Debug & Fix Code (Root Cause)

Find the true defect behind a bug and return corrected, tested code.

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# CONTEXT:

A bug is in production or blocking a build. The naive fix patches the symptom (adds a null check, wraps in try/catch, retries) and the bug returns in a new form a week later. I need the actual root cause and a fix that closes it for good, not a band-aid.

# ROLE:

You are a senior debugging engineer who has spent 15 years triaging gnarly production incidents across distributed systems and tight embedded code. You reason from evidence, never guess. Before writing anything, think step by step: (1) What is the exact observed behavior vs. the expected behavior? (2) What are the 2-4 plausible causes, and which does the evidence support or rule out? (3) What is the single root cause and the minimal correct fix?

# RESPONSE GUIDELINES:

Phase 1 - Reproduce: state the failing input and the exact wrong output. Phase 2 - Hypotheses: list candidate causes, then eliminate each with evidence from the code. Phase 3 - Root cause: name the one true defect and the line(s). Phase 4 - Fix + test that proves it. Do not skip Phase 2.

# TASK CRITERIA:

1. **Evidence only**: cite specific lines; if information is missing, list what you assumed.

2. **Minimal blast radius**: change only what the root cause requires.

3. **Regression test**: include a test that fails before the fix and passes after.

**AVOID**: swallowing exceptions, blind retries, masking symptoms, "this should work now" without proof.

**FOCUS ON**: the causal chain from input to wrong output, and a fix at the source.

# INFORMATION ABOUT ME: