muUsing mu
Lessons
What mu learns from your corrections and from getting itself unstuck, how lessons are merged and recalled, and how unused ones retire.
The lessons library is what mu remembers between sessions: your corrections, the rules you set, and the traps the agent fell into and how it got out. The command line and the desktop app share it. The judge decides what is worth keeping, whether it is new, when it applies and whether it was followed; a small writing model puts it into words.
Where lessons come from
| Source | When | What the judge decides |
|---|---|---|
| Your corrections and rules | You say no, use pnpm or never commit to main | Is this a correction, or a rule for later? (memory.capture) |
| The agent getting unstuck | It went in circles or hit a dead end, and the turn still ended with a passing check or the goal met | Was what finally worked a different approach? If so, keep the trap and the way round. (memory.outcome, at most once a turn, only after real trouble) |
| The model | It keeps something with the remember tool |
Useful again later, a one-off, or known already from the prompt or the project files? Only the first is kept. (memory.worth) |
| Sub-agents | A line starting with Lesson: in a sub-agent's report |
The same question (memory.worth) |
| You, directly | /remember <text> |
Nothing: kept as written |
Merging
Before a new lesson is stored, the six most similar kept lessons are compared with it in one request (memory.merge): the same lesson is not stored twice; a more precise one replaces the old; on a contradiction, the old one is retired, because your latest word wins. Only something you said can retire a lesson you taught; the model cannot overrule you.
Recall
When a message arrives, at the same time as the preflight, the judge is asked of each candidate lesson whether it applies (memory.recall). Up to 24 candidates are judged, the most often followed first; at most five come into the turn, one line each. Sub-agents get the lessons that apply to their task in their brief.
Followed or not
At the end of a turn, the judge reads what happened and asks of each recalled lesson whether it was followed (memory.applied). A lesson recalled eight times and never followed retires itself, and mu says so.
Commands
| Command | What it does |
|---|---|
/remember <text> |
Keep a lesson as written |
/lessons |
The lessons for this project: id, kind, how often recalled and followed, the lesson |
/lessons all |
Including those that apply everywhere and the retired ones |
/forget <id> |
Retire one |
In the desktop app, the Lessons tab shows the same list; you can edit a lesson or retire it there.
The library is one file, ~/.mu/agent/mu/lessons.jsonl. Each lesson has a kind (correction, preference, pitfall, workaround or fact), when it applies, what to do, and whether it holds for this project only or everywhere.