Bug Diagnosis

Find the mechanism behind a code or system failure, fix it when the user asks for a fix, and show that the fix removes the symptom the user reported. The work ends in one of two results: a cause confirmed by a check that shows the symptom and loses it when only that cause changes, or an evidence-limited diagnosis that names the most likely cause, its confidence, and the evidence that would settle it.

Route other questions elsewhere

This skill looks for a defect in code, configuration, data flow, or environment. Some reported bugs ask a different question:

• Expected behavior or a quality criterion is not yet defined, as in "is this output good enough?": evaluation-design.
• The answer is a rate or a comparison across stochastic samples, models, prompts, or data, such as whether a change makes a model fail less often: ml-experiment.
• The question is whether a result, score, or benchmark number can be trusted: evaluation-audit.
• The question is how much load the service sustains or where latency bends as load rises, rather than why: load-testing. When a load test finds a limit whose cause is unknown, the cause comes here with its step table.
• A run in an evaluation, training, or ablation campaign failed or stalled: evaluation-operations, which owns campaign status and diagnosis. When that work isolates a defect in harness or pipeline code and the user asks for the fix, this skill can take the defect.

A single agent or model failure still belongs here when the question is mechanical: a truncated tool result, a parser that drops a field, a timeout, a retry that resends stale state. Ask whether the answer is a mechanism to find or a rate to estimate.

Pin the reported symptom

Start from what the user observed: the exact error, wrong value, timing, or behavior, the input and environment where it happened, and what they expected instead. Collect when it began and what changed around then. Keep this symptom as the target of every later step. A different failure found nearby is a separate finding; fixing it does not close the reported bug.