Appmost

Build native apps
with OpenAI Codex.

Connect Codex to Appmost’s local MCP tools. Let your agent inspect the project, refine your screens, and show you the result in the native preview.

For local Codex sessions on Mac · Updated

Connect in five steps.

  1. Open your project in Appmost.

    Sign in to Appmost on your Mac, then open an existing project or start a new one. Keep the app open during the Codex session.

  2. Allow external agents.

    In Appmost, open Settings → External Agents and enable Allow external agents to use Appmost tools. In older builds, look for Local Agent.

  3. Choose Codex and copy the command.

    Select Codex under Configure. Copy the setup command shown by Appmost. It registers the appmost MCP server using the bridge installed on your Mac.

  4. Run it in Terminal.

    Paste and run the copied command on the same Mac. You need the Codex CLI installed and signed in. Use the complete command from Appmost, including its quoted bridge path and address.

  5. Restart Codex and start a new chat.

    Use a local Codex session on the same Mac. Check that Appmost is listed by running the read-only command below in Terminal, or use /mcp in the Codex CLI to inspect active servers.

    codex mcp list

    A saved entry confirms registration. The first tool request below checks that the agent can actually reach Appmost.

Check the connection first.

Begin with a read-only request so you can confirm Codex sees the project you intended.

Use the Appmost MCP tools to inspect the currently open project. Tell me the project name and list its pages. Do not change any files or settings.

Once that works, describe one screen change. Review it in Appmost before moving on.

Use the Appmost MCP tools to review the home screen in the open project. Suggest one improvement to the hierarchy and explain your proposal before making changes. After I approve, apply it and render the updated screen for review.

If the tools do not appear.

Terminal says “codex: command not found”.

Install or update the Codex CLI using OpenAI’s installation instructions. Open a fresh Terminal window and run the setup command copied from Appmost again.

Appmost is registered, but the connection fails.

Keep Appmost running, check External Agents is enabled, and expand MCP connection details to verify the status is Running. Copy a fresh setup command if the server address has changed, then restart Codex and start a new chat. Preserve the error shown by the agent if you need support.

Codex is working in a cloud environment or on another Mac.

The local bridge must run on the Mac where Appmost is open. Choose a local session on that Mac for this setup. A loopback address does not connect a cloud environment to your computer.

I want to use ChatGPT on the web.

This guide configures local Codex, rather than a ChatGPT web connection. ChatGPT’s remote MCP setup requires a reachable server and its own authentication. Follow OpenAI’s remote connection guide for that separate workflow; Appmost’s local bridge address cannot be pasted into it as a public endpoint.

Do I need an OpenAI API key in Appmost?

This MCP setup does not require one. Keep your normal Codex sign-in. The connection registers tools with Codex; it does not set up a separate direct OpenAI API integration in Appmost.

Continue from here.

Keep the design and the project together as you refine native screens or explore the iPhone Duo preview.

Official OpenAI MCP documentationSet up Claude Code instead