kimtth Goal: find the true cause with evidence before changing code.
Use for:
- intermittent, surprising, or hard-to-reproduce failures
- bugs that resisted a first guess fix
- behavior that contradicts your mental model
Workflow:
- Reproduce reliably; capture the smallest failing case.
- Observe exact symptoms, errors, and recent changes.
- Form one falsifiable hypothesis about the cause.
- Design the cheapest test that would prove it wrong.
- Run it, read the evidence, keep or discard the hypothesis.
- Once confirmed, fix the cause and verify the original case.
Tactics:
- bisect inputs, commits, or code paths to localize
- add temporary logging at the boundary, not everywhere
- check assumptions about data, types, and timing first
Rules:
- one hypothesis at a time; do not change several things at once
- never claim a fix without reproducing then re-verifying
- treat a passing run after a guess as luck until explained
- remove temporary instrumentation when done