Debug Probe

Quick Start

When you hit a bug that reading code can't resolve:

1. Hypothesize — Read source, generate 2-4 falsifiable hypotheses
2. Instrument — Insert minimal logging (2-4 points per hypothesis), tag [DIAG_\x3Ctopic>]
3. Collect — Build → user reproduces → user exports logs
4. Converge — Match logs to hypotheses → confirm root cause
5. Fix — Minimal fix → verify with user
6. Clean up — Remove ALL instrumentation, confirm build passes

Never skip to fixing. Always clean up after.

The 6 Phases

Phase 1: Hypothesize

Read relevant source code. Generate 2-4 testable hypotheses:

[H1] Root cause may be X → if true, log would show Y
[H2] Root cause may be Z → if true, log would show W

Share hypotheses with user before touching code.

Phase 2: Instrument

Rules:

• Only instrument to test hypotheses — no fishing expeditions
• Tag format: [DIAG_\x3Ctopic>] (short topic like auth, render, state)
• 2-4 instrumentation points per hypothesis
• Mark ALL temporary code: // DIAG: remove after debug (adapt comment syntax to language)
• Set up a diagnostic buffer (pick from TEMPLATES.md)

Use diagLog('H1', 'key=val', ...) — outputs to both console and an in-memory buffer so users can export all logs at once after reproducing the bug.

Phase 3: Collect

1. Build & deploy
2. User reproduces the bug
3. User exports logs (dump function, console output, log file, etc.)
4. Group logs by hypothesis tag ([DIAG][H1], [DIAG][H2])
5. If expected paths aren't hit → is instrumentation on the right branch? → adjust and rebuild

Phase 4: Converge

Max 2-3 iterations before escalating.

Phase 5: Fix & Verify

1. Minimal fix targeting confirmed root cause
2. Build → user verifies fix works
3. Fix fails → keep key instrumentation, return to Phase 1
4. Fix works → Phase 6

Phase 6: Clean Up

Mandatory. Search for DIAG: remove after debug and:

1. Remove all temporary instrumentation code
2. Remove all diagnostic imports
3. Remove diagnostic buffer file if no longer referenced
4. Build to confirm compilation passes
5. Tell user: instrumentation removed, only fix remains

Anti-Patterns

• ❌ Skip hypotheses, jump straight to "fixing"
• ❌ Instrument 10+ points — precision beats coverage
• ❌ Dump entire objects — signal drowns in noise
• ❌ Forget Phase 6 cleanup — instrumentation rots
• ❌ Claim "done" without user verification
• ❌ Use raw console.log / print — use the diag buffer pattern