Docs · Guide

mu on any model

mu (qybaihe/mu: npm's mu-agent, the mu command and the mu desktop app) is Pi with a judgment kernel added as an extension. It starts Pi, with Pi's settings.json and models.json in its own ~/.mu/agent folder, and the desktop app uses the same folder. So magpie sets mu up as it does Pi, and mu runs on any model in magpie: DeepSeek, GLM, Kimi, Qwen, Claude or a ChatGPT subscription.

Set up mu

1. Add a provider in magpieAdd an API key on the Providers page, or sign in to a subscription.
2. Pick a model for mu on the Agents pagePick one via magpie, and an effort if you want. The command and the desktop app both use it.
3. Start a new sessionNew mu sessions use the model.

magpie mu deepseek/deepseek-v4-pro

settings.json and models.json

magpie writes defaultProvider, defaultModel and defaultThinkingLevel in settings.json, and adds itself to models.json as the provider magpie, as it does for Pi.

// ~/.mu/agent/settings.json
{
  "defaultProvider": "magpie",
  "defaultModel": "deepseek/deepseek-v4-pro",
  "defaultThinkingLevel": "…"
}

// ~/.mu/agent/models.json
{
  "providers": {
    "magpie": { "apiKey": "", … }
  }
}

On its first run mu asks for mu setup only while models.json has no provider and settings.json no defaultProvider. Once magpie has written them, mu counts as set up and doesn't ask.

mu's own key

mu's requests say pi/ and a version, as Pi's do. So magpie gives mu a key of its own (magpie-mu), and the gateway counts its requests as mu's, not Pi's.

mu's folder

magpie finds mu's folder as mu does: the first of these variables that is set, with ~ in it standing for your home.

MU_AGENT_DIR
KYRN_AGENT_DIR
MU_CODING_AGENT_DIR
KYRN_CODING_AGENT_DIR

With none set it is ~/.mu/agent, or ~/.kyrn/agent when only ~/.kyrn, its old name, exists and ~/.mu doesn't. A mu in WSL is set up the same way, though magpie can't read the variables there.

mu is a common name: a mu on PATH that is maildir-utils' mu (djcb/mu) isn't taken for mu-agent. mu is also found by its alias mu-agent.

The judge

mu's judgment kernel has settings of its own (mu.json and MU_JUDGE). They are mu's, and magpie leaves them alone.

Switching back

Before its first write magpie saves settings.json and models.json as they were. Switching back puts them back byte for byte while they still say what magpie left.

magpie mu default

FAQ

Can mu run on DeepSeek, GLM or a ChatGPT subscription?

Yes. Pick a via-magpie model for mu on magpie's Agents page, and magpie writes settings.json and models.json in ~/.mu/agent.

Do I still run mu setup?

No. mu asks for it only while models.json has no provider and settings.json no defaultProvider, and magpie writes both.

Are mu's requests counted as Pi's?

No. Both say pi/ in their User-Agent, so magpie gives mu its own key (magpie-mu) and counts its requests as mu's.

Is mu's judge changed?

No. mu.json and MU_JUDGE are mu's own settings, and magpie leaves them alone.

More agents on the same models: Pi on any model, Mister Morph on any model, Grok App on any model and Claude Science on any model. Something fails? See Fixing common errors, or ask on Discord.