AIO Compound

Retain knowledge that prevents recurrence or substantial rediscovery. Completion, effort and a large diff are not reasons to add documentation. Read lesson procedure and use lesson only when the lesson earns a durable record.

1. Confirm the problem is solved and the causal claim verified against the current tree and observed evidence. Unconfirmed hypotheses stay in the diagnostic log, not the knowledge base.
2. Search existing project lessons and relevant backend knowledge. Decide whether the reasoning would be lost without a lesson. Code/tests that already explain it usually need no duplicate document.
3. Update the matching lesson when it is stale or incomplete. Otherwise write one focused original lesson with context, trigger, invariant, root cause, failed hypotheses, evidence, verified remedy, limits, retrieval terms and refresh conditions.
4. Validate cited artifacts, path containment and claims; check search terms retrieve the lesson and distinguish it from similar problems. Update the project's existing index or a contained lesson index for new durable records.
5. Return the lesson path, what is now retrievable and any remaining limits, or report that no qualifying lesson was written. Do not change instruction files or publish knowledge externally merely to make it discoverable.

This skill captures actual learning and returns to its caller. It does not start a new build, duplicate upstream manuals or add speculative global rules to every future task.