Codex Octopus

[Codex Octopus]

Codex Octopus

One brain, many arms.

An MCP server that wraps the OpenAI Codex SDK, letting you run multiple specialized Codex agents — each with its own model, sandbox, effort, and personality — from any MCP client.

Why

Codex is powerful. But one instance does everything the same way. Sometimes you want a strict code reviewer in read-only sandbox. A test writer with workspace-write access. A cheap quick helper on minimal effort. A deep thinker on xhigh.

Codex Octopus lets you spin up as many of these as you need. Same binary, different configurations. Each one shows up as a separate tool in your MCP client.

Prerequisites

• Node.js >= 18
• Codex CLI — the Codex SDK spawns the Codex CLI under the hood, so you need it installed (@openai/codex)
• OpenAI API key (CODEX_API_KEY env var) or inherited from parent process

Install

npm install codex-octopus

Or use npx directly in your .mcp.json (see Quick Start below).

Quick Start

Add to your .mcp.json:

{  "mcpServers": {    "codex": {      "command": "npx",      "args": ["codex-octopus@latest"],      "env": {        "CODEX_SANDBOX_MODE": "workspace-write",        "CODEX_APPROVAL_POLICY": "never"      }    }  }}

This gives you two tools: codex and codex_reply. That's it — you have Codex as a tool.

Multiple Agents

The real power is running several instances with different configurations:

{  "mcpServers": {    "code-reviewer": {      "command": "npx",      "args": ["codex-octopus@latest"],      "env": {        "CODEX_TOOL_NAME": "code_reviewer",        "CODEX_SERVER_NAME": "code-reviewer",        "CODEX_DESCRIPTION": "Strict code reviewer. Read-only sandbox.",        "CODEX_MODEL": "o3",        "CODEX_SANDBOX_MODE": "read-only",        "CODEX_APPEND_INSTRUCTIONS": "You are a strict code reviewer. Report real bugs, not style preferences.",        "CODEX_EFFORT": "high"      }    },    "test-writer": {      "command": "npx",      "args": ["codex-octopus@latest"],      "env": {        "CODEX_TOOL_NAME": "test_writer",        "CODEX_SERVER_NAME": "test-writer",        "CODEX_DESCRIPTION": "Writes thorough tests with edge case coverage.",        "CODEX_MODEL": "gpt-5-codex",        "CODEX_SANDBOX_MODE": "workspace-write",        "CODEX_APPEND_INSTRUCTIONS": "Write tests first. Cover edge cases. TDD."      }    },    "quick-qa": {      "command": "npx",      "args": ["codex-octopus@latest"],      "env": {        "CODEX_TOOL_NAME": "quick_qa",        "CODEX_SERVER_NAME": "quick-qa",        "CODEX_DESCRIPTION": "Fast answers to quick coding questions.",        "CODEX_EFFORT": "minimal"      }    }  }}

Your MCP client now sees three distinct tools — code_reviewer, test_writer, quick_qa — each purpose-built.

Agent Factory

Don't want to write configs by hand? Add a factory instance:

{  "mcpServers": {    "agent-factory": {      "command": "npx",      "args": ["codex-octopus@latest"],      "env": {        "CODEX_FACTORY_ONLY": "true",        "CODEX_SERVER_NAME": "agent-factory"      }    }  }}

This exposes a single create_codex_mcp tool — an interactive wizard. Tell it what you want ("a strict code reviewer with read-only sandbox") and it generates the .mcp.json entry for you.

Tools

Each non-factory instance exposes:

Per-invocation parameters (override server defaults):

Configuration

All configuration is via environment variables in .mcp.json. Every env var is optional.

Identity

Agent

Instructions

Advanced

Authentication

Security

• Sandbox defaults to read-only — the agent can't write files unless you explicitly set workspace-write or danger-full-access.
• cwd overrides preserve agent knowledge — when the host overrides cwd, the agent's configured base directory is automatically added to additionalDirectories.
• Security overrides narrow, never widen — per-invocation sandboxMode and approvalPolicy can only tighten (e.g., workspace-write → read-only), never loosen.
• _reply tool respects persistence — not registered when CODEX_PERSIST_SESSION=false.
• API keys are redacted — the factory wizard never exposes CODEX_API_KEY in generated configs.

Architecture

┌─────────────────────────────────┐│  MCP Client                     ││  (Claude Desktop, Cursor, etc.) ││                                 ││  Sees: code_reviewer,           ││        test_writer, quick_qa    │└──────────┬──────────────────────┘           │ JSON-RPC / stdio┌──────────▼──────────────────────┐│  Codex Octopus (per instance)   ││                                 ││  Env: CODEX_MODEL=o3            ││       CODEX_SANDBOX_MODE=...    ││       CODEX_APPEND_INSTRUCTIONS ││                                 ││  Calls: Codex SDK thread.run()  │└──────────┬──────────────────────┘           │ in-process┌──────────▼──────────────────────┐│  Codex SDK → Codex CLI          ││  Runs autonomously: reads files,││  writes code, runs commands     ││  Returns result + thread_id     │└─────────────────────────────────┘

Known Limitations

• minimal effort + web_search: OpenAI does not allow web_search tools with minimal reasoning effort. Use low or higher if web search is needed.

Development

pnpm installpnpm build       # compile TypeScriptpnpm test        # run tests (vitest)pnpm test:coverage  # coverage report

License

ISC - Xiaolai Li