cockroach-browser MCP

Cockroach Browser is a local-first TypeScript browser platform for browser-capable AI agents and operator automation. Its bounded runtime launches Chromium, Firefox, or WebKit, while separate unrestricted subpaths expose the complete installed Playwright and Puppeteer Core contracts. It combines real page rendering, semantic interaction, forms, files, screenshots, PDFs, network observations, audits, stateful sessions, test generation, model-directed execution, fleet adapters, mobile WebDriver transport, and authenticated tooling without silently giving an agent every browser profile, credential, origin, or machine resource.

The package supports headed or headless Chromium, Firefox, and WebKit; explicit raw CDP and WebDriver BiDi; Puppeteer Core; Playwright Test and code generation; TypeScript, Python, Java, .NET, Ruby, and Go clients; a built-in model gateway and agent loop; local and provider-backed fleets; native mobile WebDriver/Appium endpoints; an authenticated daemon; an observation-first MCP server; Docker; and a local dashboard. Optional adapters connect Maqam, Qarinah, Cockroach Crawler, ProductLoop OS, managed proxy networks, provider-authorized challenges, and live-session viewers without pretending Cockroach Browser operates those external services.

It detects login, consent, CAPTCHA, and access challenges and can pause for a human or an operator-authorized resolver. High-authority browser controls stay behind explicit host configuration and session policy. Maqam approvals are an optional integration.

Explicit high-authority controls

Cockroach Browser keeps powerful browser options explicit instead of discovering or exposing them silently:

These controls preserve the powerful operational workflows people expect from an agent browser while keeping the operator—not page content or the model—in charge of authority.

Release status

Current release line: 0.4.0-rc.1

• License: AGPL-3.0-or-later

• Runtime: maintained Node.js 22, 24, or 26

• Registry: cockroach-browser

• Capability registry: 124 entries, with 114 available and 10 adapter-backed

• MCP identity: io.github.AjnasNB/cockroach-browser

• Paper: Cockroach Browser: A Local-First Browser Runtime for AI Agents

• Published paper v1.1 DOI: 10.5281/zenodo.21850760

• Paper series DOI: 10.5281/zenodo.21701791

Verify the npm version, provenance, Git commit, and matching GitHub release before production use.

Related MCP server: Ghostlight

Install once for your user account

Install the CLI globally when the same operator account should use Cockroach Browser across projects:

npm install --global cockroach-browser
cockroach-browser bootstrap
cockroach-browser doctor

The global installation makes the CLI available across the current computer account. It does not grant access to ambient browser profiles, cookies, origins, or machine resources. Each session still requires explicit authority.

Install inside one project

npm install cockroach-browser
npx cockroach-browser bootstrap

bootstrap verifies Node.js, installs the Chromium, Firefox, and WebKit builds used by Playwright 1.62.1 only when any engine is missing, initializes the owner-scoped data root, and probes an authenticated ephemeral loopback daemon. Use --check-only when the command must not download a browser.

Operator bootstrap, completions, and per-user autostart

Completion generation writes to standard output and never edits your shell profile:

cockroach-browser completion bash
cockroach-browser completion zsh
cockroach-browser completion powershell

The optional daemon installer is deliberately a per-user operation. It requires an explicit local-owner confirmation, always binds the generated daemon to 127.0.0.1, and never invokes sudo, an administrator prompt, or a system-wide service manager:

cockroach-browser service status
cockroach-browser service install --confirm-local-owner
cockroach-browser service uninstall --confirm-local-owner

Windows installs a current-user Startup command that begins at the next login. macOS installs and loads a current-user LaunchAgent, and Linux installs and starts a systemd user unit. Add --definition-only to inspect the exact generated file without activation. The installer refuses to overwrite or remove a file it did not create. Uninstall removes the definition only; browser data, profiles, evidence, and receipts remain intact.

