CloakBrowser

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cloakbrowser-mcp is a Model Context Protocol browser automation server that runs upstream @playwright/mcp with the CloakBrowser Chromium binary. It provides Playwright MCP-compatible tools through a thin CloakBrowser bridge for npm and Docker users over stdio or Streamable HTTP.

Documentation: swimmwatch.github.io/cloakbrowser-mcp

The server is intentionally thin:

• upstream Playwright MCP owns browser tool schemas, descriptions, and responses;
• this package generates a Playwright MCP config that points launchOptions.executablePath to CloakBrowser;
• the bridge exposes upstream tools unchanged;
• the only local tools are cloakbrowser_binary_info and cloakbrowser_bridge_info.

Version compatibility

cloakbrowser-mcp	@playwright/mcp	Playwright MCP Docker base	CloakBrowser	Node.js	Transport	Platform	Parity
1.2.5	^0.0.75	mcr.microsoft.com/playwright/mcp:v0.0.75	^0.3.30	>=20	stdio, Streamable HTTP	linux/amd64 Docker, Node.js local	Upstream default tools compared in CI.
1.2.3	^0.0.75	mcr.microsoft.com/playwright/mcp:v0.0.75	^0.3.30	>=20	stdio, Streamable HTTP	linux/amd64 Docker, Node.js local	Upstream default tools compared in CI.
1.2.2	^0.0.75	mcr.microsoft.com/playwright/mcp:v0.0.75	^0.3.30	>=20	stdio, Streamable HTTP	linux/amd64 Docker, Node.js local	Upstream default tools compared in CI.
1.2.1	^0.0.75	mcr.microsoft.com/playwright/mcp:v0.0.75	^0.3.30	>=20	stdio, Streamable HTTP	linux/amd64 Docker, Node.js local	Upstream default tools compared in CI.
1.2.0	^0.0.75	mcr.microsoft.com/playwright/mcp:v0.0.75	^0.3.30	>=20	stdio, Streamable HTTP	linux/amd64 Docker, Node.js local	Upstream default tools compared in CI.
1.1.0	^0.0.75	mcr.microsoft.com/playwright/mcp:v0.0.75	^0.3.30	>=20	stdio, Streamable HTTP	linux/amd64 Docker, Node.js local	Upstream default tools compared in CI.
1.0.2	^0.0.75	mcr.microsoft.com/playwright/mcp:v0.0.75	^0.3.30	>=20	stdio	linux/amd64 Docker, Node.js local	Upstream default tools compared in CI.
1.0.1	^0.0.75	mcr.microsoft.com/playwright/mcp:v0.0.75	^0.3.30	>=20	stdio	linux/amd64 Docker, Node.js local	Upstream default tools compared in CI.
1.0.0	^0.0.75	mcr.microsoft.com/playwright/mcp:v0.0.75	^0.3.30	>=20	stdio	linux/amd64 Docker, Node.js local	Upstream default tools compared in CI.

See Version Compatibility for the maintained compatibility table.

Run from npm

npx -y cloakbrowser-mcp@latest --help
npx -y cloakbrowser-mcp@latest
npx -y cloakbrowser-mcp@latest --transport streamable-http --http-port 3000

Requires Node.js 20 or newer. The first real browser action may download the CloakBrowser binary unless it is already cached. The default transport is stdio. Streamable HTTP binds to 127.0.0.1 by default and serves MCP at /mcp. For the complete generated CLI flag reference, see the published CLI Reference.

Run from Docker

docker pull ghcr.io/swimmwatch/cloakbrowser-mcp:latest
docker run --rm --init -i \
  -v "$PWD/artifacts:/data" \
  ghcr.io/swimmwatch/cloakbrowser-mcp:latest

docker run --rm --init -p 127.0.0.1:3000:3000 \
  -v "$PWD/artifacts:/data" \
  ghcr.io/swimmwatch/cloakbrowser-mcp:latest \
  --transport streamable-http --http-host 0.0.0.0 --http-port 3000

The Docker image is based on the pinned official Playwright MCP image, installs the bridge under /opt/cloakbrowser-mcp, and writes artifacts to /data by default.

