Browser Harness ♞

Connect an LLM directly to your real browser with a thin, editable CDP harness. For browser tasks where you need complete freedom.

One websocket to Chrome, nothing between. The agent writes what's missing during execution. The harness improves itself every run.

Try browser-harness in Browser Use Cloud or paste the setup prompt into your coding agent.

  ● agent: wants to upload a file
  │
  ● agent-workspace/agent_helpers.py → helper missing
  │
  ● agent writes it                         agent_helpers.py
  │                                                       + custom helper
  ✓ file uploaded

You will never use the browser again.

Setup prompt

Paste into Claude Code or Codex:

Install or upgrade browser-harness to the latest stable version with uv using Python 3.12, register the skill from `browser-harness skill`, and connect it to my browser. Follow https://github.com/browser-use/browser-harness/blob/main/install.md if setup or connection fails.

The agent will open chrome://inspect/#remote-debugging. Tick the checkbox so the agent can connect to your browser:

Click Allow when the per-attach popup appears (Chrome 144+):

See agent-workspace/domain-skills/ for example tasks.

Built-in agent (Browser Harness TUI)

Browser Harness ships its own agent: a fork of OpenAI Codex with a Terminal-style TUI and native browser-harness tool integration, published at browser-use/browser-harness-tui.

Run it now (from this branch)

This agent lives on the codex-embed-browser-harness branch (not yet on PyPI), so run it straight from a checkout. Prereqs: Python ≥ 3.11, uv, and a Chrome to drive (local, or a Browser Use Cloud browser).

# 1. Get this branch
git clone -b codex-embed-browser-harness https://github.com/browser-use/browser-harness
cd browser-harness

# 2. Install the package into a venv
uv sync            # (or: python3.11 -m venv .venv && .venv/bin/pip install -e .)

# 3. Launch the TUI — the first run auto-downloads the prebuilt agent binary
#    for your platform (~86 MB, cached under ~/.browser-harness/agent-bin/).
#    From a checkout, ./browser-harness runs the working tree directly:
./browser-harness tui
#    or dispatch a task headlessly:
./browser-harness agent "open example.com and tell me the page title"

Prebuilt binaries are published for macOS (Apple Silicon & Intel) and Linux (x86_64 & arm64) — the download is auto-selected for your platform, so there's no toolchain and no long build.

Authenticate the agent (one-time). The agent is a Codex fork, so it signs in exactly like Codex — either a ChatGPT login or an API key. After the first run has downloaded the binary:

# ChatGPT sign-in (opens a browser):
~/.browser-harness/agent-bin/agent-v0.1.0/codex login
# …or use an API key instead:
export OPENAI_API_KEY=sk-...

If you already use OpenAI Codex on this machine, its ~/.codex login is reused — no separate sign-in needed.

Connect a browser. Local Chrome must expose CDP: open chrome://inspect/#remote-debugging, tick Allow remote debugging for this browser instance (and click Allow on the Chrome 144+ popup), then rerun the command. Run browser-harness --doctor to diagnose connection issues. For headless servers or parallel runs, use a Browser Use Cloud browser instead (see below).

Both commands create an isolated browser-harness run workspace, present the browser-harness skill, and make ./bin/browser-harness available to the agent inside that workspace.

Once this branch is released to PyPI, the same commands work as browser-harness tui / browser-harness agent "…" from any install.

Building from source (optional)

The agent is vendored as the codex-agent git submodule. A locally-built binary takes precedence over the download, so contributors can:

git submodule update --init
cd codex-agent/codex-rs && cargo build --release -p codex-cli && cd ../..

Resolution order for the agent binary: explicit --codex-bin → a locally-built submodule binary → the cached/downloaded prebuilt release. No environment variables, no sibling-directory guessing.

Free Browser Use Cloud browsers

Stealth, sub-agents, or headless deployment.
Browser Use Cloud free tier: 3 concurrent browsers, proxies, captcha solving, and more. No card required.

• Grab a key at cloud.browser-use.com/new-api-key
• Or let the agent sign up itself via docs.browser-use.com/llms.txt (setup flow + challenge context included).

Architecture (~1k lines across 4 core files)

• install.md — first-time install and browser bootstrap
• SKILL.md — day-to-day usage
• src/browser_harness/ — protected core package
• ${XDG_CONFIG_HOME:-~/.config}/browser-harness/agent-workspace/agent_helpers.py — helper code the agent edits
• ${XDG_CONFIG_HOME:-~/.config}/browser-harness/agent-workspace/domain-skills/ — reusable site-specific skills the agent edits

Plain browser-harness helper calls attach to the running Chrome/Chromium CDP endpoint. For isolated automation, launch Chrome yourself with --remote-debugging-port and pass BU_CDP_URL, or use a Browser Use cloud browser.

Development

From a checkout, use ./browser-harness to run the current working tree without activating a virtualenv or depending on the globally installed command:

./browser-harness <<'PY'
print(page_info())
PY

Normal agent-facing docs should keep using browser-harness; the ./browser-harness launcher is only for local repo testing.

Contributing

PRs and improvements welcome. The best way to help: contribute a new domain skill under agent-workspace/domain-skills/ for a site or task you use often (LinkedIn outreach, ordering on Amazon, filing expenses, etc.). Each skill teaches the agent the selectors, flows, and edge cases it would otherwise have to rediscover.

• Skills are written by the harness, not by you. Just run your task with the agent — when it figures something non-obvious out, it files the skill itself (see SKILL.md). Please don't hand-author skill files; agent-generated ones reflect what actually works in the browser.
• Open a PR with the generated domain-skills/<site>/ folder copied into this repo's agent-workspace/domain-skills/ examples — small and focused is great.
• Bug fixes, docs tweaks, and helper improvements are equally welcome.
• Browse existing skills (github/, linkedin/, amazon/, ...) to see the shape.

If you're not sure where to start, open an issue and we'll point you somewhere useful.

Domain skills

Set BH_DOMAIN_SKILLS=1 to enable domain skills from the agent workspace. This repo's agent-workspace/domain-skills/ directory contains examples to contribute via PR.

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The Bitter Lesson of Agent Harnesses · Web Agents That Actually Learn