Advanced TLS Fetcher

Co-Authored-By: brekotis <93345790+brekotis@users.noreply.github.com>

src/config/defaults.rs

@@ -71,6 +71,22 @@ pub(crate) fn default_tls_fetch_scope() -> String {
     String::new()
 }
 
+pub(crate) fn default_tls_fetch_attempt_timeout_ms() -> u64 {
+    5_000
+}
+
+pub(crate) fn default_tls_fetch_total_budget_ms() -> u64 {
+    15_000
+}
+
+pub(crate) fn default_tls_fetch_strict_route() -> bool {
+    true
+}
+
+pub(crate) fn default_tls_fetch_profile_cache_ttl_secs() -> u64 {
+    600
+}
+
 pub(crate) fn default_mask_port() -> u16 {
     443
 }

src/config/load.rs

@@ -1,6 +1,6 @@
 #![allow(deprecated)]
 
-use std::collections::{BTreeSet, HashMap};
+use std::collections::{BTreeSet, HashMap, HashSet};
 use std::hash::{DefaultHasher, Hash, Hasher};
 use std::net::{IpAddr, SocketAddr};
 use std::path::{Path, PathBuf};
@@ -977,6 +977,28 @@ impl ProxyConfig {
         // Normalize optional TLS fetch scope: whitespace-only values disable scoped routing.
         config.censorship.tls_fetch_scope = config.censorship.tls_fetch_scope.trim().to_string();
 
+        if config.censorship.tls_fetch.profiles.is_empty() {
+            config.censorship.tls_fetch.profiles = TlsFetchConfig::default().profiles;
+        } else {
+            let mut seen = HashSet::new();
+            config
+                .censorship
+                .tls_fetch
+                .profiles
+                .retain(|profile| seen.insert(*profile));
+        }
+
+        if config.censorship.tls_fetch.attempt_timeout_ms == 0 {
+            return Err(ProxyError::Config(
+                "censorship.tls_fetch.attempt_timeout_ms must be > 0".to_string(),
+            ));
+        }
+        if config.censorship.tls_fetch.total_budget_ms == 0 {
+            return Err(ProxyError::Config(
+                "censorship.tls_fetch.total_budget_ms must be > 0".to_string(),
+            ));
+        }
+
         // Merge primary + extra TLS domains, deduplicate (primary always first).
         if !config.censorship.tls_domains.is_empty() {
             let mut all = Vec::with_capacity(1 + config.censorship.tls_domains.len());
@@ -2459,6 +2481,94 @@ mod tests {
         let _ = std::fs::remove_file(path);
     }
 
+    #[test]
+    fn tls_fetch_defaults_are_applied() {
+        let toml = r#"
+            [censorship]
+            tls_domain = "example.com"
+
+            [access.users]
+            user = "00000000000000000000000000000000"
+        "#;
+        let dir = std::env::temp_dir();
+        let path = dir.join("telemt_tls_fetch_defaults_test.toml");
+        std::fs::write(&path, toml).unwrap();
+        let cfg = ProxyConfig::load(&path).unwrap();
+        assert_eq!(
+            cfg.censorship.tls_fetch.profiles,
+            TlsFetchConfig::default().profiles
+        );
+        assert!(cfg.censorship.tls_fetch.strict_route);
+        assert_eq!(cfg.censorship.tls_fetch.attempt_timeout_ms, 5_000);
+        assert_eq!(cfg.censorship.tls_fetch.total_budget_ms, 15_000);
+        assert_eq!(cfg.censorship.tls_fetch.profile_cache_ttl_secs, 600);
+        let _ = std::fs::remove_file(path);
+    }
+
+    #[test]
+    fn tls_fetch_profiles_are_deduplicated_preserving_order() {
+        let toml = r#"
+            [censorship]
+            tls_domain = "example.com"
+            [censorship.tls_fetch]
+            profiles = ["compat_tls12", "modern_chrome_like", "compat_tls12", "legacy_minimal"]
+
+            [access.users]
+            user = "00000000000000000000000000000000"
+        "#;
+        let dir = std::env::temp_dir();
+        let path = dir.join("telemt_tls_fetch_profiles_dedup_test.toml");
+        std::fs::write(&path, toml).unwrap();
+        let cfg = ProxyConfig::load(&path).unwrap();
+        assert_eq!(
+            cfg.censorship.tls_fetch.profiles,
+            vec![
+                TlsFetchProfile::CompatTls12,
+                TlsFetchProfile::ModernChromeLike,
+                TlsFetchProfile::LegacyMinimal
+            ]
+        );
+        let _ = std::fs::remove_file(path);
+    }
+
+    #[test]
+    fn tls_fetch_attempt_timeout_zero_is_rejected() {
+        let toml = r#"
+            [censorship]
+            tls_domain = "example.com"
+            [censorship.tls_fetch]
+            attempt_timeout_ms = 0
+
+            [access.users]
+            user = "00000000000000000000000000000000"
+        "#;
+        let dir = std::env::temp_dir();
+        let path = dir.join("telemt_tls_fetch_attempt_timeout_zero_test.toml");
+        std::fs::write(&path, toml).unwrap();
+        let err = ProxyConfig::load(&path).unwrap_err().to_string();
+        assert!(err.contains("censorship.tls_fetch.attempt_timeout_ms must be > 0"));
+        let _ = std::fs::remove_file(path);
+    }
+
+    #[test]
+    fn tls_fetch_total_budget_zero_is_rejected() {
+        let toml = r#"
+            [censorship]
+            tls_domain = "example.com"
+            [censorship.tls_fetch]
+            total_budget_ms = 0
+
+            [access.users]
+            user = "00000000000000000000000000000000"
+        "#;
+        let dir = std::env::temp_dir();
+        let path = dir.join("telemt_tls_fetch_total_budget_zero_test.toml");
+        std::fs::write(&path, toml).unwrap();
+        let err = ProxyConfig::load(&path).unwrap_err().to_string();
+        assert!(err.contains("censorship.tls_fetch.total_budget_ms must be > 0"));
+        let _ = std::fs::remove_file(path);
+    }
+
     #[test]
     fn invalid_ad_tag_is_disabled_during_load() {
         let toml = r#"

