Stealth Agent Browser

stealth-agent-browser-mcp

A Model Context Protocol (MCP) server that gives AI agents a stealth-grade Chromium browser with a hybrid Accessibility-Object-Model + Set-of-Mark vision interface. Built for Claude, works with any MCP-compatible host.

• Stealth first. Uses rebrowser-playwright to patch the Runtime.Enable CDP leak that bypasses playwright-extra-class stealth plugins. Passes modern bot-detection suites (CreepJS, bot.sannysoft.com) where vanilla Playwright fails.
• Token-lean by default. browser_snapshot returns Playwright aria snapshot YAML (~2–5 KB) instead of raw HTML (100KB+). Every interactive element carries a [ref=eN] id that actions consume directly — no selectors, no drift.
• Hybrid vision when it matters. Ask for mode: "hybrid" and the server overlays numbered red boxes on the screenshot so the model can ground visually (Set-of-Mark prompting, Yang et al.). The ref ids on the image match the ids in the YAML. No parallel numbering scheme to go out of sync.
• Readability-based content extraction. browser_scroll_read runs Mozilla Readability through JSDOM and returns clean Markdown — optionally delta-only, so re-reads cost nothing when nothing changed.
• Proxy-ready. Per-session proxy auth, useful with residential pools.

Authorized use only. Stealth tooling has legitimate applications (accessibility auditing, your-own-account automation, QA against sites you own or have permission to test). Do not use this server to violate a site's terms of service or applicable law. See SECURITY.md.

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Install

npm install -g stealth-agent-browser-mcp
# Chromium binary is fetched automatically on first launch
npx playwright-core install chromium

Or run without install via npx stealth-agent-browser-mcp.

Quickstart (Claude Desktop / Claude Code / Cursor)

Add to your MCP config:

{
  "mcpServers": {
    "stealth-browser": {
      "command": "npx",
      "args": ["-y", "stealth-agent-browser-mcp"],
      "env": {
        "SAB_HEADLESS": "true",
        "SAB_STEALTH_LEVEL": "patched"
      }
    }
  }
}

Restart the host. The agent will see the tools listed below.

Tools

Tool	Purpose
browser_navigate	Navigate a URL and return a snapshot.
browser_snapshot	aom (YAML only, cheapest), vision (raw screenshot), or hybrid (YAML + Set-of-Mark screenshot).
browser_click	Click an element by its [ref=eN].
browser_type	Type into an input/textarea by ref.
browser_select	Choose options in a <select> by ref.
browser_scroll_read	Scroll and return Readability Markdown (delta-only by default).
browser_wait_for	Wait for text or a ref to become visible.
browser_tabs	list / new / close / switch.
browser_eval	Evaluate a JS expression in the page's MAIN world; JSON result.
browser_set_proxy	Update single-proxy config (effective after browser_restart).
browser_set_proxy_pool	Replace residential proxy pool at runtime (effective after browser_restart).
browser_solve_captcha	Fallback captcha solver (CapSolver / 2Captcha). Detects Turnstile/hCaptcha/reCAPTCHA on the page.
browser_restart	Close + re-open the active browser session with current config.

All action tools are addressed by the ref emitted in the last AOM snapshot. Refs are Playwright's own aria-ref=eN ids — there is no parallel numbering scheme.

Configuration

All via environment variables:

Var	Default	Notes
SAB_HEADLESS	true	false for a visible window (debugging).
SAB_STEALTH_LEVEL	patched	off | patched | paranoid.
SAB_PROXY_SERVER	—	Single-proxy mode. e.g. http://host:port
SAB_PROXY_USERNAME / SAB_PROXY_PASSWORD	—
SAB_PROXY_POOL	—	Residential pool. Comma-separated URLs (http://u:p@host:port,...) or a JSON array of {server, username, password}.
SAB_PROXY_ROTATION	per-restart	per-session | per-restart | static.
SAB_PROXY_STICKY_TEMPLATE	—	Username template for sticky-IP providers. ${sessionId} interpolates. Example: brd-customer-c1-zone-res-session-${sessionId}.
SAB_HUMAN_MOUSE	true	Bezier-path click with pre-click hesitation. Defeats Datadome trajectory analysis.
SAB_CAPTCHA_PROVIDER	none	capsolver | twocaptcha | none.
SAB_CAPTCHA_API_KEY	—	Provider API key.
SAB_USER_DATA_DIR	—	Persistent profile directory (cookies build reputation).
SAB_DEFAULT_TIMEOUT_MS	15000	Per-action timeout.
SAB_MAX_ANNOTATED	75	Max labelled boxes in hybrid mode.
SAB_VIEWPORT_W / SAB_VIEWPORT_H	1366 / 768
SAB_LOCALE	en-US
SAB_TIMEZONE	America/New_York
LOG_LEVEL	info	debug, warn, etc. Always writes to stderr.

