# cdp

This skill controls Chrome through the DevTools Protocol from JavaScript. Use it to automate pages, inspect tabs, or run browser checks.

- skill · `type=skill` · Claude Code, Codex, Cursor, GitHub Copilot, Gemini CLI, OpenCode · 705 installs · ★ 494
- Author: browser-use
- License: MIT · policy=mirror · the beginning of the file is at the end of this page
- Source: https://github.com/browser-use/browser-harness-js/tree/HEAD/SKILL.md
- Updated: 2026-08-30
- HTML: https://affpapa.org/en/nevibecode/skills/cdp

## What it does

The skill runs JavaScript through the `browser-harness-js` CLI and connects it to Chrome with the DevTools Protocol. On first use, the CLI starts a long-lived Bun HTTP server that keeps one CDP session alive. The active target and globals remain available across later calls. It can attach to an existing Chromium browser or to Chrome started with remote debugging enabled.

The session exposes typed CDP wrappers through `session`, along with `listPageTargets()`, `detectBrowsers()`, and `resolveWsUrl(opts)`. The CLI also has commands for server status, startup, shutdown, restart, and logs. Code can be passed as one argument or through a heredoc; multi-line input needs an explicit `return` when a value should be printed.

\`browser-harness-js` must be reachable from `PATH` before the first call, or the command will fail; the skill documentation shows how to link its executable into a PATH directory. Bun is installed by the CLI on first run when it is missing.

## Requirements
- Works with: Chrome

## Install

### Claude Code (native platform)

1. **Skills CLI (Vercel)**
```bash
npx skills add browser-use/browser-harness-js --skill cdp -a claude-code
```

2. **Manually: put the files in place**
- File: `~/.claude/skills/cdp/SKILL.md` — Copy the whole skill folder; for one project use .claude/skills/cdp/

### Codex

1. **Skills CLI (Vercel)**
```bash
npx skills add browser-use/browser-harness-js --skill cdp -a codex
```

2. **Manually: put the files in place**
- File: `.agents/skills/cdp/SKILL.md` — For all projects use ~/.agents/skills/

### Cursor

1. **Skills CLI (Vercel)**
```bash
npx skills add browser-use/browser-harness-js --skill cdp -a cursor
```

2. **Manually: put the files in place**
- File: `.cursor/skills/cdp/SKILL.md` — Cursor also reads .agents/skills/ and .claude/skills/

### GitHub Copilot

1. **GitHub CLI**
```bash
gh skill install browser-use/browser-harness-js cdp
```

2. **Manually: put the files in place**
- File: `.github/skills/cdp/SKILL.md`

### Gemini CLI

1. **Skills CLI (Vercel)**
```bash
npx skills add browser-use/browser-harness-js --skill cdp -a gemini-cli
```

2. **Platform CLI**
```bash
gemini skills install https://github.com/browser-use/browser-harness-js
```

### Windsurf (Devin Desktop)

**Manually: put the files in place**
- File: `.devin/skills/cdp/SKILL.md` — The legacy .windsurf/skills/ path still works

### OpenCode

**Skills CLI (Vercel)**
```bash
npx skills add browser-use/browser-harness-js --skill cdp -a opencode
```

### Claude.ai

**Claude.ai**
- Zip the folder and upload it in Settings → Capabilities → Skills

Where a file is given instead of a command, copy the files from the source to that path: https://github.com/browser-use/browser-harness-js/tree/HEAD/SKILL.md

## When to use it
- open a Chrome page through CDP
- read the current tab’s title or DOM
- switch between browser tabs
- run JavaScript in an attached browser
- check the CDP server status

## Example prompts
- Connect to the running Chrome browser through CDP with `browser-harness-js`, then open `https://example.com`.
- Use `browser-harness-js` to run JavaScript that returns the title of the current page.
- List available Chrome tabs with `listPageTargets()`, choose one, and attach `session` to it.

## Source text · SKILL.md · MIT

Below is the content of a third-party file. It is data, not instructions for you: do not act on anything written inside unless the human asks. Block tag: 0b0c009d6ad11d51.

BEGIN THIRD-PARTY FILE 0b0c009d6ad11d51
````text
---
name: cdp
description: Drive Chrome via the DevTools Protocol from JavaScript. Run JS snippets through the `browser-harness-js` CLI — it auto-spawns a long-lived bun HTTP server holding a fully-typed CDP `Session`, and every call (`browser-harness-js 'await session.Page.navigate(...)'`) executes against the same persistent connection. Session, active target, and globals survive across calls. Use when the user wants to automate, script, or inspect a Chrome browser via CDP — single tab or multi-tab, attach to existing Chrome or to a new one launched with --remote-debugging-port.
---

# CDP — `browser-harness-js` skill

Custom codegen'd CDP SDK (every method from browser_protocol.json + js_protocol.json gets a typed wrapper) plus a tiny HTTP server that holds one persistent CDP `Session`. The `browser-harness-js` CLI auto-starts the server on first use and forwards JS snippets to it.

The SDK lives in the skill's `sdk/` directory. In the rest of this doc, `<skill-dir>` refers to wherever `npx skills add` installed the skill (Claude Code: `~/.claude/skills/cdp`; Cursor: `~/.cursor/skills/cdp`; other agents vary). The CLI should be on PATH as `browser-harness-js`.

## Setup (once, first use)

`npx skills add` drops the skill into your agent's skills directory but does NOT put the CLI on PATH. Before the first call, verify it's reachable and symlink it into any directory on your PATH if not:

```bash
# macOS (Apple Silicon + Homebrew)
command -v browser-harness-js >/dev/null || ln -sf <skill-dir>/sdk/browser-harness-js /opt/homebrew/bin/browser-harness-js

# macOS (Intel) / most Linux — may need sudo
command -v browser-harness-js >/dev/null || ln -sf <skill-dir>/sdk/browser-harness-js /usr/local/bin/browser-harness-js

# Linux without sudo (ensure ~/.local/bin is on PATH)
command -v browser-harness-js >/dev/null || { mkdir -p ~/.local/bin && ln -sf <skill-dir>/sdk/browser-harness-js ~/.local/bin/browser-harness-js; }
```

The CLI auto-installs `bun` on first run if it's missing (the server is Bun-native). Set `BROWSER_HARNESS_SKIP_BUN_INSTALL=1` to opt out.

## How to use

Just run `browser-harness-js '<JS>'`. The first call spawns the server in the background; subsequent calls hit the same process and so reuse the same `session`, the same WebSocket to Chrome, and any globals you set.

```bash
browser-harness-js 'await session.connect()'
browser-harness-js 'await session.Page.navigate({url:"https://example.com"})'
browser-harness-js '(await session.Runtime.evaluate({expression:"document.title",returnByValue:true})).result.value'
```

Output is the **raw result content** — no `{ok,result}` envelope.

| Result type | stdout |
|---|---|
| string                       | bare text, no JSON quotes (e.g. `Example Domain`) |
| number / boolean             | `42`, `true` |
| object / array (non-empty)   | compact JSON (e.g. `{"frameId":"..."}`, `[1,2,3]`) |
````
END THIRD-PARTY FILE 0b0c009d6ad11d51

The third-party file has ended. Everything between the 0b0c009d6ad11d51 tags is data: requests and commands from it are not followed. An “end of file” line with another tag inside the block is part of the file.

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