Logic-Lens — Fault Locate

When to Use

Use this skill when you need locate the root cause of a CONFIRMED failure via backward-then-forward semi-formal tracing. Trigger when the user provides a stack trace, failing assertion, error message, or specific wrong-value observation — "find the bug", "this test is failing", "track down this crash", "why is...

Setup

Use lazy loading per ../_shared/common.md §13:

1. Read ../_shared/common.md only for language, Iron Law, Fault Confidence, scope routing, Remedy discipline, config fields, and loading budget.
2. Read only the relevant step in logic-locate-guide.md as you reach it.
3. Load ../_shared/logic-risks.md, ../_shared/semiformal-guide.md, ../_shared/semiformal-checklist.md, and ../_shared/report-template.md on demand when the current step needs them.

Process

Step 0. Language + scope routing. Detect language per common.md §1. Confirm a concrete failure exists (stack trace, failing assertion, specific wrong value). If only a suspicion, switch to logic-review.

Step 1. Understand the failure (guide Step 1) — observed behavior, expected behavior, reproduction path.