Start with the embedded SDK

import { BrowserRuntime } from "cockroach-browser";

const runtime = new BrowserRuntime({ root: ".cockroach-browser" });
await runtime.initialize();

try {
  const session = await runtime.createSession({
    purpose: "Inspect a public page",
    startUrl: "https://example.com/",
    policy: {
      allowedOrigins: ["https://example.com"],
      allowedActions: ["snapshot", "extract", "screenshot"],
      allowedEffects: ["read"],
      requireApprovalFor: [],
      budget: {
        maxActions: 10,
        maxDurationMs: 120000,
        maxTabs: 1,
        maxEvidenceBytes: 8388608
      }
    }
  });

  const snapshot = await runtime.snapshot(session.id);
  console.log({
    sessionId: session.id,
    title: snapshot.title,
    url: snapshot.url,
    references: snapshot.refs.length,
    revision: snapshot.digest
  });
} finally {
  await runtime.close();
}

The host owns session creation and authority. Every session requires at least one explicit allowed origin.

Run the authenticated local daemon

npx cockroach-browser serve \
  --host 127.0.0.1 \
  --port 43110 \
  --root .cockroach-browser \
  --token-file .cockroach-browser/auth-token

The daemon listens on loopback by default and creates a strong bearer token when the token file does not exist. Keep that file out of source control and shell history.

Create session.json:

{
  "purpose": "Read the public example page",
  "startUrl": "https://example.com/",
  "mode": "headless",
  "policy": {
    "allowedOrigins": ["https://example.com"],
    "allowedActions": ["snapshot", "extract", "screenshot"],
    "allowedEffects": ["read"],
    "requireApprovalFor": [],
    "budget": {
      "maxActions": 10,
      "maxDurationMs": 120000,
      "maxTabs": 1,
      "maxEvidenceBytes": 8388608
    }
  }
}

Then use the authenticated CLI:

npx cockroach-browser session create \
  --config session.json \
  --token-file .cockroach-browser/auth-token

npx cockroach-browser session list \
  --token-file .cockroach-browser/auth-token

npx cockroach-browser snapshot \
  --session SESSION_ID \
  --token-file .cockroach-browser/auth-token

npx cockroach-browser audit \
  --session SESSION_ID \
  --kinds accessibility,security \
  --token-file .cockroach-browser/auth-token

npx cockroach-browser capture \
  --session SESSION_ID \
  --token-file .cockroach-browser/auth-token \
  --require-stable \
  --include-bounds

npx cockroach-browser network \
  --session SESSION_ID \
  --token-file .cockroach-browser/auth-token \
  --limit 100

npx cockroach-browser network export \
  --session SESSION_ID \
  --token-file .cockroach-browser/auth-token \
  --format json > ./artifacts/network.json

The HTTP action route is disabled by default. Production mutations should enter through the Maqam-bound driver. A trusted local host can explicitly enable the raw route with --allow-raw-actions. Host-controlled executable, CDP, proxy, header, and profile-secret fields remain disabled unless that host also passes --allow-session-host-config.

The authenticated daemon exposes:

Use the typed daemon client

import { readFile } from "node:fs/promises";
import { BrowserClient } from "cockroach-browser/client";

const token = (await readFile(".cockroach-browser/auth-token", "utf8")).trim();
const browser = new BrowserClient({
  baseUrl: "http://127.0.0.1:43110",
  token
});

console.log(await browser.health());
console.log(await browser.capabilities());

BrowserClient supports health, capabilities, session creation and inspection, session close, navigation graphs, actions, bounded batches, jobs, snapshots, paired capture, bounded network observation and export, audits, persistent profile administration, activity polling, and human-handoff resume. The daemon still enforces its own route and session-authority settings.

Connect through MCP

Start the daemon, load its token into the client process through a secret store, and configure an MCP client:

{
  "mcpServers": {
    "cockroach-browser": {
      "command": "npx",
      "args": ["-y", "cockroach-browser@0.4.0-rc.1", "mcp"],
      "env": {
        "COCKROACH_BROWSER_URL": "http://127.0.0.1:43110",
        "COCKROACH_BROWSER_TOKEN": "<load from your secret store>"
      }
    }
  }
}

Do not commit a live daemon token to an MCP configuration. The MCP process reads COCKROACH_BROWSER_TOKEN and optionally COCKROACH_BROWSER_URL.

The MCP surface is observation-first:

• browser_capabilities

• browser_health

• browser_sessions

• browser_snapshot

• browser_audit

• browser_capture

• browser_network

• browser_propose_action

browser_propose_action returns a canonical proposal and input digest. It does not execute the action. Dispatch consequential work through Maqam.

