# Investigate First

> Diagnose ambiguous failures before editing. Use for unknown causes, intermittent behavior, performance regressions, or investigations needing evidence-ranked hypotheses.

- Skill: `juliusbrussee/investigate-first` (Agent Skill, multi-file: 2 files)
- Install (CLI): `npx skillmds@latest add juliusbrussee/investigate-first`
- Raw SKILL.md: https://api.skillmd.com/api/skills/juliusbrussee/investigate-first/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: Julius Brussee (https://skillmd.com/u/juliusbrussee)
- Updated: 2026-09-09
- Page: https://skillmd.com/skills/juliusbrussee/investigate-first

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# Investigate first

Gather evidence before changing product code.

- Separate observed symptom from inferred cause.
- Trace inputs, state transitions, ownership boundaries, and failure output.
- Rank hypotheses by evidence and cheap falsification value.
- Do not edit until one credible mechanism explains evidence.
- Stop exploration when evidence is sufficient to name cause or exact blocker.

Report cause and proof. Make no fix unless task authorizes implementation.