Debug Deep

The full investigation workflow. Replaces "OK try X, now try Y, hmm let me check Sentry" with one chained skill that gathers evidence systematically.

Auto-invocation triggers

• User reports a bug they've already tried to fix once
• Bug report mentions "intermittent", "sometimes", "in production but not local"
• Sentry / error monitoring shows the same issue 3+ times
• CI failure pattern matches a recurring class
• User says "this is broken, find why"

Workflow

Phase 1 — Hypothesis tree (always)

Invoke systematic-debugging to build a hypothesis tree with evidence-for/against columns. No fixes yet — just structured root-cause analysis.

Phase 2 — Evidence walk (always)

Invoke tracer agent (via Agent tool, subagent_type=tracer) to walk the call paths and collect concrete evidence per hypothesis. Tracer ranks hypotheses by evidence weight and recommends next probes.

Phase 3 — Production correlation (if production-impacting)

Invoke sentry to query for matching error signatures in the last 30 days. Look for:

• Frequency trend (rising / steady / one-off)
• Affected users / orgs / environments
• Stack trace overlap with the local repro

If production data contradicts the hypothesis tree → loop back to Phase 1 with the new evidence.

Phase 4 — Regression check (always)

Invoke ci-watch to find when the failure first appeared in CI history. Bisect to the introducing commit if linear history allows. Cross-reference with the hypothesis tree's "introduced when" entries.

Phase 5 — Fix (autonomous if hypothesis is high-confidence)

Once the tree converges on one hypothesis with strong evidence:

• For local-scope fixes: implement directly via Edit
• For cross-module fixes: invoke refactor-pipeline
• For production-impacting fixes: invoke incident-response to coordinate the fix with rollback plan, comms, and post-mortem

Phase 6 — Capture (always)

• Invoke adr-write if the bug revealed a structural issue worth recording
• Add a regression test (don't skip — that's how the bug comes back)
• Invoke knowledge-loop to capture the debugging path for next time

Reconciliation

DEBUG DEEP — <bug summary>
  Phase 1 Hypotheses:    N candidates ranked
  Phase 2 Evidence:      <strongest hypothesis, confidence>
  Phase 3 Production:    <Sentry frequency, affected scope>
  Phase 4 Regression:    introduced in commit <SHA> (<date>)
  Phase 5 Fix:           <commit / PR / incident ref>
  Phase 6 Captured:      <ADR path, regression test path>

Outputs / Evidence

• Hypothesis tree (Phase 1)
• Evidence collected per hypothesis
• Sentry frequency data
• Bisect result
• Fix commit/PR
• Regression test
• ADR if structural

Failure / Stop Conditions

• Hypothesis tree has zero high-confidence winners after Phase 2 → stop, do not guess; surface the tree to user with recommended next probes
• Sentry inaccessible → continue without Phase 3, mark report as PARTIAL
• Bisect not viable (force-pushed history) → skip Phase 4, rely on hypothesis tree
• Production fix without rollback plan → block; require incident-response