Codex MCP Server

MCP server wrapper for the OpenAI Codex CLI that lets Claude Code (and any MCP‑compatible client) use Codex locally via stdio.

graph LR
    A[Claude Code / MCP Client] --> B[Codex MCP Server]

    B --> C[codex]
    B --> L[listTools]
    B --> S[listSessions]
    B --> X[deleteSession]
    B --> T[sessionStats]
    B --> P[ping]
    B --> H[help]
    B --> M[listModels]

    C --> F[Codex CLI]
    F --> G[OpenAI API]

    style A fill:#FF6B35
    style B fill:#4A90E2
    style C fill:#00D4AA
    style L fill:#00D4AA
    style S fill:#00D4AA
    style X fill:#00D4AA
    style T fill:#00D4AA
    style P fill:#00D4AA
    style H fill:#00D4AA
    style M fill:#00D4AA
    style F fill:#FFA500
    style G fill:#FF9500

Prerequisites

• OpenAI Codex CLI installed & configured
  • Install: npm i -g @openai/codex or brew install codex
  • Setup: codex login or set OPENAI_API_KEY
• Claude Code (or another MCP client)

Installation

One‑Click Installation

VS Code

VS Code Insiders

Cursor

Manual Installation

Claude Code (CLI)

claude mcp add codex-cli -- npx -y @comfucios/codex-mcp-server

Claude Desktop

Add to your Claude Desktop configuration file:

macOS: ~/Library/Application Support/Claude/claude_desktop_config.json
Windows: %APPDATA%/Claude/claude_desktop_config.json

{
  "mcpServers": {
    "codex-cli": {
      "command": "npx",
      "args": ["-y", "@comfucios/codex-mcp-server"]
    }
  }
}

Advanced Features & Tips

• Graceful shutdown — Handles SIGINT/SIGTERM so clients don’t see abrupt disconnects.
• Pagination — Large outputs are chunked; use nextPageToken/pageToken. Default size via CODEX_PAGE_SIZE.
• Session memory — Pass sessionId to keep context; sessions expire after CODEX_SESSION_TTL_MS and trim when exceeding CODEX_SESSION_MAX_BYTES.
• Tool discovery — Use listTools to get all tools with schemas (handy for client introspection).
• Image input — The codex tool supports image paths (single or array) for code/diagram analysis.
• Model control — Pass model to select gpt‑5 with reasoning effort: minimal, low, medium (default), high (e.g. "gpt-5 high").

Environment Variables

Configure via env vars (shell or .env):

• OPENAI_API_KEY — Required by Codex CLI unless you’ve run codex login.
• CODEX_PAGE_SIZE — Default page size (default: 40000, min 1000, max 200000).
• CODEX_SESSION_TTL_MS — Session time‑to‑live in ms (default: 3600000, i.e. 1 hour).
• CODEX_SESSION_MAX_BYTES — Max transcript bytes before trimming (default: 400000).

Troubleshooting

• Codex CLI not found
  • Install @openai/codex globally or via Homebrew.
  • Ensure codex --version works and the install directory is on your PATH.
• Missing API key
  • Run codex login or set OPENAI_API_KEY.
• No Codex config file
  • Create one in ~/.codex/config.toml|.yaml|.json (for use with listModels).
• Session expired
  • Sessions expire after CODEX_SESSION_TTL_MS. Use a new sessionId or increase TTL.
• Large output truncated
  • Use pageToken to fetch subsequent pages or raise CODEX_PAGE_SIZE.

Error format

All tools return consistent, structured errors:

{
  "isError": true,
  "content": [{ "type": "text", "text": "Error message here" }]
}

Usage with Claude Code

codex — AI coding assistant

Ask Codex to analyze code, generate solutions, or explain diagrams/images.

Common parameters

• prompt (string, required on first call unless paging)
• pageSize (number, optional)
• pageToken (string, optional)
• sessionId (string, optional)
• resetSession (boolean, optional)
• model (string, optional — "gpt-5 minimal|low|medium|high")
• image (string or string[])
• approvalPolicy, sandbox, workingDirectory, baseInstructions (advanced)

Examples

Basic:

{ "prompt": "Explain this TypeScript function" }

Image input:

{ "prompt": "Explain this diagram", "image": "diagram.png" }

Advanced options:

{
  "prompt": "Run this code in a sandbox",
  "sandbox": true,
  "workingDirectory": "/tmp/safe",
  "baseInstructions": "Always comment code."
}

Other tools

• listSessions — list active sessions (with metadata)
• deleteSession — delete a session by ID
• sessionStats — detailed stats for a session
• listModels — list models discovered from your ~/.codex config
• listTools — machine‑readable tool list & schemas
• ping — echo test
• help — codex --help passthrough

Example Workflows

Code analysis

Use the codex tool to review this TypeScript function and suggest improvements

Bug fixing

Use codex to help debug this error: [error message]

Code generation

Ask codex to create a React component that handles file uploads

Paging

1. First call:

{ "tool": "codex", "prompt": "...", "pageSize": 10000 }

2. Next page:

{ "tool": "codex", "pageToken": "<nextPageToken>" }

Development

# Install dependencies
npm install

# Development mode
npm run dev

# Build
npm run build

# Start built server
npm start

Testing & Quality

Uses Jest (unit + light integration).

npm test

See docs/tools.md, docs/usage.md, and docs/configuration.md for details.