Diagnose

A discipline for hard bugs. Skip phases only when explicitly justified.

Before exploring the codebase, follow ../domain-modeling/DOMAIN-AWARENESS.md. Use the CONTEXT.md vocabulary to get a clear mental model of the relevant modules.

Phase 1 — Build a feedback loop

This is the skill. Everything else is mechanical. If you have a tight pass/fail signal for the bug — one that goes red on this bug — you will find the cause; bisection, hypothesis-testing, and instrumentation all just consume it. If you don't have one, no amount of staring at code will save you.

Spend disproportionate effort here. Be aggressive. Be creative. Refuse to give up.

Ways to construct one — try them in roughly this order