What is big-brain CLAUDE.md?

Project instructions for BigBrain, including how to test its ChatGPT Desktop mode and direct MCP mode. MCP is a way for an AI assistant to call a program's tools.

It helps run automated ChatGPT Desktop tests, direct MCP tests, and the MCP Inspector, with options for terminals, loops, sounds, and notifications.

It gives developers the required setup, commands, and options for checking that BigBrain works.

How probelabs/big-brain configures Claude Code

Reuse

Borrowing it

Nothing to install: this file belongs to probelabs/big-brain. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.

Copy the file

curl -O https://raw.githubusercontent.com/probelabs/big-brain/main/CLAUDE.md

Clone the repo

git clone --depth 1 https://github.com/probelabs/big-brain

Made for: Claude Code.

Wrote 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.

README.md

[![agentmods](https://agentmods.dev/badge/instructions/probelabs/big-brain/claude-md/github.svg)](https://agentmods.dev/instructions/probelabs/big-brain/claude-md)

Your own site

<a href="https://agentmods.dev/instructions/probelabs/big-brain/claude-md"><img src="https://agentmods.dev/badge/instructions/probelabs/big-brain/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.

Your own site · 80×15

<a href="https://agentmods.dev/instructions/probelabs/big-brain/claude-md"><img src="https://agentmods.dev/badge/instructions/probelabs/big-brain/claude-md.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 864 This file is loaded in full into every session.

When invoked 864 The same file — it is already loaded in full.

Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.

Origin original No closer match found 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.

Model	Per session	Once invoked
Fable 5.1	$0.00864	$0.00864
Opus 5.5	$0.00346	$0.00346
Sonnet 5.5	$0.00173	$0.00173
Haiku 4.5	$0.00086	$0.00086

Measured 2mo ago against content hash 8af04b8f32dc, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

big-brain 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 2mo 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.

CLAUDE.md · 107 lines

How it starts

The opening of the file, as written. The whole thing — 107 lines — stays where its author put it; the contents beside it link to each section on GitHub.

BigBrain Project Documentation

Testing BigBrain

Testing ChatGPT Mode

The ChatGPT mode allows BigBrain to automatically query ChatGPT Desktop and return responses without manual intervention.

Prerequisites

ChatGPT Desktop app must be installed (https://chatgpt.com/desktop)
macOS accessibility permissions must be granted to Terminal

Running Tests

Test ChatGPT Mode Directly

node scripts/tests/test_chatgpt_mode.js

This will:

Start BigBrain with --chatgpt flag
Send a test question via MCP protocol
Automatically query ChatGPT Desktop
Return the response (takes 30-60 seconds)

Test Manual Mode (Default)

node scripts/tests/test_mcp_direct.js

Test with MCP Inspector

npm run inspector -- --chatgpt

Then use the web UI to call the ask_big_brain tool.

Available Command-Line Flags

--chatgpt - Enable automatic ChatGPT Desktop integration
--terminal <app> - Specify terminal app for ChatGPT mode (Terminal, iTerm, Warp, Alacritty)
--loop <prompt> - Enable loop mode for multi-agent systems
--disable-sound - Disable sound notifications
--disable-notification - Disable dialog notifications
--max-tokens <number> - Set custom token limit (default: 40000)

Testing Workflow

Build the project: npm run build
Copy UI reader to build: cp scripts/chatgpt/chatgpt_ui_reader_ultrafast.js build/
Run test: node scripts/tests/test_chatgpt_mode.js

Deployment

Cloudflare Pages Deployment

To deploy the website to Cloudflare Pages and make it available at https://probelabs.com/big-brain/:

1. Deploy the Site

npx wrangler pages deploy site/ --project-name big-brain

2. Get the Latest Deployment URL

npx wrangler pages deployment list --project-name big-brain

Copy the latest deployment URL (e.g., https://ea82634b.big-brain-cyt.pages.dev)

3. Update Worker with Latest URL

Edit worker.js line 10 to use the latest deployment URL:

const pagesUrl = `https://[latest-hash].big-brain-cyt.pages.dev${newPath}${url.search}`;

Read the full file on GitHub · 107 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.

2mo ago First seen · 107 lines · 864 tokens per session scan A 8af04b8f32dc

Subscribe to this mod's changes

big-brain CLAUDE.md is an instructions file published in the GitHub repository probelabs/big-brain (4 stars, last pushed 1y ago), licensed MIT. It adds 864 tokens to every session, about $0.0035 per session on Opus 5.5. 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.

ai artificial-intelligence claude context-extraction cursor mcp

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big-brain: Instructions file for Claude Code