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 agentmods add skills/marcusrbrown/systematic/test-browsernpx skills add marcusrbrown/systematic --skill test-browsergit clone --depth 1 https://github.com/marcusrbrown/systematicWhat 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 | $0.00014 | $0.02376 |
| Opus 5 | $0.00007 | $0.01188 |
| Sonnet 5 | $0.00003 | $0.00475 |
| Haiku 4.5 | $0.00001 | $0.00238 |
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 2d 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
88% identical to test-browser — 30 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 OpenCode, 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
Check whether agent-browser is installed:
command -v agent-browser >/dev/null 2>&1 && echo "Installed" || echo "NOT INSTALLED"
If not installed, inform the user: "agent-browser is not installed. Install it with npm install -g agent-browser." Then stop — this skill cannot function without agent-browser.
Workflow
1. Verify Installation
Before starting, verify agent-browser is available:
command -v agent-browser >/dev/null 2>&1 && echo "Ready" || echo "NOT INSTALLED"
If not installed, inform the user: "agent-browser is not installed. Install it with npm install -g agent-browser." Then stop.
2. Ask Browser Mode
Ask the user whether to run headed or headless (using the platform's question tool — e.g., question in OpenCode, request_user_input in Codex, ask_user in Gemini; in Pi, use the blocking-question extension if available, otherwise present numbered options in chat and wait — 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
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.
- 2d ago First seen · 317 lines · 14 tokens per session scan A ffa33e3b86cd
test-browser is a skill published in the GitHub repository marcusrbrown/systematic (24 stars, last pushed 3d ago), licensed MIT. It adds 14 tokens to every session and 2,376 once invoked, about $0.0001 per session on Opus 5. A static security scan graded it A with 0 findings. It is 88% identical to test-browser, differing in 30 lines, and is treated as a copy.
Other skills, from other repositories
plan-protocol
Guidelines for creating and managing implementation plans with citations.
plan-review
Criteria for reviewing implementation plans against quality standards.
code-review
Comprehensive code review methodology with severity classification and confidence thresholds.
code-philosophy
Internal logic and data flow philosophy (The 5 Laws of Elegant Defense). Understand deeply to ensure code guides data naturally and prevents errors.
frontend-philosophy
Visual & UI philosophy (The 5 Pillars of Intentional UI). Understand deeply to avoid "AI slop" and create distinctive, memorable interfaces.
opencode-ensemble
Use when coordinating multiple coding agents, delegating independent software work, managing OpenCode Ensemble teams, choosing teammate roles or models, reviewing teammate output, or deciding whether parallel execution is appropriate.