Claude Code Prompt to Debug Complex Issues to Root Cause

What this prompt does

This prompt forces Claude Code to debug the way a senior engineer does: methodically, not by pattern-matching the first plausible cause. It works because the template front-loads the model with the exact context a real debugger needs — severity, framework, the symptom, the trigger_condition, concrete steps, and the raw error_message — then locks the response into five ordered steps: read the stack trace, find the root cause, check connected components, propose a coded fix, and write a regression test.

The ordering is the leverage. By demanding root cause before a fix (step 2 before step 4), it stops the model from slapping a try/catch on the symptom. Step 3 — checking related components — is what catches the second bug hiding behind the first: the stale cache, the missing index, the race the original trace only hinted at. And step 5 turns the fix into something permanent, because a bug without a failing test is a bug you'll ship again.

When to use it

• A production exception with a stack trace you can paste, but no obvious culprit in the top frame.
• Intermittent or "works on my machine" bugs where the trigger_condition matters more than the code.
• Errors that surface far from their cause — a null deep in a service, a 500 from a swallowed upstream failure.
• Cross-layer issues: controller to service to model to DB, or frontend state to API to cache.
• Inherited or unfamiliar code where you need the connected-component scan to map blast radius.
• Any fix you intend to merge, because step 5 hands you the regression test to lock it down.

Example output

1. Stack trace: Error "Attempt to read property 'tier' on null"
   at OrderService.php:88 — $order->customer->tier.
2. Root cause: guest checkouts have customer_id = NULL; tier is read
   unconditionally. Symptom (the null-property error) ≠ cause (a
   nullable relation treated as always-present).
3. Related: PricingController and the invoice mailer hit the same
   getter — both crash on guest orders too.
4. Fix:
   $tier = $order->customer?->tier ?? Tier::GUEST;
5. Regression test:
   test_guest_order_prices_without_customer() — assert no exception,
   GUEST tier applied.

Pro tips

• Make error_message the full trace, not the one-line summary. The frames below the top are where root cause usually lives — truncating them is the most common reason the answer stays shallow.
• Be precise in trigger_condition. "After deploy, only for guest users" narrows the search far more than "sometimes." Intermittent bugs are won or lost here.
• Set severity honestly — "production data corruption" vs "console warning" changes how aggressively the model weighs a hotfix against a clean fix.
• Pin framework to a version (Laravel 11, React 18). Lifecycle and API behavior differ enough that a generic answer can be wrong for your stack.
• Pair it with the model's file access: after it names a root cause, ask it to open the connected components from step 3 and confirm the hypothesis against the actual code before you apply the fix.