Install Langfuse MCP in Codex

What you need first

• Codex, installed.
• uv, which gives the uvx command the server starts with.
• Your own values for YOUR_LANGFUSE_PUBLIC_KEY,YOUR_LANGFUSE_SECRET_KEY.

Steps

1. Run this in a terminal. It writes the server into ~/.codex/config.toml, which the Codex CLI, its IDE extension and the ChatGPT desktop app share.

codex mcp add langfuse-mcp --env LANGFUSE_PUBLIC_KEY=YOUR_LANGFUSE_PUBLIC_KEY --env LANGFUSE_SECRET_KEY=YOUR_LANGFUSE_SECRET_KEY -- uvx langfuse-mcp==0.13.0

2. Replace YOUR_LANGFUSE_PUBLIC_KEY,YOUR_LANGFUSE_SECRET_KEY with your own values.
3. Start Codex again and type /mcp: the server is listed.

Check it worked

Ask Codex: List the tools of langfuse-mcp.

If it does not start

spawn uvx ENOENT

uv is not on the PATH that Codex sees. Install it, or write the full path of uvx in the config.

The server starts, but its tools fail

A YOUR_… placeholder is still in the config, or its value is wrong.