Codex MCP Server

MCP server connecting Claude/Cursor to Codex CLI. Enables code analysis via @ file references, multi-turn conversations, sandboxed edits, and structured change mode.

Features

• File Analysis — Reference files with @src/, @package.json syntax
• Multi-Turn Sessions — Conversation continuity with workspace isolation
• Native Resume — Uses codex resume for context preservation (CLI v0.36.0+)
• Local OSS Models — Run with Ollama or LM Studio via localProvider
• Web Search — Research capabilities with search: true
• Sandbox Mode — Safe automation with explicit sandbox and approval policies
• Change Mode — Structured OLD/NEW patch output for refactoring
• Brainstorming — SCAMPER, design-thinking, lateral thinking frameworks
• Health Diagnostics — CLI version, features, and session monitoring
• Cross-Platform — Windows, macOS, Linux fully supported

Quick Start

claude mcp add codex-cli -- npx -y @trishchuk/codex-mcp-tool

Prerequisites: Node.js 18+, Codex CLI installed and authenticated.

Configuration

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

Config locations: macOS: ~/Library/Application Support/Claude/claude_desktop_config.json | Windows: %APPDATA%\Claude\claude_desktop_config.json

Usage Examples

// File analysis
'explain the architecture of @src/';
'analyze @package.json and list dependencies';

// With specific model
'use codex with model gpt-5.6-sol to analyze @algorithm.py';

// Multi-turn conversations (v1.4.0+)
'ask codex sessionId:"my-project" prompt:"explain @src/"';
'ask codex sessionId:"my-project" prompt:"now add error handling"';

// Brainstorming
'brainstorm ways to optimize CI/CD using SCAMPER method';

// Sandbox mode
'use codex sandbox:true to create and run a Python script';

// Web search
'ask codex search:true prompt:"latest TypeScript 5.7 features"';

// Local OSS model (Ollama)
'ask codex localProvider:"ollama" model:"qwen3:8b" prompt:"explain @src/"';

Tools

Models

By default the model parameter is omitted and Codex CLI applies the default model from your ~/.codex/config.toml (for example model = "gpt-5.6-sol"). Pass model only when you need to override the configured default for a single call. Reasoning depth is calibrated per tool:

• ask-codex — uses the Codex CLI default reasoning (medium). Increase it only when the task needs more planning or checking.
• brainstorm, do-act, review-changes — default reasoningEffort: "high" (creative ideation, act-check-fix loops, and code review benefit from deeper reasoning).

GPT-6 Astra and GPT-5.6 Sol/Terra expose max and ultra reasoning; Luna tops out at max. ultra may delegate work to subagents; most tasks should remain on medium or high. Pass a concrete slug — the bare moving aliases gpt-6 and gpt-5.6 are rejected by the API.

Key Features

Session Management (v1.4.0+)

Multi-turn conversations with workspace isolation:

{ "prompt": "analyze code", "sessionId": "my-session" }
{ "prompt": "continue from here", "sessionId": "my-session" }
{ "prompt": "start fresh", "sessionId": "my-session", "resetSession": true }

Environment:

• CODEX_SESSION_TTL_MS - Session TTL (default: 24h)
• CODEX_MAX_SESSIONS - Max sessions (default: 50)

Codex CLI version

Requires Codex CLI 0.95.0 or newer. On older versions the server fails with an explicit upgrade message rather than silently dropping unsupported flags. Upgrade with npm install -g @openai/codex@latest; run the health tool to see the detected version.

Troubleshooting: "codex not found"

MCP clients launched from a GUI (Dock, Finder, Start menu) inherit a minimal PATH that excludes Homebrew, nvm, and volta directories, so codex may work from a terminal but not from the app. The server searches those locations automatically; if it still cannot find the CLI, pin it explicitly:

{ "env": { "CODEX_CLI_PATH": "/opt/homebrew/bin/codex" } }

Find the value with which codex. Run the health tool to see which executable was resolved and how.

Local OSS Models (v1.6.0+)

Run with local Ollama or LM Studio instead of OpenAI:

// Ollama
{ "prompt": "analyze @src/", "localProvider": "ollama", "model": "qwen3:8b" }

// LM Studio
{ "prompt": "analyze @src/", "localProvider": "lmstudio", "model": "my-model" }

// Auto-select provider
{ "prompt": "analyze @src/", "oss": true }

Requirements: Ollama running locally with a model that supports tool calling (e.g. qwen3:8b).

Advanced Options

CLI Compatibility

Validated against Codex CLI 0.144.3. The server keeps older feature guards, but current releases are recommended. Notable current behavior:

• --full-auto and approval policy on-failure have been removed by Codex CLI.
• MCP sandbox: true / fullAuto: true remain compatibility aliases for --sandbox workspace-write --ask-for-approval never; they do not bypass the sandbox.
• Native --search is used without the deprecated web_search_request feature.
• Current exec flags include --strict-config, --ephemeral, --ignore-user-config, and --ignore-rules.

Troubleshooting

codex --version    # Check CLI version
codex login        # Authenticate

Use health tool for diagnostics: 'use health verbose:true'

Migration

v2.4.x → v2.5.0: Codex CLI 0.153.4 compatibility pass; added gpt-6-astra. Breaking: dropped gpt-5.4 and the moving alias gpt-5.6 (both now rejected with HTTP 400), and removed the untrusted approval policy, which Codex CLI 0.153.x no longer parses.

v2.3.x → v2.4.0: Codex CLI 0.144.3 compatibility audit; added GPT-5.6 Sol/Terra/Luna, max/ultra reasoning, current exec flags, native-only search, and safe compatibility handling for the removed --full-auto flag and on-failure approval policy.

v2.2.x → v2.3.0: gpt-5.5 as new default, added gpt-5.4-mini, dropped retired models (gpt-5.3-codex-spark, gpt-5.2-codex, gpt-5.1-codex-max, gpt-5.1-codex-mini).

v2.0.x → v2.1.0: gpt-5.4 as new default model, updated fallback chain.

v1.5.x → v1.6.0: Local OSS model support (localProvider, oss), gpt-5.3-codex default model, xhigh reasoning effort.

v1.3.x → v1.4.0: New sessionId parameter, list-sessions/health tools, structured error handling. No breaking changes.

License

MIT License. Not affiliated with OpenAI.

Documentation | Issues | Inspired by jamubc/gemini-mcp-tool