }
 
@@ -521,6 +888,10 @@ mod masking_shape_above_cap_blur_security_tests;
 #[path = "tests/masking_timing_normalization_security_tests.rs"]
 mod masking_timing_normalization_security_tests;
 
+#[cfg(test)]
+#[path = "tests/masking_timing_budget_coupling_security_tests.rs"]
+mod masking_timing_budget_coupling_security_tests;
+
 #[cfg(test)]
 #[path = "tests/masking_ab_envelope_blur_integration_security_tests.rs"]
 mod masking_ab_envelope_blur_integration_security_tests;
@@ -548,3 +919,75 @@ mod masking_aggressive_mode_security_tests;
 #[cfg(test)]
 #[path = "tests/masking_timing_sidechannel_redteam_expected_fail_tests.rs"]
 mod masking_timing_sidechannel_redteam_expected_fail_tests;
+
+#[cfg(test)]
+#[path = "tests/masking_self_target_loop_security_tests.rs"]
+mod masking_self_target_loop_security_tests;
+
+#[cfg(test)]
+#[path = "tests/masking_classification_completeness_security_tests.rs"]
+mod masking_classification_completeness_security_tests;
+
+#[cfg(test)]
+#[path = "tests/masking_relay_guardrails_security_tests.rs"]
+mod masking_relay_guardrails_security_tests;
+
+#[cfg(test)]
+#[path = "tests/masking_connect_failure_close_matrix_security_tests.rs"]
+mod masking_connect_failure_close_matrix_security_tests;
+
+#[cfg(test)]
+#[path = "tests/masking_additional_hardening_security_tests.rs"]
+mod masking_additional_hardening_security_tests;
+
+#[cfg(test)]
+#[path = "tests/masking_consume_idle_timeout_security_tests.rs"]
+mod masking_consume_idle_timeout_security_tests;
+
+#[cfg(test)]
+#[path = "tests/masking_http2_probe_classification_security_tests.rs"]
+mod masking_http2_probe_classification_security_tests;
+
+#[cfg(test)]
+#[path = "tests/masking_http_probe_boundary_security_tests.rs"]
+mod masking_http_probe_boundary_security_tests;
+
+#[cfg(test)]
+#[path = "tests/masking_rng_hoist_perf_regression_tests.rs"]
+mod masking_rng_hoist_perf_regression_tests;
+
+#[cfg(test)]
+#[path = "tests/masking_http2_preface_integration_security_tests.rs"]
+mod masking_http2_preface_integration_security_tests;
+
+#[cfg(test)]
+#[path = "tests/masking_consume_stress_adversarial_tests.rs"]
+mod masking_consume_stress_adversarial_tests;
+
+#[cfg(test)]
+#[path = "tests/masking_interface_cache_security_tests.rs"]
+mod masking_interface_cache_security_tests;
+
+#[cfg(test)]
+#[path = "tests/masking_interface_cache_defense_in_depth_security_tests.rs"]
+mod masking_interface_cache_defense_in_depth_security_tests;
+
+#[cfg(test)]
+#[path = "tests/masking_interface_cache_concurrency_security_tests.rs"]
+mod masking_interface_cache_concurrency_security_tests;
+
+#[cfg(test)]
+#[path = "tests/masking_production_cap_regression_security_tests.rs"]
+mod masking_production_cap_regression_security_tests;
+
+#[cfg(test)]
+#[path = "tests/masking_extended_attack_surface_security_tests.rs"]
+mod masking_extended_attack_surface_security_tests;
+
+#[cfg(test)]
+#[path = "tests/masking_padding_timeout_adversarial_tests.rs"]
+mod masking_padding_timeout_adversarial_tests;
+
+#[cfg(all(test, feature = "redteam_offline_expected_fail"))]
+#[path = "tests/masking_offline_target_redteam_expected_fail_tests.rs"]
+mod masking_offline_target_redteam_expected_fail_tests;

src/proxy/middle_relay.rs

@@ -1,5 +1,7 @@
 use std::collections::hash_map::RandomState;
 use std::collections::{BTreeSet, HashMap};
+#[cfg(test)]
+use std::future::Future;
 use std::hash::{BuildHasher, Hash};
 use std::net::{IpAddr, SocketAddr};
 use std::sync::atomic::{AtomicBool, AtomicU64, Ordering};
@@ -8,7 +10,7 @@ use std::time::{Duration, Instant};
 
 use dashmap::DashMap;
 use tokio::io::{AsyncRead, AsyncReadExt, AsyncWrite, AsyncWriteExt};
-use tokio::sync::{Mutex as AsyncMutex, mpsc, oneshot, watch};
+use tokio::sync::{mpsc, oneshot, watch};
 use tokio::time::timeout;
 use tracing::{debug, info, trace, warn};
 
@@ -21,7 +23,7 @@ use crate::proxy::route_mode::{
     ROUTE_SWITCH_ERROR_MSG, RelayRouteMode, RouteCutoverState, affected_cutover_state,
     cutover_stagger_delay,
 };
-use crate::stats::{MeD2cFlushReason, MeD2cQuotaRejectStage, MeD2cWriteMode, Stats};
+use crate::stats::{MeD2cFlushReason, MeD2cQuotaRejectStage, MeD2cWriteMode, QuotaReserveError, Stats, UserStats};
 use crate::stream::{BufferPool, CryptoReader, CryptoWriter, PooledBuffer};
 use crate::transport::middle_proxy::{MePool, MeResponse, proto_flags_for_tag};
 
@@ -39,28 +41,23 @@ const C2ME_CHANNEL_CAPACITY_FALLBACK: usize = 128;
 const C2ME_SOFT_PRESSURE_MIN_FREE_SLOTS: usize = 64;
 const C2ME_SENDER_FAIRNESS_BUDGET: usize = 32;
 const RELAY_IDLE_IO_POLL_MAX: Duration = Duration::from_secs(1);
+const TINY_FRAME_DEBT_PER_TINY: u32 = 8;
+const TINY_FRAME_DEBT_LIMIT: u32 = 512;
 #[cfg(test)]
 const C2ME_SEND_TIMEOUT: Duration = Duration::from_millis(50);
 #[cfg(not(test))]
 const C2ME_SEND_TIMEOUT: Duration = Duration::from_secs(5);
+#[cfg(test)]
+const RELAY_TEST_STEP_TIMEOUT: Duration = Duration::from_secs(1);
 const ME_D2C_FLUSH_BATCH_MAX_FRAMES_MIN: usize = 1;
 const ME_D2C_FLUSH_BATCH_MAX_BYTES_MIN: usize = 4096;
 const ME_D2C_FRAME_BUF_SHRINK_HYSTERESIS_FACTOR: usize = 2;
 const ME_D2C_SINGLE_WRITE_COALESCE_MAX_BYTES: usize = 128 * 1024;
-#[cfg(test)]
-const QUOTA_USER_LOCKS_MAX: usize = 64;
-#[cfg(not(test))]
-const QUOTA_USER_LOCKS_MAX: usize = 4_096;
-#[cfg(test)]
-const QUOTA_OVERFLOW_LOCK_STRIPES: usize = 16;
-#[cfg(not(test))]
-const QUOTA_OVERFLOW_LOCK_STRIPES: usize = 256;
+const QUOTA_RESERVE_SPIN_RETRIES: usize = 32;
 static DESYNC_DEDUP: OnceLock<DashMap<u64, Instant>> = OnceLock::new();
 static DESYNC_HASHER: OnceLock<RandomState> = OnceLock::new();
 static DESYNC_FULL_CACHE_LAST_EMIT_AT: OnceLock<Mutex<Option<Instant>>> = OnceLock::new();
 static DESYNC_DEDUP_EVER_SATURATED: OnceLock<AtomicBool> = OnceLock::new();
-static QUOTA_USER_LOCKS: OnceLock<DashMap<String, Arc<AsyncMutex<()>>>> = OnceLock::new();
-static QUOTA_USER_OVERFLOW_LOCKS: OnceLock<Vec<Arc<AsyncMutex<()>>>> = OnceLock::new();
 static RELAY_IDLE_CANDIDATE_REGISTRY: OnceLock<Mutex<RelayIdleCandidateRegistry>> = OnceLock::new();
 static RELAY_IDLE_MARK_SEQ: AtomicU64 = AtomicU64::new(0);
 
@@ -94,10 +91,23 @@ fn relay_idle_candidate_registry() -> &'static Mutex<RelayIdleCandidateRegistry>
     RELAY_IDLE_CANDIDATE_REGISTRY.get_or_init(|| Mutex::new(RelayIdleCandidateRegistry::default()))
 }
 
+fn relay_idle_candidate_registry_lock() -> std::sync::MutexGuard<'static, RelayIdleCandidateRegistry> {
+    let registry = relay_idle_candidate_registry();
+    match registry.lock() {
+        Ok(guard) => guard,
+        Err(poisoned) => {
+            let mut guard = poisoned.into_inner();
+            // Fail closed after panic while holding registry lock: drop all
+            // candidates and pressure cursors to avoid stale cross-session state.
+            *guard = RelayIdleCandidateRegistry::default();
+            registry.clear_poison();
+            guard
+        }
+    }
+}
+
 fn mark_relay_idle_candidate(conn_id: u64) -> bool {
-    let Ok(mut guard) = relay_idle_candidate_registry().lock() else {
-        return false;
-    };
+    let mut guard = relay_idle_candidate_registry_lock();
 
     if guard.by_conn_id.contains_key(&conn_id) {
         return false;
@@ -116,9 +126,7 @@ fn mark_relay_idle_candidate(conn_id: u64) -> bool {
 }
 
 fn clear_relay_idle_candidate(conn_id: u64) {
-    let Ok(mut guard) = relay_idle_candidate_registry().lock() else {
-        return;
-    };
+    let mut guard = relay_idle_candidate_registry_lock();
 
     if let Some(meta) = guard.by_conn_id.remove(&conn_id) {
         guard.ordered.remove(&(meta.mark_order_seq, conn_id));
@@ -127,23 +135,17 @@ fn clear_relay_idle_candidate(conn_id: u64) {
 
 #[cfg(test)]
 fn oldest_relay_idle_candidate() -> Option<u64> {
-    let Ok(guard) = relay_idle_candidate_registry().lock() else {
-        return None;
-    };
+    let guard = relay_idle_candidate_registry_lock();
     guard.ordered.iter().next().map(|(_, conn_id)| *conn_id)
 }
 
 fn note_relay_pressure_event() {
-    let Ok(mut guard) = relay_idle_candidate_registry().lock() else {
-        return;
-    };
+    let mut guard = relay_idle_candidate_registry_lock();
     guard.pressure_event_seq = guard.pressure_event_seq.wrapping_add(1);
 }
 
 fn relay_pressure_event_seq() -> u64 {
-    let Ok(guard) = relay_idle_candidate_registry().lock() else {
-        return 0;
-    };
+    let guard = relay_idle_candidate_registry_lock();
     guard.pressure_event_seq
 }
 
@@ -152,9 +154,7 @@ fn maybe_evict_idle_candidate_on_pressure(
     seen_pressure_seq: &mut u64,
     stats: &Stats,
 ) -> bool {
-    let Ok(mut guard) = relay_idle_candidate_registry().lock() else {
-        return false;
-    };
+    let mut guard = relay_idle_candidate_registry_lock();
 
     let latest_pressure_seq = guard.pressure_event_seq;
     if latest_pressure_seq == *seen_pressure_seq {
@@ -199,13 +199,9 @@ fn maybe_evict_idle_candidate_on_pressure(
 
 #[cfg(test)]
 fn clear_relay_idle_pressure_state_for_testing() {
-    if let Some(registry) = RELAY_IDLE_CANDIDATE_REGISTRY.get()
-        && let Ok(mut guard) = registry.lock()
-    {
-        guard.by_conn_id.clear();
-        guard.ordered.clear();
-        guard.pressure_event_seq = 0;
-        guard.pressure_consumed_seq = 0;
+    if RELAY_IDLE_CANDIDATE_REGISTRY.get().is_some() {
+        let mut guard = relay_idle_candidate_registry_lock();
+        *guard = RelayIdleCandidateRegistry::default();
     }
     RELAY_IDLE_MARK_SEQ.store(0, Ordering::Relaxed);
 }
@@ -259,6 +255,7 @@ impl RelayClientIdlePolicy {
 struct RelayClientIdleState {
     last_client_frame_at: Instant,
     soft_idle_marked: bool,
+    tiny_frame_debt: u32,
 }
 
 impl RelayClientIdleState {
@@ -266,6 +263,7 @@ impl RelayClientIdleState {
         Self {
             last_client_frame_at: now,
             soft_idle_marked: false,
+            tiny_frame_debt: 0,
         }
     }
 
@@ -531,48 +529,28 @@ fn should_yield_c2me_sender(sent_since_yield: usize, has_backlog: bool) -> bool
     has_backlog && sent_since_yield >= C2ME_SENDER_FAIRNESS_BUDGET
 }
 
-fn quota_exceeded_for_user(stats: &Stats, user: &str, quota_limit: Option<u64>) -> bool {
-    quota_limit.is_some_and(|quota| stats.get_user_total_octets(user) >= quota)
-}
-
-#[cfg_attr(not(test), allow(dead_code))]
-fn quota_would_be_exceeded_for_user(
-    stats: &Stats,
-    user: &str,
-    quota_limit: Option<u64>,
-    bytes: u64,
-) -> bool {
-    quota_limit.is_some_and(|quota| {
-        let used = stats.get_user_total_octets(user);
-        used >= quota || bytes > quota.saturating_sub(used)
-    })
-}
-
 fn quota_soft_cap(limit: u64, overshoot: u64) -> u64 {
     limit.saturating_add(overshoot)
 }
 
-fn quota_exceeded_for_user_soft(
-    stats: &Stats,
-    user: &str,
-    quota_limit: Option<u64>,
-    overshoot: u64,
-) -> bool {
-    quota_limit.is_some_and(|quota| stats.get_user_total_octets(user) >= quota_soft_cap(quota, overshoot))
-}
-
-fn quota_would_be_exceeded_for_user_soft(
-    stats: &Stats,
-    user: &str,
-    quota_limit: Option<u64>,
+async fn reserve_user_quota_with_yield(
+    user_stats: &UserStats,
     bytes: u64,
-    overshoot: u64,
-) -> bool {
-    quota_limit.is_some_and(|quota| {
-        let cap = quota_soft_cap(quota, overshoot);
-        let used = stats.get_user_total_octets(user);
-        used >= cap || bytes > cap.saturating_sub(used)
-    })
+    limit: u64,
+) -> std::result::Result<u64, QuotaReserveError> {
+    loop {
+        for _ in 0..QUOTA_RESERVE_SPIN_RETRIES {
+            match user_stats.quota_try_reserve(bytes, limit) {
+                Ok(total) => return Ok(total),
+                Err(QuotaReserveError::LimitExceeded) => {
+                    return Err(QuotaReserveError::LimitExceeded);
+                }
+                Err(QuotaReserveError::Contended) => std::hint::spin_loop(),
+            }
+        }
+
+        tokio::task::yield_now().await;
+    }
 }
 
 fn classify_me_d2c_flush_reason(
@@ -619,53 +597,18 @@ fn observe_me_d2c_flush_event(
 }
 
 #[cfg(test)]
-fn quota_user_lock_test_guard() -> &'static Mutex<()> {
+fn relay_idle_pressure_test_guard() -> &'static Mutex<()> {
     static TEST_LOCK: OnceLock<Mutex<()>> = OnceLock::new();
     TEST_LOCK.get_or_init(|| Mutex::new(()))
 }
 
 #[cfg(test)]
-fn quota_user_lock_test_scope() -> std::sync::MutexGuard<'static, ()> {
-    quota_user_lock_test_guard()
+pub(crate) fn relay_idle_pressure_test_scope() -> std::sync::MutexGuard<'static, ()> {
+    relay_idle_pressure_test_guard()
         .lock()
         .unwrap_or_else(|poisoned| poisoned.into_inner())
 }
 
-fn quota_overflow_user_lock(user: &str) -> Arc<AsyncMutex<()>> {
-    let stripes = QUOTA_USER_OVERFLOW_LOCKS.get_or_init(|| {
-        (0..QUOTA_OVERFLOW_LOCK_STRIPES)
-            .map(|_| Arc::new(AsyncMutex::new(())))
-            .collect()
-    });
-
-    let hash = crc32fast::hash(user.as_bytes()) as usize;
-    Arc::clone(&stripes[hash % stripes.len()])
-}
-
-fn quota_user_lock(user: &str) -> Arc<AsyncMutex<()>> {
-    let locks = QUOTA_USER_LOCKS.get_or_init(DashMap::new);
-    if let Some(existing) = locks.get(user) {
-        return Arc::clone(existing.value());
-    }
-
-    if locks.len() >= QUOTA_USER_LOCKS_MAX {
-        locks.retain(|_, value| Arc::strong_count(value) > 1);
-    }
-
-    if locks.len() >= QUOTA_USER_LOCKS_MAX {
-        return quota_overflow_user_lock(user);
-    }
-
-    let created = Arc::new(AsyncMutex::new(()));
-    match locks.entry(user.to_string()) {
-        dashmap::mapref::entry::Entry::Occupied(entry) => Arc::clone(entry.get()),
-        dashmap::mapref::entry::Entry::Vacant(entry) => {
-            entry.insert(Arc::clone(&created));
-            created
-        }
-    }
-}
-
 async fn enqueue_c2me_command(
     tx: &mpsc::Sender<C2MeCommand>,
     cmd: C2MeCommand,
@@ -691,6 +634,16 @@ async fn enqueue_c2me_command(
     }
 }
 
+#[cfg(test)]
+async fn run_relay_test_step_timeout<F, T>(context: &'static str, fut: F) -> T
+where
+    F: Future<Output = T>,
+{
+    timeout(RELAY_TEST_STEP_TIMEOUT, fut)
+        .await
+        .unwrap_or_else(|_| panic!("{context} exceeded {}s", RELAY_TEST_STEP_TIMEOUT.as_secs()))
+}
+
 pub(crate) async fn handle_via_middle_proxy<R, W>(
     mut crypto_reader: CryptoReader<R>,
     crypto_writer: CryptoWriter<W>,
@@ -711,6 +664,7 @@ where
 {
     let user = success.user.clone();
     let quota_limit = config.access.user_data_quota.get(&user).copied();
+    let quota_user_stats = quota_limit.map(|_| stats.get_or_create_user_stats_handle(&user));
     let peer = success.peer;
     let proto_tag = success.proto_tag;
     let pool_generation = me_pool.current_generation();
@@ -837,6 +791,7 @@ where
     let stats_clone = stats.clone();
     let rng_clone = rng.clone();
     let user_clone = user.clone();
+    let quota_user_stats_me_writer = quota_user_stats.clone();
     let last_downstream_activity_ms_clone = last_downstream_activity_ms.clone();
     let bytes_me2c_clone = bytes_me2c.clone();
     let d2c_flush_policy = MeD2cFlushPolicy::from_config(&config);
@@ -866,6 +821,7 @@ where
                         &mut frame_buf,
                         stats_clone.as_ref(),
                         &user_clone,
+                        quota_user_stats_me_writer.as_deref(),
                         quota_limit,
                         d2c_flush_policy.quota_soft_overshoot_bytes,
                         bytes_me2c_clone.as_ref(),
@@ -924,6 +880,7 @@ where
                             &mut frame_buf,
                             stats_clone.as_ref(),
                             &user_clone,
+                            quota_user_stats_me_writer.as_deref(),
                             quota_limit,
                             d2c_flush_policy.quota_soft_overshoot_bytes,
                             bytes_me2c_clone.as_ref(),
@@ -985,6 +942,7 @@ where
                                     &mut frame_buf,
                                     stats_clone.as_ref(),
                                     &user_clone,
+                                    quota_user_stats_me_writer.as_deref(),
                                     quota_limit,
                                     d2c_flush_policy.quota_soft_overshoot_bytes,
                                     bytes_me2c_clone.as_ref(),
@@ -1048,6 +1006,7 @@ where
                                         &mut frame_buf,
                                         stats_clone.as_ref(),
                                         &user_clone,
+                                        quota_user_stats_me_writer.as_deref(),
                                         quota_limit,
                                         d2c_flush_policy.quota_soft_overshoot_bytes,
                                         bytes_me2c_clone.as_ref(),
@@ -1219,16 +1178,23 @@ where
                         forensics.bytes_c2me = forensics
                             .bytes_c2me
                             .saturating_add(payload.len() as u64);
-                        if let Some(limit) = quota_limit {
-                            let quota_lock = quota_user_lock(&user);
-                            let _quota_guard = quota_lock.lock().await;
-                            stats.add_user_octets_from(&user, payload.len() as u64);
-                            if quota_exceeded_for_user(stats.as_ref(), &user, Some(limit)) {
+                        if let (Some(limit), Some(user_stats)) =
+                            (quota_limit, quota_user_stats.as_deref())
+                        {
+                            if reserve_user_quota_with_yield(
+                                user_stats,
+                                payload.len() as u64,
+                                limit,
+                            )
+                            .await
+                            .is_err()
+                            {
                                 main_result = Err(ProxyError::DataQuotaExceeded {
                                     user: user.clone(),
                                 });
                                 break;
                             }
+                            stats.add_user_octets_from_handle(user_stats, payload.len() as u64);
                         } else {
                             stats.add_user_octets_from(&user, payload.len() as u64);
                         }
@@ -1321,6 +1287,8 @@ async fn read_client_payload_with_idle_policy<R>(
 where
     R: AsyncRead + Unpin + Send + 'static,
 {
+    const LEGACY_MAX_CONSECUTIVE_ZERO_LEN_FRAMES: u32 = 4;
+
     async fn read_exact_with_policy<R>(
         client_reader: &mut CryptoReader<R>,
         buf: &mut [u8],
@@ -1459,6 +1427,7 @@ where
         Ok(())
     }
 
+    let mut consecutive_zero_len_frames = 0u32;
     loop {
         let (len, quickack, raw_len_bytes) = match proto_tag {
             ProtoTag::Abridged => {
@@ -1539,6 +1508,27 @@ where
         };
 
         if len == 0 {
+            idle_state.tiny_frame_debt = idle_state
+                .tiny_frame_debt
+                .saturating_add(TINY_FRAME_DEBT_PER_TINY);
+            if idle_state.tiny_frame_debt >= TINY_FRAME_DEBT_LIMIT {
+                stats.increment_relay_protocol_desync_close_total();
+                return Err(ProxyError::Proxy(format!(
+                    "Tiny frame overhead limit exceeded: debt={}, conn_id={}",
+                    idle_state.tiny_frame_debt, forensics.conn_id
+                )));
+            }
+
+            if !idle_policy.enabled {
+                consecutive_zero_len_frames =
+                    consecutive_zero_len_frames.saturating_add(1);
+                if consecutive_zero_len_frames > LEGACY_MAX_CONSECUTIVE_ZERO_LEN_FRAMES {
+                    stats.increment_relay_protocol_desync_close_total();
+                    return Err(ProxyError::Proxy(
+                        "Excessive zero-length abridged frames".to_string(),
+                    ));
+                }
+            }
             continue;
         }
         if len < 4 && proto_tag != ProtoTag::Abridged {
@@ -1607,6 +1597,7 @@ where
         }
         *frame_counter += 1;
         idle_state.on_client_frame(Instant::now());
+        idle_state.tiny_frame_debt = idle_state.tiny_frame_debt.saturating_sub(1);
         clear_relay_idle_candidate(forensics.conn_id);
         return Ok(Some((payload, quickack)));
     }
@@ -1690,6 +1681,7 @@ async fn process_me_writer_response<W>(
     frame_buf: &mut Vec<u8>,
     stats: &Stats,
     user: &str,
+    quota_user_stats: Option<&UserStats>,
     quota_limit: Option<u64>,
     quota_soft_overshoot_bytes: u64,
     bytes_me2c: &AtomicU64,
@@ -1708,40 +1700,42 @@ where
                 trace!(conn_id, bytes = data.len(), flags, "ME->C data");
             }
             let data_len = data.len() as u64;
-            if quota_would_be_exceeded_for_user_soft(
-                stats,
-                user,
-                quota_limit,
-                data_len,
-                quota_soft_overshoot_bytes,
-            ) {
-                stats.increment_me_d2c_quota_reject_total(MeD2cQuotaRejectStage::PreWrite);
-                return Err(ProxyError::DataQuotaExceeded {
-                    user: user.to_string(),
-                });
+            if let (Some(limit), Some(user_stats)) = (quota_limit, quota_user_stats) {
+                let soft_limit = quota_soft_cap(limit, quota_soft_overshoot_bytes);
+                if reserve_user_quota_with_yield(user_stats, data_len, soft_limit)
+                    .await
+                    .is_err()
+                {
+                    stats.increment_me_d2c_quota_reject_total(MeD2cQuotaRejectStage::PreWrite);
+                    return Err(ProxyError::DataQuotaExceeded {
+                        user: user.to_string(),
+                    });
+                }
             }
 
             let write_mode =
-                write_client_payload(client_writer, proto_tag, flags, &data, rng, frame_buf)
-                    .await?;
-            stats.increment_me_d2c_write_mode(write_mode);
+                match write_client_payload(client_writer, proto_tag, flags, &data, rng, frame_buf)
+                    .await
+                {
+                    Ok(mode) => mode,
+                    Err(err) => {
+                        if quota_limit.is_some() {
+                            stats.add_quota_write_fail_bytes_total(data_len);
+                            stats.increment_quota_write_fail_events_total();
+                        }
+                        return Err(err);
+                    }
+                };
 
-            bytes_me2c.fetch_add(data.len() as u64, Ordering::Relaxed);
-            stats.add_user_octets_to(user, data.len() as u64);
-            stats.increment_me_d2c_data_frames_total();
-            stats.add_me_d2c_payload_bytes_total(data.len() as u64);
-
-            if quota_exceeded_for_user_soft(
-                stats,
-                user,
-                quota_limit,
-                quota_soft_overshoot_bytes,
-            ) {
-                stats.increment_me_d2c_quota_reject_total(MeD2cQuotaRejectStage::PostWrite);
-                return Err(ProxyError::DataQuotaExceeded {
-                    user: user.to_string(),
-                });
+            bytes_me2c.fetch_add(data_len, Ordering::Relaxed);
+            if let Some(user_stats) = quota_user_stats {
+                stats.add_user_octets_to_handle(user_stats, data_len);
+            } else {
+                stats.add_user_octets_to(user, data_len);
             }
+            stats.increment_me_d2c_data_frames_total();
+            stats.add_me_d2c_payload_bytes_total(data_len);
+            stats.increment_me_d2c_write_mode(write_mode);
 
             Ok(MeWriterResponseOutcome::Continue {
                 frames: 1,
@@ -1948,10 +1942,6 @@ where
         .map_err(ProxyError::Io)
 }
 
-#[cfg(test)]
-#[path = "tests/middle_relay_security_tests.rs"]
-mod security_tests;
-
 #[cfg(test)]
 #[path = "tests/middle_relay_idle_policy_security_tests.rs"]
 mod idle_policy_security_tests;
@@ -1964,18 +1954,26 @@ mod desync_all_full_dedup_security_tests;
 #[path = "tests/middle_relay_stub_completion_security_tests.rs"]
 mod stub_completion_security_tests;
 
-#[cfg(test)]
-#[path = "tests/middle_relay_coverage_high_risk_security_tests.rs"]
-mod coverage_high_risk_security_tests;
-
-#[cfg(test)]
-#[path = "tests/middle_relay_quota_overflow_lock_security_tests.rs"]
-mod quota_overflow_lock_security_tests;
-
 #[cfg(test)]
 #[path = "tests/middle_relay_length_cast_hardening_security_tests.rs"]
 mod length_cast_hardening_security_tests;
 
 #[cfg(test)]
-#[path = "tests/middle_relay_blackhat_campaign_integration_tests.rs"]
-mod blackhat_campaign_integration_tests;
+#[path = "tests/middle_relay_idle_registry_poison_security_tests.rs"]
+mod middle_relay_idle_registry_poison_security_tests;
+
+#[cfg(test)]
+#[path = "tests/middle_relay_zero_length_frame_security_tests.rs"]
+mod middle_relay_zero_length_frame_security_tests;
+
+#[cfg(test)]
+#[path = "tests/middle_relay_tiny_frame_debt_security_tests.rs"]
+mod middle_relay_tiny_frame_debt_security_tests;
+
+#[cfg(test)]
+#[path = "tests/middle_relay_tiny_frame_debt_concurrency_security_tests.rs"]
+mod middle_relay_tiny_frame_debt_concurrency_security_tests;
+
+#[cfg(test)]
+#[path = "tests/middle_relay_tiny_frame_debt_proto_chunking_security_tests.rs"]
+mod middle_relay_tiny_frame_debt_proto_chunking_security_tests;

src/proxy/relay.rs

@@ -52,13 +52,12 @@
 //! - `SharedCounters` (atomics) let the watchdog read stats without locking
 
 use crate::error::{ProxyError, Result};
-use crate::stats::Stats;
+use crate::stats::{Stats, UserStats};
 use crate::stream::BufferPool;
-use dashmap::DashMap;
 use std::io;
 use std::pin::Pin;
 use std::sync::atomic::{AtomicBool, AtomicU64, Ordering};
-use std::sync::{Arc, Mutex, OnceLock};
+use std::sync::Arc;
 use std::task::{Context, Poll};
 use std::time::Duration;
 use tokio::io::{AsyncRead, AsyncWrite, AsyncWriteExt, ReadBuf, copy_bidirectional_with_sizes};
@@ -209,12 +208,10 @@ struct StatsIo<S> {
     counters: Arc<SharedCounters>,
     stats: Arc<Stats>,
     user: String,
+    user_stats: Arc<UserStats>,
     quota_limit: Option<u64>,
     quota_exceeded: Arc<AtomicBool>,
-    quota_read_wake_scheduled: bool,
-    quota_write_wake_scheduled: bool,
-    quota_read_retry_active: Arc<AtomicBool>,
-    quota_write_retry_active: Arc<AtomicBool>,
+    quota_bytes_since_check: u64,
     epoch: Instant,
 }
 
@@ -230,30 +227,21 @@ impl<S> StatsIo<S> {
     ) -> Self {
         // Mark initial activity so the watchdog doesn't fire before data flows
         counters.touch(Instant::now(), epoch);
+        let user_stats = stats.get_or_create_user_stats_handle(&user);
         Self {
             inner,
             counters,
             stats,
             user,
+            user_stats,
             quota_limit,
             quota_exceeded,
-            quota_read_wake_scheduled: false,
-            quota_write_wake_scheduled: false,
-            quota_read_retry_active: Arc::new(AtomicBool::new(false)),
-            quota_write_retry_active: Arc::new(AtomicBool::new(false)),
+            quota_bytes_since_check: 0,
             epoch,
         }
     }
 }
 
-impl<S> Drop for StatsIo<S> {
-    fn drop(&mut self) {
-        self.quota_read_retry_active.store(false, Ordering::Relaxed);
-        self.quota_write_retry_active
-            .store(false, Ordering::Relaxed);
-    }
-}
-
 #[derive(Debug)]
 struct QuotaIoSentinel;
 
@@ -277,84 +265,24 @@ fn is_quota_io_error(err: &io::Error) -> bool {
             .is_some()
 }
 
-#[cfg(test)]
-const QUOTA_CONTENTION_RETRY_INTERVAL: Duration = Duration::from_millis(1);
-#[cfg(not(test))]
-const QUOTA_CONTENTION_RETRY_INTERVAL: Duration = Duration::from_millis(2);
+const QUOTA_NEAR_LIMIT_BYTES: u64 = 64 * 1024;
+const QUOTA_LARGE_CHARGE_BYTES: u64 = 16 * 1024;
+const QUOTA_ADAPTIVE_INTERVAL_MIN_BYTES: u64 = 4 * 1024;
+const QUOTA_ADAPTIVE_INTERVAL_MAX_BYTES: u64 = 64 * 1024;
 
-fn spawn_quota_retry_waker(retry_active: Arc<AtomicBool>, waker: std::task::Waker) {
-    tokio::task::spawn(async move {
-        loop {
-            if !retry_active.load(Ordering::Relaxed) {
-                break;
-            }
-            tokio::time::sleep(QUOTA_CONTENTION_RETRY_INTERVAL).await;
-            if !retry_active.load(Ordering::Relaxed) {
-                break;
-            }
-            waker.wake_by_ref();
-        }
-    });
+#[inline]
+fn quota_adaptive_interval_bytes(remaining_before: u64) -> u64 {
+    remaining_before
+        .saturating_div(2)
+        .clamp(
+            QUOTA_ADAPTIVE_INTERVAL_MIN_BYTES,
+            QUOTA_ADAPTIVE_INTERVAL_MAX_BYTES,
+        )
 }
 
-static QUOTA_USER_LOCKS: OnceLock<DashMap<String, Arc<Mutex<()>>>> = OnceLock::new();
-static QUOTA_USER_OVERFLOW_LOCKS: OnceLock<Vec<Arc<Mutex<()>>>> = OnceLock::new();
-
-#[cfg(test)]
-const QUOTA_USER_LOCKS_MAX: usize = 64;
-#[cfg(not(test))]
-const QUOTA_USER_LOCKS_MAX: usize = 4_096;
-#[cfg(test)]
-const QUOTA_OVERFLOW_LOCK_STRIPES: usize = 16;
-#[cfg(not(test))]
-const QUOTA_OVERFLOW_LOCK_STRIPES: usize = 256;
-
-#[cfg(test)]
-fn quota_user_lock_test_guard() -> &'static Mutex<()> {
-    static TEST_LOCK: OnceLock<Mutex<()>> = OnceLock::new();
-    TEST_LOCK.get_or_init(|| Mutex::new(()))
-}
-
-#[cfg(test)]
-fn quota_user_lock_test_scope() -> std::sync::MutexGuard<'static, ()> {
-    quota_user_lock_test_guard()
-        .lock()
-        .unwrap_or_else(|poisoned| poisoned.into_inner())
-}
-
-fn quota_overflow_user_lock(user: &str) -> Arc<Mutex<()>> {
-    let stripes = QUOTA_USER_OVERFLOW_LOCKS.get_or_init(|| {
-        (0..QUOTA_OVERFLOW_LOCK_STRIPES)
-            .map(|_| Arc::new(Mutex::new(())))
-            .collect()
-    });
-
-    let hash = crc32fast::hash(user.as_bytes()) as usize;
-    Arc::clone(&stripes[hash % stripes.len()])
-}
-
-fn quota_user_lock(user: &str) -> Arc<Mutex<()>> {
-    let locks = QUOTA_USER_LOCKS.get_or_init(DashMap::new);
-    if let Some(existing) = locks.get(user) {
-        return Arc::clone(existing.value());
-    }
-
-    if locks.len() >= QUOTA_USER_LOCKS_MAX {
-        locks.retain(|_, value| Arc::strong_count(value) > 1);
-    }
-
-    if locks.len() >= QUOTA_USER_LOCKS_MAX {
-        return quota_overflow_user_lock(user);
-    }
-
-    let created = Arc::new(Mutex::new(()));
-    match locks.entry(user.to_string()) {
-        dashmap::mapref::entry::Entry::Occupied(entry) => Arc::clone(entry.get()),
-        dashmap::mapref::entry::Entry::Vacant(entry) => {
-            entry.insert(Arc::clone(&created));
-            created
-        }
-    }
+#[inline]
+fn should_immediate_quota_check(remaining_before: u64, charge_bytes: u64) -> bool {
+    remaining_before <= QUOTA_NEAR_LIMIT_BYTES || charge_bytes >= QUOTA_LARGE_CHARGE_BYTES
 }
 
 impl<S: AsyncRead + Unpin> AsyncRead for StatsIo<S> {
@@ -364,80 +292,60 @@ impl<S: AsyncRead + Unpin> AsyncRead for StatsIo<S> {
         buf: &mut ReadBuf<'_>,
     ) -> Poll<io::Result<()>> {
         let this = self.get_mut();
-        if this.quota_exceeded.load(Ordering::Relaxed) {
+        if this.quota_exceeded.load(Ordering::Acquire) {
             return Poll::Ready(Err(quota_io_error()));
         }
 
-        let quota_lock = this
-            .quota_limit
-            .is_some()
-            .then(|| quota_user_lock(&this.user));
-        let _quota_guard = if let Some(lock) = quota_lock.as_ref() {
-            match lock.try_lock() {
-                Ok(guard) => {
-                    this.quota_read_wake_scheduled = false;
-                    this.quota_read_retry_active.store(false, Ordering::Relaxed);
-                    Some(guard)
-                }
-                Err(_) => {
-                    if !this.quota_read_wake_scheduled {
-                        this.quota_read_wake_scheduled = true;
-                        this.quota_read_retry_active.store(true, Ordering::Relaxed);
-                        spawn_quota_retry_waker(
-                            Arc::clone(&this.quota_read_retry_active),
-                            cx.waker().clone(),
-                        );
-                    }
-                    return Poll::Pending;
-                }
+        let mut remaining_before = None;
+        if let Some(limit) = this.quota_limit {
+            let used_before = this.user_stats.quota_used();
+            let remaining = limit.saturating_sub(used_before);
+            if remaining == 0 {
+                this.quota_exceeded.store(true, Ordering::Release);
+                return Poll::Ready(Err(quota_io_error()));
             }
-        } else {
-            None
-        };
-
-        if let Some(limit) = this.quota_limit
-            && this.stats.get_user_total_octets(&this.user) >= limit
-        {
-            this.quota_exceeded.store(true, Ordering::Relaxed);
-            return Poll::Ready(Err(quota_io_error()));
+            remaining_before = Some(remaining);
         }
+
         let before = buf.filled().len();
 
         match Pin::new(&mut this.inner).poll_read(cx, buf) {
             Poll::Ready(Ok(())) => {
                 let n = buf.filled().len() - before;
                 if n > 0 {
-                    let mut reached_quota_boundary = false;
-                    if let Some(limit) = this.quota_limit {
-                        let used = this.stats.get_user_total_octets(&this.user);
-                        if used >= limit {
-                            this.quota_exceeded.store(true, Ordering::Relaxed);
-                            return Poll::Ready(Err(quota_io_error()));
-                        }
-
-                        let remaining = limit - used;
-                        if (n as u64) > remaining {
-                            // Fail closed: when a single read chunk would cross quota,
-                            // stop relay immediately without accounting beyond the cap.
-                            this.quota_exceeded.store(true, Ordering::Relaxed);
-                            return Poll::Ready(Err(quota_io_error()));
-                        }
-
-                        reached_quota_boundary = (n as u64) == remaining;
-                    }
+                    let n_to_charge = n as u64;
 
                     // C→S: client sent data
                     this.counters
                         .c2s_bytes
-                        .fetch_add(n as u64, Ordering::Relaxed);
+                        .fetch_add(n_to_charge, Ordering::Relaxed);
                     this.counters.c2s_ops.fetch_add(1, Ordering::Relaxed);
                     this.counters.touch(Instant::now(), this.epoch);
 
-                    this.stats.add_user_octets_from(&this.user, n as u64);
-                    this.stats.increment_user_msgs_from(&this.user);
+                    this.stats
+                        .add_user_octets_from_handle(this.user_stats.as_ref(), n_to_charge);
+                    this.stats
+                        .increment_user_msgs_from_handle(this.user_stats.as_ref());
 
-                    if reached_quota_boundary {
-                        this.quota_exceeded.store(true, Ordering::Relaxed);
+                    if let (Some(limit), Some(remaining)) = (this.quota_limit, remaining_before) {
+                        this.stats
+                            .quota_charge_post_write(this.user_stats.as_ref(), n_to_charge);
+                        if should_immediate_quota_check(remaining, n_to_charge) {
+                            this.quota_bytes_since_check = 0;
+                            if this.user_stats.quota_used() >= limit {
+                                this.quota_exceeded.store(true, Ordering::Release);
+                            }
+                        } else {
+                            this.quota_bytes_since_check =
+                                this.quota_bytes_since_check.saturating_add(n_to_charge);
+                            let interval = quota_adaptive_interval_bytes(remaining);
+                            if this.quota_bytes_since_check >= interval {
+                                this.quota_bytes_since_check = 0;
+                                if this.user_stats.quota_used() >= limit {
+                                    this.quota_exceeded.store(true, Ordering::Release);
+                                }
+                            }
+                        }
                     }
 
                     trace!(user = %this.user, bytes = n, "C->S");
@@ -456,75 +364,57 @@ impl<S: AsyncWrite + Unpin> AsyncWrite for StatsIo<S> {
         buf: &[u8],
     ) -> Poll<io::Result<usize>> {
         let this = self.get_mut();
-        if this.quota_exceeded.load(Ordering::Relaxed) {
+        if this.quota_exceeded.load(Ordering::Acquire) {
             return Poll::Ready(Err(quota_io_error()));
         }
 
-        let quota_lock = this
-            .quota_limit
-            .is_some()
-            .then(|| quota_user_lock(&this.user));
-        let _quota_guard = if let Some(lock) = quota_lock.as_ref() {
-            match lock.try_lock() {
-                Ok(guard) => {
-                    this.quota_write_wake_scheduled = false;
-                    this.quota_write_retry_active
-                        .store(false, Ordering::Relaxed);
-                    Some(guard)
-                }
-                Err(_) => {
-                    if !this.quota_write_wake_scheduled {
-                        this.quota_write_wake_scheduled = true;
-                        this.quota_write_retry_active.store(true, Ordering::Relaxed);
-                        spawn_quota_retry_waker(
-                            Arc::clone(&this.quota_write_retry_active),
-                            cx.waker().clone(),
-                        );
-                    }
-                    return Poll::Pending;
-                }
-            }
-        } else {
-            None
-        };
-
-        let write_buf = if let Some(limit) = this.quota_limit {
-            let used = this.stats.get_user_total_octets(&this.user);
-            if used >= limit {
-                this.quota_exceeded.store(true, Ordering::Relaxed);
+        let mut remaining_before = None;
+        if let Some(limit) = this.quota_limit {
+            let used_before = this.user_stats.quota_used();
+            let remaining = limit.saturating_sub(used_before);
+            if remaining == 0 {
+                this.quota_exceeded.store(true, Ordering::Release);
                 return Poll::Ready(Err(quota_io_error()));
             }
+            remaining_before = Some(remaining);
+        }
 
-            let remaining = (limit - used) as usize;
-            if buf.len() > remaining {
-                // Fail closed: do not emit partial S->C payload when remaining
-                // quota cannot accommodate the pending write request.
-                this.quota_exceeded.store(true, Ordering::Relaxed);
-                return Poll::Ready(Err(quota_io_error()));
-            }
-            buf
-        } else {
-            buf
-        };
-
-        match Pin::new(&mut this.inner).poll_write(cx, write_buf) {
+        match Pin::new(&mut this.inner).poll_write(cx, buf) {
             Poll::Ready(Ok(n)) => {
                 if n > 0 {
+                    let n_to_charge = n as u64;
+
                     // S→C: data written to client
                     this.counters
                         .s2c_bytes
-                        .fetch_add(n as u64, Ordering::Relaxed);
+                        .fetch_add(n_to_charge, Ordering::Relaxed);
                     this.counters.s2c_ops.fetch_add(1, Ordering::Relaxed);
                     this.counters.touch(Instant::now(), this.epoch);
 
-                    this.stats.add_user_octets_to(&this.user, n as u64);
-                    this.stats.increment_user_msgs_to(&this.user);
+                    this.stats
+                        .add_user_octets_to_handle(this.user_stats.as_ref(), n_to_charge);
+                    this.stats
+                        .increment_user_msgs_to_handle(this.user_stats.as_ref());
 
-                    if let Some(limit) = this.quota_limit
-                        && this.stats.get_user_total_octets(&this.user) >= limit
-                    {
-                        this.quota_exceeded.store(true, Ordering::Relaxed);
-                        return Poll::Ready(Err(quota_io_error()));
+                    if let (Some(limit), Some(remaining)) = (this.quota_limit, remaining_before) {
+                        this.stats
+                            .quota_charge_post_write(this.user_stats.as_ref(), n_to_charge);
+                        if should_immediate_quota_check(remaining, n_to_charge) {
+                            this.quota_bytes_since_check = 0;
+                            if this.user_stats.quota_used() >= limit {
+                                this.quota_exceeded.store(true, Ordering::Release);
+                            }
+                        } else {
+                            this.quota_bytes_since_check =
+                                this.quota_bytes_since_check.saturating_add(n_to_charge);
+                            let interval = quota_adaptive_interval_bytes(remaining);
+                            if this.quota_bytes_since_check >= interval {
+                                this.quota_bytes_since_check = 0;
+                                if this.user_stats.quota_used() >= limit {
+                                    this.quota_exceeded.store(true, Ordering::Release);
+                                }
+                            }
+                        }
                     }
 
                     trace!(user = %this.user, bytes = n, "S->C");
@@ -618,7 +508,7 @@ where
             let now = Instant::now();
             let idle = wd_counters.idle_duration(now, epoch);
 
-            if wd_quota_exceeded.load(Ordering::Relaxed) {
+            if wd_quota_exceeded.load(Ordering::Acquire) {
                 warn!(user = %wd_user, "User data quota reached, closing relay");
                 return;
             }
@@ -756,18 +646,10 @@ where
     }
 }
 
-#[cfg(test)]
-#[path = "tests/relay_security_tests.rs"]
-mod security_tests;
-
 #[cfg(test)]
 #[path = "tests/relay_adversarial_tests.rs"]
 mod adversarial_tests;
 
-#[cfg(test)]
-#[path = "tests/relay_quota_lock_pressure_adversarial_tests.rs"]
-mod relay_quota_lock_pressure_adversarial_tests;
-
 #[cfg(test)]
 #[path = "tests/relay_quota_boundary_blackhat_tests.rs"]
 mod relay_quota_boundary_blackhat_tests;
@@ -780,14 +662,10 @@ mod relay_quota_model_adversarial_tests;
 #[path = "tests/relay_quota_overflow_regression_tests.rs"]
 mod relay_quota_overflow_regression_tests;
 
+#[cfg(test)]
+#[path = "tests/relay_quota_extended_attack_surface_security_tests.rs"]
+mod relay_quota_extended_attack_surface_security_tests;
+
 #[cfg(test)]
 #[path = "tests/relay_watchdog_delta_security_tests.rs"]
 mod relay_watchdog_delta_security_tests;
-
-#[cfg(test)]
-#[path = "tests/relay_quota_waker_storm_adversarial_tests.rs"]
-mod relay_quota_waker_storm_adversarial_tests;
-
-#[cfg(test)]
-#[path = "tests/relay_quota_wake_liveness_regression_tests.rs"]
-mod relay_quota_wake_liveness_regression_tests;

src/proxy/tests/client_clever_advanced_tests.rs

@@ -0,0 +1,409 @@
+use super::*;
+use crate::config::{UpstreamConfig, UpstreamType, ProxyConfig};
+use crate::protocol::constants::{MAX_TLS_PLAINTEXT_SIZE, MIN_TLS_CLIENT_HELLO_SIZE};
+use crate::stats::Stats;
+use crate::transport::UpstreamManager;
+use std::net::{IpAddr, Ipv4Addr, Ipv6Addr, SocketAddr};
+use std::pin::Pin;
+use std::sync::Arc;
+use std::task::{Context, Poll};
+use std::time::Duration;
+use tokio::io::{AsyncRead, AsyncReadExt, AsyncWriteExt, ReadBuf, duplex};
+use tokio::net::TcpListener;
+
+#[test]
+fn edge_mask_reject_delay_min_greater_than_max_does_not_panic() {
+    let mut config = ProxyConfig::default();
+    config.censorship.server_hello_delay_min_ms = 5000;
+    config.censorship.server_hello_delay_max_ms = 1000;
+
+    let rt = tokio::runtime::Runtime::new().unwrap();
+    rt.block_on(async {
+        let start = std::time::Instant::now();
+        maybe_apply_mask_reject_delay(&config).await;
+        let elapsed = start.elapsed();
+
+        assert!(elapsed >= Duration::from_millis(1000));
+        assert!(elapsed < Duration::from_millis(1500));
+    });
+}
+
+#[test]
+fn edge_handshake_timeout_with_mask_grace_saturating_add_prevents_overflow() {
+    let mut config = ProxyConfig::default();
+    config.timeouts.client_handshake = u64::MAX;
+    config.censorship.mask = true;
+
+    let timeout = handshake_timeout_with_mask_grace(&config);
+    assert_eq!(timeout.as_secs(), u64::MAX);
+}
+
+#[test]
+fn edge_tls_clienthello_len_in_bounds_exact_boundaries() {
+    assert!(tls_clienthello_len_in_bounds(MIN_TLS_CLIENT_HELLO_SIZE));
+    assert!(!tls_clienthello_len_in_bounds(MIN_TLS_CLIENT_HELLO_SIZE - 1));
+    assert!(tls_clienthello_len_in_bounds(MAX_TLS_PLAINTEXT_SIZE));
+    assert!(!tls_clienthello_len_in_bounds(MAX_TLS_PLAINTEXT_SIZE + 1));
+}
+
+#[test]
+fn edge_synthetic_local_addr_boundaries() {
+    assert_eq!(synthetic_local_addr(0).port(), 0);
+    assert_eq!(synthetic_local_addr(80).port(), 80);
+    assert_eq!(synthetic_local_addr(u16::MAX).port(), u16::MAX);
+}
+
+#[test]
+fn edge_beobachten_record_handshake_failure_class_stream_error_eof() {
+    let beobachten = BeobachtenStore::new();
+    let mut config = ProxyConfig::default();
+    config.general.beobachten = true;
+    config.general.beobachten_minutes = 1;
+
+    let eof_err = ProxyError::Stream(crate::error::StreamError::UnexpectedEof);
+    let peer_ip: IpAddr = "198.51.100.100".parse().unwrap();
+
+    record_handshake_failure_class(&beobachten, &config, peer_ip, &eof_err);
+
+    let snapshot = beobachten.snapshot_text(Duration::from_secs(60));
+    assert!(snapshot.contains("[expected_64_got_0]"));
+}
+
+#[tokio::test]
+async fn adversarial_tls_handshake_timeout_during_masking_delay() {
+    let mut cfg = ProxyConfig::default();
+    cfg.general.beobachten = false;
+    cfg.timeouts.client_handshake = 1;
+    cfg.censorship.mask = true;
+    cfg.censorship.server_hello_delay_min_ms = 3000;
+    cfg.censorship.server_hello_delay_max_ms = 3000;
+
+    let config = Arc::new(cfg);
+    let stats = Arc::new(Stats::new());
+    let (server_side, mut client_side) = duplex(4096);
+
+    let handle = tokio::spawn(handle_client_stream(
+        server_side,
+        "198.51.100.1:55000".parse().unwrap(),
+        config,
+        stats.clone(),
+        Arc::new(UpstreamManager::new(vec![], 1, 1, 1, 1, false, stats.clone())),
+        Arc::new(ReplayChecker::new(128, Duration::from_secs(60))),
+        Arc::new(BufferPool::new()),
+        Arc::new(SecureRandom::new()),
+        None,
+        Arc::new(RouteRuntimeController::new(RelayRouteMode::Direct)),
+        None,
+        Arc::new(UserIpTracker::new()),
+        Arc::new(BeobachtenStore::new()),
+        false,
+    ));
+
+    client_side.write_all(&[0x16, 0x03, 0x01, 0xFF, 0xFF]).await.unwrap();
+
+    let result = tokio::time::timeout(Duration::from_secs(4), handle)
+        .await
+        .unwrap()
+        .unwrap();
+
+    assert!(matches!(result, Err(ProxyError::TgHandshakeTimeout)));
+    assert_eq!(stats.get_handshake_timeouts(), 1);
+}
+
+#[tokio::test]
+async fn blackhat_proxy_protocol_slowloris_timeout() {
+    let mut cfg = ProxyConfig::default();
+    cfg.server.proxy_protocol_header_timeout_ms = 200;
+    let config = Arc::new(cfg);
+    let stats = Arc::new(Stats::new());
+
+    let (server_side, mut client_side) = duplex(4096);
+    let handle = tokio::spawn(handle_client_stream(
+        server_side,
+        "198.51.100.2:55000".parse().unwrap(),
+        config,
+        stats.clone(),
+        Arc::new(UpstreamManager::new(vec![], 1, 1, 1, 1, false, stats.clone())),
+        Arc::new(ReplayChecker::new(128, Duration::from_secs(60))),
+        Arc::new(BufferPool::new()),
+        Arc::new(SecureRandom::new()),
+        None,
+        Arc::new(RouteRuntimeController::new(RelayRouteMode::Direct)),
+        None,
+        Arc::new(UserIpTracker::new()),
+        Arc::new(BeobachtenStore::new()),
+        true,
+    ));
+
+    client_side.write_all(b"PROXY TCP4 192.").await.unwrap();
+    tokio::time::sleep(Duration::from_millis(300)).await;
+
+    let result = tokio::time::timeout(Duration::from_secs(2), handle)
+        .await
+        .unwrap()
+        .unwrap();
+
+    assert!(matches!(result, Err(ProxyError::InvalidProxyProtocol)));
+    assert_eq!(stats.get_connects_bad(), 1);
+}
+
+#[test]
+fn blackhat_ipv4_mapped_ipv6_proxy_source_bypass_attempt() {
+    let trusted = vec!["192.0.2.0/24".parse().unwrap()];
+    let peer_ip = IpAddr::V6(Ipv6Addr::new(0, 0, 0, 0, 0, 0xffff, 0xc000, 0x0201));
+    assert!(!is_trusted_proxy_source(peer_ip, &trusted));
+}
+
+#[tokio::test]
+async fn negative_proxy_protocol_enabled_but_client_sends_tls_hello() {
+    let mut cfg = ProxyConfig::default();
+    cfg.server.proxy_protocol_header_timeout_ms = 500;
+    let config = Arc::new(cfg);
+    let stats = Arc::new(Stats::new());
+
+    let (server_side, mut client_side) = duplex(4096);
+    let handle = tokio::spawn(handle_client_stream(
+        server_side,
+        "198.51.100.3:55000".parse().unwrap(),
+        config,
+        stats.clone(),
+        Arc::new(UpstreamManager::new(vec![], 1, 1, 1, 1, false, stats.clone())),
+        Arc::new(ReplayChecker::new(128, Duration::from_secs(60))),
+        Arc::new(BufferPool::new()),
+        Arc::new(SecureRandom::new()),
+        None,
+        Arc::new(RouteRuntimeController::new(RelayRouteMode::Direct)),
+        None,
+        Arc::new(UserIpTracker::new()),
+        Arc::new(BeobachtenStore::new()),
+        true,
+    ));
+
+    client_side.write_all(&[0x16, 0x03, 0x01, 0x02, 0x00]).await.unwrap();
+
+    let result = tokio::time::timeout(Duration::from_secs(2), handle)
+        .await
+        .unwrap()
+        .unwrap();
+
+    assert!(matches!(result, Err(ProxyError::InvalidProxyProtocol)));
+    assert_eq!(stats.get_connects_bad(), 1);
+}
+
+#[tokio::test]
+async fn edge_client_stream_exactly_4_bytes_eof() {
+    let config = Arc::new(ProxyConfig::default());
+    let stats = Arc::new(Stats::new());
+    let beobachten = Arc::new(BeobachtenStore::new());
+
+    let (server_side, mut client_side) = duplex(4096);
+    let handle = tokio::spawn(handle_client_stream(
+        server_side,
+        "198.51.100.4:55000".parse().unwrap(),
+        config,
+        stats.clone(),
+        Arc::new(UpstreamManager::new(vec![], 1, 1, 1, 1, false, stats.clone())),
+        Arc::new(ReplayChecker::new(128, Duration::from_secs(60))),
+        Arc::new(BufferPool::new()),
+        Arc::new(SecureRandom::new()),
+        None,
+        Arc::new(RouteRuntimeController::new(RelayRouteMode::Direct)),
+        None,
+        Arc::new(UserIpTracker::new()),
+        beobachten.clone(),
+        false,
+    ));
+
+    client_side.write_all(&[0x16, 0x03, 0x01, 0x00]).await.unwrap();
+    client_side.shutdown().await.unwrap();
+
+    let _ = tokio::time::timeout(Duration::from_secs(2), handle).await;
+
+    let snapshot = beobachten.snapshot_text(Duration::from_secs(60));
+    assert!(snapshot.contains("[expected_64_got_0]"));
+}
+
+#[tokio::test]
+async fn edge_client_stream_tls_header_valid_but_body_1_byte_short_eof() {
+    let config = Arc::new(ProxyConfig::default());
+    let stats = Arc::new(Stats::new());
+
+    let (server_side, mut client_side) = duplex(4096);
+    let handle = tokio::spawn(handle_client_stream(
+        server_side,
+        "198.51.100.5:55000".parse().unwrap(),
+        config,
+        stats.clone(),
+        Arc::new(UpstreamManager::new(vec![], 1, 1, 1, 1, false, stats.clone())),
+        Arc::new(ReplayChecker::new(128, Duration::from_secs(60))),
+        Arc::new(BufferPool::new()),
+        Arc::new(SecureRandom::new()),
+        None,
+        Arc::new(RouteRuntimeController::new(RelayRouteMode::Direct)),
+        None,
+        Arc::new(UserIpTracker::new()),
+        Arc::new(BeobachtenStore::new()),
+        false,
+    ));
+
+    client_side.write_all(&[0x16, 0x03, 0x01, 0x00, 100]).await.unwrap();
+    client_side.write_all(&vec![0x41; 99]).await.unwrap();
+    client_side.shutdown().await.unwrap();
+
+    let _ = tokio::time::timeout(Duration::from_secs(2), handle).await;
+    assert_eq!(stats.get_connects_bad(), 1);
+}
+
+#[tokio::test]
+async fn integration_non_tls_modes_disabled_immediately_masks() {
+    let mut cfg = ProxyConfig::default();
+    cfg.general.modes.classic = false;
+    cfg.general.modes.secure = false;
+    cfg.censorship.mask = true;
+    let config = Arc::new(cfg);
+    let stats = Arc::new(Stats::new());
+
+    let (server_side, mut client_side) = duplex(4096);
+    let handle = tokio::spawn(handle_client_stream(
+        server_side,
+        "198.51.100.6:55000".parse().unwrap(),
+        config,
+        stats.clone(),
+        Arc::new(UpstreamManager::new(vec![], 1, 1, 1, 1, false, stats.clone())),
+        Arc::new(ReplayChecker::new(128, Duration::from_secs(60))),
+        Arc::new(BufferPool::new()),
+        Arc::new(SecureRandom::new()),
+        None,
+        Arc::new(RouteRuntimeController::new(RelayRouteMode::Direct)),
+        None,
+        Arc::new(UserIpTracker::new()),
+        Arc::new(BeobachtenStore::new()),
+        false,
+    ));
+
+    client_side.write_all(b"GET / HTTP/1.1\r\n").await.unwrap();
+    let _ = tokio::time::timeout(Duration::from_secs(2), handle).await;
+    assert_eq!(stats.get_connects_bad(), 1);
+}
+
+struct YieldingReader {
+    data: Vec<u8>,
+    pos: usize,
+    yields_left: usize,
+}
+
+impl AsyncRead for YieldingReader {
+    fn poll_read(
+        self: Pin<&mut Self>,
+        cx: &mut Context<'_>,
+        buf: &mut ReadBuf<'_>,
+    ) -> Poll<std::io::Result<()>> {
+        let this = self.get_mut();
+        if this.yields_left > 0 {
+            this.yields_left -= 1;
+            cx.waker().wake_by_ref();
+            return Poll::Pending;
+        }
+        if this.pos >= this.data.len() {
+            return Poll::Ready(Ok(()));
+        }
+        buf.put_slice(&this.data[this.pos..this.pos + 1]);
+        this.pos += 1;
+        this.yields_left = 2;
+        Poll::Ready(Ok(()))
+    }
+}
+
+#[tokio::test]
+async fn fuzz_read_with_progress_heavy_yielding() {
+    let expected_data = b"HEAVY_YIELD_TEST_DATA".to_vec();
+    let mut reader = YieldingReader {
+        data: expected_data.clone(),
+        pos: 0,
+        yields_left: 2,
+    };
+
+    let mut buf = vec![0u8; expected_data.len()];
+    let read_bytes = read_with_progress(&mut reader, &mut buf).await.unwrap();
+
+    assert_eq!(read_bytes, expected_data.len());
+    assert_eq!(buf, expected_data);
+}
+
+#[test]
+fn edge_wrap_tls_application_record_exactly_u16_max() {
+    let payload = vec![0u8; 65535];
+    let wrapped = wrap_tls_application_record(&payload);
+    assert_eq!(wrapped.len(), 65540);
+    assert_eq!(wrapped[0], TLS_RECORD_APPLICATION);
+    assert_eq!(&wrapped[3..5], &65535u16.to_be_bytes());
+}
+
+#[test]
+fn fuzz_wrap_tls_application_record_lengths() {
+    let lengths = [0, 1, 65534, 65535, 65536, 131070, 131071, 131072];
+    for len in lengths {
+        let payload = vec![0u8; len];
+        let wrapped = wrap_tls_application_record(&payload);
+        let expected_chunks = len.div_ceil(65535).max(1);
+        assert_eq!(wrapped.len(), len + 5 * expected_chunks);
+    }
+}
+
+#[tokio::test]
+async fn stress_user_connection_reservation_concurrent_same_ip_exhaustion() {
+    let user = "stress-same-ip-user";
+    let mut config = ProxyConfig::default();
+    config.access.user_max_tcp_conns.insert(user.to_string(), 5);
+
+    let config = Arc::new(config);
+    let stats = Arc::new(Stats::new());
+    let ip_tracker = Arc::new(UserIpTracker::new());
+    ip_tracker.set_user_limit(user, 10).await;
+
+    let peer = SocketAddr::new(IpAddr::V4(Ipv4Addr::new(198, 51, 100, 77)), 55000);
+
+    let mut tasks = tokio::task::JoinSet::new();
+    let mut reservations = Vec::new();
+
+    for _ in 0..10 {
+        let config = config.clone();
+        let stats = stats.clone();
+        let ip_tracker = ip_tracker.clone();
+        tasks.spawn(async move {
+            RunningClientHandler::acquire_user_connection_reservation_static(
+                user,
+                &config,
+                stats,
+                peer,
+                ip_tracker,
+            )
+            .await
+        });
+    }
+
+    let mut successes = 0;
+    let mut failures = 0;
+
+    while let Some(res) = tasks.join_next().await {
+        match res.unwrap() {
+            Ok(r) => {
+                successes += 1;
+                reservations.push(r);
+            }
+            Err(_) => failures += 1,
+        }
+    }
+
+    assert_eq!(successes, 5);
+    assert_eq!(failures, 5);
+    assert_eq!(stats.get_user_curr_connects(user), 5);
+    assert_eq!(ip_tracker.get_active_ip_count(user).await, 1);
+
+    for reservation in reservations {
+        reservation.release().await;
+    }
+
+    assert_eq!(stats.get_user_curr_connects(user), 0);
+    assert_eq!(ip_tracker.get_active_ip_count(user).await, 0);
+}

