Borrowing it
Nothing to install: this file belongs to opentabs-dev/opentabs. 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/opentabs-dev/opentabs/main/CLAUDE.mdgit clone --depth 1 https://github.com/opentabs-dev/opentabsWrote 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/opentabs-dev/opentabs/claude-md)<a href="https://agentmods.dev/instructions/opentabs-dev/opentabs/claude-md"><img src="https://agentmods.dev/badge/instructions/opentabs-dev/opentabs/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/opentabs-dev/opentabs/claude-md"><img src="https://agentmods.dev/badge/instructions/opentabs-dev/opentabs/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 | $0.06529 | $0.06529 |
| Opus 5.5 | $0.02612 | $0.02612 |
| Sonnet 5.5 | $0.01306 | $0.01306 |
| Haiku 4.5 | $0.00653 | $0.00653 |
Grade A, and why
opentabs CLAUDE.md scanned grade A with 1 finding 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 1mo 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.
Runs shell commandslowCapability
Expected in a hook, worth knowing in a rule or an instructions file.
**Production code** (`platform/*/src/`): Uses Node.js APIs directly (`node:fs/promises`, `node:child_process`, `node:crypto`, `process.env`, `process.argv`). This is a copy
88% identical to opentabs AGENTS.md — 66 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 — 431 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Project Instructions for Claude
Project Overview
OpenTabs Platform is a Chrome extension + MCP server with a plugin-based architecture. A plugin SDK allows anyone to create OpenTabs plugins as standalone npm packages. The MCP server discovers plugins at runtime, and the Chrome extension dynamically injects plugin adapters into matching tabs — giving AI agents access to web applications through the user's authenticated browser session.
Architecture
┌─────────────┐ Streamable HTTP ┌─────────────┐ WebSocket ┌──────────────────┐
│ Claude Code │ ←───────────────→ │ MCP Server │ ←─────────→ │ Chrome Extension │
│ │ /mcp │ (localhost) │ │ (Background) │
└─────────────┘ └──────┬──────┘ └────────┬─────────┘
│ │
┌──────▼──────┐ ┌────────▼─────────┐
│ Plugin │ │ Adapter IIFEs │
│ Discovery │ │ (per plugin, │
│ (npm + local│ │ injected into │
│ paths) │ │ matching tabs) │
└─────────────┘ └────────┬─────────┘
│ Same-origin
┌────────▼─────────┐
│ Web APIs │
│ (user's session) │
└──────────────────┘
MCP Server (platform/mcp-server): Plugin discovery, tool dispatch via WebSocket, browser tools, audit log. See platform/mcp-server/CLAUDE.md for details.
Chrome Extension (platform/browser-extension): Adapter injection, tool dispatch relay, React side panel UI. Published to npm as @opentabs-dev/browser-extension and bundled as a CLI dependency so opentabs start can auto-install it. See platform/browser-extension/CLAUDE.md for details.
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.
- 1mo ago First seen · 431 lines · 6,529 tokens per session scan A 7473bbabb844
opentabs CLAUDE.md is an instructions file published in the GitHub repository opentabs-dev/opentabs (999 stars, last pushed 3d ago), licensed MIT. It adds 6,529 tokens to every session, about $0.0261 per session on Opus 5.5. A static security scan graded it A with 1 finding (runs shell commands). It is 88% identical to opentabs AGENTS.md, differing in 66 lines, and is treated as a copy.
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