Bug investigation

Skill ldilov/harness-forge/skills/bug-investigation

AI coding agent runtime that makes LLMs understand your codebase with repository-aware context, memory, and continuous learning

Install

npx -y skills add ldilov/harness-forge --skill bug-investigation

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Use for defects, regressions, outages, flaky tests, and unexpected behavior. Guides the agent through triage, containment, reproduction, hypotheses, root-cause evidence, fix verification, and recurrence prevention. Do not use as the primary workflow for new features; use double-diamond-feature instead.

SKILL.md

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Bug Investigation

Trigger Signals

Use this skill when the user reports:

broken behavior
a regression
a failing or flaky test
production degradation
incorrect data/output
an incident-like symptom
a bug report with expected vs actual behavior

Do not use as the primary workflow for new features. Use double-diamond-feature instead.

Workflow

1. Triage

Classify:

severity: low, medium, high, incident
user/system impact
data risk
production risk
containment needed or not

If harm is ongoing, contain first and preserve evidence.

2. Problem Report

Capture:

expected behavior
actual behavior
reproduction steps or evidence gap
environment/version/time window
relevant logs/traces/screenshots if available

3. Evidence Inspection

Inspect relevant code, tests, recent changes, config, logs, and runtime artifacts. Reuse Harness Forge surfaces when present: .hforge/runtime/repo/repo-map.json, .hforge/runtime/findings/risk-signals.json. Label assumptions clearly.

4. Hypotheses

Create a ranked hypothesis table:

ID	Hypothesis	Likelihood	Evidence for	Evidence against	Test	Status

Prefer tests that rule out multiple causes. Record negative results.

5. Fix

Implement the smallest fix for the confirmed cause. Avoid broad refactors unless the cause requires them.

6. Verify

Verify using:

reproduction now passes
regression test added or updated
relevant existing tests
manual verification if automated tests are unavailable

7. Prevent Recurrence

Recommend one or more:

regression test
input validation
type/schema guard
monitor/alert
docs/playbook update
postmortem or A3/8D-lite for severe/recurrent issues

Output Before Fix

## Bug Investigation Frame

### Triage
- Severity:
- Impact:
- Data risk:
- Containment:

### Problem report
- Expected:
- Actual:
- Reproduction:
- Environment:

### Evidence
- User-provided:
- Repository/runtime:
- Assumptions:

### Hypotheses
| ID | Hypothesis | Likelihood | Evidence for | Evidence against | Test | Status |
|---|---|---|---|---|---|---|

### Fix plan
- Confirmed/likely cause:
- Proposed fix:
- Verification:
- Prevention:

Output After Fix

## Bug Fix Report
- Root cause evidence:
- Changes made:
- Verification:
- Regression coverage:
- Recurrence prevention:
- Follow-up/postmortem need:

Root-Cause Honesty

Do not claim a root cause unless it is supported by reproduction, logs, tests, code-path evidence, or clearly stated confidence.

Target Compatibility

This skill is plain-markdown and host-agnostic. Claude Code invokes it as /bug-investigation; Codex selects it via /skills or $bug-investigation. Do not rely on host-native hooks or interactive prompts.