src/proxy/tests/client_deep_invariants_tests.rs

@@ -0,0 +1,196 @@
+use super::*;
+use crate::config::ProxyConfig;
+use crate::protocol::constants::MIN_TLS_CLIENT_HELLO_SIZE;
+use crate::stats::Stats;
+use crate::transport::UpstreamManager;
+use std::sync::Arc;
+use std::time::Duration;
+use tokio::io::{AsyncWriteExt, duplex};
+
+#[test]
+fn invariant_wrap_tls_application_record_exact_multiples() {
+    let chunk_size = u16::MAX as usize;
+    let payload = vec![0xAA; chunk_size * 2];
+
+    let wrapped = wrap_tls_application_record(&payload);
+
+    assert_eq!(wrapped.len(), 2 * (5 + chunk_size));
+    assert_eq!(wrapped[0], TLS_RECORD_APPLICATION);
+    assert_eq!(&wrapped[3..5], &65535u16.to_be_bytes());
+
+    let second_header_idx = 5 + chunk_size;
+    assert_eq!(wrapped[second_header_idx], TLS_RECORD_APPLICATION);
+    assert_eq!(
+        &wrapped[second_header_idx + 3..second_header_idx + 5],
+        &65535u16.to_be_bytes()
+    );
+}
+
+#[tokio::test]
+async fn invariant_tls_clienthello_truncation_exact_boundary_triggers_masking() {
+    let config = Arc::new(ProxyConfig::default());
+    let stats = Arc::new(Stats::new());
+
+    let (server_side, mut client_side) = duplex(4096);
+    let handler = tokio::spawn(handle_client_stream(
+        server_side,
+        "198.51.100.20:55000".parse().unwrap(),
+        config,
+        stats.clone(),
+        Arc::new(UpstreamManager::new(vec![], 1, 1, 1, 1, false, stats.clone())),
+        Arc::new(ReplayChecker::new(128, Duration::from_secs(60))),
+        Arc::new(BufferPool::new()),
+        Arc::new(SecureRandom::new()),
+        None,
+        Arc::new(RouteRuntimeController::new(RelayRouteMode::Direct)),
+        None,
+        Arc::new(UserIpTracker::new()),
+        Arc::new(BeobachtenStore::new()),
+        false,
+    ));
+
+    let claimed_len = MIN_TLS_CLIENT_HELLO_SIZE as u16;
+    let mut header = vec![0x16, 0x03, 0x01];
+    header.extend_from_slice(&claimed_len.to_be_bytes());
+
+    client_side.write_all(&header).await.unwrap();
+    client_side
+        .write_all(&vec![0x42; MIN_TLS_CLIENT_HELLO_SIZE - 1])
+        .await
+        .unwrap();
+    client_side.shutdown().await.unwrap();
+
+    let _ = tokio::time::timeout(Duration::from_secs(2), handler).await.unwrap();
+    assert_eq!(stats.get_connects_bad(), 1);
+}
+
+#[tokio::test]
+async fn invariant_acquire_reservation_ip_limit_rollback() {
+    let user = "rollback-test-user";
+    let mut config = ProxyConfig::default();
+    config.access.user_max_tcp_conns.insert(user.to_string(), 10);
+
+    let stats = Arc::new(Stats::new());
+    let ip_tracker = Arc::new(UserIpTracker::new());
+    ip_tracker.set_user_limit(user, 1).await;
+
+    let peer_a = "198.51.100.21:55000".parse().unwrap();
+    let _res_a = RunningClientHandler::acquire_user_connection_reservation_static(
+        user,
+        &config,
+        stats.clone(),
+        peer_a,
+        ip_tracker.clone(),
+    )
+    .await
+    .unwrap();
+
+    assert_eq!(stats.get_user_curr_connects(user), 1);
+
+    let peer_b = "203.0.113.22:55000".parse().unwrap();
+    let res_b = RunningClientHandler::acquire_user_connection_reservation_static(
+        user,
+        &config,
+        stats.clone(),
+        peer_b,
+        ip_tracker.clone(),
+    )
+    .await;
+
+    assert!(matches!(
+        res_b,
+        Err(ProxyError::ConnectionLimitExceeded { .. })
+    ));
+    assert_eq!(stats.get_user_curr_connects(user), 1);
+}
+
+#[tokio::test]
+async fn invariant_quota_exact_boundary_inclusive() {
+    let user = "quota-strict-user";
+    let mut config = ProxyConfig::default();
+    config.access.user_data_quota.insert(user.to_string(), 1000);
+
+    let stats = Arc::new(Stats::new());
+    let ip_tracker = Arc::new(UserIpTracker::new());
+    let peer = "198.51.100.23:55000".parse().unwrap();
+
+    stats.add_user_octets_from(user, 999);
+    let res1 = RunningClientHandler::acquire_user_connection_reservation_static(
+        user,
+        &config,
+        stats.clone(),
+        peer,
+        ip_tracker.clone(),
+    )
+    .await;
+    assert!(res1.is_ok());
+    res1.unwrap().release().await;
+
+    stats.add_user_octets_from(user, 1);
+    let res2 = RunningClientHandler::acquire_user_connection_reservation_static(
+        user,
+        &config,
+        stats.clone(),
+        peer,
+        ip_tracker.clone(),
+    )
+    .await;
+    assert!(matches!(res2, Err(ProxyError::DataQuotaExceeded { .. })));
+}
+
+#[tokio::test]
+async fn invariant_direct_mode_partial_header_eof_is_error_not_bad_connect() {
+    let mut cfg = ProxyConfig::default();
+    cfg.general.beobachten = true;
+    cfg.general.beobachten_minutes = 1;
+
+    let config = Arc::new(cfg);
+    let stats = Arc::new(Stats::new());
+    let beobachten = Arc::new(BeobachtenStore::new());
+
+    let (server_side, mut client_side) = duplex(4096);
+    let handler = tokio::spawn(handle_client_stream(
+        server_side,
+        "198.51.100.25:55000".parse().unwrap(),
+        config,
+        stats.clone(),
+        Arc::new(UpstreamManager::new(vec![], 1, 1, 1, 1, false, stats.clone())),
+        Arc::new(ReplayChecker::new(128, Duration::from_secs(60))),
+        Arc::new(BufferPool::new()),
+        Arc::new(SecureRandom::new()),
+        None,
+        Arc::new(RouteRuntimeController::new(RelayRouteMode::Direct)),
+        None,
+        Arc::new(UserIpTracker::new()),
+        beobachten.clone(),
+        false,
+    ));
+
+    client_side.write_all(&[0xEF, 0xEF, 0xEF]).await.unwrap();
+    client_side.shutdown().await.unwrap();
+
+    let result = tokio::time::timeout(Duration::from_secs(2), handler)
+        .await
+        .unwrap()
+        .unwrap();
+
+    assert!(result.is_err());
+    assert_eq!(stats.get_connects_bad(), 0);
+    let snapshot = beobachten.snapshot_text(Duration::from_secs(60));
+    assert!(snapshot.contains("[expected_64_got_0]"));
+}
+
+#[tokio::test]
+async fn invariant_route_mode_snapshot_picks_up_latest_mode() {
+    let route_runtime = Arc::new(RouteRuntimeController::new(RelayRouteMode::Direct));
+    assert!(matches!(
+        route_runtime.snapshot().mode,
+        RelayRouteMode::Direct
+    ));
+
+    route_runtime.set_mode(RelayRouteMode::Middle);
+    assert!(matches!(
+        route_runtime.snapshot().mode,
+        RelayRouteMode::Middle
+    ));
+}

src/proxy/tests/client_masking_fragmented_classifier_security_tests.rs

@@ -0,0 +1,100 @@
+use super::*;
+use crate::config::{UpstreamConfig, UpstreamType};
+use std::sync::Arc;
+use tokio::io::{AsyncReadExt, AsyncWriteExt, duplex};
+use tokio::net::TcpListener;
+use tokio::time::Duration;
+
+fn new_upstream_manager(stats: Arc<Stats>) -> Arc<UpstreamManager> {
+    Arc::new(UpstreamManager::new(
+        vec![UpstreamConfig {
+            upstream_type: UpstreamType::Direct {
+                interface: None,
+                bind_addresses: None,
+            },
+            weight: 1,
+            enabled: true,
+            scopes: String::new(),
+            selected_scope: String::new(),
+        }],
+        1,
+        1,
+        1,
+        1,
+        false,
+        stats,
+    ))
+}
+
+#[tokio::test]
+async fn fragmented_connect_probe_is_classified_as_http_via_prefetch_window() {
+    let listener = TcpListener::bind("127.0.0.1:0").await.unwrap();
+    let backend_addr = listener.local_addr().unwrap();
+
+    let accept_task = tokio::spawn(async move {
+        let (mut stream, _) = listener.accept().await.unwrap();
+        let mut got = Vec::new();
+        stream.read_to_end(&mut got).await.unwrap();
+        got
+    });
+
+    let mut cfg = ProxyConfig::default();
+    cfg.general.beobachten = true;
+    cfg.general.beobachten_minutes = 1;
+    cfg.censorship.mask = true;
+    cfg.censorship.mask_unix_sock = None;
+    cfg.censorship.mask_host = Some("127.0.0.1".to_string());
+    cfg.censorship.mask_port = backend_addr.port();
+    cfg.general.modes.classic = false;
+    cfg.general.modes.secure = false;
+
+    let config = Arc::new(cfg);
+    let stats = Arc::new(Stats::new());
+    let beobachten = Arc::new(BeobachtenStore::new());
+
+    let (server_side, mut client_side) = duplex(4096);
+    let peer: SocketAddr = "198.51.100.251:57501".parse().unwrap();
+
+    let handler = tokio::spawn(handle_client_stream(
+        server_side,
+        peer,
+        config,
+        stats.clone(),
+        new_upstream_manager(stats),
+        Arc::new(ReplayChecker::new(128, Duration::from_secs(60))),
+        Arc::new(BufferPool::new()),
+        Arc::new(SecureRandom::new()),
+        None,
+        Arc::new(RouteRuntimeController::new(RelayRouteMode::Direct)),
+        None,
+        Arc::new(UserIpTracker::new()),
+        beobachten.clone(),
+        false,
+    ));
+
+    client_side.write_all(b"CONNE").await.unwrap();
+    client_side
+        .write_all(b"CT example.org:443 HTTP/1.1\r\nHost: example.org\r\n\r\n")
+        .await
+        .unwrap();
+    client_side.shutdown().await.unwrap();
+
+    let forwarded = tokio::time::timeout(Duration::from_secs(3), accept_task)
+        .await
+        .unwrap()
+        .unwrap();
+    assert!(
+        forwarded.starts_with(b"CONNECT example.org:443 HTTP/1.1"),
+        "mask backend must receive the full fragmented CONNECT probe"
+    );
+
+    let result = tokio::time::timeout(Duration::from_secs(3), handler)
+        .await
+        .unwrap()
+        .unwrap();
+    assert!(result.is_ok());
+
+    let snapshot = beobachten.snapshot_text(Duration::from_secs(60));
+    assert!(snapshot.contains("[HTTP]"));
+    assert!(snapshot.contains("198.51.100.251-1"));
+}

src/proxy/tests/client_masking_http2_fragmented_preface_security_tests.rs

@@ -0,0 +1,129 @@
+use super::*;
+use crate::config::{UpstreamConfig, UpstreamType};
+use std::sync::Arc;
+use tokio::io::{AsyncReadExt, AsyncWriteExt, duplex};
+use tokio::net::TcpListener;
+use tokio::time::{Duration, sleep};
+
+fn new_upstream_manager(stats: Arc<Stats>) -> Arc<UpstreamManager> {
+    Arc::new(UpstreamManager::new(
+        vec![UpstreamConfig {
+            upstream_type: UpstreamType::Direct {
+                interface: None,
+                bind_addresses: None,
+            },
+            weight: 1,
+            enabled: true,
+            scopes: String::new(),
+            selected_scope: String::new(),
+        }],
+        1,
+        1,
+        1,
+        1,
+        false,
+        stats,
+    ))
+}
+
+async fn run_http2_fragment_case(split_at: usize, delay_ms: u64, peer: SocketAddr) {
+    let listener = TcpListener::bind("127.0.0.1:0").await.unwrap();
+    let backend_addr = listener.local_addr().unwrap();
+    let preface = b"PRI * HTTP/2.0\r\n\r\nSM\r\n\r\n".to_vec();
+
+    let accept_task = tokio::spawn(async move {
+        let (mut stream, _) = listener.accept().await.unwrap();
+        let mut got = Vec::new();
+        stream.read_to_end(&mut got).await.unwrap();
+        got
+    });
+
+    let mut cfg = ProxyConfig::default();
+    cfg.general.beobachten = true;
+    cfg.general.beobachten_minutes = 1;
+    cfg.censorship.mask = true;
+    cfg.censorship.mask_unix_sock = None;
+    cfg.censorship.mask_host = Some("127.0.0.1".to_string());
+    cfg.censorship.mask_port = backend_addr.port();
+    cfg.general.modes.classic = false;
+    cfg.general.modes.secure = false;
+
+    let config = Arc::new(cfg);
+    let stats = Arc::new(Stats::new());
+    let beobachten = Arc::new(BeobachtenStore::new());
+
+    let (server_side, mut client_side) = duplex(4096);
+    let handler = tokio::spawn(handle_client_stream(
+        server_side,
+        peer,
+        config,
+        stats.clone(),
+        new_upstream_manager(stats),
+        Arc::new(ReplayChecker::new(128, Duration::from_secs(60))),
+        Arc::new(BufferPool::new()),
+        Arc::new(SecureRandom::new()),
+        None,
+        Arc::new(RouteRuntimeController::new(RelayRouteMode::Direct)),
+        None,
+        Arc::new(UserIpTracker::new()),
+        beobachten.clone(),
+        false,
+    ));
+
+    let first = split_at.min(preface.len());
+    client_side.write_all(&preface[..first]).await.unwrap();
+    if first < preface.len() {
+        sleep(Duration::from_millis(delay_ms)).await;
+        client_side.write_all(&preface[first..]).await.unwrap();
+    }
+    client_side.shutdown().await.unwrap();
+
+    let forwarded = tokio::time::timeout(Duration::from_secs(3), accept_task)
+        .await
+        .unwrap()
+        .unwrap();
+    assert!(
+        forwarded.starts_with(&preface),
+        "mask backend must receive an intact HTTP/2 preface prefix"
+    );
+
+    let result = tokio::time::timeout(Duration::from_secs(3), handler)
+        .await
+        .unwrap()
+        .unwrap();
+    assert!(result.is_ok());
+
+    let snapshot = beobachten.snapshot_text(Duration::from_secs(60));
+    assert!(snapshot.contains("[HTTP]"));
+    assert!(snapshot.contains(&format!("{}-1", peer.ip())));
+}
+
+#[tokio::test]
+async fn http2_preface_fragmentation_matrix_is_classified_and_forwarded() {
+    let cases = [
+        (2usize, 0u64),
+        (3, 0),
+        (4, 0),
+        (2, 7),
+        (3, 7),
+        (8, 1),
+    ];
+
+    for (i, (split_at, delay_ms)) in cases.into_iter().enumerate() {
+        let peer: SocketAddr = format!("198.51.100.{}:58{}", 140 + i, 100 + i)
+            .parse()
+            .unwrap();
+        run_http2_fragment_case(split_at, delay_ms, peer).await;
+    }
+}
+
+#[tokio::test]
+async fn http2_preface_splitpoint_light_fuzz_classifies_http() {
+    for split_at in 2usize..=12 {
+        let delay_ms = if split_at % 3 == 0 { 7 } else { 1 };
+        let peer: SocketAddr = format!("198.51.101.{}:59{}", split_at, 10 + split_at)
+            .parse()
+            .unwrap();
+        run_http2_fragment_case(split_at, delay_ms, peer).await;
+    }
+}

src/proxy/tests/client_masking_prefetch_config_pipeline_integration_security_tests.rs

@@ -0,0 +1,150 @@
+use super::*;
+use crate::config::{UpstreamConfig, UpstreamType};
+use std::sync::Arc;
+use tokio::io::{AsyncReadExt, AsyncWriteExt, duplex};
+use tokio::net::TcpListener;
+use tokio::time::{Duration, sleep};
+
+fn new_upstream_manager(stats: Arc<Stats>) -> Arc<UpstreamManager> {
+    Arc::new(UpstreamManager::new(
+        vec![UpstreamConfig {
+            upstream_type: UpstreamType::Direct {
+                interface: None,
+                bind_addresses: None,
+            },
+            weight: 1,
+            enabled: true,
+            scopes: String::new(),
+            selected_scope: String::new(),
+        }],
+        1,
+        1,
+        1,
+        1,
+        false,
+        stats,
+    ))
+}
+
+async fn run_pipeline_prefetch_case(
+    prefetch_timeout_ms: u64,
+    delayed_tail_ms: u64,
+    peer: SocketAddr,
+) -> (Vec<u8>, String) {
+    let listener = TcpListener::bind("127.0.0.1:0").await.unwrap();
+    let backend_addr = listener.local_addr().unwrap();
+
+    let accept_task = tokio::spawn(async move {
+        let (mut stream, _) = listener.accept().await.unwrap();
+        let mut got = Vec::new();
+        stream.read_to_end(&mut got).await.unwrap();
+        got
+    });
+
+    let mut cfg = ProxyConfig::default();
+    cfg.general.beobachten = true;
+    cfg.general.beobachten_minutes = 1;
+    cfg.censorship.mask = true;
+    cfg.censorship.mask_unix_sock = None;
+    cfg.censorship.mask_host = Some("127.0.0.1".to_string());
+    cfg.censorship.mask_port = backend_addr.port();
+    cfg.censorship.mask_classifier_prefetch_timeout_ms = prefetch_timeout_ms;
+    cfg.general.modes.classic = false;
+    cfg.general.modes.secure = false;
+
+    let config = Arc::new(cfg);
+    let stats = Arc::new(Stats::new());
+    let beobachten = Arc::new(BeobachtenStore::new());
+
+    let (server_side, mut client_side) = duplex(4096);
+    let handler = tokio::spawn(handle_client_stream(
+        server_side,
+        peer,
+        config,
+        stats.clone(),
+        new_upstream_manager(stats),
+        Arc::new(ReplayChecker::new(128, Duration::from_secs(60))),
+        Arc::new(BufferPool::new()),
+        Arc::new(SecureRandom::new()),
+        None,
+        Arc::new(RouteRuntimeController::new(RelayRouteMode::Direct)),
+        None,
+        Arc::new(UserIpTracker::new()),
+        beobachten.clone(),
+        false,
+    ));
+
+    client_side.write_all(b"C").await.unwrap();
+    sleep(Duration::from_millis(delayed_tail_ms)).await;
+
+    client_side
+        .write_all(b"ONNECT example.org:443 HTTP/1.1\r\nHost: example.org\r\n\r\n")
+        .await
+        .unwrap();
+    client_side.shutdown().await.unwrap();
+
+    let forwarded = tokio::time::timeout(Duration::from_secs(3), accept_task)
+        .await
+        .unwrap()
+        .unwrap();
+
+    let result = tokio::time::timeout(Duration::from_secs(3), handler)
+        .await
+        .unwrap()
+        .unwrap();
+    assert!(result.is_ok());
+
+    let snapshot = beobachten.snapshot_text(Duration::from_secs(60));
+    (forwarded, snapshot)
+}
+
+#[tokio::test]
+async fn tdd_pipeline_prefetch_5ms_misses_15ms_tail_and_classifies_as_port_scanner() {
+    let peer: SocketAddr = "198.51.100.171:58071".parse().unwrap();
+    let (forwarded, snapshot) = run_pipeline_prefetch_case(5, 15, peer).await;
+
+    assert!(
+        forwarded.starts_with(b"CONNECT"),
+        "mask backend must still receive full payload bytes in-order"
+    );
+    assert!(
+        snapshot.contains("[HTTP]") || snapshot.contains("[port-scanner]"),
+        "unexpected classifier snapshot for 5ms delayed-tail case: {snapshot}"
+    );
+}
+
+#[tokio::test]
+async fn tdd_pipeline_prefetch_20ms_recovers_15ms_tail_and_classifies_as_http() {
+    let peer: SocketAddr = "198.51.100.172:58072".parse().unwrap();
+    let (forwarded, snapshot) = run_pipeline_prefetch_case(20, 15, peer).await;
+
+    assert!(
+        forwarded.starts_with(b"CONNECT"),
+        "mask backend must receive full CONNECT payload"
+    );
+    assert!(
+        snapshot.contains("[HTTP]"),
+        "20ms budget should recover delayed fragmented prefix and classify as HTTP"
+    );
+}
+
+#[tokio::test]
+async fn matrix_pipeline_prefetch_budget_behavior_5_20_50ms() {
+    let peer5: SocketAddr = "198.51.100.173:58073".parse().unwrap();
+    let peer20: SocketAddr = "198.51.100.174:58074".parse().unwrap();
+    let peer50: SocketAddr = "198.51.100.175:58075".parse().unwrap();
+
+    let (_, snap5) = run_pipeline_prefetch_case(5, 35, peer5).await;
+    let (_, snap20) = run_pipeline_prefetch_case(20, 35, peer20).await;
+    let (_, snap50) = run_pipeline_prefetch_case(50, 35, peer50).await;
+
+    assert!(
+        snap5.contains("[HTTP]") || snap5.contains("[port-scanner]"),
+        "unexpected 5ms snapshot: {snap5}"
+    );
+    assert!(
+        snap20.contains("[HTTP]") || snap20.contains("[port-scanner]"),
+        "unexpected 20ms snapshot: {snap20}"
+    );
+    assert!(snap50.contains("[HTTP]"));
+}

src/proxy/tests/client_masking_prefetch_config_runtime_security_tests.rs

@@ -0,0 +1,82 @@
+use super::*;
+use tokio::io::{AsyncWriteExt, duplex};
+use tokio::time::{Duration, sleep};
+
+#[test]
+fn prefetch_timeout_budget_reads_from_config() {
+    let mut cfg = ProxyConfig::default();
+    assert_eq!(
+        mask_classifier_prefetch_timeout(&cfg),
+        Duration::from_millis(5),
+        "default prefetch timeout budget must remain 5ms"
+    );
+
+    cfg.censorship.mask_classifier_prefetch_timeout_ms = 20;
+    assert_eq!(
+        mask_classifier_prefetch_timeout(&cfg),
+        Duration::from_millis(20),
+        "runtime prefetch timeout budget must follow configured value"
+    );
+}
+
+#[tokio::test]
+async fn configured_prefetch_budget_20ms_recovers_tail_delayed_15ms() {
+    let (mut reader, mut writer) = duplex(1024);
+
+    let writer_task = tokio::spawn(async move {
+        sleep(Duration::from_millis(15)).await;
+        writer
+            .write_all(b"ONNECT example.org:443 HTTP/1.1\r\n")
+            .await
+            .expect("tail bytes must be writable");
+        writer.shutdown().await.expect("writer shutdown must succeed");
+    });
+
+    let mut initial_data = b"C".to_vec();
+    extend_masking_initial_window_with_timeout(
+        &mut reader,
+        &mut initial_data,
+        Duration::from_millis(20),
+    )
+    .await;
+
+    writer_task
+        .await
+        .expect("writer task must not panic in runtime timeout test");
+
+    assert!(
+        initial_data.starts_with(b"CONNECT"),
+        "20ms configured prefetch budget should recover 15ms delayed CONNECT tail"
+    );
+}
+
+#[tokio::test]
+async fn configured_prefetch_budget_5ms_misses_tail_delayed_15ms() {
+    let (mut reader, mut writer) = duplex(1024);
+
+    let writer_task = tokio::spawn(async move {
+        sleep(Duration::from_millis(15)).await;
+        writer
+            .write_all(b"ONNECT example.org:443 HTTP/1.1\r\n")
+            .await
+            .expect("tail bytes must be writable");
+        writer.shutdown().await.expect("writer shutdown must succeed");
+    });
+
+    let mut initial_data = b"C".to_vec();
+    extend_masking_initial_window_with_timeout(
+        &mut reader,
+        &mut initial_data,
+        Duration::from_millis(5),
+    )
+    .await;
+
+    writer_task
+        .await
+        .expect("writer task must not panic in runtime timeout test");
+
+    assert!(
+        !initial_data.starts_with(b"CONNECT"),
+        "5ms configured prefetch budget should miss 15ms delayed CONNECT tail"
+    );
+}

src/proxy/tests/client_masking_prefetch_invariant_security_tests.rs

@@ -0,0 +1,261 @@
+use super::*;
+use crate::config::{UpstreamConfig, UpstreamType};
+use crate::crypto::sha256_hmac;
+use crate::protocol::constants::{HANDSHAKE_LEN, TLS_VERSION};
+use crate::protocol::tls;
+use tokio::io::{AsyncReadExt, AsyncWriteExt, duplex};
+use tokio::net::TcpListener;
+
+struct PipelineHarness {
+    config: Arc<ProxyConfig>,
+    stats: Arc<Stats>,
+    upstream_manager: Arc<UpstreamManager>,
+    replay_checker: Arc<ReplayChecker>,
+    buffer_pool: Arc<BufferPool>,
+    rng: Arc<SecureRandom>,
+    route_runtime: Arc<RouteRuntimeController>,
+    ip_tracker: Arc<UserIpTracker>,
+    beobachten: Arc<BeobachtenStore>,
+}
+
+fn build_harness(secret_hex: &str, mask_port: u16) -> PipelineHarness {
+    let mut cfg = ProxyConfig::default();
+    cfg.general.beobachten = false;
+    cfg.censorship.mask = true;
+    cfg.censorship.mask_unix_sock = None;
+    cfg.censorship.mask_host = Some("127.0.0.1".to_string());
+    cfg.censorship.mask_port = mask_port;
+    cfg.censorship.mask_proxy_protocol = 0;
+    cfg.access.ignore_time_skew = true;
+    cfg.access
+        .users
+        .insert("user".to_string(), secret_hex.to_string());
+
+    let config = Arc::new(cfg);
+    let stats = Arc::new(Stats::new());
+    let upstream_manager = Arc::new(UpstreamManager::new(
+        vec![UpstreamConfig {
+            upstream_type: UpstreamType::Direct {
+                interface: None,
+                bind_addresses: None,
+            },
+            weight: 1,
+            enabled: true,
+            scopes: String::new(),
+            selected_scope: String::new(),
+        }],
+        1,
+        1,
+        1,
+        1,
+        false,
+        stats.clone(),
+    ));
+
+    PipelineHarness {
+        config,
+        stats,
+        upstream_manager,
+        replay_checker: Arc::new(ReplayChecker::new(256, Duration::from_secs(60))),
+        buffer_pool: Arc::new(BufferPool::new()),
+        rng: Arc::new(SecureRandom::new()),
+        route_runtime: Arc::new(RouteRuntimeController::new(RelayRouteMode::Direct)),
+        ip_tracker: Arc::new(UserIpTracker::new()),
+        beobachten: Arc::new(BeobachtenStore::new()),
+    }
+}
+
+fn make_valid_tls_client_hello(secret: &[u8], timestamp: u32, tls_len: usize, fill: u8) -> Vec<u8> {
+    let total_len = 5 + tls_len;
+    let mut handshake = vec![fill; total_len];
+
+    handshake[0] = 0x16;
+    handshake[1] = 0x03;
+    handshake[2] = 0x01;
+    handshake[3..5].copy_from_slice(&(tls_len as u16).to_be_bytes());
+
+    let session_id_len: usize = 32;
+    handshake[tls::TLS_DIGEST_POS + tls::TLS_DIGEST_LEN] = session_id_len as u8;
+
+    handshake[tls::TLS_DIGEST_POS..tls::TLS_DIGEST_POS + tls::TLS_DIGEST_LEN].fill(0);
+    let computed = sha256_hmac(secret, &handshake);
+    let mut digest = computed;
+    let ts = timestamp.to_le_bytes();
+    for i in 0..4 {
+        digest[28 + i] ^= ts[i];
+    }
+    handshake[tls::TLS_DIGEST_POS..tls::TLS_DIGEST_POS + tls::TLS_DIGEST_LEN]
+        .copy_from_slice(&digest);
+
+    handshake
+}
+
+fn wrap_tls_application_data(payload: &[u8]) -> Vec<u8> {
+    let mut record = Vec::with_capacity(5 + payload.len());
+    record.push(0x17);
+    record.extend_from_slice(&TLS_VERSION);
+    record.extend_from_slice(&(payload.len() as u16).to_be_bytes());
+    record.extend_from_slice(payload);
+    record
+}
+
+async fn read_and_discard_tls_record_body<T>(stream: &mut T, header: [u8; 5])
+where
+    T: tokio::io::AsyncRead + Unpin,
+{
+    let len = u16::from_be_bytes([header[3], header[4]]) as usize;
+    let mut body = vec![0u8; len];
+    stream.read_exact(&mut body).await.unwrap();
+}
+
+#[test]
+fn empty_initial_data_prefetch_gate_is_fail_closed() {
+    assert!(
+        !should_prefetch_mask_classifier_window(&[]),
+        "empty initial_data must not trigger classifier prefetch"
+    );
+}
+
+#[tokio::test]
+async fn blackhat_empty_initial_data_prefetch_must_not_consume_fallback_payload() {
+    let payload = b"\x17\x03\x03\x00\x10coalesced-tail-bytes".to_vec();
+    let (mut reader, mut writer) = duplex(1024);
+
+    writer.write_all(&payload).await.unwrap();
+    writer.shutdown().await.unwrap();
+
+    let mut initial_data = Vec::new();
+    extend_masking_initial_window(&mut reader, &mut initial_data).await;
+
+    assert!(
+        initial_data.is_empty(),
+        "empty initial_data must remain empty after prefetch stage"
+    );
+
+    let mut remaining = Vec::new();
+    reader.read_to_end(&mut remaining).await.unwrap();
+    assert_eq!(
+        remaining, payload,
+        "prefetch stage must not consume fallback payload when initial_data is empty"
+    );
+}
+
+#[tokio::test]
+async fn positive_fragmented_http_prefix_still_prefetches_within_window() {
+    let (mut reader, mut writer) = duplex(1024);
+    writer
+        .write_all(b"NECT example.org:443 HTTP/1.1\r\n")
+        .await
+        .unwrap();
+    writer.shutdown().await.unwrap();
+
+    let mut initial_data = b"CON".to_vec();
+    extend_masking_initial_window(&mut reader, &mut initial_data).await;
+
+    assert!(
+        initial_data.starts_with(b"CONNECT"),
+        "fragmented HTTP method prefix should still be recoverable by prefetch"
+    );
+    assert!(
+        initial_data.len() <= 16,
+        "prefetch window must remain bounded"
+    );
+}
+
+#[tokio::test]
+async fn light_fuzz_empty_initial_data_never_prefetches_any_bytes() {
+    let mut seed = 0xD15C_A11E_2026_0322u64;
+
+    for _ in 0..128 {
+        seed ^= seed << 7;
+        seed ^= seed >> 9;
+        seed ^= seed << 8;
+
+        let len = ((seed & 0x3f) as usize).saturating_add(1);
+        let mut payload = vec![0u8; len];
+        for (idx, byte) in payload.iter_mut().enumerate() {
+            *byte = (seed as u8).wrapping_add(idx as u8).wrapping_mul(17);
+        }
+
+        let (mut reader, mut writer) = duplex(1024);
+        writer.write_all(&payload).await.unwrap();
+        writer.shutdown().await.unwrap();
+
+        let mut initial_data = Vec::new();
+        extend_masking_initial_window(&mut reader, &mut initial_data).await;
+        assert!(initial_data.is_empty());
+
+        let mut remaining = Vec::new();
+        reader.read_to_end(&mut remaining).await.unwrap();
+        assert_eq!(remaining, payload);
+    }
+}
+
+#[tokio::test]
+async fn blackhat_integration_empty_initial_data_path_is_byte_exact_and_eof_clean() {
+    let listener = TcpListener::bind("127.0.0.1:0").await.unwrap();
+    let backend_addr = listener.local_addr().unwrap();
+
+    let secret = [0xD3u8; 16];
+    let client_hello = make_valid_tls_client_hello(&secret, 411, 600, 0x2B);
+    let mut invalid_payload = vec![0u8; HANDSHAKE_LEN];
+    invalid_payload[0] = 0xFF;
+    let invalid_mtproto_record = wrap_tls_application_data(&invalid_payload);
+    let trailing_record = wrap_tls_application_data(b"empty-prefetch-invariant");
+    let expected = trailing_record.clone();
+
+    let accept_task = tokio::spawn(async move {
+        let (mut stream, _) = listener.accept().await.unwrap();
+
+        let mut got = vec![0u8; expected.len()];
+        stream.read_exact(&mut got).await.unwrap();
+        assert_eq!(got, expected);
+
+        let mut one = [0u8; 1];
+        let n = stream.read(&mut one).await.unwrap();
+        assert_eq!(
+            n, 0,
+            "fallback stream must not append synthetic bytes on empty initial_data path"
+        );
+    });
+
+    let harness = build_harness("d3d3d3d3d3d3d3d3d3d3d3d3d3d3d3d3", backend_addr.port());
+    let (server_side, mut client_side) = duplex(131072);
+
+    let handler = tokio::spawn(handle_client_stream(
+        server_side,
+        "198.51.100.245:56145".parse().unwrap(),
+        harness.config,
+        harness.stats,
+        harness.upstream_manager,
+        harness.replay_checker,
+        harness.buffer_pool,
+        harness.rng,
+        None,
+        harness.route_runtime,
+        None,
+        harness.ip_tracker,
+        harness.beobachten,
+        false,
+    ));
+
+    client_side.write_all(&client_hello).await.unwrap();
+    let mut head = [0u8; 5];
+    client_side.read_exact(&mut head).await.unwrap();
+    assert_eq!(head[0], 0x16);
+    read_and_discard_tls_record_body(&mut client_side, head).await;
+
+    client_side.write_all(&invalid_mtproto_record).await.unwrap();
+    client_side.write_all(&trailing_record).await.unwrap();
+    client_side.shutdown().await.unwrap();
+
+    tokio::time::timeout(Duration::from_secs(3), accept_task)
+        .await
+        .unwrap()
+        .unwrap();
+
+    let _ = tokio::time::timeout(Duration::from_secs(3), handler)
+        .await
+        .unwrap()
+        .unwrap();
+}

src/proxy/tests/client_masking_prefetch_strict_boundary_security_tests.rs

@@ -0,0 +1,70 @@
+use super::*;
+use tokio::io::{AsyncWriteExt, duplex};
+use tokio::time::{Duration, advance, sleep};
+
+async fn run_strict_prefetch_case(prefetch_ms: u64, tail_delay_ms: u64) -> Vec<u8> {
+    let (mut reader, mut writer) = duplex(1024);
+
+    let writer_task = tokio::spawn(async move {
+        sleep(Duration::from_millis(tail_delay_ms)).await;
+        let _ = writer.write_all(b"ONNECT example.org:443 HTTP/1.1\r\n").await;
+        let _ = writer.shutdown().await;
+    });
+
+    let mut initial_data = b"C".to_vec();
+    let mut prefetch_task = tokio::spawn(async move {
+        extend_masking_initial_window_with_timeout(
+            &mut reader,
+            &mut initial_data,
+            Duration::from_millis(prefetch_ms),
+        )
+        .await;
+        initial_data
+    });
+
+    tokio::task::yield_now().await;
+
+    if tail_delay_ms > 0 {
+        advance(Duration::from_millis(tail_delay_ms)).await;
+        tokio::task::yield_now().await;
+    }
+
+    if prefetch_ms > tail_delay_ms {
+        advance(Duration::from_millis(prefetch_ms - tail_delay_ms)).await;
+        tokio::task::yield_now().await;
+    }
+
+    let result = prefetch_task.await.expect("prefetch task must not panic");
+    writer_task.await.expect("writer task must not panic");
+    result
+}
+
+#[tokio::test(start_paused = true)]
+async fn strict_prefetch_5ms_misses_15ms_tail() {
+    let got = run_strict_prefetch_case(5, 15).await;
+    assert_eq!(got, b"C".to_vec());
+}
+
+#[tokio::test(start_paused = true)]
+async fn strict_prefetch_20ms_recovers_15ms_tail() {
+    let got = run_strict_prefetch_case(20, 15).await;
+    assert!(got.starts_with(b"CONNECT"));
+}
+
+#[tokio::test(start_paused = true)]
+async fn strict_prefetch_50ms_recovers_35ms_tail() {
+    let got = run_strict_prefetch_case(50, 35).await;
+    assert!(got.starts_with(b"CONNECT"));
+}
+
+#[tokio::test(start_paused = true)]
+async fn strict_prefetch_equal_budget_and_delay_recovers_tail() {
+    let got = run_strict_prefetch_case(20, 20).await;
+    assert!(got.starts_with(b"CONNECT"));
+}
+
+#[tokio::test(start_paused = true)]
+async fn strict_prefetch_one_ms_after_budget_misses_tail() {
+    let got = run_strict_prefetch_case(20, 21).await;
+    assert_eq!(got, b"C".to_vec());
+}

src/proxy/tests/client_masking_prefetch_timing_matrix_security_tests.rs

@@ -0,0 +1,95 @@
+use super::*;
+use tokio::io::{AsyncRead, AsyncReadExt, AsyncWriteExt, duplex};
+use tokio::time::{Duration, sleep, timeout};
+
+async fn extend_masking_initial_window_with_budget<R>(
+    reader: &mut R,
+    initial_data: &mut Vec<u8>,
+    prefetch_timeout: Duration,
+) where
+    R: AsyncRead + Unpin,
+{
+    if !should_prefetch_mask_classifier_window(initial_data) {
+        return;
+    }
+
+    let need = 16usize.saturating_sub(initial_data.len());
+    if need == 0 {
+        return;
+    }
+
+    let mut extra = [0u8; 16];
+    if let Ok(Ok(n)) = timeout(prefetch_timeout, reader.read(&mut extra[..need])).await
+        && n > 0
+    {
+        initial_data.extend_from_slice(&extra[..n]);
+    }
+}
+
+async fn run_prefetch_budget_case(prefetch_budget_ms: u64, delayed_tail_ms: u64) -> bool {
+    let (mut reader, mut writer) = duplex(1024);
+
+    let writer_task = tokio::spawn(async move {
+        sleep(Duration::from_millis(delayed_tail_ms)).await;
+        writer
+            .write_all(b"ONNECT example.org:443 HTTP/1.1\r\n")
+            .await
+            .expect("tail bytes must be writable");
+        writer.shutdown().await.expect("writer shutdown must succeed");
+    });
+
+    let mut initial_data = b"C".to_vec();
+    extend_masking_initial_window_with_budget(
+        &mut reader,
+        &mut initial_data,
+        Duration::from_millis(prefetch_budget_ms),
+    )
+    .await;
+
+    writer_task
+        .await
+        .expect("writer task must not panic during matrix case");
+
+    initial_data.starts_with(b"CONNECT")
+}
+
+#[tokio::test]
+async fn adversarial_prefetch_budget_matrix_5_20_50ms_for_fragmented_connect_tail() {
+    let cases = [
+        // (tail-delay-ms, expected CONNECT recovery for budgets [5, 20, 50])
+        (2u64, [true, true, true]),
+        (15u64, [false, true, true]),
+        (35u64, [false, false, true]),
+    ];
+
+    for (tail_delay_ms, expected) in cases {
+        let got_5 = run_prefetch_budget_case(5, tail_delay_ms).await;
+        let got_20 = run_prefetch_budget_case(20, tail_delay_ms).await;
+        let got_50 = run_prefetch_budget_case(50, tail_delay_ms).await;
+
+        assert_eq!(
+            got_5, expected[0],
+            "5ms prefetch budget mismatch for tail delay {}ms",
+            tail_delay_ms
+        );
+        assert_eq!(
+            got_20, expected[1],
+            "20ms prefetch budget mismatch for tail delay {}ms",
+            tail_delay_ms
+        );
+        assert_eq!(
+            got_50, expected[2],
+            "50ms prefetch budget mismatch for tail delay {}ms",
+            tail_delay_ms
+        );
+    }
+}
+
+#[tokio::test]
+async fn control_current_runtime_prefetch_budget_is_5ms() {
+    assert_eq!(
+        MASK_CLASSIFIER_PREFETCH_TIMEOUT,
+        Duration::from_millis(5),
+        "matrix assumptions require current runtime prefetch budget to stay at 5ms"
+    );
+}

src/proxy/tests/client_masking_replay_timing_security_tests.rs

@@ -0,0 +1,161 @@
+use super::*;
+use crate::config::{UpstreamConfig, UpstreamType};
+use crate::crypto::sha256_hmac;
+use crate::protocol::constants::{HANDSHAKE_LEN, TLS_VERSION};
+use crate::protocol::tls;
+use std::sync::Arc;
+use tokio::io::{AsyncReadExt, AsyncWriteExt, duplex};
+use tokio::time::{Duration, Instant};
+
+fn new_upstream_manager(stats: Arc<Stats>) -> Arc<UpstreamManager> {
+    Arc::new(UpstreamManager::new(
+        vec![UpstreamConfig {
+            upstream_type: UpstreamType::Direct {
+                interface: None,
+                bind_addresses: None,
+            },
+            weight: 1,
+            enabled: true,
+            scopes: String::new(),
+            selected_scope: String::new(),
+        }],
+        1,
+        1,
+        1,
+        1,
+        false,
+        stats,
+    ))
+}
+
+fn make_valid_tls_client_hello(secret: &[u8], timestamp: u32, tls_len: usize, fill: u8) -> Vec<u8> {
+    let total_len = 5 + tls_len;
+    let mut handshake = vec![fill; total_len];
+
+    handshake[0] = 0x16;
+    handshake[1] = 0x03;
+    handshake[2] = 0x01;
+    handshake[3..5].copy_from_slice(&(tls_len as u16).to_be_bytes());
+
+    let session_id_len: usize = 32;
+    handshake[tls::TLS_DIGEST_POS + tls::TLS_DIGEST_LEN] = session_id_len as u8;
+
+    handshake[tls::TLS_DIGEST_POS..tls::TLS_DIGEST_POS + tls::TLS_DIGEST_LEN].fill(0);
+    let computed = sha256_hmac(secret, &handshake);
+    let mut digest = computed;
+    let ts = timestamp.to_le_bytes();
+    for i in 0..4 {
+        digest[28 + i] ^= ts[i];
+    }
+
+    handshake[tls::TLS_DIGEST_POS..tls::TLS_DIGEST_POS + tls::TLS_DIGEST_LEN]
+        .copy_from_slice(&digest);
+    handshake
+}
+
+async fn run_replay_candidate_session(
+    replay_checker: Arc<ReplayChecker>,
+    hello: &[u8],
+    peer: SocketAddr,
+    drive_mtproto_fail: bool,
+) -> Duration {
+    let mut cfg = ProxyConfig::default();
+    cfg.general.beobachten = false;
+    cfg.censorship.mask = true;
+    cfg.censorship.mask_unix_sock = None;
+    cfg.censorship.mask_host = Some("127.0.0.1".to_string());
+    cfg.censorship.mask_port = 1;
+    cfg.censorship.mask_timing_normalization_enabled = false;
+    cfg.access.ignore_time_skew = true;
+    cfg.access
+        .users
+        .insert("user".to_string(), "abababababababababababababababab".to_string());
+
+    let config = Arc::new(cfg);
+    let stats = Arc::new(Stats::new());
+    let beobachten = Arc::new(BeobachtenStore::new());
+
+    let (server_side, mut client_side) = duplex(65536);
+    let started = Instant::now();
+
+    let task = tokio::spawn(handle_client_stream(
+        server_side,
+        peer,
+        config,
+        stats.clone(),
+        new_upstream_manager(stats),
+        replay_checker,
+        Arc::new(BufferPool::new()),
+        Arc::new(SecureRandom::new()),
+        None,
+        Arc::new(RouteRuntimeController::new(RelayRouteMode::Direct)),
+        None,
+        Arc::new(UserIpTracker::new()),
+        beobachten,
+        false,
+    ));
+
+    client_side.write_all(hello).await.unwrap();
+
+    if drive_mtproto_fail {
+        let mut server_hello_head = [0u8; 5];
+        client_side.read_exact(&mut server_hello_head).await.unwrap();
+        assert_eq!(server_hello_head[0], 0x16);
+        let body_len = u16::from_be_bytes([server_hello_head[3], server_hello_head[4]]) as usize;
+        let mut body = vec![0u8; body_len];
+        client_side.read_exact(&mut body).await.unwrap();
+
+        let mut invalid_mtproto_record = Vec::with_capacity(5 + HANDSHAKE_LEN);
+        invalid_mtproto_record.push(0x17);
+        invalid_mtproto_record.extend_from_slice(&TLS_VERSION);
+        invalid_mtproto_record.extend_from_slice(&(HANDSHAKE_LEN as u16).to_be_bytes());
+        invalid_mtproto_record.extend_from_slice(&vec![0u8; HANDSHAKE_LEN]);
+        client_side.write_all(&invalid_mtproto_record).await.unwrap();
+        client_side
+            .write_all(b"GET /replay-fallback HTTP/1.1\r\nHost: x\r\n\r\n")
+            .await
+            .unwrap();
+    }
+
+    client_side.shutdown().await.unwrap();
+
+    let _ = tokio::time::timeout(Duration::from_secs(4), task)
+        .await
+        .unwrap()
+        .unwrap();
+
+    started.elapsed()
+}
+
+#[tokio::test]
+async fn replay_reject_still_honors_masking_timing_budget() {
+    let replay_checker = Arc::new(ReplayChecker::new(256, Duration::from_secs(60)));
+    let hello = make_valid_tls_client_hello(&[0xAB; 16], 7, 600, 0x51);
+
+    let seed_elapsed = run_replay_candidate_session(
+        Arc::clone(&replay_checker),
+        &hello,
+        "198.51.100.201:58001".parse().unwrap(),
+        true,
+    )
+    .await;
+
+    assert!(
+        seed_elapsed >= Duration::from_millis(40) && seed_elapsed < Duration::from_millis(250),
+        "seed replay-candidate run must honor masking timing budget without unbounded delay"
+    );
+
+    let replay_elapsed = run_replay_candidate_session(
+        Arc::clone(&replay_checker),
+        &hello,
+        "198.51.100.202:58002".parse().unwrap(),
+        false,
+    )
+    .await;
+
+    assert!(
+        replay_elapsed >= Duration::from_millis(40)
+            && replay_elapsed < Duration::from_millis(250),
+        "replay rejection path must still satisfy masking timing budget without unbounded DB/CPU delay"
+    );
+}

src/proxy/tests/client_more_advanced_tests.rs

@@ -0,0 +1,257 @@
+use super::*;
+use crate::config::ProxyConfig;
+use crate::stats::Stats;
+use crate::transport::UpstreamManager;
+use std::sync::Arc;
+use std::time::Duration;
+use tokio::io::{AsyncReadExt, AsyncWriteExt, duplex};
+
+#[tokio::test]
+async fn edge_mask_delay_bypassed_if_max_is_zero() {
+    let mut config = ProxyConfig::default();
+    config.censorship.server_hello_delay_min_ms = 10_000;
+    config.censorship.server_hello_delay_max_ms = 0;
+
+    let start = std::time::Instant::now();
+    maybe_apply_mask_reject_delay(&config).await;
+    assert!(start.elapsed() < Duration::from_millis(50));
+}
+
+#[test]
+fn edge_beobachten_ttl_clamps_exactly_to_24_hours() {
+    let mut config = ProxyConfig::default();
+    config.general.beobachten = true;
+    config.general.beobachten_minutes = 100_000;
+
+    let ttl = beobachten_ttl(&config);
+    assert_eq!(ttl.as_secs(), 24 * 60 * 60);
+}
+
+#[test]
+fn edge_wrap_tls_application_record_empty_payload() {
+    let wrapped = wrap_tls_application_record(&[]);
+    assert_eq!(wrapped.len(), 5);
+    assert_eq!(wrapped[0], TLS_RECORD_APPLICATION);
+    assert_eq!(&wrapped[3..5], &[0, 0]);
+}
+
+#[tokio::test]
+async fn boundary_user_data_quota_exact_match_rejects() {
+    let user = "quota-boundary-user";
+    let mut config = ProxyConfig::default();
+    config.access.user_data_quota.insert(user.to_string(), 1024);
+
+    let stats = Arc::new(Stats::new());
+    stats.add_user_octets_from(user, 1024);
+
+    let ip_tracker = Arc::new(UserIpTracker::new());
+    let peer = "198.51.100.10:55000".parse().unwrap();
+
+    let result = RunningClientHandler::acquire_user_connection_reservation_static(
+        user,
+        &config,
+        stats,
+        peer,
+        ip_tracker,
+    )
+    .await;
+
+    assert!(matches!(result, Err(ProxyError::DataQuotaExceeded { .. })));
+}
+
+#[tokio::test]
+async fn boundary_user_expiration_in_past_rejects() {
+    let user = "expired-boundary-user";
+    let mut config = ProxyConfig::default();
+    let expired_time = chrono::Utc::now() - chrono::Duration::milliseconds(1);
+    config
+        .access
+        .user_expirations
+        .insert(user.to_string(), expired_time);
+
+    let stats = Arc::new(Stats::new());
+    let ip_tracker = Arc::new(UserIpTracker::new());
+    let peer = "198.51.100.11:55000".parse().unwrap();
+
+    let result = RunningClientHandler::acquire_user_connection_reservation_static(
+        user,
+        &config,
+        stats,
+        peer,
+        ip_tracker,
+    )
+    .await;
+
+    assert!(matches!(result, Err(ProxyError::UserExpired { .. })));
+}
+
+#[tokio::test]
+async fn blackhat_proxy_protocol_massive_garbage_rejected_quickly() {
+    let mut cfg = ProxyConfig::default();
+    cfg.server.proxy_protocol_header_timeout_ms = 300;
+    let config = Arc::new(cfg);
+    let stats = Arc::new(Stats::new());
+
+    let (server_side, mut client_side) = duplex(4096);
+    let handler = tokio::spawn(handle_client_stream(
+        server_side,
+        "198.51.100.12:55000".parse().unwrap(),
+        config,
+        stats.clone(),
+        Arc::new(UpstreamManager::new(vec![], 1, 1, 1, 1, false, stats.clone())),
+        Arc::new(ReplayChecker::new(128, Duration::from_secs(60))),
+        Arc::new(BufferPool::new()),
+        Arc::new(SecureRandom::new()),
+        None,
+        Arc::new(RouteRuntimeController::new(RelayRouteMode::Direct)),
+        None,
+        Arc::new(UserIpTracker::new()),
+        Arc::new(BeobachtenStore::new()),
+        true,
+    ));
+
+    client_side.write_all(&vec![b'A'; 2000]).await.unwrap();
+
+    let result = tokio::time::timeout(Duration::from_secs(2), handler)
+        .await
+        .unwrap()
+        .unwrap();
+    assert!(matches!(result, Err(ProxyError::InvalidProxyProtocol)));
+    assert_eq!(stats.get_connects_bad(), 1);
+}
+
+#[tokio::test]
+async fn edge_tls_body_immediate_eof_triggers_masking_and_bad_connect() {
+    let mut cfg = ProxyConfig::default();
+    cfg.general.beobachten = true;
+    cfg.general.beobachten_minutes = 1;
+
+    let config = Arc::new(cfg);
+    let stats = Arc::new(Stats::new());
+    let beobachten = Arc::new(BeobachtenStore::new());
+
+    let (server_side, mut client_side) = duplex(4096);
+    let handler = tokio::spawn(handle_client_stream(
+        server_side,
+        "198.51.100.13:55000".parse().unwrap(),
+        config,
+        stats.clone(),
+        Arc::new(UpstreamManager::new(vec![], 1, 1, 1, 1, false, stats.clone())),
+        Arc::new(ReplayChecker::new(128, Duration::from_secs(60))),
+        Arc::new(BufferPool::new()),
+        Arc::new(SecureRandom::new()),
+        None,
+        Arc::new(RouteRuntimeController::new(RelayRouteMode::Direct)),
+        None,
+        Arc::new(UserIpTracker::new()),
+        beobachten.clone(),
+        false,
+    ));
+
+    client_side.write_all(&[0x16, 0x03, 0x01, 0x00, 100]).await.unwrap();
+    client_side.shutdown().await.unwrap();
+
+    let _ = tokio::time::timeout(Duration::from_secs(2), handler).await.unwrap();
+
+    assert_eq!(stats.get_connects_bad(), 1);
+}
+
+#[tokio::test]
+async fn security_classic_mode_disabled_masks_valid_length_payload() {
+    let mut cfg = ProxyConfig::default();
+    cfg.general.modes.classic = false;
+    cfg.general.modes.secure = false;
+    cfg.censorship.mask = true;
+
+    let config = Arc::new(cfg);
+    let stats = Arc::new(Stats::new());
+
+    let (server_side, mut client_side) = duplex(4096);
+    let handler = tokio::spawn(handle_client_stream(
+        server_side,
+        "198.51.100.15:55000".parse().unwrap(),
+        config,
+        stats.clone(),
+        Arc::new(UpstreamManager::new(vec![], 1, 1, 1, 1, false, stats.clone())),
+        Arc::new(ReplayChecker::new(128, Duration::from_secs(60))),
+        Arc::new(BufferPool::new()),
+        Arc::new(SecureRandom::new()),
+        None,
+        Arc::new(RouteRuntimeController::new(RelayRouteMode::Direct)),
+        None,
+        Arc::new(UserIpTracker::new()),
+        Arc::new(BeobachtenStore::new()),
+        false,
+    ));
+
+    client_side.write_all(&vec![0xEF; 64]).await.unwrap();
+    client_side.shutdown().await.unwrap();
+
+    let _ = tokio::time::timeout(Duration::from_secs(2), handler).await.unwrap();
+    assert_eq!(stats.get_connects_bad(), 1);
+}
+
+#[tokio::test]
+async fn concurrency_ip_tracker_strict_limit_one_rapid_churn() {
+    let user = "rapid-churn-user";
+    let mut config = ProxyConfig::default();
+    config.access.user_max_tcp_conns.insert(user.to_string(), 10);
+
+    let stats = Arc::new(Stats::new());
+    let ip_tracker = Arc::new(UserIpTracker::new());
+    ip_tracker.set_user_limit(user, 1).await;
+
+    let peer = "198.51.100.16:55000".parse().unwrap();
+
+    for _ in 0..500 {
+        let reservation = RunningClientHandler::acquire_user_connection_reservation_static(
+            user,
+            &config,
+            stats.clone(),
+            peer,
+            ip_tracker.clone(),
+        )
+        .await
+        .unwrap();
+        reservation.release().await;
+    }
+
+    assert_eq!(stats.get_user_curr_connects(user), 0);
+    assert_eq!(ip_tracker.get_active_ip_count(user).await, 0);
+}
+
+#[tokio::test]
+async fn quirk_read_with_progress_zero_length_buffer_returns_zero_immediately() {
+    let (mut server_side, _client_side) = duplex(4096);
+    let mut empty_buf = &mut [][..];
+
+    let result = tokio::time::timeout(
+        Duration::from_millis(50),
+        read_with_progress(&mut server_side, &mut empty_buf),
+    )
+    .await;
+
+    assert!(result.is_ok());
+    assert_eq!(result.unwrap().unwrap(), 0);
+}
+
+#[tokio::test]
+async fn stress_read_with_progress_cancellation_safety() {
+    let (mut server_side, mut client_side) = duplex(4096);
+
+    client_side.write_all(b"12345").await.unwrap();
+
+    let mut buf = [0u8; 10];
+    let result = tokio::time::timeout(
+        Duration::from_millis(50),
+        read_with_progress(&mut server_side, &mut buf),
+    )
+    .await;
+
+    assert!(result.is_err());
+
+    client_side.write_all(b"67890").await.unwrap();
+    let mut buf2 = [0u8; 5];
+    server_side.read_exact(&mut buf2).await.unwrap();
+    assert_eq!(&buf2, b"67890");
+}

src/proxy/tests/client_security_tests.rs

@@ -7,6 +7,9 @@ use crate::protocol::tls;
 use crate::proxy::handshake::HandshakeSuccess;
 use crate::stream::{CryptoReader, CryptoWriter};
 use crate::transport::proxy_protocol::ProxyProtocolV1Builder;
+use rand::rngs::StdRng;
+use rand::Rng;
+use rand::SeedableRng;
 use std::net::Ipv4Addr;
 use tokio::io::{AsyncReadExt, AsyncWriteExt, duplex};
 use tokio::net::{TcpListener, TcpStream};
@@ -25,6 +28,202 @@ fn synthetic_local_addr_uses_configured_port_for_max() {
     assert_eq!(addr.port(), u16::MAX);
 }
 
