Stealth, TLS Fingerprints, and Diagnostics

This page is the single source of truth for stygian-browser anti-detection behavior. It consolidates browser stealth, TLS fingerprint control, and runtime verification.

Optimal stealth profiles

stygian-browser now provides two reusable high-stealth constructors:

1. BrowserConfig::stealth_profile_without_proxy()
2. BrowserConfig::stealth_profile_with_proxy(proxy_url)

Direct integration without proxy

use stygian_browser::{BrowserConfig, BrowserPool};

let config = BrowserConfig::stealth_profile_without_proxy();
let pool = BrowserPool::new(config).await?;

Direct integration with proxy

use stygian_browser::{BrowserConfig, BrowserPool};

let config = BrowserConfig::stealth_profile_with_proxy("http://user:pass@proxy:8080");
let pool = BrowserPool::new(config).await?;

What these profiles set

Both profiles set:

1. StealthLevel::Advanced
2. HeadlessMode::New
3. CdpFixMode::AddBinding
4. Default noise stack enabled
5. Weighted coherent fingerprint profile

Difference:

1. No-proxy profile uses WebRtcPolicy::BlockAll
2. Proxy profile uses WebRtcPolicy::DisableNonProxied

Preset matrix

Operational guidance:

1. Start with the profile that matches your network path (proxy vs non-proxy).
2. If pages fail due to RTC features, prefer the proxy profile over weakening non-proxy settings.
3. Keep CdpFixMode::AddBinding and HeadlessMode::New unchanged unless you have a compatibility break you can reproduce.
4. Validate each target with verify_stealth_with_transport() after navigation.

MCP usage caveat

For browser_acquire, optional fields like stealth_level, webrtc_policy, cdp_fix_mode, tls_profile, and proxy are metadata labels for session attribution and response echoing. They do not reconfigure an already pooled browser instance at runtime.

To get true max-stealth behavior through MCP, start the MCP server with a BrowserPool already configured using one of the profile constructors above.

Example server boot (non-proxy):

use stygian_browser::{BrowserConfig, BrowserPool};
use stygian_browser::mcp::McpBrowserServer;

let pool = BrowserPool::new(BrowserConfig::stealth_profile_without_proxy()).await?;
McpBrowserServer::new(pool).run().await?;

Example server boot (proxy):

use stygian_browser::{BrowserConfig, BrowserPool};
use stygian_browser::mcp::McpBrowserServer;

let pool = BrowserPool::new(BrowserConfig::stealth_profile_with_proxy("http://user:pass@proxy:8080")).await?;
McpBrowserServer::new(pool).run().await?;

Stealth levels

Notes:

1. Basic uses minimal navigator spoof plus CDP mitigation.
2. Advanced enables the full injection stack in apply_stealth_to_page.
3. The human behavior APIs are available, but are not automatically injected by apply_stealth_to_page.

What advanced actually injects

When stealth_level is advanced, stygian-browser injects the following at new-document time:

1. CDP hardening script.
2. CDP protection script (mode-driven).
3. Navigator spoof script.
4. Fingerprint script.
5. WebRTC script.
6. Canvas noise.
7. WebGL noise.
8. Audio noise.
9. Rects/TextMetrics noise.
10. Navigator coherence script.
11. Timing noise.
12. Peripheral stealth script.

Headless mode

Use HeadlessMode::New unless you are forced onto old Chromium builds.

use stygian_browser::{BrowserConfig, HeadlessMode};

let cfg = BrowserConfig::builder()
    .headless_mode(HeadlessMode::New)
    .build();

Environment override:

STYGIAN_HEADLESS_MODE=new cargo run

CDP leak mitigation

Set via BrowserConfig::cdp_fix_mode or STYGIAN_CDP_FIX_MODE.

WebRTC policy

Set via BrowserConfig::webrtc.

For highest non-proxy stealth, prefer block_all unless target compatibility requires otherwise.

Fingerprint coherence

Advanced mode derives identity from one coherent profile per browser instance. If you do not set fingerprint_profile explicitly, a weighted fallback profile is chosen.

Current weighted fallback mapping:

1. Windows: 65%
2. macOS: 20%
3. Linux: 5%
4. Android: 10%

TLS fingerprint control

TLS fingerprint control is orthogonal to browser JS stealth and requires feature tls-config. Use it for HTTP clients where JA3/JA4 consistency matters.

Built-in profiles:

1. CHROME_131
2. FIREFOX_133
3. SAFARI_18
4. EDGE_131

use stygian_browser::tls::{build_profiled_client, CHROME_131};

let client = build_profiled_client(&CHROME_131, None)?;
let response = client.get("https://example.com").send().await?;

For browser contexts, chrome_tls_args can constrain TLS version behavior, but exact Chrome cipher ordering remains tied to the browser binary.

JA4Q — QUIC Initial Packet fingerprint

stygian_browser::tls::Ja4q mirrors the existing Ja4 (TLS ClientHello) fingerprint for the QUIC Initial packet, per the JA4+ spec Cloudflare has begun collecting. TlsProfile::ja4q() returns family-default reference values for supported browser families:

Ja4q::from_components(...) builds a fingerprint from raw QUIC Initial components for cases where you have a live packet capture and want to verify against the reference values.

Bind the axes — TlsProfilePack

The UA, TLS ClientHello (JA3/JA4), HTTP/2 SETTINGS frame, and HTTP/3 perk are not four independent knobs — they are bound together at the type level into a TlsProfilePack. Mixing Chrome's UA with Firefox's TLS fingerprint (or with Safari's H2 SETTINGS) produces a profile no real browser will ever emit, and a careful detector suite will flag the mismatch faster than a silent request would be.

The TlsProfile enum carries all four axes together. Picking one profile gives you the matching UA, TLS handshake, H2 SETTINGS, and H3 perk in a single value — there's no way to assemble a mixed profile by accident. This is the Web Scraping Guide §Innovation pattern: the binding is enforced by the type system, not by convention.

Diagnostic hints — runtime configuration warnings

BrowserConfig::diagnostic_hints() returns a list of non-fatal DiagnosticHints that surface structural incompatibilities between configuration choices at runtime. Unlike BrowserConfig::validate(), hints never block the browser from launching — they exist so the existing browser_stealth_check MCP tool can report them to the caller before the first request goes out.

Currently emitted hint:

Hints are advisory. The browser will still launch and the proxy will still be used — but the operator will know that the H3 preference is not being honored. This closes the gap where a misconfigured prefer_h3 would have been silently ignored.

Runtime stealth diagnostics

Run diagnostics from a live page handle:

let report = page.verify_stealth().await?;
let report_with_transport = page.verify_stealth_with_transport(None).await?;

DiagnosticReport includes:

1. checks
2. passed_count
3. failed_count
4. known_limitations
5. transport

There are currently 25 built-in JS checks.

Known limitation probes currently include:

1. WebGPU surface exposure
2. performance.memory exposure

Treat known_limitations as visible surfaces not yet fully spoofed/validated.

Detection vectors covered

Human interaction APIs

These are available as explicit APIs and MCP interaction controls.

1. MouseSimulator
2. TypingSimulator
3. InteractionSimulator
4. RequestPacer

Use them when the target expects user-like interaction cadence. They are not automatically invoked by apply_stealth_to_page.

Cloudflare Turnstile reality check

1. Invisible/non-interactive modes are primarily fingerprint-driven.
2. Managed mode may require explicit user interaction and cannot be bypassed solely by improving fingerprint quality.

For managed flows, rely on sanctioned session bootstrap methods such as prior trusted clearance state, human-in-the-loop, or site-approved challenge workflows.