dhpk-root-cause-investigationlisted

# Bug Investigation Skill ## Overview Use a five-phase evidence loop to move from symptom to root cause, then to a bounded repair handoff: `Clarify → Gather evidence → Trace and confirm → Design the fix → Preserve knowledge` Keep the investigation record current. Every conclusion must point to evidence; every unresolved claim must be labelled as a hypothesis or blocker. ## Symptom-specific red loop Before broad theorizing, turn the reported symptom into a **symptom-specific** reproduction: a minimal input, expected/actual output, and a **red-capable** assertion or probe that fails for the same reason. Minimize the case until one boundary or transition can be observed. If the failure cannot be reproduced, record that as inconclusive evidence instead of weakening the assertion. Maintain a **ranked** list of **falsifiable** hypotheses. For each hypothesis, name the prediction, the smallest discriminating check, and the evidence that would reject it. Do not promote a hypothesis because it is plausible or because it matches a familiar bug pattern. Instrumentation is temporary and tagged with its purpose, owner, and cleanup condition. Remove or quarantine debug probes after confirmation, retain only the evidence needed for a regression test, and record whether a **postmortem** or follow-up is needed for monitoring, data repair, or process change. ## Redact before sharing evidence Redact secrets from every command, output, log excerpt, trace, and captured artifact before p