+#[test]
+fn handshake_timeout_with_mask_grace_includes_mask_margin() {
+    let mut config = ProxyConfig::default();
+    config.timeouts.client_handshake = 2;
+
+    config.censorship.mask = false;
+    assert_eq!(handshake_timeout_with_mask_grace(&config), Duration::from_secs(2));
+
+    config.censorship.mask = true;
+    assert_eq!(
+        handshake_timeout_with_mask_grace(&config),
+        Duration::from_millis(2750),
+        "mask mode extends handshake timeout by 750 ms"
+    );
+}
+
+#[tokio::test]
+async fn read_with_progress_reads_partial_buffers_before_eof() {
+    let data = vec![0xAA, 0xBB, 0xCC];
+    let mut reader = std::io::Cursor::new(data);
+    let mut buf = [0u8; 5];
+
+    let read = read_with_progress(&mut reader, &mut buf).await.unwrap();
+    assert_eq!(read, 3);
+    assert_eq!(&buf[..3], &[0xAA, 0xBB, 0xCC]);
+}
+
+#[test]
+fn is_trusted_proxy_source_respects_cidr_list_and_empty_rejects_all() {
+    let peer: IpAddr = "10.10.10.10".parse().unwrap();
+    assert!(!is_trusted_proxy_source(peer, &[]));
+
+    let trusted = vec!["10.0.0.0/8".parse().unwrap()];
+    assert!(is_trusted_proxy_source(peer, &trusted));
+
+    let not_trusted = vec!["192.0.2.0/24".parse().unwrap()];
+    assert!(!is_trusted_proxy_source(peer, &not_trusted));
+}
+
+#[test]
+fn is_trusted_proxy_source_accepts_cidr_zero_zero_as_global_cidr() {
+    let peer: IpAddr = "203.0.113.42".parse().unwrap();
+    let trust_all = vec!["0.0.0.0/0".parse().unwrap()];
+    assert!(is_trusted_proxy_source(peer, &trust_all));
+
+    let peer_v6: IpAddr = "2001:db8::1".parse().unwrap();
+    let trust_all_v6 = vec!["::/0".parse().unwrap()];
+    assert!(is_trusted_proxy_source(peer_v6, &trust_all_v6));
+}
+
+struct ErrorReader;
+
+impl tokio::io::AsyncRead for ErrorReader {
+    fn poll_read(
+        self: std::pin::Pin<&mut Self>,
+        _cx: &mut std::task::Context<'_>,
+        _buf: &mut tokio::io::ReadBuf<'_>,
+    ) -> std::task::Poll<std::io::Result<()>> {
+        std::task::Poll::Ready(Err(std::io::Error::new(std::io::ErrorKind::UnexpectedEof, "fake error")))
+    }
+}
+
+#[tokio::test]
+async fn read_with_progress_returns_error_from_failed_reader() {
+    let mut reader = ErrorReader;
+    let mut buf = [0u8; 8];
+    let err = read_with_progress(&mut reader, &mut buf).await.unwrap_err();
+    assert_eq!(err.kind(), std::io::ErrorKind::UnexpectedEof);
+}
+
+#[test]
+fn handshake_timeout_with_mask_grace_handles_maximum_values_without_overflow() {
+    let mut config = ProxyConfig::default();
+    config.timeouts.client_handshake = u64::MAX;
+    config.censorship.mask = true;
+
+    let timeout = handshake_timeout_with_mask_grace(&config);
+    assert!(timeout >= Duration::from_secs(u64::MAX));
+}
+
+#[tokio::test]
+async fn read_with_progress_zero_length_buffer_returns_zero() {
+    let data = vec![1, 2, 3];
+    let mut reader = std::io::Cursor::new(data);
+    let mut buf = [];
+
+    let read = read_with_progress(&mut reader, &mut buf).await.unwrap();
+    assert_eq!(read, 0);
+}
+
+#[test]
+fn handshake_timeout_without_mask_is_exact_base() {
+    let mut config = ProxyConfig::default();
+    config.timeouts.client_handshake = 7;
+    config.censorship.mask = false;
+
+    assert_eq!(handshake_timeout_with_mask_grace(&config), Duration::from_secs(7));
+}
+
+#[test]
+fn handshake_timeout_mask_enabled_adds_750ms() {
+    let mut config = ProxyConfig::default();
+    config.timeouts.client_handshake = 3;
+    config.censorship.mask = true;
+
+    assert_eq!(handshake_timeout_with_mask_grace(&config), Duration::from_millis(3750));
+}
+
+#[tokio::test]
+async fn read_with_progress_full_then_empty_transition() {
+    let data = vec![0x10, 0x20];
+    let mut cursor = std::io::Cursor::new(data);
+    let mut buf = [0u8; 2];
+
+    assert_eq!(read_with_progress(&mut cursor, &mut buf).await.unwrap(), 2);
+    assert_eq!(read_with_progress(&mut cursor, &mut buf).await.unwrap(), 0);
+}
+
+#[tokio::test]
+async fn read_with_progress_fragmented_io_works_over_multiple_calls() {
+    let mut cursor = std::io::Cursor::new(vec![1, 2, 3, 4, 5]);
+    let mut result = Vec::new();
+
+    for chunk_size in 1..=5 {
+        let mut b = vec![0u8; chunk_size];
+        let n = read_with_progress(&mut cursor, &mut b).await.unwrap();
+        result.extend_from_slice(&b[..n]);
+        if n == 0 { break; }
+    }
+
+    assert_eq!(result, vec![1,2,3,4,5]);
+}
+
+#[tokio::test]
+async fn read_with_progress_stress_randomized_chunk_sizes() {
+    for i in 0..128 {
+        let mut rng = StdRng::seed_from_u64(i as u64 + 1);
+        let mut input: Vec<u8> = (0..(i % 41)).map(|_| rng.next_u32() as u8).collect();
+        let mut cursor = std::io::Cursor::new(input.clone());
+        let mut collected = Vec::new();
+
+        while cursor.position() < cursor.get_ref().len() as u64 {
+            let chunk = 1 + (rng.next_u32() as usize % 8);
+            let mut b = vec![0u8; chunk];
+            let read = read_with_progress(&mut cursor, &mut b).await.unwrap();
+            collected.extend_from_slice(&b[..read]);
+            if read == 0 { break; }
+        }
+
+        assert_eq!(collected, input);
+    }
+}
+
+#[test]
+fn is_trusted_proxy_source_boundary_narrow_ipv4() {
+    let matching = "172.16.0.1".parse().unwrap();
+    let not_matching = "172.15.255.255".parse().unwrap();
+    let cidr = vec!["172.16.0.0/12".parse().unwrap()];
+    assert!(is_trusted_proxy_source(matching, &cidr));
+    assert!(!is_trusted_proxy_source(not_matching, &cidr));
+}
+
+#[test]
+fn is_trusted_proxy_source_rejects_out_of_family_ipv6_v4_cidr() {
+    let peer = "2001:db8::1".parse().unwrap();
+    let cidr = vec!["10.0.0.0/8".parse().unwrap()];
+    assert!(!is_trusted_proxy_source(peer, &cidr));
+}
+
+#[test]
+fn wrap_tls_application_record_reserved_chunks_look_reasonable() {
+    let payload = vec![0xAA; 1 + (u16::MAX as usize) + 2];
+    let wrapped = wrap_tls_application_record(&payload);
+    assert!(wrapped.len() > payload.len());
+    assert!(wrapped.contains(&0x17));
+}
+
+#[test]
+fn wrap_tls_application_record_roundtrip_size_check() {
+    let payload_len = 3000;
+    let payload = vec![0x55; payload_len];
+    let wrapped = wrap_tls_application_record(&payload);
+
+    let mut idx = 0;
+    let mut consumed = 0;
+    while idx + 5 <= wrapped.len() {
+        assert_eq!(wrapped[idx], 0x17);
+        let len = u16::from_be_bytes([wrapped[idx+3], wrapped[idx+4]]) as usize;
+        consumed += len;
+        idx += 5 + len;
+        if idx >= wrapped.len() { break; }
+    }
+
+    assert_eq!(consumed, payload_len);
+}
+
 fn make_crypto_reader<R>(reader: R) -> CryptoReader<R>
 where
     R: tokio::io::AsyncRead + Unpin,

src/proxy/tests/handshake_advanced_clever_tests.rs

@@ -0,0 +1,647 @@
+use super::*;
+use crate::crypto::{sha256, sha256_hmac, AesCtr};
+use crate::protocol::constants::{ProtoTag, RESERVED_NONCE_BEGINNINGS, RESERVED_NONCE_FIRST_BYTES};
+use std::net::{IpAddr, Ipv4Addr, Ipv6Addr, SocketAddr};
+use std::sync::Arc;
+use std::time::{Duration, Instant};
+
+// --- Helpers ---
+
+fn auth_probe_test_guard() -> std::sync::MutexGuard<'static, ()> {
+    auth_probe_test_lock()
+        .lock()
+        .unwrap_or_else(|poisoned| poisoned.into_inner())
+}
+
+fn test_config_with_secret_hex(secret_hex: &str) -> ProxyConfig {
+    let mut cfg = ProxyConfig::default();
+    cfg.access.users.clear();
+    cfg.access
+        .users
+        .insert("user".to_string(), secret_hex.to_string());
+    cfg.access.ignore_time_skew = true;
+    cfg.general.modes.secure = true;
+    cfg.general.modes.classic = true;
+    cfg.general.modes.tls = true;
+    cfg
+}
+
+fn make_valid_tls_handshake(secret: &[u8], timestamp: u32) -> Vec<u8> {
+    let session_id_len: usize = 32;
+    let len = tls::TLS_DIGEST_POS + tls::TLS_DIGEST_LEN + 1 + session_id_len;
+    let mut handshake = vec![0x42u8; len];
+
+    handshake[tls::TLS_DIGEST_POS + tls::TLS_DIGEST_LEN] = session_id_len as u8;
+    handshake[tls::TLS_DIGEST_POS..tls::TLS_DIGEST_POS + tls::TLS_DIGEST_LEN].fill(0);
+
+    let computed = sha256_hmac(secret, &handshake);
+    let mut digest = computed;
+    let ts = timestamp.to_le_bytes();
+    for i in 0..4 {
+        digest[28 + i] ^= ts[i];
+    }
+
+    handshake[tls::TLS_DIGEST_POS..tls::TLS_DIGEST_POS + tls::TLS_DIGEST_LEN]
+        .copy_from_slice(&digest);
+    handshake
+}
+
+fn make_valid_mtproto_handshake(
+    secret_hex: &str,
+    proto_tag: ProtoTag,
+    dc_idx: i16,
+) -> [u8; HANDSHAKE_LEN] {
+    let secret = hex::decode(secret_hex).expect("secret hex must decode");
+    let mut handshake = [0x5Au8; HANDSHAKE_LEN];
+    for (idx, b) in handshake[SKIP_LEN..SKIP_LEN + PREKEY_LEN + IV_LEN]
+        .iter_mut()
+        .enumerate()
+    {
+        *b = (idx as u8).wrapping_add(1);
+    }
+
+    let dec_prekey = &handshake[SKIP_LEN..SKIP_LEN + PREKEY_LEN];
+    let dec_iv_bytes = &handshake[SKIP_LEN + PREKEY_LEN..SKIP_LEN + PREKEY_LEN + IV_LEN];
+
+    let mut dec_key_input = Vec::with_capacity(PREKEY_LEN + secret.len());
+    dec_key_input.extend_from_slice(dec_prekey);
+    dec_key_input.extend_from_slice(&secret);
+    let dec_key = sha256(&dec_key_input);
+
+    let mut dec_iv_arr = [0u8; IV_LEN];
+    dec_iv_arr.copy_from_slice(dec_iv_bytes);
+    let dec_iv = u128::from_be_bytes(dec_iv_arr);
+
+    let mut stream = AesCtr::new(&dec_key, dec_iv);
+    let keystream = stream.encrypt(&[0u8; HANDSHAKE_LEN]);
+
+    let mut target_plain = [0u8; HANDSHAKE_LEN];
+    target_plain[PROTO_TAG_POS..PROTO_TAG_POS + 4].copy_from_slice(&proto_tag.to_bytes());
+    target_plain[DC_IDX_POS..DC_IDX_POS + 2].copy_from_slice(&dc_idx.to_le_bytes());
+
+    for idx in PROTO_TAG_POS..HANDSHAKE_LEN {
+        handshake[idx] = target_plain[idx] ^ keystream[idx];
+    }
+
+    handshake
+}
+
+fn make_valid_tls_client_hello_with_alpn(
+    secret: &[u8],
+    timestamp: u32,
+    alpn_protocols: &[&[u8]],
+) -> Vec<u8> {
+    let mut body = Vec::new();
+    body.extend_from_slice(&TLS_VERSION);
+    body.extend_from_slice(&[0u8; 32]);
+    body.push(32);
+    body.extend_from_slice(&[0x42u8; 32]);
+    body.extend_from_slice(&2u16.to_be_bytes());
+    body.extend_from_slice(&[0x13, 0x01]);
+    body.push(1);
+    body.push(0);
+
+    let mut ext_blob = Vec::new();
+    if !alpn_protocols.is_empty() {
+        let mut alpn_list = Vec::new();
+        for proto in alpn_protocols {
+            alpn_list.push(proto.len() as u8);
+            alpn_list.extend_from_slice(proto);
+        }
+        let mut alpn_data = Vec::new();
+        alpn_data.extend_from_slice(&(alpn_list.len() as u16).to_be_bytes());
+        alpn_data.extend_from_slice(&alpn_list);
+
+        ext_blob.extend_from_slice(&0x0010u16.to_be_bytes());
+        ext_blob.extend_from_slice(&(alpn_data.len() as u16).to_be_bytes());
+        ext_blob.extend_from_slice(&alpn_data);
+    }
+    body.extend_from_slice(&(ext_blob.len() as u16).to_be_bytes());
+    body.extend_from_slice(&ext_blob);
+
+    let mut handshake = Vec::new();
+    handshake.push(0x01);
+    let body_len = (body.len() as u32).to_be_bytes();
+    handshake.extend_from_slice(&body_len[1..4]);
+    handshake.extend_from_slice(&body);
+
+    let mut record = Vec::new();
+    record.push(TLS_RECORD_HANDSHAKE);
+    record.extend_from_slice(&[0x03, 0x01]);
+    record.extend_from_slice(&(handshake.len() as u16).to_be_bytes());
+    record.extend_from_slice(&handshake);
+
+    record[tls::TLS_DIGEST_POS..tls::TLS_DIGEST_POS + tls::TLS_DIGEST_LEN].fill(0);
+    let computed = sha256_hmac(secret, &record);
+    let mut digest = computed;
+    let ts = timestamp.to_le_bytes();
+    for i in 0..4 {
+        digest[28 + i] ^= ts[i];
+    }
+    record[tls::TLS_DIGEST_POS..tls::TLS_DIGEST_POS + tls::TLS_DIGEST_LEN].copy_from_slice(&digest);
+
+    record
+}
+
+// --- Category 1: Edge Cases & Protocol Boundaries ---
+
+#[tokio::test]
+async fn tls_minimum_viable_length_boundary() {
+    let _guard = auth_probe_test_guard();
+    clear_auth_probe_state_for_testing();
+
+    let secret = [0x11u8; 16];
+    let config = test_config_with_secret_hex("11111111111111111111111111111111");
+    let replay_checker = ReplayChecker::new(128, Duration::from_secs(60));
+    let rng = SecureRandom::new();
+    let peer: SocketAddr = "192.0.2.1:12345".parse().unwrap();
+
+    let min_len = tls::TLS_DIGEST_POS + tls::TLS_DIGEST_LEN + 1;
+    let mut exact_min_handshake = vec![0x42u8; min_len];
+    exact_min_handshake[min_len - 1] = 0;
+    exact_min_handshake[tls::TLS_DIGEST_POS..tls::TLS_DIGEST_POS + tls::TLS_DIGEST_LEN].fill(0);
+    let digest = sha256_hmac(&secret, &exact_min_handshake);
+    exact_min_handshake[tls::TLS_DIGEST_POS..tls::TLS_DIGEST_POS + tls::TLS_DIGEST_LEN]
+        .copy_from_slice(&digest);
+
+    let res = handle_tls_handshake(
+        &exact_min_handshake,
+        tokio::io::empty(),
+        tokio::io::sink(),
+        peer,
+        &config,
+        &replay_checker,
+        &rng,
+        None,
+    )
+    .await;
+    assert!(matches!(res, HandshakeResult::Success(_)), "Exact minimum length TLS handshake must succeed");
+
+    let short_handshake = vec![0x42u8; min_len - 1];
+    let res_short = handle_tls_handshake(
+        &short_handshake,
+        tokio::io::empty(),
+        tokio::io::sink(),
+        peer,
+        &config,
+        &replay_checker,
+        &rng,
+        None,
+    )
+    .await;
+    assert!(matches!(res_short, HandshakeResult::BadClient { .. }), "Handshake 1 byte shorter than minimum must fail closed");
+}
+
+#[tokio::test]
+async fn mtproto_extreme_dc_index_serialization() {
+    let _guard = auth_probe_test_guard();
+    clear_auth_probe_state_for_testing();
+
+    let secret_hex = "22222222222222222222222222222222";
+    let config = test_config_with_secret_hex(secret_hex);
+    for (idx, extreme_dc) in [i16::MIN, i16::MAX, -1, 0].into_iter().enumerate() {
+        // Keep replay state independent per case so we validate dc_idx encoding,
+        // not duplicate-handshake rejection behavior.
+        let replay_checker = ReplayChecker::new(128, Duration::from_secs(60));
+        let peer = SocketAddr::new(IpAddr::V4(Ipv4Addr::new(192, 0, 2, 2)), 12345 + idx as u16);
+        let handshake = make_valid_mtproto_handshake(secret_hex, ProtoTag::Secure, extreme_dc);
+        let res = handle_mtproto_handshake(
+            &handshake,
+            tokio::io::empty(),
+            tokio::io::sink(),
+            peer,
+            &config,
+            &replay_checker,
+            false,
+            None,
+        )
+        .await;
+
+        match res {
+            HandshakeResult::Success((_, _, success)) => {
+                assert_eq!(success.dc_idx, extreme_dc, "Extreme DC index {} must serialize/deserialize perfectly", extreme_dc);
+            }
+            _ => panic!("MTProto handshake with extreme DC index {} failed", extreme_dc),
+        }
+    }
+}
+
+#[tokio::test]
+async fn alpn_strict_case_and_padding_rejection() {
+    let _guard = auth_probe_test_guard();
+    clear_auth_probe_state_for_testing();
+
+    let secret = [0x33u8; 16];
+    let mut config = test_config_with_secret_hex("33333333333333333333333333333333");
+    config.censorship.alpn_enforce = true;
+    let replay_checker = ReplayChecker::new(128, Duration::from_secs(60));
+    let rng = SecureRandom::new();
+    let peer: SocketAddr = "192.0.2.3:12345".parse().unwrap();
+
+    let bad_alpns: &[&[u8]] = &[b"H2", b"h2\0", b" http/1.1", b"http/1.1\n"];
+
+    for bad_alpn in bad_alpns {
+        let handshake = make_valid_tls_client_hello_with_alpn(&secret, 0, &[*bad_alpn]);
+        let res = handle_tls_handshake(
+            &handshake,
+            tokio::io::empty(),
+            tokio::io::sink(),
+            peer,
+            &config,
+            &replay_checker,
+            &rng,
+            None,
+        )
+        .await;
+        assert!(matches!(res, HandshakeResult::BadClient { .. }), "ALPN strict enforcement must reject {:?}", bad_alpn);
+    }
+}
+
+#[test]
+fn ipv4_mapped_ipv6_bucketing_anomaly() {
+    let ipv4_mapped_1 = IpAddr::V6(Ipv6Addr::new(0, 0, 0, 0, 0, 0xffff, 0xc000, 0x0201));
+    let ipv4_mapped_2 = IpAddr::V6(Ipv6Addr::new(0, 0, 0, 0, 0, 0xffff, 0xc633, 0x6402));
+
+    let norm_1 = normalize_auth_probe_ip(ipv4_mapped_1);
+    let norm_2 = normalize_auth_probe_ip(ipv4_mapped_2);
+
+    assert_eq!(norm_1, norm_2, "IPv4-mapped IPv6 addresses must collapse into the same /64 bucket (::0)");
+    assert_eq!(norm_1, IpAddr::V6(Ipv6Addr::new(0, 0, 0, 0, 0, 0, 0, 0)), "The bucket must be exactly ::0");
+}
+
+// --- Category 2: Adversarial & Black Hat ---
+
+#[tokio::test]
+async fn mtproto_invalid_ciphertext_does_not_poison_replay_cache() {
+    let _guard = auth_probe_test_guard();
+    clear_auth_probe_state_for_testing();
+
+    let secret_hex = "55555555555555555555555555555555";
+    let config = test_config_with_secret_hex(secret_hex);
+    let replay_checker = ReplayChecker::new(128, Duration::from_secs(60));
+    let peer: SocketAddr = "192.0.2.5:12345".parse().unwrap();
+
+    let valid_handshake = make_valid_mtproto_handshake(secret_hex, ProtoTag::Secure, 1);
+    let mut invalid_handshake = valid_handshake;
+    invalid_handshake[SKIP_LEN + PREKEY_LEN + IV_LEN + 1] ^= 0xFF;
+
+    let res_invalid = handle_mtproto_handshake(
+        &invalid_handshake,
+        tokio::io::empty(),
+        tokio::io::sink(),
+        peer,
+        &config,
+        &replay_checker,
+        false,
+        None,
+    )
+    .await;
+    assert!(matches!(res_invalid, HandshakeResult::BadClient { .. }));
+
+    let res_valid = handle_mtproto_handshake(
+        &valid_handshake,
+        tokio::io::empty(),
+        tokio::io::sink(),
+        peer,
+        &config,
+        &replay_checker,
+        false,
+        None,
+    )
+    .await;
+    assert!(matches!(res_valid, HandshakeResult::Success(_)), "Invalid MTProto ciphertext must not poison the replay cache");
+}
+
+#[tokio::test]
+async fn tls_invalid_session_does_not_poison_replay_cache() {
+    let _guard = auth_probe_test_guard();
+    clear_auth_probe_state_for_testing();
+
+    let secret = [0x66u8; 16];
+    let config = test_config_with_secret_hex("66666666666666666666666666666666");
+    let replay_checker = ReplayChecker::new(128, Duration::from_secs(60));
+    let rng = SecureRandom::new();
+    let peer: SocketAddr = "192.0.2.6:12345".parse().unwrap();
+
+    let valid_handshake = make_valid_tls_handshake(&secret, 0);
+    let mut invalid_handshake = valid_handshake.clone();
+    let session_idx = tls::TLS_DIGEST_POS + tls::TLS_DIGEST_LEN + 1;
+    invalid_handshake[session_idx] ^= 0xFF;
+
+    let res_invalid = handle_tls_handshake(
+        &invalid_handshake,
+        tokio::io::empty(),
+        tokio::io::sink(),
+        peer,
+        &config,
+        &replay_checker,
+        &rng,
+        None,
+    )
+    .await;
+    assert!(matches!(res_invalid, HandshakeResult::BadClient { .. }));
+
+    let res_valid = handle_tls_handshake(
+        &valid_handshake,
+        tokio::io::empty(),
+        tokio::io::sink(),
+        peer,
+        &config,
+        &replay_checker,
+        &rng,
+        None,
+    )
+    .await;
+    assert!(matches!(res_valid, HandshakeResult::Success(_)), "Invalid TLS payload must not poison the replay cache");
+}
+
+#[tokio::test]
+async fn server_hello_delay_timing_neutrality_on_hmac_failure() {
+    let _guard = auth_probe_test_guard();
+    clear_auth_probe_state_for_testing();
+
+    let secret = [0x77u8; 16];
+    let mut config = test_config_with_secret_hex("77777777777777777777777777777777");
+    config.censorship.server_hello_delay_min_ms = 50;
+    config.censorship.server_hello_delay_max_ms = 50;
+
+    let replay_checker = ReplayChecker::new(128, Duration::from_secs(60));
+    let rng = SecureRandom::new();
+    let peer: SocketAddr = "192.0.2.7:12345".parse().unwrap();
+
+    let mut invalid_handshake = make_valid_tls_handshake(&secret, 0);
+    invalid_handshake[tls::TLS_DIGEST_POS] ^= 0xFF;
+
+    let start = Instant::now();
+    let res = handle_tls_handshake(
+        &invalid_handshake,
+        tokio::io::empty(),
+        tokio::io::sink(),
+        peer,
+        &config,
+        &replay_checker,
+        &rng,
+        None,
+    )
+    .await;
+    let elapsed = start.elapsed();
+
+    assert!(matches!(res, HandshakeResult::BadClient { .. }));
+    assert!(elapsed >= Duration::from_millis(45), "Invalid HMAC must still incur the configured ServerHello delay to prevent timing side-channels");
+}
+
+#[tokio::test]
+async fn server_hello_delay_inversion_resilience() {
+    let _guard = auth_probe_test_guard();
+    clear_auth_probe_state_for_testing();
+
+    let secret = [0x88u8; 16];
+    let mut config = test_config_with_secret_hex("88888888888888888888888888888888");
+    config.censorship.server_hello_delay_min_ms = 100;
+    config.censorship.server_hello_delay_max_ms = 10;
+
+    let replay_checker = ReplayChecker::new(128, Duration::from_secs(60));
+    let rng = SecureRandom::new();
+    let peer: SocketAddr = "192.0.2.8:12345".parse().unwrap();
+
+    let valid_handshake = make_valid_tls_handshake(&secret, 0);
+
+    let start = Instant::now();
+    let res = handle_tls_handshake(
+        &valid_handshake,
+        tokio::io::empty(),
+        tokio::io::sink(),
+        peer,
+        &config,
+        &replay_checker,
+        &rng,
+        None,
+    )
+    .await;
+    let elapsed = start.elapsed();
+
+    assert!(matches!(res, HandshakeResult::Success(_)));
+    assert!(elapsed >= Duration::from_millis(90), "Delay logic must gracefully handle min > max inversions via max.max(min)");
+}
+
+#[tokio::test]
+async fn mixed_valid_and_invalid_user_secrets_configuration() {
+    let _guard = auth_probe_test_guard();
+    clear_auth_probe_state_for_testing();
+    let _warn_guard = warned_secrets_test_lock().lock().unwrap();
+    clear_warned_secrets_for_testing();
+
+    let mut config = ProxyConfig::default();
+    config.access.ignore_time_skew = true;
+
+    for i in 0..9 {
+        let bad_secret = if i % 2 == 0 { "badhex!" } else { "1122" };
+        config.access.users.insert(format!("bad_user_{}", i), bad_secret.to_string());
+    }
+    let valid_secret_hex = "99999999999999999999999999999999";
+    config.access.users.insert("good_user".to_string(), valid_secret_hex.to_string());
+    config.general.modes.secure = true;
+    config.general.modes.classic = true;
+    config.general.modes.tls = true;
+
+    let secret = [0x99u8; 16];
+    let replay_checker = ReplayChecker::new(128, Duration::from_secs(60));
+    let rng = SecureRandom::new();
+    let peer: SocketAddr = "192.0.2.9:12345".parse().unwrap();
+
+    let valid_handshake = make_valid_tls_handshake(&secret, 0);
+
+    let res = handle_tls_handshake(
+        &valid_handshake,
+        tokio::io::empty(),
+        tokio::io::sink(),
+        peer,
+        &config,
+        &replay_checker,
+        &rng,
+        None,
+    )
+    .await;
+
+    assert!(matches!(res, HandshakeResult::Success(_)), "Proxy must gracefully skip invalid secrets and authenticate the valid one");
+}
+
+#[tokio::test]
+async fn tls_emulation_fallback_when_cache_missing() {
+    let _guard = auth_probe_test_guard();
+    clear_auth_probe_state_for_testing();
+
+    let secret = [0xAAu8; 16];
+    let mut config = test_config_with_secret_hex("aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa");
+    config.censorship.tls_emulation = true;
+    config.general.modes.tls = true;
+
+    let replay_checker = ReplayChecker::new(128, Duration::from_secs(60));
+    let rng = SecureRandom::new();
+    let peer: SocketAddr = "192.0.2.10:12345".parse().unwrap();
+
+    let valid_handshake = make_valid_tls_handshake(&secret, 0);
+
+    let res = handle_tls_handshake(
+        &valid_handshake,
+        tokio::io::empty(),
+        tokio::io::sink(),
+        peer,
+        &config,
+        &replay_checker,
+        &rng,
+        None,
+    )
+    .await;
+
+    assert!(matches!(res, HandshakeResult::Success(_)), "TLS emulation must gracefully fall back to standard ServerHello if cache is missing");
+}
+
+#[tokio::test]
+async fn classic_mode_over_tls_transport_protocol_confusion() {
+    let _guard = auth_probe_test_guard();
+    clear_auth_probe_state_for_testing();
+
+    let secret_hex = "bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb";
+    let mut config = test_config_with_secret_hex(secret_hex);
+    config.general.modes.classic = true;
+    config.general.modes.tls = true;
+
+    let replay_checker = ReplayChecker::new(128, Duration::from_secs(60));
+    let peer: SocketAddr = "192.0.2.11:12345".parse().unwrap();
+
+    let handshake = make_valid_mtproto_handshake(secret_hex, ProtoTag::Intermediate, 1);
+
+    let res = handle_mtproto_handshake(
+        &handshake,
+        tokio::io::empty(),
+        tokio::io::sink(),
+        peer,
+        &config,
+        &replay_checker,
+        true,
+        None,
+    )
+    .await;
+
+    assert!(matches!(res, HandshakeResult::Success(_)), "Intermediate tag over TLS must succeed if classic mode is enabled, locking in cross-transport behavior");
+}
+
+#[test]
+fn generate_tg_nonce_never_emits_reserved_bytes() {
+    let client_enc_key = [0xCCu8; 32];
+    let client_enc_iv = 123456789u128;
+    let rng = SecureRandom::new();
+
+    for _ in 0..10_000 {
+        let (nonce, _, _, _, _) = generate_tg_nonce(
+            ProtoTag::Secure,
+            1,
+            &client_enc_key,
+            client_enc_iv,
+            &rng,
+            false,
+        );
+
+        assert!(!RESERVED_NONCE_FIRST_BYTES.contains(&nonce[0]), "Nonce must never start with reserved bytes");
+        let first_four: [u8; 4] = [nonce[0], nonce[1], nonce[2], nonce[3]];
+        assert!(!RESERVED_NONCE_BEGINNINGS.contains(&first_four), "Nonce must never match reserved 4-byte beginnings");
+    }
+}
+
+#[tokio::test(flavor = "multi_thread", worker_threads = 4)]
+async fn dashmap_concurrent_saturation_stress() {
+    let _guard = auth_probe_test_guard();
+    clear_auth_probe_state_for_testing();
+
+    let ip_a: IpAddr = "192.0.2.13".parse().unwrap();
+    let ip_b: IpAddr = "198.51.100.13".parse().unwrap();
+    let mut tasks = Vec::new();
+
+    for i in 0..100 {
+        let target_ip = if i % 2 == 0 { ip_a } else { ip_b };
+        tasks.push(tokio::spawn(async move {
+            for _ in 0..50 {
+                auth_probe_record_failure(target_ip, Instant::now());
+            }
+        }));
+    }
+
+    for task in tasks {
+        task.await.expect("Task panicked during concurrent DashMap stress");
+    }
+
+    assert!(auth_probe_is_throttled_for_testing(ip_a), "IP A must be throttled after concurrent stress");
+    assert!(auth_probe_is_throttled_for_testing(ip_b), "IP B must be throttled after concurrent stress");
+}
+
+#[test]
+fn prototag_invalid_bytes_fail_closed() {
+    let invalid_tags: [[u8; 4]; 5] = [
+        [0, 0, 0, 0],
+        [0xFF, 0xFF, 0xFF, 0xFF],
+        [0xDE, 0xAD, 0xBE, 0xEF],
+        [0xDD, 0xDD, 0xDD, 0xDE],
+        [0x11, 0x22, 0x33, 0x44],
+    ];
+
+    for tag in invalid_tags {
+        assert_eq!(ProtoTag::from_bytes(tag), None, "Invalid ProtoTag bytes {:?} must fail closed", tag);
+    }
+}
+
+#[test]
+fn auth_probe_eviction_hash_collision_stress() {
+    let _guard = auth_probe_test_guard();
+    clear_auth_probe_state_for_testing();
+
+    let state = auth_probe_state_map();
+    let now = Instant::now();
+
+    for i in 0..10_000u32 {
+        let ip = IpAddr::V4(Ipv4Addr::new(10, 0, (i >> 8) as u8, (i & 0xFF) as u8));
+        auth_probe_record_failure_with_state(state, ip, now);
+    }
+
+    assert!(state.len() <= AUTH_PROBE_TRACK_MAX_ENTRIES, "Eviction logic must successfully bound the map size under heavy insertion stress");
+}
+
+#[test]
+fn encrypt_tg_nonce_with_ciphers_advances_counter_correctly() {
+    let client_enc_key = [0xDDu8; 32];
+    let client_enc_iv = 987654321u128;
+    let rng = SecureRandom::new();
+
+    let (nonce, _, _, _, _) = generate_tg_nonce(
+        ProtoTag::Secure,
+        2,
+        &client_enc_key,
+        client_enc_iv,
+        &rng,
+        false,
+    );
+
+    let (_, mut returned_encryptor, _) = encrypt_tg_nonce_with_ciphers(&nonce);
+    let zeros = [0u8; 64];
+    let returned_keystream = returned_encryptor.encrypt(&zeros);
+
+    let enc_key_iv = &nonce[SKIP_LEN..SKIP_LEN + KEY_LEN + IV_LEN];
+    let mut expected_enc_key = [0u8; 32];
+    expected_enc_key.copy_from_slice(&enc_key_iv[..KEY_LEN]);
+    let mut expected_enc_iv_arr = [0u8; IV_LEN];
+    expected_enc_iv_arr.copy_from_slice(&enc_key_iv[KEY_LEN..]);
+    let expected_enc_iv = u128::from_be_bytes(expected_enc_iv_arr);
+
+    let mut manual_encryptor = AesCtr::new(&expected_enc_key, expected_enc_iv);
+
+    let mut manual_input = Vec::new();
+    manual_input.extend_from_slice(&nonce);
+    manual_input.extend_from_slice(&zeros);
+    let manual_output = manual_encryptor.encrypt(&manual_input);
+
+    assert_eq!(
+        returned_keystream,
+        &manual_output[64..128],
+        "encrypt_tg_nonce_with_ciphers must correctly advance the AES-CTR counter by exactly the nonce length"
+    );
+}

src/proxy/tests/handshake_auth_probe_eviction_bias_security_tests.rs

@@ -0,0 +1,93 @@
+use super::*;
+use std::collections::HashSet;
+use std::net::{IpAddr, Ipv4Addr};
+use std::time::{Duration, Instant};
+
+fn auth_probe_test_guard() -> std::sync::MutexGuard<'static, ()> {
+    auth_probe_test_lock()
+        .lock()
+        .unwrap_or_else(|poisoned| poisoned.into_inner())
+}
+
+#[test]
+fn adversarial_large_state_offsets_escape_first_scan_window() {
+    let _guard = auth_probe_test_guard();
+    let base = Instant::now();
+    let state_len = 65_536usize;
+    let scan_limit = 1_024usize;
+
+    let mut saw_offset_outside_first_window = false;
+    for i in 0..8_192u64 {
+        let ip = IpAddr::V4(Ipv4Addr::new(
+            ((i >> 16) & 0xff) as u8,
+            ((i >> 8) & 0xff) as u8,
+            (i & 0xff) as u8,
+            ((i.wrapping_mul(131)) & 0xff) as u8,
+        ));
+        let now = base + Duration::from_nanos(i);
+        let start = auth_probe_scan_start_offset(ip, now, state_len, scan_limit);
+        if start >= scan_limit {
+            saw_offset_outside_first_window = true;
+            break;
+        }
+    }
+
+    assert!(
+        saw_offset_outside_first_window,
+        "scan start offset must cover the full auth-probe state, not only the first scan window"
+    );
+}
+
+#[test]
+fn stress_large_state_offsets_cover_many_scan_windows() {
+    let _guard = auth_probe_test_guard();
+    let base = Instant::now();
+    let state_len = 65_536usize;
+    let scan_limit = 1_024usize;
+
+    let mut covered_windows = HashSet::new();
+    for i in 0..16_384u64 {
+        let ip = IpAddr::V4(Ipv4Addr::new(
+            ((i >> 16) & 0xff) as u8,
+            ((i >> 8) & 0xff) as u8,
+            (i & 0xff) as u8,
+            ((i.wrapping_mul(17)) & 0xff) as u8,
+        ));
+        let now = base + Duration::from_micros(i);
+        let start = auth_probe_scan_start_offset(ip, now, state_len, scan_limit);
+        covered_windows.insert(start / scan_limit);
+    }
+
+    assert!(
+        covered_windows.len() >= 16,
+        "eviction scan must not collapse to a tiny hot zone; covered windows={} out of {}",
+        covered_windows.len(),
+        state_len / scan_limit
+    );
+}
+
+#[test]
+fn light_fuzz_offset_always_stays_inside_state_len() {
+    let _guard = auth_probe_test_guard();
+    let mut seed = 0xC0FF_EE12_3456_789Au64;
+    let base = Instant::now();
+
+    for _ in 0..8_192usize {
+        seed ^= seed << 7;
+        seed ^= seed >> 9;
+        seed ^= seed << 8;
+
+        let ip = IpAddr::V4(Ipv4Addr::new(
+            (seed >> 24) as u8,
+            (seed >> 16) as u8,
+            (seed >> 8) as u8,
+            seed as u8,
+        ));
+        let state_len = ((seed >> 16) as usize % 200_000).saturating_add(1);
+        let scan_limit = ((seed >> 40) as usize % 2_048).saturating_add(1);
+        let now = base + Duration::from_nanos(seed & 0x0fff);
+        let start = auth_probe_scan_start_offset(ip, now, state_len, scan_limit);
+
+        assert!(start < state_len, "scan offset must stay inside state length");
+    }
+}

src/proxy/tests/handshake_auth_probe_scan_budget_security_tests.rs

@@ -0,0 +1,99 @@
+use super::*;
+use std::net::{IpAddr, Ipv4Addr};
+use std::time::{Duration, Instant};
+
+fn auth_probe_test_guard() -> std::sync::MutexGuard<'static, ()> {
+    auth_probe_test_lock()
+        .lock()
+        .unwrap_or_else(|poisoned| poisoned.into_inner())
+}
+
+#[test]
+fn edge_zero_state_len_yields_zero_start_offset() {
+    let _guard = auth_probe_test_guard();
+    let ip = IpAddr::V4(Ipv4Addr::new(198, 51, 100, 44));
+    let now = Instant::now();
+
+    assert_eq!(
+        auth_probe_scan_start_offset(ip, now, 0, 16),
+        0,
+        "empty map must not produce non-zero scan offset"
+    );
+}
+
+#[test]
+fn adversarial_large_state_must_allow_start_offset_outside_scan_budget_window() {
+    let _guard = auth_probe_test_guard();
+    let base = Instant::now();
+    let scan_limit = 16usize;
+    let state_len = 65_536usize;
+
+    let mut saw_offset_outside_window = false;
+    for i in 0..2048u32 {
+        let ip = IpAddr::V4(Ipv4Addr::new(
+            203,
+            ((i >> 16) & 0xff) as u8,
+            ((i >> 8) & 0xff) as u8,
+            (i & 0xff) as u8,
+        ));
+        let now = base + Duration::from_micros(i as u64);
+        let start = auth_probe_scan_start_offset(ip, now, state_len, scan_limit);
+        assert!(
+            start < state_len,
+            "start offset must stay within state length; start={start}, len={state_len}"
+        );
+        if start >= scan_limit {
+            saw_offset_outside_window = true;
+            break;
+        }
+    }
+
+    assert!(
+        saw_offset_outside_window,
+        "large-state eviction must sample beyond the first scan window"
+    );
+}
+
+#[test]
+fn positive_state_smaller_than_scan_limit_caps_to_state_len() {
+    let _guard = auth_probe_test_guard();
+    let ip = IpAddr::V4(Ipv4Addr::new(192, 0, 2, 17));
+    let now = Instant::now();
+
+    for state_len in 1..32usize {
+        let start = auth_probe_scan_start_offset(ip, now, state_len, 64);
+        assert!(
+            start < state_len,
+            "start offset must never exceed state length when scan limit is larger"
+        );
+    }
+}
+
+#[test]
+fn light_fuzz_scan_offset_budget_never_exceeds_effective_window() {
+    let _guard = auth_probe_test_guard();
+    let mut seed = 0x5A41_5356_4C32_3236u64;
+    let base = Instant::now();
+
+    for _ in 0..4096 {
+        seed ^= seed << 7;
+        seed ^= seed >> 9;
+        seed ^= seed << 8;
+
+        let ip = IpAddr::V4(Ipv4Addr::new(
+            (seed >> 24) as u8,
+            (seed >> 16) as u8,
+            (seed >> 8) as u8,
+            seed as u8,
+        ));
+        let state_len = ((seed >> 8) as usize % 131_072).saturating_add(1);
+        let scan_limit = ((seed >> 32) as usize % 512).saturating_add(1);
+        let now = base + Duration::from_nanos(seed & 0xffff);
+        let start = auth_probe_scan_start_offset(ip, now, state_len, scan_limit);
+
+        assert!(
+            start < state_len,
+            "scan offset must stay inside state length"
+        );
+    }
+}

src/proxy/tests/handshake_auth_probe_scan_offset_stress_tests.rs

@@ -0,0 +1,116 @@
+use super::*;
+use std::collections::HashSet;
+use std::net::{IpAddr, Ipv4Addr};
+use std::time::{Duration, Instant};
+
+fn auth_probe_test_guard() -> std::sync::MutexGuard<'static, ()> {
+    auth_probe_test_lock()
+        .lock()
+        .unwrap_or_else(|poisoned| poisoned.into_inner())
+}
+
+#[test]
+fn positive_same_ip_moving_time_yields_diverse_scan_offsets() {
+    let _guard = auth_probe_test_guard();
+    let ip = IpAddr::V4(Ipv4Addr::new(198, 51, 100, 77));
+    let base = Instant::now();
+    let mut uniq = HashSet::new();
+
+    for i in 0..512u64 {
+        let now = base + Duration::from_nanos(i);
+        let offset = auth_probe_scan_start_offset(ip, now, 65_536, 16);
+        uniq.insert(offset);
+    }
+
+    assert!(
+        uniq.len() >= 256,
+        "offset randomization collapsed unexpectedly for same-ip moving-time samples (uniq={})",
+        uniq.len()
+    );
+}
+
+#[test]
+fn adversarial_many_ips_same_time_spreads_offsets_without_bias_collapse() {
+    let _guard = auth_probe_test_guard();
+    let now = Instant::now();
+    let mut uniq = HashSet::new();
+
+    for i in 0..1024u32 {
+        let ip = IpAddr::V4(Ipv4Addr::new(
+            (i >> 16) as u8,
+            (i >> 8) as u8,
+            i as u8,
+            (255 - (i as u8)),
+        ));
+        uniq.insert(auth_probe_scan_start_offset(ip, now, 65_536, 16));
+    }
+
+    assert!(
+        uniq.len() >= 512,
+        "scan offset distribution collapsed unexpectedly across adversarial peer set (uniq={})",
+        uniq.len()
+    );
+}
+
+#[tokio::test(flavor = "multi_thread", worker_threads = 4)]
+async fn stress_parallel_failure_churn_under_saturation_remains_capped_and_live() {
+    let _guard = auth_probe_test_guard();
+    clear_auth_probe_state_for_testing();
+
+    let start = Instant::now();
+    let mut workers = Vec::new();
+    for worker in 0..8u8 {
+        workers.push(tokio::spawn(async move {
+            for i in 0..8192u32 {
+                let ip = IpAddr::V4(Ipv4Addr::new(
+                    10,
+                    worker,
+                    ((i >> 8) & 0xff) as u8,
+                    (i & 0xff) as u8,
+                ));
+                auth_probe_record_failure(ip, start + Duration::from_micros((i % 128) as u64));
+            }
+        }));
+    }
+
+    for worker in workers {
+        worker.await.expect("saturation worker must not panic");
+    }
+
+    assert!(
+        auth_probe_state_map().len() <= AUTH_PROBE_TRACK_MAX_ENTRIES,
+        "state must remain hard-capped under parallel saturation churn"
+    );
+
+    let probe = IpAddr::V4(Ipv4Addr::new(10, 4, 1, 1));
+    let _ = auth_probe_should_apply_preauth_throttle(probe, start + Duration::from_millis(1));
+}
+
+#[test]
+fn light_fuzz_scan_offset_stays_within_window_for_randomized_inputs() {
+    let _guard = auth_probe_test_guard();
+    let mut seed = 0xA55A_1357_2468_9BDFu64;
+    let base = Instant::now();
+
+    for _ in 0..8192 {
+        seed ^= seed << 7;
+        seed ^= seed >> 9;
+        seed ^= seed << 8;
+
+        let ip = IpAddr::V4(Ipv4Addr::new(
+            (seed >> 24) as u8,
+            (seed >> 16) as u8,
+            (seed >> 8) as u8,
+            seed as u8,
+        ));
+        let state_len = ((seed >> 8) as usize % 200_000).saturating_add(1);
+        let scan_limit = ((seed >> 40) as usize % 1024).saturating_add(1);
+        let now = base + Duration::from_nanos(seed & 0x1fff);
+
+        let offset = auth_probe_scan_start_offset(ip, now, state_len, scan_limit);
+        assert!(
+            offset < state_len,
+            "scan offset must always remain inside state length"
+        );
+    }
+}

src/proxy/tests/handshake_key_material_zeroization_security_tests.rs

@@ -0,0 +1,42 @@
+use super::*;
+
+fn handshake_source() -> &'static str {
+    include_str!("../handshake.rs")
+}
+
+#[test]
+fn security_dec_key_derivation_is_zeroized_in_candidate_loop() {
+    let src = handshake_source();
+    assert!(
+        src.contains("let dec_key = Zeroizing::new(sha256(&dec_key_input));"),
+        "candidate-loop dec_key derivation must be wrapped in Zeroizing to clear secrets on early-continue paths"
+    );
+}
+
+#[test]
+fn security_enc_key_derivation_is_zeroized_in_candidate_loop() {
+    let src = handshake_source();
+    assert!(
+        src.contains("let enc_key = Zeroizing::new(sha256(&enc_key_input));"),
+        "candidate-loop enc_key derivation must be wrapped in Zeroizing to clear secrets on early-continue paths"
+    );
+}
+
+#[test]
+fn security_aes_ctr_initialization_uses_zeroizing_references() {
+    let src = handshake_source();
+    assert!(
+        src.contains("let mut decryptor = AesCtr::new(&dec_key, dec_iv);")
+            && src.contains("let encryptor = AesCtr::new(&enc_key, enc_iv);"),
+        "AES-CTR initialization must use Zeroizing key wrappers directly without creating extra plain key variables"
+    );
+}
+
+#[test]
+fn security_success_struct_copies_out_of_zeroizing_wrappers() {
+    let src = handshake_source();
+    assert!(
+        src.contains("dec_key: *dec_key,") && src.contains("enc_key: *enc_key,"),
+        "HandshakeSuccess construction must copy from Zeroizing wrappers so loop-local key material is dropped and zeroized"
+    );
+}

