root-cause-investigation

name	root-cause-investigation
description	Diagnose a bug, failing test, error, regression, or incorrect runtime behavior by reproducing it and tracing the first causal divergence. Use when the true source is unknown; do not use for speculative cleanup or when a proven fix is already specified.

Root-Cause Investigation

This skill supplies a read-only diagnostic method. It never authorizes edits, commits, pushes, remote updates, issue comments, or delegation; the caller owns those permissions and budgets.

Follow the investigation method. Maintain one hypothesis ledger and choose experiments by information gain. Stop only with ROOT CAUSE PROVEN, ROOT CAUSE NOT PROVEN plus exact missing evidence, or CANNOT REPRODUCE plus the required environment/input/state. Use the diagnosis template or the caller's stricter format.

Apply a caller-authorized fix only when the proven source change is small, unambiguous, and contains no material product/architecture choice. Require the original repro and appropriate behavioral regression coverage. Otherwise hand off the diagnosis and fix direction. Never suppress the symptom, weaken a test, catch-and-ignore the error, or add a fallback that preserves the cause.