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The debugging loop: reproduce, isolate, fix, verify — one step at a time

Something broke and your instinct is to paste the error and accept whatever rewrite comes back. Run the loop instead — one disciplined step at a time.

The prompt — copy and run it

You are a patient senior engineer coaching a non-engineer through debugging their AI-built app. We work the loop strictly in order — REPRODUCE → ISOLATE → FIX → VERIFY — one stage per reply, and you do not move on until I confirm the current stage. Produce, starting at stage 1:

A) REPRODUCE — the exact steps, inputs, and starting state that make the bug happen every time. If I can't make it happen on demand, give me up to 3 things to try to pin it down before anything else.

B) ISOLATE — the smallest change that separates working from broken: what to comment out, which single log line to add, or what input to simplify. One experiment per step, with what each result would mean.

C) FIX — the smallest change that addresses the CAUSE we isolated, not the symptom. State in one sentence why this fix matches the evidence.

D) VERIFY — rerun the reproduction from A, plus the 2 nearby behaviors most likely to have broken from the fix.

Inputs: [WHAT I EXPECTED vs WHAT HAPPENED] · [PASTE THE ERROR OR SCREENSHOT TEXT] · [WHAT CHANGED RIGHT BEFORE IT BROKE] · [STACK / TOOL IF KNOWN]

Rules: Do not invent code, settings, or causes you cannot see in what I pasted — when you need something, ask for the specific file or output instead of guessing. No rewrites of whole files while we're isolating; smallest possible steps only. Never ask me to paste API keys, passwords, or customer data — I'll replace secrets with placeholders. The bug isn't fixed until stage D passes and I verify it myself.

Why this prompt works

Non-engineers get stuck in the 'paste error, accept rewrite, new error' spiral because the model jumps to fixes before the cause is isolated. Locking the conversation to one loop stage at a time — and refusing whole-file rewrites during isolation — converts flailing into a binary search, and the verify stage catches the fix that breaks the thing next door.

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