src/proxy/tests/handshake_more_clever_tests.rs

@@ -0,0 +1,614 @@
+use super::*;
+use crate::crypto::{sha256, sha256_hmac, AesCtr};
+use crate::protocol::constants::{ProtoTag, RESERVED_NONCE_BEGINNINGS, RESERVED_NONCE_FIRST_BYTES};
+use rand::{Rng, SeedableRng};
+use rand::rngs::StdRng;
+use std::collections::HashSet;
+use std::net::{IpAddr, Ipv4Addr, Ipv6Addr, SocketAddr};
+use std::sync::Arc;
+use std::time::{Duration, Instant};
+use tokio::sync::Barrier;
+
+// --- Helpers ---
+
+fn auth_probe_test_guard() -> std::sync::MutexGuard<'static, ()> {
+    auth_probe_test_lock()
+        .lock()
+        .unwrap_or_else(|poisoned| poisoned.into_inner())
+}
+
+fn test_config_with_secret_hex(secret_hex: &str) -> ProxyConfig {
+    let mut cfg = ProxyConfig::default();
+    cfg.access.users.clear();
+    cfg.access
+        .users
+        .insert("user".to_string(), secret_hex.to_string());
+    cfg.access.ignore_time_skew = true;
+    cfg.general.modes.secure = true;
+    cfg.general.modes.classic = true;
+    cfg.general.modes.tls = true;
+    cfg
+}
+
+fn make_valid_tls_handshake(secret: &[u8], timestamp: u32) -> Vec<u8> {
+    let session_id_len: usize = 32;
+    let len = tls::TLS_DIGEST_POS + tls::TLS_DIGEST_LEN + 1 + session_id_len;
+    let mut handshake = vec![0x42u8; len];
+
+    handshake[tls::TLS_DIGEST_POS + tls::TLS_DIGEST_LEN] = session_id_len as u8;
+    handshake[tls::TLS_DIGEST_POS..tls::TLS_DIGEST_POS + tls::TLS_DIGEST_LEN].fill(0);
+
+    let computed = sha256_hmac(secret, &handshake);
+    let mut digest = computed;
+    let ts = timestamp.to_le_bytes();
+    for i in 0..4 {
+        digest[28 + i] ^= ts[i];
+    }
+
+    handshake[tls::TLS_DIGEST_POS..tls::TLS_DIGEST_POS + tls::TLS_DIGEST_LEN]
+        .copy_from_slice(&digest);
+    handshake
+}
+
+fn make_valid_mtproto_handshake(
+    secret_hex: &str,
+    proto_tag: ProtoTag,
+    dc_idx: i16,
+) -> [u8; HANDSHAKE_LEN] {
+    let secret = hex::decode(secret_hex).expect("secret hex must decode");
+    let mut handshake = [0x5Au8; HANDSHAKE_LEN];
+    for (idx, b) in handshake[SKIP_LEN..SKIP_LEN + PREKEY_LEN + IV_LEN]
+        .iter_mut()
+        .enumerate()
+    {
+        *b = (idx as u8).wrapping_add(1);
+    }
+
+    let dec_prekey = &handshake[SKIP_LEN..SKIP_LEN + PREKEY_LEN];
+    let dec_iv_bytes = &handshake[SKIP_LEN + PREKEY_LEN..SKIP_LEN + PREKEY_LEN + IV_LEN];
+
+    let mut dec_key_input = Vec::with_capacity(PREKEY_LEN + secret.len());
+    dec_key_input.extend_from_slice(dec_prekey);
+    dec_key_input.extend_from_slice(&secret);
+    let dec_key = sha256(&dec_key_input);
+
+    let mut dec_iv_arr = [0u8; IV_LEN];
+    dec_iv_arr.copy_from_slice(dec_iv_bytes);
+    let dec_iv = u128::from_be_bytes(dec_iv_arr);
+
+    let mut stream = AesCtr::new(&dec_key, dec_iv);
+    let keystream = stream.encrypt(&[0u8; HANDSHAKE_LEN]);
+
+    let mut target_plain = [0u8; HANDSHAKE_LEN];
+    target_plain[PROTO_TAG_POS..PROTO_TAG_POS + 4].copy_from_slice(&proto_tag.to_bytes());
+    target_plain[DC_IDX_POS..DC_IDX_POS + 2].copy_from_slice(&dc_idx.to_le_bytes());
+
+    for idx in PROTO_TAG_POS..HANDSHAKE_LEN {
+        handshake[idx] = target_plain[idx] ^ keystream[idx];
+    }
+
+    handshake
+}
+
+fn make_valid_tls_client_hello_with_sni_and_alpn(
+    secret: &[u8],
+    timestamp: u32,
+    sni_host: &str,
+    alpn_protocols: &[&[u8]],
+) -> Vec<u8> {
+    let mut body = Vec::new();
+    body.extend_from_slice(&TLS_VERSION);
+    body.extend_from_slice(&[0u8; 32]);
+    body.push(32);
+    body.extend_from_slice(&[0x42u8; 32]);
+    body.extend_from_slice(&2u16.to_be_bytes());
+    body.extend_from_slice(&[0x13, 0x01]);
+    body.push(1);
+    body.push(0);
+
+    let mut ext_blob = Vec::new();
+
+    let host_bytes = sni_host.as_bytes();
+    let mut sni_payload = Vec::new();
+    sni_payload.extend_from_slice(&((host_bytes.len() + 3) as u16).to_be_bytes());
+    sni_payload.push(0);
+    sni_payload.extend_from_slice(&(host_bytes.len() as u16).to_be_bytes());
+    sni_payload.extend_from_slice(host_bytes);
+    ext_blob.extend_from_slice(&0x0000u16.to_be_bytes());
+    ext_blob.extend_from_slice(&(sni_payload.len() as u16).to_be_bytes());
+    ext_blob.extend_from_slice(&sni_payload);
+
+    if !alpn_protocols.is_empty() {
+        let mut alpn_list = Vec::new();
+        for proto in alpn_protocols {
+            alpn_list.push(proto.len() as u8);
+            alpn_list.extend_from_slice(proto);
+        }
+        let mut alpn_data = Vec::new();
+        alpn_data.extend_from_slice(&(alpn_list.len() as u16).to_be_bytes());
+        alpn_data.extend_from_slice(&alpn_list);
+
+        ext_blob.extend_from_slice(&0x0010u16.to_be_bytes());
+        ext_blob.extend_from_slice(&(alpn_data.len() as u16).to_be_bytes());
+        ext_blob.extend_from_slice(&alpn_data);
+    }
+
+    body.extend_from_slice(&(ext_blob.len() as u16).to_be_bytes());
+    body.extend_from_slice(&ext_blob);
+
+    let mut handshake = Vec::new();
+    handshake.push(0x01);
+    let body_len = (body.len() as u32).to_be_bytes();
+    handshake.extend_from_slice(&body_len[1..4]);
+    handshake.extend_from_slice(&body);
+
+    let mut record = Vec::new();
+    record.push(TLS_RECORD_HANDSHAKE);
+    record.extend_from_slice(&[0x03, 0x01]);
+    record.extend_from_slice(&(handshake.len() as u16).to_be_bytes());
+    record.extend_from_slice(&handshake);
+
+    record[tls::TLS_DIGEST_POS..tls::TLS_DIGEST_POS + tls::TLS_DIGEST_LEN].fill(0);
+    let computed = sha256_hmac(secret, &record);
+    let mut digest = computed;
+    let ts = timestamp.to_le_bytes();
+    for i in 0..4 {
+        digest[28 + i] ^= ts[i];
+    }
+    record[tls::TLS_DIGEST_POS..tls::TLS_DIGEST_POS + tls::TLS_DIGEST_LEN].copy_from_slice(&digest);
+
+    record
+}
+
+// --- Category 1: Timing & Delay Invariants ---
+
+#[tokio::test]
+async fn server_hello_delay_bypassed_if_max_is_zero_despite_high_min() {
+    let _guard = auth_probe_test_guard();
+    clear_auth_probe_state_for_testing();
+
+    let secret = [0x1Au8; 16];
+    let mut config = test_config_with_secret_hex("1a1a1a1a1a1a1a1a1a1a1a1a1a1a1a1a");
+    config.censorship.server_hello_delay_min_ms = 5000;
+    config.censorship.server_hello_delay_max_ms = 0;
+
+    let replay_checker = ReplayChecker::new(128, Duration::from_secs(60));
+    let rng = SecureRandom::new();
+    let peer: SocketAddr = "192.0.2.101:12345".parse().unwrap();
+
+    let mut invalid_handshake = make_valid_tls_handshake(&secret, 0);
+    invalid_handshake[tls::TLS_DIGEST_POS] ^= 0xFF;
+
+    let fut = handle_tls_handshake(
+        &invalid_handshake,
+        tokio::io::empty(),
+        tokio::io::sink(),
+        peer,
+        &config,
+        &replay_checker,
+        &rng,
+        None,
+    );
+
+    // Deterministic assertion: with max_ms == 0 there must be no sleep path,
+    // so the handshake should complete promptly under a generous timeout budget.
+    let res = tokio::time::timeout(Duration::from_millis(250), fut)
+        .await
+        .expect("max_ms=0 should bypass artificial delay and complete quickly");
+
+    assert!(matches!(res, HandshakeResult::BadClient { .. }));
+}
+
+#[test]
+fn auth_probe_backoff_extreme_fail_streak_clamps_safely() {
+    let _guard = auth_probe_test_guard();
+    clear_auth_probe_state_for_testing();
+
+    let state = auth_probe_state_map();
+    let peer_ip = IpAddr::V4(Ipv4Addr::new(198, 51, 100, 99));
+    let now = Instant::now();
+
+    state.insert(
+        peer_ip,
+        AuthProbeState {
+            fail_streak: u32::MAX - 1,
+            blocked_until: now,
+            last_seen: now,
+        },
+    );
+
+    auth_probe_record_failure_with_state(&state, peer_ip, now);
+
+    let updated = state.get(&peer_ip).unwrap();
+    assert_eq!(updated.fail_streak, u32::MAX);
+
+    let expected_blocked_until = now + Duration::from_millis(AUTH_PROBE_BACKOFF_MAX_MS);
+    assert_eq!(updated.blocked_until, expected_blocked_until, "Extreme fail streak must clamp cleanly to AUTH_PROBE_BACKOFF_MAX_MS");
+}
+
+#[test]
+fn generate_tg_nonce_cryptographic_uniqueness_and_entropy() {
+    let client_enc_key = [0x2Bu8; 32];
+    let client_enc_iv = 1337u128;
+    let rng = SecureRandom::new();
+
+    let mut nonces = HashSet::new();
+    let mut total_set_bits = 0usize;
+    let iterations = 5_000;
+
+    for _ in 0..iterations {
+        let (nonce, _, _, _, _) = generate_tg_nonce(
+            ProtoTag::Secure,
+            2,
+            &client_enc_key,
+            client_enc_iv,
+            &rng,
+            false,
+        );
+
+        for byte in nonce.iter() {
+            total_set_bits += byte.count_ones() as usize;
+        }
+
+        assert!(nonces.insert(nonce), "generate_tg_nonce emitted a duplicate nonce! RNG is stuck.");
+    }
+
+    let total_bits = iterations * HANDSHAKE_LEN * 8;
+    let ratio = (total_set_bits as f64) / (total_bits as f64);
+    assert!(ratio > 0.48 && ratio < 0.52, "Nonce entropy is degraded. Set bit ratio: {}", ratio);
+}
+
+#[tokio::test]
+async fn mtproto_multi_user_decryption_isolation() {
+    let _guard = auth_probe_test_guard();
+    clear_auth_probe_state_for_testing();
+
+    let mut config = ProxyConfig::default();
+    config.general.modes.secure = true;
+    config.access.ignore_time_skew = true;
+
+    config.access.users.insert("user_a".to_string(), "11111111111111111111111111111111".to_string());
+    config.access.users.insert("user_b".to_string(), "22222222222222222222222222222222".to_string());
+    let good_secret_hex = "33333333333333333333333333333333";
+    config.access.users.insert("user_c".to_string(), good_secret_hex.to_string());
+
+    let replay_checker = ReplayChecker::new(128, Duration::from_secs(60));
+    let peer: SocketAddr = "192.0.2.104:12345".parse().unwrap();
+
+    let valid_handshake = make_valid_mtproto_handshake(good_secret_hex, ProtoTag::Secure, 1);
+
+    let res = handle_mtproto_handshake(
+        &valid_handshake,
+        tokio::io::empty(),
+        tokio::io::sink(),
+        peer,
+        &config,
+        &replay_checker,
+        false,
+        None,
+    )
+    .await;
+
+    match res {
+        HandshakeResult::Success((_, _, success)) => {
+            assert_eq!(success.user, "user_c", "Decryption attempts on previous users must not corrupt the handshake buffer for the valid user");
+        }
+        _ => panic!("Multi-user MTProto handshake failed. Decryption buffer might be mutating in place."),
+    }
+}
+
+#[tokio::test(flavor = "multi_thread", worker_threads = 4)]
+async fn invalid_secret_warning_lock_contention_and_bound() {
+    let _guard = warned_secrets_test_lock()
+        .lock()
+        .unwrap_or_else(|poisoned| poisoned.into_inner());
+    clear_warned_secrets_for_testing();
+
+    let tasks = 50;
+    let iterations_per_task = 100;
+    let barrier = Arc::new(Barrier::new(tasks));
+    let mut handles = Vec::new();
+
+    for t in 0..tasks {
+        let b = barrier.clone();
+        handles.push(tokio::spawn(async move {
+            b.wait().await;
+            for i in 0..iterations_per_task {
+                let user_name = format!("contention_user_{}_{}", t, i);
+                warn_invalid_secret_once(&user_name, "invalid_hex", ACCESS_SECRET_BYTES, None);
+            }
+        }));
+    }
+
+    for handle in handles {
+        handle.await.unwrap();
+    }
+
+    let warned = INVALID_SECRET_WARNED.get().unwrap();
+    let guard = warned.lock().unwrap_or_else(|poisoned| poisoned.into_inner());
+
+    assert_eq!(
+        guard.len(),
+        WARNED_SECRET_MAX_ENTRIES,
+        "Concurrent spam of invalid secrets must strictly bound the HashSet memory to WARNED_SECRET_MAX_ENTRIES"
+    );
+}
+
+#[tokio::test(flavor = "multi_thread", worker_threads = 4)]
+async fn mtproto_strict_concurrent_replay_race_condition() {
+    let _guard = auth_probe_test_guard();
+    clear_auth_probe_state_for_testing();
+
+    let secret_hex = "4A4A4A4A4A4A4A4A4A4A4A4A4A4A4A4A";
+    let config = Arc::new(test_config_with_secret_hex(secret_hex));
+    let replay_checker = Arc::new(ReplayChecker::new(4096, Duration::from_secs(60)));
+    let valid_handshake = Arc::new(make_valid_mtproto_handshake(secret_hex, ProtoTag::Secure, 1));
+
+    let tasks = 100;
+    let barrier = Arc::new(Barrier::new(tasks));
+    let mut handles = Vec::new();
+
+    for i in 0..tasks {
+        let b = barrier.clone();
+        let cfg = config.clone();
+        let rc = replay_checker.clone();
+        let hs = valid_handshake.clone();
+
+        handles.push(tokio::spawn(async move {
+            let peer = SocketAddr::new(IpAddr::V4(Ipv4Addr::new(10, 0, 0, (i % 250) as u8)), 10000 + i as u16);
+            b.wait().await;
+            handle_mtproto_handshake(
+                &hs,
+                tokio::io::empty(),
+                tokio::io::sink(),
+                peer,
+                &cfg,
+                &rc,
+                false,
+                None,
+            )
+            .await
+        }));
+    }
+
+    let mut successes = 0;
+    let mut failures = 0;
+
+    for handle in handles {
+        match handle.await.unwrap() {
+            HandshakeResult::Success(_) => successes += 1,
+            HandshakeResult::BadClient { .. } => failures += 1,
+            _ => panic!("Unexpected error result in concurrent MTProto replay test"),
+        }
+    }
+
+    assert_eq!(successes, 1, "Replay cache race condition allowed multiple identical MTProto handshakes to succeed");
+    assert_eq!(failures, tasks - 1, "Replay cache failed to forcefully reject concurrent duplicates");
+}
+
+#[tokio::test]
+async fn tls_alpn_zero_length_protocol_handled_safely() {
+    let _guard = auth_probe_test_guard();
+    clear_auth_probe_state_for_testing();
+
+    let secret = [0x5Bu8; 16];
+    let mut config = test_config_with_secret_hex("5b5b5b5b5b5b5b5b5b5b5b5b5b5b5b5b");
+    config.censorship.alpn_enforce = true;
+    let replay_checker = ReplayChecker::new(128, Duration::from_secs(60));
+    let rng = SecureRandom::new();
+    let peer: SocketAddr = "192.0.2.107:12345".parse().unwrap();
+
+    let handshake = make_valid_tls_client_hello_with_sni_and_alpn(&secret, 0, "example.com", &[b""]);
+
+    let res = handle_tls_handshake(
+        &handshake,
+        tokio::io::empty(),
+        tokio::io::sink(),
+        peer,
+        &config,
+        &replay_checker,
+        &rng,
+        None,
+    )
+    .await;
+
+    assert!(matches!(res, HandshakeResult::BadClient { .. }), "0-length ALPN must be safely rejected without panicking");
+}
+
+#[tokio::test]
+async fn tls_sni_massive_hostname_does_not_panic() {
+    let _guard = auth_probe_test_guard();
+    clear_auth_probe_state_for_testing();
+
+    let secret = [0x6Cu8; 16];
+    let config = test_config_with_secret_hex("6c6c6c6c6c6c6c6c6c6c6c6c6c6c6c6c");
+    let replay_checker = ReplayChecker::new(128, Duration::from_secs(60));
+    let rng = SecureRandom::new();
+    let peer: SocketAddr = "192.0.2.108:12345".parse().unwrap();
+
+    let massive_hostname = String::from_utf8(vec![b'a'; 65000]).unwrap();
+    let handshake = make_valid_tls_client_hello_with_sni_and_alpn(&secret, 0, &massive_hostname, &[]);
+
+    let res = handle_tls_handshake(
+        &handshake,
+        tokio::io::empty(),
+        tokio::io::sink(),
+        peer,
+        &config,
+        &replay_checker,
+        &rng,
+        None,
+    )
+    .await;
+
+    assert!(matches!(res, HandshakeResult::Success(_) | HandshakeResult::BadClient { .. }), "Massive SNI hostname must be processed or ignored without stack overflow or panic");
+}
+
+#[tokio::test]
+async fn tls_progressive_truncation_fuzzing_no_panics() {
+    let _guard = auth_probe_test_guard();
+    clear_auth_probe_state_for_testing();
+
+    let secret = [0x7Du8; 16];
+    let config = test_config_with_secret_hex("7d7d7d7d7d7d7d7d7d7d7d7d7d7d7d7d");
+    let replay_checker = ReplayChecker::new(128, Duration::from_secs(60));
+    let rng = SecureRandom::new();
+    let peer: SocketAddr = "192.0.2.109:12345".parse().unwrap();
+
+    let valid_handshake = make_valid_tls_client_hello_with_sni_and_alpn(&secret, 0, "example.com", &[b"h2"]);
+    let full_len = valid_handshake.len();
+
+    // Truncated corpus only: full_len is a valid baseline and should not be
+    // asserted as BadClient in a truncation-specific test.
+    for i in (0..full_len).rev() {
+        let truncated = &valid_handshake[..i];
+        let res = handle_tls_handshake(
+            truncated,
+            tokio::io::empty(),
+            tokio::io::sink(),
+            peer,
+            &config,
+            &replay_checker,
+            &rng,
+            None,
+        )
+        .await;
+        assert!(matches!(res, HandshakeResult::BadClient { .. }), "Truncated TLS handshake at len {} must fail safely without panicking", i);
+    }
+}
+
+#[tokio::test]
+async fn mtproto_pure_entropy_fuzzing_no_panics() {
+    let _guard = auth_probe_test_guard();
+    clear_auth_probe_state_for_testing();
+
+    let config = test_config_with_secret_hex("8e8e8e8e8e8e8e8e8e8e8e8e8e8e8e8e");
+    let replay_checker = ReplayChecker::new(128, Duration::from_secs(60));
+    let peer: SocketAddr = "192.0.2.110:12345".parse().unwrap();
+
+    let mut seeded = StdRng::seed_from_u64(0xDEADBEEFCAFE);
+
+    for _ in 0..10_000 {
+        let mut noise = [0u8; HANDSHAKE_LEN];
+        seeded.fill_bytes(&mut noise);
+
+        let res = handle_mtproto_handshake(
+            &noise,
+            tokio::io::empty(),
+            tokio::io::sink(),
+            peer,
+            &config,
+            &replay_checker,
+            false,
+            None,
+        )
+        .await;
+
+        assert!(matches!(res, HandshakeResult::BadClient { .. }), "Pure entropy MTProto payload must fail closed and never panic");
+    }
+}
+
+#[test]
+fn decode_user_secret_odd_length_hex_rejection() {
+    let _guard = warned_secrets_test_lock()
+        .lock()
+        .unwrap_or_else(|poisoned| poisoned.into_inner());
+    clear_warned_secrets_for_testing();
+
+    let mut config = ProxyConfig::default();
+    config.access.users.clear();
+    config.access.users.insert("odd_user".to_string(), "1234567890123456789012345678901".to_string());
+
+    let decoded = decode_user_secrets(&config, None);
+    assert!(decoded.is_empty(), "Odd-length hex string must be gracefully rejected by hex::decode without unwrapping");
+}
+
+#[test]
+fn saturation_grace_pre_existing_high_fail_streak_immediate_throttle() {
+    let _guard = auth_probe_test_guard();
+    clear_auth_probe_state_for_testing();
+
+    let state = auth_probe_state_map();
+    let peer_ip = IpAddr::V4(Ipv4Addr::new(198, 51, 100, 112));
+    let now = Instant::now();
+
+    let extreme_streak = AUTH_PROBE_BACKOFF_START_FAILS + AUTH_PROBE_SATURATION_GRACE_FAILS + 5;
+    state.insert(
+        peer_ip,
+        AuthProbeState {
+            fail_streak: extreme_streak,
+            blocked_until: now + Duration::from_secs(5),
+            last_seen: now,
+        },
+    );
+
+    {
+        let mut guard = auth_probe_saturation_state_lock();
+        *guard = Some(AuthProbeSaturationState {
+            fail_streak: AUTH_PROBE_BACKOFF_START_FAILS,
+            blocked_until: now + Duration::from_secs(5),
+            last_seen: now,
+        });
+    }
+
+    let is_throttled = auth_probe_should_apply_preauth_throttle(peer_ip, now);
+    assert!(is_throttled, "A peer with a pre-existing high fail streak must be immediately throttled when saturation begins, receiving no unearned grace period");
+}
+
+#[test]
+fn auth_probe_saturation_note_resets_retention_window() {
+    let _guard = auth_probe_test_guard();
+    clear_auth_probe_state_for_testing();
+
+    let base_time = Instant::now();
+
+    auth_probe_note_saturation(base_time);
+    let later = base_time + Duration::from_secs(AUTH_PROBE_TRACK_RETENTION_SECS - 1);
+    auth_probe_note_saturation(later);
+
+    let check_time = base_time + Duration::from_secs(AUTH_PROBE_TRACK_RETENTION_SECS + 5);
+
+    // This call may return false if backoff has elapsed, but it must not clear
+    // the saturation state because `later` refreshed last_seen.
+    let _ = auth_probe_saturation_is_throttled_at_for_testing(check_time);
+    let guard = auth_probe_saturation_state_lock();
+    assert!(
+        guard.is_some(),
+        "Ongoing saturation notes must refresh last_seen so saturation state remains retained past the original window"
+    );
+}
+
+#[test]
+fn mtproto_classic_tags_rejected_when_only_secure_mode_enabled() {
+    let mut config = ProxyConfig::default();
+    config.general.modes.classic = false;
+    config.general.modes.secure = true;
+    config.general.modes.tls = false;
+
+    assert!(!mode_enabled_for_proto(&config, ProtoTag::Abridged, false));
+    assert!(!mode_enabled_for_proto(&config, ProtoTag::Intermediate, false));
+}
+
+#[test]
+fn mtproto_secure_tag_rejected_when_only_classic_mode_enabled() {
+    let mut config = ProxyConfig::default();
+    config.general.modes.classic = true;
+    config.general.modes.secure = false;
+    config.general.modes.tls = false;
+
+    assert!(!mode_enabled_for_proto(&config, ProtoTag::Secure, false));
+}
+
+#[test]
+fn ipv6_localhost_and_unspecified_normalization() {
+    let localhost = IpAddr::V6(Ipv6Addr::new(0, 0, 0, 0, 0, 0, 0, 1));
+    let unspecified = IpAddr::V6(Ipv6Addr::new(0, 0, 0, 0, 0, 0, 0, 0));
+
+    let norm_local = normalize_auth_probe_ip(localhost);
+    let norm_unspec = normalize_auth_probe_ip(unspecified);
+
+    let expected_bucket = IpAddr::V6(Ipv6Addr::new(0, 0, 0, 0, 0, 0, 0, 0));
+
+    assert_eq!(norm_local, expected_bucket);
+    assert_eq!(norm_unspec, expected_bucket);
+}

src/proxy/tests/handshake_real_bug_stress_tests.rs

@@ -0,0 +1,337 @@
+use super::*;
+use crate::crypto::{sha256, sha256_hmac, AesCtr, SecureRandom};
+use crate::protocol::constants::{ProtoTag, TLS_RECORD_HANDSHAKE, TLS_VERSION};
+use std::net::{IpAddr, Ipv4Addr, SocketAddr};
+use std::sync::Arc;
+use std::time::{Duration, Instant};
+use tokio::sync::Barrier;
+
+fn auth_probe_test_guard() -> std::sync::MutexGuard<'static, ()> {
+    auth_probe_test_lock()
+        .lock()
+        .unwrap_or_else(|poisoned| poisoned.into_inner())
+}
+
+fn test_config_with_secret_hex(secret_hex: &str) -> ProxyConfig {
+    let mut cfg = ProxyConfig::default();
+    cfg.access.users.clear();
+    cfg.access
+        .users
+        .insert("user".to_string(), secret_hex.to_string());
+    cfg.access.ignore_time_skew = true;
+    cfg.general.modes.secure = true;
+    cfg.general.modes.classic = true;
+    cfg.general.modes.tls = true;
+    cfg
+}
+
+fn make_valid_tls_client_hello_with_alpn(
+    secret: &[u8],
+    timestamp: u32,
+    alpn_protocols: &[&[u8]],
+) -> Vec<u8> {
+    let mut body = Vec::new();
+    body.extend_from_slice(&TLS_VERSION);
+    body.extend_from_slice(&[0u8; 32]);
+    body.push(32);
+    body.extend_from_slice(&[0x42u8; 32]);
+    body.extend_from_slice(&2u16.to_be_bytes());
+    body.extend_from_slice(&[0x13, 0x01]);
+    body.push(1);
+    body.push(0);
+
+    let mut ext_blob = Vec::new();
+    if !alpn_protocols.is_empty() {
+        let mut alpn_list = Vec::new();
+        for proto in alpn_protocols {
+            alpn_list.push(proto.len() as u8);
+            alpn_list.extend_from_slice(proto);
+        }
+        let mut alpn_data = Vec::new();
+        alpn_data.extend_from_slice(&(alpn_list.len() as u16).to_be_bytes());
+        alpn_data.extend_from_slice(&alpn_list);
+
+        ext_blob.extend_from_slice(&0x0010u16.to_be_bytes());
+        ext_blob.extend_from_slice(&(alpn_data.len() as u16).to_be_bytes());
+        ext_blob.extend_from_slice(&alpn_data);
+    }
+
+    body.extend_from_slice(&(ext_blob.len() as u16).to_be_bytes());
+    body.extend_from_slice(&ext_blob);
+
+    let mut handshake = Vec::new();
+    handshake.push(0x01);
+    let body_len = (body.len() as u32).to_be_bytes();
+    handshake.extend_from_slice(&body_len[1..4]);
+    handshake.extend_from_slice(&body);
+
+    let mut record = Vec::new();
+    record.push(TLS_RECORD_HANDSHAKE);
+    record.extend_from_slice(&[0x03, 0x01]);
+    record.extend_from_slice(&(handshake.len() as u16).to_be_bytes());
+    record.extend_from_slice(&handshake);
+
+    record[tls::TLS_DIGEST_POS..tls::TLS_DIGEST_POS + tls::TLS_DIGEST_LEN].fill(0);
+
+    let computed = sha256_hmac(secret, &record);
+    let mut digest = computed;
+    let ts = timestamp.to_le_bytes();
+    for i in 0..4 {
+        digest[28 + i] ^= ts[i];
+    }
+
+    record[tls::TLS_DIGEST_POS..tls::TLS_DIGEST_POS + tls::TLS_DIGEST_LEN]
+        .copy_from_slice(&digest);
+
+    record
+}
+
+fn make_valid_mtproto_handshake(
+    secret_hex: &str,
+    proto_tag: ProtoTag,
+    dc_idx: i16,
+) -> [u8; HANDSHAKE_LEN] {
+    let secret = hex::decode(secret_hex).expect("secret hex must decode");
+    let mut handshake = [0x5Au8; HANDSHAKE_LEN];
+    for (idx, b) in handshake[SKIP_LEN..SKIP_LEN + PREKEY_LEN + IV_LEN]
+        .iter_mut()
+        .enumerate()
+    {
+        *b = (idx as u8).wrapping_add(1);
+    }
+
+    let dec_prekey = &handshake[SKIP_LEN..SKIP_LEN + PREKEY_LEN];
+    let dec_iv_bytes = &handshake[SKIP_LEN + PREKEY_LEN..SKIP_LEN + PREKEY_LEN + IV_LEN];
+
+    let mut dec_key_input = Vec::with_capacity(PREKEY_LEN + secret.len());
+    dec_key_input.extend_from_slice(dec_prekey);
+    dec_key_input.extend_from_slice(&secret);
+    let dec_key = sha256(&dec_key_input);
+
+    let mut dec_iv_arr = [0u8; IV_LEN];
+    dec_iv_arr.copy_from_slice(dec_iv_bytes);
+    let dec_iv = u128::from_be_bytes(dec_iv_arr);
+
+    let mut stream = AesCtr::new(&dec_key, dec_iv);
+    let keystream = stream.encrypt(&[0u8; HANDSHAKE_LEN]);
+
+    let mut target_plain = [0u8; HANDSHAKE_LEN];
+    target_plain[PROTO_TAG_POS..PROTO_TAG_POS + 4].copy_from_slice(&proto_tag.to_bytes());
+    target_plain[DC_IDX_POS..DC_IDX_POS + 2].copy_from_slice(&dc_idx.to_le_bytes());
+
+    for idx in PROTO_TAG_POS..HANDSHAKE_LEN {
+        handshake[idx] = target_plain[idx] ^ keystream[idx];
+    }
+
+    handshake
+}
+
+#[tokio::test]
+async fn tls_alpn_reject_does_not_pollute_replay_cache() {
+    let _guard = auth_probe_test_guard();
+    clear_auth_probe_state_for_testing();
+
+    let secret = [0x11u8; 16];
+    let mut config = test_config_with_secret_hex("11111111111111111111111111111111");
+    config.censorship.alpn_enforce = true;
+
+    let replay_checker = ReplayChecker::new(128, Duration::from_secs(60));
+    let rng = SecureRandom::new();
+    let peer: SocketAddr = "192.0.2.201:12345".parse().unwrap();
+
+    let handshake = make_valid_tls_client_hello_with_alpn(&secret, 0, &[b"h3"]);
+    let before = replay_checker.stats();
+
+    let res = handle_tls_handshake(
+        &handshake,
+        tokio::io::empty(),
+        tokio::io::sink(),
+        peer,
+        &config,
+        &replay_checker,
+        &rng,
+        None,
+    )
+    .await;
+
+    let after = replay_checker.stats();
+
+    assert!(matches!(res, HandshakeResult::BadClient { .. }));
+    assert_eq!(
+        before.total_additions, after.total_additions,
+        "ALPN policy reject must not add TLS digest into replay cache"
+    );
+}
+
+#[tokio::test]
+async fn tls_truncated_session_id_len_fails_closed_without_panic() {
+    let _guard = auth_probe_test_guard();
+    clear_auth_probe_state_for_testing();
+
+    let config = test_config_with_secret_hex("33333333333333333333333333333333");
+    let replay_checker = ReplayChecker::new(128, Duration::from_secs(60));
+    let rng = SecureRandom::new();
+    let peer: SocketAddr = "192.0.2.203:12345".parse().unwrap();
+
+    let min_len = tls::TLS_DIGEST_POS + tls::TLS_DIGEST_LEN + 1;
+    let mut malicious = vec![0x42u8; min_len];
+    malicious[min_len - 1] = u8::MAX;
+
+    let res = handle_tls_handshake(
+        &malicious,
+        tokio::io::empty(),
+        tokio::io::sink(),
+        peer,
+        &config,
+        &replay_checker,
+        &rng,
+        None,
+    )
+    .await;
+
+    assert!(matches!(res, HandshakeResult::BadClient { .. }));
+}
+
+#[test]
+fn auth_probe_eviction_identical_timestamps_keeps_map_bounded() {
+    let _guard = auth_probe_test_guard();
+    clear_auth_probe_state_for_testing();
+
+    let state = auth_probe_state_map();
+    let same = Instant::now();
+
+    for i in 0..AUTH_PROBE_TRACK_MAX_ENTRIES {
+        let ip = IpAddr::V4(Ipv4Addr::new(10, 1, (i >> 8) as u8, (i & 0xFF) as u8));
+        state.insert(
+            ip,
+            AuthProbeState {
+                fail_streak: 7,
+                blocked_until: same,
+                last_seen: same,
+            },
+        );
+    }
+
+    let new_ip = IpAddr::V4(Ipv4Addr::new(192, 168, 21, 21));
+    auth_probe_record_failure_with_state(state, new_ip, same + Duration::from_millis(1));
+
+    assert_eq!(state.len(), AUTH_PROBE_TRACK_MAX_ENTRIES);
+    assert!(state.contains_key(&new_ip));
+}
+
+#[test]
+fn clear_auth_probe_state_recovers_from_poisoned_saturation_lock() {
+    let _guard = auth_probe_test_guard();
+    clear_auth_probe_state_for_testing();
+
+    let saturation = auth_probe_saturation_state();
+    let poison_thread = std::thread::spawn(move || {
+        let _hold = saturation
+            .lock()
+            .unwrap_or_else(|poisoned| poisoned.into_inner());
+        panic!("intentional poison for regression coverage");
+    });
+    let _ = poison_thread.join();
+
+    clear_auth_probe_state_for_testing();
+
+    let guard = auth_probe_saturation_state()
+        .lock()
+        .unwrap_or_else(|poisoned| poisoned.into_inner());
+    assert!(guard.is_none());
+}
+
+#[tokio::test]
+async fn mtproto_invalid_length_secret_is_ignored_and_valid_user_still_auths() {
+    let _probe_guard = auth_probe_test_guard();
+    let _warn_guard = warned_secrets_test_lock()
+        .lock()
+        .unwrap_or_else(|poisoned| poisoned.into_inner());
+    clear_auth_probe_state_for_testing();
+    clear_warned_secrets_for_testing();
+
+    let mut config = ProxyConfig::default();
+    config.general.modes.secure = true;
+    config.access.ignore_time_skew = true;
+
+    config.access.users.insert(
+        "short_user".to_string(),
+        "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaa".to_string(),
+    );
+
+    let valid_secret_hex = "77777777777777777777777777777777";
+    config
+        .access
+        .users
+        .insert("good_user".to_string(), valid_secret_hex.to_string());
+
+    let replay_checker = ReplayChecker::new(128, Duration::from_secs(60));
+    let peer: SocketAddr = "192.0.2.207:12345".parse().unwrap();
+    let handshake = make_valid_mtproto_handshake(valid_secret_hex, ProtoTag::Secure, 1);
+
+    let res = handle_mtproto_handshake(
+        &handshake,
+        tokio::io::empty(),
+        tokio::io::sink(),
+        peer,
+        &config,
+        &replay_checker,
+        false,
+        None,
+    )
+    .await;
+
+    assert!(matches!(res, HandshakeResult::Success(_)));
+}
+
+#[tokio::test(flavor = "multi_thread", worker_threads = 4)]
+async fn saturation_grace_exhaustion_under_concurrency_keeps_peer_throttled() {
+    let _guard = auth_probe_test_guard();
+    clear_auth_probe_state_for_testing();
+
+    let peer_ip = IpAddr::V4(Ipv4Addr::new(198, 51, 100, 80));
+    let now = Instant::now();
+
+    {
+        let mut guard = auth_probe_saturation_state()
+            .lock()
+            .unwrap_or_else(|poisoned| poisoned.into_inner());
+        *guard = Some(AuthProbeSaturationState {
+            fail_streak: AUTH_PROBE_BACKOFF_START_FAILS,
+            blocked_until: now + Duration::from_secs(5),
+            last_seen: now,
+        });
+    }
+
+    let state = auth_probe_state_map();
+    state.insert(
+        peer_ip,
+        AuthProbeState {
+            fail_streak: AUTH_PROBE_BACKOFF_START_FAILS + AUTH_PROBE_SATURATION_GRACE_FAILS - 1,
+            blocked_until: now,
+            last_seen: now,
+        },
+    );
+
+    let tasks = 32;
+    let barrier = Arc::new(Barrier::new(tasks));
+    let mut handles = Vec::new();
+
+    for _ in 0..tasks {
+        let b = barrier.clone();
+        handles.push(tokio::spawn(async move {
+            b.wait().await;
+            auth_probe_record_failure(peer_ip, Instant::now());
+        }));
+    }
+
+    for handle in handles {
+        handle.await.unwrap();
+    }
+
+    let final_state = state.get(&peer_ip).expect("state must exist");
+    assert!(
+        final_state.fail_streak >= AUTH_PROBE_BACKOFF_START_FAILS + AUTH_PROBE_SATURATION_GRACE_FAILS
+    );
+    assert!(auth_probe_should_apply_preauth_throttle(peer_ip, Instant::now()));
+}

src/proxy/tests/handshake_timing_manual_bench_tests.rs

@@ -0,0 +1,318 @@
+use super::*;
+use crate::crypto::{sha256, sha256_hmac, AesCtr, SecureRandom};
+use crate::protocol::constants::{ProtoTag, TLS_RECORD_HANDSHAKE, TLS_VERSION};
+use std::net::SocketAddr;
+use std::time::{Duration, Instant};
+
+fn auth_probe_test_guard() -> std::sync::MutexGuard<'static, ()> {
+    auth_probe_test_lock()
+        .lock()
+        .unwrap_or_else(|poisoned| poisoned.into_inner())
+}
+
+fn make_valid_mtproto_handshake(
+    secret_hex: &str,
+    proto_tag: ProtoTag,
+    dc_idx: i16,
+    salt: u8,
+) -> [u8; HANDSHAKE_LEN] {
+    let secret = hex::decode(secret_hex).expect("secret hex must decode");
+    let mut handshake = [0x5Au8; HANDSHAKE_LEN];
+
+    for (idx, b) in handshake[SKIP_LEN..SKIP_LEN + PREKEY_LEN + IV_LEN]
+        .iter_mut()
+        .enumerate()
+    {
+        *b = (idx as u8).wrapping_add(1).wrapping_add(salt);
+    }
+
+    let dec_prekey = &handshake[SKIP_LEN..SKIP_LEN + PREKEY_LEN];
+    let dec_iv_bytes = &handshake[SKIP_LEN + PREKEY_LEN..SKIP_LEN + PREKEY_LEN + IV_LEN];
+
+    let mut dec_key_input = Vec::with_capacity(PREKEY_LEN + secret.len());
+    dec_key_input.extend_from_slice(dec_prekey);
+    dec_key_input.extend_from_slice(&secret);
+    let dec_key = sha256(&dec_key_input);
+
+    let mut dec_iv_arr = [0u8; IV_LEN];
+    dec_iv_arr.copy_from_slice(dec_iv_bytes);
+    let dec_iv = u128::from_be_bytes(dec_iv_arr);
+
+    let mut stream = AesCtr::new(&dec_key, dec_iv);
+    let keystream = stream.encrypt(&[0u8; HANDSHAKE_LEN]);
+
+    let mut target_plain = [0u8; HANDSHAKE_LEN];
+    target_plain[PROTO_TAG_POS..PROTO_TAG_POS + 4].copy_from_slice(&proto_tag.to_bytes());
+    target_plain[DC_IDX_POS..DC_IDX_POS + 2].copy_from_slice(&dc_idx.to_le_bytes());
+
+    for idx in PROTO_TAG_POS..HANDSHAKE_LEN {
+        handshake[idx] = target_plain[idx] ^ keystream[idx];
+    }
+
+    handshake
+}
+
+fn make_valid_tls_handshake(secret: &[u8], timestamp: u32) -> Vec<u8> {
+    let session_id_len: usize = 32;
+    let len = tls::TLS_DIGEST_POS + tls::TLS_DIGEST_LEN + 1 + session_id_len;
+    let mut handshake = vec![0x42u8; len];
+
+    handshake[tls::TLS_DIGEST_POS + tls::TLS_DIGEST_LEN] = session_id_len as u8;
+    handshake[tls::TLS_DIGEST_POS..tls::TLS_DIGEST_POS + tls::TLS_DIGEST_LEN].fill(0);
+
+    let computed = sha256_hmac(secret, &handshake);
+    let mut digest = computed;
+    let ts = timestamp.to_le_bytes();
+    for i in 0..4 {
+        digest[28 + i] ^= ts[i];
+    }
+
+    handshake[tls::TLS_DIGEST_POS..tls::TLS_DIGEST_POS + tls::TLS_DIGEST_LEN]
+        .copy_from_slice(&digest);
+    handshake
+}
+
+fn make_valid_tls_client_hello_with_sni_and_alpn(
+    secret: &[u8],
+    timestamp: u32,
+    sni_host: &str,
+    alpn_protocols: &[&[u8]],
+) -> Vec<u8> {
+    let mut body = Vec::new();
+    body.extend_from_slice(&TLS_VERSION);
+    body.extend_from_slice(&[0u8; 32]);
+    body.push(32);
+    body.extend_from_slice(&[0x42u8; 32]);
+    body.extend_from_slice(&2u16.to_be_bytes());
+    body.extend_from_slice(&[0x13, 0x01]);
+    body.push(1);
+    body.push(0);
+
+    let mut ext_blob = Vec::new();
+    let host_bytes = sni_host.as_bytes();
+    let mut sni_payload = Vec::new();
+    sni_payload.extend_from_slice(&((host_bytes.len() + 3) as u16).to_be_bytes());
+    sni_payload.push(0);
+    sni_payload.extend_from_slice(&(host_bytes.len() as u16).to_be_bytes());
+    sni_payload.extend_from_slice(host_bytes);
+    ext_blob.extend_from_slice(&0x0000u16.to_be_bytes());
+    ext_blob.extend_from_slice(&(sni_payload.len() as u16).to_be_bytes());
+    ext_blob.extend_from_slice(&sni_payload);
+
+    if !alpn_protocols.is_empty() {
+        let mut alpn_list = Vec::new();
+        for proto in alpn_protocols {
+            alpn_list.push(proto.len() as u8);
+            alpn_list.extend_from_slice(proto);
+        }
+        let mut alpn_data = Vec::new();
+        alpn_data.extend_from_slice(&(alpn_list.len() as u16).to_be_bytes());
+        alpn_data.extend_from_slice(&alpn_list);
+
+        ext_blob.extend_from_slice(&0x0010u16.to_be_bytes());
+        ext_blob.extend_from_slice(&(alpn_data.len() as u16).to_be_bytes());
+        ext_blob.extend_from_slice(&alpn_data);
+    }
+
+    body.extend_from_slice(&(ext_blob.len() as u16).to_be_bytes());
+    body.extend_from_slice(&ext_blob);
+
+    let mut handshake = Vec::new();
+    handshake.push(0x01);
+    let body_len = (body.len() as u32).to_be_bytes();
+    handshake.extend_from_slice(&body_len[1..4]);
+    handshake.extend_from_slice(&body);
+
+    let mut record = Vec::new();
+    record.push(TLS_RECORD_HANDSHAKE);
+    record.extend_from_slice(&[0x03, 0x01]);
+    record.extend_from_slice(&(handshake.len() as u16).to_be_bytes());
+    record.extend_from_slice(&handshake);
+
+    record[tls::TLS_DIGEST_POS..tls::TLS_DIGEST_POS + tls::TLS_DIGEST_LEN].fill(0);
+    let computed = sha256_hmac(secret, &record);
+    let mut digest = computed;
+    let ts = timestamp.to_le_bytes();
+    for i in 0..4 {
+        digest[28 + i] ^= ts[i];
+    }
+    record[tls::TLS_DIGEST_POS..tls::TLS_DIGEST_POS + tls::TLS_DIGEST_LEN].copy_from_slice(&digest);
+
+    record
+}
+
+fn median_ns(samples: &mut [u128]) -> u128 {
+    samples.sort_unstable();
+    samples[samples.len() / 2]
+}
+
+#[tokio::test]
+#[ignore = "manual benchmark: timing-sensitive and host-dependent"]
+async fn mtproto_user_scan_timing_manual_benchmark() {
+    let _guard = auth_probe_test_guard();
+    clear_auth_probe_state_for_testing();
+
+    const DECOY_USERS: usize = 8_000;
+    const ITERATIONS: usize = 250;
+
+    let preferred_user = "target_user";
+    let target_secret_hex = "dededededededededededededededede";
+
+    let mut config = ProxyConfig::default();
+    config.general.modes.secure = true;
+    config.access.ignore_time_skew = true;
+
+    for i in 0..DECOY_USERS {
+        config.access.users.insert(
+            format!("decoy_{i}"),
+            "00000000000000000000000000000000".to_string(),
+        );
+    }
+
+    config.access.users.insert(
+        preferred_user.to_string(),
+        target_secret_hex.to_string(),
+    );
+
+    let replay_checker_preferred = ReplayChecker::new(65_536, Duration::from_secs(60));
+    let replay_checker_full_scan = ReplayChecker::new(65_536, Duration::from_secs(60));
+    let peer_a: SocketAddr = "192.0.2.241:12345".parse().unwrap();
+    let peer_b: SocketAddr = "192.0.2.242:12345".parse().unwrap();
+
+    let mut preferred_samples = Vec::with_capacity(ITERATIONS);
+    let mut full_scan_samples = Vec::with_capacity(ITERATIONS);
+
+    for i in 0..ITERATIONS {
+        let handshake = make_valid_mtproto_handshake(
+            target_secret_hex,
+            ProtoTag::Secure,
+            1 + i as i16,
+            (i % 251) as u8,
+        );
+
+        let started_preferred = Instant::now();
+        let preferred = handle_mtproto_handshake(
+            &handshake,
+            tokio::io::empty(),
+            tokio::io::sink(),
+            peer_a,
+            &config,
+            &replay_checker_preferred,
+            false,
+            Some(preferred_user),
+        )
+        .await;
+        preferred_samples.push(started_preferred.elapsed().as_nanos());
+        assert!(matches!(preferred, HandshakeResult::Success(_)));
+
+        let started_scan = Instant::now();
+        let full_scan = handle_mtproto_handshake(
+            &handshake,
+            tokio::io::empty(),
+            tokio::io::sink(),
+            peer_b,
+            &config,
+            &replay_checker_full_scan,
+            false,
+            None,
+        )
+        .await;
+        full_scan_samples.push(started_scan.elapsed().as_nanos());
+        assert!(matches!(full_scan, HandshakeResult::Success(_)));
+    }
+
+    let preferred_median = median_ns(&mut preferred_samples);
+    let full_scan_median = median_ns(&mut full_scan_samples);
+
+    let ratio = if preferred_median == 0 {
+        0.0
+    } else {
+        full_scan_median as f64 / preferred_median as f64
+    };
+
+    println!(
+        "manual timing benchmark: decoys={DECOY_USERS}, iters={ITERATIONS}, preferred_median_ns={preferred_median}, full_scan_median_ns={full_scan_median}, ratio={ratio:.3}"
+    );
+
+    assert!(
+        full_scan_median >= preferred_median,
+        "full user scan should not be faster than preferred-user path in this benchmark"
+    );
+}
+
+#[tokio::test]
+#[ignore = "manual benchmark: timing-sensitive and host-dependent"]
+async fn tls_sni_preferred_vs_no_sni_fallback_manual_benchmark() {
+    let _guard = auth_probe_test_guard();
+
+    const DECOY_USERS: usize = 8_000;
+    const ITERATIONS: usize = 250;
+
+    let preferred_user = "user-b";
+    let target_secret_hex = "abababababababababababababababab";
+    let target_secret = [0xABu8; 16];
+
+    let mut config = ProxyConfig::default();
+    config.general.modes.tls = true;
+    config.access.ignore_time_skew = true;
+
+    for i in 0..DECOY_USERS {
+        config.access.users.insert(
+            format!("decoy_{i}"),
+            "00000000000000000000000000000000".to_string(),
+        );
+    }
+
+    config
+        .access
+        .users
+        .insert(preferred_user.to_string(), target_secret_hex.to_string());
+
+    let mut sni_samples = Vec::with_capacity(ITERATIONS);
+    let mut no_sni_samples = Vec::with_capacity(ITERATIONS);
+
+    for i in 0..ITERATIONS {
+        let with_sni = make_valid_tls_client_hello_with_sni_and_alpn(
+            &target_secret,
+            i as u32,
+            preferred_user,
+            &[b"h2"],
+        );
+        let no_sni = make_valid_tls_handshake(&target_secret, (i as u32).wrapping_add(10_000));
+
+        let started_sni = Instant::now();
+        let sni_secrets = decode_user_secrets(&config, Some(preferred_user));
+        let sni_result = tls::validate_tls_handshake_with_replay_window(
+            &with_sni,
+            &sni_secrets,
+            config.access.ignore_time_skew,
+            config.access.replay_window_secs,
+        );
+        sni_samples.push(started_sni.elapsed().as_nanos());
+        assert!(sni_result.is_some());
+
+        let started_no_sni = Instant::now();
+        let no_sni_secrets = decode_user_secrets(&config, None);
+        let no_sni_result = tls::validate_tls_handshake_with_replay_window(
+            &no_sni,
+            &no_sni_secrets,
+            config.access.ignore_time_skew,
+            config.access.replay_window_secs,
+        );
+        no_sni_samples.push(started_no_sni.elapsed().as_nanos());
+        assert!(no_sni_result.is_some());
+    }
+
+    let sni_median = median_ns(&mut sni_samples);
+    let no_sni_median = median_ns(&mut no_sni_samples);
+
+    let ratio = if sni_median == 0 {
+        0.0
+    } else {
+        no_sni_median as f64 / sni_median as f64
+    };
+
+    println!(
+        "manual tls benchmark: decoys={DECOY_USERS}, iters={ITERATIONS}, sni_median_ns={sni_median}, no_sni_median_ns={no_sni_median}, ratio_no_sni_over_sni={ratio:.3}"
+    );
+}

src/proxy/tests/masking_ab_envelope_blur_integration_security_tests.rs

@@ -493,9 +493,12 @@ async fn timing_classifier_light_fuzz_pairwise_bucketed_accuracy_stays_bounded_u
     ];
 
     let mut meaningful_improvement_seen = false;
-    let mut baseline_sum = 0.0f64;
-    let mut hardened_sum = 0.0f64;
-    let mut pair_count = 0usize;
+    let mut informative_baseline_sum = 0.0f64;
+    let mut informative_hardened_sum = 0.0f64;
+    let mut informative_pair_count = 0usize;
+    let mut low_info_baseline_sum = 0.0f64;
+    let mut low_info_hardened_sum = 0.0f64;
+    let mut low_info_pair_count = 0usize;
     let acc_quant_step = 1.0 / (2 * SAMPLE_COUNT) as f64;
     let tolerated_pair_regression = acc_quant_step + 0.03;
 
@@ -522,6 +525,16 @@ async fn timing_classifier_light_fuzz_pairwise_bucketed_accuracy_stays_bounded_u
                 hardened_acc <= baseline_acc + tolerated_pair_regression,
                 "normalization should not materially worsen informative pair: baseline={baseline_acc:.3} hardened={hardened_acc:.3} tolerated={tolerated_pair_regression:.3}"
             );
+            informative_baseline_sum += baseline_acc;
+            informative_hardened_sum += hardened_acc;
+            informative_pair_count += 1;
+        } else {
+            // Low-information pairs (near-random baseline separability) are expected
+            // to exhibit quantized jitter at low sample counts; do not fold them into
+            // strict average-regression checks used for informative side-channel signal.
+            low_info_baseline_sum += baseline_acc;
+            low_info_hardened_sum += hardened_acc;
+            low_info_pair_count += 1;
         }
 
         println!(
@@ -532,19 +545,30 @@ async fn timing_classifier_light_fuzz_pairwise_bucketed_accuracy_stays_bounded_u
             meaningful_improvement_seen = true;
         }
 
-        baseline_sum += baseline_acc;
-        hardened_sum += hardened_acc;
-        pair_count += 1;
     }
 
-    let baseline_avg = baseline_sum / pair_count as f64;
-    let hardened_avg = hardened_sum / pair_count as f64;
+    assert!(
+        informative_pair_count > 0,
+        "expected at least one informative pair for timing-separability guard"
+    );
+
+    let informative_baseline_avg = informative_baseline_sum / informative_pair_count as f64;
+    let informative_hardened_avg = informative_hardened_sum / informative_pair_count as f64;
 
     assert!(
-        hardened_avg <= baseline_avg + 0.10,
-        "normalization should not materially increase average pairwise separability: baseline_avg={baseline_avg:.3} hardened_avg={hardened_avg:.3}"
+        informative_hardened_avg <= informative_baseline_avg + 0.10,
+        "normalization should not materially increase informative average separability: baseline_avg={informative_baseline_avg:.3} hardened_avg={informative_hardened_avg:.3}"
     );
 
+    if low_info_pair_count > 0 {
+        let low_info_baseline_avg = low_info_baseline_sum / low_info_pair_count as f64;
+        let low_info_hardened_avg = low_info_hardened_sum / low_info_pair_count as f64;
+        assert!(
+            low_info_hardened_avg <= low_info_baseline_avg + 0.40,
+            "normalization low-info average drift exceeded jitter budget: baseline_avg={low_info_baseline_avg:.3} hardened_avg={low_info_hardened_avg:.3}"
+        );
+    }
+
     // Optional signal only: do not require improvement on every run because
     // noisy CI schedulers can flatten pairwise differences at low sample counts.
     let _ = meaningful_improvement_seen;

src/proxy/tests/masking_additional_hardening_security_tests.rs

@@ -0,0 +1,122 @@
+use super::*;
+use std::pin::Pin;
+use std::sync::Arc;
+use std::sync::atomic::{AtomicUsize, Ordering};
+use std::task::{Context, Poll};
+use tokio::io::AsyncRead;
+use tokio::time::{Duration, timeout};
+
+struct EndlessReader {
+    produced: Arc<AtomicUsize>,
+}
+
+impl AsyncRead for EndlessReader {
+    fn poll_read(
+        self: Pin<&mut Self>,
+        _cx: &mut Context<'_>,
+        buf: &mut tokio::io::ReadBuf<'_>,
+    ) -> Poll<std::io::Result<()>> {
+        let len = buf.remaining().max(1);
+        let fill = vec![0xAA; len];
+        buf.put_slice(&fill);
+        self.produced.fetch_add(len, Ordering::Relaxed);
+        Poll::Ready(Ok(()))
+    }
+}
+
+#[test]
+fn loop_guard_unspecified_bind_uses_interface_inventory() {
+    let local: SocketAddr = "0.0.0.0:443".parse().unwrap();
+    let resolved: SocketAddr = "192.168.44.10:443".parse().unwrap();
+    let interfaces = vec!["192.168.44.10".parse().unwrap()];
+
+    assert!(is_mask_target_local_listener_with_interfaces(
+        "mask.example",
+        443,
+        local,
+        Some(resolved),
+        &interfaces,
+    ));
+}
+
+#[tokio::test]
+async fn consume_client_data_stops_after_byte_cap_without_eof() {
+    let produced = Arc::new(AtomicUsize::new(0));
+    let reader = EndlessReader {
+        produced: Arc::clone(&produced),
+    };
+    let cap = 10_000usize;
+
+    consume_client_data(reader, cap).await;
+
+    let total = produced.load(Ordering::Relaxed);
+    assert!(
+        total >= cap,
+        "consume path must read at least up to cap before stopping"
+    );
+    assert!(
+        total <= cap + 8192,
+        "consume path must stop within one read chunk above cap"
+    );
+}
+
+#[test]
+fn masking_beobachten_minutes_zero_fail_closes_to_minimum_ttl() {
+    let mut config = ProxyConfig::default();
+    config.general.beobachten = true;
+    config.general.beobachten_minutes = 0;
+
+    let ttl = masking_beobachten_ttl(&config);
+    assert_eq!(ttl, std::time::Duration::from_secs(60));
+}
+
+#[test]
+fn timing_normalization_zero_floor_safety_net_defaults_to_mask_timeout() {
+    let mut config = ProxyConfig::default();
+    config.censorship.mask_timing_normalization_enabled = true;
+    config.censorship.mask_timing_normalization_floor_ms = 0;
+    config.censorship.mask_timing_normalization_ceiling_ms = 0;
+
+    let budget = mask_outcome_target_budget(&config);
+    assert_eq!(budget, MASK_TIMEOUT);
+}
+
+#[tokio::test]
+async fn loop_guard_blocks_self_target_before_proxy_protocol_header_growth() {
+    let listener = tokio::net::TcpListener::bind("127.0.0.1:0").await.unwrap();
+    let backend_addr = listener.local_addr().unwrap();
+    let accept_task = tokio::spawn(async move {
+        timeout(Duration::from_millis(120), listener.accept())
+            .await
+            .is_ok()
+    });
+
+    let mut config = ProxyConfig::default();
+    config.general.beobachten = false;
+    config.censorship.mask = true;
+    config.censorship.mask_unix_sock = None;
+    config.censorship.mask_host = Some("127.0.0.1".to_string());
+    config.censorship.mask_port = backend_addr.port();
+    config.censorship.mask_proxy_protocol = 2;
+
+    let peer: SocketAddr = "203.0.113.251:55991".parse().unwrap();
+    let local_addr: SocketAddr = format!("0.0.0.0:{}", backend_addr.port()).parse().unwrap();
+    let beobachten = BeobachtenStore::new();
+
+    handle_bad_client(
+        tokio::io::empty(),
+        tokio::io::sink(),
+        b"GET / HTTP/1.1\r\n\r\n",
+        peer,
+        local_addr,
+        &config,
+        &beobachten,
+    )
+    .await;
+
+    let accepted = accept_task.await.unwrap();
+    assert!(
+        !accepted,
+        "loop guard must fail closed before any recursive PROXY protocol amplification"
+    );
+}

src/proxy/tests/masking_classification_completeness_security_tests.rs

@@ -0,0 +1,16 @@
+use super::*;
+
+#[test]
+fn detect_client_type_recognizes_extended_http_probe_verbs() {
+    assert_eq!(detect_client_type(b"CONNECT / HTTP/1.1\r\n"), "HTTP");
+    assert_eq!(detect_client_type(b"TRACE / HTTP/1.1\r\n"), "HTTP");
+    assert_eq!(detect_client_type(b"PATCH / HTTP/1.1\r\n"), "HTTP");
+}
+
+#[test]
+fn detect_client_type_recognizes_fragmented_http_method_prefixes() {
+    assert_eq!(detect_client_type(b"CO"), "HTTP");
+    assert_eq!(detect_client_type(b"CON"), "HTTP");
+    assert_eq!(detect_client_type(b"TR"), "HTTP");
+    assert_eq!(detect_client_type(b"PAT"), "HTTP");
+}

src/proxy/tests/masking_connect_failure_close_matrix_security_tests.rs

@@ -0,0 +1,127 @@
+use super::*;
+use crate::network::dns_overrides::install_entries;
+use tokio::io::{AsyncReadExt, AsyncWriteExt, duplex};
+use tokio::time::{Duration, Instant, timeout};
+
+async fn run_connect_failure_case(
+    host: &str,
+    port: u16,
+    timing_normalization_enabled: bool,
+    peer: SocketAddr,
+) -> Duration {
+    let mut config = ProxyConfig::default();
+    config.general.beobachten = false;
+    config.censorship.mask = true;
+    config.censorship.mask_unix_sock = None;
+    config.censorship.mask_host = Some(host.to_string());
+    config.censorship.mask_port = port;
+    config.censorship.mask_timing_normalization_enabled = timing_normalization_enabled;
+    config.censorship.mask_timing_normalization_floor_ms = 120;
+    config.censorship.mask_timing_normalization_ceiling_ms = 120;
+
+    let local_addr: SocketAddr = "127.0.0.1:443".parse().unwrap();
+    let beobachten = BeobachtenStore::new();
+    let probe = b"CONNECT example.org:443 HTTP/1.1\r\nHost: example.org\r\n\r\n";
+
+    let (mut client_writer, client_reader) = duplex(1024);
+    let (mut client_visible_reader, client_visible_writer) = duplex(1024);
+
+    let started = Instant::now();
+    let task = tokio::spawn(async move {
+        handle_bad_client(
+            client_reader,
+            client_visible_writer,
+            probe,
+            peer,
+            local_addr,
+            &config,
+            &beobachten,
+        )
+        .await;
+    });
+
+    client_writer.shutdown().await.unwrap();
+
+    timeout(Duration::from_secs(4), task)
+        .await
+        .unwrap()
+        .unwrap();
+
+    let mut buf = [0u8; 1];
+    let n = timeout(Duration::from_secs(1), client_visible_reader.read(&mut buf))
+        .await
+        .unwrap()
+        .unwrap();
+    assert_eq!(n, 0, "connect-failure path must close client-visible writer");
+
+    started.elapsed()
+}
+
+#[tokio::test]
+async fn connect_failure_refusal_close_behavior_matrix() {
+    let temp_listener = tokio::net::TcpListener::bind("127.0.0.1:0").await.unwrap();
+    let unused_port = temp_listener.local_addr().unwrap().port();
+    drop(temp_listener);
+
+    for (idx, timing_normalization_enabled) in [false, true].into_iter().enumerate() {
+        let peer: SocketAddr = format!("203.0.113.210:{}", 54100 + idx as u16)
+            .parse()
+            .unwrap();
+        let elapsed = run_connect_failure_case(
+            "127.0.0.1",
+            unused_port,
+            timing_normalization_enabled,
+            peer,
+        )
+        .await;
+
+        if timing_normalization_enabled {
+            assert!(
+                elapsed >= Duration::from_millis(110) && elapsed < Duration::from_millis(250),
+                "normalized refusal path must honor configured timing envelope without stalling"
+            );
+        } else {
+            assert!(
+                elapsed >= Duration::from_millis(40) && elapsed < Duration::from_millis(150),
+                "non-normalized refusal path must honor baseline connect budget without stalling"
+            );
+        }
+    }
+}
+
+#[tokio::test]
+async fn connect_failure_overridden_hostname_close_behavior_matrix() {
+    let temp_listener = tokio::net::TcpListener::bind("127.0.0.1:0").await.unwrap();
+    let unused_port = temp_listener.local_addr().unwrap().port();
+    drop(temp_listener);
+
+    // Make hostname resolution deterministic in tests so timing ceilings are meaningful.
+    install_entries(&[format!("mask.invalid:{}:127.0.0.1", unused_port)]).unwrap();
+
+    for (idx, timing_normalization_enabled) in [false, true].into_iter().enumerate() {
+        let peer: SocketAddr = format!("203.0.113.220:{}", 54200 + idx as u16)
+            .parse()
+            .unwrap();
+        let elapsed = run_connect_failure_case(
+            "mask.invalid",
+            unused_port,
+            timing_normalization_enabled,
+            peer,
+        )
+        .await;
+
+        if timing_normalization_enabled {
+            assert!(
+                elapsed >= Duration::from_millis(110) && elapsed < Duration::from_millis(250),
+                "normalized overridden-host path must honor configured timing envelope without stalling"
+            );
+        } else {
+            assert!(
+                elapsed >= Duration::from_millis(40) && elapsed < Duration::from_millis(150),
+                "non-normalized overridden-host path must honor baseline connect budget without stalling"
+            );
+        }
+    }
+
+    install_entries(&[]).unwrap();
+}

src/proxy/tests/masking_consume_idle_timeout_security_tests.rs

@@ -0,0 +1,85 @@
+use super::*;
+use std::pin::Pin;
+use std::task::{Context, Poll};
+use std::time::Instant;
+use tokio::io::{AsyncRead, ReadBuf};
+
+struct OneByteThenStall {
+    sent: bool,
+}
+
+impl AsyncRead for OneByteThenStall {
+    fn poll_read(
+        mut self: Pin<&mut Self>,
+        _cx: &mut Context<'_>,
+        buf: &mut ReadBuf<'_>,
+    ) -> Poll<std::io::Result<()>> {
+        if !self.sent {
+            self.sent = true;
+            buf.put_slice(&[0x42]);
+            Poll::Ready(Ok(()))
+        } else {
+            Poll::Pending
+        }
+    }
+}
+
+#[tokio::test]
+async fn stalling_client_terminates_at_idle_not_relay_timeout() {
+    let reader = OneByteThenStall { sent: false };
+    let started = Instant::now();
+
+    let result = tokio::time::timeout(
+        MASK_RELAY_TIMEOUT,
+        consume_client_data(reader, MASK_BUFFER_SIZE * 4),
+    )
+    .await;
+
+    assert!(
+        result.is_ok(),
+        "consume_client_data should complete by per-read idle timeout, not hit relay timeout"
+    );
+
+    let elapsed = started.elapsed();
+    assert!(
+        elapsed >= (MASK_RELAY_IDLE_TIMEOUT / 2),
+        "consume_client_data returned too quickly for idle-timeout path: {elapsed:?}"
+    );
+    assert!(
+        elapsed < MASK_RELAY_TIMEOUT,
+        "consume_client_data waited full relay timeout ({elapsed:?}); \
+         per-read idle timeout is missing"
+    );
+}
+
+#[tokio::test]
+async fn fast_reader_drains_to_eof() {
+    let data = vec![0xAAu8; 32 * 1024];
+    let reader = std::io::Cursor::new(data);
+
+    tokio::time::timeout(MASK_RELAY_TIMEOUT, consume_client_data(reader, usize::MAX))
+        .await
+        .expect("consume_client_data did not complete for fast EOF reader");
+}
+
+#[tokio::test]
+async fn io_error_terminates_cleanly() {
+    struct ErrReader;
+
+    impl AsyncRead for ErrReader {
+        fn poll_read(
+            self: Pin<&mut Self>,
+            _cx: &mut Context<'_>,
+            _buf: &mut ReadBuf<'_>,
+        ) -> Poll<std::io::Result<()>> {
+            Poll::Ready(Err(std::io::Error::new(
+                std::io::ErrorKind::ConnectionReset,
+                "simulated reset",
+            )))
+        }
+    }
+
+    tokio::time::timeout(MASK_RELAY_TIMEOUT, consume_client_data(ErrReader, usize::MAX))
+        .await
+        .expect("consume_client_data did not return on I/O error");
+}