src/config/types.rs

@@ -1367,6 +1367,82 @@ pub enum UnknownSniAction {
     Mask,
 }
 
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash, Serialize, Deserialize)]
+#[serde(rename_all = "snake_case")]
+pub enum TlsFetchProfile {
+    ModernChromeLike,
+    ModernFirefoxLike,
+    CompatTls12,
+    LegacyMinimal,
+}
+
+impl TlsFetchProfile {
+    pub fn as_str(self) -> &'static str {
+        match self {
+            TlsFetchProfile::ModernChromeLike => "modern_chrome_like",
+            TlsFetchProfile::ModernFirefoxLike => "modern_firefox_like",
+            TlsFetchProfile::CompatTls12 => "compat_tls12",
+            TlsFetchProfile::LegacyMinimal => "legacy_minimal",
+        }
+    }
+}
+
+fn default_tls_fetch_profiles() -> Vec<TlsFetchProfile> {
+    vec![
+        TlsFetchProfile::ModernChromeLike,
+        TlsFetchProfile::ModernFirefoxLike,
+        TlsFetchProfile::CompatTls12,
+        TlsFetchProfile::LegacyMinimal,
+    ]
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct TlsFetchConfig {
+    /// Ordered list of ClientHello profiles used for adaptive fallback.
+    #[serde(default = "default_tls_fetch_profiles")]
+    pub profiles: Vec<TlsFetchProfile>,
+
+    /// When true and upstream route is configured, TLS fetch fails closed on
+    /// upstream connect errors and does not fallback to direct TCP.
+    #[serde(default = "default_tls_fetch_strict_route")]
+    pub strict_route: bool,
+
+    /// Timeout per one profile attempt in milliseconds.
+    #[serde(default = "default_tls_fetch_attempt_timeout_ms")]
+    pub attempt_timeout_ms: u64,
+
+    /// Total wall-clock budget in milliseconds across all profile attempts.
+    #[serde(default = "default_tls_fetch_total_budget_ms")]
+    pub total_budget_ms: u64,
+
+    /// Adds GREASE-style values into selected ClientHello extensions.
+    #[serde(default)]
+    pub grease_enabled: bool,
+
+    /// Produces deterministic ClientHello randomness for debugging/tests.
+    #[serde(default)]
+    pub deterministic: bool,
+
+    /// TTL for winner-profile cache entries in seconds.
+    /// Set to 0 to disable profile cache.
+    #[serde(default = "default_tls_fetch_profile_cache_ttl_secs")]
+    pub profile_cache_ttl_secs: u64,
+}
+
+impl Default for TlsFetchConfig {
+    fn default() -> Self {
+        Self {
+            profiles: default_tls_fetch_profiles(),
+            strict_route: default_tls_fetch_strict_route(),
+            attempt_timeout_ms: default_tls_fetch_attempt_timeout_ms(),
+            total_budget_ms: default_tls_fetch_total_budget_ms(),
+            grease_enabled: false,
+            deterministic: false,
+            profile_cache_ttl_secs: default_tls_fetch_profile_cache_ttl_secs(),
+        }
+    }
+}
+
 #[derive(Debug, Clone, Serialize, Deserialize)]
 pub struct AntiCensorshipConfig {
     #[serde(default = "default_tls_domain")]
@@ -1385,6 +1461,10 @@ pub struct AntiCensorshipConfig {
     #[serde(default = "default_tls_fetch_scope")]
     pub tls_fetch_scope: String,
 
+    /// Fetch strategy for TLS front metadata bootstrap and periodic refresh.
+    #[serde(default)]
+    pub tls_fetch: TlsFetchConfig,
+
     #[serde(default = "default_true")]
     pub mask: bool,
 
@@ -1492,6 +1572,7 @@ impl Default for AntiCensorshipConfig {
             tls_domains: Vec::new(),
             unknown_sni_action: UnknownSniAction::Drop,
             tls_fetch_scope: default_tls_fetch_scope(),
+            tls_fetch: TlsFetchConfig::default(),
             mask: default_true(),
             mask_host: None,
             mask_port: default_mask_port(),

src/maestro/tls_bootstrap.rs

@@ -7,6 +7,7 @@ use tracing::warn;
 use crate::config::ProxyConfig;
 use crate::startup::{COMPONENT_TLS_FRONT_BOOTSTRAP, StartupTracker};
 use crate::tls_front::TlsFrontCache;
+use crate::tls_front::fetcher::TlsFetchStrategy;
 use crate::transport::UpstreamManager;
 
 pub(crate) async fn bootstrap_tls_front(
@@ -40,7 +41,17 @@ pub(crate) async fn bootstrap_tls_front(
         let mask_unix_sock = config.censorship.mask_unix_sock.clone();
         let tls_fetch_scope = (!config.censorship.tls_fetch_scope.is_empty())
             .then(|| config.censorship.tls_fetch_scope.clone());
-        let fetch_timeout = Duration::from_secs(5);
+        let tls_fetch = config.censorship.tls_fetch.clone();
+        let fetch_strategy = TlsFetchStrategy {
+            profiles: tls_fetch.profiles,
+            strict_route: tls_fetch.strict_route,
+            attempt_timeout: Duration::from_millis(tls_fetch.attempt_timeout_ms.max(1)),
+            total_budget: Duration::from_millis(tls_fetch.total_budget_ms.max(1)),
+            grease_enabled: tls_fetch.grease_enabled,
+            deterministic: tls_fetch.deterministic,
+            profile_cache_ttl: Duration::from_secs(tls_fetch.profile_cache_ttl_secs),
+        };
+        let fetch_timeout = fetch_strategy.total_budget;
 
