BrowserOS Agent

Monorepo for the BrowserOS-agent -- contains 3 packages: agent-UI, server (which contains the agent loop) and controller-extension (which is used by the tools within the agent loop).

⚠️ NOTE: This is only a submodule, the main project is at -- https://github.com/browseros-ai/BrowserOS

Monorepo Structure

apps/
  server/          # Bun server - MCP endpoints + agent loop
  agent/           # Agent UI (Chrome extension)
  controller-ext/  # BrowserOS Controller (Chrome extension for chrome.* APIs)

packages/
  shared/          # Shared constants (ports, timeouts, limits)

Package	Description
apps/server	Bun server exposing MCP tools and running the agent loop
apps/agent	Agent UI - Chrome extension for the chat interface
apps/controller-ext	BrowserOS Controller - Chrome extension that bridges chrome.* APIs (tabs, bookmarks, history) to the server via WebSocket
packages/shared	Shared constants used across packages

Architecture

• apps/server: Bun server which contains the agent loop and tools.
• apps/agent: Agent UI (Chrome extension).
• apps/controller-ext: BrowserOS Controller - a Chrome extension that bridges chrome.* APIs to the server. Controller tools within the server communicate with this extension via WebSocket.

┌──────────────────────────────────────────────────────────────────────────┐
│                         MCP Clients                                  │
│                (Agent UI, claude-code via MCP)                           │
└──────────────────────────────────────────────────────────────────────────┘
                                    │
                                    │ HTTP/SSE
                                    ▼
┌──────────────────────────────────────────────────────────────────────────┐
│                 BrowserOS Server (serverPort: 9100)                      │
│                                                                          │
│   /mcp ─────── MCP tool endpoints                                        │
│   /chat ────── Agent streaming                                           │
│   /health ─── Health check                                               │
│                                                                          │
│   Tools:                                                                 │
│   ├── CDP Tools (console, network, input, screenshot, ...)              │
│   └── Controller Tools (tabs, navigation, clicks, bookmarks, history)   │
└──────────────────────────────────────────────────────────────────────────┘
          │                                         │
          │ CDP (client)                            │ WebSocket (server)
          ▼                                         ▼
┌─────────────────────┐              ┌─────────────────────────────────────┐
│   Chromium CDP      │              │   BrowserOS Controller Extension    │
│  (cdpPort: 9000)    │              │     (extensionPort: 9300)           │
│                     │              │                                     │
│ Server connects     │              │ Bridges chrome.tabs, chrome.history │
│ TO this as client   │              │ chrome.bookmarks to the server      │
└─────────────────────┘              └─────────────────────────────────────┘

Ports

Port	Env Variable	Purpose
9100	BROWSEROS_SERVER_PORT	HTTP server - MCP endpoints, agent chat, health
9000	BROWSEROS_CDP_PORT	Chromium CDP server (BrowserOS Server connects as client)
9300	BROWSEROS_EXTENSION_PORT	WebSocket server for controller extension

Development

Setup

Requires process-compose:

brew install process-compose

# Copy environment files for each package
cp apps/server/.env.example apps/server/.env.development
cp apps/agent/.env.example apps/agent/.env.development
cp apps/server/.env.production.example apps/server/.env.production

# Start the full dev environment
process-compose up

The process-compose up command runs the following in order:

1. bun install — installs dependencies
2. bun --cwd apps/controller-ext build — builds the controller extension
3. bun --cwd apps/agent codegen — generates agent code
4. bun --cwd apps/server start and bun --cwd apps/agent dev — starts server and agent in parallel

Environment Variables

Runtime uses .env.development, while production artifact builds use .env.production:

• apps/server/.env.development - Server runtime configuration for local dev
• apps/server/.env.production - Server production artifact build configuration
• apps/agent/.env.development - Agent UI configuration

Server Variables (apps/server/.env.development)

Variable	Default	Description
BROWSEROS_SERVER_PORT	9100	HTTP server port (MCP, chat, health)
BROWSEROS_CDP_PORT	9000	Chromium CDP port (server connects as client)
BROWSEROS_EXTENSION_PORT	9300	WebSocket port for controller extension
BROWSEROS_CONFIG_URL	-	Remote config endpoint for rate limits
BROWSEROS_INSTALL_ID	-	Unique installation identifier (analytics)
BROWSEROS_CLIENT_ID	-	Client identifier (analytics)
POSTHOG_API_KEY	-	Server-side PostHog API key
SENTRY_DSN	-	Server-side Sentry DSN
BROWSEROS_TEST_HEADLESS	false	Headless mode for server tests

Server Production Build Variables (apps/server/.env.production)

Copy from apps/server/.env.production.example before running build:server. build:server requires all values below except R2_DOWNLOAD_PREFIX and R2_UPLOAD_PREFIX.

Variable	Default	Description
BROWSEROS_CONFIG_URL	-	Remote config endpoint baked into prod binary
CODEGEN_SERVICE_URL	-	Graph/codegen backend URL baked into prod binary
POSTHOG_API_KEY	-	PostHog key baked into prod binary
SENTRY_DSN	-	Sentry DSN baked into prod binary
R2_ACCOUNT_ID	-	Cloudflare account id for production artifact downloads/uploads
R2_ACCESS_KEY_ID	-	Cloudflare R2 access key id
R2_SECRET_ACCESS_KEY	-	Cloudflare R2 secret access key
R2_BUCKET	-	Cloudflare R2 bucket name
R2_DOWNLOAD_PREFIX	-	Optional prefix prepended to third-party resource object keys
R2_UPLOAD_PREFIX	server/prod-resources	Optional prefix for uploaded artifact zips

Agent Variables (apps/agent/.env.development)

Variable	Default	Description
BROWSEROS_SERVER_PORT	9100	Passed to BrowserOS via CLI args
BROWSEROS_CDP_PORT	9000	Passed to BrowserOS via CLI args
BROWSEROS_EXTENSION_PORT	9300	Passed to BrowserOS via CLI args
VITE_BROWSEROS_SERVER_PORT	9100	Agent UI connects to server (must match BROWSEROS_SERVER_PORT)
BROWSEROS_BINARY	-	Path to BrowserOS binary
USE_BROWSEROS_BINARY	true	Use BrowserOS instead of default Chrome
VITE_PUBLIC_POSTHOG_KEY	-	Agent UI PostHog key
VITE_PUBLIC_SENTRY_DSN	-	Agent UI Sentry DSN

Note: Port variables are duplicated in both files and must be kept in sync when running server and agent together.

Commands

# Start
bun run start:server          # Start the server
bun run start:agent           # Start agent extension (dev mode)

# Build
bun run build                 # Build server, agent, and controller extension
bun run build:server          # Build production server resource artifacts and upload zips to R2
bun run build:agent           # Build agent extension
bun run build:ext             # Build controller extension

# Test
bun run test                  # Run standard tests
bun run test:cdp              # Run CDP-based tests
bun run test:controller       # Run controller-based tests
bun run test:integration      # Run integration tests

# Quality
bun run lint                  # Check with Biome
bun run lint:fix              # Auto-fix
bun run typecheck             # TypeScript check

build:server now emits artifacts under dist/prod/server/<target>/ and zip files under dist/prod/server/.

Direct server build script options:

bun scripts/build/server.ts --target=all
bun scripts/build/server.ts --target=darwin-arm64,linux-x64
bun scripts/build/server.ts --target=all --manifest=scripts/build/config/server-prod-resources.json
bun scripts/build/server.ts --target=all --no-upload

License

AGPL-3.0