Install mumo in Codex.

Generate your API key

Sign in, create a mumo API key, and copy the value that starts with mmo_live_. Codex reads it from your shell environment, not from a config file — so it never lives in committed code.

Set MUMO_API_KEY for Codex

The plugin's .mcp.json declares bearer_token_env_var: MUMO_API_KEY, which tells Codex to read the token from your environment and send it as the Authorization header on every request to https://mumo.chat/api/mcp.

For Codex in the terminal, add export MUMO_API_KEY=mmo_live_YOUR_KEY_HEREto your shell's startup file — ~/.zshrcfor zsh, macOS's default; for Bash, the file your terminal actually sources (~/.bash_profile for macOS login shells, ~/.bashrc on most Linux terminals) — and open a new terminal window. Confirm the key is there before going further:

echo "$MUMO_API_KEY"

If that prints nothing, your shell sourced a different file — fix that first, because the next command publishes whatever the variable holds, empty included. On macOS, the Codex app and IDE extension launched from Finder or the Dock don't read your shell profile, so from that same window also set it for GUI apps — passing the variable rather than the literal key, so the key never lands in your shell history:

launchctl setenv MUMO_API_KEY "$MUMO_API_KEY"

One caveat: whether launchctl setenvsurvives a reboot is undocumented (Apple's man page says nothing either way); if mumo stops authenticating after a restart, re-run it. Both file-based options described here — your shell's startup file and a LaunchAgent plist that runs the same command at login — store the key in plaintext. Apply chmod 600 to whichever file you use and never commit it.

Add the mumo marketplace

If you don't have the Codex CLI yet, install it from npm — then register the mumo marketplace:

npm i -g @openai/codex
codex plugin marketplace add mumo-chat/mumo-codex

This adds an entry to ~/.codex/config.toml under [marketplaces.mumo]. Adding the marketplace does not auto-enable the plugin — that's the next step.

Install the mumo plugin

Recommended: install from the Codex app. Most users live in the GUI, and the install card is cleaner there.

1. Open the Codex desktop app.
2. In the side nav, click Plugins.
3. Click the publisher dropdown (defaults to Built by OpenAI) and select mumo.
4. On the mumo plugin card under Productivity, click the + button.
5. In the install dialog, click Install mumo.

When the install completes, ~/.codex/config.toml ends up with [plugins."mumo@mumo"] + enabled = true, and the plugin's skill + MCP server are registered. Start a new thread (or restart Codex) so the freshly-installed MCP server attaches.

CLI alternative. If you're working headless or prefer the terminal, the plugin browser is also available inside any Codex CLI session. Start a session with codex, then run /plugins, switch to the mumo marketplace tab, select mumo, press Enter, and choose Install plugin.

Fallback if neither the app nor the CLI plugin browser is enabling mumo on your Codex build: register the MCP server directly. This gives you the mumo tools but skips the skill (so the agent loses the deliberation-loop instructions and has to discover the tools on its own):

codex mcp add mumo \
  --url https://mumo.chat/api/mcp \
  --bearer-token-env-var MUMO_API_KEY

Verify with a low-cost call

Before running a real deliberation, smoke-test auth and tool routing. Ask Codex in a thread:

Ask mumo to list available models.

That hits list_models (read-only, no credit consumed) over a live connection — a model list back means the key resolved and the server accepted it. An auth error means MUMO_API_KEYisn't visible to the Codex you launched.

codex mcp list

…only confirms mumo is registered. It does not complete an MCP handshake, so a server with a missing key still shows up there.

Run your first deliberation

Name mumo explicitly the first time so Codex routes through the panel. The skill will guide the agent through the create→wait→read→snippet loop and teach it to verify the session actually fired.

Ask mumo to compare Postgres and MongoDB for our event store.
Include the constraints from this repo and tell me where the models disagree.

If the agent claims a deliberation succeeded but doesn't produce a UUID-format session ID, the call didn't fire — confirm with list_sessions or check mumo.chat. The skill teaches this discipline; this is the user-facing reminder.