         let cache_initial = cache.clone();
         let domains_initial = tls_domains.to_vec();
@@ -48,6 +59,7 @@ pub(crate) async fn bootstrap_tls_front(
         let unix_sock_initial = mask_unix_sock.clone();
         let scope_initial = tls_fetch_scope.clone();
         let upstream_initial = upstream_manager.clone();
+        let strategy_initial = fetch_strategy.clone();
         tokio::spawn(async move {
             let mut join = tokio::task::JoinSet::new();
             for domain in domains_initial {
@@ -56,12 +68,13 @@ pub(crate) async fn bootstrap_tls_front(
                 let unix_sock_domain = unix_sock_initial.clone();
                 let scope_domain = scope_initial.clone();
                 let upstream_domain = upstream_initial.clone();
+                let strategy_domain = strategy_initial.clone();
                 join.spawn(async move {
-                    match crate::tls_front::fetcher::fetch_real_tls(
+                    match crate::tls_front::fetcher::fetch_real_tls_with_strategy(
                         &host_domain,
                         port,
                         &domain,
-                        fetch_timeout,
+                        &strategy_domain,
                         Some(upstream_domain),
                         scope_domain.as_deref(),
                         proxy_protocol,
@@ -107,6 +120,7 @@ pub(crate) async fn bootstrap_tls_front(
         let unix_sock_refresh = mask_unix_sock.clone();
         let scope_refresh = tls_fetch_scope.clone();
         let upstream_refresh = upstream_manager.clone();
+        let strategy_refresh = fetch_strategy.clone();
         tokio::spawn(async move {
             loop {
                 let base_secs = rand::rng().random_range(4 * 3600..=6 * 3600);
@@ -120,12 +134,13 @@ pub(crate) async fn bootstrap_tls_front(
                     let unix_sock_domain = unix_sock_refresh.clone();
                     let scope_domain = scope_refresh.clone();
                     let upstream_domain = upstream_refresh.clone();
+                    let strategy_domain = strategy_refresh.clone();
                     join.spawn(async move {
-                        match crate::tls_front::fetcher::fetch_real_tls(
+                        match crate::tls_front::fetcher::fetch_real_tls_with_strategy(
                             &host_domain,
                             port,
                             &domain,
-                            fetch_timeout,
+                            &strategy_domain,
                             Some(upstream_domain),
                             scope_domain.as_deref(),
                             proxy_protocol,

src/tls_front/fetcher.rs

@@ -1,7 +1,9 @@
 #![allow(clippy::too_many_arguments)]
 
+use dashmap::DashMap;
 use std::sync::Arc;
-use std::time::Duration;
+use std::sync::OnceLock;
+use std::time::{Duration, Instant};
 
 use anyhow::{Result, anyhow};
 use tokio::io::{AsyncRead, AsyncReadExt, AsyncWrite, AsyncWriteExt};
@@ -21,7 +23,8 @@ use rustls::{DigitallySignedStruct, Error as RustlsError};
 use x509_parser::certificate::X509Certificate;
 use x509_parser::prelude::FromDer;
 
-use crate::crypto::SecureRandom;
+use crate::config::TlsFetchProfile;
+use crate::crypto::{SecureRandom, sha256};
 use crate::network::dns_overrides::resolve_socket_addr;
 use crate::protocol::constants::{
     TLS_RECORD_APPLICATION, TLS_RECORD_CHANGE_CIPHER, TLS_RECORD_HANDSHAKE,
@@ -78,6 +81,197 @@ impl ServerCertVerifier for NoVerify {
     }
 }
 
+#[derive(Debug, Clone)]
+pub struct TlsFetchStrategy {
+    pub profiles: Vec<TlsFetchProfile>,
+    pub strict_route: bool,
+    pub attempt_timeout: Duration,
+    pub total_budget: Duration,
+    pub grease_enabled: bool,
+    pub deterministic: bool,
+    pub profile_cache_ttl: Duration,
+}
+
+impl TlsFetchStrategy {
+    #[allow(dead_code)]
+    pub fn single_attempt(connect_timeout: Duration) -> Self {
+        Self {
+            profiles: vec![TlsFetchProfile::CompatTls12],
+            strict_route: false,
+            attempt_timeout: connect_timeout.max(Duration::from_millis(1)),
+            total_budget: connect_timeout.max(Duration::from_millis(1)),
+            grease_enabled: false,
+            deterministic: false,
+            profile_cache_ttl: Duration::ZERO,
+        }
+    }
+}
+
+#[derive(Debug, Clone, PartialEq, Eq, Hash)]
+struct ProfileCacheKey {
+    host: String,
+    port: u16,
+    sni: String,
+    scope: Option<String>,
+    proxy_protocol: u8,
+    route_hint: RouteHint,
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+enum RouteHint {
+    Direct,
+    Upstream,
+    Unix,
+}
+
+#[derive(Debug, Clone, Copy)]
+struct ProfileCacheValue {
+    profile: TlsFetchProfile,
+    updated_at: Instant,
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+enum FetchErrorKind {
+    Connect,
+    Route,
+    EarlyEof,
+    Timeout,
+    ServerHelloMissing,
+    TlsAlert,
+    Parse,
+    Other,
+}
+
+static PROFILE_CACHE: OnceLock<DashMap<ProfileCacheKey, ProfileCacheValue>> = OnceLock::new();
+
+fn profile_cache() -> &'static DashMap<ProfileCacheKey, ProfileCacheValue> {
+    PROFILE_CACHE.get_or_init(DashMap::new)
+}
+
+fn route_hint(
+    upstream: Option<&std::sync::Arc<crate::transport::UpstreamManager>>,
+    unix_sock: Option<&str>,
+) -> RouteHint {
+    if unix_sock.is_some() {
+        RouteHint::Unix
+    } else if upstream.is_some() {
+        RouteHint::Upstream
+    } else {
+        RouteHint::Direct
+    }
+}
+
+fn profile_cache_key(
+    host: &str,
+    port: u16,
+    sni: &str,
+    upstream: Option<&std::sync::Arc<crate::transport::UpstreamManager>>,
+    scope: Option<&str>,
+    proxy_protocol: u8,
+    unix_sock: Option<&str>,
+) -> ProfileCacheKey {
+    ProfileCacheKey {
+        host: host.to_string(),
+        port,
+        sni: sni.to_string(),
+        scope: scope.map(ToString::to_string),
+        proxy_protocol,
+        route_hint: route_hint(upstream, unix_sock),
+    }
+}
+
+fn classify_fetch_error(err: &anyhow::Error) -> FetchErrorKind {
+    for cause in err.chain() {
+        if let Some(io) = cause.downcast_ref::<std::io::Error>() {
+            return match io.kind() {
+                std::io::ErrorKind::TimedOut => FetchErrorKind::Timeout,
+                std::io::ErrorKind::UnexpectedEof => FetchErrorKind::EarlyEof,
+                std::io::ErrorKind::ConnectionRefused
+                | std::io::ErrorKind::ConnectionAborted
+                | std::io::ErrorKind::ConnectionReset
+                | std::io::ErrorKind::NotConnected
+                | std::io::ErrorKind::AddrNotAvailable => FetchErrorKind::Connect,
+                _ => FetchErrorKind::Other,
+            };
+        }
+    }
+
+    let message = err.to_string().to_lowercase();
+    if message.contains("upstream route") {
+        FetchErrorKind::Route
+    } else if message.contains("serverhello not received") {
+        FetchErrorKind::ServerHelloMissing
+    } else if message.contains("alert") {
+        FetchErrorKind::TlsAlert
+    } else if message.contains("parse") {
+        FetchErrorKind::Parse
+    } else if message.contains("timed out") || message.contains("deadline has elapsed") {
+        FetchErrorKind::Timeout
+    } else if message.contains("eof") {
+        FetchErrorKind::EarlyEof
+    } else {
+        FetchErrorKind::Other
+    }
+}
+
+fn order_profiles(
+    strategy: &TlsFetchStrategy,
+    cache_key: Option<&ProfileCacheKey>,
+    now: Instant,
+) -> Vec<TlsFetchProfile> {
+    let mut ordered = if strategy.profiles.is_empty() {
+        vec![TlsFetchProfile::CompatTls12]
+    } else {
+        strategy.profiles.clone()
+    };
+
+    if strategy.profile_cache_ttl.is_zero() {
+        return ordered;
+    }
+
+    let Some(key) = cache_key else {
+        return ordered;
+    };
+
+    if let Some(cached) = profile_cache().get(key) {
+        let age = now.saturating_duration_since(cached.updated_at);
+        if age > strategy.profile_cache_ttl {
+            drop(cached);
+            profile_cache().remove(key);
+            return ordered;
+        }
+
+        if let Some(pos) = ordered.iter().position(|profile| *profile == cached.profile) {
+            if pos != 0 {
+                ordered.swap(0, pos);
+            }
+        }
+    }
+
+    ordered
+}
+
+fn remember_profile_success(
+    strategy: &TlsFetchStrategy,
+    cache_key: Option<ProfileCacheKey>,
+    profile: TlsFetchProfile,
+    now: Instant,
+) {
+    if strategy.profile_cache_ttl.is_zero() {
+        return;
+    }
+    let Some(key) = cache_key else {
+        return;
+    };
+    profile_cache().insert(
+        key,
+        ProfileCacheValue {
+            profile,
+            updated_at: now,
+        },
+    );
+}
+
 fn build_client_config() -> Arc<ClientConfig> {
     let root = rustls::RootCertStore::empty();
 
