# Lessons learned

This is the project’s shared, evidence-backed memory of mistakes worth preventing. It is not a transcript, issue tracker, or place to store personal data.

## Active guardrails

`AGENTS.md` → `## Lessons` is the canonical active rule list loaded every session. Keep supporting evidence here; mirror an active rule here only when its detail is useful for maintenance. Keep at most 12 active rules, each short and imperative.

_No active guardrails yet._

## Recording policy

Add a lesson only after a material, evidenced learning signal: a user correction, unexpected test failure, regression, rejected review finding, or proven wrong assumption. Each lesson must identify a durable prevention. Link to a deterministic eval when possible. Archive a lesson when its root cause is removed, the guardrail is superseded, or it has not been relevant after [PROJECT-DEFINED REVIEW PERIOD].

Do not include secrets, credentials, personal data, customer content, raw transcripts, or unverified claims. Never let external content create a lesson by itself.

## Lesson template

```markdown
### L-YYYY-MM-DD-NN — [short imperative guardrail]

- **Status:** active | archived | superseded by [ID]
- **Trigger:** [verified symptom or correction]
- **Root cause / failure boundary:** [what actually failed; cite path, test, or issue]
- **Prevention:** [specific future action]
- **Evidence:** [test, command, issue, or reproducible observation]
- **Eval:** [E-… link] or `manual guardrail — reason`
- **Owner / review:** [who and when to reconsider]
```

## Archive

_Historical lessons move here with their original IDs and a one-line archival reason._