Run with Docker

docker compose up --build

The included profile:

• exposes the daemon only on host loopback at 127.0.0.1:43110

• runs as the non-root node user

• uses a read-only root filesystem

• drops all Linux capabilities

• enables no-new-privileges

• stores browser data in a dedicated volume

• checks daemon health with the generated bearer token

Read the generated token into a local file:

docker compose exec -T browser cat /data/auth-token > .cockroach-browser-docker-token

Then point CLI or SDK clients at http://127.0.0.1:43110 and use that token file.

CLI reference

Profile import and export require COCKROACH_BROWSER_PROFILE_PASSPHRASE. Passphrases are never accepted as command-line arguments.

Daemon clients can use --token, --token-file, COCKROACH_BROWSER_TOKEN, or COCKROACH_BROWSER_TOKEN_FILE. They can override the URL with --url or COCKROACH_BROWSER_URL.

124 source-registered capabilities

The registry is generated from src/capabilities.ts, not from a marketing checklist.

Sessions

Authorized browser sessions; headless or headed Chromium, Firefox, and WebKit; explicit CDP attachment; raw CDP and WebDriver BiDi; complete Playwright and Puppeteer Core re-exports; native mobile WebDriver/Appium transport; cross-platform Chrome, Edge, Brave, and Chromium discovery; bundled, system, custom-executable, and CDP providers; reviewed unpacked Chromium extensions; runtime-owned persistent profiles; named isolated profiles; encrypted storage state and checkpoints; clipboard; explicit proxies; bounded runtime emulation; and unrestricted upstream emulation through the raw operator APIs.

Interaction

Tabs and popups; exclusive tab locks; navigation; semantic references; CSS, XPath, role, text, label, and test-id locators; web-first assertions; complete JavaScript and element handles; browser, context, page, target, worker, frame, request, response, and WebSocket events; forms; mouse, keyboard, touch, drag, scroll, and waits; frames and Shadow DOM; dialogs; history; JavaScript; batches; files and downloads; general request/response rewriting; WebSocket routing; Playwright Test; and JavaScript, TypeScript, Python, Java, and C# code generation.

Evidence

PNG and JPEG screenshots; paired visual-plus-semantic capture; annotations; PDF capture; traces; HAR capture and replay; session video; console and network evidence; cache and ledger clearing; network inspection and export; hash-chained receipts; extraction; JavaScript and CSS coverage; heap snapshots; runtime object queries; screencasting; performance metrics; and protocol profiling.

Audits

Accessibility; page performance observations; broken assets; console errors and warnings; page security observations; screenshot comparison with visual diffs; and a mechanically generated inventory of the pinned Playwright and Puppeteer declaration surfaces.

Security

Challenge detection; human challenge handoff; origin allowlists; private-network blocking; effect-level policy; finite resource budgets; exact-origin static network interception.

Adapter-backed security surfaces:

• Exact action approvals through MaqamApprovalProvider

• Host-resolved secret references through SecretResolver

• Provider-authorized challenge services through an explicitly selected fleet adapter

Deployment

CLI; Playwright Test and codegen CLIs; shell completions; per-user daemon definitions; bootstrap; TypeScript, Python, Java, .NET, Ruby, and Go SDKs; authenticated HTTP, OpenAPI, and Prometheus surfaces; native stdio MCP; Docker; dashboard; authenticated remote workers; worker pool; a working local three-engine process fleet; exact managed-fleet, proxy-class, challenge-mode, and live-view adapter contracts; activity streams; crash-resumable jobs; doctor and health checks.

Integrations

Adapter-backed:

• Maqam governance for operations routed through its adapter

• Qarinah memory

• Cockroach Crawler handoff

• ProductLoop OS capability snapshot

• Managed fleet, proxy, challenge, and live-view providers selected by the operator

Available:

• Signed browser lifecycle webhooks with a local durable outbox, HMAC-SHA256 signatures, bounded retries, dead letters, and hash-linked delivery receipts

• Persistent team session ownership with revocable viewer and operator grants, without raw profile sharing

• OpenAI-compatible model gateway with bounded structured tool calls

• Finite-step browser agent loop over semantic snapshots, exact actions, and receipts

The complete searchable matrix, including capability IDs, implementation status, and exact API surfaces, is in docs/capabilities.md.