@@ -95,7 +289,114 @@ fn build_client_config() -> Arc<ClientConfig> {
     Arc::new(config)
 }
 
-fn build_client_hello(sni: &str, rng: &SecureRandom) -> Vec<u8> {
+fn deterministic_bytes(seed: &str, len: usize) -> Vec<u8> {
+    let mut out = Vec::with_capacity(len);
+    let mut counter: u32 = 0;
+    while out.len() < len {
+        let mut chunk_seed = Vec::with_capacity(seed.len() + std::mem::size_of::<u32>());
+        chunk_seed.extend_from_slice(seed.as_bytes());
+        chunk_seed.extend_from_slice(&counter.to_le_bytes());
+        out.extend_from_slice(&sha256(&chunk_seed));
+        counter = counter.wrapping_add(1);
+    }
+    out.truncate(len);
+    out
+}
+
+fn profile_cipher_suites(profile: TlsFetchProfile) -> &'static [u16] {
+    const MODERN_CHROME: &[u16] = &[
+        0x1301, 0x1302, 0x1303, 0xc02b, 0xc02c, 0xcca9, 0xc02f, 0xc030, 0xcca8, 0x009e, 0x00ff,
+    ];
+    const MODERN_FIREFOX: &[u16] = &[
+        0x1301, 0x1303, 0x1302, 0xc02b, 0xcca9, 0xc02c, 0xc02f, 0xcca8, 0xc030, 0x009e, 0x00ff,
+    ];
+    const COMPAT_TLS12: &[u16] = &[
+        0xc02b, 0xc02c, 0xc02f, 0xc030, 0xcca9, 0xcca8, 0x1301, 0x1302, 0x1303, 0x009e, 0x00ff,
+    ];
+    const LEGACY_MINIMAL: &[u16] = &[0xc02b, 0xc02f, 0x1301, 0x1302, 0x00ff];
+
+    match profile {
+        TlsFetchProfile::ModernChromeLike => MODERN_CHROME,
+        TlsFetchProfile::ModernFirefoxLike => MODERN_FIREFOX,
+        TlsFetchProfile::CompatTls12 => COMPAT_TLS12,
+        TlsFetchProfile::LegacyMinimal => LEGACY_MINIMAL,
+    }
+}
+
+fn profile_groups(profile: TlsFetchProfile) -> &'static [u16] {
+    const MODERN: &[u16] = &[0x001d, 0x0017, 0x0018]; // x25519, secp256r1, secp384r1
+    const COMPAT: &[u16] = &[0x001d, 0x0017];
+    const LEGACY: &[u16] = &[0x0017];
+
+    match profile {
+        TlsFetchProfile::ModernChromeLike | TlsFetchProfile::ModernFirefoxLike => MODERN,
+        TlsFetchProfile::CompatTls12 => COMPAT,
+        TlsFetchProfile::LegacyMinimal => LEGACY,
+    }
+}
+
+fn profile_sig_algs(profile: TlsFetchProfile) -> &'static [u16] {
+    const MODERN: &[u16] = &[0x0804, 0x0805, 0x0403, 0x0503, 0x0806];
+    const COMPAT: &[u16] = &[0x0403, 0x0503, 0x0804, 0x0805];
+    const LEGACY: &[u16] = &[0x0403, 0x0804];
+
+    match profile {
+        TlsFetchProfile::ModernChromeLike | TlsFetchProfile::ModernFirefoxLike => MODERN,
+        TlsFetchProfile::CompatTls12 => COMPAT,
+        TlsFetchProfile::LegacyMinimal => LEGACY,
+    }
+}
+
+fn profile_alpn(profile: TlsFetchProfile) -> &'static [&'static [u8]] {
+    const H2_HTTP11: &[&[u8]] = &[b"h2", b"http/1.1"];
+    const HTTP11: &[&[u8]] = &[b"http/1.1"];
+    match profile {
+        TlsFetchProfile::ModernChromeLike | TlsFetchProfile::ModernFirefoxLike => H2_HTTP11,
+        TlsFetchProfile::CompatTls12 | TlsFetchProfile::LegacyMinimal => HTTP11,
+    }
+}
+
+fn profile_supported_versions(profile: TlsFetchProfile) -> &'static [u16] {
+    const MODERN: &[u16] = &[0x0304, 0x0303];
+    const COMPAT: &[u16] = &[0x0303, 0x0304];
+    const LEGACY: &[u16] = &[0x0303];
+    match profile {
+        TlsFetchProfile::ModernChromeLike | TlsFetchProfile::ModernFirefoxLike => MODERN,
+        TlsFetchProfile::CompatTls12 => COMPAT,
+        TlsFetchProfile::LegacyMinimal => LEGACY,
+    }
+}
+
+fn profile_padding_target(profile: TlsFetchProfile) -> usize {
+    match profile {
+        TlsFetchProfile::ModernChromeLike => 220,
+        TlsFetchProfile::ModernFirefoxLike => 200,
+        TlsFetchProfile::CompatTls12 => 180,
+        TlsFetchProfile::LegacyMinimal => 64,
+    }
+}
+
+fn grease_value(rng: &SecureRandom, deterministic: bool, seed: &str) -> u16 {
+    const GREASE_VALUES: [u16; 16] = [
+        0x0a0a, 0x1a1a, 0x2a2a, 0x3a3a, 0x4a4a, 0x5a5a, 0x6a6a, 0x7a7a, 0x8a8a, 0x9a9a, 0xaaaa,
+        0xbaba, 0xcaca, 0xdada, 0xeaea, 0xfafa,
+    ];
+    if deterministic {
+        let idx = deterministic_bytes(seed, 1)[0] as usize % GREASE_VALUES.len();
+        GREASE_VALUES[idx]
+    } else {
+        let idx = (rng.bytes(1)[0] as usize) % GREASE_VALUES.len();
+        GREASE_VALUES[idx]
+    }
+}
+
+fn build_client_hello(
+    sni: &str,
+    rng: &SecureRandom,
+    profile: TlsFetchProfile,
+    grease_enabled: bool,
+    deterministic: bool,
+) -> Vec<u8> {
     // === ClientHello body ===
     let mut body = Vec::new();
 