Architecture

src/
├── index.ts         # Entry (stdio)
├── server.ts        # MCP server + tool registration
├── tools.ts         # Tool handlers
├── browser.ts       # Stealth Chromium launcher (rebrowser-playwright)
├── session.ts       # Per-connection browser/context/page state
├── snapshot.ts      # AOM + Set-of-Mark pipeline
├── annotate.ts      # SVG overlay compositing (sharp)
├── reader.ts        # Readability → Markdown (pierces open shadow roots)
├── fingerprint.ts   # Rotatable UA/viewport/timezone profiles
├── proxy.ts         # Residential pool + rotation + sticky-session template
├── human-mouse.ts   # Bezier-curve cursor paths (ghost-cursor math)
├── captcha.ts       # CapSolver / 2Captcha REST adapters
├── config.ts        # Zod-validated env config
└── logger.ts        # pino → stderr (never stdout)

All logs go to stderr — stdout is reserved for JSON-RPC. Never add console.log.

TLS / JA3 fingerprint — why there is no Node-layer spoofer here

A common ask for scrapers is: "spoof the TLS ClientHello (JA3) to look like Chrome, via curl-impersonate or node-tls-client."

That applies to Node-layer HTTP scrapers (fetch, got, axios) where the TCP connection originates from Node's OpenSSL, which emits a ClientHello signature distinct from Chrome's BoringSSL — and Cloudflare / Akamai Bot Manager drop it at the network layer before a single byte of JavaScript runs.

This MCP does not have that architecture. Every request exits through Chromium. Chromium's TLS stack is Chrome's TLS stack (literally the same BoringSSL build), so the ClientHello JA3 is Chrome's JA3 by construction. No JS-level rewriting is possible or necessary.

The one place TLS can still betray you is if you route through a proxy that terminates and re-initiates TLS (MITM). Residential proxy providers (Bright Data, DataImpulse, Oxylabs residential, SOAX) route at TCP — they do not MITM TLS — and the Chromium handshake reaches the origin unmodified. The products that do MITM TLS are managed scraping browsers (Bright Data's Scraping Browser, Oxylabs Web Unblocker), which ship their own headless Chrome and replace this MCP rather than layering on top of it.

Bottom line: with rebrowser-playwright + residential pool (P1) + human mouse (P2), the TLS fingerprint, CDP runtime, DOM surface, and behavioral layer all match real Chrome. Captcha solving (P3) is a fallback for the 1–5% of sessions that still get flagged.

Benchmarks

npm run bench:stealth launches the configured browser against public bot-detection test pages (bot.sannysoft.com, CreepJS, pixelscan, BrowserLeaks WebRTC) and reports pass/fail. These are the same harnesses used by the rebrowser-patches and Patchright projects — see rebrowser-bot-detector for the reference suite.

Typical local-fixture test run (see test/):

Test	Result
AOM YAML contains refs for all interactive elements	✓
hybrid mode returns PNG + YAML, refs match	✓
click/type by ref produces expected DOM change	✓
Readability extracts article to Markdown	✓
Delta-only scroll returns (no readable content change) on repeat	✓

Comparison

	stealth-agent-browser-mcp	playwright-mcp	browser-use MCP	computer use
CDP-level stealth (Cloudflare/DataDome)	✓	✗	partial	✗
Accessibility-tree snapshots	✓	✓	✓	✗
Set-of-Mark vision (ref-labeled screenshot)	✓	✗	✗	pure vision
Readability-based scroll-and-read	✓	✗	✗	✗
Token-lean by default	✓	✓	✗	✗
Bundled agent loop	✗ (host's model drives)	✗	✓	✗

Development

npm install
npx playwright-core install chromium
npm run build
npm test

Contributing

See CONTRIBUTING.md. All contributions under Apache-2.0.

License

Apache-2.0