MCP client configuration

npm

{
  "mcpServers": {
    "cloakbrowser": {
      "command": "npx",
      "args": ["-y", "cloakbrowser-mcp@latest"],
      "env": {
        "PLAYWRIGHT_MCP_OUTPUT_DIR": "/tmp/cloakbrowser-artifacts",
        "PLAYWRIGHT_MCP_HEADLESS": "true"
      }
    }
  }
}

Docker

{
  "mcpServers": {
    "cloakbrowser": {
      "command": "docker",
      "args": [
        "run",
        "--rm",
        "--init",
        "-i",
        "-v",
        "/tmp/cloakbrowser-artifacts:/data",
        "ghcr.io/swimmwatch/cloakbrowser-mcp:latest"
      ]
    }
  }
}

Configuration

Use upstream PLAYWRIGHT_MCP_* variables for browser, artifact, timeout, network, and tool capability settings. Cloak-specific bridge toggles use CLOAK_PLAYWRIGHT_MCP_*. CLI flags are documented in the generated CLI Reference.

Common variables:

Variable	Default	Description
CLOAK_PLAYWRIGHT_MCP_TRANSPORT	stdio	MCP transport exposed by the bridge: stdio or streamable-http.
CLOAK_PLAYWRIGHT_MCP_HTTP_HOST	127.0.0.1	Streamable HTTP bind host.
CLOAK_PLAYWRIGHT_MCP_HTTP_PORT	3000	Streamable HTTP bind port.
CLOAK_PLAYWRIGHT_MCP_HTTP_ENDPOINT	/mcp	Streamable HTTP endpoint path.
CLOAK_PLAYWRIGHT_MCP_HTTP_AUTH_TOKEN	unset	Optional Bearer token for Streamable HTTP.
CLOAK_PLAYWRIGHT_MCP_HTTP_SESSION_BACKEND	memory	Session metadata backend. Only memory is implemented in this release.
CLOAK_PLAYWRIGHT_MCP_HTTP_SESSION_IDLE_TTL_MS	3600000	Idle TTL for Streamable HTTP sessions.
CLOAK_PLAYWRIGHT_MCP_HTTP_SESSION_MAX	32	Maximum active Streamable HTTP sessions in one process.
PLAYWRIGHT_MCP_BROWSER_ENGINE	cloak	cloak uses CloakBrowser. playwright uses the upstream Playwright MCP browser runtime.
PLAYWRIGHT_MCP_HEADLESS	true	Runs Chromium headless.
PLAYWRIGHT_MCP_OUTPUT_DIR	.playwright-mcp	Artifact directory for npm usage. Docker defaults to /data.
PLAYWRIGHT_MCP_OUTPUT_MODE	stdout	Upstream output mode, either stdout or file.
CLOAK_PLAYWRIGHT_MCP_CONSOLE_FALLBACK	true	Enables the compatibility patch for console messages.
CLOAK_PLAYWRIGHT_MCP_STEALTH_ARGS	true	Adds CloakBrowser default stealth launch arguments.
CLOAK_PLAYWRIGHT_MCP_EXTRA_ARGS	unset	Comma-separated or JSON array of extra Chromium launch arguments.

The old CLOAKBROWSER_MCP_* variables are not supported.

Tools

The upstream Playwright MCP tool list is authoritative. This project does not reimplement or re-document upstream browser schemas in source code.

Local tools:

• cloakbrowser_binary_info returns CloakBrowser package, platform, cache, and resolved binary data.
• cloakbrowser_bridge_info returns bridge metadata, upstream package/version, and local tool names.

Development

npm install
npm run build
npm test
npm run docker:build
npm run docker:smoke
npm run server:validate
npm run bridge:compare -- cloakbrowser-mcp:dev --report bridge-parity-report.json

Documentation starts at docs/getting-started.md. Contributor material is grouped under docs/contributor-guide.md.