@@ -103,29 +404,20 @@ fn build_client_hello(sni: &str, rng: &SecureRandom) -> Vec<u8> {
     body.extend_from_slice(&[0x03, 0x03]);
 
     // Random
-    body.extend_from_slice(&rng.bytes(32));
+    if deterministic {
+        body.extend_from_slice(&deterministic_bytes(&format!("tls-fetch-random:{sni}"), 32));
+    } else {
+        body.extend_from_slice(&rng.bytes(32));
+    }
 
     // Session ID: empty
     body.push(0);
 
-    // Cipher suites:
+    let mut cipher_suites = profile_cipher_suites(profile).to_vec();
-    // - TLS1.3 set
+    if grease_enabled {
-    // - broad TLS1.2 ECDHE set for RSA/ECDSA cert chains
+        let grease = grease_value(rng, deterministic, &format!("cipher:{sni}"));
-    // This keeps raw probing compatible with common production frontends that
+        cipher_suites.insert(0, grease);
-    // still negotiate TLS1.2.
+    }
-    let cipher_suites: [u16; 11] = [
-        0x1301, // TLS_AES_128_GCM_SHA256
-        0x1302, // TLS_AES_256_GCM_SHA384
-        0x1303, // TLS_CHACHA20_POLY1305_SHA256
-        0xc02b, // TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256
-        0xc02c, // TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384
-        0xcca9, // TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305_SHA256
-        0xc02f, // TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256
-        0xc030, // TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384
-        0xcca8, // TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305_SHA256
-        0x009e, // TLS_DHE_RSA_WITH_AES_128_GCM_SHA256
-        0x00ff, // TLS_EMPTY_RENEGOTIATION_INFO_SCSV
-    ];
     body.extend_from_slice(&((cipher_suites.len() * 2) as u16).to_be_bytes());
     for suite in cipher_suites {
         body.extend_from_slice(&suite.to_be_bytes());
@@ -150,7 +442,11 @@ fn build_client_hello(sni: &str, rng: &SecureRandom) -> Vec<u8> {
     exts.extend_from_slice(&sni_ext);
 
     // supported_groups
-    let groups: [u16; 2] = [0x001d, 0x0017]; // x25519, secp256r1
+    let mut groups = profile_groups(profile).to_vec();
+    if grease_enabled {
+        let grease = grease_value(rng, deterministic, &format!("group:{sni}"));
+        groups.insert(0, grease);
+    }
     exts.extend_from_slice(&0x000au16.to_be_bytes());
     exts.extend_from_slice(&((2 + groups.len() * 2) as u16).to_be_bytes());
     exts.extend_from_slice(&(groups.len() as u16 * 2).to_be_bytes());
@@ -159,7 +455,11 @@ fn build_client_hello(sni: &str, rng: &SecureRandom) -> Vec<u8> {
     }
 
     // signature_algorithms
-    let sig_algs: [u16; 4] = [0x0804, 0x0805, 0x0403, 0x0503]; // rsa_pss_rsae_sha256/384, ecdsa_secp256r1_sha256, ecdsa_secp384r1_sha384
+    let mut sig_algs = profile_sig_algs(profile).to_vec();
+    if grease_enabled {
+        let grease = grease_value(rng, deterministic, &format!("sigalg:{sni}"));
+        sig_algs.insert(0, grease);
+    }
     exts.extend_from_slice(&0x000du16.to_be_bytes());
     exts.extend_from_slice(&((2 + sig_algs.len() * 2) as u16).to_be_bytes());
     exts.extend_from_slice(&(sig_algs.len() as u16 * 2).to_be_bytes());
@@ -167,8 +467,12 @@ fn build_client_hello(sni: &str, rng: &SecureRandom) -> Vec<u8> {
         exts.extend_from_slice(&a.to_be_bytes());
     }
 
-    // supported_versions (TLS1.3 + TLS1.2)
+    // supported_versions
-    let versions: [u16; 2] = [0x0304, 0x0303];
+    let mut versions = profile_supported_versions(profile).to_vec();
+    if grease_enabled {
+        let grease = grease_value(rng, deterministic, &format!("version:{sni}"));
+        versions.insert(0, grease);
+    }
     exts.extend_from_slice(&0x002bu16.to_be_bytes());
     exts.extend_from_slice(&((1 + versions.len() * 2) as u16).to_be_bytes());
     exts.push((versions.len() * 2) as u8);
@@ -177,7 +481,14 @@ fn build_client_hello(sni: &str, rng: &SecureRandom) -> Vec<u8> {
     }
 
