investigatelisted

# Investigate A bug report names a symptom. Find the cause and fix it where all callers route through, so no sibling path stays broken. ## Steps (paste as todos) 1. **Reproduce first.** Get a deterministic repro before theorizing. Can't reproduce → gather evidence (logs, trace, inputs) until you can. No repro, no fix. 2. **Capture the evidence.** Exact error, stack, inputs, the failing values. Write down what you observe vs what you expected. 3. **Locate the shared point.** Find the function that misbehaves, then `grep` every caller. The cause usually lives where they converge, not in the one path the report named. 4. **Form one hypothesis and test it.** Change nothing else. Confirm the hypothesis explains the observed evidence before fixing. 5. **Fix at the source.** One guard/fix in the shared function beats a patch in every caller — smaller diff, and it fixes the siblings too. 6. **Prove it.** Re-run the repro → gone. Add or adjust a test that fails without the fix, so it can't regress. ## Guardrails - Don't patch the symptom on the named path and stop — the other callers are still broken. - A "this is fine / expected" conclusion is valid only if the same observable can't also be the failure. If a genuinely broken state looks identical, keep digging. - Don't stack speculative fixes; one variable at a time (see `hillclimb`).