Claude Codex Bridge

What umum-ai/claude-codex-bridge MCP server does

The umum-ai/claude-codex-bridge MCP server lets Claude Code delegate work to OpenAI Codex agents. A task runs in a selected absolute project directory and returns a session identifier promptly rather than making Claude wait for completion. Claude can then receive progress, questions, errors, and final results through Channels.

The bridge is intended for the 🤖 Coding Agents category. It supports workflows such as asking Codex to review code, steering an active task toward a different part of the implementation, interrupting a turn, and continuing a saved thread after Claude restarts.

How it works

Claude Code starts the bridge as an MCP server. The bridge launches a local codex app-server process and communicates with it over stdio. Control requests have a 30-second acknowledgement timeout, while the Codex task continues asynchronously inside the Codex process. This design does not depend on a long-running Claude Bash call or its command timeout.

Channel notifications carry Codex activity back to Claude. Notifications are batched approximately once per second, and Claude processes queued messages when it can take its next turn. The bridge keeps a limited event journal for the current process: up to 200 recent events and 64,000 characters of the latest answer. Event batches are capped at 8,000 characters, and truncation or an expired cursor is reported.

Codex uses its existing login state and configuration. The bridge does not add an API proxy, change model identity, intercept requests, or create a background daemon. Exiting Claude stops the bridge and its app-server process, although saved Codex threads can be reopened later.

Setup and configuration

Install Claude Code 2.1.261, Codex CLI 0.153.4, and Node.js 24.20.0 or newer. These are the tested versions; older versions are unsupported, and newer versions need verification. node, npx, and codex must be available on the PATH inherited by Claude Code. Claude and Codex must each be signed in, with Codex access to the model you intend to use.

Add the umum-ai/claude-codex-bridge marketplace to Claude, install the plugin for the user scope, and enable Channels with channelsEnabled: true in Claude settings. The plugin uses npx --yes to obtain its pinned npm package on first startup, so the initial launch needs npm registry access. Start Claude from the project directory and verify that a short test task produces incoming progress events. Channel activation can also depend on account or organization policy.

Tools and capabilities

The umum-ai/claude-codex-bridge MCP server provides these tools:

• codex_models lists models available to Codex.
• codex_start begins an independent task in an absolute project directory.
• codex_message sends an instruction during a turn or starts the next turn.
• codex_stop interrupts the current turn.
• codex_resume reopens a saved Codex thread.
• codex_answer responds to a structured question from Codex.
• codex_status reads status, pending questions, and the latest answer.
• codex_events reads recent events using a sequence cursor.

A selected model is requested without provider fallback. A service tier such as fast can override the configured Codex service tier for a thread. Retain the threadId when a session may need to continue after restarting Claude.

Limitations and notes

The bridge uses the experimental Codex app-server protocol and Claude Code Channels research preview. It is not a native Claude subagent, so its sessions do not appear in Claude's subagent panel. Live notifications may not arrive if Channels are unavailable or not enabled for the account or session.

Codex runs with danger-full-access and approvalPolicy: never. It can modify files and execute commands as the local user without requesting approval, and Claude's tool permissions do not sandbox it. Choose the project directory and delegated tasks with that execution mode in mind. Running work is lost when Claude exits; only saved threads can be resumed.