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Diagnose and fix bugs with root-cause analysis and verification. Use when you have a concrete issue report, failing behavior, runtime error, or test regression that should be resolved safely. Stop and escalate to brainstorm when scope or risk grows.

Code Review

What this skill does


# Fix

## Scope Gate (Required Before Starting)

Use this skill only when all conditions below are true:

1. **Concrete issue signal exists**
   - Clear failing behavior, error, or regression is identified
   - Enough evidence exists to begin diagnosis (logs, stack trace, failing test, or reproducible steps)

2. **Likely localized fix path**
   - Issue appears constrained to a small area
   - No expected cross-system redesign or migration

3. **Low-to-moderate architectural risk**
   - Fix can be made without foundational changes
   - No phased rollout/feature-flag strategy is expected

4. **Straightforward verification path**
   - Reproduction and post-fix checks can be run in practical scope
   - Success criteria can be validated directly

If any condition fails, escalate to `brainstorm` or `write-plan`.

## Hard Stop Escalation Criteria

Immediately stop and switch to planning if any of these occur:

- Root cause remains unclear after focused investigation
- Fix requires cross-cutting architectural or data-model changes
- Scope expands into large refactor or multi-module migration
- Security/compliance-sensitive behavior is involved
- Verification reveals broad regressions requiring phased mitigation
- Multiple fix attempts fail without converging on a root cause

Escalation action:

1. Stop all implementation activities.
2. Output the exact message: "This fix exceeds safe single-pass debugging limits. Ask, Recommend `brainstorm` or `write-plan` first to define phased diagnosis, implementation, and risk controls."

## Workflow

### Step 1: Intake and Contextualize

1. Understand the reported bug and define explicit expected behavior.
2. Collect/confirm minimum bug report fields:
   - Title
   - Expected behavior
   - Actual behavior
   - Reproduction steps
   - Evidence (logs, trace, screenshot, failing test output)
   - Environment (branch/OS/runtime/version if relevant)
   - Impact/severity
3. Load only the project context relevant to the bug:
   - If `docs/SUMMARY.md` exists, read it first.
   - Load only task-relevant detail docs.
   - Prioritize `Code Standard` docs for implementation conventions.
   - If docs conflict with code or user intent, use the available input/question tool before broad changes.

### Step 2: Reproduce and Diagnose

1. Reproduce the issue consistently.
2. Locate the failure point (file/function/line range/subsystem).
3. Trace control/data flow to identify the **root cause**.
4. Form a fix hypothesis and confirm it explains observed behavior.

Guidelines:

- Read surrounding code, not only the failing line.
- Prefer root-cause correction over symptom patching.
- Add temporary diagnostics only when needed; remove them after use.

### Step 3: Decide Small vs Bigger Fix

Classify the work before coding:

#### Small fix (continue in this skill)

Most are true:

- Root cause is clear and validated
- Change surface is narrow (typically a few files)
- Regression risk is limited and testable quickly

#### Bigger/risky fix (escalate to `brainstorm` or `write-plan`)

Any are true:

- Root cause is uncertain
- Multiple subsystems must change together
- Requires migration, rollout sequencing, or broad refactor
- Risk cannot be reasonably controlled in a single pass

If it is a bigger fix, follow **Hard Stop Escalation Criteria**.

### Step 4: Implement (Small Fix Path)

1. State a brief 1-3 bullet implementation plan.
2. Apply the smallest targeted change that resolves the root cause.
3. Keep scope strict; avoid unrelated refactors.
4. Add/update regression tests when applicable.

### Step 5: Verify

Run validation in increasing scope:

1. Focused checks for the changed behavior/module
2. Nearby regression checks
3. Relevant project checks (lint/typecheck/tests/build) as needed

Fix is complete only when:

- Reproduction no longer fails
- Expected behavior is confirmed
- No critical regressions are introduced

If verification indicates broader impact, escalate to `brainstorm` or `write-plan`.

### Step 6: Complete and Report

Provide a concise completion report with:

- **Root cause**
- **What changed**
- **Why this fix works**
- **Verification performed and results**
- **Residual risks / follow-ups**

If behavior or documentation-relevant rules changed, update the minimal relevant docs. If architecture changed, this should have been escalated.

## Rules

- Do not guess when key context is missing.
- Always prioritize root-cause fixes.
- Keep blast radius minimal.
- Do not mark done without verification.
- Escalate early when scope/risk exceeds this skill.

## Optional Bug Report Template

Use when the report is incomplete:

- Title:
- Expected behavior:
- Actual behavior:
- Reproduction steps:
- Error logs/stack trace:
- Environment:
- Impact/severity:
- Additional context:

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