Mace-Enterprise Systematic debugging
Fix the cause, not the symptom. (Adapted discipline — our own wording.)
Phase 1 — Reproduce
Get a reliable repro + the exact expected vs actual. No repro → make the smallest input that triggers it first.
Phase 2 — Isolate / trace
Narrow where behavior diverges: bisect, log at boundaries, check assumptions with evidence, not guesses. One hypothesis at a time; test it before the next. Trace backward: a bug usually surfaces deep in the call chain — follow it up (what called this? what value was passed? where did that value originate?) to the original trigger, not the place the error shows. To trace, instrument before the dangerous operation (log inputs + a captured stack), not after it fails.
Phase 3 — Fix at the root
Fix the actual cause. If you can't name the cause, you're not in Phase 3 yet — go back to Phase 2. Where it pays, add defense-in-depth — validate at each layer so the same bug becomes impossible, not just absent here.
Phase 4 — Defend
Add a test/check that would have caught it (regression); confirm it fails-before / passes-after.
Discipline
No shotgun edits — change one thing, observe, keep or revert. Show the result on sample data, not just "fixed" (see [[karpathy-loop-and-agent-discipline]]). If stuck after 2–3 hypotheses, report back with what's ruled out — don't spiral.
Verify before you claim it's fixed (iron rule)
No completion claim without fresh verification evidence in this same turn. Before saying fixed/passing/done: identify the command that proves it → run it fully → read the actual output (exit code, failure count) → only then state the result with that evidence. "Should work", "looks right", a previous run, or a subagent's success report are not evidence — re-run and check the diff. Skipping this is lying, not finishing.