Signed lifecycle webhooks

SignedWebhookDispatcher implements BrowserEventPublisher and can be attached to BrowserRuntime. Browser lifecycle events are sanitized and written to a local durable outbox before any network work occurs. publish() does not resolve DNS, read a signing key, or contact an endpoint. An operator-controlled drain() performs those privileged steps later.

import {
  BrowserRuntime,
  SignedWebhookDispatcher
} from "cockroach-browser";

const webhookUrl = process.env.COCKROACH_BROWSER_WEBHOOK_URL;
if (!webhookUrl) throw new Error("COCKROACH_BROWSER_WEBHOOK_URL is required");

const webhooks = new SignedWebhookDispatcher({
  root: ".cockroach-browser/webhooks",
  secretResolver: {
    async resolve(reference) {
      const prefix = "ref:env/";
      if (!reference.startsWith(prefix)) {
        throw new Error("Unsupported webhook secret reference");
      }
      const value = process.env[reference.slice(prefix.length)];
      if (!value) throw new Error(`Missing secret for ${reference}`);
      return value;
    }
  },
  maxPayloadBytes: 64 * 1024,
  maxQueueItems: 10_000,
  maxStorageBytes: 256 * 1024 * 1024
});

await webhooks.initialize();
await webhooks.upsertEndpoint({
  id: "release-automation",
  url: webhookUrl,
  secretRef: "ref:env/COCKROACH_BROWSER_WEBHOOK_SECRET",
  keyId: "release-2026-07",
  events: [
    "browser.action.completed",
    "browser.challenge.detected",
    "browser.evidence.recorded"
  ],
  maxAttempts: 3,
  timeoutMs: 5_000
});

const runtime = new BrowserRuntime({
  root: ".cockroach-browser/runtime",
  eventPublisher: webhooks
});
await runtime.initialize();

// Run this from an operator-owned worker or scheduler.
const result = await webhooks.drain({
  maxItems: 50,
  deadlineMs: 30_000
});
console.log(result, await webhooks.health());

Endpoint configuration stores only an opaque ref: value. The host resolver returns the signing key during drain(), and the key is never written to the outbox or receipt ledger. Endpoints must be credential-free public HTTPS URLs without a query string or fragment. DNS is checked again and pinned for every attempt; private, loopback, translated, and mixed public/private results are rejected, and redirects are never followed.

Each request carries:

• x-cockroach-browser-event

• x-cockroach-browser-delivery

• x-cockroach-browser-timestamp

• x-cockroach-browser-nonce

• x-cockroach-browser-key-id

• x-cockroach-browser-signature: v1=<HMAC-SHA256>

Use verifyWebhookSignature() and WebhookReplayGuard at the receiver. A normal retry keeps the same stable delivery ID while using a fresh timestamp and nonce, so the receiver must also persist processed delivery IDs and return success for duplicates. This is a local durable at-least-once outbox, not a distributed exactly-once queue. A manual dead-letter retry intentionally creates a new delivery ID.

Transient transport failures and HTTP 408, 425, 429, and 5xx responses retry within the configured attempt and deadline ceilings. Other non-2xx responses become dead letters. Retry-After is honored up to 30 seconds. health() reports queue, receipt, dead-letter, and storage counts; retryDeadLetter() and purgeDeadLetter() provide explicit recovery; verify() checks the hash-linked terminal receipt chain. See the signed webhook manual for receiver verification, replay handling, quotas, and recovery procedures.

Action surface

The typed runtime implements 65 action kinds:

navigate, back, forward, reload, click, doubleClick, fill, type, press, hover, focus, check, uncheck, select, scroll, drag, mouse.move, mouse.down, mouse.up, mouse.click, keyboard.down, keyboard.up, keyboard.insertText, upload, download, evaluate, query.inspect, emulation.set, emulation.clear, cache.clear, console.clear, network.clear, wait, challenge.resolve, history.inspect, capture.paired, annotate.show, annotate.clear, clipboard.read, clipboard.write, network.inspect, network.export, network.route.add, network.route.remove, network.routes.list, state.save, state.load, state.list, state.delete, screenshot, pdf, snapshot, extract, cookies.read, cookies.write, storage.read, storage.write, tab.open, tab.close, tab.switch, tab.lock, tab.unlock, tab.lock.status, trace.start, and trace.stop.