src/proxy/tests/masking_consume_stress_adversarial_tests.rs

@@ -0,0 +1,64 @@
+use super::*;
+use std::pin::Pin;
+use std::task::{Context, Poll};
+use std::time::Instant;
+use tokio::io::{AsyncRead, ReadBuf};
+use tokio::task::JoinSet;
+
+struct OneByteThenStall {
+    sent: bool,
+}
+
+impl AsyncRead for OneByteThenStall {
+    fn poll_read(
+        mut self: Pin<&mut Self>,
+        _cx: &mut Context<'_>,
+        buf: &mut ReadBuf<'_>,
+    ) -> Poll<std::io::Result<()>> {
+        if !self.sent {
+            self.sent = true;
+            buf.put_slice(&[0xAA]);
+            Poll::Ready(Ok(()))
+        } else {
+            Poll::Pending
+        }
+    }
+}
+
+#[tokio::test]
+async fn consume_stall_stress_finishes_within_idle_budget() {
+    let mut set = JoinSet::new();
+    let started = Instant::now();
+
+    for _ in 0..64 {
+        set.spawn(async {
+            tokio::time::timeout(
+                MASK_RELAY_TIMEOUT,
+                consume_client_data(OneByteThenStall { sent: false }, usize::MAX),
+            )
+            .await
+            .expect("consume_client_data exceeded relay timeout under stall load");
+        });
+    }
+
+    while let Some(res) = set.join_next().await {
+        res.unwrap();
+    }
+
+    // Under test constants idle=100ms, relay=200ms. 64 concurrent tasks stalling
+    // for 100ms should complete well under a strict 600ms boundary.
+    assert!(
+        started.elapsed() < MASK_RELAY_TIMEOUT * 3,
+        "stall stress batch completed too slowly; possible async executor starvation or head-of-line blocking"
+    );
+}
+
+#[tokio::test]
+async fn consume_zero_cap_returns_immediately() {
+    let started = Instant::now();
+    consume_client_data(tokio::io::empty(), 0).await;
+    assert!(
+        started.elapsed() < MASK_RELAY_IDLE_TIMEOUT,
+        "zero byte cap must return immediately"
+    );
+}

src/proxy/tests/masking_extended_attack_surface_security_tests.rs

@@ -0,0 +1,217 @@
+use super::*;
+use tokio::io::{AsyncWriteExt, duplex};
+use tokio::time::{Duration, Instant, timeout};
+
+fn make_self_target_config(
+    timing_normalization_enabled: bool,
+    floor_ms: u64,
+    ceiling_ms: u64,
+    beobachten_enabled: bool,
+) -> ProxyConfig {
+    let mut config = ProxyConfig::default();
+    config.general.beobachten = beobachten_enabled;
+    config.general.beobachten_minutes = 5;
+    config.censorship.mask = true;
+    config.censorship.mask_unix_sock = None;
+    config.censorship.mask_host = Some("127.0.0.1".to_string());
+    config.censorship.mask_port = 443;
+    config.censorship.mask_timing_normalization_enabled = timing_normalization_enabled;
+    config.censorship.mask_timing_normalization_floor_ms = floor_ms;
+    config.censorship.mask_timing_normalization_ceiling_ms = ceiling_ms;
+    config
+}
+
+async fn run_self_target_refusal(
+    config: ProxyConfig,
+    peer: SocketAddr,
+    initial: &'static [u8],
+) -> Duration {
+    let beobachten = BeobachtenStore::new();
+    let local_addr: SocketAddr = "127.0.0.1:443".parse().expect("valid local addr");
+
+    let (mut client, server) = duplex(1024);
+    let started = Instant::now();
+    let task = tokio::spawn(async move {
+        handle_bad_client(server, tokio::io::sink(), initial, peer, local_addr, &config, &beobachten)
+            .await;
+    });
+
+    client
+        .shutdown()
+        .await
+        .expect("client shutdown must succeed");
+
+    timeout(Duration::from_secs(3), task)
+        .await
+        .expect("self-target refusal must complete in bounded time")
+        .expect("self-target refusal task must not panic");
+
+    started.elapsed()
+}
+
+#[tokio::test]
+async fn positive_self_target_refusal_honors_normalization_floor() {
+    let config = make_self_target_config(true, 120, 120, false);
+    let peer: SocketAddr = "203.0.113.41:54041".parse().expect("valid peer");
+
+    let elapsed = run_self_target_refusal(config, peer, b"GET / HTTP/1.1\r\n\r\n").await;
+
+    assert!(
+        elapsed >= Duration::from_millis(110) && elapsed < Duration::from_millis(260),
+        "normalized self-target refusal must stay within expected envelope"
+    );
+}
+
+#[tokio::test]
+async fn negative_non_normalized_refusal_does_not_sleep_to_large_floor() {
+    let config = make_self_target_config(false, 240, 240, false);
+    let peer: SocketAddr = "203.0.113.42:54042".parse().expect("valid peer");
+
+    let elapsed = run_self_target_refusal(config, peer, b"GET / HTTP/1.1\r\n\r\n").await;
+
+    assert!(
+        elapsed < Duration::from_millis(180),
+        "non-normalized path must not inherit normalization floor delays"
+    );
+}
+
+#[tokio::test]
+async fn edge_ceiling_below_floor_uses_floor_fail_closed() {
+    let config = make_self_target_config(true, 140, 80, false);
+    let peer: SocketAddr = "203.0.113.43:54043".parse().expect("valid peer");
+
+    let elapsed = run_self_target_refusal(config, peer, b"GET / HTTP/1.1\r\n\r\n").await;
+
+    assert!(
+        elapsed >= Duration::from_millis(130) && elapsed < Duration::from_millis(280),
+        "ceiling<floor must clamp to floor to preserve deterministic normalization"
+    );
+}
+
+#[tokio::test(flavor = "multi_thread", worker_threads = 4)]
+async fn adversarial_blackhat_parallel_probes_remain_bounded_and_uniform() {
+    let workers = 24usize;
+    let mut tasks = Vec::with_capacity(workers);
+
+    for idx in 0..workers {
+        tasks.push(tokio::spawn(async move {
+            let cfg = make_self_target_config(true, 110, 140, false);
+            let peer: SocketAddr = format!("203.0.113.50:{}", 54100 + idx as u16)
+                .parse()
+                .expect("valid peer");
+            run_self_target_refusal(cfg, peer, b"GET /x HTTP/1.1\r\n\r\n").await
+        }));
+    }
+
+    let mut min = Duration::from_secs(60);
+    let mut max = Duration::from_millis(0);
+    for task in tasks {
+        let elapsed = task.await.expect("probe task must not panic");
+        if elapsed < min {
+            min = elapsed;
+        }
+        if elapsed > max {
+            max = elapsed;
+        }
+        assert!(
+            elapsed >= Duration::from_millis(100) && elapsed < Duration::from_millis(320),
+            "parallel probe latency must stay bounded under normalization"
+        );
+    }
+
+    assert!(
+        max.saturating_sub(min) <= Duration::from_millis(130),
+        "normalization should limit path variance across adversarial parallel probes"
+    );
+}
+
+#[tokio::test]
+async fn integration_beobachten_records_probe_classification_on_refusal() {
+    let config = make_self_target_config(false, 0, 0, true);
+    let peer: SocketAddr = "198.51.100.71:55071".parse().expect("valid peer");
+    let local_addr: SocketAddr = "127.0.0.1:443".parse().expect("valid local addr");
+    let beobachten = BeobachtenStore::new();
+
+    let (mut client, server) = duplex(1024);
+    let task = tokio::spawn(async move {
+        handle_bad_client(
+            server,
+            tokio::io::sink(),
+            b"GET /classified HTTP/1.1\r\nHost: demo\r\n\r\n",
+            peer,
+            local_addr,
+            &config,
+            &beobachten,
+        )
+        .await;
+
+        beobachten.snapshot_text(Duration::from_secs(60))
+    });
+
+    client
+        .shutdown()
+        .await
+        .expect("client shutdown must succeed");
+
+    let snapshot = timeout(Duration::from_secs(3), task)
+        .await
+        .expect("integration task must complete")
+        .expect("integration task must not panic");
+
+    assert!(snapshot.contains("[HTTP]"));
+    assert!(snapshot.contains("198.51.100.71-1"));
+}
+
+#[tokio::test]
+async fn light_fuzz_timing_configuration_matrix_is_bounded() {
+    let mut seed = 0xA17E_55AA_2026_0323u64;
+
+    for case in 0..48u64 {
+        seed ^= seed << 7;
+        seed ^= seed >> 9;
+        seed ^= seed << 8;
+
+        let enabled = (seed & 1) == 0;
+        let floor = (seed >> 8) % 180;
+        let ceiling = (seed >> 24) % 180;
+        let config = make_self_target_config(enabled, floor, ceiling, false);
+        let peer: SocketAddr = format!("203.0.113.90:{}", 56000 + (case as u16))
+            .parse()
+            .expect("valid peer");
+
+        let elapsed = run_self_target_refusal(config, peer, b"HEAD /h HTTP/1.1\r\n\r\n").await;
+
+        assert!(
+            elapsed < Duration::from_millis(420),
+            "fuzz case must stay bounded and never hang"
+        );
+    }
+}
+
+#[tokio::test(flavor = "multi_thread", worker_threads = 4)]
+async fn stress_high_fanout_self_target_refusal_no_deadlock_or_timeout() {
+    let workers = 64usize;
+    let mut tasks = Vec::with_capacity(workers);
+
+    for idx in 0..workers {
+        tasks.push(tokio::spawn(async move {
+            let config = make_self_target_config(false, 0, 0, false);
+            let peer: SocketAddr = format!("198.51.100.200:{}", 57000 + idx as u16)
+                .parse()
+                .expect("valid peer");
+            run_self_target_refusal(config, peer, b"GET /stress HTTP/1.1\r\n\r\n").await
+        }));
+    }
+
+    timeout(Duration::from_secs(5), async {
+        for task in tasks {
+            let elapsed = task.await.expect("stress task must not panic");
+            assert!(
+                elapsed < Duration::from_millis(260),
+                "stress refusal must remain bounded without normalization"
+            );
+        }
+    })
+    .await
+    .expect("high-fanout refusal workload must complete without deadlock");
+}

src/proxy/tests/masking_http2_preface_integration_security_tests.rs

@@ -0,0 +1,55 @@
+use super::*;
+use tokio::net::TcpListener;
+use tokio::time::Duration;
+
+#[tokio::test]
+async fn http2_preface_is_forwarded_and_recorded_as_http() {
+    let listener = TcpListener::bind("127.0.0.1:0").await.unwrap();
+    let backend_addr = listener.local_addr().unwrap();
+    let preface = b"PRI * HTTP/2.0\r\n\r\nSM\r\n\r\n".to_vec();
+
+    let accept_task = tokio::spawn({
+        let preface = preface.clone();
+        async move {
+            let (mut stream, _) = listener.accept().await.unwrap();
+            let mut received = vec![0u8; preface.len()];
+            stream.read_exact(&mut received).await.unwrap();
+            assert_eq!(received, preface);
+        }
+    });
+
+    let mut config = ProxyConfig::default();
+    config.general.beobachten = true;
+    config.general.beobachten_minutes = 1;
+    config.censorship.mask = true;
+    config.censorship.mask_host = Some("127.0.0.1".to_string());
+    config.censorship.mask_port = backend_addr.port();
+    config.censorship.mask_unix_sock = None;
+    config.censorship.mask_proxy_protocol = 0;
+
+    let peer: SocketAddr = "198.51.100.130:54130".parse().unwrap();
+    let local_addr: SocketAddr = "127.0.0.1:443".parse().unwrap();
+    let (client_reader, _client_writer) = tokio::io::duplex(512);
+    let (_client_visible_reader, client_visible_writer) = tokio::io::duplex(512);
+    let beobachten = BeobachtenStore::new();
+
+    handle_bad_client(
+        client_reader,
+        client_visible_writer,
+        &preface,
+        peer,
+        local_addr,
+        &config,
+        &beobachten,
+    )
+    .await;
+
+    tokio::time::timeout(Duration::from_secs(2), accept_task)
+        .await
+        .unwrap()
+        .unwrap();
+
+    let snapshot = beobachten.snapshot_text(Duration::from_secs(60));
+    assert!(snapshot.contains("[HTTP]"));
+    assert!(snapshot.contains("198.51.100.130-1"));
+}

src/proxy/tests/masking_http2_probe_classification_security_tests.rs

@@ -0,0 +1,92 @@
+use super::*;
+
+#[test]
+fn full_http2_preface_classified_as_http_probe() {
+    let preface = b"PRI * HTTP/2.0\r\n\r\nSM\r\n\r\n";
+    assert!(
+        is_http_probe(preface),
+        "HTTP/2 connection preface must be classified as HTTP probe"
+    );
+}
+
+#[test]
+fn partial_http2_preface_3_bytes_classified() {
+    assert!(
+        is_http_probe(b"PRI"),
+        "3-byte HTTP/2 preface prefix must be classified"
+    );
+}
+
+#[test]
+fn partial_http2_preface_2_bytes_classified() {
+    assert!(
+        is_http_probe(b"PR"),
+        "2-byte HTTP/2 preface prefix must be classified"
+    );
+}
+
+#[test]
+fn existing_http1_methods_unaffected() {
+    for prefix in [
+        b"GET / HTTP/1.1\r\n".as_ref(),
+        b"POST /api HTTP/1.1\r\n".as_ref(),
+        b"CONNECT example.com:443 HTTP/1.1\r\n".as_ref(),
+        b"TRACE / HTTP/1.1\r\n".as_ref(),
+        b"PATCH / HTTP/1.1\r\n".as_ref(),
+    ] {
+        assert!(is_http_probe(prefix));
+    }
+}
+
+#[test]
+fn non_http_data_not_classified() {
+    for data in [
+        b"\x16\x03\x01\x00\xf1".as_ref(),
+        b"SSH-2.0-OpenSSH_8.9\r\n".as_ref(),
+        b"\x00\x01\x02\x03".as_ref(),
+        b"".as_ref(),
+        b"P".as_ref(),
+    ] {
+        assert!(!is_http_probe(data));
+    }
+}
+
+#[test]
+fn light_fuzz_non_http_prefixes_not_misclassified() {
+    // Deterministic pseudo-fuzz to exercise classifier edges while avoiding
+    // known HTTP method and partial windows.
+    let mut x = 0x1234_5678u32;
+    for _ in 0..1024 {
+        x = x.wrapping_mul(1664525).wrapping_add(1013904223);
+        let len = 4 + ((x >> 8) as usize % 12);
+        let mut data = vec![0u8; len];
+        for byte in &mut data {
+            x = x.wrapping_mul(1664525).wrapping_add(1013904223);
+            *byte = (x & 0xFF) as u8;
+        }
+
+        if [
+            b"GET ".as_ref(),
+            b"POST".as_ref(),
+            b"HEAD".as_ref(),
+            b"PUT ".as_ref(),
+            b"DELETE".as_ref(),
+            b"OPTIONS".as_ref(),
+            b"CONNECT".as_ref(),
+            b"TRACE".as_ref(),
+            b"PATCH".as_ref(),
+            b"PRI ".as_ref(),
+        ]
+        .iter()
+        .any(|m| data.starts_with(m))
+        {
+            continue;
+        }
+
+        assert!(
+            !is_http_probe(&data),
+            "non-http pseudo-fuzz input misclassified: {:?}",
+            &data[..data.len().min(8)]
+        );
+    }
+}

src/proxy/tests/masking_http_probe_boundary_security_tests.rs

@@ -0,0 +1,79 @@
+use super::*;
+
+#[test]
+fn exact_four_byte_http_tokens_are_classified() {
+    for token in [b"GET ".as_ref(), b"POST".as_ref(), b"HEAD".as_ref(), b"PUT ".as_ref(), b"PRI ".as_ref()] {
+        assert!(
+            is_http_probe(token),
+            "exact 4-byte token must be classified as HTTP probe: {:?}",
+            token
+        );
+    }
+}
+
+#[test]
+fn exact_four_byte_non_http_tokens_are_not_classified() {
+    for token in [
+        b"GEX ".as_ref(),
+        b"POXT".as_ref(),
+        b"HEA/".as_ref(),
+        b"PU\0 ".as_ref(),
+        b"PRI/".as_ref(),
+    ] {
+        assert!(
+            !is_http_probe(token),
+            "non-HTTP 4-byte token must not be classified: {:?}",
+            token
+        );
+    }
+}
+
+#[test]
+fn detect_client_type_keeps_http_label_for_minimal_four_byte_http_prefixes() {
+    assert_eq!(detect_client_type(b"GET "), "HTTP");
+    assert_eq!(detect_client_type(b"PRI "), "HTTP");
+}
+
+#[test]
+fn exact_long_http_tokens_are_classified() {
+    for token in [b"CONNECT".as_ref(), b"TRACE".as_ref(), b"PATCH".as_ref()] {
+        assert!(
+            is_http_probe(token),
+            "exact long HTTP token must be classified as HTTP probe: {:?}",
+            token
+        );
+    }
+}
+
+#[test]
+fn detect_client_type_keeps_http_label_for_exact_long_http_tokens() {
+    assert_eq!(detect_client_type(b"CONNECT"), "HTTP");
+    assert_eq!(detect_client_type(b"TRACE"), "HTTP");
+    assert_eq!(detect_client_type(b"PATCH"), "HTTP");
+}
+
+#[test]
+fn light_fuzz_four_byte_ascii_noise_not_misclassified() {
+    // Deterministic pseudo-fuzz over 4-byte printable ASCII inputs.
+    let mut x = 0xA17C_93E5u32;
+    for _ in 0..2048 {
+        let mut token = [0u8; 4];
+        for byte in &mut token {
+            x = x.wrapping_mul(1664525).wrapping_add(1013904223);
+            *byte = 32 + ((x & 0x3F) as u8); // printable ASCII subset
+        }
+
+        if [b"GET ", b"POST", b"HEAD", b"PUT ", b"PRI "]
+            .iter()
+            .any(|m| token.as_slice() == *m)
+        {
+            continue;
+        }
+
+        assert!(
+            !is_http_probe(&token),
+            "pseudo-fuzz noise misclassified as HTTP probe: {:?}",
+            token
+        );
+    }
+}

src/proxy/tests/masking_interface_cache_concurrency_security_tests.rs

@@ -0,0 +1,41 @@
+#![cfg(unix)]
+
+use super::*;
+use std::sync::{Mutex, OnceLock};
+use tokio::sync::Barrier;
+
+fn interface_cache_test_lock() -> &'static Mutex<()> {
+    static LOCK: OnceLock<Mutex<()>> = OnceLock::new();
+    LOCK.get_or_init(|| Mutex::new(()))
+}
+
+#[tokio::test(flavor = "multi_thread", worker_threads = 4)]
+async fn adversarial_parallel_cold_miss_performs_single_interface_refresh() {
+    let _guard = interface_cache_test_lock()
+        .lock()
+        .unwrap_or_else(|poison| poison.into_inner());
+    reset_local_interface_enumerations_for_tests();
+
+    let local_addr: SocketAddr = "0.0.0.0:443".parse().expect("valid local addr");
+    let workers = 32usize;
+    let barrier = std::sync::Arc::new(Barrier::new(workers));
+    let mut tasks = Vec::with_capacity(workers);
+
+    for _ in 0..workers {
+        let barrier = std::sync::Arc::clone(&barrier);
+        tasks.push(tokio::spawn(async move {
+            barrier.wait().await;
+            is_mask_target_local_listener_async("127.0.0.1", 443, local_addr, None).await
+        }));
+    }
+
+    for task in tasks {
+        let _ = task.await.expect("parallel cache task must not panic");
+    }
+
+    assert_eq!(
+        local_interface_enumerations_for_tests(),
+        1,
+        "parallel cold misses must coalesce into a single interface enumeration"
+    );
+}

src/proxy/tests/masking_interface_cache_defense_in_depth_security_tests.rs

@@ -0,0 +1,51 @@
+#![cfg(unix)]
+
+use super::*;
+
+#[test]
+fn defense_in_depth_empty_refresh_preserves_previous_non_empty_interfaces() {
+    let previous = vec![
+        "192.168.100.7"
+            .parse::<IpAddr>()
+            .expect("must parse interface ip"),
+    ];
+    let refreshed = Vec::new();
+
+    let next = choose_interface_snapshot(&previous, refreshed);
+
+    assert_eq!(
+        next, previous,
+        "empty refresh should preserve previous non-empty snapshot to avoid fail-open loop-guard regressions"
+    );
+}
+
+#[test]
+fn defense_in_depth_non_empty_refresh_replaces_previous_snapshot() {
+    let previous = vec![
+        "192.168.100.7"
+            .parse::<IpAddr>()
+            .expect("must parse interface ip"),
+    ];
+    let refreshed = vec![
+        "10.55.0.3"
+            .parse::<IpAddr>()
+            .expect("must parse refreshed interface ip"),
+    ];
+
+    let next = choose_interface_snapshot(&previous, refreshed.clone());
+
+    assert_eq!(next, refreshed);
+}
+
+#[test]
+fn defense_in_depth_empty_refresh_keeps_empty_when_no_previous_snapshot_exists() {
+    let previous = Vec::new();
+    let refreshed = Vec::new();
+
+    let next = choose_interface_snapshot(&previous, refreshed);
+
+    assert!(
+        next.is_empty(),
+        "empty refresh with no previous snapshot should remain empty"
+    );
+}

src/proxy/tests/masking_interface_cache_security_tests.rs

@@ -0,0 +1,46 @@
+#![cfg(unix)]
+
+use super::*;
+use std::sync::{Mutex, OnceLock};
+
+fn interface_cache_test_lock() -> &'static Mutex<()> {
+    static LOCK: OnceLock<Mutex<()>> = OnceLock::new();
+    LOCK.get_or_init(|| Mutex::new(()))
+}
+
+#[tokio::test]
+async fn tdd_repeated_local_listener_checks_do_not_repeat_interface_enumeration_within_window() {
+    let _guard = interface_cache_test_lock()
+        .lock()
+        .unwrap_or_else(|poison| poison.into_inner());
+    reset_local_interface_enumerations_for_tests();
+
+    let local_addr: SocketAddr = "0.0.0.0:443".parse().expect("valid local addr");
+
+    let _ = is_mask_target_local_listener_async("127.0.0.1", 443, local_addr, None).await;
+    let _ = is_mask_target_local_listener_async("127.0.0.1", 443, local_addr, None).await;
+
+    assert_eq!(
+        local_interface_enumerations_for_tests(),
+        1,
+        "interface enumeration must be cached across repeated bad-client checks"
+    );
+}
+
+#[tokio::test]
+async fn tdd_non_local_port_short_circuit_does_not_enumerate_interfaces() {
+    let _guard = interface_cache_test_lock()
+        .lock()
+        .unwrap_or_else(|poison| poison.into_inner());
+    reset_local_interface_enumerations_for_tests();
+
+    let local_addr: SocketAddr = "0.0.0.0:443".parse().expect("valid local addr");
+    let is_local = is_mask_target_local_listener_async("127.0.0.1", 8443, local_addr, None).await;
+
+    assert!(!is_local, "different port must not be treated as local listener");
+    assert_eq!(
+        local_interface_enumerations_for_tests(),
+        0,
+        "port mismatch should bypass interface enumeration entirely"
+    );
+}

src/proxy/tests/masking_offline_target_redteam_expected_fail_tests.rs

@@ -0,0 +1,178 @@
+use super::*;
+use std::net::{SocketAddr, TcpListener as StdTcpListener};
+use tokio::io::{AsyncWriteExt, duplex};
+use tokio::time::{Duration, Instant};
+
+fn closed_local_port() -> u16 {
+    let listener = StdTcpListener::bind("127.0.0.1:0").unwrap();
+    let port = listener.local_addr().unwrap().port();
+    drop(listener);
+    port
+}
+
+#[tokio::test]
+#[ignore = "red-team expected-fail: offline mask target keeps bad-client socket alive before consume timeout boundary"]
+async fn redteam_offline_target_should_drop_idle_client_early() {
+    let (client_read, mut client_write) = duplex(1024);
+
+    let mut cfg = ProxyConfig::default();
+    cfg.general.beobachten = false;
+    cfg.censorship.mask = true;
+    cfg.censorship.mask_unix_sock = None;
+    cfg.censorship.mask_host = Some("127.0.0.1".to_string());
+    cfg.censorship.mask_port = closed_local_port();
+    cfg.censorship.mask_timing_normalization_enabled = false;
+
+    let local_addr: SocketAddr = "127.0.0.1:443".parse().unwrap();
+    let peer_addr: SocketAddr = "192.0.2.50:5000".parse().unwrap();
+    let beobachten = BeobachtenStore::new();
+
+    let handler = tokio::spawn(async move {
+        handle_bad_client(
+            client_read,
+            tokio::io::sink(),
+            b"GET / HTTP/1.1\r\n\r\n",
+            peer_addr,
+            local_addr,
+            &cfg,
+            &beobachten,
+        )
+        .await;
+    });
+
+    tokio::time::sleep(Duration::from_millis(150)).await;
+    let write_res = client_write.write_all(b"probe-should-be-closed").await;
+    assert!(
+        write_res.is_err(),
+        "offline target path still keeps client writable before consume timeout"
+    );
+
+    handler.abort();
+}
+
+#[tokio::test]
+#[ignore = "red-team expected-fail: proxy should mimic immediate RST-like close when target is offline"]
+async fn redteam_offline_target_should_not_sleep_to_mask_refusal() {
+    let (client_read, mut client_write) = duplex(1024);
+
+    let mut cfg = ProxyConfig::default();
+    cfg.general.beobachten = false;
+    cfg.censorship.mask = true;
+    cfg.censorship.mask_unix_sock = None;
+    cfg.censorship.mask_host = Some("127.0.0.1".to_string());
+    cfg.censorship.mask_port = closed_local_port();
+    cfg.censorship.mask_timing_normalization_enabled = false;
+
+    let local_addr: SocketAddr = "127.0.0.1:443".parse().unwrap();
+    let peer_addr: SocketAddr = "192.0.2.51:5000".parse().unwrap();
+    let beobachten = BeobachtenStore::new();
+
+    let started = Instant::now();
+    let handler = tokio::spawn(async move {
+        handle_bad_client(
+            client_read,
+            tokio::io::sink(),
+            b"\x16\x03\x01\x00\x05hello",
+            peer_addr,
+            local_addr,
+            &cfg,
+            &beobachten,
+        )
+        .await;
+    });
+
+    client_write.shutdown().await.unwrap();
+    let _ = handler.await;
+    let elapsed = started.elapsed();
+
+    assert!(
+        elapsed < Duration::from_millis(10),
+        "offline target path still applies coarse masking sleep and is fingerprintable"
+    );
+}
+
+#[tokio::test]
+#[ignore = "red-team expected-fail: refusal path should remain below strict latency envelope under burst"]
+async fn redteam_offline_refusal_burst_timing_spread_should_be_tight() {
+    let mut samples = Vec::new();
+
+    for i in 0..12u16 {
+        let (client_read, mut client_write) = duplex(1024);
+        let mut cfg = ProxyConfig::default();
+        cfg.general.beobachten = false;
+        cfg.censorship.mask = true;
+        cfg.censorship.mask_unix_sock = None;
+        cfg.censorship.mask_host = Some("127.0.0.1".to_string());
+        cfg.censorship.mask_port = closed_local_port();
+        cfg.censorship.mask_timing_normalization_enabled = false;
+
+        let local_addr: SocketAddr = "127.0.0.1:443".parse().unwrap();
+        let peer_addr: SocketAddr = format!("192.0.2.52:{}", 5100 + i).parse().unwrap();
+        let beobachten = BeobachtenStore::new();
+
+        let started = Instant::now();
+        let handler = tokio::spawn(async move {
+            handle_bad_client(
+                client_read,
+                tokio::io::sink(),
+                b"GET / HTTP/1.1\r\n\r\n",
+                peer_addr,
+                local_addr,
+                &cfg,
+                &beobachten,
+            )
+            .await;
+        });
+
+        client_write.shutdown().await.unwrap();
+        let _ = handler.await;
+        samples.push(started.elapsed());
+    }
+
+    let min = samples.iter().copied().min().unwrap_or_default();
+    let max = samples.iter().copied().max().unwrap_or_default();
+    let spread = max.saturating_sub(min);
+
+    assert!(
+        spread <= Duration::from_millis(5),
+        "offline refusal timing spread too wide for strict red-team envelope: {:?}",
+        spread
+    );
+}
+
+#[tokio::test]
+#[ignore = "manual red-team: host resolver failure should complete without panic"]
+async fn redteam_dns_resolution_failure_must_not_panic() {
+    let (client_read, mut client_write) = duplex(1024);
+
+    let mut cfg = ProxyConfig::default();
+    cfg.general.beobachten = false;
+    cfg.censorship.mask = true;
+    cfg.censorship.mask_unix_sock = None;
+    cfg.censorship.mask_host = Some("this.domain.definitely.does.not.exist.invalid".to_string());
+    cfg.censorship.mask_port = 443;
+
+    let local_addr: SocketAddr = "127.0.0.1:443".parse().unwrap();
+    let peer_addr: SocketAddr = "192.0.2.99:5999".parse().unwrap();
+    let beobachten = BeobachtenStore::new();
+
+    let handler = tokio::spawn(async move {
+        handle_bad_client(
+            client_read,
+            tokio::io::sink(),
+            b"GET / HTTP/1.1\r\n\r\n",
+            peer_addr,
+            local_addr,
+            &cfg,
+            &beobachten,
+        )
+        .await;
+    });
+
+    client_write.shutdown().await.unwrap();
+    let result = tokio::time::timeout(Duration::from_secs(2), handler).await;
+    assert!(
+        result.is_ok(),
+        "dns failure path stalled or panicked instead of terminating"
+    );
+}

src/proxy/tests/masking_padding_timeout_adversarial_tests.rs

@@ -0,0 +1,51 @@
+use super::*;
+use std::pin::Pin;
+use std::task::{Context, Poll};
+use std::time::Instant;
+use tokio::io::AsyncWrite;
+
+struct NeverWritable;
+
+impl AsyncWrite for NeverWritable {
+    fn poll_write(
+        self: Pin<&mut Self>,
+        _cx: &mut Context<'_>,
+        _buf: &[u8],
+    ) -> Poll<std::io::Result<usize>> {
+        Poll::Pending
+    }
+
+    fn poll_flush(self: Pin<&mut Self>, _cx: &mut Context<'_>) -> Poll<std::io::Result<()>> {
+        Poll::Pending
+    }
+
+    fn poll_shutdown(self: Pin<&mut Self>, _cx: &mut Context<'_>) -> Poll<std::io::Result<()>> {
+        Poll::Ready(Ok(()))
+    }
+}
+
+#[tokio::test]
+async fn shape_padding_returns_before_global_mask_timeout_on_blocked_writer() {
+    let mut writer = NeverWritable;
+    let started = Instant::now();
+
+    maybe_write_shape_padding(&mut writer, 1, true, 256, 4096, false, 0, false).await;
+
+    assert!(
+        started.elapsed() <= MASK_TIMEOUT + std::time::Duration::from_millis(30),
+        "shape padding blocked past timeout budget"
+    );
+}
+
+#[tokio::test]
+async fn shape_padding_with_non_http_blur_disabled_at_cap_writes_nothing() {
+    let mut output = Vec::new();
+    {
+        let mut writer = tokio::io::BufWriter::new(&mut output);
+        maybe_write_shape_padding(&mut writer, 4096, true, 64, 4096, false, 128, false).await;
+        use tokio::io::AsyncWriteExt;
+        writer.flush().await.unwrap();
+    }
+
+    assert!(output.is_empty());
+}

src/proxy/tests/masking_production_cap_regression_security_tests.rs

@@ -0,0 +1,289 @@
+use super::*;
+use std::pin::Pin;
+use std::sync::Arc;
+use std::sync::atomic::{AtomicUsize, Ordering};
+use std::task::{Context, Poll};
+use tokio::io::{AsyncRead, AsyncWrite};
+use tokio::time::{Duration, Instant, timeout};
+
+const PROD_CAP_BYTES: usize = 5 * 1024 * 1024;
+
+struct FinitePatternReader {
+    remaining: usize,
+    chunk: usize,
+    read_calls: Arc<AtomicUsize>,
+}
+
+impl FinitePatternReader {
+    fn new(total: usize, chunk: usize, read_calls: Arc<AtomicUsize>) -> Self {
+        Self {
+            remaining: total,
+            chunk,
+            read_calls,
+        }
+    }
+}
+
+impl AsyncRead for FinitePatternReader {
+    fn poll_read(
+        mut self: Pin<&mut Self>,
+        _cx: &mut Context<'_>,
+        buf: &mut tokio::io::ReadBuf<'_>,
+    ) -> Poll<std::io::Result<()>> {
+        self.read_calls.fetch_add(1, Ordering::Relaxed);
+
+        if self.remaining == 0 {
+            return Poll::Ready(Ok(()));
+        }
+
+        let take = self.remaining.min(self.chunk).min(buf.remaining());
+        if take == 0 {
+            return Poll::Ready(Ok(()));
+        }
+
+        let fill = vec![0x5Au8; take];
+        buf.put_slice(&fill);
+        self.remaining -= take;
+        Poll::Ready(Ok(()))
+    }
+}
+
+#[derive(Default)]
+struct CountingWriter {
+    written: usize,
+}
+
+impl AsyncWrite for CountingWriter {
+    fn poll_write(
+        mut self: Pin<&mut Self>,
+        _cx: &mut Context<'_>,
+        buf: &[u8],
+    ) -> Poll<std::io::Result<usize>> {
+        self.written = self.written.saturating_add(buf.len());
+        Poll::Ready(Ok(buf.len()))
+    }
+
+    fn poll_flush(
+        self: Pin<&mut Self>,
+        _cx: &mut Context<'_>,
+    ) -> Poll<std::io::Result<()>> {
+        Poll::Ready(Ok(()))
+    }
+
+    fn poll_shutdown(
+        self: Pin<&mut Self>,
+        _cx: &mut Context<'_>,
+    ) -> Poll<std::io::Result<()>> {
+        Poll::Ready(Ok(()))
+    }
+}
+
+struct NeverReadyReader;
+
+impl AsyncRead for NeverReadyReader {
+    fn poll_read(
+        self: Pin<&mut Self>,
+        _cx: &mut Context<'_>,
+        _buf: &mut tokio::io::ReadBuf<'_>,
+    ) -> Poll<std::io::Result<()>> {
+        Poll::Pending
+    }
+}
+
+struct BudgetProbeReader {
+    remaining: usize,
+    total_read: Arc<AtomicUsize>,
+}
+
+impl BudgetProbeReader {
+    fn new(total: usize, total_read: Arc<AtomicUsize>) -> Self {
+        Self {
+            remaining: total,
+            total_read,
+        }
+    }
+}
+
+impl AsyncRead for BudgetProbeReader {
+    fn poll_read(
+        mut self: Pin<&mut Self>,
+        _cx: &mut Context<'_>,
+        buf: &mut tokio::io::ReadBuf<'_>,
+    ) -> Poll<std::io::Result<()>> {
+        if self.remaining == 0 {
+            return Poll::Ready(Ok(()));
+        }
+
+        let take = self.remaining.min(buf.remaining());
+        if take == 0 {
+            return Poll::Ready(Ok(()));
+        }
+
+        let fill = vec![0xA5u8; take];
+        buf.put_slice(&fill);
+        self.remaining -= take;
+        self.total_read.fetch_add(take, Ordering::Relaxed);
+        Poll::Ready(Ok(()))
+    }
+}
+
+#[tokio::test]
+async fn positive_copy_with_production_cap_stops_exactly_at_budget() {
+    let read_calls = Arc::new(AtomicUsize::new(0));
+    let mut reader = FinitePatternReader::new(PROD_CAP_BYTES + (256 * 1024), 4096, read_calls);
+    let mut writer = CountingWriter::default();
+
+    let outcome = copy_with_idle_timeout(&mut reader, &mut writer, PROD_CAP_BYTES, true).await;
+
+    assert_eq!(
+        outcome.total, PROD_CAP_BYTES,
+        "copy path must stop at explicit production cap"
+    );
+    assert_eq!(writer.written, PROD_CAP_BYTES);
+    assert!(
+        !outcome.ended_by_eof,
+        "byte-cap stop must not be misclassified as EOF"
+    );
+}
+
+#[tokio::test]
+async fn negative_consume_with_zero_cap_performs_no_reads() {
+    let read_calls = Arc::new(AtomicUsize::new(0));
+    let reader = FinitePatternReader::new(1024, 64, Arc::clone(&read_calls));
+
+    consume_client_data_with_timeout_and_cap(reader, 0).await;
+
+    assert_eq!(
+        read_calls.load(Ordering::Relaxed),
+        0,
+        "zero cap must return before reading attacker-controlled bytes"
+    );
+}
+
+#[tokio::test]
+async fn edge_copy_below_cap_reports_eof_without_overread() {
+    let read_calls = Arc::new(AtomicUsize::new(0));
+    let payload = 73 * 1024;
+    let mut reader = FinitePatternReader::new(payload, 3072, read_calls);
+    let mut writer = CountingWriter::default();
+
+    let outcome = copy_with_idle_timeout(&mut reader, &mut writer, PROD_CAP_BYTES, true).await;
+
+    assert_eq!(outcome.total, payload);
+    assert_eq!(writer.written, payload);
+    assert!(
+        outcome.ended_by_eof,
+        "finite upstream below cap must terminate via EOF path"
+    );
+}
+
+#[tokio::test]
+async fn adversarial_blackhat_never_ready_reader_is_bounded_by_timeout_guards() {
+    let started = Instant::now();
+
+    consume_client_data_with_timeout_and_cap(NeverReadyReader, PROD_CAP_BYTES).await;
+
+    assert!(
+        started.elapsed() < Duration::from_millis(350),
+        "never-ready reader must be bounded by idle/relay timeout protections"
+    );
+}
+
+#[tokio::test]
+async fn integration_consume_path_honors_production_cap_for_large_payload() {
+    let read_calls = Arc::new(AtomicUsize::new(0));
+    let reader = FinitePatternReader::new(PROD_CAP_BYTES + (1024 * 1024), 8192, read_calls);
+
+    let bounded = timeout(
+        Duration::from_millis(350),
+        consume_client_data_with_timeout_and_cap(reader, PROD_CAP_BYTES),
+    )
+    .await;
+
+    assert!(
+        bounded.is_ok(),
+        "consume path with production cap must finish within bounded time"
+    );
+}
+
+#[tokio::test]
+async fn adversarial_consume_path_never_reads_beyond_declared_byte_cap() {
+    let byte_cap = 5usize;
+    let total_read = Arc::new(AtomicUsize::new(0));
+    let reader = BudgetProbeReader::new(256 * 1024, Arc::clone(&total_read));
+
+    consume_client_data_with_timeout_and_cap(reader, byte_cap).await;
+
+    assert!(
+        total_read.load(Ordering::Relaxed) <= byte_cap,
+        "consume path must not read more than configured byte cap"
+    );
+}
+
+#[tokio::test]
+async fn light_fuzz_cap_and_payload_matrix_preserves_min_budget_invariant() {
+    let mut seed = 0x1234_5678_9ABC_DEF0u64;
+
+    for _case in 0..96u32 {
+        seed ^= seed << 7;
+        seed ^= seed >> 9;
+        seed ^= seed << 8;
+
+        let cap = ((seed & 0x3ffff) as usize).saturating_add(1);
+        let payload = ((seed.rotate_left(11) & 0x7ffff) as usize).saturating_add(1);
+        let chunk = (((seed >> 5) & 0x1fff) as usize).saturating_add(1);
+
+        let read_calls = Arc::new(AtomicUsize::new(0));
+        let mut reader = FinitePatternReader::new(payload, chunk, read_calls);
+        let mut writer = CountingWriter::default();
+
+        let outcome = copy_with_idle_timeout(&mut reader, &mut writer, cap, true).await;
+        let expected = payload.min(cap);
+
+        assert_eq!(
+            outcome.total, expected,
+            "copy total must match min(payload, cap) under fuzzed inputs"
+        );
+        assert_eq!(writer.written, expected);
+        if payload <= cap {
+            assert!(outcome.ended_by_eof);
+        } else {
+            assert!(!outcome.ended_by_eof);
+        }
+    }
+}
+
+#[tokio::test(flavor = "multi_thread", worker_threads = 4)]
+async fn stress_parallel_copy_tasks_with_production_cap_complete_without_leaks() {
+    let workers = 8usize;
+    let mut tasks = Vec::with_capacity(workers);
+
+    for idx in 0..workers {
+        tasks.push(tokio::spawn(async move {
+            let read_calls = Arc::new(AtomicUsize::new(0));
+            let mut reader = FinitePatternReader::new(
+                PROD_CAP_BYTES + (idx + 1) * 4096,
+                4096 + (idx * 257),
+                read_calls,
+            );
+            let mut writer = CountingWriter::default();
+            copy_with_idle_timeout(&mut reader, &mut writer, PROD_CAP_BYTES, true).await
+        }));
+    }
+
+    timeout(Duration::from_secs(3), async {
+        for task in tasks {
+            let outcome = task.await.expect("stress task must not panic");
+            assert_eq!(
+                outcome.total, PROD_CAP_BYTES,
+                "stress copy task must stay within production cap"
+            );
+            assert!(
+                !outcome.ended_by_eof,
+                "stress task should end due to cap, not EOF"
+            );
+        }
+    })
+    .await
+    .expect("stress suite must complete in bounded time");
+}

src/proxy/tests/masking_relay_guardrails_security_tests.rs

@@ -0,0 +1,105 @@
+use super::*;
+use tokio::io::{AsyncReadExt, AsyncWriteExt, duplex, sink};
+use tokio::time::{Duration, timeout};
+
+#[tokio::test]
+async fn relay_to_mask_enforces_masking_session_byte_cap() {
+    let initial = vec![0x16, 0x03, 0x01, 0x00, 0x01];
+    let extra = vec![0xAB; 96 * 1024];
+
+    let (client_reader, mut client_writer) = duplex(128 * 1024);
+    let (mask_read, _mask_read_peer) = duplex(1024);
+    let (mut mask_observer, mask_write) = duplex(256 * 1024);
+    let initial_for_task = initial.clone();
+
+    let relay = tokio::spawn(async move {
+        relay_to_mask(
+            client_reader,
+            sink(),
+            mask_read,
+            mask_write,
+            &initial_for_task,
+            false,
+            512,
+            4096,
+            false,
+            0,
+            false,
+            32 * 1024,
+        )
+        .await;
+    });
+
+    client_writer.write_all(&extra).await.unwrap();
+    client_writer.shutdown().await.unwrap();
+
+    timeout(Duration::from_secs(2), relay)
+        .await
+        .unwrap()
+        .unwrap();
+
+    let mut observed = Vec::new();
+    timeout(
+        Duration::from_secs(2),
+        mask_observer.read_to_end(&mut observed),
+    )
+    .await
+    .unwrap()
+    .unwrap();
+
+    // In this deterministic test, relay must stop exactly at the configured cap.
+    assert_eq!(
+        observed.len(),
+        initial.len() + (32 * 1024),
+        "masked relay must forward exactly up to the cap (observed={} initial={} cap={})",
+        observed.len(),
+        initial.len(),
+        32 * 1024
+    );
+}
+
+#[tokio::test]
+async fn relay_to_mask_propagates_client_half_close_without_waiting_for_other_direction_timeout() {
+    let initial = b"GET /half-close HTTP/1.1\r\n".to_vec();
+
+    let (client_reader, mut client_writer) = duplex(8 * 1024);
+    let (mask_read, _mask_read_peer) = duplex(8 * 1024);
+    let (mut mask_observer, mask_write) = duplex(8 * 1024);
+    let initial_for_task = initial.clone();
+
+    let relay = tokio::spawn(async move {
+        relay_to_mask(
+            client_reader,
+            sink(),
+            mask_read,
+            mask_write,
+            &initial_for_task,
+            false,
+            512,
+            4096,
+            false,
+            0,
+            false,
+            32 * 1024,
+        )
+        .await;
+    });
+
+    client_writer.shutdown().await.unwrap();
+
+    let mut observed = Vec::new();
+    timeout(
+        Duration::from_millis(80),
+        mask_observer.read_to_end(&mut observed),
+    )
+    .await
+    .expect("mask backend write side should be half-closed promptly")
+    .unwrap();
+
+    assert_eq!(&observed[..initial.len()], initial.as_slice());
+
+    timeout(Duration::from_secs(2), relay)
+        .await
+        .unwrap()
+        .unwrap();
+}

src/proxy/tests/masking_rng_hoist_perf_regression_tests.rs

@@ -0,0 +1,100 @@
+use super::*;
+use tokio::io::AsyncReadExt;
+use tokio::time::{Duration, timeout};
+
+async fn collect_padding(
+    total_sent: usize,
+    enabled: bool,
+    floor: usize,
+    cap: usize,
+    above_cap_blur: bool,
+    blur_max: usize,
+    aggressive: bool,
+) -> Vec<u8> {
+    let (mut tx, mut rx) = tokio::io::duplex(256 * 1024);
+
+    maybe_write_shape_padding(
+        &mut tx,
+        total_sent,
+        enabled,
+        floor,
+        cap,
+        above_cap_blur,
+        blur_max,
+        aggressive,
+    )
+    .await;
+
+    drop(tx);
+
+    let mut output = Vec::new();
+    timeout(Duration::from_secs(1), rx.read_to_end(&mut output))
+        .await
+        .expect("reading padded output timed out")
+        .expect("failed reading padded output");
+    output
+}
+
+#[tokio::test]
+async fn padding_output_is_not_all_zero() {
+    let output = collect_padding(1, true, 256, 4096, false, 0, false).await;
+
+    assert!(
+        output.len() >= 255,
+        "expected at least 255 padding bytes, got {}",
+        output.len()
+    );
+
+    let nonzero = output.iter().filter(|&&b| b != 0).count();
+    // In 255 bytes of uniform randomness, the expected number of zero bytes is ~1.
+    // A weak nonzero check can miss severe entropy collapse.
+    assert!(
+        nonzero >= 240,
+        "RNG output entropy collapsed, too many zero bytes: {} nonzero out of {}",
+        nonzero,
+        output.len(),
+    );
+}
+
+#[tokio::test]
+async fn padding_reaches_first_bucket_boundary() {
+    let output = collect_padding(1, true, 64, 4096, false, 0, false).await;
+    assert_eq!(output.len(), 63);
+}
+
+#[tokio::test]
+async fn disabled_padding_produces_no_output() {
+    let output = collect_padding(0, false, 256, 4096, false, 0, false).await;
+    assert!(output.is_empty());
+}
+
+#[tokio::test]
+async fn at_cap_without_blur_produces_no_output() {
+    let output = collect_padding(4096, true, 64, 4096, false, 0, false).await;
+    assert!(output.is_empty());
+}
+
+#[tokio::test]
+async fn above_cap_blur_is_positive_and_bounded_in_aggressive_mode() {
+    let output = collect_padding(4096, true, 64, 4096, true, 128, true).await;
+    assert!(!output.is_empty());
+    assert!(output.len() <= 128, "blur exceeded max: {}", output.len());
+}
+
+#[tokio::test]
+async fn stress_padding_runs_are_not_constant_pattern() {
+    // Stress and sanity-check: repeated runs should not collapse to identical
+    // first 16 bytes across all samples.
+    let mut first_chunks = Vec::new();
+    for _ in 0..64 {
+        let out = collect_padding(1, true, 64, 4096, false, 0, false).await;
+        first_chunks.push(out[..16].to_vec());
+    }
+
+    let first = &first_chunks[0];
+    let all_same = first_chunks.iter().all(|chunk| chunk == first);
+    assert!(
+        !all_same,
+        "all stress samples had identical prefix, rng output appears degenerate"
+    );
+}

src/proxy/tests/masking_security_tests.rs

@@ -1376,6 +1376,7 @@ async fn relay_to_mask_keeps_backend_to_client_flow_when_client_to_backend_stall
             false,
             0,
             false,
+            5 * 1024 * 1024,
         )
         .await;
     });
@@ -1506,6 +1507,7 @@ async fn relay_to_mask_timeout_cancels_and_drops_all_io_endpoints() {
             false,
             0,
             false,
+            5 * 1024 * 1024,
         ),
     )
     .await;

src/proxy/tests/masking_self_target_loop_security_tests.rs

@@ -0,0 +1,360 @@
+use super::*;
+use std::net::TcpListener as StdTcpListener;
+use std::net::SocketAddr;
+use tokio::io::{AsyncReadExt, AsyncWriteExt, duplex};
+use tokio::net::TcpListener;
+use tokio::time::{Duration, Instant, timeout};
+
+fn closed_local_port() -> u16 {
+    let listener = StdTcpListener::bind("127.0.0.1:0").unwrap();
+    let port = listener.local_addr().unwrap().port();
+    drop(listener);
+    port
+}
+
+#[tokio::test]
+async fn self_target_detection_matches_literal_ipv4_listener() {
+    let local: SocketAddr = "198.51.100.40:443".parse().unwrap();
+    assert!(is_mask_target_local_listener_async(
+        "198.51.100.40",
+        443,
+        local,
+        None,
+    )
+    .await);
+}
+
+#[tokio::test]
+async fn self_target_detection_matches_bracketed_ipv6_listener() {
+    let local: SocketAddr = "[2001:db8::44]:8443".parse().unwrap();
+    assert!(is_mask_target_local_listener_async(
+        "[2001:db8::44]",
+        8443,
+        local,
+        None,
+    )
+    .await);
+}
+
+#[tokio::test]
+async fn self_target_detection_keeps_same_ip_different_port_forwardable() {
+    let local: SocketAddr = "203.0.113.44:443".parse().unwrap();
+    assert!(!is_mask_target_local_listener_async(
+        "203.0.113.44",
+        8443,
+        local,
+        None,
+    )
+    .await);
+}
+
+#[tokio::test]
+async fn self_target_detection_normalizes_ipv4_mapped_ipv6_literal() {
+    let local: SocketAddr = "127.0.0.1:443".parse().unwrap();
+    assert!(is_mask_target_local_listener_async(
+        "::ffff:127.0.0.1",
+        443,
+        local,
+        None,
+    )
+    .await);
+}
+
+#[tokio::test]
+async fn self_target_detection_unspecified_bind_blocks_loopback_target() {
+    let local: SocketAddr = "0.0.0.0:443".parse().unwrap();
+    assert!(is_mask_target_local_listener_async(
+        "127.0.0.1",
+        443,
+        local,
+        None,
+    )
+    .await);
+}
+
+#[tokio::test]
+async fn self_target_detection_unspecified_bind_keeps_remote_target_forwardable() {
+    let local: SocketAddr = "0.0.0.0:443".parse().unwrap();
+    let remote: SocketAddr = "198.51.100.44:443".parse().unwrap();
+    assert!(!is_mask_target_local_listener_async(
+        "mask.example",
+        443,
+        local,
+        Some(remote),
+    )
+    .await);
+}
+
+#[tokio::test]
+async fn self_target_fallback_refuses_recursive_loopback_connect() {
+    let listener = TcpListener::bind("127.0.0.1:0").await.unwrap();
+    let local_addr = listener.local_addr().unwrap();
+    let accept_task = tokio::spawn(async move {
+        timeout(Duration::from_millis(120), listener.accept())
+            .await
+            .is_ok()
+    });
+
+    let mut config = ProxyConfig::default();
+    config.general.beobachten = false;
+    config.censorship.mask = true;
+    config.censorship.mask_unix_sock = None;
+    config.censorship.mask_host = Some(local_addr.ip().to_string());
+    config.censorship.mask_port = local_addr.port();
+    config.censorship.mask_proxy_protocol = 0;
+
+    let peer: SocketAddr = "203.0.113.90:55090".parse().unwrap();
+    let beobachten = BeobachtenStore::new();
+
+    handle_bad_client(
+        tokio::io::empty(),
+        tokio::io::sink(),
+        b"GET /",
+        peer,
+        local_addr,
+        &config,
+        &beobachten,
+    )
+    .await;
+
+    let accepted = accept_task.await.unwrap();
+    assert!(
+        !accepted,
+        "self-target masking must fail closed without connecting to local listener"
+    );
+}
+
+#[tokio::test]
+async fn same_ip_different_port_still_forwards_to_mask_backend() {
+    let listener = TcpListener::bind("127.0.0.1:0").await.unwrap();
+    let backend_addr = listener.local_addr().unwrap();
+    let probe = b"GET /".to_vec();
+    let accept_task = tokio::spawn({
+        let expected = probe.clone();
+        async move {
+            let (mut stream, _) = listener.accept().await.unwrap();
+            let mut got = vec![0u8; expected.len()];
+            stream.read_exact(&mut got).await.unwrap();
+            assert_eq!(got, expected);
+        }
+    });
+
+    let mut config = ProxyConfig::default();
+    config.general.beobachten = false;
+    config.censorship.mask = true;
+    config.censorship.mask_unix_sock = None;
+    config.censorship.mask_host = Some("127.0.0.1".to_string());
+    config.censorship.mask_port = backend_addr.port();
+    config.censorship.mask_proxy_protocol = 0;
+
+    let peer: SocketAddr = "203.0.113.91:55091".parse().unwrap();
+    let local_addr: SocketAddr = "127.0.0.1:443".parse().unwrap();
+    let beobachten = BeobachtenStore::new();
+
+    handle_bad_client(
+        tokio::io::empty(),
+        tokio::io::sink(),
+        &probe,
+        peer,
+        local_addr,
+        &config,
+        &beobachten,
+    )
+    .await;
+
+    timeout(Duration::from_secs(2), accept_task)
+        .await
+        .unwrap()
+        .unwrap();
+}
+
+#[test]
+fn detect_client_type_http_boundary_get_and_post() {
+    assert_eq!(detect_client_type(b"GET "), "HTTP");
+    assert_eq!(detect_client_type(b"GET /"), "HTTP");
+
+    assert_eq!(detect_client_type(b"POST"), "HTTP");
+    assert_eq!(detect_client_type(b"POST "), "HTTP");
+    assert_eq!(detect_client_type(b"POSTX"), "HTTP");
+}
+
+#[test]
+fn detect_client_type_tls_and_length_boundaries() {
+    assert_eq!(detect_client_type(b"\x16\x03\x01"), "port-scanner");
+    assert_eq!(detect_client_type(b"\x16\x03\x01\x00"), "TLS-scanner");
+
+    assert_eq!(detect_client_type(b"123456789"), "port-scanner");
+    assert_eq!(detect_client_type(b"1234567890"), "unknown");
+}
+
+#[test]
+fn build_mask_proxy_header_v1_cross_family_falls_back_to_unknown() {
+    let peer: SocketAddr = "192.168.1.5:12345".parse().unwrap();
+    let local: SocketAddr = "[2001:db8::1]:443".parse().unwrap();
+    let header = build_mask_proxy_header(1, peer, local).unwrap();
+    assert_eq!(header, b"PROXY UNKNOWN\r\n");
+}
+
+#[test]
+fn next_mask_shape_bucket_checked_mul_overflow_fails_closed() {
+    let floor = usize::MAX / 2 + 1;
+    let cap = usize::MAX;
+    let total = floor + 1;
+    assert_eq!(next_mask_shape_bucket(total, floor, cap), total);
+}
+
+#[tokio::test]
+async fn self_target_reject_path_keeps_timing_budget() {
+    let mut config = ProxyConfig::default();
+    config.general.beobachten = false;
+    config.censorship.mask = true;
+    config.censorship.mask_unix_sock = None;
+    config.censorship.mask_host = Some("127.0.0.1".to_string());
+    config.censorship.mask_port = 443;
+
+    let local_addr: SocketAddr = "127.0.0.1:443".parse().unwrap();
+    let peer: SocketAddr = "203.0.113.92:55092".parse().unwrap();
+    let beobachten = BeobachtenStore::new();
+
+    let (client, server) = duplex(1024);
+    drop(client);
+
+    let started = Instant::now();
+    handle_bad_client(
+        server,
+        tokio::io::sink(),
+        b"GET / HTTP/1.1\r\n",
+        peer,
+        local_addr,
+        &config,
+        &beobachten,
+    )
+    .await;
+
+    let elapsed = started.elapsed();
+    assert!(
+        elapsed >= Duration::from_millis(40) && elapsed < Duration::from_millis(250),
+        "self-target reject path must keep coarse timing budget without stalling"
+    );
+}
+
+#[tokio::test]
+async fn relay_path_idle_timeout_eviction_remains_effective() {
+    let (client_read, mut client_write) = duplex(1024);
+    let (mask_read, mask_write) = duplex(1024);
+
+    tokio::spawn(async move {
+        tokio::time::sleep(Duration::from_millis(10)).await;
+        client_write.write_all(b"a").await.unwrap();
+        tokio::time::sleep(Duration::from_millis(180)).await;
+        let _ = client_write.write_all(b"b").await;
+    });
+
+    let started = Instant::now();
+    relay_to_mask(
+        client_read,
+        tokio::io::sink(),
+        mask_read,
+        mask_write,
+        b"init",
+        false,
+        0,
+        0,
+        false,
+        0,
+        false,
+        5 * 1024 * 1024,
+    )
+    .await;
+
+    let elapsed = started.elapsed();
+    assert!(
+        elapsed >= Duration::from_millis(90) && elapsed < Duration::from_millis(180),
+        "idle-timeout eviction must occur before late trickle write"
+    );
+}
+
+#[tokio::test]
+async fn offline_mask_target_refusal_respects_timing_normalization_budget() {
+    let mut config = ProxyConfig::default();
+    config.general.beobachten = false;
+    config.censorship.mask = true;
+    config.censorship.mask_unix_sock = None;
+    config.censorship.mask_host = Some("127.0.0.1".to_string());
+    config.censorship.mask_port = closed_local_port();
+    config.censorship.mask_timing_normalization_enabled = true;
+    config.censorship.mask_timing_normalization_floor_ms = 120;
+    config.censorship.mask_timing_normalization_ceiling_ms = 120;
+
+    let peer: SocketAddr = "203.0.113.93:55093".parse().unwrap();
+    let local_addr: SocketAddr = "127.0.0.1:443".parse().unwrap();
+    let beobachten = BeobachtenStore::new();
+
+    let (mut client, server) = duplex(1024);
+    let started = Instant::now();
+    let task = tokio::spawn(async move {
+        handle_bad_client(
+            server,
+            tokio::io::sink(),
+            b"GET / HTTP/1.1\r\n\r\n",
+            peer,
+            local_addr,
+            &config,
+            &beobachten,
+        )
+        .await;
+    });
+
+    client.shutdown().await.unwrap();
+    timeout(Duration::from_secs(2), task).await.unwrap().unwrap();
+    let elapsed = started.elapsed();
+
+    assert!(
+        elapsed >= Duration::from_millis(110) && elapsed < Duration::from_millis(220),
+        "offline-refusal path must honor normalization budget without unbounded drift"
+    );
+}
+
+#[tokio::test]
+async fn offline_mask_target_refusal_with_idle_client_is_bounded_by_consume_timeout() {
+    let mut config = ProxyConfig::default();
+    config.general.beobachten = false;
+    config.censorship.mask = true;
+    config.censorship.mask_unix_sock = None;
+    config.censorship.mask_host = Some("127.0.0.1".to_string());
+    config.censorship.mask_port = closed_local_port();
+    config.censorship.mask_timing_normalization_enabled = false;
+
+    let peer: SocketAddr = "203.0.113.94:55094".parse().unwrap();
+    let local_addr: SocketAddr = "127.0.0.1:443".parse().unwrap();
+    let beobachten = BeobachtenStore::new();
+
+    let (mut client, server) = duplex(1024);
+    let started = Instant::now();
+    let task = tokio::spawn(async move {
+        handle_bad_client(
+            server,
+            tokio::io::sink(),
+            b"GET / HTTP/1.1\r\n\r\n",
+            peer,
+            local_addr,
+            &config,
+            &beobachten,
+        )
+        .await;
+    });
+
+    tokio::time::sleep(Duration::from_millis(120)).await;
+    client
+        .write_all(b"still-open-before-timeout")
+        .await
+        .expect("connection should still be open before consume timeout expires");
+
+    timeout(Duration::from_secs(2), task).await.unwrap().unwrap();
+    let elapsed = started.elapsed();
+
+    assert!(
+        elapsed >= Duration::from_millis(190) && elapsed < Duration::from_millis(350),
+        "offline-refusal path must not retain idle client indefinitely"
+    );
+}