     // key_share (x25519)
-    let key = gen_key_share(rng);
+    let key = if deterministic {
+        let det = deterministic_bytes(&format!("keyshare:{sni}"), 32);
+        let mut key = [0u8; 32];
+        key.copy_from_slice(&det);
+        key
+    } else {
+        gen_key_share(rng)
+    };
     let mut keyshare = Vec::with_capacity(4 + key.len());
     keyshare.extend_from_slice(&0x001du16.to_be_bytes()); // group
     keyshare.extend_from_slice(&(key.len() as u16).to_be_bytes());
@@ -187,18 +498,29 @@ fn build_client_hello(sni: &str, rng: &SecureRandom) -> Vec<u8> {
     exts.extend_from_slice(&(keyshare.len() as u16).to_be_bytes());
     exts.extend_from_slice(&keyshare);
 
-    // ALPN (http/1.1)
+    // ALPN
-    let alpn_proto = b"http/1.1";
+    let mut alpn_list = Vec::new();
-    exts.extend_from_slice(&0x0010u16.to_be_bytes());
+    for proto in profile_alpn(profile) {
-    exts.extend_from_slice(&((2 + 1 + alpn_proto.len()) as u16).to_be_bytes());
+        alpn_list.push(proto.len() as u8);
-    exts.extend_from_slice(&((1 + alpn_proto.len()) as u16).to_be_bytes());
+        alpn_list.extend_from_slice(proto);
-    exts.push(alpn_proto.len() as u8);
+    }
-    exts.extend_from_slice(alpn_proto);
+    if !alpn_list.is_empty() {
+        exts.extend_from_slice(&0x0010u16.to_be_bytes());
+        exts.extend_from_slice(&((2 + alpn_list.len()) as u16).to_be_bytes());
+        exts.extend_from_slice(&(alpn_list.len() as u16).to_be_bytes());
+        exts.extend_from_slice(&alpn_list);
+    }
+
+    if grease_enabled {
+        let grease = grease_value(rng, deterministic, &format!("ext:{sni}"));
+        exts.extend_from_slice(&grease.to_be_bytes());
+        exts.extend_from_slice(&0u16.to_be_bytes());
+    }
 
     // padding to reduce recognizability and keep length ~500 bytes
-    const TARGET_EXT_LEN: usize = 180;
+    let target_ext_len = profile_padding_target(profile);
-    if exts.len() < TARGET_EXT_LEN {
+    if exts.len() < target_ext_len {
-        let remaining = TARGET_EXT_LEN - exts.len();
+        let remaining = target_ext_len - exts.len();
         if remaining > 4 {
             let pad_len = remaining - 4; // minus type+len
             exts.extend_from_slice(&0x0015u16.to_be_bytes()); // padding extension
@@ -414,27 +736,41 @@ async fn connect_tcp_with_upstream(
     connect_timeout: Duration,
     upstream: Option<std::sync::Arc<crate::transport::UpstreamManager>>,
     scope: Option<&str>,
+    strict_route: bool,
 ) -> Result<UpstreamStream> {
     if let Some(manager) = upstream {
-        if let Some(addr) = resolve_socket_addr(host, port) {
+        let resolved = if let Some(addr) = resolve_socket_addr(host, port) {
-            match manager.connect(addr, None, scope).await {
+            Some(addr)
-                Ok(stream) => return Ok(stream),
+        } else {
-                Err(e) => {
+            match tokio::net::lookup_host((host, port)).await {
-                    warn!(
+                Ok(mut addrs) => addrs.find(|a| a.is_ipv4()),
-                        host = %host,
+                Err(e) => {
-                        port = port,
+                    if strict_route {
-                        scope = ?scope,
+                        return Err(anyhow!(
-                        error = %e,
+                            "upstream route DNS resolution failed for {host}:{port}: {e}"
-                        "Upstream connect failed, using direct connect"
+                        ));
-                    );
+                    }
-                }
+                    warn!(
-            }
+                        host = %host,
-        } else if let Ok(mut addrs) = tokio::net::lookup_host((host, port)).await
+                        port = port,
-            && let Some(addr) = addrs.find(|a| a.is_ipv4())
+                        scope = ?scope,
-        {
+                        error = %e,
+                        "Upstream DNS resolution failed, using direct connect"
+                    );
+                    None
+                }
+            }
+        };
+
+        if let Some(addr) = resolved {
             match manager.connect(addr, None, scope).await {
                 Ok(stream) => return Ok(stream),
                 Err(e) => {
+                    if strict_route {
+                        return Err(anyhow!(
+                            "upstream route connect failed for {host}:{port}: {e}"
+                        ));
+                    }
                     warn!(
                         host = %host,
                         port = port,
@@ -444,6 +780,10 @@ async fn connect_tcp_with_upstream(
                     );
                 }
             }
+        } else if strict_route {
+            return Err(anyhow!(
+                "upstream route resolution produced no usable address for {host}:{port}"
+            ));
         }
     }
     Ok(UpstreamStream::Tcp(
@@ -483,12 +823,15 @@ async fn fetch_via_raw_tls_stream<S>(
     sni: &str,
     connect_timeout: Duration,
     proxy_protocol: u8,
+    profile: TlsFetchProfile,
+    grease_enabled: bool,
+    deterministic: bool,
 ) -> Result<TlsFetchResult>
 where
     S: AsyncRead + AsyncWrite + Unpin,
 {
     let rng = SecureRandom::new();
-    let client_hello = build_client_hello(sni, &rng);
+    let client_hello = build_client_hello(sni, &rng, profile, grease_enabled, deterministic);
     timeout(connect_timeout, async {
         if proxy_protocol > 0 {
             let header = match proxy_protocol {
@@ -562,6 +905,10 @@ async fn fetch_via_raw_tls(
     scope: Option<&str>,
     proxy_protocol: u8,
     unix_sock: Option<&str>,
+    strict_route: bool,
+    profile: TlsFetchProfile,
+    grease_enabled: bool,
+    deterministic: bool,
 ) -> Result<TlsFetchResult> {
     #[cfg(unix)]
     if let Some(sock_path) = unix_sock {
@@ -572,8 +919,16 @@ async fn fetch_via_raw_tls(
                     sock = %sock_path,
                     "Raw TLS fetch using mask unix socket"
                 );
-                return fetch_via_raw_tls_stream(stream, sni, connect_timeout, proxy_protocol)
+                return fetch_via_raw_tls_stream(
-                    .await;
+                    stream,
+                    sni,
+                    connect_timeout,
+                    proxy_protocol,
+                    profile,
+                    grease_enabled,
+                    deterministic,
+                )
+                .await;
             }
             Ok(Err(e)) => {
                 warn!(
@@ -596,8 +951,25 @@ async fn fetch_via_raw_tls(
     #[cfg(not(unix))]
     let _ = unix_sock;
 
