Codex Buddy For Claude

MCP server that gives Claude Code access to OpenAI models for:

• Code Review (codex_review) — expert code review with severity ratings and actionable fixes
• Deep Thinking (codex_thinkdeep) — architecture decisions, trade-off analysis, debugging hypotheses
• Security Audit (codex_secaudit) — OWASP-aligned security audit with threat-level-aware analysis

Reports are automatically saved as markdown files to <project>/codex-reports/.

Requirements

• Python 3.10+
• Either an OpenAI API key (pay-per-token) or a ChatGPT Plus/Pro subscription (flat monthly fee)

Install

# Clone the repo
git clone https://github.com/leo919cc/codex-buddy-for-claude.git
cd codex-buddy-for-claude

# Create venv and install dependencies
python3 -m venv .venv
source .venv/bin/activate
pip install -r requirements.txt

Add to Claude Code

Add the server to your Claude Code MCP config (~/.claude.json):

{
  "mcpServers": {
    "codexreview": {
      "command": "/absolute/path/to/codex-buddy-for-claude/.venv/bin/python",
      "args": ["/absolute/path/to/codex-buddy-for-claude/server.py"]
    }
  }
}

Replace /absolute/path/to/ with the actual path where you cloned the repo.

Then restart Claude Code. You should see the three tools available:

• mcp__codexreview__codex_review
• mcp__codexreview__codex_thinkdeep
• mcp__codexreview__codex_secaudit

Authentication

The server supports two auth methods. It prefers OAuth (free with subscription) and falls back to API key (pay-per-token).

Option A: ChatGPT subscription (recommended)

Use your ChatGPT Plus ($20/mo) or Pro ($200/mo) subscription — no per-token API costs.

# Install Codex CLI and login (one-time)
npm install -g @openai/codex
codex login

This saves OAuth tokens to ~/.codex/auth.json. The MCP server auto-detects them on startup. The report footer will show (subscription) to confirm.

Option B: API key (pay-per-token)

Create a .env file in the repo directory:

echo "OPENAI_API_KEY=sk-your-key-here" > .env

Or export it in your shell:

export OPENAI_API_KEY=sk-your-key-here

The report footer will show (API) when using this method.

Both configured?

If both OAuth and API key are available, OAuth is used by default (free). The API key serves as fallback if OAuth tokens expire or fail.

Configuration

Env Variable	Default	Description
OPENAI_API_KEY	(optional if using OAuth)	Your OpenAI API key
CODEX_MODEL	gpt-5.4	Default model for all tools

You can also override the model per-call by passing the model parameter to any tool.

Supported models

Any OpenAI model works. High-reasoning models (codex/5.x series) automatically use the Responses API:

• gpt-5.4 (default) — high reasoning
• gpt-5.4-pro — xhigh reasoning (premium pricing)
• gpt-5.3-codex, gpt-5.2-codex, gpt-5.1-codex, etc.
• gpt-4o, gpt-4-turbo, etc. — use standard chat completions API

Usage

Once configured, Claude Code will automatically have access to the tools. You can ask Claude to:

• "Review this file" → triggers codex_review
• "Think deeply about whether we should use X or Y" → triggers codex_thinkdeep
• "Run a security audit on this file" → triggers codex_secaudit

Parameters

All tools accept:

• model — override the default model
• project_dir — where to save reports (auto-detected from file paths if not set)

codex_review

• files (required) — list of absolute file paths
• context — what the code does, focus areas

codex_thinkdeep

• problem (required) — the question or decision to analyze
• context — constraints, what you've considered
• files — relevant code files for grounding

codex_secaudit

• files (required) — list of absolute file paths
• context — deployment context, threat model
• threat_level — low | medium | high | critical

License

MIT