systematic-debugginglisted

# Systematic Debugging ## Core Principle **NO FIXES WITHOUT ROOT CAUSE INVESTIGATION FIRST.** Never apply symptom-focused patches that mask underlying problems. Understand WHY something fails before attempting to fix it. ## The Four-Phase Framework ### Phase 1: Root Cause Investigation Before touching any code: 1. **Read error messages thoroughly** - Every word matters 2. **Reproduce the issue consistently** - If you can't reproduce it, you can't verify a fix 3. **Examine recent changes** - What changed before this started failing? 4. **Gather diagnostic evidence** - Logs, stack traces, state dumps 5. **Trace data flow** - Follow the call chain to find where bad values originate **Root Cause Tracing Technique:** ``` 1. Observe the symptom - Where does the error manifest? 2. Find immediate cause - Which code directly produces the error? 3. Ask "What called this?" - Map the call chain upward 4. Keep tracing up - Follow invalid data backward through the stack 5. Find original trigger - Where did the problem actually start? ``` **Key principle:** Never fix problems solely where errors appear—always trace to the original trigger. ### Phase 2: Pattern Analysis 1. **Locate working examples** - Find similar code that works correctly 2. **Compare implementations completely** - Don't just skim 3. **Identify differences** - What's different between working and broken? 4. **Understand dependencies** - What does this code depend on? ### Phase 3: Hypothesis and Testing Apply t