-    let stream = connect_tcp_with_upstream(host, port, connect_timeout, upstream, scope).await?;
+    let stream = connect_tcp_with_upstream(
-    fetch_via_raw_tls_stream(stream, sni, connect_timeout, proxy_protocol).await
+        host,
+        port,
+        connect_timeout,
+        upstream,
+        scope,
+        strict_route,
+    )
+    .await?;
+    fetch_via_raw_tls_stream(
+        stream,
+        sni,
+        connect_timeout,
+        proxy_protocol,
+        profile,
+        grease_enabled,
+        deterministic,
+    )
+    .await
 }
 
 async fn fetch_via_rustls_stream<S>(
@@ -703,6 +1075,7 @@ async fn fetch_via_rustls(
     scope: Option<&str>,
     proxy_protocol: u8,
     unix_sock: Option<&str>,
+    strict_route: bool,
 ) -> Result<TlsFetchResult> {
     #[cfg(unix)]
     if let Some(sock_path) = unix_sock {
@@ -736,16 +1109,159 @@ async fn fetch_via_rustls(
     #[cfg(not(unix))]
     let _ = unix_sock;
 
-    let stream = connect_tcp_with_upstream(host, port, connect_timeout, upstream, scope).await?;
+    let stream = connect_tcp_with_upstream(
+        host,
+        port,
+        connect_timeout,
+        upstream,
+        scope,
+        strict_route,
+    )
+    .await?;
     fetch_via_rustls_stream(stream, host, sni, proxy_protocol).await
 }
 
-/// Fetch real TLS metadata for the given SNI.
+/// Fetch real TLS metadata with an adaptive multi-profile strategy.
-///
+pub async fn fetch_real_tls_with_strategy(
-/// Strategy:
+    host: &str,
-/// 1) Probe raw TLS for realistic ServerHello and ApplicationData record sizes.
+    port: u16,
-/// 2) Fetch certificate chain via rustls to build cert payload.
+    sni: &str,
-/// 3) Merge both when possible; otherwise auto-fallback to whichever succeeded.
+    strategy: &TlsFetchStrategy,
+    upstream: Option<std::sync::Arc<crate::transport::UpstreamManager>>,
+    scope: Option<&str>,
+    proxy_protocol: u8,
+    unix_sock: Option<&str>,
+) -> Result<TlsFetchResult> {
+    let attempt_timeout = strategy.attempt_timeout.max(Duration::from_millis(1));
+    let total_budget = strategy.total_budget.max(Duration::from_millis(1));
+    let started_at = Instant::now();
+    let cache_key = profile_cache_key(
+        host,
+        port,
+        sni,
+        upstream.as_ref(),
+        scope,
+        proxy_protocol,
+        unix_sock,
+    );
+    let profiles = order_profiles(strategy, Some(&cache_key), started_at);
+
+    let mut raw_result = None;
+    let mut raw_last_error: Option<anyhow::Error> = None;
+    let mut raw_last_error_kind = FetchErrorKind::Other;
+    let mut selected_profile = None;
+
+    for profile in profiles {
+        let elapsed = started_at.elapsed();
+        if elapsed >= total_budget {
+            break;
+        }
+        let timeout_for_attempt = attempt_timeout.min(total_budget - elapsed);
+
+        match fetch_via_raw_tls(
+            host,
+            port,
+            sni,
+            timeout_for_attempt,
+            upstream.clone(),
+            scope,
+            proxy_protocol,
+            unix_sock,
+            strategy.strict_route,
+            profile,
+            strategy.grease_enabled,
+            strategy.deterministic,
+        )
+        .await
+        {
+            Ok(res) => {
+                selected_profile = Some(profile);
+                raw_result = Some(res);
+                break;
+            }
+            Err(err) => {
+                let kind = classify_fetch_error(&err);
+                warn!(
+                    sni = %sni,
+                    profile = profile.as_str(),
+                    error_kind = ?kind,
+                    error = %err,
+                    "Raw TLS fetch attempt failed"
+                );
+                raw_last_error_kind = kind;
+                raw_last_error = Some(err);
+                if strategy.strict_route && matches!(kind, FetchErrorKind::Route) {
+                    break;
+                }
+            }
+        }
+    }
+
+    if let Some(profile) = selected_profile {
+        remember_profile_success(strategy, Some(cache_key), profile, Instant::now());
+    }
+
+    if raw_result.is_none()
+        && strategy.strict_route
+        && matches!(raw_last_error_kind, FetchErrorKind::Route)
+    {
+        if let Some(err) = raw_last_error {
+            return Err(err);
+        }
+        return Err(anyhow!("TLS fetch strict-route failure"));
+    }
+
+    let elapsed = started_at.elapsed();
+    if elapsed >= total_budget {
+        return match raw_result {
+            Some(raw) => Ok(raw),
+            None => Err(raw_last_error.unwrap_or_else(|| anyhow!("TLS fetch total budget exhausted"))),
+        };
+    }
+
+    let rustls_timeout = attempt_timeout.min(total_budget - elapsed);
+    let rustls_result = fetch_via_rustls(
+        host,
+        port,
+        sni,
+        rustls_timeout,
+        upstream,
+        scope,
+        proxy_protocol,
+        unix_sock,
+        strategy.strict_route,
+    )
+    .await;
+
+    match rustls_result {
+        Ok(rustls) => {
+            if let Some(mut raw) = raw_result {
+                raw.cert_info = rustls.cert_info;
+                raw.cert_payload = rustls.cert_payload;
+                raw.behavior_profile.source = TlsProfileSource::Merged;
+                debug!(sni = %sni, "Fetched TLS metadata via adaptive raw probe + rustls cert chain");
+                Ok(raw)
+            } else {
+                Ok(rustls)
+            }
+        }
+        Err(err) => {
+            if let Some(raw) = raw_result {
+                warn!(sni = %sni, error = %err, "Rustls cert fetch failed, using raw TLS metadata only");
+                Ok(raw)
+            } else if let Some(raw_err) = raw_last_error {
+                Err(anyhow!(
+                    "TLS fetch failed (raw: {raw_err}; rustls: {err})"
+                ))
+            } else {
+                Err(err)
+            }
+        }
+    }
+}
+
+/// Fetch real TLS metadata for the given SNI using a single-attempt compatibility strategy.
+#[allow(dead_code)]
 pub async fn fetch_real_tls(
     host: &str,
     port: u16,
@@ -756,62 +1272,30 @@ pub async fn fetch_real_tls(
     proxy_protocol: u8,
     unix_sock: Option<&str>,
 ) -> Result<TlsFetchResult> {
-    let raw_result = match fetch_via_raw_tls(
+    let strategy = TlsFetchStrategy::single_attempt(connect_timeout);
+    fetch_real_tls_with_strategy(
         host,
         port,
         sni,
-        connect_timeout,
+        &strategy,
-        upstream.clone(),
-        scope,
-        proxy_protocol,
-        unix_sock,
-    )
-    .await
-    {
-        Ok(res) => Some(res),
-        Err(e) => {
-            warn!(sni = %sni, error = %e, "Raw TLS fetch failed");
-            None
-        }
-    };
-
-    match fetch_via_rustls(
-        host,
-        port,
-        sni,
-        connect_timeout,
         upstream,
         scope,
         proxy_protocol,
         unix_sock,
     )
     .await
-    {
-        Ok(rustls_result) => {
-            if let Some(mut raw) = raw_result {
-                raw.cert_info = rustls_result.cert_info;
-                raw.cert_payload = rustls_result.cert_payload;
-                raw.behavior_profile.source = TlsProfileSource::Merged;
-                debug!(sni = %sni, "Fetched TLS metadata via raw probe + rustls cert chain");
-                Ok(raw)
-            } else {
-                Ok(rustls_result)
-            }
-        }
-        Err(e) => {
-            if let Some(raw) = raw_result {
-                warn!(sni = %sni, error = %e, "Rustls cert fetch failed, using raw TLS metadata only");
-                Ok(raw)
-            } else {
-                Err(e)
-            }
-        }
-    }
 }
 
