loom-debugging

# Debugging ## Overview Find the true cause of a defect and prevent its recurrence — across app code, tests, data pipelines, ML, and infra. The failure mode to avoid is *symptom-patching*: changing code until the symptom disappears without understanding why, which moves the bug rather than fixing it. ## The Root-Cause Loop Run this loop; don't skip steps. Most wasted time comes from hypothesizing before reproducing, or fixing before localizing. 1. **Reproduce** — deterministically. If you can't reproduce it, you can't verify a fix. Capture exact inputs, env, versions, and the full error/stack. For intermittent bugs, first make it *more* frequent (loop it, add load, shrink timeouts) before anything else. 2. **Minimize** — shrink to the smallest input/code that still fails. Delete half, re-run, repeat (delta-debugging). A 5-line repro localizes faster than a 5000-line one and often reveals the cause outright. 3. **Localize** — bound *where* it happens before asking *why*. Bisect in space (comment out / binary-search modules) and in time (`git bisect`). Read the stack trace top frame first, then the first frame in *your* code. 4. **Hypothesize** — state a specific, falsifiable cause ("X is null because Y returns None when Z"). Vague hypotheses ("something with async") aren't testable. 5. **Test the hypothesis** — one variable at a time; change something that should confirm/refute it. If the experiment can't distinguish two causes, design a better one. 6. **Fix** — the root ...