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Root-cause interrogation: a hypothesis ladder from a bug report
Prod bug, vague repro, clock ticking. Structure the investigation before you start changing code at random.
The prompt — copy and run it
You are a senior engineer running a structured root-cause investigation. I will paste the symptoms and every piece of evidence I have. Produce: A) HYPOTHESIS LADDER — 5 ranked hypotheses. For each: the mechanism, which pasted evidence supports or contradicts it, and the cheapest discriminating test (a log line to add, a git bisect range, a feature-flag toggle, a minimal repro). B) EVIDENCE GAPS — what I have not given you that would most change the ranking, in priority order. C) PREVENTION — run 5-whys on the top hypothesis and name the class-level fix (test, lint rule, alert, type change) that prevents the whole category from recurring. Inputs: [SYMPTOM + WHEN FIRST SEEN] · [PASTE LOGS / STACK TRACE / RECENT DIFFS] · [ENVIRONMENT + RECENT DEPLOYS] Rules: Do not invent stack frames, log lines, or code behavior not in my paste — every hypothesis must cite the evidence line it rests on, and pure speculation must be labeled as such. Verify the discriminating test's result before acting on any hypothesis. Strip credentials and user PII from anything you echo back.
How to use this prompt
- Copy the full prompt above with the Copy button.
- Fill in your inputs. Replace each bracketed placeholder with your specifics:
[SYMPTOM + WHEN FIRST SEEN][PASTE LOGS / STACK TRACE / RECENT DIFFS][ENVIRONMENT + RECENT DEPLOYS] - Paste into ChatGPT, Claude, or Gemini and run. Read the reality guardrail below before you act on the output.
Why this prompt works
Ranked hypotheses with discriminating tests is how senior engineers actually debug — it converts panic into a binary-search plan. The prevention step turns one fix into a class fix, which is the difference between closing a ticket and improving the system.
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When should I use this prompt?
Prod bug, vague repro, clock ticking. Structure the investigation before you start changing code at random.
Why does this prompt work?
Ranked hypotheses with discriminating tests is how senior engineers actually debug — it converts panic into a binary-search plan. The prevention step turns one fix into a class fix, which is the difference between closing a ticket and improving the system.
What mistake does this prompt help you avoid?
Panic debugging by changing code at random — ranked hypotheses with discriminating tests turn the hunt into a binary search, then a class fix.
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