 #[cfg(test)]
 mod tests {
-    use super::{derive_behavior_profile, encode_tls13_certificate_message};
+    use std::time::{Duration, Instant};
+
+    use super::{
+        ProfileCacheValue, TlsFetchStrategy, build_client_hello, derive_behavior_profile,
+        encode_tls13_certificate_message, order_profiles, profile_cache, profile_cache_key,
+    };
+    use crate::config::TlsFetchProfile;
+    use crate::crypto::SecureRandom;
     use crate::protocol::constants::{
         TLS_RECORD_APPLICATION, TLS_RECORD_CHANGE_CIPHER, TLS_RECORD_HANDSHAKE,
     };
@@ -860,4 +1344,89 @@ mod tests {
         assert_eq!(profile.ticket_record_sizes, vec![220, 180]);
         assert_eq!(profile.source, TlsProfileSource::Raw);
     }
+
+    #[test]
+    fn test_order_profiles_prioritizes_fresh_cached_winner() {
+        let strategy = TlsFetchStrategy {
+            profiles: vec![
+                TlsFetchProfile::ModernChromeLike,
+                TlsFetchProfile::CompatTls12,
+                TlsFetchProfile::LegacyMinimal,
+            ],
+            strict_route: true,
+            attempt_timeout: Duration::from_secs(1),
+            total_budget: Duration::from_secs(2),
+            grease_enabled: false,
+            deterministic: false,
+            profile_cache_ttl: Duration::from_secs(60),
+        };
+        let cache_key = profile_cache_key(
+            "mask.example",
+            443,
+            "tls.example",
+            None,
+            Some("tls"),
+            0,
+            None,
+        );
+        profile_cache().remove(&cache_key);
+        profile_cache().insert(
+            cache_key.clone(),
+            ProfileCacheValue {
+                profile: TlsFetchProfile::CompatTls12,
+                updated_at: Instant::now(),
+            },
+        );
+
+        let ordered = order_profiles(&strategy, Some(&cache_key), Instant::now());
+        assert_eq!(ordered[0], TlsFetchProfile::CompatTls12);
+        profile_cache().remove(&cache_key);
+    }
+
+    #[test]
+    fn test_order_profiles_drops_expired_cached_winner() {
+        let strategy = TlsFetchStrategy {
+            profiles: vec![TlsFetchProfile::ModernFirefoxLike, TlsFetchProfile::CompatTls12],
+            strict_route: true,
+            attempt_timeout: Duration::from_secs(1),
+            total_budget: Duration::from_secs(2),
+            grease_enabled: false,
+            deterministic: false,
+            profile_cache_ttl: Duration::from_secs(5),
+        };
+        let cache_key = profile_cache_key("mask2.example", 443, "tls2.example", None, None, 0, None);
+        profile_cache().remove(&cache_key);
+        profile_cache().insert(
+            cache_key.clone(),
+            ProfileCacheValue {
+                profile: TlsFetchProfile::CompatTls12,
+                updated_at: Instant::now() - Duration::from_secs(6),
+            },
+        );
+
+        let ordered = order_profiles(&strategy, Some(&cache_key), Instant::now());
+        assert_eq!(ordered[0], TlsFetchProfile::ModernFirefoxLike);
+        assert!(profile_cache().get(&cache_key).is_none());
+    }
+
+    #[test]
+    fn test_deterministic_client_hello_is_stable() {
+        let rng = SecureRandom::new();
+        let first = build_client_hello(
+            "stable.example",
+            &rng,
+            TlsFetchProfile::ModernChromeLike,
+            true,
+            true,
+        );
+        let second = build_client_hello(
+            "stable.example",
+            &rng,
+            TlsFetchProfile::ModernChromeLike,
+            true,
+            true,
+        );
+
+        assert_eq!(first, second);
+    }
 }