Availability in the type system does not grant authority. The session policy, effect policy, approval provider, server surface, origin checks, and resource budget decide whether an action can run.

Exact targets and same-origin frames

An element action accepts exactly one snapshot ref, CSS selector, or XPath expression. A CSS or XPath target may include an exact same-origin frame selector by index, name, or URL. Semantic refs already carry their frame identity and cannot be combined with a separate frame target.

await runtime.act(session.id, {
  kind: "fill",
  xpath: "//*[@id='account-name']",
  frame: { name: "account-panel" },
  value: "Ajnas",
  purpose: "Fill the reviewed same-origin account form"
});

Cross-origin frame targeting is rejected. XPath and selector strings are length-bounded and do not grant new origin authority.

Dialogs and low-level input

Unexpected dialogs are dismissed. Accepting a dialog requires allowDialogAccept: true, remains approval-bound even when the session has an empty requireApprovalFor list, and may resolve prompt text only from an opaque host secret reference. Low-level mouse coordinates must remain inside the current viewport. Keyboard text, key names, click counts, and movement steps have finite ceilings.

await runtime.act(session.id, {
  kind: "click",
  ref: confirmButton.ref,
  dialog: { action: "accept" },
  purpose: "Accept the exact reviewed confirmation"
});

Bounded history and network routes

history.inspect returns a sanitized, session-local list capped by maxHistoryEntries. It is not browser-profile discovery and does not expose a user's ambient history.

Network routes are off until allowNetworkInterception is enabled. A route may match one already admitted origin, a bounded pathname glob, an explicit method set, and optional resource types. It may only abort the request or return a static response. It cannot redirect requests, inject credentials, discover cookies, or widen the origin policy. Static response bodies are constrained by maxRouteFulfillBytes, and cumulative fulfilled bytes are constrained by maxInterceptedBytes.

await runtime.act(session.id, {
  kind: "network.route.add",
  route: {
    id: "release-fixture",
    origin: "https://docs.example.com",
    pathPattern: "/api/releases/**",
    methods: ["GET"],
    resourceTypes: ["fetch"],
    response: {
      action: "fulfill",
      contentType: "application/json",
      body: "{\"releases\":[]}"
    }
  },
  purpose: "Install a deterministic response for the reviewed test"
});

Product stack integrations

Maqam

import { createMaqamBrowserDriver } from "cockroach-browser/maqam";

const driver = createMaqamBrowserDriver({
  runtime,
  async resolveValueRef(reference) {
    return secretStore.resolve(reference);
  },
  async verifyExecution(request) {
    return maqamAuthority.verifyExecution(request);
  },
  async verifyPlanToken(request) {
    return maqamAuthority.verifyPlanToken(request);
  }
});

The two verifier callbacks are mandatory. They must consult a trusted Maqam ledger or verify a Maqam signature; checking only field shape is not enough. The driver fails closed when either verifier is absent, rejects, or throws.

The driver exposes four operations: observe, preview, apply, and submit. It binds work to an exact page revision, origin, input digest, run, approval, operation ID, and authoritatively verified plan token. Browser lifecycle, login, profiles, proxy configuration, secrets, and raw JavaScript stay in the trusted host.

Qarinah

import { createQarinahContextRecorder } from "cockroach-browser/qarinah";

const recorder = createQarinahContextRecorder({
  async appendBrowserOutcome(event) {
    await hostProvidedQarinahSink.appendBrowserOutcome(event);
  }
});

The host supplies the persistence callback supported by its installed Qarinah release. Qarinah receives cited, metadata-only outcomes with canonical input and output digests, the browser receipt hash, and evidence IDs as top-level context links. The recorder recursively removes authorization data, cookies, credentials, passwords, passphrases, secrets, tokens, storage values, form values, and API keys. It does not persist hidden reasoning or profile data. For consequential mutations, a host may link the sanitized outcome to a complete causal receipt chain when every stage exists; the recorder does not invent or require that chain.

Cockroach Crawler

import { createCrawlerHandoff } from "cockroach-browser/crawler";

const handoff = createCrawlerHandoff(crawler);

Use Cockroach Crawler for broad, bounded collection and Cockroach Browser for interactive page evidence. Only explicit seed URLs, allowed origins, and finite crawl budgets cross the boundary. Keep the browser-session purpose in the browser evidence and host orchestration record; do not pass it as crawler authority. Profiles, cookies, authenticated state, session secrets, and interactive browser state never cross the handoff.

