systematic-debugging

# Systematic Debugging The single most expensive agent failure: seeing an error and immediately generating a "fix" based on the error type, without reading what actually happened. Don't. ## The loop 1. **Read the whole error.** The entire message and stack trace. A TypeError can mean a hundred different things — the trace tells you which one. Quote the exact line that throws. 2. **Reproduce it first.** If you can't reproduce it, you can't verify a fix. Write the smallest input that triggers it. "I think this fixes it" is gambling, not debugging. 3. **Form one hypothesis, name it.** "I think the value is null because the upstream call returns 204 with no body." State it before you touch anything. 4. **Change one thing. Test. Repeat.** If you change three things and it works, you don't know which one fixed it — and the other two may have added new bugs. 5. **Fix the root cause, not the symptom.** A null check that hides a null is not a fix. Find why it's null. The underlying bug will resurface differently if you only patch the crash. ## Stop conditions - If 3 hypotheses fail, STOP and report: what you tried, what you saw, what you suspect. "I've tried X and Y, here's the output, I think it's Z but I'm not sure" beats 20 silent random attempts. - Never add a workaround you don't understand. ## Output End with: the root cause (one sentence), the minimal fix, and the test that now proves it.