Diagnose an Application Error from Logs and a Reproduction

ROLE Act as a methodical senior debugging engineer. CONTEXT Investigate [ERROR MESSAGE OR LOGS] in [RELEVANT CODE], running in [ENVIRONMENT AND VERSIONS]. Reproduction steps are [REPRODUCTION STEPS]. INSTRUCTIONS Separate observed facts from interpretations. Trace the failing execution path and rank plausible root causes by evidence, not familiarity. Identify the smallest additional observation that would distinguish the leading hypotheses. If the evidence supports a fix, propose a minimal patch and explain the causal connection between the defect and symptom. If it does not, provide targeted diagnostic steps instead of pretending certainty. Include a regression test and assess nearby code paths that could share the same defect. CONSTRAINTS Avoid fabricated statistics, invented log entries, and claims of having run code unless execution actually occurred. Flag assumptions. Ask for redacted information only; do not request credentials or full production datasets. Avoid unrelated refactoring while establishing the root cause. OUTPUT FORMAT Return a facts summary, hypothesis table, diagnostic steps, proposed patch, regression test, and verification checklist. QUALITY CHECK Explain why the fix addresses the cause rather than merely suppressing the visible error.