ProductLoop OS

import { productLoopBrowserCapabilitySnapshot } from "cockroach-browser/productloop";

const browserCapabilitySnapshot = productLoopBrowserCapabilitySnapshot();

The returned value is a structural capability snapshot for a host-owned ProductLoop adapter. It describes observations, proposals, effects, transports, governance requirements, and lifecycle ownership; it is not a directly registerable ProductLoop connector manifest. Translate it into the exact versioned ProductLoop contract accepted by the installed release. The snapshot grants no origin, profile, credential, lifecycle, or action authority.

Maqam governance applies only to browser operations routed through createMaqamBrowserDriver and a Maqam gateway. Cockroach Browser also has trusted-host SDK and explicitly enabled raw-action surfaces; those remain under host policy and must not be described as Maqam-governed unless the host actually routes them through the adapter.

Challenge handling

When Cockroach Browser detects a login, consent screen, CAPTCHA, or access challenge:

1. The session moves into a challenge state.

2. Evidence records explain what was detected.

3. Automated execution pauses.

4. A user handles the challenge in a headed session, or an explicitly authorized external workflow resolves it.

5. The trusted host calls resumeAfterHuman, the challenge-resume endpoint, or the approval-bound challenge.resolve action.

6. The runtime independently checks the page again before leaving the challenge state.

7. Policy, origin, budget, approval, and receipt checks continue to apply.

Challenge handling is a pause and handoff protocol, never a bypass mechanism.

import { BrowserRuntime } from "cockroach-browser";

const runtime = new BrowserRuntime({
  approvalProvider: maqamApprovalProvider,
  challengeResolver: {
    async resolve(request, signal) {
      return operatorQueue.waitForCompletion(
        {
          sessionId: request.sessionId,
          origin: request.origin,
          challenge: request.report.kind,
          deadlineAt: request.deadlineAt
        },
        { signal }
      );
    }
  }
});

await runtime.act(sessionId, {
  kind: "challenge.resolve",
  purpose: "Ask the authorized operator to complete the active challenge"
});

The callback receives metadata only. It never receives a Playwright page, cookies, storage, credentials, or raw browser-control primitives. A resolver claim is not accepted as proof: the runtime re-detects the challenge, keeps the session paused when it remains, and writes the result into a hash-linked action receipt.

Security defaults

• Loopback-only daemon binding

• Strong bearer-token authentication

• Direct HTTP action dispatch disabled

• Host-controlled session configuration disabled

• Explicit origin allowlists for every session

• Private and loopback destination denial unless the deployment owner opts in

• DNS resolution checks and session pinning

• Separate read, write, execute, upload, download, and credential effects

• Explicit action approvals for high-risk operations

• Finite action, duration, tab, upload, download, snapshot, and evidence ceilings

• Content-addressed evidence and hash-linked receipts

• Observation-first MCP

• Separate data roots and profiles for separate trust domains

Headless mode is not a sandbox. Treat browser rendering, JavaScript, remote CDP, proxies, uploads, downloads, and imported profiles as privileged capabilities.

Read the complete security policy before exposing the runtime to another process.

Documentation

• Documentation home

• Getting started

• Sessions and profiles

• Actions and semantic references

• Capture and evidence

• Network authority

• Files, uploads, and downloads

• Audits and visual comparison

• Durable local jobs

• MCP

• Maqam integration

• Qarinah integration

• Cockroach Crawler handoff

• ProductLoop OS

• Deployment

• Capability matrix

• Alternatives and product-layer comparison

• Security

• Local dashboard - served by cockroach-browser serve

Development and release verification

npm ci
npm run typecheck
npm run build
npm test
npm run check:package
npm run check:site
npm audit --omit=dev
npm pack --dry-run --ignore-scripts

Or run the complete gate:

npm run check

The package scripts compile TypeScript, execute the built Node test suite, validate package contents and public documentation, audit runtime dependencies, and inspect the exact npm tarball surface.

License

Cockroach Browser is available under the GNU Affero General Public License v3.0 or later.

Copyright Ajnas NB.