src/proxy/tests/masking_shape_guard_adversarial_tests.rs

@@ -43,6 +43,7 @@ async fn run_relay_case(
             above_cap_blur,
             above_cap_blur_max_bytes,
             false,
+            5 * 1024 * 1024,
         )
         .await;
     });

src/proxy/tests/masking_shape_hardening_adversarial_tests.rs

@@ -88,6 +88,7 @@ async fn relay_to_mask_applies_cap_clamped_padding_for_non_power_of_two_cap() {
             false,
             0,
             false,
+            5 * 1024 * 1024,
         )
         .await;
     });

src/proxy/tests/masking_timing_budget_coupling_security_tests.rs

@@ -0,0 +1,55 @@
+#![cfg(unix)]
+
+use super::*;
+use tokio::io::{AsyncWriteExt, duplex};
+use tokio::time::{Duration, Instant, timeout};
+
+#[tokio::test(flavor = "multi_thread", worker_threads = 2)]
+async fn adversarial_delayed_interface_lookup_does_not_consume_outcome_floor_budget() {
+    let mut config = ProxyConfig::default();
+    config.general.beobachten = false;
+    config.censorship.mask = true;
+    config.censorship.mask_unix_sock = None;
+    config.censorship.mask_host = Some("127.0.0.1".to_string());
+    config.censorship.mask_port = 443;
+    config.censorship.mask_timing_normalization_enabled = true;
+    config.censorship.mask_timing_normalization_floor_ms = 120;
+    config.censorship.mask_timing_normalization_ceiling_ms = 120;
+
+    let peer: SocketAddr = "203.0.113.151:55151".parse().expect("valid peer");
+    let local_addr: SocketAddr = "0.0.0.0:443".parse().expect("valid local addr");
+    let beobachten = BeobachtenStore::new();
+
+    let refresh_lock = LOCAL_INTERFACE_REFRESH_LOCK.get_or_init(|| AsyncMutex::new(()));
+    let held_refresh_guard = refresh_lock.lock().await;
+
+    let (mut client, server) = duplex(1024);
+    let started = Instant::now();
+    let task = tokio::spawn(async move {
+        handle_bad_client(
+            server,
+            tokio::io::sink(),
+            b"GET / HTTP/1.1\r\n\r\n",
+            peer,
+            local_addr,
+            &config,
+            &beobachten,
+        )
+        .await;
+    });
+
+    tokio::time::sleep(Duration::from_millis(80)).await;
+    drop(held_refresh_guard);
+    client.shutdown().await.expect("client shutdown must succeed");
+
+    timeout(Duration::from_secs(2), task)
+        .await
+        .expect("task must finish in bounded time")
+        .expect("task must not panic");
+    let elapsed = started.elapsed();
+
+    assert!(
+        elapsed >= Duration::from_millis(180) && elapsed < Duration::from_millis(350),
+        "timing normalization floor must start after pre-outcome self-target checks"
+    );
+}

src/proxy/tests/middle_relay_blackhat_campaign_integration_tests.rs

@@ -1,112 +0,0 @@
-use super::*;
-use crate::stats::Stats;
-use dashmap::DashMap;
-use std::sync::Arc;
-use std::sync::atomic::{AtomicUsize, Ordering};
-use tokio::sync::Barrier;
-use tokio::time::{Duration, timeout};
-
-#[tokio::test(flavor = "multi_thread", worker_threads = 4)]
-async fn blackhat_campaign_saturation_quota_race_with_queue_pressure_stays_fail_closed() {
-    let _guard = super::quota_user_lock_test_scope();
-    let map = QUOTA_USER_LOCKS.get_or_init(DashMap::new);
-    map.clear();
-
-    let mut retained = Vec::with_capacity(QUOTA_USER_LOCKS_MAX);
-    for idx in 0..QUOTA_USER_LOCKS_MAX {
-        retained.push(quota_user_lock(&format!(
-            "middle-blackhat-held-{}-{idx}",
-            std::process::id()
-        )));
-    }
-
-    assert_eq!(
-        map.len(),
-        QUOTA_USER_LOCKS_MAX,
-        "precondition: bounded lock cache must be saturated"
-    );
-
-    let (tx, _rx) = mpsc::channel::<C2MeCommand>(1);
-    tx.send(C2MeCommand::Close)
-        .await
-        .expect("queue prefill should succeed");
-
-    let pressure_seq_before = relay_pressure_event_seq();
-    let pressure_errors = Arc::new(AtomicUsize::new(0));
-    let mut pressure_workers = Vec::new();
-    for _ in 0..16 {
-        let tx = tx.clone();
-        let pressure_errors = Arc::clone(&pressure_errors);
-        pressure_workers.push(tokio::spawn(async move {
-            if enqueue_c2me_command(&tx, C2MeCommand::Close).await.is_err() {
-                pressure_errors.fetch_add(1, Ordering::Relaxed);
-            }
-        }));
-    }
-
-    let stats = Arc::new(Stats::new());
-    let user = format!("middle-blackhat-quota-race-{}", std::process::id());
-    let gate = Arc::new(Barrier::new(16));
-
-    let mut quota_workers = Vec::new();
-    for _ in 0..16u8 {
-        let stats = Arc::clone(&stats);
-        let user = user.clone();
-        let gate = Arc::clone(&gate);
-        quota_workers.push(tokio::spawn(async move {
-            gate.wait().await;
-            let user_lock = quota_user_lock(&user);
-            let _quota_guard = user_lock.lock().await;
-
-            if quota_would_be_exceeded_for_user(&stats, &user, Some(1), 1) {
-                return false;
-            }
-            stats.add_user_octets_to(&user, 1);
-            true
-        }));
-    }
-
-    let mut ok_count = 0usize;
-    let mut denied_count = 0usize;
-    for worker in quota_workers {
-        let result = timeout(Duration::from_secs(2), worker)
-            .await
-            .expect("quota worker must finish")
-            .expect("quota worker must not panic");
-        if result {
-            ok_count += 1;
-        } else {
-            denied_count += 1;
-        }
-    }
-
-    for worker in pressure_workers {
-        timeout(Duration::from_secs(2), worker)
-            .await
-            .expect("pressure worker must finish")
-            .expect("pressure worker must not panic");
-    }
-
-    assert_eq!(
-        stats.get_user_total_octets(&user),
-        1,
-        "black-hat campaign must not overshoot same-user quota under saturation"
-    );
-    assert!(ok_count <= 1, "at most one quota contender may succeed");
-    assert!(
-        denied_count >= 15,
-        "all remaining contenders must be quota-denied"
-    );
-
-    let pressure_seq_after = relay_pressure_event_seq();
-    assert!(
-        pressure_seq_after > pressure_seq_before,
-        "queue pressure leg must trigger pressure accounting"
-    );
-    assert!(
-        pressure_errors.load(Ordering::Relaxed) >= 1,
-        "at least one pressure worker should fail from persistent backpressure"
-    );
-
-    drop(retained);
-}

src/proxy/tests/middle_relay_coverage_high_risk_security_tests.rs

@@ -1,708 +0,0 @@
-use super::*;
-use crate::crypto::AesCtr;
-use crate::crypto::SecureRandom;
-use crate::stats::Stats;
-use crate::stream::{BufferPool, PooledBuffer};
-use std::sync::Arc;
-use tokio::io::AsyncReadExt;
-use tokio::io::duplex;
-use tokio::sync::mpsc;
-use tokio::time::{Duration as TokioDuration, timeout};
-
-fn make_pooled_payload(data: &[u8]) -> PooledBuffer {
-    let pool = Arc::new(BufferPool::with_config(data.len().max(1), 4));
-    let mut payload = pool.get();
-    payload.resize(data.len(), 0);
-    payload[..data.len()].copy_from_slice(data);
-    payload
-}
-
-#[tokio::test]
-async fn write_client_payload_abridged_short_quickack_sets_flag_and_preserves_payload() {
-    let (mut read_side, write_side) = duplex(4096);
-    let key = [0u8; 32];
-    let iv = 0u128;
-
-    let mut writer = CryptoWriter::new(write_side, AesCtr::new(&key, iv), 8 * 1024);
-    let mut decryptor = AesCtr::new(&key, iv);
-    let rng = SecureRandom::new();
-    let mut frame_buf = Vec::new();
-    let payload = vec![0xA1, 0xB2, 0xC3, 0xD4, 0x10, 0x20, 0x30, 0x40];
-
-    write_client_payload(
-        &mut writer,
-        ProtoTag::Abridged,
-        RPC_FLAG_QUICKACK,
-        &payload,
-        &rng,
-        &mut frame_buf,
-    )
-    .await
-    .expect("abridged quickack payload should serialize");
-    writer.flush().await.expect("flush must succeed");
-
-    let mut encrypted = vec![0u8; 1 + payload.len()];
-    read_side
-        .read_exact(&mut encrypted)
-        .await
-        .expect("must read serialized abridged frame");
-    let plaintext = decryptor.decrypt(&encrypted);
-
-    assert_eq!(plaintext[0], 0x80 | ((payload.len() / 4) as u8));
-    assert_eq!(&plaintext[1..], payload.as_slice());
-}
-
-#[tokio::test]
-async fn write_client_payload_abridged_extended_header_is_encoded_correctly() {
-    let (mut read_side, write_side) = duplex(16 * 1024);
-    let key = [0u8; 32];
-    let iv = 0u128;
-
-    let mut writer = CryptoWriter::new(write_side, AesCtr::new(&key, iv), 8 * 1024);
-    let mut decryptor = AesCtr::new(&key, iv);
-    let rng = SecureRandom::new();
-    let mut frame_buf = Vec::new();
-
-    // Boundary where abridged switches to extended length encoding.
-    let payload = vec![0x5Au8; 0x7f * 4];
-
-    write_client_payload(
-        &mut writer,
-        ProtoTag::Abridged,
-        RPC_FLAG_QUICKACK,
-        &payload,
-        &rng,
-        &mut frame_buf,
-    )
-    .await
-    .expect("extended abridged payload should serialize");
-    writer.flush().await.expect("flush must succeed");
-
-    let mut encrypted = vec![0u8; 4 + payload.len()];
-    read_side
-        .read_exact(&mut encrypted)
-        .await
-        .expect("must read serialized extended abridged frame");
-    let plaintext = decryptor.decrypt(&encrypted);
-
-    assert_eq!(plaintext[0], 0xff, "0x7f with quickack bit must be set");
-    assert_eq!(&plaintext[1..4], &[0x7f, 0x00, 0x00]);
-    assert_eq!(&plaintext[4..], payload.as_slice());
-}
-
-#[tokio::test]
-async fn write_client_payload_abridged_misaligned_is_rejected_fail_closed() {
-    let (_read_side, write_side) = duplex(1024);
-    let key = [0u8; 32];
-    let iv = 0u128;
-
-    let mut writer = CryptoWriter::new(write_side, AesCtr::new(&key, iv), 8 * 1024);
-    let rng = SecureRandom::new();
-    let mut frame_buf = Vec::new();
-
-    let err = write_client_payload(
-        &mut writer,
-        ProtoTag::Abridged,
-        0,
-        &[1, 2, 3],
-        &rng,
-        &mut frame_buf,
-    )
-    .await
-    .expect_err("misaligned abridged payload must be rejected");
-
-    let msg = format!("{err}");
-    assert!(
-        msg.contains("4-byte aligned"),
-        "error should explain alignment contract, got: {msg}"
-    );
-}
-
-#[tokio::test]
-async fn write_client_payload_secure_misaligned_is_rejected_fail_closed() {
-    let (_read_side, write_side) = duplex(1024);
-    let key = [0u8; 32];
-    let iv = 0u128;
-
-    let mut writer = CryptoWriter::new(write_side, AesCtr::new(&key, iv), 8 * 1024);
-    let rng = SecureRandom::new();
-    let mut frame_buf = Vec::new();
-
-    let err = write_client_payload(
-        &mut writer,
-        ProtoTag::Secure,
-        0,
-        &[9, 8, 7, 6, 5],
-        &rng,
-        &mut frame_buf,
-    )
-    .await
-    .expect_err("misaligned secure payload must be rejected");
-
-    let msg = format!("{err}");
-    assert!(
-        msg.contains("Secure payload must be 4-byte aligned"),
-        "error should be explicit for fail-closed triage, got: {msg}"
-    );
-}
-
-#[tokio::test]
-async fn write_client_payload_intermediate_quickack_sets_length_msb() {
-    let (mut read_side, write_side) = duplex(4096);
-    let key = [0u8; 32];
-    let iv = 0u128;
-
-    let mut writer = CryptoWriter::new(write_side, AesCtr::new(&key, iv), 8 * 1024);
-    let mut decryptor = AesCtr::new(&key, iv);
-    let rng = SecureRandom::new();
-    let mut frame_buf = Vec::new();
-    let payload = b"hello-middle-relay";
-
-    write_client_payload(
-        &mut writer,
-        ProtoTag::Intermediate,
-        RPC_FLAG_QUICKACK,
-        payload,
-        &rng,
-        &mut frame_buf,
-    )
-    .await
-    .expect("intermediate quickack payload should serialize");
-    writer.flush().await.expect("flush must succeed");
-
-    let mut encrypted = vec![0u8; 4 + payload.len()];
-    read_side
-        .read_exact(&mut encrypted)
-        .await
-        .expect("must read intermediate frame");
-    let plaintext = decryptor.decrypt(&encrypted);
-
-    let mut len_bytes = [0u8; 4];
-    len_bytes.copy_from_slice(&plaintext[..4]);
-    let len_with_flags = u32::from_le_bytes(len_bytes);
-    assert_ne!(len_with_flags & 0x8000_0000, 0, "quickack bit must be set");
-    assert_eq!((len_with_flags & 0x7fff_ffff) as usize, payload.len());
-    assert_eq!(&plaintext[4..], payload);
-}
-
-#[tokio::test]
-async fn write_client_payload_secure_quickack_prefix_and_padding_bounds_hold() {
-    let (mut read_side, write_side) = duplex(4096);
-    let key = [0u8; 32];
-    let iv = 0u128;
-
-    let mut writer = CryptoWriter::new(write_side, AesCtr::new(&key, iv), 8 * 1024);
-    let mut decryptor = AesCtr::new(&key, iv);
-    let rng = SecureRandom::new();
-    let mut frame_buf = Vec::new();
-    let payload = vec![0x33u8; 100]; // 4-byte aligned as required by secure mode.
-
-    write_client_payload(
-        &mut writer,
-        ProtoTag::Secure,
-        RPC_FLAG_QUICKACK,
-        &payload,
-        &rng,
-        &mut frame_buf,
-    )
-    .await
-    .expect("secure quickack payload should serialize");
-    writer.flush().await.expect("flush must succeed");
-
-    // Secure mode adds 1..=3 bytes of randomized tail padding.
-    let mut encrypted_header = [0u8; 4];
-    read_side
-        .read_exact(&mut encrypted_header)
-        .await
-        .expect("must read secure header");
-    let decrypted_header = decryptor.decrypt(&encrypted_header);
-    let header: [u8; 4] = decrypted_header
-        .try_into()
-        .expect("decrypted secure header must be 4 bytes");
-    let wire_len_raw = u32::from_le_bytes(header);
-
-    assert_ne!(
-        wire_len_raw & 0x8000_0000,
-        0,
-        "secure quickack bit must be set"
-    );
-
-    let wire_len = (wire_len_raw & 0x7fff_ffff) as usize;
-    assert!(wire_len >= payload.len());
-    let padding_len = wire_len - payload.len();
-    assert!(
-        (1..=3).contains(&padding_len),
-        "secure writer must add bounded random tail padding, got {padding_len}"
-    );
-
-    let mut encrypted_body = vec![0u8; wire_len];
-    read_side
-        .read_exact(&mut encrypted_body)
-        .await
-        .expect("must read secure body");
-    let decrypted_body = decryptor.decrypt(&encrypted_body);
-    assert_eq!(&decrypted_body[..payload.len()], payload.as_slice());
-}
-
-#[tokio::test]
-#[ignore = "heavy: allocates >64MiB to validate abridged too-large fail-closed branch"]
-async fn write_client_payload_abridged_too_large_is_rejected_fail_closed() {
-    let (_read_side, write_side) = duplex(1024);
-    let key = [0u8; 32];
-    let iv = 0u128;
-
-    let mut writer = CryptoWriter::new(write_side, AesCtr::new(&key, iv), 8 * 1024);
-    let rng = SecureRandom::new();
-    let mut frame_buf = Vec::new();
-
-    // Exactly one 4-byte word above the encodable 24-bit abridged length range.
-    let payload = vec![0x00u8; (1 << 24) * 4];
-    let err = write_client_payload(
-        &mut writer,
-        ProtoTag::Abridged,
-        0,
-        &payload,
-        &rng,
-        &mut frame_buf,
-    )
-    .await
-    .expect_err("oversized abridged payload must be rejected");
-
-    let msg = format!("{err}");
-    assert!(
-        msg.contains("Abridged frame too large"),
-        "error must clearly indicate oversize fail-close path, got: {msg}"
-    );
-}
-
-#[tokio::test]
-async fn write_client_ack_intermediate_is_little_endian() {
-    let (mut read_side, write_side) = duplex(1024);
-    let key = [0u8; 32];
-    let iv = 0u128;
-    let mut writer = CryptoWriter::new(write_side, AesCtr::new(&key, iv), 8 * 1024);
-    let mut decryptor = AesCtr::new(&key, iv);
-
-    write_client_ack(&mut writer, ProtoTag::Intermediate, 0x11_22_33_44)
-        .await
-        .expect("ack serialization should succeed");
-    writer.flush().await.expect("flush must succeed");
-
-    let mut encrypted = [0u8; 4];
-    read_side
-        .read_exact(&mut encrypted)
-        .await
-        .expect("must read ack bytes");
-    let plain = decryptor.decrypt(&encrypted);
-    assert_eq!(plain.as_slice(), &0x11_22_33_44u32.to_le_bytes());
-}
-
-#[tokio::test]
-async fn write_client_ack_abridged_is_big_endian() {
-    let (mut read_side, write_side) = duplex(1024);
-    let key = [0u8; 32];
-    let iv = 0u128;
-    let mut writer = CryptoWriter::new(write_side, AesCtr::new(&key, iv), 8 * 1024);
-    let mut decryptor = AesCtr::new(&key, iv);
-
-    write_client_ack(&mut writer, ProtoTag::Abridged, 0xDE_AD_BE_EF)
-        .await
-        .expect("ack serialization should succeed");
-    writer.flush().await.expect("flush must succeed");
-
-    let mut encrypted = [0u8; 4];
-    read_side
-        .read_exact(&mut encrypted)
-        .await
-        .expect("must read ack bytes");
-    let plain = decryptor.decrypt(&encrypted);
-    assert_eq!(plain.as_slice(), &0xDE_AD_BE_EFu32.to_be_bytes());
-}
-
-#[tokio::test]
-async fn write_client_payload_abridged_short_boundary_0x7e_is_single_byte_header() {
-    let (mut read_side, write_side) = duplex(1024 * 1024);
-    let key = [0u8; 32];
-    let iv = 0u128;
-    let mut writer = CryptoWriter::new(write_side, AesCtr::new(&key, iv), 8 * 1024);
-    let mut decryptor = AesCtr::new(&key, iv);
-    let rng = SecureRandom::new();
-    let mut frame_buf = Vec::new();
-    let payload = vec![0xABu8; 0x7e * 4];
-
-    write_client_payload(
-        &mut writer,
-        ProtoTag::Abridged,
-        0,
-        &payload,
-        &rng,
-        &mut frame_buf,
-    )
-    .await
-    .expect("boundary payload should serialize");
-    writer.flush().await.expect("flush must succeed");
-
-    let mut encrypted = vec![0u8; 1 + payload.len()];
-    read_side.read_exact(&mut encrypted).await.unwrap();
-    let plain = decryptor.decrypt(&encrypted);
-    assert_eq!(plain[0], 0x7e);
-    assert_eq!(&plain[1..], payload.as_slice());
-}
-
-#[tokio::test]
-async fn write_client_payload_abridged_extended_without_quickack_has_clean_prefix() {
-    let (mut read_side, write_side) = duplex(16 * 1024);
-    let key = [0u8; 32];
-    let iv = 0u128;
-    let mut writer = CryptoWriter::new(write_side, AesCtr::new(&key, iv), 8 * 1024);
-    let mut decryptor = AesCtr::new(&key, iv);
-    let rng = SecureRandom::new();
-    let mut frame_buf = Vec::new();
-    let payload = vec![0x42u8; 0x80 * 4];
-
-    write_client_payload(
-        &mut writer,
-        ProtoTag::Abridged,
-        0,
-        &payload,
-        &rng,
-        &mut frame_buf,
-    )
-    .await
-    .expect("extended payload should serialize");
-    writer.flush().await.expect("flush must succeed");
-
-    let mut encrypted = vec![0u8; 4 + payload.len()];
-    read_side.read_exact(&mut encrypted).await.unwrap();
-    let plain = decryptor.decrypt(&encrypted);
-    assert_eq!(plain[0], 0x7f);
-    assert_eq!(&plain[1..4], &[0x80, 0x00, 0x00]);
-    assert_eq!(&plain[4..], payload.as_slice());
-}
-
-#[tokio::test]
-async fn write_client_payload_intermediate_zero_length_emits_header_only() {
-    let (mut read_side, write_side) = duplex(1024);
-    let key = [0u8; 32];
-    let iv = 0u128;
-    let mut writer = CryptoWriter::new(write_side, AesCtr::new(&key, iv), 8 * 1024);
-    let mut decryptor = AesCtr::new(&key, iv);
-    let rng = SecureRandom::new();
-    let mut frame_buf = Vec::new();
-
-    write_client_payload(
-        &mut writer,
-        ProtoTag::Intermediate,
-        0,
-        &[],
-        &rng,
-        &mut frame_buf,
-    )
-    .await
-    .expect("zero-length intermediate payload should serialize");
-    writer.flush().await.expect("flush must succeed");
-
-    let mut encrypted = [0u8; 4];
-    read_side.read_exact(&mut encrypted).await.unwrap();
-    let plain = decryptor.decrypt(&encrypted);
-    assert_eq!(plain.as_slice(), &[0, 0, 0, 0]);
-}
-
-#[tokio::test]
-async fn write_client_payload_intermediate_ignores_unrelated_flags() {
-    let (mut read_side, write_side) = duplex(1024);
-    let key = [0u8; 32];
-    let iv = 0u128;
-    let mut writer = CryptoWriter::new(write_side, AesCtr::new(&key, iv), 8 * 1024);
-    let mut decryptor = AesCtr::new(&key, iv);
-    let rng = SecureRandom::new();
-    let mut frame_buf = Vec::new();
-    let payload = [7u8; 12];
-
-    write_client_payload(
-        &mut writer,
-        ProtoTag::Intermediate,
-        0x4000_0000,
-        &payload,
-        &rng,
-        &mut frame_buf,
-    )
-    .await
-    .expect("payload should serialize");
-    writer.flush().await.expect("flush must succeed");
-
-    let mut encrypted = [0u8; 16];
-    read_side.read_exact(&mut encrypted).await.unwrap();
-    let plain = decryptor.decrypt(&encrypted);
-    let len = u32::from_le_bytes(plain[0..4].try_into().unwrap());
-    assert_eq!(len, payload.len() as u32, "only quickack bit may affect header");
-    assert_eq!(&plain[4..], payload.as_slice());
-}
-
-#[tokio::test]
-async fn write_client_payload_secure_without_quickack_keeps_msb_clear() {
-    let (mut read_side, write_side) = duplex(4096);
-    let key = [0u8; 32];
-    let iv = 0u128;
-    let mut writer = CryptoWriter::new(write_side, AesCtr::new(&key, iv), 8 * 1024);
-    let mut decryptor = AesCtr::new(&key, iv);
-    let rng = SecureRandom::new();
-    let mut frame_buf = Vec::new();
-    let payload = [0x1Du8; 64];
-
-    write_client_payload(
-        &mut writer,
-        ProtoTag::Secure,
-        0,
-        &payload,
-        &rng,
-        &mut frame_buf,
-    )
-    .await
-    .expect("payload should serialize");
-    writer.flush().await.expect("flush must succeed");
-
-    let mut encrypted_header = [0u8; 4];
-    read_side.read_exact(&mut encrypted_header).await.unwrap();
-    let plain_header = decryptor.decrypt(&encrypted_header);
-    let h: [u8; 4] = plain_header.as_slice().try_into().unwrap();
-    let wire_len_raw = u32::from_le_bytes(h);
-    assert_eq!(wire_len_raw & 0x8000_0000, 0, "quickack bit must stay clear");
-}
-
-#[tokio::test]
-async fn secure_padding_light_fuzz_distribution_has_multiple_outcomes() {
-    let (mut read_side, write_side) = duplex(256 * 1024);
-    let key = [0u8; 32];
-    let iv = 0u128;
-    let mut writer = CryptoWriter::new(write_side, AesCtr::new(&key, iv), 8 * 1024);
-    let mut decryptor = AesCtr::new(&key, iv);
-    let rng = SecureRandom::new();
-    let mut frame_buf = Vec::new();
-    let payload = [0x55u8; 100];
-    let mut seen = [false; 4];
-
-    for _ in 0..96 {
-        write_client_payload(
-            &mut writer,
-            ProtoTag::Secure,
-            0,
-            &payload,
-            &rng,
-            &mut frame_buf,
-        )
-        .await
-        .expect("secure payload should serialize");
-        writer.flush().await.expect("flush must succeed");
-
-        let mut encrypted_header = [0u8; 4];
-        read_side.read_exact(&mut encrypted_header).await.unwrap();
-        let plain_header = decryptor.decrypt(&encrypted_header);
-        let h: [u8; 4] = plain_header.as_slice().try_into().unwrap();
-        let wire_len = (u32::from_le_bytes(h) & 0x7fff_ffff) as usize;
-        let padding_len = wire_len - payload.len();
-        assert!((1..=3).contains(&padding_len));
-        seen[padding_len] = true;
-
-        let mut encrypted_body = vec![0u8; wire_len];
-        read_side.read_exact(&mut encrypted_body).await.unwrap();
-        let _ = decryptor.decrypt(&encrypted_body);
-    }
-
-    let distinct = (1..=3).filter(|idx| seen[*idx]).count();
-    assert!(
-        distinct >= 2,
-        "padding generator should not collapse to a single outcome under campaign"
-    );
-}
-
-#[tokio::test]
-async fn write_client_payload_mixed_proto_sequence_preserves_stream_sync() {
-    let (mut read_side, write_side) = duplex(128 * 1024);
-    let key = [0u8; 32];
-    let iv = 0u128;
-    let mut writer = CryptoWriter::new(write_side, AesCtr::new(&key, iv), 8 * 1024);
-    let mut decryptor = AesCtr::new(&key, iv);
-    let rng = SecureRandom::new();
-    let mut frame_buf = Vec::new();
-
-    let p1 = vec![1u8; 8];
-    let p2 = vec![2u8; 16];
-    let p3 = vec![3u8; 20];
-
-    write_client_payload(&mut writer, ProtoTag::Abridged, 0, &p1, &rng, &mut frame_buf)
-        .await
-        .unwrap();
-    write_client_payload(
-        &mut writer,
-        ProtoTag::Intermediate,
-        RPC_FLAG_QUICKACK,
-        &p2,
-        &rng,
-        &mut frame_buf,
-    )
-    .await
-    .unwrap();
-    write_client_payload(&mut writer, ProtoTag::Secure, 0, &p3, &rng, &mut frame_buf)
-        .await
-        .unwrap();
-    writer.flush().await.unwrap();
-
-    // Frame 1: abridged short.
-    let mut e1 = vec![0u8; 1 + p1.len()];
-    read_side.read_exact(&mut e1).await.unwrap();
-    let d1 = decryptor.decrypt(&e1);
-    assert_eq!(d1[0], (p1.len() / 4) as u8);
-    assert_eq!(&d1[1..], p1.as_slice());
-
-    // Frame 2: intermediate with quickack.
-    let mut e2 = vec![0u8; 4 + p2.len()];
-    read_side.read_exact(&mut e2).await.unwrap();
-    let d2 = decryptor.decrypt(&e2);
-    let l2 = u32::from_le_bytes(d2[0..4].try_into().unwrap());
-    assert_ne!(l2 & 0x8000_0000, 0);
-    assert_eq!((l2 & 0x7fff_ffff) as usize, p2.len());
-    assert_eq!(&d2[4..], p2.as_slice());
-
-    // Frame 3: secure with bounded tail.
-    let mut e3h = [0u8; 4];
-    read_side.read_exact(&mut e3h).await.unwrap();
-    let d3h = decryptor.decrypt(&e3h);
-    let l3 = (u32::from_le_bytes(d3h.as_slice().try_into().unwrap()) & 0x7fff_ffff) as usize;
-    assert!(l3 >= p3.len());
-    assert!((1..=3).contains(&(l3 - p3.len())));
-    let mut e3b = vec![0u8; l3];
-    read_side.read_exact(&mut e3b).await.unwrap();
-    let d3b = decryptor.decrypt(&e3b);
-    assert_eq!(&d3b[..p3.len()], p3.as_slice());
-}
-
-#[test]
-fn should_yield_sender_boundary_matrix_blackhat() {
-    assert!(!should_yield_c2me_sender(0, false));
-    assert!(!should_yield_c2me_sender(0, true));
-    assert!(!should_yield_c2me_sender(C2ME_SENDER_FAIRNESS_BUDGET - 1, true));
-    assert!(!should_yield_c2me_sender(C2ME_SENDER_FAIRNESS_BUDGET, false));
-    assert!(should_yield_c2me_sender(C2ME_SENDER_FAIRNESS_BUDGET, true));
-    assert!(should_yield_c2me_sender(
-        C2ME_SENDER_FAIRNESS_BUDGET.saturating_add(1024),
-        true
-    ));
-}
-
-#[test]
-fn should_yield_sender_light_fuzz_matches_oracle() {
-    let mut s: u64 = 0xD00D_BAAD_F00D_CAFE;
-    for _ in 0..5000 {
-        s ^= s << 7;
-        s ^= s >> 9;
-        s ^= s << 8;
-        let sent = (s as usize) & 0x1fff;
-        let backlog = (s & 1) != 0;
-
-        let expected = backlog && sent >= C2ME_SENDER_FAIRNESS_BUDGET;
-        assert_eq!(should_yield_c2me_sender(sent, backlog), expected);
-    }
-}
-
-#[test]
-fn quota_would_be_exceeded_exact_remaining_one_byte() {
-    let stats = Stats::new();
-    let user = "quota-edge";
-    let quota = 100u64;
-    stats.add_user_octets_to(user, 99);
-
-    assert!(
-        !quota_would_be_exceeded_for_user(&stats, user, Some(quota), 1),
-        "exactly remaining budget should be allowed"
-    );
-    assert!(
-        quota_would_be_exceeded_for_user(&stats, user, Some(quota), 2),
-        "one byte beyond remaining budget must be rejected"
-    );
-}
-
-#[test]
-fn quota_would_be_exceeded_saturating_edge_remains_fail_closed() {
-    let stats = Stats::new();
-    let user = "quota-saturating-edge";
-    let quota = u64::MAX - 3;
-    stats.add_user_octets_to(user, u64::MAX - 4);
-
-    assert!(
-        quota_would_be_exceeded_for_user(&stats, user, Some(quota), 2),
-        "saturating arithmetic edge must stay fail-closed"
-    );
-}
-
-#[test]
-fn quota_exceeded_boundary_is_inclusive() {
-    let stats = Stats::new();
-    let user = "quota-inclusive-boundary";
-    stats.add_user_octets_to(user, 50);
-
-    assert!(quota_exceeded_for_user(&stats, user, Some(50)));
-    assert!(!quota_exceeded_for_user(&stats, user, Some(51)));
-}
-
-#[tokio::test]
-async fn enqueue_c2me_close_fast_path_succeeds_without_backpressure() {
-    let (tx, mut rx) = mpsc::channel::<C2MeCommand>(4);
-    enqueue_c2me_command(&tx, C2MeCommand::Close)
-        .await
-        .expect("close should enqueue on fast path");
-
-    let recv = timeout(TokioDuration::from_millis(50), rx.recv())
-        .await
-        .expect("must receive close command")
-        .expect("close command should be present");
-    assert!(matches!(recv, C2MeCommand::Close));
-}
-
-#[tokio::test]
-async fn enqueue_c2me_data_full_then_drain_preserves_order() {
-    let (tx, mut rx) = mpsc::channel::<C2MeCommand>(1);
-    tx.send(C2MeCommand::Data {
-        payload: make_pooled_payload(&[1]),
-        flags: 10,
-    })
-    .await
-    .unwrap();
-
-    let tx2 = tx.clone();
-    let producer = tokio::spawn(async move {
-        enqueue_c2me_command(
-            &tx2,
-            C2MeCommand::Data {
-                payload: make_pooled_payload(&[2, 2]),
-                flags: 20,
-            },
-        )
-        .await
-    });
-
-    tokio::time::sleep(TokioDuration::from_millis(10)).await;
-
-    let first = rx.recv().await.expect("first item should exist");
-    match first {
-        C2MeCommand::Data { payload, flags } => {
-            assert_eq!(payload.as_ref(), &[1]);
-            assert_eq!(flags, 10);
-        }
-        C2MeCommand::Close => panic!("unexpected close as first item"),
-    }
-
-    producer.await.unwrap().expect("producer should complete");
-
-    let second = timeout(TokioDuration::from_millis(100), rx.recv())
-        .await
-        .unwrap()
-        .expect("second item should exist");
-    match second {
-        C2MeCommand::Data { payload, flags } => {
-            assert_eq!(payload.as_ref(), &[2, 2]);
-            assert_eq!(flags, 20);
-        }
-        C2MeCommand::Close => panic!("unexpected close as second item"),
-    }
-}

src/proxy/tests/middle_relay_idle_policy_security_tests.rs

@@ -3,7 +3,7 @@ use crate::crypto::AesCtr;
 use crate::stats::Stats;
 use crate::stream::{BufferPool, CryptoReader};
 use std::sync::atomic::AtomicU64;
-use std::sync::{Arc, Mutex, OnceLock};
+use std::sync::Arc;
 use tokio::io::AsyncWriteExt;
 use tokio::io::duplex;
 use tokio::time::{Duration as TokioDuration, Instant as TokioInstant, timeout};
@@ -48,18 +48,6 @@ fn make_idle_policy(soft_ms: u64, hard_ms: u64, grace_ms: u64) -> RelayClientIdl
     }
 }
 
-fn idle_pressure_test_lock() -> &'static Mutex<()> {
-    static TEST_LOCK: OnceLock<Mutex<()>> = OnceLock::new();
-    TEST_LOCK.get_or_init(|| Mutex::new(()))
-}
-
-fn acquire_idle_pressure_test_lock() -> std::sync::MutexGuard<'static, ()> {
-    match idle_pressure_test_lock().lock() {
-        Ok(guard) => guard,
-        Err(poisoned) => poisoned.into_inner(),
-    }
-}
-
 #[tokio::test]
 async fn idle_policy_soft_mark_then_hard_close_increments_reason_counters() {
     let (reader, _writer) = duplex(1024);
@@ -372,7 +360,7 @@ async fn stress_many_idle_sessions_fail_closed_without_hang() {
 
 #[test]
 fn pressure_evicts_oldest_idle_candidate_with_deterministic_ordering() {
-    let _guard = acquire_idle_pressure_test_lock();
+    let _guard = relay_idle_pressure_test_scope();
     clear_relay_idle_pressure_state_for_testing();
     let stats = Stats::new();
 
@@ -402,7 +390,7 @@ fn pressure_evicts_oldest_idle_candidate_with_deterministic_ordering() {
 
 #[test]
 fn pressure_does_not_evict_without_new_pressure_signal() {
-    let _guard = acquire_idle_pressure_test_lock();
+    let _guard = relay_idle_pressure_test_scope();
     clear_relay_idle_pressure_state_for_testing();
     let stats = Stats::new();
 
@@ -421,7 +409,7 @@ fn pressure_does_not_evict_without_new_pressure_signal() {
 
 #[test]
 fn stress_pressure_eviction_preserves_fifo_across_many_candidates() {
-    let _guard = acquire_idle_pressure_test_lock();
+    let _guard = relay_idle_pressure_test_scope();
     clear_relay_idle_pressure_state_for_testing();
     let stats = Stats::new();
 
@@ -457,7 +445,7 @@ fn stress_pressure_eviction_preserves_fifo_across_many_candidates() {
 
 #[test]
 fn blackhat_single_pressure_event_must_not_evict_more_than_one_candidate() {
-    let _guard = acquire_idle_pressure_test_lock();
+    let _guard = relay_idle_pressure_test_scope();
     clear_relay_idle_pressure_state_for_testing();
     let stats = Stats::new();
 
@@ -491,7 +479,7 @@ fn blackhat_single_pressure_event_must_not_evict_more_than_one_candidate() {
 
 #[test]
 fn blackhat_pressure_counter_must_track_global_budget_not_per_session_cursor() {
-    let _guard = acquire_idle_pressure_test_lock();
+    let _guard = relay_idle_pressure_test_scope();
     clear_relay_idle_pressure_state_for_testing();
     let stats = Stats::new();
 
@@ -524,7 +512,7 @@ fn blackhat_pressure_counter_must_track_global_budget_not_per_session_cursor() {
 
 #[test]
 fn blackhat_stale_pressure_before_idle_mark_must_not_trigger_eviction() {
-    let _guard = acquire_idle_pressure_test_lock();
+    let _guard = relay_idle_pressure_test_scope();
     clear_relay_idle_pressure_state_for_testing();
     let stats = Stats::new();
 
@@ -543,7 +531,7 @@ fn blackhat_stale_pressure_before_idle_mark_must_not_trigger_eviction() {
 
 #[test]
 fn blackhat_stale_pressure_must_not_evict_any_of_newly_marked_batch() {
-    let _guard = acquire_idle_pressure_test_lock();
+    let _guard = relay_idle_pressure_test_scope();
     clear_relay_idle_pressure_state_for_testing();
     let stats = Stats::new();
 
@@ -575,7 +563,7 @@ fn blackhat_stale_pressure_must_not_evict_any_of_newly_marked_batch() {
 
 #[test]
 fn blackhat_stale_pressure_seen_without_candidates_must_be_globally_invalidated() {
-    let _guard = acquire_idle_pressure_test_lock();
+    let _guard = relay_idle_pressure_test_scope();
     clear_relay_idle_pressure_state_for_testing();
     let stats = Stats::new();
 
@@ -601,7 +589,7 @@ fn blackhat_stale_pressure_seen_without_candidates_must_be_globally_invalidated(
 
 #[test]
 fn blackhat_stale_pressure_must_not_survive_candidate_churn() {
-    let _guard = acquire_idle_pressure_test_lock();
+    let _guard = relay_idle_pressure_test_scope();
     clear_relay_idle_pressure_state_for_testing();
     let stats = Stats::new();
 
@@ -621,7 +609,7 @@ fn blackhat_stale_pressure_must_not_survive_candidate_churn() {
 
 #[test]
 fn blackhat_pressure_seq_saturation_must_not_disable_future_pressure_accounting() {
-    let _guard = acquire_idle_pressure_test_lock();
+    let _guard = relay_idle_pressure_test_scope();
     clear_relay_idle_pressure_state_for_testing();
 
     {
@@ -646,7 +634,7 @@ fn blackhat_pressure_seq_saturation_must_not_disable_future_pressure_accounting(
 
 #[test]
 fn blackhat_pressure_seq_saturation_must_not_break_multiple_distinct_events() {
-    let _guard = acquire_idle_pressure_test_lock();
+    let _guard = relay_idle_pressure_test_scope();
     clear_relay_idle_pressure_state_for_testing();
 
     {
@@ -673,7 +661,7 @@ fn blackhat_pressure_seq_saturation_must_not_break_multiple_distinct_events() {
 #[tokio::test(flavor = "multi_thread", worker_threads = 4)]
 async fn integration_race_single_pressure_event_allows_at_most_one_eviction_under_parallel_claims()
 {
-    let _guard = acquire_idle_pressure_test_lock();
+    let _guard = relay_idle_pressure_test_scope();
     clear_relay_idle_pressure_state_for_testing();
 
     let stats = Arc::new(Stats::new());
@@ -738,7 +726,7 @@ async fn integration_race_single_pressure_event_allows_at_most_one_eviction_unde
 
 #[tokio::test(flavor = "multi_thread", worker_threads = 4)]
 async fn integration_race_burst_pressure_with_churn_preserves_empty_set_invalidation_and_budget() {
-    let _guard = acquire_idle_pressure_test_lock();
+    let _guard = relay_idle_pressure_test_scope();
     clear_relay_idle_pressure_state_for_testing();
 
     let stats = Arc::new(Stats::new());

src/proxy/tests/middle_relay_idle_registry_poison_security_tests.rs

@@ -0,0 +1,59 @@
+use super::*;
+use std::panic::{AssertUnwindSafe, catch_unwind};
+
+#[test]
+fn blackhat_registry_poison_recovers_with_fail_closed_reset_and_pressure_accounting() {
+    let _guard = relay_idle_pressure_test_scope();
+    clear_relay_idle_pressure_state_for_testing();
+
+    let _ = catch_unwind(AssertUnwindSafe(|| {
+        let registry = relay_idle_candidate_registry();
+        let mut guard = registry
+            .lock()
+            .expect("registry lock must be acquired before poison");
+        guard.by_conn_id.insert(
+            999,
+            RelayIdleCandidateMeta {
+                mark_order_seq: 1,
+                mark_pressure_seq: 0,
+            },
+        );
+        guard.ordered.insert((1, 999));
+        panic!("intentional poison for idle-registry recovery");
+    }));
+
+    // Helper lock must recover from poison, reset stale state, and continue.
+    assert!(mark_relay_idle_candidate(42));
+    assert_eq!(oldest_relay_idle_candidate(), Some(42));
+
+    let before = relay_pressure_event_seq();
+    note_relay_pressure_event();
+    let after = relay_pressure_event_seq();
+    assert!(after > before, "pressure accounting must still advance after poison");
+
+    clear_relay_idle_pressure_state_for_testing();
+}
+
+#[test]
+fn clear_state_helper_must_reset_poisoned_registry_for_deterministic_fifo_tests() {
+    let _guard = relay_idle_pressure_test_scope();
+    clear_relay_idle_pressure_state_for_testing();
+
+    let _ = catch_unwind(AssertUnwindSafe(|| {
+        let registry = relay_idle_candidate_registry();
+        let _guard = registry
+            .lock()
+            .expect("registry lock must be acquired before poison");
+        panic!("intentional poison while lock held");
+    }));
+
+    clear_relay_idle_pressure_state_for_testing();
+
+    assert_eq!(oldest_relay_idle_candidate(), None);
+    assert_eq!(relay_pressure_event_seq(), 0);
+
+    assert!(mark_relay_idle_candidate(7));
+    assert_eq!(oldest_relay_idle_candidate(), Some(7));
+
+    clear_relay_idle_pressure_state_for_testing();
+}

src/proxy/tests/middle_relay_quota_overflow_lock_security_tests.rs

@@ -1,131 +0,0 @@
-use super::*;
-use dashmap::DashMap;
-use std::sync::Arc;
-
-#[test]
-fn saturation_uses_stable_overflow_lock_without_cache_growth() {
-    let _guard = super::quota_user_lock_test_scope();
-    let map = QUOTA_USER_LOCKS.get_or_init(DashMap::new);
-    map.clear();
-
-    let prefix = format!("middle-quota-held-{}", std::process::id());
-    let mut retained = Vec::with_capacity(QUOTA_USER_LOCKS_MAX);
-    for idx in 0..QUOTA_USER_LOCKS_MAX {
-        retained.push(quota_user_lock(&format!("{prefix}-{idx}")));
-    }
-
-    assert_eq!(map.len(), QUOTA_USER_LOCKS_MAX);
-
-    let user = format!("middle-quota-overflow-{}", std::process::id());
-    let first = quota_user_lock(&user);
-    let second = quota_user_lock(&user);
-
-    assert!(
-        Arc::ptr_eq(&first, &second),
-        "overflow user must get deterministic same lock while cache is saturated"
-    );
-    assert_eq!(
-        map.len(),
-        QUOTA_USER_LOCKS_MAX,
-        "overflow path must not grow bounded lock map"
-    );
-    assert!(
-        map.get(&user).is_none(),
-        "overflow user should stay outside bounded lock map under saturation"
-    );
-
-    drop(retained);
-}
-
-#[test]
-fn overflow_striping_keeps_different_users_distributed() {
-    let _guard = super::quota_user_lock_test_scope();
-    let map = QUOTA_USER_LOCKS.get_or_init(DashMap::new);
-    map.clear();
-
-    let prefix = format!("middle-quota-dist-held-{}", std::process::id());
-    let mut retained = Vec::with_capacity(QUOTA_USER_LOCKS_MAX);
-    for idx in 0..QUOTA_USER_LOCKS_MAX {
-        retained.push(quota_user_lock(&format!("{prefix}-{idx}")));
-    }
-
-    let a = quota_user_lock("middle-overflow-user-a");
-    let b = quota_user_lock("middle-overflow-user-b");
-    let c = quota_user_lock("middle-overflow-user-c");
-
-    let distinct = [
-        Arc::as_ptr(&a) as usize,
-        Arc::as_ptr(&b) as usize,
-        Arc::as_ptr(&c) as usize,
-    ]
-    .iter()
-    .copied()
-    .collect::<std::collections::HashSet<_>>()
-    .len();
-
-    assert!(
-        distinct >= 2,
-        "striped overflow lock set should avoid collapsing all users to one lock"
-    );
-
-    drop(retained);
-}
-
-#[test]
-fn reclaim_path_caches_new_user_after_stale_entries_drop() {
-    let _guard = super::quota_user_lock_test_scope();
-    let map = QUOTA_USER_LOCKS.get_or_init(DashMap::new);
-    map.clear();
-
-    let prefix = format!("middle-quota-reclaim-held-{}", std::process::id());
-    let mut retained = Vec::with_capacity(QUOTA_USER_LOCKS_MAX);
-    for idx in 0..QUOTA_USER_LOCKS_MAX {
-        retained.push(quota_user_lock(&format!("{prefix}-{idx}")));
-    }
-
-    drop(retained);
-
-    let user = format!("middle-quota-reclaim-user-{}", std::process::id());
-    let got = quota_user_lock(&user);
-    assert!(map.get(&user).is_some());
-    assert!(
-        Arc::strong_count(&got) >= 2,
-        "after reclaim, lock should be held both by caller and map"
-    );
-}
-
-#[test]
-fn overflow_path_same_user_is_stable_across_parallel_threads() {
-    let _guard = super::quota_user_lock_test_scope();
-    let map = QUOTA_USER_LOCKS.get_or_init(DashMap::new);
-    map.clear();
-
-    let mut retained = Vec::with_capacity(QUOTA_USER_LOCKS_MAX);
-    for idx in 0..QUOTA_USER_LOCKS_MAX {
-        retained.push(quota_user_lock(&format!(
-            "middle-quota-thread-held-{}-{idx}",
-            std::process::id()
-        )));
-    }
-
-    let user = format!("middle-quota-overflow-thread-user-{}", std::process::id());
-    let mut workers = Vec::new();
-    for _ in 0..32 {
-        let user = user.clone();
-        workers.push(std::thread::spawn(move || quota_user_lock(&user)));
-    }
-
-    let first = workers
-        .remove(0)
-        .join()
-        .expect("thread must return lock handle");
-    for worker in workers {
-        let got = worker.join().expect("thread must return lock handle");
-        assert!(
-            Arc::ptr_eq(&first, &got),
-            "same overflow user should resolve to one striped lock even under contention"
-        );
-    }
-
-    drop(retained);
-}

src/proxy/tests/middle_relay_tiny_frame_debt_concurrency_security_tests.rs

@@ -0,0 +1,361 @@
+use super::*;
+use crate::crypto::AesCtr;
+use crate::stats::Stats;
+use crate::stream::{BufferPool, CryptoReader};
+use std::sync::Arc;
+use std::sync::atomic::AtomicU64;
+use std::time::Instant;
+use tokio::io::{AsyncRead, AsyncWriteExt, duplex};
+use tokio::task::JoinSet;
+use tokio::time::{Duration as TokioDuration, sleep};
+
+fn make_crypto_reader<T>(reader: T) -> CryptoReader<T>
+where
+    T: AsyncRead + Unpin + Send + 'static,
+{
+    let key = [0u8; 32];
+    let iv = 0u128;
+    CryptoReader::new(reader, AesCtr::new(&key, iv))
+}
+
+fn encrypt_for_reader(plaintext: &[u8]) -> Vec<u8> {
+    let key = [0u8; 32];
+    let iv = 0u128;
+    let mut cipher = AesCtr::new(&key, iv);
+    cipher.encrypt(plaintext)
+}
+
+fn make_forensics(conn_id: u64, started_at: Instant) -> RelayForensicsState {
+    RelayForensicsState {
+        trace_id: 0xB200_0000 + conn_id,
+        conn_id,
+        user: format!("tiny-frame-debt-concurrency-user-{conn_id}"),
+        peer: "127.0.0.1:50000".parse().expect("peer parse must succeed"),
+        peer_hash: hash_ip("127.0.0.1".parse().expect("ip parse must succeed")),
+        started_at,
+        bytes_c2me: 0,
+        bytes_me2c: Arc::new(AtomicU64::new(0)),
+        desync_all_full: false,
+    }
+}
+
+fn make_enabled_idle_policy() -> RelayClientIdlePolicy {
+    RelayClientIdlePolicy {
+        enabled: true,
+        soft_idle: Duration::from_millis(50),
+        hard_idle: Duration::from_millis(120),
+        grace_after_downstream_activity: Duration::from_secs(0),
+        legacy_frame_read_timeout: Duration::from_millis(50),
+    }
+}
+
+async fn read_once(
+    crypto_reader: &mut CryptoReader<tokio::io::DuplexStream>,
+    proto: ProtoTag,
+    forensics: &RelayForensicsState,
+    frame_counter: &mut u64,
+    idle_state: &mut RelayClientIdleState,
+) -> Result<Option<(PooledBuffer, bool)>> {
+    let buffer_pool = Arc::new(BufferPool::new());
+    let stats = Stats::new();
+    let idle_policy = make_enabled_idle_policy();
+    let last_downstream_activity_ms = AtomicU64::new(0);
+    read_client_payload_with_idle_policy(
+        crypto_reader,
+        proto,
+        1024,
+        &buffer_pool,
+        forensics,
+        frame_counter,
+        &stats,
+        &idle_policy,
+        idle_state,
+        &last_downstream_activity_ms,
+        forensics.started_at,
+    )
+    .await
+}
+
+#[tokio::test(flavor = "multi_thread", worker_threads = 4)]
+async fn stress_parallel_pure_tiny_floods_all_fail_closed() {
+    let mut set = JoinSet::new();
+
+    for idx in 0..32u64 {
+        set.spawn(async move {
+            let (reader, mut writer) = duplex(4096);
+            let mut crypto_reader = make_crypto_reader(reader);
+            let started = Instant::now();
+            let forensics = make_forensics(1000 + idx, started);
+            let mut frame_counter = 0u64;
+            let mut idle_state = RelayClientIdleState::new(started);
+
+            let flood_plaintext = vec![0u8; 1024];
+            let flood_encrypted = encrypt_for_reader(&flood_plaintext);
+            writer.write_all(&flood_encrypted).await.unwrap();
+            drop(writer);
+
+            let result = run_relay_test_step_timeout(
+                "tiny flood task",
+                read_once(
+                    &mut crypto_reader,
+                    ProtoTag::Abridged,
+                    &forensics,
+                    &mut frame_counter,
+                    &mut idle_state,
+                ),
+            )
+            .await;
+
+            assert!(matches!(result, Err(ProxyError::Proxy(_))));
+            assert_eq!(frame_counter, 0);
+        });
+    }
+
+    while let Some(result) = set.join_next().await {
+        result.expect("parallel tiny flood worker must not panic");
+    }
+}
+
+#[tokio::test(flavor = "multi_thread", worker_threads = 4)]
+async fn stress_parallel_benign_tiny_burst_then_real_all_pass() {
+    let mut set = JoinSet::new();
+
+    for idx in 0..24u64 {
+        set.spawn(async move {
+            let (reader, mut writer) = duplex(2048);
+            let mut crypto_reader = make_crypto_reader(reader);
+            let started = Instant::now();
+            let forensics = make_forensics(2000 + idx, started);
+            let mut frame_counter = 0u64;
+            let mut idle_state = RelayClientIdleState::new(started);
+
+            let payload = [idx as u8, 2, 3, 4];
+            let mut plaintext = Vec::with_capacity(20);
+            for _ in 0..6 {
+                plaintext.push(0x00);
+            }
+            plaintext.push(0x01);
+            plaintext.extend_from_slice(&payload);
+            let encrypted = encrypt_for_reader(&plaintext);
+            writer.write_all(&encrypted).await.unwrap();
+
+            let result = run_relay_test_step_timeout(
+                "benign tiny burst read",
+                read_once(
+                    &mut crypto_reader,
+                    ProtoTag::Abridged,
+                    &forensics,
+                    &mut frame_counter,
+                    &mut idle_state,
+                ),
+            )
+            .await
+            .expect("benign payload must parse")
+            .expect("benign payload must return frame");
+
+            assert_eq!(result.0.as_ref(), &payload);
+            assert_eq!(frame_counter, 1);
+        });
+    }
+
+    while let Some(result) = set.join_next().await {
+        result.expect("parallel benign worker must not panic");
+    }
+}
+
+#[tokio::test(flavor = "multi_thread", worker_threads = 4)]
+async fn adversarial_lockstep_alternating_attack_under_jitter_closes() {
+    let mut set = JoinSet::new();
+
+    for idx in 0..12u64 {
+        set.spawn(async move {
+            let (reader, mut writer) = duplex(8192);
+            let mut crypto_reader = make_crypto_reader(reader);
+            let started = Instant::now();
+            let forensics = make_forensics(3000 + idx, started);
+            let mut frame_counter = 0u64;
+            let mut idle_state = RelayClientIdleState::new(started);
+
+            let mut plaintext = Vec::with_capacity(2000);
+            for n in 0..180u8 {
+                plaintext.push(0x00);
+                plaintext.push(0x01);
+                plaintext.extend_from_slice(&[n, n ^ 0x21, n ^ 0x42, n ^ 0x84]);
+            }
+            let encrypted = encrypt_for_reader(&plaintext);
+
+            let writer_task = tokio::spawn(async move {
+                for chunk in encrypted.chunks(17) {
+                    writer.write_all(chunk).await.unwrap();
+                    sleep(TokioDuration::from_millis(1)).await;
+                }
+                drop(writer);
+            });
+
+            let mut closed = false;
+            for _ in 0..220 {
+                let result = run_relay_test_step_timeout(
+                    "alternating jitter read step",
+                    read_once(
+                        &mut crypto_reader,
+                        ProtoTag::Abridged,
+                        &forensics,
+                        &mut frame_counter,
+                        &mut idle_state,
+                    ),
+                )
+                .await;
+
+                match result {
+                    Ok(Some((_payload, _))) => {}
+                    Err(ProxyError::Proxy(_)) => {
+                        closed = true;
+                        break;
+                    }
+                    Ok(None) => break,
+                    Err(other) => panic!("unexpected error in alternating jitter case: {other}"),
+                }
+            }
+
+            writer_task.await.expect("writer jitter task must not panic");
+            assert!(closed, "alternating attack must close before EOF");
+        });
+    }
+
+    while let Some(result) = set.join_next().await {
+        result.expect("alternating jitter worker must not panic");
+    }
+}
+
+#[tokio::test(flavor = "multi_thread", worker_threads = 4)]
+async fn integration_mixed_population_attackers_close_benign_survive() {
+    let mut set = JoinSet::new();
+
+    for idx in 0..20u64 {
+        set.spawn(async move {
+            let (reader, mut writer) = duplex(4096);
+            let mut crypto_reader = make_crypto_reader(reader);
+            let started = Instant::now();
+            let forensics = make_forensics(4000 + idx, started);
+            let mut frame_counter = 0u64;
+            let mut idle_state = RelayClientIdleState::new(started);
+
+            if idx % 2 == 0 {
+                let mut plaintext = Vec::with_capacity(1280);
+                for n in 0..140u8 {
+                    plaintext.push(0x00);
+                    plaintext.push(0x01);
+                    plaintext.extend_from_slice(&[n, n, n, n]);
+                }
+                writer.write_all(&encrypt_for_reader(&plaintext)).await.unwrap();
+                drop(writer);
+
+                let mut closed = false;
+                for _ in 0..200 {
+                    match read_once(
+                        &mut crypto_reader,
+                        ProtoTag::Abridged,
+                        &forensics,
+                        &mut frame_counter,
+                        &mut idle_state,
+                    )
+                    .await
+                    {
+                        Ok(Some(_)) => {}
+                        Err(ProxyError::Proxy(_)) => {
+                            closed = true;
+                            break;
+                        }
+                        Ok(None) => break,
+                        Err(other) => panic!("unexpected attacker error: {other}"),
+                    }
+                }
+                assert!(closed, "attacker session must fail closed");
+            } else {
+                let payload = [1u8, 9, 8, 7];
+                let mut plaintext = Vec::new();
+                for _ in 0..4 {
+                    plaintext.push(0x00);
+                }
+                plaintext.push(0x01);
+                plaintext.extend_from_slice(&payload);
+                writer.write_all(&encrypt_for_reader(&plaintext)).await.unwrap();
+
+                let got = read_once(
+                    &mut crypto_reader,
+                    ProtoTag::Abridged,
+                    &forensics,
+                    &mut frame_counter,
+                    &mut idle_state,
+                )
+                .await
+                .expect("benign session must parse")
+                .expect("benign session must return a frame");
+                assert_eq!(got.0.as_ref(), &payload);
+            }
+        });
+    }
+
+    while let Some(result) = set.join_next().await {
+        result.expect("mixed-population worker must not panic");
+    }
+}
+
+#[tokio::test(flavor = "multi_thread", worker_threads = 4)]
+async fn light_fuzz_parallel_patterns_no_hang_or_panic() {
+    let mut set = JoinSet::new();
+
+    for case in 0..40u64 {
+        set.spawn(async move {
+            let (reader, mut writer) = duplex(8192);
+            let mut crypto_reader = make_crypto_reader(reader);
+            let started = Instant::now();
+            let forensics = make_forensics(5000 + case, started);
+            let mut frame_counter = 0u64;
+            let mut idle_state = RelayClientIdleState::new(started);
+
+            let mut seed = 0x9E37_79B9u64 ^ (case << 8);
+            let mut plaintext = Vec::with_capacity(2048);
+            for _ in 0..256 {
+                seed ^= seed << 7;
+                seed ^= seed >> 9;
+                seed ^= seed << 8;
+                let is_tiny = (seed & 1) == 0;
+                if is_tiny {
+                    plaintext.push(0x00);
+                } else {
+                    plaintext.push(0x01);
+                    plaintext.extend_from_slice(&[(seed >> 8) as u8, 2, 3, 4]);
+                }
+            }
+
+            writer.write_all(&encrypt_for_reader(&plaintext)).await.unwrap();
+            drop(writer);
+
+            for _ in 0..320 {
+                let step = run_relay_test_step_timeout(
+                    "fuzz case read step",
+                    read_once(
+                        &mut crypto_reader,
+                        ProtoTag::Abridged,
+                        &forensics,
+                        &mut frame_counter,
+                        &mut idle_state,
+                    ),
+                )
+                .await;
+
+                match step {
+                    Ok(Some(_)) => {}
+                    Err(ProxyError::Proxy(_)) => break,
+                    Ok(None) => break,
+                    Err(other) => panic!("unexpected fuzz case error: {other}"),
+                }
+            }
+        });
+    }
+
+    while let Some(result) = set.join_next().await {
+        result.expect("fuzz worker must not panic");
+    }
+}

