Debug

This skill is guidance, not a script. Make each investigation reduce uncertainty. A patch that changes the symptom without explaining it is not yet a diagnosis.

When not to use

• Designing the failure behavior itself, rather than explaining an observed wrong behavior. Use error-handling.
• A test that passes or fails inconsistently with no product symptom. Use test-reliability.
• A behavior that is merely undesired but correct. That is a change request, not a defect.

Inputs and authorization

• Required: the input, expected result, actual result, and the conditions that trigger the failure.
• Authorization: diagnosis-only work ends with findings. Apply a repair only when the task authorizes it, and renew alignment before changing agreed behavior or compatibility.

Method

Establish the input, expected, actual, and triggering conditions without removing the timing, scale, configuration, or environment that causes the failure. Prefer a fast, repeatable observation that catches the user's exact symptom. If reproduction is unavailable, inspect existing traces and successful versus failing paths, state the evidence limit, and identify the next discriminating observation.