diagnoselisted

Active bug investigation discipline — 6-phase methodology covering feedback-loop, reproduce, hypothesise, instrument, fix-with-regression-test, and cleanup-with-post-mortem. Use when investigating a hard bug or performance regression that doesn't have an obvious root cause. Triggers: "diagnose", "debug this", "investigate this bug", "reproduce the failure", "why is X failing". Read-only guidance — guides the human through systematic investigation rather than auto-fixing. Refuses to skip Phase 1 (feedback loop) even under pressure, because guessing-before-loop is the documented anti-pattern this skill prevents. Maps to H1 (Be Proactive — trace all callers) + H5 (Seek First to Understand — reproduce before fixing). Hands off to /post-mortem once the fix lands and the feedback loop passes.
pitimon/8-habit-ai-dev · ★ 3 · Code & Development · score 77

Install: claude install-skill pitimon/8-habit-ai-dev

# `/diagnose` — Active Bug Investigation (6 Phases) **Habits**: H1 (Be Proactive — prevent recurrence, not just patch the symptom) + H5 (Seek First to Understand — reproduce before fix) ## When to Use - A bug is reported and the root cause is **not** obvious - A performance regression appeared; you need to localize what changed - Tests passed locally but failed in CI, or vice versa - A feature works for some inputs and fails for others — you need to find the boundary - A previous fix didn't hold; the bug returned in a different form This skill enforces the discipline **build a fast feedback loop before you guess**. Documented friction: a lesson in `~/.claude/lessons/2026-04-12-compression-worker-420-investigation.md` notes that a 30-minute log-analysis session could have been a 5-minute SQL-comparison session if Phase 1 had been done first. ## When to Skip - Single-line bug with obvious root cause (typo, wrong constant, off-by-one in plain sight) - Lint/format errors with a clear fix - Rename refactors and dependency bumps with passing CI - Stack trace points to a single line that you can read and immediately understand For these, fix directly and run tests. Save the 6 phases for hard bugs. ## Predecessor `/research` Brief (Optional Input) If you ran `/research` before this — or have a saved brief from a prior session — paste its path now. Standard locations: - `~/.claude/plans/*.md` (Deep-mode briefs) - `docs/specs/<slug>/research.md` (persisted briefs) If no prio