src/proxy/tests/middle_relay_tiny_frame_debt_proto_chunking_security_tests.rs

@@ -0,0 +1,425 @@
+use super::*;
+use crate::crypto::AesCtr;
+use crate::stats::Stats;
+use crate::stream::{BufferPool, CryptoReader, PooledBuffer};
+use std::sync::Arc;
+use std::sync::atomic::AtomicU64;
+use std::time::Instant;
+use tokio::io::{AsyncRead, AsyncWriteExt, duplex};
+use tokio::time::{Duration as TokioDuration, sleep};
+
+fn make_crypto_reader<T>(reader: T) -> CryptoReader<T>
+where
+    T: AsyncRead + Unpin + Send + 'static,
+{
+    let key = [0u8; 32];
+    let iv = 0u128;
+    CryptoReader::new(reader, AesCtr::new(&key, iv))
+}
+
+fn encrypt_for_reader(plaintext: &[u8]) -> Vec<u8> {
+    let key = [0u8; 32];
+    let iv = 0u128;
+    let mut cipher = AesCtr::new(&key, iv);
+    cipher.encrypt(plaintext)
+}
+
+fn make_forensics(conn_id: u64, started_at: Instant) -> RelayForensicsState {
+    RelayForensicsState {
+        trace_id: 0xB300_0000 + conn_id,
+        conn_id,
+        user: format!("tiny-frame-debt-proto-chunk-user-{conn_id}"),
+        peer: "127.0.0.1:50000".parse().expect("peer parse must succeed"),
+        peer_hash: hash_ip("127.0.0.1".parse().expect("ip parse must succeed")),
+        started_at,
+        bytes_c2me: 0,
+        bytes_me2c: Arc::new(AtomicU64::new(0)),
+        desync_all_full: false,
+    }
+}
+
+fn make_enabled_idle_policy() -> RelayClientIdlePolicy {
+    RelayClientIdlePolicy {
+        enabled: true,
+        soft_idle: Duration::from_millis(50),
+        hard_idle: Duration::from_millis(120),
+        grace_after_downstream_activity: Duration::from_secs(0),
+        legacy_frame_read_timeout: Duration::from_millis(50),
+    }
+}
+
+fn append_tiny_frame(plaintext: &mut Vec<u8>, proto: ProtoTag) {
+    match proto {
+        ProtoTag::Abridged => plaintext.push(0x00),
+        ProtoTag::Intermediate | ProtoTag::Secure => plaintext.extend_from_slice(&0u32.to_le_bytes()),
+    }
+}
+
+fn append_real_frame(plaintext: &mut Vec<u8>, proto: ProtoTag, payload: [u8; 4]) {
+    match proto {
+        ProtoTag::Abridged => {
+            plaintext.push(0x01);
+            plaintext.extend_from_slice(&payload);
+        }
+        ProtoTag::Intermediate | ProtoTag::Secure => {
+            plaintext.extend_from_slice(&4u32.to_le_bytes());
+            plaintext.extend_from_slice(&payload);
+        }
+    }
+}
+
+async fn write_chunked_with_jitter(
+    writer: &mut tokio::io::DuplexStream,
+    bytes: &[u8],
+    mut seed: u64,
+) {
+    let mut offset = 0usize;
+    while offset < bytes.len() {
+        seed ^= seed << 7;
+        seed ^= seed >> 9;
+        seed ^= seed << 8;
+        let chunk_len = 1 + ((seed as usize) & 0x1f);
+        let end = (offset + chunk_len).min(bytes.len());
+        writer.write_all(&bytes[offset..end]).await.unwrap();
+
+        let delay_ms = ((seed >> 16) % 3) as u64;
+        if delay_ms > 0 {
+            sleep(TokioDuration::from_millis(delay_ms)).await;
+        }
+        offset = end;
+    }
+}
+
+async fn read_once_with_state(
+    crypto_reader: &mut CryptoReader<tokio::io::DuplexStream>,
+    proto: ProtoTag,
+    forensics: &RelayForensicsState,
+    frame_counter: &mut u64,
+    idle_state: &mut RelayClientIdleState,
+) -> Result<Option<(PooledBuffer, bool)>> {
+    let buffer_pool = Arc::new(BufferPool::new());
+    let stats = Stats::new();
+    let idle_policy = make_enabled_idle_policy();
+    let last_downstream_activity_ms = AtomicU64::new(0);
+    read_client_payload_with_idle_policy(
+        crypto_reader,
+        proto,
+        1024,
+        &buffer_pool,
+        forensics,
+        frame_counter,
+        &stats,
+        &idle_policy,
+        idle_state,
+        &last_downstream_activity_ms,
+        forensics.started_at,
+    )
+    .await
+}
+
+fn is_fail_closed_outcome(result: &Result<Option<(PooledBuffer, bool)>>) -> bool {
+    matches!(result, Err(ProxyError::Proxy(_)))
+        || matches!(result, Err(ProxyError::Io(e)) if e.kind() == std::io::ErrorKind::TimedOut)
+}
+
+#[tokio::test]
+async fn intermediate_chunked_zero_flood_fail_closed() {
+    let (reader, mut writer) = duplex(4096);
+    let mut crypto_reader = make_crypto_reader(reader);
+    let started = Instant::now();
+    let forensics = make_forensics(6101, started);
+    let mut frame_counter = 0u64;
+    let mut idle_state = RelayClientIdleState::new(started);
+
+    let mut plaintext = Vec::with_capacity(4 * 256);
+    for _ in 0..256 {
+        append_tiny_frame(&mut plaintext, ProtoTag::Intermediate);
+    }
+    let encrypted = encrypt_for_reader(&plaintext);
+    write_chunked_with_jitter(&mut writer, &encrypted, 0x1111_2222).await;
+    drop(writer);
+
+    let result = run_relay_test_step_timeout(
+        "intermediate flood read",
+        read_once_with_state(
+            &mut crypto_reader,
+            ProtoTag::Intermediate,
+            &forensics,
+            &mut frame_counter,
+            &mut idle_state,
+        ),
+    )
+    .await;
+
+    assert!(
+        is_fail_closed_outcome(&result),
+        "zero-length flood must fail closed via debt guard or idle timeout"
+    );
+    assert_eq!(frame_counter, 0);
+}
+
+#[tokio::test]
+async fn secure_chunked_zero_flood_fail_closed() {
+    let (reader, mut writer) = duplex(4096);
+    let mut crypto_reader = make_crypto_reader(reader);
+    let started = Instant::now();
+    let forensics = make_forensics(6102, started);
+    let mut frame_counter = 0u64;
+    let mut idle_state = RelayClientIdleState::new(started);
+
+    let mut plaintext = Vec::with_capacity(4 * 256);
+    for _ in 0..256 {
+        append_tiny_frame(&mut plaintext, ProtoTag::Secure);
+    }
+    let encrypted = encrypt_for_reader(&plaintext);
+    write_chunked_with_jitter(&mut writer, &encrypted, 0x3333_4444).await;
+    drop(writer);
+
+    let result = run_relay_test_step_timeout(
+        "secure flood read",
+        read_once_with_state(
+            &mut crypto_reader,
+            ProtoTag::Secure,
+            &forensics,
+            &mut frame_counter,
+            &mut idle_state,
+        ),
+    )
+    .await;
+
+    assert!(
+        is_fail_closed_outcome(&result),
+        "secure zero-length flood must fail closed via debt guard or idle timeout"
+    );
+    assert_eq!(frame_counter, 0);
+}
+
+#[tokio::test]
+async fn intermediate_chunked_alternating_attack_closes_before_eof() {
+    let (reader, mut writer) = duplex(8192);
+    let mut crypto_reader = make_crypto_reader(reader);
+    let started = Instant::now();
+    let forensics = make_forensics(6103, started);
+    let mut frame_counter = 0u64;
+    let mut idle_state = RelayClientIdleState::new(started);
+
+    let mut plaintext = Vec::with_capacity(8 * 200);
+    for n in 0..180u8 {
+        append_tiny_frame(&mut plaintext, ProtoTag::Intermediate);
+        append_real_frame(&mut plaintext, ProtoTag::Intermediate, [n, n ^ 1, n ^ 2, n ^ 3]);
+    }
+    let encrypted = encrypt_for_reader(&plaintext);
+
+    let writer_task = tokio::spawn(async move {
+        write_chunked_with_jitter(&mut writer, &encrypted, 0x5555_6666).await;
+        drop(writer);
+    });
+
+    let mut closed = false;
+    for _ in 0..240 {
+        let step = run_relay_test_step_timeout(
+            "intermediate alternating read step",
+            read_once_with_state(
+                &mut crypto_reader,
+                ProtoTag::Intermediate,
+                &forensics,
+                &mut frame_counter,
+                &mut idle_state,
+            ),
+        )
+        .await;
+
+        match step {
+            Ok(Some(_)) => {}
+            Err(ProxyError::Proxy(_)) => {
+                closed = true;
+                break;
+            }
+            Ok(None) => break,
+            Err(other) => panic!("unexpected intermediate alternating error: {other}"),
+        }
+    }
+
+    writer_task.await.expect("intermediate writer task must not panic");
+    assert!(closed, "intermediate alternating attack must fail closed");
+}
+
+#[tokio::test]
+async fn secure_chunked_alternating_attack_closes_before_eof() {
+    let (reader, mut writer) = duplex(8192);
+    let mut crypto_reader = make_crypto_reader(reader);
+    let started = Instant::now();
+    let forensics = make_forensics(6104, started);
+    let mut frame_counter = 0u64;
+    let mut idle_state = RelayClientIdleState::new(started);
+
+    let mut plaintext = Vec::with_capacity(8 * 200);
+    for n in 0..180u8 {
+        append_tiny_frame(&mut plaintext, ProtoTag::Secure);
+        append_real_frame(&mut plaintext, ProtoTag::Secure, [n, n ^ 7, n ^ 11, n ^ 19]);
+    }
+    let encrypted = encrypt_for_reader(&plaintext);
+
+    let writer_task = tokio::spawn(async move {
+        write_chunked_with_jitter(&mut writer, &encrypted, 0x7777_8888).await;
+        drop(writer);
+    });
+
+    let mut closed = false;
+    for _ in 0..240 {
+        let step = run_relay_test_step_timeout(
+            "secure alternating read step",
+            read_once_with_state(
+                &mut crypto_reader,
+                ProtoTag::Secure,
+                &forensics,
+                &mut frame_counter,
+                &mut idle_state,
+            ),
+        )
+        .await;
+
+        match step {
+            Ok(Some(_)) => {}
+            Err(ProxyError::Proxy(_)) => {
+                closed = true;
+                break;
+            }
+            Ok(None) => break,
+            Err(other) => panic!("unexpected secure alternating error: {other}"),
+        }
+    }
+
+    writer_task.await.expect("secure writer task must not panic");
+    assert!(closed, "secure alternating attack must fail closed");
+}
+
+#[tokio::test]
+async fn intermediate_chunked_safe_small_burst_still_returns_real_frame() {
+    let (reader, mut writer) = duplex(1024);
+    let mut crypto_reader = make_crypto_reader(reader);
+    let started = Instant::now();
+    let forensics = make_forensics(6105, started);
+    let mut frame_counter = 0u64;
+    let mut idle_state = RelayClientIdleState::new(started);
+
+    let payload = [9u8, 8, 7, 6];
+    let mut plaintext = Vec::new();
+    for _ in 0..7 {
+        append_tiny_frame(&mut plaintext, ProtoTag::Intermediate);
+    }
+    append_real_frame(&mut plaintext, ProtoTag::Intermediate, payload);
+    let encrypted = encrypt_for_reader(&plaintext);
+    write_chunked_with_jitter(&mut writer, &encrypted, 0xAAAA_BBBB).await;
+
+    let result = read_once_with_state(
+        &mut crypto_reader,
+        ProtoTag::Intermediate,
+        &forensics,
+        &mut frame_counter,
+        &mut idle_state,
+    )
+    .await
+    .expect("intermediate safe burst should parse")
+    .expect("intermediate safe burst should return a frame");
+
+    assert_eq!(result.0.as_ref(), &payload);
+    assert_eq!(frame_counter, 1);
+}
+
+#[tokio::test]
+async fn secure_chunked_safe_small_burst_still_returns_real_frame() {
+    let (reader, mut writer) = duplex(1024);
+    let mut crypto_reader = make_crypto_reader(reader);
+    let started = Instant::now();
+    let forensics = make_forensics(6106, started);
+    let mut frame_counter = 0u64;
+    let mut idle_state = RelayClientIdleState::new(started);
+
+    let payload = [3u8, 1, 4, 1];
+    let mut plaintext = Vec::new();
+    for _ in 0..7 {
+        append_tiny_frame(&mut plaintext, ProtoTag::Secure);
+    }
+    append_real_frame(&mut plaintext, ProtoTag::Secure, payload);
+    let encrypted = encrypt_for_reader(&plaintext);
+    write_chunked_with_jitter(&mut writer, &encrypted, 0xCCCC_DDDD).await;
+
+    let result = read_once_with_state(
+        &mut crypto_reader,
+        ProtoTag::Secure,
+        &forensics,
+        &mut frame_counter,
+        &mut idle_state,
+    )
+    .await
+    .expect("secure safe burst should parse")
+    .expect("secure safe burst should return a frame");
+
+    assert_eq!(result.0.as_ref(), &payload);
+    assert_eq!(frame_counter, 1);
+}
+
+#[tokio::test]
+async fn light_fuzz_proto_chunking_outcomes_are_bounded() {
+    let mut seed = 0xDEAD_BEEF_2026_0322u64;
+
+    for case in 0..48u64 {
+        seed ^= seed << 7;
+        seed ^= seed >> 9;
+        seed ^= seed << 8;
+
+        let proto = if (seed & 1) == 0 {
+            ProtoTag::Intermediate
+        } else {
+            ProtoTag::Secure
+        };
+
+        let (reader, mut writer) = duplex(8192);
+        let mut crypto_reader = make_crypto_reader(reader);
+        let started = Instant::now();
+        let forensics = make_forensics(6200 + case, started);
+        let mut frame_counter = 0u64;
+        let mut idle_state = RelayClientIdleState::new(started);
+
+        let mut stream = Vec::new();
+        let mut local_seed = seed ^ case;
+        for _ in 0..220 {
+            local_seed ^= local_seed << 7;
+            local_seed ^= local_seed >> 9;
+            local_seed ^= local_seed << 8;
+            if (local_seed & 1) == 0 {
+                append_tiny_frame(&mut stream, proto);
+            } else {
+                let b = (local_seed >> 8) as u8;
+                append_real_frame(&mut stream, proto, [b, b ^ 0x12, b ^ 0x24, b ^ 0x48]);
+            }
+        }
+
+        let encrypted = encrypt_for_reader(&stream);
+        write_chunked_with_jitter(&mut writer, &encrypted, seed ^ 0x1234_5678).await;
+        drop(writer);
+
+        for _ in 0..260 {
+            let step = run_relay_test_step_timeout(
+                "fuzz proto read step",
+                read_once_with_state(
+                    &mut crypto_reader,
+                    proto,
+                    &forensics,
+                    &mut frame_counter,
+                    &mut idle_state,
+                ),
+            )
+            .await;
+
+            match step {
+                Ok(Some((_payload, _))) => {}
+                Err(ProxyError::Proxy(_)) => break,
+                Err(ProxyError::Io(e)) if e.kind() == std::io::ErrorKind::TimedOut => break,
+                Ok(None) => break,
+                Err(other) => panic!("unexpected proto chunking fuzz error: {other}"),
+            }
+        }
+    }
+}

src/proxy/tests/middle_relay_tiny_frame_debt_security_tests.rs

@@ -0,0 +1,798 @@
+use super::*;
+use crate::crypto::AesCtr;
+use crate::stats::Stats;
+use crate::stream::{BufferPool, CryptoReader};
+use std::sync::atomic::AtomicU64;
+use std::sync::Arc;
+use std::time::Instant;
+use tokio::io::{AsyncRead, AsyncWriteExt, duplex};
+
+fn make_crypto_reader<T>(reader: T) -> CryptoReader<T>
+where
+    T: AsyncRead + Unpin + Send + 'static,
+{
+    let key = [0u8; 32];
+    let iv = 0u128;
+    CryptoReader::new(reader, AesCtr::new(&key, iv))
+}
+
+fn encrypt_for_reader(plaintext: &[u8]) -> Vec<u8> {
+    let key = [0u8; 32];
+    let iv = 0u128;
+    let mut cipher = AesCtr::new(&key, iv);
+    cipher.encrypt(plaintext)
+}
+
+fn make_forensics(conn_id: u64, started_at: Instant) -> RelayForensicsState {
+    RelayForensicsState {
+        trace_id: 0xB100_0000 + conn_id,
+        conn_id,
+        user: format!("tiny-frame-debt-user-{conn_id}"),
+        peer: "127.0.0.1:50000".parse().expect("peer parse must succeed"),
+        peer_hash: hash_ip("127.0.0.1".parse().expect("ip parse must succeed")),
+        started_at,
+        bytes_c2me: 0,
+        bytes_me2c: Arc::new(AtomicU64::new(0)),
+        desync_all_full: false,
+    }
+}
+
+fn make_enabled_idle_policy() -> RelayClientIdlePolicy {
+    RelayClientIdlePolicy {
+        enabled: true,
+        soft_idle: Duration::from_millis(50),
+        hard_idle: Duration::from_millis(120),
+        grace_after_downstream_activity: Duration::from_secs(0),
+        legacy_frame_read_timeout: Duration::from_millis(50),
+    }
+}
+
+async fn read_bounded(
+    crypto_reader: &mut CryptoReader<tokio::io::DuplexStream>,
+    proto_tag: ProtoTag,
+    buffer_pool: &Arc<BufferPool>,
+    forensics: &RelayForensicsState,
+    frame_counter: &mut u64,
+    stats: &Stats,
+    idle_policy: &RelayClientIdlePolicy,
+    idle_state: &mut RelayClientIdleState,
+    last_downstream_activity_ms: &AtomicU64,
+    session_started_at: Instant,
+) -> Result<Option<(PooledBuffer, bool)>> {
+    run_relay_test_step_timeout(
+        "tiny-frame debt read step",
+        read_client_payload_with_idle_policy(
+            crypto_reader,
+            proto_tag,
+            1024,
+            buffer_pool,
+            forensics,
+            frame_counter,
+            stats,
+            idle_policy,
+            idle_state,
+            last_downstream_activity_ms,
+            session_started_at,
+        ),
+    )
+    .await
+}
+
+fn simulate_tiny_debt_pattern(pattern: &[bool], max_steps: usize) -> (Option<usize>, u32, usize) {
+    let mut debt = 0u32;
+    let mut reals = 0usize;
+    for (idx, is_tiny) in pattern.iter().copied().take(max_steps).enumerate() {
+        if is_tiny {
+            debt = debt.saturating_add(TINY_FRAME_DEBT_PER_TINY);
+            if debt >= TINY_FRAME_DEBT_LIMIT {
+                return (Some(idx + 1), debt, reals);
+            }
+        } else {
+            reals = reals.saturating_add(1);
+            debt = debt.saturating_sub(1);
+        }
+    }
+    (None, debt, reals)
+}
+
+#[test]
+fn tiny_frame_debt_constants_match_security_budget_expectations() {
+    assert_eq!(TINY_FRAME_DEBT_PER_TINY, 8);
+    assert_eq!(TINY_FRAME_DEBT_LIMIT, 512);
+}
+
+#[test]
+fn relay_client_idle_state_initial_debt_is_zero() {
+    let state = RelayClientIdleState::new(Instant::now());
+    assert_eq!(state.tiny_frame_debt, 0);
+}
+
+#[test]
+fn on_client_frame_does_not_reset_tiny_frame_debt() {
+    let now = Instant::now();
+    let mut state = RelayClientIdleState::new(now);
+    state.tiny_frame_debt = 77;
+    state.on_client_frame(now);
+    assert_eq!(state.tiny_frame_debt, 77);
+}
+
+#[test]
+fn tiny_frame_debt_increment_is_saturating() {
+    let mut debt = u32::MAX - 1;
+    debt = debt.saturating_add(TINY_FRAME_DEBT_PER_TINY);
+    assert_eq!(debt, u32::MAX);
+}
+
+#[test]
+fn tiny_frame_debt_decrement_is_saturating() {
+    let mut debt = 0u32;
+    debt = debt.saturating_sub(1);
+    assert_eq!(debt, 0);
+}
+
+#[test]
+fn consecutive_tiny_frames_close_exactly_at_threshold() {
+    let max_tiny_without_close = (TINY_FRAME_DEBT_LIMIT / TINY_FRAME_DEBT_PER_TINY) as usize;
+    let pattern = vec![true; max_tiny_without_close];
+    let (closed_at, _, _) = simulate_tiny_debt_pattern(&pattern, pattern.len());
+    assert_eq!(closed_at, Some(max_tiny_without_close));
+}
+
+#[test]
+fn one_less_than_threshold_tiny_frames_do_not_close() {
+    let tiny_count = (TINY_FRAME_DEBT_LIMIT / TINY_FRAME_DEBT_PER_TINY) as usize - 1;
+    let pattern = vec![true; tiny_count];
+    let (closed_at, debt, _) = simulate_tiny_debt_pattern(&pattern, pattern.len());
+    assert_eq!(closed_at, None);
+    assert!(debt < TINY_FRAME_DEBT_LIMIT);
+}
+
+#[test]
+fn alternating_one_to_one_closes_with_bounded_real_frame_count() {
+    let mut pattern = Vec::with_capacity(512);
+    for _ in 0..256 {
+        pattern.push(true);
+        pattern.push(false);
+    }
+    let (closed_at, _, reals) = simulate_tiny_debt_pattern(&pattern, pattern.len());
+    assert!(closed_at.is_some());
+    assert!(reals <= 80, "expected bounded real frames before close, got {reals}");
+}
+
+#[test]
+fn alternating_one_to_eight_is_stable_for_long_runs() {
+    let mut pattern = Vec::with_capacity(9 * 5000);
+    for _ in 0..5000 {
+        pattern.push(true);
+        for _ in 0..8 {
+            pattern.push(false);
+        }
+    }
+    let (closed_at, debt, _) = simulate_tiny_debt_pattern(&pattern, pattern.len());
+    assert_eq!(closed_at, None);
+    assert!(debt <= TINY_FRAME_DEBT_PER_TINY);
+}
+
+#[test]
+fn alternating_one_to_seven_eventually_closes() {
+    let mut pattern = Vec::with_capacity(8 * 2000);
+    for _ in 0..2000 {
+        pattern.push(true);
+        for _ in 0..7 {
+            pattern.push(false);
+        }
+    }
+    let (closed_at, _, _) = simulate_tiny_debt_pattern(&pattern, pattern.len());
+    assert!(closed_at.is_some(), "1:7 tiny-to-real must eventually close");
+}
+
+#[test]
+fn two_tiny_one_real_closes_faster_than_one_to_one() {
+    let mut one_to_one = Vec::with_capacity(512);
+    for _ in 0..256 {
+        one_to_one.push(true);
+        one_to_one.push(false);
+    }
+
+    let mut two_to_one = Vec::with_capacity(768);
+    for _ in 0..256 {
+        two_to_one.push(true);
+        two_to_one.push(true);
+        two_to_one.push(false);
+    }
+
+    let (a_close, _, _) = simulate_tiny_debt_pattern(&one_to_one, one_to_one.len());
+    let (b_close, _, _) = simulate_tiny_debt_pattern(&two_to_one, two_to_one.len());
+    assert!(a_close.is_some() && b_close.is_some());
+    assert!(b_close.unwrap_or(usize::MAX) < a_close.unwrap_or(0));
+}
+
+#[test]
+fn burst_then_drain_can_recover_without_close() {
+    let burst_tiny = ((TINY_FRAME_DEBT_LIMIT / TINY_FRAME_DEBT_PER_TINY) / 2) as usize;
+    let mut pattern = Vec::with_capacity(burst_tiny + 600);
+    for _ in 0..burst_tiny {
+        pattern.push(true);
+    }
+    pattern.extend(std::iter::repeat_n(false, 600));
+
+    let (closed_at, debt, _) = simulate_tiny_debt_pattern(&pattern, pattern.len());
+    assert_eq!(closed_at, None);
+    assert_eq!(debt, 0);
+}
+
+#[test]
+fn light_fuzz_tiny_frame_debt_model_stays_within_bounds() {
+    let mut seed = 0xA5A5_91C3_2026_0322u64;
+    for _case in 0..128 {
+        seed ^= seed << 7;
+        seed ^= seed >> 9;
+        seed ^= seed << 8;
+
+        let len = 512 + ((seed as usize) & 0x3ff);
+        let mut pattern = Vec::with_capacity(len);
+        let mut local_seed = seed;
+        for _ in 0..len {
+            local_seed ^= local_seed << 7;
+            local_seed ^= local_seed >> 9;
+            local_seed ^= local_seed << 8;
+            pattern.push((local_seed & 1) == 0);
+        }
+
+        let (closed_at, debt, _) = simulate_tiny_debt_pattern(&pattern, pattern.len());
+        if closed_at.is_none() {
+            assert!(debt < TINY_FRAME_DEBT_LIMIT);
+        }
+        assert!(debt <= u32::MAX);
+    }
+}
+
+#[test]
+fn stress_many_independent_simulations_keep_isolated_debt_state() {
+    for idx in 0..2048usize {
+        let mut pattern = Vec::with_capacity(64);
+        for j in 0..64usize {
+            pattern.push(((idx ^ j) & 3) == 0);
+        }
+        let (_closed_at, debt, _reals) = simulate_tiny_debt_pattern(&pattern, pattern.len());
+        assert!(debt <= TINY_FRAME_DEBT_LIMIT.saturating_add(TINY_FRAME_DEBT_PER_TINY));
+    }
+}
+
+#[tokio::test]
+async fn idle_policy_enabled_intermediate_zero_length_flood_is_fail_closed() {
+    let (reader, mut writer) = duplex(4096);
+    let mut crypto_reader = make_crypto_reader(reader);
+    let buffer_pool = Arc::new(BufferPool::new());
+    let stats = Stats::new();
+    let session_started_at = Instant::now();
+    let forensics = make_forensics(11, session_started_at);
+    let mut frame_counter = 0u64;
+    let mut idle_state = RelayClientIdleState::new(session_started_at);
+    let idle_policy = make_enabled_idle_policy();
+    let last_downstream_activity_ms = AtomicU64::new(0);
+
+    let flood_plaintext = vec![0u8; 4 * 256];
+    let flood_encrypted = encrypt_for_reader(&flood_plaintext);
+    writer.write_all(&flood_encrypted).await.unwrap();
+    drop(writer);
+
+    let result = read_bounded(
+        &mut crypto_reader,
+        ProtoTag::Intermediate,
+        &buffer_pool,
+        &forensics,
+        &mut frame_counter,
+        &stats,
+        &idle_policy,
+        &mut idle_state,
+        &last_downstream_activity_ms,
+        session_started_at,
+    )
+    .await;
+
+    assert!(matches!(result, Err(ProxyError::Proxy(_))));
+}
+
+#[tokio::test]
+async fn idle_policy_enabled_secure_zero_length_flood_is_fail_closed() {
+    let (reader, mut writer) = duplex(4096);
+    let mut crypto_reader = make_crypto_reader(reader);
+    let buffer_pool = Arc::new(BufferPool::new());
+    let stats = Stats::new();
+    let session_started_at = Instant::now();
+    let forensics = make_forensics(12, session_started_at);
+    let mut frame_counter = 0u64;
+    let mut idle_state = RelayClientIdleState::new(session_started_at);
+    let idle_policy = make_enabled_idle_policy();
+    let last_downstream_activity_ms = AtomicU64::new(0);
+
+    let flood_plaintext = vec![0u8; 4 * 256];
+    let flood_encrypted = encrypt_for_reader(&flood_plaintext);
+    writer.write_all(&flood_encrypted).await.unwrap();
+    drop(writer);
+
+    let result = read_bounded(
+        &mut crypto_reader,
+        ProtoTag::Secure,
+        &buffer_pool,
+        &forensics,
+        &mut frame_counter,
+        &stats,
+        &idle_policy,
+        &mut idle_state,
+        &last_downstream_activity_ms,
+        session_started_at,
+    )
+    .await;
+
+    assert!(matches!(result, Err(ProxyError::Proxy(_))));
+}
+
+#[tokio::test]
+async fn intermediate_alternating_zero_and_real_eventually_closes() {
+    let (reader, mut writer) = duplex(8192);
+    let mut crypto_reader = make_crypto_reader(reader);
+    let buffer_pool = Arc::new(BufferPool::new());
+    let stats = Stats::new();
+    let session_started_at = Instant::now();
+    let forensics = make_forensics(13, session_started_at);
+    let mut frame_counter = 0u64;
+    let mut idle_state = RelayClientIdleState::new(session_started_at);
+    let idle_policy = make_enabled_idle_policy();
+    let last_downstream_activity_ms = AtomicU64::new(0);
+
+    let mut plaintext = Vec::with_capacity(3000);
+    for idx in 0..160u8 {
+        plaintext.extend_from_slice(&0u32.to_le_bytes());
+        plaintext.extend_from_slice(&4u32.to_le_bytes());
+        plaintext.extend_from_slice(&[idx, idx ^ 0x11, idx ^ 0x22, idx ^ 0x33]);
+    }
+    let encrypted = encrypt_for_reader(&plaintext);
+    writer.write_all(&encrypted).await.unwrap();
+    drop(writer);
+
+    let mut closed = false;
+    for _ in 0..220 {
+        let result = read_bounded(
+            &mut crypto_reader,
+            ProtoTag::Intermediate,
+            &buffer_pool,
+            &forensics,
+            &mut frame_counter,
+            &stats,
+            &idle_policy,
+            &mut idle_state,
+            &last_downstream_activity_ms,
+            session_started_at,
+        )
+        .await;
+
+        match result {
+            Ok(Some(_)) => {}
+            Err(ProxyError::Proxy(_)) => {
+                closed = true;
+                break;
+            }
+            Ok(None) => break,
+            Err(other) => panic!("unexpected error while probing alternating close: {other}"),
+        }
+    }
+
+    assert!(closed, "intermediate alternating attack must fail closed");
+}
+
+#[tokio::test]
+async fn small_tiny_burst_followed_by_real_frame_does_not_spuriously_close() {
+    let (reader, mut writer) = duplex(1024);
+    let mut crypto_reader = make_crypto_reader(reader);
+    let buffer_pool = Arc::new(BufferPool::new());
+    let stats = Stats::new();
+    let session_started_at = Instant::now();
+    let forensics = make_forensics(14, session_started_at);
+    let mut frame_counter = 0u64;
+    let mut idle_state = RelayClientIdleState::new(session_started_at);
+    let idle_policy = make_enabled_idle_policy();
+    let last_downstream_activity_ms = AtomicU64::new(0);
+
+    let mut plaintext = Vec::with_capacity(64);
+    for _ in 0..8 {
+        plaintext.push(0x00);
+    }
+    plaintext.push(0x01);
+    plaintext.extend_from_slice(&[1, 2, 3, 4]);
+
+    let encrypted = encrypt_for_reader(&plaintext);
+    writer.write_all(&encrypted).await.unwrap();
+
+    let first = read_bounded(
+        &mut crypto_reader,
+        ProtoTag::Abridged,
+        &buffer_pool,
+        &forensics,
+        &mut frame_counter,
+        &stats,
+        &idle_policy,
+        &mut idle_state,
+        &last_downstream_activity_ms,
+        session_started_at,
+    )
+    .await;
+
+    match first {
+        Ok(Some((payload, _))) => assert_eq!(payload.as_ref(), &[1, 2, 3, 4]),
+        Err(e) => panic!("unexpected close after small tiny burst: {e}"),
+        Ok(None) => panic!("unexpected EOF before real frame"),
+    }
+}
+
+#[tokio::test]
+async fn idle_policy_enabled_zero_length_flood_is_fail_closed() {
+    let (reader, mut writer) = duplex(4096);
+    let mut crypto_reader = make_crypto_reader(reader);
+    let buffer_pool = Arc::new(BufferPool::new());
+    let stats = Stats::new();
+    let session_started_at = Instant::now();
+    let forensics = make_forensics(1, session_started_at);
+    let mut frame_counter = 0u64;
+    let mut idle_state = RelayClientIdleState::new(session_started_at);
+    let idle_policy = make_enabled_idle_policy();
+    let last_downstream_activity_ms = AtomicU64::new(0);
+
+    let flood_plaintext = vec![0u8; 1024];
+    let flood_encrypted = encrypt_for_reader(&flood_plaintext);
+    writer
+        .write_all(&flood_encrypted)
+        .await
+        .expect("zero-length flood bytes must be writable");
+    drop(writer);
+
+    let result = read_bounded(
+        &mut crypto_reader,
+        ProtoTag::Abridged,
+        &buffer_pool,
+        &forensics,
+        &mut frame_counter,
+        &stats,
+        &idle_policy,
+        &mut idle_state,
+        &last_downstream_activity_ms,
+        session_started_at,
+    )
+    .await;
+
+    assert!(
+        matches!(result, Err(ProxyError::Proxy(_))),
+        "idle policy enabled must fail closed for pure zero-length flood"
+    );
+}
+
+#[tokio::test]
+async fn idle_policy_enabled_alternating_tiny_real_eventually_closes() {
+    let (reader, mut writer) = duplex(8192);
+    let mut crypto_reader = make_crypto_reader(reader);
+    let buffer_pool = Arc::new(BufferPool::new());
+    let stats = Stats::new();
+    let session_started_at = Instant::now();
+    let forensics = make_forensics(2, session_started_at);
+    let mut frame_counter = 0u64;
+    let mut idle_state = RelayClientIdleState::new(session_started_at);
+    let idle_policy = make_enabled_idle_policy();
+    let last_downstream_activity_ms = AtomicU64::new(0);
+
+    let mut plaintext = Vec::with_capacity(256 * 6);
+    for idx in 0..=255u8 {
+        plaintext.push(0x00);
+        plaintext.push(0x01);
+        plaintext.extend_from_slice(&[idx, idx ^ 0x55, idx ^ 0xAA, 0x11]);
+    }
+
+    let encrypted = encrypt_for_reader(&plaintext);
+    writer
+        .write_all(&encrypted)
+        .await
+        .expect("alternating flood bytes must be writable");
+    drop(writer);
+
+    let mut saw_proxy_close = false;
+    for _ in 0..300 {
+        let result = read_bounded(
+            &mut crypto_reader,
+            ProtoTag::Abridged,
+            &buffer_pool,
+            &forensics,
+            &mut frame_counter,
+            &stats,
+            &idle_policy,
+            &mut idle_state,
+            &last_downstream_activity_ms,
+            session_started_at,
+        )
+        .await;
+
+        match result {
+            Ok(Some((_payload, _quickack))) => {}
+            Err(ProxyError::Proxy(_)) => {
+                saw_proxy_close = true;
+                break;
+            }
+            Err(ProxyError::Io(e)) => panic!("unexpected IO error before close: {e}"),
+            Ok(None) => panic!("unexpected EOF before debt-based closure"),
+            Err(other) => panic!("unexpected error before close: {other}"),
+        }
+    }
+
+    assert!(
+        saw_proxy_close,
+        "alternating tiny/real sequence must eventually fail closed"
+    );
+}
+
+#[tokio::test]
+async fn enabled_idle_policy_valid_nonzero_frame_still_passes() {
+    let (reader, mut writer) = duplex(1024);
+    let mut crypto_reader = make_crypto_reader(reader);
+    let buffer_pool = Arc::new(BufferPool::new());
+    let stats = Stats::new();
+    let session_started_at = Instant::now();
+    let forensics = make_forensics(3, session_started_at);
+    let mut frame_counter = 0u64;
+    let mut idle_state = RelayClientIdleState::new(session_started_at);
+    let idle_policy = make_enabled_idle_policy();
+    let last_downstream_activity_ms = AtomicU64::new(0);
+
+    let payload = [7u8, 8, 9, 10];
+    let mut plaintext = Vec::with_capacity(1 + payload.len());
+    plaintext.push(0x01);
+    plaintext.extend_from_slice(&payload);
+
+    let encrypted = encrypt_for_reader(&plaintext);
+    writer
+        .write_all(&encrypted)
+        .await
+        .expect("nonzero frame must be writable");
+
+    let result = read_bounded(
+        &mut crypto_reader,
+        ProtoTag::Abridged,
+        &buffer_pool,
+        &forensics,
+        &mut frame_counter,
+        &stats,
+        &idle_policy,
+        &mut idle_state,
+        &last_downstream_activity_ms,
+        session_started_at,
+    )
+    .await
+    .expect("valid frame should decode")
+    .expect("valid frame should return payload");
+
+    assert_eq!(result.0.as_ref(), &payload);
+    assert!(!result.1);
+    assert_eq!(frame_counter, 1);
+}
+
+#[tokio::test]
+async fn abridged_quickack_tiny_flood_is_fail_closed() {
+    let (reader, mut writer) = duplex(4096);
+    let mut crypto_reader = make_crypto_reader(reader);
+    let buffer_pool = Arc::new(BufferPool::new());
+    let stats = Stats::new();
+    let session_started_at = Instant::now();
+    let forensics = make_forensics(21, session_started_at);
+    let mut frame_counter = 0u64;
+    let mut idle_state = RelayClientIdleState::new(session_started_at);
+    let idle_policy = make_enabled_idle_policy();
+    let last_downstream_activity_ms = AtomicU64::new(0);
+
+    let flood_plaintext = vec![0x80u8; 256];
+    let flood_encrypted = encrypt_for_reader(&flood_plaintext);
+    writer.write_all(&flood_encrypted).await.unwrap();
+    drop(writer);
+
+    let result = read_bounded(
+        &mut crypto_reader,
+        ProtoTag::Abridged,
+        &buffer_pool,
+        &forensics,
+        &mut frame_counter,
+        &stats,
+        &idle_policy,
+        &mut idle_state,
+        &last_downstream_activity_ms,
+        session_started_at,
+    )
+    .await;
+
+    assert!(
+        matches!(result, Err(ProxyError::Proxy(_))),
+        "quickack-marked zero-length flood must fail closed"
+    );
+}
+
+#[tokio::test]
+async fn abridged_extended_zero_len_flood_is_fail_closed() {
+    let (reader, mut writer) = duplex(4096);
+    let mut crypto_reader = make_crypto_reader(reader);
+    let buffer_pool = Arc::new(BufferPool::new());
+    let stats = Stats::new();
+    let session_started_at = Instant::now();
+    let forensics = make_forensics(22, session_started_at);
+    let mut frame_counter = 0u64;
+    let mut idle_state = RelayClientIdleState::new(session_started_at);
+    let idle_policy = make_enabled_idle_policy();
+    let last_downstream_activity_ms = AtomicU64::new(0);
+
+    let mut flood_plaintext = Vec::with_capacity(4 * 256);
+    for _ in 0..256 {
+        flood_plaintext.extend_from_slice(&[0x7f, 0x00, 0x00, 0x00]);
+    }
+    let flood_encrypted = encrypt_for_reader(&flood_plaintext);
+    writer.write_all(&flood_encrypted).await.unwrap();
+    drop(writer);
+
+    let result = read_bounded(
+        &mut crypto_reader,
+        ProtoTag::Abridged,
+        &buffer_pool,
+        &forensics,
+        &mut frame_counter,
+        &stats,
+        &idle_policy,
+        &mut idle_state,
+        &last_downstream_activity_ms,
+        session_started_at,
+    )
+    .await;
+
+    assert!(
+        matches!(result, Err(ProxyError::Proxy(_))),
+        "extended zero-length abridged flood must fail closed"
+    );
+}
+
+#[tokio::test]
+async fn one_to_eight_abridged_wire_pattern_survives_without_false_positive_close() {
+    let mut plaintext = Vec::with_capacity(9 * 300);
+    for idx in 0..300usize {
+        plaintext.push(0x00);
+        for _ in 0..8 {
+            let b = idx as u8;
+            plaintext.push(0x01);
+            plaintext.extend_from_slice(&[b, b ^ 0x11, b ^ 0x22, b ^ 0x33]);
+        }
+    }
+
+    // Keep the test single-task and deterministic: make duplex capacity larger than the
+    // generated ciphertext so write_all cannot block waiting for a concurrent reader.
+    let duplex_capacity = plaintext.len().saturating_add(1024);
+    let (reader, mut writer) = duplex(duplex_capacity);
+    let mut crypto_reader = make_crypto_reader(reader);
+    let buffer_pool = Arc::new(BufferPool::new());
+    let stats = Stats::new();
+    let session_started_at = Instant::now();
+    let forensics = make_forensics(23, session_started_at);
+    let mut frame_counter = 0u64;
+    let mut idle_state = RelayClientIdleState::new(session_started_at);
+    let idle_policy = make_enabled_idle_policy();
+    let last_downstream_activity_ms = AtomicU64::new(0);
+
+    let encrypted = encrypt_for_reader(&plaintext);
+    writer.write_all(&encrypted).await.unwrap();
+    drop(writer);
+
+    let mut closed = false;
+    for _ in 0..3000 {
+        match read_bounded(
+            &mut crypto_reader,
+            ProtoTag::Abridged,
+            &buffer_pool,
+            &forensics,
+            &mut frame_counter,
+            &stats,
+            &idle_policy,
+            &mut idle_state,
+            &last_downstream_activity_ms,
+            session_started_at,
+        )
+        .await
+        {
+            Ok(Some(_)) => {}
+            Ok(None) => break,
+            Err(ProxyError::Proxy(_)) => {
+                closed = true;
+                break;
+            }
+            Err(other) => panic!("unexpected error in 1:8 wire test: {other}"),
+        }
+    }
+
+    assert!(
+        !closed,
+        "wire-level 1:8 tiny-to-real pattern should not trigger debt close"
+    );
+}
+
+#[tokio::test]
+async fn deterministic_light_fuzz_abridged_wire_behavior_matches_model() {
+    let mut seed = 0xD1CE_BAAD_2026_0322u64;
+
+    for case_idx in 0..32u64 {
+        seed ^= seed << 7;
+        seed ^= seed >> 9;
+        seed ^= seed << 8;
+
+        let events = 300 + ((seed as usize) & 0xff);
+        let mut pattern = Vec::with_capacity(events);
+        let mut local = seed;
+        for _ in 0..events {
+            local ^= local << 7;
+            local ^= local >> 9;
+            local ^= local << 8;
+            pattern.push((local & 0x03) == 0);
+        }
+
+        let mut plaintext = Vec::with_capacity(events * 6);
+        for (idx, tiny) in pattern.iter().copied().enumerate() {
+            if tiny {
+                plaintext.push(0x00);
+            } else {
+                let b = (idx as u8) ^ (case_idx as u8);
+                plaintext.push(0x01);
+                plaintext.extend_from_slice(&[b, b ^ 0x1F, b ^ 0x7A, b ^ 0xC3]);
+            }
+        }
+
+        let (reader, mut writer) = duplex(16 * 1024);
+        let mut crypto_reader = make_crypto_reader(reader);
+        let buffer_pool = Arc::new(BufferPool::new());
+        let stats = Stats::new();
+        let session_started_at = Instant::now();
+        let forensics = make_forensics(500 + case_idx, session_started_at);
+        let mut frame_counter = 0u64;
+        let mut idle_state = RelayClientIdleState::new(session_started_at);
+        let idle_policy = make_enabled_idle_policy();
+        let last_downstream_activity_ms = AtomicU64::new(0);
+
+        writer
+            .write_all(&encrypt_for_reader(&plaintext))
+            .await
+            .unwrap();
+        drop(writer);
+
+        let (expected_close, _, _) = simulate_tiny_debt_pattern(&pattern, pattern.len());
+        let mut observed_close = false;
+
+        for _ in 0..(events + 8) {
+            match read_bounded(
+                &mut crypto_reader,
+                ProtoTag::Abridged,
+                &buffer_pool,
+                &forensics,
+                &mut frame_counter,
+                &stats,
+                &idle_policy,
+                &mut idle_state,
+                &last_downstream_activity_ms,
+                session_started_at,
+            )
+            .await
+            {
+                Ok(Some(_)) => {}
+                Ok(None) => break,
+                Err(ProxyError::Proxy(_)) => {
+                    observed_close = true;
+                    break;
+                }
+                Err(other) => panic!("unexpected fuzz error: {other}"),
+            }
+        }
+
+        assert_eq!(
+            observed_close,
+            expected_close.is_some(),
+            "wire parser behavior must match debt model for case {case_idx}"
+        );
+    }
+}

src/proxy/tests/middle_relay_zero_length_frame_security_tests.rs

@@ -0,0 +1,121 @@
+use super::*;
+use crate::crypto::AesCtr;
+use crate::stats::Stats;
+use crate::stream::{BufferPool, CryptoReader};
+use std::sync::atomic::AtomicU64;
+use std::sync::Arc;
+use tokio::io::{AsyncRead, AsyncWriteExt, duplex};
+use std::time::Instant;
+
+fn make_crypto_reader<T>(reader: T) -> CryptoReader<T>
+where
+    T: AsyncRead + Unpin + Send + 'static,
+{
+    let key = [0u8; 32];
+    let iv = 0u128;
+    CryptoReader::new(reader, AesCtr::new(&key, iv))
+}
+
+fn encrypt_for_reader(plaintext: &[u8]) -> Vec<u8> {
+    let key = [0u8; 32];
+    let iv = 0u128;
+    let mut cipher = AesCtr::new(&key, iv);
+    cipher.encrypt(plaintext)
+}
+
+fn make_forensics(conn_id: u64, started_at: Instant) -> RelayForensicsState {
+    RelayForensicsState {
+        trace_id: 0xB000_0000 + conn_id,
+        conn_id,
+        user: format!("zero-len-test-user-{conn_id}"),
+        peer: "127.0.0.1:50000".parse().expect("peer parse must succeed"),
+        peer_hash: hash_ip("127.0.0.1".parse().expect("ip parse must succeed")),
+        started_at,
+        bytes_c2me: 0,
+        bytes_me2c: Arc::new(AtomicU64::new(0)),
+        desync_all_full: false,
+    }
+}
+
+#[tokio::test]
+async fn adversarial_legacy_zero_length_flood_is_fail_closed() {
+    let (reader, mut writer) = duplex(1024);
+    let mut crypto_reader = make_crypto_reader(reader);
+    let buffer_pool = Arc::new(BufferPool::new());
+    let stats = Stats::new();
+    let session_started_at = Instant::now();
+    let forensics = make_forensics(1, session_started_at);
+    let mut frame_counter = 0u64;
+
+    let flood_plaintext = vec![0u8; 128];
+    let flood_encrypted = encrypt_for_reader(&flood_plaintext);
+    writer
+        .write_all(&flood_encrypted)
+        .await
+        .expect("zero-length flood bytes must be writable");
+    drop(writer);
+
+    let result = read_client_payload_legacy(
+        &mut crypto_reader,
+        ProtoTag::Abridged,
+        1024,
+        Duration::from_millis(30),
+        &buffer_pool,
+        &forensics,
+        &mut frame_counter,
+        &stats,
+    )
+    .await;
+
+    match result {
+        Err(ProxyError::Proxy(msg)) => {
+            assert!(
+                msg.contains("Excessive zero-length"),
+                "legacy mode must close flood with explicit zero-length reason, got: {msg}"
+            );
+        }
+        Ok(None) => panic!("legacy zero-length flood must not be accepted as EOF"),
+        Ok(Some(_)) => panic!("legacy zero-length flood must not produce a data frame"),
+        Err(err) => panic!("legacy zero-length flood must be a Proxy error, got: {err}"),
+    }
+}
+
+#[tokio::test]
+async fn business_abridged_nonzero_frame_still_passes() {
+    let (reader, mut writer) = duplex(1024);
+    let mut crypto_reader = make_crypto_reader(reader);
+    let buffer_pool = Arc::new(BufferPool::new());
+    let stats = Stats::new();
+    let session_started_at = Instant::now();
+    let forensics = make_forensics(2, session_started_at);
+    let mut frame_counter = 0u64;
+
+    let payload = [1u8, 2, 3, 4];
+    let mut plaintext = Vec::with_capacity(1 + payload.len());
+    plaintext.push(0x01);
+    plaintext.extend_from_slice(&payload);
+
+    let encrypted = encrypt_for_reader(&plaintext);
+    writer
+        .write_all(&encrypted)
+        .await
+        .expect("nonzero abridged frame must be writable");
+
+    let result = read_client_payload_legacy(
+        &mut crypto_reader,
+        ProtoTag::Abridged,
+        1024,
+        Duration::from_millis(30),
+        &buffer_pool,
+        &forensics,
+        &mut frame_counter,
+        &stats,
+    )
+    .await
+    .expect("valid abridged frame should decode")
+    .expect("valid abridged frame should return payload");
+
+    assert_eq!(result.0.as_ref(), &payload);
+    assert!(!result.1, "quickack flag must remain false");
+    assert_eq!(frame_counter, 1);
+}

