Systematic Debugging

Overview

Find root causes quickly using a proven four-phase process: reproduce, isolate, identify, and verify.

When to Use This Skill

✅ Complex bugs with unclear causes ✅ Production incidents requiring fast resolution ✅ Multi-component failures ✅ Intermittent issues ✅ Performance problems

The Four Phases

Phase 1: REPRODUCE

Create a reliable, minimal reproduction case:

• Document exact steps to trigger the bug
• Capture environment (OS, version, config)
• Simplify the scenario - remove unnecessary variables
• Make it consistent - bug should happen every time
• Save test data for later verification

Phase 2: ISOLATE

Narrow down where the bug occurs:

• Binary search through code layers (frontend/backend/db)
• Eliminate components - what's NOT involved?
• Add logging strategically to trace execution
• Test hypotheses one at a time
• Document what you ruled out

Phase 3: IDENTIFY

Find the exact root cause:

• Examine the isolated code carefully
• Check assumptions - what did you think was true?
• Look for edge cases and boundary conditions
• Review recent changes that might be related
• Verify data flow through the system

Phase 4: VERIFY

Confirm the fix actually resolves the issue:

• Apply the minimal fix that addresses root cause
• Test with original reproduction case
• Add regression test to prevent recurrence
• Check for similar issues elsewhere in codebase
• Document the fix for future reference

Common Debugging Mistakes

❌ Skipping straight to fixes without understanding ❌ Making multiple changes at once ❌ Not documenting what you tried ❌ Fixing symptoms instead of root causes ❌ Not verifying the fix works long-term

Questions Claude Will Ask

To help debug systematically:

1. What were you doing when the bug occurred?
2. What did you expect to happen vs. what actually happened?
3. Can you reproduce this consistently?
4. What have you already tried?
5. What environment are you running in?

Integration with Claude

When debugging, say:

• "Help me debug [issue] systematically"
• "I'm seeing [error], let's work through it methodically"
• "Let's isolate where this bug is occurring"

Claude will:

• Guide you through all four phases
• Prevent jumping to conclusions
• Help document your findings
• Suggest targeted tests
• Ensure you verify the fix