A three-stage debugging chain instead of one giant prompt

For a complex bug, this three-stage chain is more reliable:

1. Diagnose: provide logs, expected behavior, and the smallest reproduction; ask only for ranked hypotheses with evidence.
2. Test: request a low-risk verification command or test for each hypothesis. Do not change code yet.
3. Fix: once the cause is confirmed, request the smallest patch, a regression test, and a rollback path.

Review each stage and carry only verified information forward. This prevents the model from overcommitting to its first guess.