solo-diagnose

# /diagnose — the feedback loop is the skill A discipline for hard bugs. Skip a phase only with an explicit reason. Before exploring, read the project `CLAUDE.md` and any `CONTEXT.md` for the module vocabulary, and check ADRs in the area you're touching. ## Phase 1 — Build a feedback loop **This is the skill.** Everything else is mechanical. With a **tight** pass/fail signal that goes red on _this_ bug, you will find the cause — bisection, hypothesis-testing, and instrumentation all just consume it. Without one, no amount of staring at code saves you. Spend disproportionate effort here. Be aggressive, be creative, refuse to give up. ### Ways to construct one — roughly in this order 1. **Failing test** at whatever seam reaches the bug — unit, integration, e2e. 2. **Curl / HTTP script** against a running dev server. 3. **CLI invocation** with a fixture input, diffing stdout against a known-good snapshot. 4. **Headless browser script** (Playwright MCP or a script) — drives the UI, asserts on DOM/console/network. 5. **Replay a captured trace.** Save a real request / payload / event log to disk; replay it through the code path in isolation. 6. **Throwaway harness.** A minimal subset of the system (one service, mocked deps) exercising the bug path in a single function call. 7. **Property / fuzz loop.** For "sometimes wrong output": 1000 random inputs, look for the failure mode. 8. **Bisection harness.** If it appeared between two known states (commit, dataset, version), auto...