Install Deus Witness in Codex

What you need first

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

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 witness --env DEUS_WITNESS_KEY=YOUR_DEUS_WITNESS_KEY -- uvx deus-witness==0.2.56 -- YOUR_UPSTREAM_COMMAND

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

Check it worked

Ask Codex: List the tools of witness.

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.