Borrowing it
Nothing to install: this file belongs to zbrooklyn-claude-labs/playwright-pool. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.
curl -O https://raw.githubusercontent.com/zbrooklyn-claude-labs/playwright-pool/master/CLAUDE.mdgit clone --depth 1 https://github.com/zbrooklyn-claude-labs/playwright-poolWrote 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/instructions/zbrooklyn-claude-labs/playwright-pool/claude-md)<a href="https://agentmods.dev/instructions/zbrooklyn-claude-labs/playwright-pool/claude-md"><img src="https://agentmods.dev/badge/instructions/zbrooklyn-claude-labs/playwright-pool/claude-md/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/instructions/zbrooklyn-claude-labs/playwright-pool/claude-md"><img src="https://agentmods.dev/badge/instructions/zbrooklyn-claude-labs/playwright-pool/claude-md.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 | $0.00499 | $0.00499 |
| Opus 5 | $0.00249 | $0.00249 |
| Sonnet 5 | $0.00100 | $0.00100 |
| Haiku 4.5 | $0.00050 | $0.00050 |
Grade A, and why
playwright-pool CLAUDE.md 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 8d 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 — 43 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Playwright Pool — Project Rules
Overview
MCP server that dynamically manages authenticated Playwright browser pools from a single golden profile.
Branch Rules
mainis the default branch- Feature work on feature branches, merge via PR
Key Files
server.js— the entire MCP server (single file)package.json— dependencies and metadataREADME.md— public documentation
Testing
No automated tests yet. Manual testing:
- Configure in
.mcp.json - Launch windows via
pool_launch - Verify auth with
pool_navigateto authenticated pages - Verify cleanup with
pool_close all
Core Design Principle: Visual Truth
The rendered UI is the source of truth, not the source code. All audit tools must prioritize what the user actually sees over what the code says should happen.
Three-Layer Audit Rule — all three must agree before any UI claim:
- Code check (what the CSS/HTML says)
- Programmatic measurement (what the browser computed —
getComputedStyle,getBoundingClientRect) - Visual verification (screenshot — what the user actually sees)
Code saying padding: 16px means nothing if a conflicting style makes the visual result wrong. When building audit tools, always verify against the rendered output, not just the DOM/CSS.
Performance Guidelines
- Prefer CLI for audits and screenshots — saves context tokens (~20 tokens for a file path vs ~28,000 for a full snapshot)
- Use MCP for interactive browser sessions (clicking, navigating, reacting to page state)
- Always use
snapshot_compactoverbrowser_snapshot— 20x fewer tokens (~1,375 vs ~28,000) - First
pool_launchhas ~17s overhead (template creation); subsequent operations are fast (<2s)
Architecture Decisions
- Auth overlay, not full profile copy — copying entire Chromium profiles causes crashes due to cache/GPU data tied to specific Chromium builds. We create a fresh profile and overlay only the 13 auth-critical files.
- Template caching — the first
pool_launchcreates a template profile (one headless Chromium launch). Subsequent launches just copy the template (filesystem only, no Chromium launch). - UUID session isolation — each MCP server process gets a random UUID prefix. Concurrent sessions never collide on disk.
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.
- 8d ago First seen · 43 lines · 499 tokens per session scan A 31e303fe518a
playwright-pool CLAUDE.md is an instructions file published in the GitHub repository zbrooklyn-claude-labs/playwright-pool (0 stars, last pushed 2mo ago), licensed MIT. It adds 499 tokens to every session, about $0.0025 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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