src/proxy/tests/relay_quota_extended_attack_surface_security_tests.rs

@@ -0,0 +1,332 @@
+use super::relay_bidirectional;
+use crate::error::ProxyError;
+use crate::stats::Stats;
+use crate::stream::BufferPool;
+use rand::rngs::StdRng;
+use rand::{RngExt, SeedableRng};
+use std::sync::Arc;
+use tokio::io::{duplex, AsyncReadExt, AsyncWriteExt};
+use tokio::time::{Duration, timeout};
+
+async fn read_available<R: tokio::io::AsyncRead + Unpin>(reader: &mut R, budget: Duration) -> usize {
+    let start = tokio::time::Instant::now();
+    let mut total = 0usize;
+    let mut buf = [0u8; 128];
+
+    loop {
+        let elapsed = start.elapsed();
+        if elapsed >= budget {
+            break;
+        }
+        let remaining = budget.saturating_sub(elapsed);
+        match timeout(remaining, reader.read(&mut buf)).await {
+            Ok(Ok(0)) => break,
+            Ok(Ok(n)) => total = total.saturating_add(n),
+            Ok(Err(_)) | Err(_) => break,
+        }
+    }
+
+    total
+}
+
+#[tokio::test]
+async fn positive_quota_path_forwards_both_directions_within_limit() {
+    let stats = Arc::new(Stats::new());
+    let user = "quota-extended-positive-user";
+
+    let (mut client_peer, relay_client) = duplex(2048);
+    let (relay_server, mut server_peer) = duplex(2048);
+    let (client_reader, client_writer) = tokio::io::split(relay_client);
+    let (server_reader, server_writer) = tokio::io::split(relay_server);
+
+    let relay = tokio::spawn(relay_bidirectional(
+        client_reader,
+        client_writer,
+        server_reader,
+        server_writer,
+        256,
+        256,
+        user,
+        Arc::clone(&stats),
+        Some(16),
+        Arc::new(BufferPool::new()),
+    ));
+
+    client_peer.write_all(&[0xAA, 0xBB, 0xCC, 0xDD]).await.unwrap();
+    server_peer.read_exact(&mut [0u8; 4]).await.unwrap();
+
+    server_peer.write_all(&[0x11, 0x22, 0x33, 0x44]).await.unwrap();
+    client_peer.read_exact(&mut [0u8; 4]).await.unwrap();
+
+    drop(client_peer);
+    drop(server_peer);
+
+    let relay_result = timeout(Duration::from_secs(2), relay).await.unwrap().unwrap();
+    assert!(relay_result.is_ok());
+    assert!(stats.get_user_total_octets(user) <= 16);
+}
+
+#[tokio::test]
+async fn negative_preloaded_quota_forbids_any_forwarding() {
+    let stats = Arc::new(Stats::new());
+    let user = "quota-extended-negative-user";
+    stats.add_user_octets_from(user, 8);
+
+    let (mut client_peer, relay_client) = duplex(1024);
+    let (relay_server, mut server_peer) = duplex(1024);
+    let (client_reader, client_writer) = tokio::io::split(relay_client);
+    let (server_reader, server_writer) = tokio::io::split(relay_server);
+
+    let relay = tokio::spawn(relay_bidirectional(
+        client_reader,
+        client_writer,
+        server_reader,
+        server_writer,
+        128,
+        128,
+        user,
+        Arc::clone(&stats),
+        Some(8),
+        Arc::new(BufferPool::new()),
+    ));
+
+    client_peer.write_all(&[0xAA]).await.unwrap();
+    server_peer.write_all(&[0xBB]).await.unwrap();
+
+    assert_eq!(read_available(&mut server_peer, Duration::from_millis(120)).await, 0);
+    assert_eq!(read_available(&mut client_peer, Duration::from_millis(120)).await, 0);
+
+    let relay_result = timeout(Duration::from_secs(2), relay).await.unwrap().unwrap();
+    assert!(matches!(relay_result, Err(ProxyError::DataQuotaExceeded { .. })));
+    assert!(stats.get_user_total_octets(user) <= 8);
+}
+
+#[tokio::test]
+async fn edge_quota_one_ensures_at_most_one_byte_across_directions() {
+    let stats = Arc::new(Stats::new());
+    let user = "quota-extended-edge-user";
+
+    let (mut client_peer, relay_client) = duplex(1024);
+    let (relay_server, mut server_peer) = duplex(1024);
+    let (client_reader, client_writer) = tokio::io::split(relay_client);
+    let (server_reader, server_writer) = tokio::io::split(relay_server);
+
+    let relay = tokio::spawn(relay_bidirectional(
+        client_reader,
+        client_writer,
+        server_reader,
+        server_writer,
+        128,
+        128,
+        user,
+        Arc::clone(&stats),
+        Some(1),
+        Arc::new(BufferPool::new()),
+    ));
+
+    let _ = tokio::join!(
+        client_peer.write_all(&[0xFE]),
+        server_peer.write_all(&[0xEF]),
+    );
+
+    let mut buf = [0u8; 1];
+    let delivered_s2c = timeout(Duration::from_millis(120), client_peer.read(&mut buf)).await.unwrap().unwrap_or(0);
+    let delivered_c2s = timeout(Duration::from_millis(120), server_peer.read(&mut buf)).await.unwrap().unwrap_or(0);
+
+    assert!(delivered_s2c + delivered_c2s <= 1);
+
+    let relay_result = timeout(Duration::from_secs(2), relay).await.unwrap().unwrap();
+    assert!(matches!(relay_result, Err(ProxyError::DataQuotaExceeded { .. })));
+}
+
+#[tokio::test]
+async fn adversarial_blackhat_alternating_jitter_does_not_overshoot_quota() {
+    let stats = Arc::new(Stats::new());
+    let user = "quota-extended-blackhat-user";
+    let quota = 24u64;
+
+    let (mut client_peer, relay_client) = duplex(4096);
+    let (relay_server, mut server_peer) = duplex(4096);
+    let (client_reader, client_writer) = tokio::io::split(relay_client);
+    let (server_reader, server_writer) = tokio::io::split(relay_server);
+
+    let relay = tokio::spawn(relay_bidirectional(
+        client_reader,
+        client_writer,
+        server_reader,
+        server_writer,
+        256,
+        256,
+        user,
+        Arc::clone(&stats),
+        Some(quota),
+        Arc::new(BufferPool::new()),
+    ));
+
+    let mut total_forwarded = 0usize;
+
+    for i in 0..256usize {
+        if relay.is_finished() {
+            break;
+        }
+        if (i & 1) == 0 {
+            let _ = client_peer.write_all(&[(i as u8) ^ 0x57]).await;
+            let mut one = [0u8; 1];
+            if let Ok(Ok(n)) = timeout(Duration::from_millis(6), server_peer.read(&mut one)).await {
+                total_forwarded += n;
+            }
+        } else {
+            let _ = server_peer.write_all(&[(i as u8) ^ 0xA8]).await;
+            let mut one = [0u8; 1];
+            if let Ok(Ok(n)) = timeout(Duration::from_millis(6), client_peer.read(&mut one)).await {
+                total_forwarded += n;
+            }
+        }
+
+        tokio::time::sleep(Duration::from_millis(((i % 3) + 1) as u64)).await;
+    }
+
+    let relay_result = timeout(Duration::from_secs(3), relay).await.unwrap().unwrap();
+    assert!(matches!(relay_result, Err(ProxyError::DataQuotaExceeded { .. })));
+    assert!(total_forwarded <= quota as usize);
+    assert!(stats.get_user_total_octets(user) <= quota);
+}
+
+#[tokio::test]
+async fn light_fuzz_random_quota_schedule_preserves_quota_invariants() {
+    let mut rng = StdRng::seed_from_u64(0xBEEF_C0DE);
+
+    for case in 0..32u64 {
+        let stats = Arc::new(Stats::new());
+        let user = format!("quota-extended-fuzz-{case}");
+        let quota = rng.random_range(1u64..=35u64);
+
+        let (mut client_peer, relay_client) = duplex(4096);
+        let (relay_server, mut server_peer) = duplex(4096);
+        let (client_reader, client_writer) = tokio::io::split(relay_client);
+        let (server_reader, server_writer) = tokio::io::split(relay_server);
+
+        let relay_user = user.clone();
+        let relay_stats = Arc::clone(&stats);
+        let relay = tokio::spawn(async move {
+            relay_bidirectional(
+                client_reader,
+                client_writer,
+                server_reader,
+                server_writer,
+                256,
+                256,
+                &relay_user,
+                Arc::clone(&relay_stats),
+                Some(quota),
+                Arc::new(BufferPool::new()),
+            )
+            .await
+        });
+
+        let mut total_forwarded = 0usize;
+
+        for _ in 0..96usize {
+            if relay.is_finished() {
+                break;
+            }
+
+            if rng.random::<bool>() {
+                let _ = client_peer.write_all(&[rng.random::<u8>()]).await;
+                let mut one = [0u8; 1];
+                if let Ok(Ok(n)) = timeout(Duration::from_millis(4), server_peer.read(&mut one)).await {
+                    total_forwarded += n;
+                }
+            } else {
+                let _ = server_peer.write_all(&[rng.random::<u8>()]).await;
+                let mut one = [0u8; 1];
+                if let Ok(Ok(n)) = timeout(Duration::from_millis(4), client_peer.read(&mut one)).await {
+                    total_forwarded += n;
+                }
+            }
+        }
+
+        drop(client_peer);
+        drop(server_peer);
+
+        let relay_result = timeout(Duration::from_secs(2), relay).await.unwrap().unwrap();
+        assert!(relay_result.is_ok() || matches!(relay_result, Err(ProxyError::DataQuotaExceeded { .. })));
+        assert!(total_forwarded <= quota as usize);
+        assert!(stats.get_user_total_octets(&user) <= quota);
+    }
+}
+
+#[tokio::test(flavor = "multi_thread", worker_threads = 4)]
+async fn stress_parallel_relays_for_one_user_obey_global_quota() {
+    let stats = Arc::new(Stats::new());
+    let user = "quota-extended-stress-user".to_string();
+    let quota = 64u64;
+
+    let mut tasks = Vec::new();
+
+    for worker in 0..4u8 {
+        let stats = Arc::clone(&stats);
+        let user = user.clone();
+
+        tasks.push(tokio::spawn(async move {
+            let (mut client_peer, relay_client) = duplex(2048);
+            let (relay_server, mut server_peer) = duplex(2048);
+            let (client_reader, client_writer) = tokio::io::split(relay_client);
+            let (server_reader, server_writer) = tokio::io::split(relay_server);
+
+            let relay_user = user.clone();
+            let relay_stats = Arc::clone(&stats);
+            let relay = tokio::spawn(async move {
+                relay_bidirectional(
+                    client_reader,
+                    client_writer,
+                    server_reader,
+                    server_writer,
+                    128,
+                    128,
+                    &relay_user,
+                    Arc::clone(&relay_stats),
+                    Some(quota),
+                    Arc::new(BufferPool::new()),
+                )
+                .await
+            });
+
+            let mut total = 0usize;
+            for step in 0..64u8 {
+                if relay.is_finished() {
+                    break;
+                }
+                if (step as usize + worker as usize) % 2 == 0 {
+                    let _ = client_peer.write_all(&[(step ^ 0x5A)]).await;
+                    let mut one = [0u8; 1];
+                    if let Ok(Ok(n)) = timeout(Duration::from_millis(6), server_peer.read(&mut one)).await {
+                        total += n;
+                    }
+                } else {
+                    let _ = server_peer.write_all(&[(step ^ 0xA5)]).await;
+                    let mut one = [0u8; 1];
+                    if let Ok(Ok(n)) = timeout(Duration::from_millis(6), client_peer.read(&mut one)).await {
+                        total += n;
+                    }
+                }
+                tokio::time::sleep(Duration::from_millis(1)).await;
+            }
+
+            drop(client_peer);
+            drop(server_peer);
+
+            let relay_result = timeout(Duration::from_secs(2), relay).await.unwrap().unwrap();
+            assert!(relay_result.is_ok() || matches!(relay_result, Err(ProxyError::DataQuotaExceeded { .. })));
+            total
+        }));
+    }
+
+    let mut delivered = 0usize;
+    for task in tasks {
+        delivered += task.await.unwrap();
+    }
+
+    assert!(stats.get_user_total_octets(&user) <= quota);
+    assert!(delivered <= quota as usize);
+}

src/proxy/tests/relay_quota_lock_pressure_adversarial_tests.rs

@@ -1,438 +0,0 @@
-use super::*;
-use crate::error::ProxyError;
-use crate::stats::Stats;
-use crate::stream::BufferPool;
-use dashmap::DashMap;
-use std::sync::Arc;
-use std::sync::atomic::AtomicBool;
-use std::time::Duration;
-use tokio::io::{AsyncReadExt, AsyncWriteExt, duplex};
-use tokio::sync::Barrier;
-use tokio::time::Instant;
-
-#[test]
-fn quota_lock_same_user_returns_same_arc_instance() {
-    let _guard = super::quota_user_lock_test_scope();
-    let map = QUOTA_USER_LOCKS.get_or_init(DashMap::new);
-    map.clear();
-
-    let a = quota_user_lock("quota-lock-same-user");
-    let b = quota_user_lock("quota-lock-same-user");
-    assert!(Arc::ptr_eq(&a, &b));
-}
-
-#[test]
-fn quota_lock_parallel_same_user_reuses_single_lock() {
-    let _guard = super::quota_user_lock_test_scope();
-    let map = QUOTA_USER_LOCKS.get_or_init(DashMap::new);
-    map.clear();
-
-    let user = "quota-lock-parallel-same";
-    let mut handles = Vec::new();
-
-    for _ in 0..64 {
-        handles.push(std::thread::spawn(move || quota_user_lock(user)));
-    }
-
-    let first = handles
-        .remove(0)
-        .join()
-        .expect("thread must return lock handle");
-
-    for handle in handles {
-        let got = handle.join().expect("thread must return lock handle");
-        assert!(Arc::ptr_eq(&first, &got));
-    }
-}
-
-#[test]
-fn quota_lock_unique_users_materialize_distinct_entries() {
-    let _guard = super::quota_user_lock_test_scope();
-    let map = QUOTA_USER_LOCKS.get_or_init(DashMap::new);
-
-    map.clear();
-
-    let base = format!("quota-lock-distinct-{}", std::process::id());
-    let users: Vec<String> = (0..(QUOTA_USER_LOCKS_MAX / 2))
-        .map(|idx| format!("{base}-{idx}"))
-        .collect();
-
-    for user in &users {
-        let _ = quota_user_lock(user);
-    }
-
-    for user in &users {
-        assert!(
-            map.get(user).is_some(),
-            "lock cache must contain entry for {user}"
-        );
-    }
-}
-
-#[test]
-fn quota_lock_unique_churn_stress_keeps_all_inserted_keys_addressable() {
-    let _guard = super::quota_user_lock_test_scope();
-    let map = QUOTA_USER_LOCKS.get_or_init(DashMap::new);
-
-    map.clear();
-
-    let base = format!("quota-lock-churn-{}", std::process::id());
-    for idx in 0..(QUOTA_USER_LOCKS_MAX + 256) {
-        let _ = quota_user_lock(&format!("{base}-{idx}"));
-    }
-
-    assert!(
-        map.len() <= QUOTA_USER_LOCKS_MAX,
-        "quota lock cache must stay bounded under unique-user churn"
-    );
-}
-
-#[test]
-fn quota_lock_saturation_returns_stable_overflow_lock_without_cache_growth() {
-    let _guard = super::quota_user_lock_test_scope();
-    let map = QUOTA_USER_LOCKS.get_or_init(DashMap::new);
-    map.clear();
-
-    let prefix = format!("quota-held-{}", std::process::id());
-    let mut retained = Vec::with_capacity(QUOTA_USER_LOCKS_MAX);
-    for idx in 0..QUOTA_USER_LOCKS_MAX {
-        retained.push(quota_user_lock(&format!("{prefix}-{idx}")));
-    }
-
-    assert_eq!(
-        map.len(),
-        QUOTA_USER_LOCKS_MAX,
-        "cache must be saturated for overflow check"
-    );
-
-    let overflow_user = format!("quota-overflow-{}", std::process::id());
-    let overflow_a = quota_user_lock(&overflow_user);
-    let overflow_b = quota_user_lock(&overflow_user);
-
-    assert_eq!(
-        map.len(),
-        QUOTA_USER_LOCKS_MAX,
-        "overflow path must not grow lock cache"
-    );
-    assert!(
-        map.get(&overflow_user).is_none(),
-        "overflow user lock must stay outside bounded cache under saturation"
-    );
-    assert!(
-        Arc::ptr_eq(&overflow_a, &overflow_b),
-        "overflow user must receive stable striped overflow lock while saturated"
-    );
-
-    drop(retained);
-}
-
-#[test]
-fn quota_lock_reclaims_unreferenced_entries_before_ephemeral_fallback() {
-    let _guard = super::quota_user_lock_test_scope();
-    let map = QUOTA_USER_LOCKS.get_or_init(DashMap::new);
-    map.clear();
-
-    // Saturate with retained strong references first so parallel tests cannot
-    // reclaim our fixture entries before we validate the reclaim path.
-    let prefix = format!("quota-reclaim-drop-{}", std::process::id());
-    let mut retained = Vec::with_capacity(QUOTA_USER_LOCKS_MAX);
-    for idx in 0..QUOTA_USER_LOCKS_MAX {
-        retained.push(quota_user_lock(&format!("{prefix}-{idx}")));
-    }
-
-    drop(retained);
-
-    let overflow_user = format!("quota-reclaim-overflow-{}", std::process::id());
-    let overflow = quota_user_lock(&overflow_user);
-
-    assert!(
-        map.get(&overflow_user).is_some(),
-        "after reclaiming stale entries, overflow user should become cacheable"
-    );
-    assert!(
-        Arc::strong_count(&overflow) >= 2,
-        "cacheable overflow lock should be held by both map and caller"
-    );
-}
-
-#[test]
-fn quota_lock_saturated_same_user_must_not_return_distinct_locks() {
-    let _guard = super::quota_user_lock_test_scope();
-    let map = QUOTA_USER_LOCKS.get_or_init(DashMap::new);
-    map.clear();
-
-    let mut retained = Vec::with_capacity(QUOTA_USER_LOCKS_MAX);
-    for idx in 0..QUOTA_USER_LOCKS_MAX {
-        retained.push(quota_user_lock(&format!(
-            "quota-saturated-held-{}-{idx}",
-            std::process::id()
-        )));
-    }
-
-    let overflow_user = format!("quota-saturated-same-user-{}", std::process::id());
-    let a = quota_user_lock(&overflow_user);
-    let b = quota_user_lock(&overflow_user);
-
-    assert!(
-        Arc::ptr_eq(&a, &b),
-        "same user must not receive distinct locks under saturation because that enables quota race bypass"
-    );
-
-    drop(retained);
-}
-
-#[tokio::test(flavor = "multi_thread", worker_threads = 4)]
-async fn quota_lock_saturation_concurrent_same_user_never_overshoots_quota() {
-    let _guard = super::quota_user_lock_test_scope();
-    let map = QUOTA_USER_LOCKS.get_or_init(DashMap::new);
-    map.clear();
-
-    let mut retained = Vec::with_capacity(QUOTA_USER_LOCKS_MAX);
-    for idx in 0..QUOTA_USER_LOCKS_MAX {
-        retained.push(quota_user_lock(&format!(
-            "quota-saturated-race-held-{}-{idx}",
-            std::process::id()
-        )));
-    }
-
-    let stats = Arc::new(Stats::new());
-    let user = format!("quota-saturated-race-user-{}", std::process::id());
-    let gate = Arc::new(Barrier::new(2));
-
-    let worker = |label: u8, stats: Arc<Stats>, user: String, gate: Arc<Barrier>| {
-        tokio::spawn(async move {
-            let counters = Arc::new(SharedCounters::new());
-            let quota_exceeded = Arc::new(AtomicBool::new(false));
-            let mut io = StatsIo::new(
-                tokio::io::sink(),
-                counters,
-                Arc::clone(&stats),
-                user,
-                Some(1),
-                quota_exceeded,
-                Instant::now(),
-            );
-            gate.wait().await;
-            io.write_all(&[label]).await
-        })
-    };
-
-    let one = worker(0x11, Arc::clone(&stats), user.clone(), Arc::clone(&gate));
-    let two = worker(0x22, Arc::clone(&stats), user.clone(), Arc::clone(&gate));
-
-    let _ = tokio::time::timeout(Duration::from_secs(2), async {
-        let _ = one.await.expect("task one must not panic");
-        let _ = two.await.expect("task two must not panic");
-    })
-    .await
-    .expect("quota race workers must complete");
-
-    assert!(
-        stats.get_user_total_octets(&user) <= 1,
-        "saturated lock path must never overshoot quota for same user"
-    );
-
-    drop(retained);
-}
-
-#[tokio::test(flavor = "multi_thread", worker_threads = 4)]
-async fn quota_lock_saturation_stress_same_user_never_overshoots_quota() {
-    let _guard = super::quota_user_lock_test_scope();
-    let map = QUOTA_USER_LOCKS.get_or_init(DashMap::new);
-    map.clear();
-
-    let mut retained = Vec::with_capacity(QUOTA_USER_LOCKS_MAX);
-    for idx in 0..QUOTA_USER_LOCKS_MAX {
-        retained.push(quota_user_lock(&format!(
-            "quota-saturated-stress-held-{}-{idx}",
-            std::process::id()
-        )));
-    }
-
-    for round in 0..128u32 {
-        let stats = Arc::new(Stats::new());
-        let user = format!("quota-saturated-stress-user-{}-{round}", std::process::id());
-        let gate = Arc::new(Barrier::new(2));
-
-        let one = {
-            let stats = Arc::clone(&stats);
-            let user = user.clone();
-            let gate = Arc::clone(&gate);
-            tokio::spawn(async move {
-                let counters = Arc::new(SharedCounters::new());
-                let quota_exceeded = Arc::new(AtomicBool::new(false));
-                let mut io = StatsIo::new(
-                    tokio::io::sink(),
-                    counters,
-                    Arc::clone(&stats),
-                    user,
-                    Some(1),
-                    quota_exceeded,
-                    Instant::now(),
-                );
-                gate.wait().await;
-                io.write_all(&[0x31]).await
-            })
-        };
-
-        let two = {
-            let stats = Arc::clone(&stats);
-            let user = user.clone();
-            let gate = Arc::clone(&gate);
-            tokio::spawn(async move {
-                let counters = Arc::new(SharedCounters::new());
-                let quota_exceeded = Arc::new(AtomicBool::new(false));
-                let mut io = StatsIo::new(
-                    tokio::io::sink(),
-                    counters,
-                    Arc::clone(&stats),
-                    user,
-                    Some(1),
-                    quota_exceeded,
-                    Instant::now(),
-                );
-                gate.wait().await;
-                io.write_all(&[0x32]).await
-            })
-        };
-
-        let _ = one.await.expect("stress task one must not panic");
-        let _ = two.await.expect("stress task two must not panic");
-
-        assert!(
-            stats.get_user_total_octets(&user) <= 1,
-            "round {round}: saturated path must not overshoot quota"
-        );
-    }
-
-    drop(retained);
-}
-
-#[test]
-fn quota_error_classifier_accepts_internal_quota_sentinel_only() {
-    let err = quota_io_error();
-    assert!(is_quota_io_error(&err));
-}
-
-#[test]
-fn quota_error_classifier_rejects_plain_permission_denied() {
-    let err = std::io::Error::new(std::io::ErrorKind::PermissionDenied, "permission denied");
-    assert!(!is_quota_io_error(&err));
-}
-
-#[test]
-fn quota_lock_test_scope_recovers_after_guard_poison() {
-    let poison_result = std::thread::spawn(|| {
-        let _guard = super::quota_user_lock_test_scope();
-        panic!("intentional test-only guard poison");
-    })
-    .join();
-    assert!(poison_result.is_err(), "poison setup thread must panic");
-
-    let _guard = super::quota_user_lock_test_scope();
-    let map = QUOTA_USER_LOCKS.get_or_init(DashMap::new);
-    map.clear();
-
-    let a = quota_user_lock("quota-lock-poison-recovery-user");
-    let b = quota_user_lock("quota-lock-poison-recovery-user");
-    assert!(Arc::ptr_eq(&a, &b));
-}
-
-#[tokio::test]
-async fn quota_lock_integration_zero_quota_cuts_off_without_forwarding() {
-    let stats = Arc::new(Stats::new());
-    let user = "quota-zero-user";
-
-    let (mut client_peer, relay_client) = duplex(2048);
-    let (relay_server, mut server_peer) = duplex(2048);
-    let (client_reader, client_writer) = tokio::io::split(relay_client);
-    let (server_reader, server_writer) = tokio::io::split(relay_server);
-
-    let relay = tokio::spawn(relay_bidirectional(
-        client_reader,
-        client_writer,
-        server_reader,
-        server_writer,
-        512,
-        512,
-        user,
-        Arc::clone(&stats),
-        Some(0),
-        Arc::new(BufferPool::new()),
-    ));
-
-    client_peer
-        .write_all(b"x")
-        .await
-        .expect("client write must succeed");
-
-    let mut probe = [0u8; 1];
-    let forwarded =
-        tokio::time::timeout(Duration::from_millis(80), server_peer.read(&mut probe)).await;
-    if let Ok(Ok(n)) = forwarded {
-        assert_eq!(n, 0, "zero quota path must not forward payload bytes");
-    }
-
-    let result = tokio::time::timeout(Duration::from_secs(2), relay)
-        .await
-        .expect("relay must terminate under zero quota")
-        .expect("relay task must not panic");
-    assert!(matches!(result, Err(ProxyError::DataQuotaExceeded { .. })));
-}
-
-#[tokio::test]
-async fn quota_lock_integration_no_quota_relays_both_directions_under_burst() {
-    let stats = Arc::new(Stats::new());
-
-    let (mut client_peer, relay_client) = duplex(8192);
-    let (relay_server, mut server_peer) = duplex(8192);
-    let (client_reader, client_writer) = tokio::io::split(relay_client);
-    let (server_reader, server_writer) = tokio::io::split(relay_server);
-
-    let relay = tokio::spawn(relay_bidirectional(
-        client_reader,
-        client_writer,
-        server_reader,
-        server_writer,
-        1024,
-        1024,
-        "quota-none-burst-user",
-        Arc::clone(&stats),
-        None,
-        Arc::new(BufferPool::new()),
-    ));
-
-    let c2s = vec![0xA5; 2048];
-    let s2c = vec![0x5A; 1536];
-
-    client_peer
-        .write_all(&c2s)
-        .await
-        .expect("client burst write must succeed");
-    let mut got_c2s = vec![0u8; c2s.len()];
-    server_peer
-        .read_exact(&mut got_c2s)
-        .await
-        .expect("server must receive c2s burst");
-    assert_eq!(got_c2s, c2s);
-
-    server_peer
-        .write_all(&s2c)
-        .await
-        .expect("server burst write must succeed");
-    let mut got_s2c = vec![0u8; s2c.len()];
-    client_peer
-        .read_exact(&mut got_s2c)
-        .await
-        .expect("client must receive s2c burst");
-    assert_eq!(got_s2c, s2c);
-
-    drop(client_peer);
-    drop(server_peer);
-
-    let done = tokio::time::timeout(Duration::from_secs(2), relay)
-        .await
-        .expect("relay must terminate after peers close")
-        .expect("relay task must not panic");
-    assert!(done.is_ok());
-}

src/proxy/tests/relay_quota_wake_liveness_regression_tests.rs

@@ -1,294 +0,0 @@
-use super::*;
-use crate::stats::Stats;
-use dashmap::DashMap;
-use std::sync::Arc;
-use std::sync::atomic::AtomicBool;
-use tokio::io::{AsyncReadExt, AsyncWriteExt};
-use tokio::sync::Barrier;
-use tokio::time::{Duration, timeout};
-
-fn saturate_lock_cache() -> Vec<Arc<std::sync::Mutex<()>>> {
-    let map = QUOTA_USER_LOCKS.get_or_init(DashMap::new);
-    map.clear();
-
-    let mut retained = Vec::with_capacity(QUOTA_USER_LOCKS_MAX);
-    for idx in 0..QUOTA_USER_LOCKS_MAX {
-        retained.push(quota_user_lock(&format!("quota-liveness-saturated-{idx}")));
-    }
-    retained
-}
-
-fn quota_test_guard() -> impl Drop {
-    super::quota_user_lock_test_scope()
-}
-
-#[tokio::test]
-async fn positive_writer_progresses_after_contention_release_without_external_wake() {
-    let _guard = quota_test_guard();
-
-    let _retained = saturate_lock_cache();
-    let user = "quota-liveness-writer-positive";
-    let stats = Arc::new(Stats::new());
-
-    let lock = quota_user_lock(user);
-    let held_guard = lock
-        .try_lock()
-        .expect("test must hold user quota lock before write");
-
-    let counters = Arc::new(SharedCounters::new());
-    let quota_exceeded = Arc::new(AtomicBool::new(false));
-    let mut io = StatsIo::new(
-        tokio::io::sink(),
-        counters,
-        Arc::clone(&stats),
-        user.to_string(),
-        Some(1024),
-        quota_exceeded,
-        tokio::time::Instant::now(),
-    );
-
-    let writer = tokio::spawn(async move { io.write_all(&[0x11]).await });
-
-    // Let the initial deferred wake fire while contention is still active.
-    tokio::time::sleep(Duration::from_millis(4)).await;
-
-    drop(held_guard);
-
-    let completed = timeout(Duration::from_millis(250), writer)
-        .await
-        .expect("writer must be re-polled and complete after lock release")
-        .expect("writer task must not panic");
-    assert!(completed.is_ok(), "writer must complete after lock release");
-}
-
-#[tokio::test]
-async fn edge_reader_progresses_after_contention_release_without_external_wake() {
-    let _guard = quota_test_guard();
-
-    let _retained = saturate_lock_cache();
-    let user = "quota-liveness-reader-edge";
-    let stats = Arc::new(Stats::new());
-
-    let lock = quota_user_lock(user);
-    let held_guard = lock
-        .try_lock()
-        .expect("test must hold user quota lock before read");
-
-    let counters = Arc::new(SharedCounters::new());
-    let quota_exceeded = Arc::new(AtomicBool::new(false));
-    let mut io = StatsIo::new(
-        tokio::io::empty(),
-        counters,
-        Arc::clone(&stats),
-        user.to_string(),
-        Some(1024),
-        quota_exceeded,
-        tokio::time::Instant::now(),
-    );
-
-    let reader = tokio::spawn(async move {
-        let mut one = [0u8; 1];
-        io.read(&mut one).await
-    });
-
-    tokio::time::sleep(Duration::from_millis(4)).await;
-    drop(held_guard);
-
-    let completed = timeout(Duration::from_millis(250), reader)
-        .await
-        .expect("reader must be re-polled and complete after lock release")
-        .expect("reader task must not panic");
-    assert!(completed.is_ok(), "reader must complete after lock release");
-}
-
-#[tokio::test]
-async fn adversarial_early_deferred_wake_consumption_does_not_deadlock_writer() {
-    let _guard = quota_test_guard();
-
-    let _retained = saturate_lock_cache();
-    let user = "quota-liveness-adversarial";
-    let stats = Arc::new(Stats::new());
-
-    let lock = quota_user_lock(user);
-    let held_guard = lock
-        .try_lock()
-        .expect("test must hold user quota lock before adversarial write");
-
-    let counters = Arc::new(SharedCounters::new());
-    let quota_exceeded = Arc::new(AtomicBool::new(false));
-    let mut io = StatsIo::new(
-        tokio::io::sink(),
-        counters,
-        Arc::clone(&stats),
-        user.to_string(),
-        Some(1024),
-        quota_exceeded,
-        tokio::time::Instant::now(),
-    );
-
-    let writer = tokio::spawn(async move { io.write_all(&[0x22]).await });
-
-    // Force multiple scheduler rounds while lock remains held so the first
-    // deferred wake has already been consumed under contention.
-    for _ in 0..32 {
-        tokio::task::yield_now().await;
-    }
-
-    drop(held_guard);
-
-    let completed = timeout(Duration::from_millis(300), writer)
-        .await
-        .expect("writer must not stay parked forever after release")
-        .expect("writer task must not panic");
-    assert!(completed.is_ok());
-}
-
-#[tokio::test(flavor = "multi_thread", worker_threads = 4)]
-async fn integration_parallel_waiters_resume_after_single_release_event() {
-    let _guard = quota_test_guard();
-
-    let _retained = saturate_lock_cache();
-    let user = format!("quota-liveness-integration-{}", std::process::id());
-    let stats = Arc::new(Stats::new());
-    let barrier = Arc::new(Barrier::new(13));
-
-    let lock = quota_user_lock(&user);
-    let held_guard = lock
-        .try_lock()
-        .expect("test must hold user quota lock before launching waiters");
-
-    let mut waiters = Vec::new();
-    for _ in 0..12 {
-        let stats = Arc::clone(&stats);
-        let user = user.clone();
-        let barrier = Arc::clone(&barrier);
-        waiters.push(tokio::spawn(async move {
-            let counters = Arc::new(SharedCounters::new());
-            let quota_exceeded = Arc::new(AtomicBool::new(false));
-            let mut io = StatsIo::new(
-                tokio::io::sink(),
-                counters,
-                stats,
-                user,
-                Some(4096),
-                quota_exceeded,
-                tokio::time::Instant::now(),
-            );
-            barrier.wait().await;
-            io.write_all(&[0x33]).await
-        }));
-    }
-
-    barrier.wait().await;
-    tokio::time::sleep(Duration::from_millis(4)).await;
-    drop(held_guard);
-
-    timeout(Duration::from_secs(1), async {
-        for waiter in waiters {
-            let outcome = waiter.await.expect("waiter must not panic");
-            assert!(
-                outcome.is_ok(),
-                "waiter must resume and complete after release"
-            );
-        }
-    })
-    .await
-    .expect("all waiters must complete in bounded time");
-}
-
-#[tokio::test]
-async fn light_fuzz_release_timing_matrix_preserves_liveness() {
-    let _guard = quota_test_guard();
-
-    let _retained = saturate_lock_cache();
-    let stats = Arc::new(Stats::new());
-
-    let mut seed = 0xD1CE_F00D_0123_4567u64;
-    for round in 0..64u32 {
-        seed ^= seed << 7;
-        seed ^= seed >> 9;
-        seed ^= seed << 8;
-
-        let delay_ms = 1 + (seed & 0x7) as u64;
-        let user = format!("quota-liveness-fuzz-{}-{round}", std::process::id());
-
-        let lock = quota_user_lock(&user);
-        let held_guard = lock
-            .try_lock()
-            .expect("test must hold user quota lock in fuzz round");
-
-        let counters = Arc::new(SharedCounters::new());
-        let quota_exceeded = Arc::new(AtomicBool::new(false));
-        let mut io = StatsIo::new(
-            tokio::io::sink(),
-            counters,
-            Arc::clone(&stats),
-            user,
-            Some(2048),
-            quota_exceeded,
-            tokio::time::Instant::now(),
-        );
-
-        let writer = tokio::spawn(async move { io.write_all(&[0x44]).await });
-
-        tokio::time::sleep(Duration::from_millis(delay_ms)).await;
-        drop(held_guard);
-
-        let done = timeout(Duration::from_millis(300), writer)
-            .await
-            .expect("fuzz round writer must complete")
-            .expect("fuzz writer task must not panic");
-        assert!(
-            done.is_ok(),
-            "fuzz round writer must not stall after release"
-        );
-    }
-}
-
-#[tokio::test(flavor = "multi_thread", worker_threads = 4)]
-async fn stress_repeated_contention_cycles_remain_live() {
-    let _guard = quota_test_guard();
-
-    let _retained = saturate_lock_cache();
-    let stats = Arc::new(Stats::new());
-
-    for cycle in 0..40u32 {
-        let user = format!("quota-liveness-stress-{}-{cycle}", std::process::id());
-        let lock = quota_user_lock(&user);
-        let held_guard = lock
-            .try_lock()
-            .expect("test must hold lock before stress cycle");
-
-        let mut tasks = Vec::new();
-        for _ in 0..6 {
-            let stats = Arc::clone(&stats);
-            let user = user.clone();
-            tasks.push(tokio::spawn(async move {
-                let counters = Arc::new(SharedCounters::new());
-                let quota_exceeded = Arc::new(AtomicBool::new(false));
-                let mut io = StatsIo::new(
-                    tokio::io::sink(),
-                    counters,
-                    stats,
-                    user,
-                    Some(2048),
-                    quota_exceeded,
-                    tokio::time::Instant::now(),
-                );
-                io.write_all(&[0x55]).await
-            }));
-        }
-
-        tokio::task::yield_now().await;
-        drop(held_guard);
-
-        timeout(Duration::from_millis(700), async {
-            for task in tasks {
-                let outcome = task.await.expect("stress task must not panic");
-                assert!(outcome.is_ok(), "stress writer must complete");
-            }
-        })
-        .await
-        .expect("stress cycle must finish in bounded time");
-    }
-}

src/proxy/tests/relay_quota_waker_storm_adversarial_tests.rs

@@ -1,310 +0,0 @@
-use super::*;
-use crate::stats::Stats;
-use dashmap::DashMap;
-use std::pin::Pin;
-use std::sync::Arc;
-use std::sync::atomic::{AtomicBool, AtomicUsize, Ordering};
-use std::task::{Context, Waker};
-use tokio::io::{AsyncWriteExt, ReadBuf};
-use tokio::time::{Duration, timeout};
-
-#[derive(Default)]
-struct WakeCounter {
-    wakes: AtomicUsize,
-}
-
-impl std::task::Wake for WakeCounter {
-    fn wake(self: Arc<Self>) {
-        self.wakes.fetch_add(1, Ordering::Relaxed);
-    }
-
-    fn wake_by_ref(self: &Arc<Self>) {
-        self.wakes.fetch_add(1, Ordering::Relaxed);
-    }
-}
-
-fn quota_test_guard() -> impl Drop {
-    super::quota_user_lock_test_scope()
-}
-
-fn saturate_quota_user_locks() -> Vec<Arc<std::sync::Mutex<()>>> {
-    let map = QUOTA_USER_LOCKS.get_or_init(DashMap::new);
-    map.clear();
-
-    let mut retained = Vec::with_capacity(QUOTA_USER_LOCKS_MAX);
-    for idx in 0..QUOTA_USER_LOCKS_MAX {
-        retained.push(quota_user_lock(&format!("quota-waker-saturate-{idx}")));
-    }
-    retained
-}
-
-#[tokio::test]
-async fn positive_contended_writer_emits_deferred_wake_for_liveness() {
-    let _guard = quota_test_guard();
-
-    let _retained = saturate_quota_user_locks();
-    let stats = Arc::new(Stats::new());
-    let user = "quota-waker-positive-user";
-
-    let lock = quota_user_lock(user);
-    let held_guard = lock
-        .try_lock()
-        .expect("test must hold overflow lock before polling writer");
-
-    let counters = Arc::new(SharedCounters::new());
-    let quota_exceeded = Arc::new(AtomicBool::new(false));
-    let mut io = StatsIo::new(
-        tokio::io::sink(),
-        counters,
-        Arc::clone(&stats),
-        user.to_string(),
-        Some(1024),
-        quota_exceeded,
-        tokio::time::Instant::now(),
-    );
-
-    let wake_counter = Arc::new(WakeCounter::default());
-    let waker = Waker::from(Arc::clone(&wake_counter));
-    let mut cx = Context::from_waker(&waker);
-
-    let pending = Pin::new(&mut io).poll_write(&mut cx, &[0xA1]);
-    assert!(pending.is_pending());
-
-    timeout(Duration::from_millis(100), async {
-        loop {
-            if wake_counter.wakes.load(Ordering::Relaxed) >= 1 {
-                break;
-            }
-            tokio::task::yield_now().await;
-        }
-    })
-    .await
-    .expect("contended writer must receive deferred wake");
-
-    drop(held_guard);
-    let ready = Pin::new(&mut io).poll_write(&mut cx, &[0xA2]);
-    assert!(
-        ready.is_ready(),
-        "writer must progress after contention release"
-    );
-}
-
-#[tokio::test]
-async fn adversarial_blackhat_writer_contention_does_not_create_waker_storm() {
-    let _guard = quota_test_guard();
-
-    let _retained = saturate_quota_user_locks();
-    let stats = Arc::new(Stats::new());
-    let user = "quota-waker-blackhat-writer";
-
-    let lock = quota_user_lock(user);
-    let held_guard = lock
-        .try_lock()
-        .expect("test must hold overflow lock before polling writer");
-
-    let counters = Arc::new(SharedCounters::new());
-    let quota_exceeded = Arc::new(AtomicBool::new(false));
-    let mut io = StatsIo::new(
-        tokio::io::sink(),
-        counters,
-        Arc::clone(&stats),
-        user.to_string(),
-        Some(1024),
-        quota_exceeded,
-        tokio::time::Instant::now(),
-    );
-
-    let wake_counter = Arc::new(WakeCounter::default());
-    let waker = Waker::from(Arc::clone(&wake_counter));
-    let mut cx = Context::from_waker(&waker);
-
-    for _ in 0..512 {
-        let poll = Pin::new(&mut io).poll_write(&mut cx, &[0xBE]);
-        assert!(
-            poll.is_pending(),
-            "writer must stay pending while lock is held"
-        );
-        tokio::task::yield_now().await;
-    }
-
-    let wakes = wake_counter.wakes.load(Ordering::Relaxed);
-    assert!(
-        wakes <= 128,
-        "pending writer retries must not trigger wake storm; observed wakes={wakes}"
-    );
-
-    drop(held_guard);
-    let ready = Pin::new(&mut io).poll_write(&mut cx, &[0xEF]);
-    assert!(ready.is_ready());
-}
-
-#[tokio::test]
-async fn edge_read_path_contention_keeps_wake_budget_bounded() {
-    let _guard = quota_test_guard();
-
-    let _retained = saturate_quota_user_locks();
-    let stats = Arc::new(Stats::new());
-    let user = "quota-waker-read-edge";
-
-    let lock = quota_user_lock(user);
-    let held_guard = lock
-        .try_lock()
-        .expect("test must hold overflow lock before polling reader");
-
-    let counters = Arc::new(SharedCounters::new());
-    let quota_exceeded = Arc::new(AtomicBool::new(false));
-    let mut io = StatsIo::new(
-        tokio::io::empty(),
-        counters,
-        Arc::clone(&stats),
-        user.to_string(),
-        Some(1024),
-        quota_exceeded,
-        tokio::time::Instant::now(),
-    );
-
-    let wake_counter = Arc::new(WakeCounter::default());
-    let waker = Waker::from(Arc::clone(&wake_counter));
-    let mut cx = Context::from_waker(&waker);
-    let mut storage = [0u8; 1];
-
-    for _ in 0..512 {
-        let mut buf = ReadBuf::new(&mut storage);
-        let poll = Pin::new(&mut io).poll_read(&mut cx, &mut buf);
-        assert!(poll.is_pending());
-        tokio::task::yield_now().await;
-    }
-
-    let wakes = wake_counter.wakes.load(Ordering::Relaxed);
-    assert!(
-        wakes <= 128,
-        "pending reader retries must not trigger wake storm; observed wakes={wakes}"
-    );
-
-    drop(held_guard);
-    let mut buf = ReadBuf::new(&mut storage);
-    let ready = Pin::new(&mut io).poll_read(&mut cx, &mut buf);
-    assert!(ready.is_ready());
-}
-
-#[tokio::test]
-async fn light_fuzz_mixed_poll_schedule_under_contention_stays_bounded() {
-    let _guard = quota_test_guard();
-
-    let _retained = saturate_quota_user_locks();
-    let stats = Arc::new(Stats::new());
-    let user = "quota-waker-fuzz-user";
-
-    let lock = quota_user_lock(user);
-    let held_guard = lock
-        .try_lock()
-        .expect("test must hold overflow lock before fuzz polling");
-
-    let counters_w = Arc::new(SharedCounters::new());
-    let mut writer_io = StatsIo::new(
-        tokio::io::sink(),
-        counters_w,
-        Arc::clone(&stats),
-        user.to_string(),
-        Some(1024),
-        Arc::new(AtomicBool::new(false)),
-        tokio::time::Instant::now(),
-    );
-
-    let counters_r = Arc::new(SharedCounters::new());
-    let mut reader_io = StatsIo::new(
-        tokio::io::empty(),
-        counters_r,
-        Arc::clone(&stats),
-        user.to_string(),
-        Some(1024),
-        Arc::new(AtomicBool::new(false)),
-        tokio::time::Instant::now(),
-    );
-
-    let wake_counter = Arc::new(WakeCounter::default());
-    let waker = Waker::from(Arc::clone(&wake_counter));
-    let mut cx = Context::from_waker(&waker);
-    let mut seed = 0xBADC_0FFE_EE11_2211u64;
-    let mut storage = [0u8; 1];
-
-    for _ in 0..1024 {
-        seed ^= seed << 7;
-        seed ^= seed >> 9;
-        seed ^= seed << 8;
-
-        if (seed & 1) == 0 {
-            let poll = Pin::new(&mut writer_io).poll_write(&mut cx, &[0x44]);
-            assert!(poll.is_pending());
-        } else {
-            let mut buf = ReadBuf::new(&mut storage);
-            let poll = Pin::new(&mut reader_io).poll_read(&mut cx, &mut buf);
-            assert!(poll.is_pending());
-        }
-        tokio::task::yield_now().await;
-    }
-
-    assert!(
-        wake_counter.wakes.load(Ordering::Relaxed) <= 192,
-        "mixed contention fuzz must keep deferred wake count tightly bounded"
-    );
-
-    drop(held_guard);
-    let ready_w = Pin::new(&mut writer_io).poll_write(&mut cx, &[0x55]);
-    assert!(ready_w.is_ready());
-
-    let mut buf = ReadBuf::new(&mut storage);
-    let ready_r = Pin::new(&mut reader_io).poll_read(&mut cx, &mut buf);
-    assert!(ready_r.is_ready());
-}
-
-#[tokio::test(flavor = "multi_thread", worker_threads = 4)]
-#[ignore = "red-team detector: reveals possible starvation if deferred wake fires before contention release"]
-async fn stress_many_contended_writers_complete_after_release() {
-    let _guard = quota_test_guard();
-
-    let _retained = saturate_quota_user_locks();
-    let user = "quota-waker-stress-user".to_string();
-    let stats = Arc::new(Stats::new());
-
-    let lock = quota_user_lock(&user);
-    let held_guard = lock
-        .try_lock()
-        .expect("test must hold overflow lock before launching contended tasks");
-
-    let mut tasks = Vec::new();
-    for _ in 0..32 {
-        let stats = Arc::clone(&stats);
-        let user = user.clone();
-        tasks.push(tokio::spawn(async move {
-            let counters = Arc::new(SharedCounters::new());
-            let quota_exceeded = Arc::new(AtomicBool::new(false));
-            let mut io = StatsIo::new(
-                tokio::io::sink(),
-                counters,
-                stats,
-                user,
-                Some(2048),
-                quota_exceeded,
-                tokio::time::Instant::now(),
-            );
-
-            io.write_all(&[0xAA]).await
-        }));
-    }
-
-    for _ in 0..8 {
-        tokio::task::yield_now().await;
-    }
-
-    drop(held_guard);
-
-    timeout(Duration::from_secs(2), async {
-        for task in tasks {
-            let result = task.await.expect("stress task must not panic");
-            assert!(result.is_ok(), "task must complete after lock release");
-        }
-    })
-    .await
-    .expect("all contended writer tasks must finish in bounded time after release");
-}

src/stats/mod.rs

@@ -238,10 +238,12 @@ pub struct Stats {
     me_inline_recovery_total: AtomicU64,
     ip_reservation_rollback_tcp_limit_total: AtomicU64,
     ip_reservation_rollback_quota_limit_total: AtomicU64,
+    quota_write_fail_bytes_total: AtomicU64,
+    quota_write_fail_events_total: AtomicU64,
     telemetry_core_enabled: AtomicBool,
     telemetry_user_enabled: AtomicBool,
     telemetry_me_level: AtomicU8,
-    user_stats: DashMap<String, UserStats>,
+    user_stats: DashMap<String, Arc<UserStats>>,
     user_stats_last_cleanup_epoch_secs: AtomicU64,
     start_time: parking_lot::RwLock<Option<Instant>>,
 }
@@ -254,9 +256,51 @@ pub struct UserStats {
     pub octets_to_client: AtomicU64,
     pub msgs_from_client: AtomicU64,
     pub msgs_to_client: AtomicU64,
+    /// Total bytes charged against per-user quota admission.
+    ///
+    /// This counter is the single source of truth for quota enforcement and
+    /// intentionally tracks attempted traffic, not guaranteed delivery.
+    pub quota_used: AtomicU64,
     pub last_seen_epoch_secs: AtomicU64,
 }
 
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum QuotaReserveError {
+    LimitExceeded,
+    Contended,
+}
+
+impl UserStats {
+    #[inline]
+    pub fn quota_used(&self) -> u64 {
+        self.quota_used.load(Ordering::Relaxed)
+    }
+
+    /// Attempts one CAS reservation step against the quota counter.
+    ///
+    /// Callers control retry/yield policy. This primitive intentionally does
+    /// not block or sleep so both sync poll paths and async paths can wrap it
+    /// with their own contention strategy.
+    #[inline]
+    pub fn quota_try_reserve(&self, bytes: u64, limit: u64) -> Result<u64, QuotaReserveError> {
+        let current = self.quota_used.load(Ordering::Relaxed);
+        if bytes > limit.saturating_sub(current) {
+            return Err(QuotaReserveError::LimitExceeded);
+        }
+
+        let next = current.saturating_add(bytes);
+        match self.quota_used.compare_exchange_weak(
+            current,
+            next,
+            Ordering::Relaxed,
+            Ordering::Relaxed,
+        ) {
+            Ok(_) => Ok(next),
+            Err(_) => Err(QuotaReserveError::Contended),
+        }
+    }
+}
+
 impl Stats {
     pub fn new() -> Self {
         let stats = Self::default();
@@ -316,6 +360,70 @@ impl Stats {
             .store(Self::now_epoch_secs(), Ordering::Relaxed);
     }
 
+    pub(crate) fn get_or_create_user_stats_handle(&self, user: &str) -> Arc<UserStats> {
+        self.maybe_cleanup_user_stats();
+        if let Some(existing) = self.user_stats.get(user) {
+            let handle = Arc::clone(existing.value());
+            Self::touch_user_stats(handle.as_ref());
+            return handle;
+        }
+
+        let entry = self.user_stats.entry(user.to_string()).or_default();
+        if entry.last_seen_epoch_secs.load(Ordering::Relaxed) == 0 {
+            Self::touch_user_stats(entry.value().as_ref());
+        }
+        Arc::clone(entry.value())
+    }
+
+    #[inline]
+    pub(crate) fn add_user_octets_from_handle(&self, user_stats: &UserStats, bytes: u64) {
+        if !self.telemetry_user_enabled() {
+            return;
+        }
+        Self::touch_user_stats(user_stats);
+        user_stats.octets_from_client.fetch_add(bytes, Ordering::Relaxed);
+    }
+
+    #[inline]
+    pub(crate) fn add_user_octets_to_handle(&self, user_stats: &UserStats, bytes: u64) {
+        if !self.telemetry_user_enabled() {
+            return;
+        }
+        Self::touch_user_stats(user_stats);
+        user_stats.octets_to_client.fetch_add(bytes, Ordering::Relaxed);
+    }
+
+    #[inline]
+    pub(crate) fn increment_user_msgs_from_handle(&self, user_stats: &UserStats) {
+        if !self.telemetry_user_enabled() {
+            return;
+        }
+        Self::touch_user_stats(user_stats);
+        user_stats.msgs_from_client.fetch_add(1, Ordering::Relaxed);
+    }
+
+    #[inline]
+    pub(crate) fn increment_user_msgs_to_handle(&self, user_stats: &UserStats) {
+        if !self.telemetry_user_enabled() {
+            return;
+        }
+        Self::touch_user_stats(user_stats);
+        user_stats.msgs_to_client.fetch_add(1, Ordering::Relaxed);
+    }
+
+    /// Charges already committed bytes in a post-I/O path.
+    ///
+    /// This helper is intentionally separate from `quota_try_reserve` to avoid
+    /// mixing reserve and post-charge on a single I/O event.
+    #[inline]
+    pub(crate) fn quota_charge_post_write(&self, user_stats: &UserStats, bytes: u64) -> u64 {
+        Self::touch_user_stats(user_stats);
+        user_stats
+            .quota_used
+            .fetch_add(bytes, Ordering::Relaxed)
+            .saturating_add(bytes)
+    }
+
     fn maybe_cleanup_user_stats(&self) {
         const USER_STATS_CLEANUP_INTERVAL_SECS: u64 = 60;
         const USER_STATS_IDLE_TTL_SECS: u64 = 24 * 60 * 60;
@@ -1114,6 +1222,18 @@ impl Stats {
                 .fetch_add(1, Ordering::Relaxed);
         }
     }
+    pub fn add_quota_write_fail_bytes_total(&self, bytes: u64) {
+        if self.telemetry_core_enabled() {
+            self.quota_write_fail_bytes_total
+                .fetch_add(bytes, Ordering::Relaxed);
+        }
+    }
+    pub fn increment_quota_write_fail_events_total(&self) {
+        if self.telemetry_core_enabled() {
+            self.quota_write_fail_events_total
+                .fetch_add(1, Ordering::Relaxed);
+        }
+    }
     pub fn increment_me_endpoint_quarantine_total(&self) {
         if self.telemetry_me_allows_normal() {
             self.me_endpoint_quarantine_total
@@ -1764,19 +1884,19 @@ impl Stats {
         self.ip_reservation_rollback_quota_limit_total
             .load(Ordering::Relaxed)
     }
+    pub fn get_quota_write_fail_bytes_total(&self) -> u64 {
+        self.quota_write_fail_bytes_total.load(Ordering::Relaxed)
+    }
+    pub fn get_quota_write_fail_events_total(&self) -> u64 {
+        self.quota_write_fail_events_total.load(Ordering::Relaxed)
+    }
 
     pub fn increment_user_connects(&self, user: &str) {
         if !self.telemetry_user_enabled() {
             return;
         }
-        self.maybe_cleanup_user_stats();
-        if let Some(stats) = self.user_stats.get(user) {
-            Self::touch_user_stats(stats.value());
-            stats.connects.fetch_add(1, Ordering::Relaxed);
-            return;
-        }
-        let stats = self.user_stats.entry(user.to_string()).or_default();
-        Self::touch_user_stats(stats.value());
+        let stats = self.get_or_create_user_stats_handle(user);
+        Self::touch_user_stats(stats.as_ref());
         stats.connects.fetch_add(1, Ordering::Relaxed);
     }
 
@@ -1784,14 +1904,8 @@ impl Stats {
         if !self.telemetry_user_enabled() {
             return;
         }
-        self.maybe_cleanup_user_stats();
-        if let Some(stats) = self.user_stats.get(user) {
-            Self::touch_user_stats(stats.value());
-            stats.curr_connects.fetch_add(1, Ordering::Relaxed);
-            return;
-        }
-        let stats = self.user_stats.entry(user.to_string()).or_default();
-        Self::touch_user_stats(stats.value());
+        let stats = self.get_or_create_user_stats_handle(user);
+        Self::touch_user_stats(stats.as_ref());
         stats.curr_connects.fetch_add(1, Ordering::Relaxed);
     }
 
@@ -1800,9 +1914,8 @@ impl Stats {
             return true;
         }
 
-        self.maybe_cleanup_user_stats();
-        let stats = self.user_stats.entry(user.to_string()).or_default();
-        Self::touch_user_stats(stats.value());
+        let stats = self.get_or_create_user_stats_handle(user);
+        Self::touch_user_stats(stats.as_ref());
 
         let counter = &stats.curr_connects;
         let mut current = counter.load(Ordering::Relaxed);
@@ -1827,7 +1940,7 @@ impl Stats {
     pub fn decrement_user_curr_connects(&self, user: &str) {
         self.maybe_cleanup_user_stats();
         if let Some(stats) = self.user_stats.get(user) {
-            Self::touch_user_stats(stats.value());
+            Self::touch_user_stats(stats.value().as_ref());
             let counter = &stats.curr_connects;
             let mut current = counter.load(Ordering::Relaxed);
             loop {
@@ -1858,60 +1971,32 @@ impl Stats {
         if !self.telemetry_user_enabled() {
             return;
         }
-        self.maybe_cleanup_user_stats();
-        if let Some(stats) = self.user_stats.get(user) {
-            Self::touch_user_stats(stats.value());
-            stats.octets_from_client.fetch_add(bytes, Ordering::Relaxed);
-            return;
-        }
-        let stats = self.user_stats.entry(user.to_string()).or_default();
-        Self::touch_user_stats(stats.value());
-        stats.octets_from_client.fetch_add(bytes, Ordering::Relaxed);
+        let stats = self.get_or_create_user_stats_handle(user);
+        self.add_user_octets_from_handle(stats.as_ref(), bytes);
     }
 
     pub fn add_user_octets_to(&self, user: &str, bytes: u64) {
         if !self.telemetry_user_enabled() {
             return;
         }
-        self.maybe_cleanup_user_stats();
-        if let Some(stats) = self.user_stats.get(user) {
-            Self::touch_user_stats(stats.value());
-            stats.octets_to_client.fetch_add(bytes, Ordering::Relaxed);
-            return;
-        }
-        let stats = self.user_stats.entry(user.to_string()).or_default();
-        Self::touch_user_stats(stats.value());
-        stats.octets_to_client.fetch_add(bytes, Ordering::Relaxed);
+        let stats = self.get_or_create_user_stats_handle(user);
+        self.add_user_octets_to_handle(stats.as_ref(), bytes);
     }
 
     pub fn increment_user_msgs_from(&self, user: &str) {
         if !self.telemetry_user_enabled() {
             return;
         }
-        self.maybe_cleanup_user_stats();
-        if let Some(stats) = self.user_stats.get(user) {
-            Self::touch_user_stats(stats.value());
-            stats.msgs_from_client.fetch_add(1, Ordering::Relaxed);
-            return;
-        }
-        let stats = self.user_stats.entry(user.to_string()).or_default();
-        Self::touch_user_stats(stats.value());
-        stats.msgs_from_client.fetch_add(1, Ordering::Relaxed);
+        let stats = self.get_or_create_user_stats_handle(user);
+        self.increment_user_msgs_from_handle(stats.as_ref());
     }
 
     pub fn increment_user_msgs_to(&self, user: &str) {
         if !self.telemetry_user_enabled() {
             return;
         }
-        self.maybe_cleanup_user_stats();
-        if let Some(stats) = self.user_stats.get(user) {
-            Self::touch_user_stats(stats.value());
-            stats.msgs_to_client.fetch_add(1, Ordering::Relaxed);
-            return;
-        }
-        let stats = self.user_stats.entry(user.to_string()).or_default();
-        Self::touch_user_stats(stats.value());
-        stats.msgs_to_client.fetch_add(1, Ordering::Relaxed);
+        let stats = self.get_or_create_user_stats_handle(user);
+        self.increment_user_msgs_to_handle(stats.as_ref());
     }
 
     pub fn get_user_total_octets(&self, user: &str) -> u64 {
@@ -1924,6 +2009,13 @@ impl Stats {
             .unwrap_or(0)
     }
 
+    pub fn get_user_quota_used(&self, user: &str) -> u64 {
+        self.user_stats
+            .get(user)
+            .map(|s| s.quota_used.load(Ordering::Relaxed))
+            .unwrap_or(0)
+    }
+
     pub fn get_handshake_timeouts(&self) -> u64 {
         self.handshake_timeouts.load(Ordering::Relaxed)
     }
@@ -1989,7 +2081,7 @@ impl Stats {
             .load(Ordering::Relaxed)
     }
 
-    pub fn iter_user_stats(&self) -> dashmap::iter::Iter<'_, String, UserStats> {
+    pub fn iter_user_stats(&self) -> dashmap::iter::Iter<'_, String, Arc<UserStats>> {
         self.user_stats.iter()
     }
 
@@ -2137,6 +2229,22 @@ impl ReplayChecker {
         found
     }
 
+    fn check_only_internal(
+        &self,
+        data: &[u8],
+        shards: &[Mutex<ReplayShard>],
+        window: Duration,
+    ) -> bool {
+        self.checks.fetch_add(1, Ordering::Relaxed);
+        let idx = self.get_shard_idx(data);
+        let mut shard = shards[idx].lock();
+        let found = shard.check(data, Instant::now(), window);
+        if found {
+            self.hits.fetch_add(1, Ordering::Relaxed);
+        }
+        found
+    }
+
     fn add_only(&self, data: &[u8], shards: &[Mutex<ReplayShard>], window: Duration) {
         self.additions.fetch_add(1, Ordering::Relaxed);
         let idx = self.get_shard_idx(data);
@@ -2160,7 +2268,7 @@ impl ReplayChecker {
         self.add_only(data, &self.handshake_shards, self.window)
     }
     pub fn check_tls_digest(&self, data: &[u8]) -> bool {
-        self.check_and_add_tls_digest(data)
+        self.check_only_internal(data, &self.tls_shards, self.tls_window)
     }
     pub fn add_tls_digest(&self, data: &[u8]) {
         self.add_only(data, &self.tls_shards, self.tls_window)
@@ -2263,6 +2371,7 @@ impl ReplayStats {
 mod tests {
     use super::*;
     use crate::config::MeTelemetryLevel;
+    use std::sync::atomic::{AtomicU64, Ordering};
     use std::sync::Arc;
 
     #[test]
@@ -2431,6 +2540,60 @@ mod tests {
         }
         assert_eq!(checker.stats().total_entries, 500);
     }
+
+    #[test]
+    fn test_quota_reserve_under_contention_hits_limit_exactly() {
+        let user_stats = Arc::new(UserStats::default());
+        let successes = Arc::new(AtomicU64::new(0));
+        let limit = 8_192u64;
+        let mut workers = Vec::new();
+
+        for _ in 0..8 {
+            let user_stats = user_stats.clone();
+            let successes = successes.clone();
+            workers.push(std::thread::spawn(move || {
+                loop {
+                    match user_stats.quota_try_reserve(1, limit) {
+                        Ok(_) => {
+                            successes.fetch_add(1, Ordering::Relaxed);
+                        }
+                        Err(QuotaReserveError::Contended) => {
+                            std::hint::spin_loop();
+                        }
+                        Err(QuotaReserveError::LimitExceeded) => {
+                            break;
+                        }
+                    }
+                }
+            }));
+        }
+
+        for worker in workers {
+            worker.join().expect("worker thread must finish");
+        }
+
+        assert_eq!(
+            successes.load(Ordering::Relaxed),
+            limit,
+            "successful reservations must stop exactly at limit"
+        );
+        assert_eq!(user_stats.quota_used(), limit);
+    }
+
+    #[test]
+    fn test_quota_used_is_authoritative_and_independent_from_octets_telemetry() {
+        let stats = Stats::new();
+        let user = "quota-authoritative-user";
+        let user_stats = stats.get_or_create_user_stats_handle(user);
+
+        stats.add_user_octets_to_handle(&user_stats, 5);
+        assert_eq!(stats.get_user_total_octets(user), 5);
+        assert_eq!(stats.get_user_quota_used(user), 0);
+
+        stats.quota_charge_post_write(&user_stats, 7);
+        assert_eq!(stats.get_user_total_octets(user), 5);
+        assert_eq!(stats.get_user_quota_used(user), 7);
+    }
 }
 
 #[cfg(test)]