Diagnose and Fix Tracked Errors

Goal

Turn an error that surfaced through an error-tracking or observability tool — or a stack trace or log someone pasted — into an evidence-backed root cause, and land the fix at the point the project's design says owns the violated rule, which is frequently not where the error was observed.

This is a method, not a tool. It rests on four commitments:

• Reproduce before theorizing. Build a deterministic way to trigger the exact symptom before reading code to form theories.
• Isolate the origin. Strip non-load-bearing layers until the origin is separated from the site where the failure became visible.
• Drive root cause with falsifiable hypotheses. Enumerate candidate causes, then disprove them one variable at a time.
• Fix at the design-correct location. The place that crashes is rarely the place that owns the invariant. Decide the owner by design before writing any fix, and place the fix — and its regression test — there.

The symptom's location and the cause's location are different questions. Answer both, in that order, and never let the first stand in for the second.

What Counts as In Scope

Apply this skill when the task does one or more of these things: