copilot-setting: Skill for Claude Code

Debug — Workflow

Systematic isolation and minimal fix.

Phase 0 — Load canonical rules

MANDATORY pre-load gate — do NOT propose a fix (Phase 6) until you have opened the instruction files for the layers you touch. Your training data defaults to modern Java/Spring; these files are the version lock for Java 8 / Spring 3.2 / Hibernate 4.2. Open them first, every time — the negative lists in the agent body are a floor, not the full rules. Read-back receipt: NAME each file you opened and QUOTE its single most load-bearing rule for this change — a generic restatement you could have written from memory means you skipped the file.

Layers you touch — open each one: instructions/java.instructions.md, instructions/spring-hibernate.instructions.md, instructions/sql.instructions.md, instructions/sql-ddl.instructions.md, instructions/security.instructions.md (a bug fix can regress a security control — XSS, IDOR, injection).

Phase 1 — Define the Problem

Expected:      <what should happen>
Actual:        <what actually happens>
Error/Trace:   <exact message, not paraphrased>
Reproducible:  always / sometimes / once
Since when:    recent change / always / unknown

Phase 2 — Gather Evidence

Read stack trace bottom-up — first line in YOUR code is the entry point. Check recent git changes in the affected area.

Phase 3 — Form Hypotheses

List ≥ 3 candidate causes before ranking — never investigate the first hypothesis without listing alternatives. For each: what confirms it, what refutes it, effort to verify. Verify lowest-effort hypothesis first.

Phase 4 — Isolate

Binary search on execution path: entry → failure point → check midpoint → narrow until divergence is one line.

Phase 5 — Verify Root Cause

Verification gate (MUST answer before Phase 6):

1. Does this cause explain ALL reported symptoms? List each symptom + how this cause produces it.
2. Remove this cause hypothetically — would the bug disappear? If unsure, you haven't found root cause.
3. Is this the deepest cause, or a symptom of something upstream?