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/tommymorgan/claude-plugins/browser-testing-patternsnpx skills add tommymorgan/claude-plugins --skill browser-testing-patternsgit clone --depth 1 https://github.com/tommymorgan/claude-pluginsWhat 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 | $0.00058 | $0.02566 |
| Opus 5 | $0.00029 | $0.01283 |
| Sonnet 5 | $0.00012 | $0.00513 |
| Haiku 4.5 | $0.00006 | $0.00257 |
Grade A, and why
Browser Testing Patterns 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.
How it starts
The opening of the file, as written. The whole thing — 396 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Browser Testing Patterns
Purpose
Provide systematic patterns and best practices for autonomous browser-based exploratory testing using CLI tools. Guide agents through comprehensive web application testing including functional validation, visual inspection, accessibility compliance, and performance measurement.
Tools
Browser testing uses three tools, each for a specific purpose:
| Tool | Purpose | Required |
|---|---|---|
| agent-browser | Primary browser automation | Always |
| playwright-cli | Video demo recording | Only when video requested |
| chrome-devtools-mcp | Deep performance profiling | Only for performance scenarios |
See testing/README.md for installation instructions.
Shell Safety
CLI commands run through Bash. Always quote user-controlled values to prevent shell injection:
# CORRECT — all values quoted
agent-browser -s=my-session open "https://example.com/path?q=search term"
agent-browser -s=my-session fill @e3 "user's input value"
agent-browser -s=my-session eval "document.querySelector('.class').textContent"
# INCORRECT — unquoted values risk injection
agent-browser open $url
agent-browser fill @ref $text
agent-browser eval $script
Rules:
- Always double-quote URLs, form values, JavaScript expressions, and selectors
- Never interpolate unquoted variables into commands
- This applies to all values from plan files, user input, or page content
Core Testing Methodology
Systematic Exploration Approach
Test web applications using a structured layered approach:
- Pre-flight check: Verify agent-browser is installed and functional
- Initial reconnaissance: Navigate to target, capture state
- Functional testing: Interact with elements, test workflows
- Accessibility validation: Check WCAG compliance
- Performance measurement: Analyze Core Web Vitals
- Visual inspection: Detect layout issues
- Session cleanup: Close browser sessions
- Reporting: Categorize and document findings
What ships with it
4 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.
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 · 396 lines · 58 tokens per session scan A 8dcb3f155fe3
Browser Testing Patterns is a skill published in the GitHub repository tommymorgan/claude-plugins (4 stars, last pushed 1mo ago), licensed MIT. It adds 58 tokens to every session and 2,566 once invoked, about $0.0003 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 2026-08-31.
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