test-browser

A command that runs end-to-end browser tests on pages affected by a pull request or branch. End-to-end tests check complete user actions in a real browser.

In plain words
What is it for?
Use it to test affected web pages with the `agent-browser` command-line tool and headless Chromium, a browser that runs without a visible window.
Why use it?
It can reveal JavaScript integration problems, visual layout changes, broken workflows, and browser console errors that smaller code tests may miss.

Command

Install

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.

agentmods
npx agentmods add commands/aegntic/compound-engineering/test-browser
Clone the repo
git clone --depth 1 https://github.com/aegntic/compound-engineering
Per session 14 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 2,049 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin 86% copy Near-identical to another mod in the catalogue.
Token cost

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.

ModelPer sessionOnce invoked
Fable 5 $0.00014 $0.02049
Opus 5 $0.00007 $0.01025
Sonnet 5 $0.00003 $0.00410
Haiku 4.5 $0.00001 $0.00205

Measured yesterday against content hash e4357d90bdd0, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

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 yesterday.

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.

Origin

This is a copy

86% identical to test-browser — 31 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.

commands/test-browser.md · 333 lines

How it starts

The opening of the file, as written. The whole thing — 333 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Browser Test Command

<command_purpose>Run end-to-end browser tests on pages affected by a PR or branch changes using agent-browser CLI.</command_purpose>

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

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

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 agent-browser skill 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

<ask_browser_mode>

Before starting tests, ask user if they want to watch the browser:

Use AskUserQuestion with:

  • Question: "Do you want to watch the browser tests run?"
  • Options:
    1. Headed (watch) - Opens visible browser window so you can see tests run
    2. Headless (faster) - Runs in background, faster but invisible

Read the full file on GitHub · 333 lines

Changes

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.

  1. yesterday First seen · 333 lines · 14 tokens per session scan A e4357d90bdd0

Subscribe to this mod's changes

test-browser is a command published in the GitHub repository aegntic/compound-engineering (2 stars, last pushed 2mo ago), licensed MIT. It adds 14 tokens to every session and 2,049 once invoked, about $0.0001 per session on Opus 5. A static security scan graded it A with 0 findings. It is 86% identical to test-browser, differing in 31 lines, and is treated as a copy.