Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
npx skills add Jerrylalala/compound-engineering --skill test-browsergit clone --depth 1 https://github.com/Jerrylalala/compound-engineeringWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/jerrylalala/compound-engineering/test-browser)<a href="https://agentmods.dev/skills/jerrylalala/compound-engineering/test-browser"><img src="https://agentmods.dev/badge/skills/jerrylalala/compound-engineering/test-browser/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/jerrylalala/compound-engineering/test-browser"><img src="https://agentmods.dev/badge/skills/jerrylalala/compound-engineering/test-browser.svg" alt="Reviewed on agentmods" width="80" height="20"></a>What it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00014 | $0.02314 |
| Opus 5.5 | $0.00006 | $0.00926 |
| Sonnet 5.5 | $0.00003 | $0.00463 |
| Haiku 4.5 | $0.00001 | $0.00231 |
Grade A, and why
test-browser scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 1mo ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
This is a copy
98% identical to test-browser — 4 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.
How it starts
The opening of the file, as written. The whole thing — 317 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Browser Test Skill
Run end-to-end browser tests on pages affected by a PR or branch changes using the agent-browser CLI.
Use agent-browser Only For Browser Automation
This workflow uses the agent-browser CLI exclusively. Do not use any alternative browser automation system, browser MCP integration, or built-in browser-control tool. If the platform offers multiple ways to control a browser, always choose agent-browser.
Use agent-browser for: opening pages, clicking elements, filling forms, taking screenshots, and scraping rendered content.
Platform-specific hints:
- In Claude Code, do not use Chrome MCP tools (
mcp__claude-in-chrome__*). - In Codex, do not substitute unrelated browsing tools.
Prerequisites
- Local development server running (e.g.,
bin/dev,rails server,npm run dev) agent-browserCLI installed (see Setup below)- Git repository with changes to test
Setup
command -v agent-browser >/dev/null 2>&1 && echo "Installed" || echo "NOT INSTALLED"
Install if needed:
npm install -g agent-browser
agent-browser install
See the agent-browser skill for detailed usage.
Workflow
1. Verify Installation
Before starting, verify agent-browser is available:
command -v agent-browser >/dev/null 2>&1 && echo "Ready" || (echo "Installing..." && npm install -g agent-browser && agent-browser install)
If installation fails, inform the user and stop.
2. Ask Browser Mode
Ask the user whether to run headed or headless (using the platform's question tool — e.g., AskUserQuestion in Claude Code, request_user_input in Codex, ask_user in Gemini — or present options and wait for a reply):
Do you want to watch the browser tests run?
1. Headed (watch) - Opens visible browser window so you can see tests run
2. Headless (faster) - Runs in background, faster but invisible
Store the choice and use the --headed flag when the user selects option 1.
3. Determine Test Scope
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- 1mo ago First seen · 317 lines · 14 tokens per session scan A 292f16327520
test-browser is a skill published in the GitHub repository Jerrylalala/compound-engineering (6 stars, last pushed 4mo ago), licensed MIT. It adds 14 tokens to every session and 2,314 once invoked, about $0.0001 per session on Opus 5.5. A static security scan graded it A with 0 findings. It is 98% identical to test-browser, differing in 4 lines, and is treated as a copy.
Other skills, from other repositories
browse
Drive a real browser through Aside: open a page, read it, click through a flow, take screenshots, check console errors. (gstack).
cua-driver
Use Cua Driver for desktop or browser tasks that are awkward or unavailable through Bash/APIs, or when the user explicitly wants GUI interaction: app testing, visual bug reproduction, form filling, calendar entry, screenshots, and demo recording. Also covers Cua setup; not OpenAI Codex Computer Use or web research.
create-verification-skill
Create a repo-local verification skill and exhaustive feature map for driving a real app through its UI, CLI, or API. Use for "create a verification skill", "make a verify skill for this repo", or "document how agents can verify this app".
browser-qa
A browser-based quality check for deployed web pages and user flows. It uses browser automation to test rendering, navigation, forms, interactions, responsive behaviour, and accessibility-related issues.
webapp-testing
Toolkit for interacting with and testing local web applications using Playwright. Supports verifying frontend functionality, debugging UI behavior, capturing browser screenshots, and viewing browser logs.
test-electron-app
Drive the real running PostHog Electron app (live tRPC, workspace-server, real data) over CDP with agent-browser. Connect to the running app on port 9222, test desktop changes against a local Django stack, snapshot the accessibility tree, inspect network requests, and screenshot only when explicitly asked. Use when…