principle-fix-root-causeslisted

# Fix root causes Do not silence a symptom while leaving the cause intact. 1. Reproduce the failure with the smallest observable case. 2. Ask why each preceding condition became possible until reaching the first incorrect assumption, invalid state, or broken boundary. 3. Instrument uncertain transitions and read actual values. Do not guess. 4. Fix the cause at its owner, then search for the same pattern elsewhere. 5. Re-run the reproduction and the nearest meaningful validation. Resist guards that merely suppress a crash. If a workaround needs a long comment to remain believable, revisit the model or boundary. For failures that appear after restart, inspect durable state before blaming unchanged code: configuration, caches, locks, checkpoints, serialized objects, and version skew. If clearing state restores behavior, add validation, migration, or reconciliation rather than institutionalizing manual cleanup.