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 marchatton/agent-skills --skill test-browsergit clone --depth 1 https://github.com/marchatton/agent-skillsWrote 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/marchatton/agent-skills/test-browser)<a href="https://agentmods.dev/skills/marchatton/agent-skills/test-browser"><img src="https://agentmods.dev/badge/skills/marchatton/agent-skills/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/marchatton/agent-skills/test-browser"><img src="https://agentmods.dev/badge/skills/marchatton/agent-skills/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 | $0.00022 | $0.01964 |
| Opus 5 | $0.00011 | $0.00982 |
| Sonnet 5 | $0.00004 | $0.00393 |
| Haiku 4.5 | $0.00002 | $0.00196 |
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 7d 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.
How it starts
The opening of the file, as written. The whole thing — 322 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Browser Test Command
Run end-to-end browser tests on pages affected by a PR or branch changes using agent-browser CLI.
CRITICAL: Use agent-browser CLI Only
DO NOT use Chrome MCP tools (mcp__claude-in-chrome__*).
This command uses the agent-browser CLI exclusively. The agent-browser CLI is a Bash-based tool from Vercel that runs headless Chromium. It is NOT the same as Chrome browser automation via MCP.
If you find yourself calling mcp__claude-in-chrome__* tools, STOP. Use agent-browser Bash commands instead.
Introduction
Role: QA Engineer specializing in browser-based end-to-end testing
This command tests affected pages in a real browser, catching issues that unit tests miss:
- JavaScript integration bugs
- CSS/layout regressions
- User workflow breakages
- Console errors
Prerequisites
- Local development server running (e.g.,
bin/dev,rails server,npm run dev) - agent-browser CLI installed (see Setup below)
- Git repository with changes to test
Setup
Check installation:
command -v agent-browser >/dev/null 2>&1 && echo "Installed" || echo "NOT INSTALLED"
Install if needed:
npm install -g agent-browser
agent-browser install # Downloads Chromium (~160MB)
See the CLI reference below for detailed usage.
Main Tasks
0. Verify agent-browser Installation
Before starting ANY browser testing, verify agent-browser is installed:
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.
1. Ask Browser Mode
Before starting tests, ask user if they want to watch the browser:
Use ask-questions-if-underspecified with:
- Question: "Do you want to watch the browser tests run?"
- Options:
- Headed (watch) - Opens visible browser window so you can see tests run
- Headless (faster) - Runs in background, faster but invisible
Store the choice and use --headed flag when user selects "Headed".
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.
- 7d ago First seen · 322 lines · 22 tokens per session scan A f7a4a4d8c8a0
test-browser is a skill published in the GitHub repository marchatton/agent-skills (5 stars, last pushed 6mo ago), licensed MIT. It adds 22 tokens to every session and 1,964 once invoked, about $0.0001 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-03.
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).
playwright-cli
A command-line tool for controlling Chromium, Firefox, and WebKit browsers, including navigation, page interaction, screenshots, PDFs, and recorded actions.
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.
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.
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…