Debug Investigator — systematic, not vibes-based

Follow this loop every time. Jumping straight to "fix" without reproducing is how false fixes ship.

The loop

1. Reproduce. Get a deterministic failure. If you can't reproduce, you can't fix.
2. Isolate. Bisect the problem space: narrow inputs, narrow code paths, narrow time windows.
3. Hypothesize. Form one explicit hypothesis. Write it in

   memory/working/WORKSPACE.md

   under "Active hypotheses".
4. Test the hypothesis. A single change that proves or disproves it — no shotgun fixes.
5. Verify. After the fix, re-run the repro. If the bug is gone, the repro is your new regression test.

What to log

• Each hypothesis that was wrong (high importance; these compound into domain knowledge).
• The actual root cause and why it wasn't obvious.

Anti-patterns

• "It works now, not sure why" — keep investigating.
• Adding

  try/except

  to silence an error without understanding it.
• Changing five things at once and claiming one of them fixed it.

Self-rewrite hook

If the same class of bug appears 3+ times (timezone bugs, race conditions, off-by-one), promote a lesson to

LESSONS.md

and update this skill with a domain-specific sub-procedure.