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Wraps the OpenAI Codex SDK to provide specialized AI agents for coding tasks, allowing for the configuration of specific models, sandbox environments, and reasoning effort levels for use cases like code review and test generation.

How do I use Codex Octopus?

1. Click on "Install Server". 2. Wait a few minutes for the server to deploy. Once ready, it will show a "Started" state. 3. In the chat, type @ followed by the MCP server name and your instructions, e.g., "@Codex Octopus write thorough unit tests for the user authentication logic in auth.js" That's it! The server will respond to your query, and you can continue using it as needed. Here is a step-by-step guide with screenshots.

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:

Tool	Purpose
`<name>`	Send a task to the agent, get a response + `thread_id`
`<name>_reply`	Continue a previous conversation by `thread_id`

Per-invocation parameters (override server defaults):

Parameter	Description
`prompt`	The task or question (required)
`cwd`	Working directory override
`model`	Model override
`additionalDirs`	Extra directories the agent can access
`effort`	Reasoning effort (`minimal` to `xhigh`)
`sandboxMode`	Sandbox override (can only tighten, never loosen)
`approvalPolicy`	Approval override (can only tighten, never loosen)
`networkAccess`	Enable network access from sandbox
`webSearchMode`	Web search: `disabled`, `cached`, `live`
`instructions`	Additional instructions (prepended to prompt)

Configuration

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

Identity

Env Var	Description	Default
`CODEX_TOOL_NAME`	Tool name prefix (`<name>` and `<name>_reply`)	`codex`
`CODEX_DESCRIPTION`	Tool description shown to the host AI	generic
`CODEX_SERVER_NAME`	MCP server name in protocol handshake	`codex-octopus`
`CODEX_FACTORY_ONLY`	Only expose the factory wizard tool	`false`

Agent

Env Var	Description	Default
`CODEX_MODEL`	Model (`gpt-5-codex`, `o3`, `codex-1`, etc.)	SDK default
`CODEX_CWD`	Working directory	`process.cwd()`
`CODEX_SANDBOX_MODE`	`read-only`, `workspace-write`, `danger-full-access`	`read-only`
`CODEX_APPROVAL_POLICY`	`never`, `on-failure`, `on-request`, `untrusted`	`on-failure`
`CODEX_EFFORT`	`minimal`, `low`, `medium`, `high`, `xhigh`	SDK default
`CODEX_ADDITIONAL_DIRS`	Extra directories (comma-separated)	none
`CODEX_NETWORK_ACCESS`	Allow network from sandbox	`false`
`CODEX_WEB_SEARCH`	`disabled`, `cached`, `live`	`disabled`

Instructions

Env Var	Description
`CODEX_INSTRUCTIONS`	Replaces the default instructions
`CODEX_APPEND_INSTRUCTIONS`	Appended to the default (usually what you want)

Advanced

Env Var	Description
`CODEX_PERSIST_SESSION`	`true`/`false` — enable session resume (default: `true`)

Authentication

Env Var	Description	Default
`CODEX_API_KEY`	OpenAI API key for this agent	inherited from parent

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 install
pnpm build       # compile TypeScript
pnpm test        # run tests (vitest)
pnpm test:coverage  # coverage report

License

ISC - Xiaolai Li

Codex Octopus

Codex Octopus

Why

Prerequisites

Install

Quick Start

Multiple Agents

Agent Factory

Tools

Configuration

Identity

Agent

Instructions

Advanced

Authentication

Security

Architecture

Known Limitations

Development

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