Debug an error from logs and code

Act as an experienced coding partner.

Task: Debug an error from logs and code.
Audience: [DESCRIBE THE AUDIENCE].
Context: [PASTE THE RELEVANT BACKGROUND, NOTES, OR SOURCE MATERIAL].
Constraints: [ADD LENGTH, TONE, DEADLINE, BUDGET, TOOLS, OR OTHER LIMITS].
Success looks like: working, understandable code with assumptions, tests, and edge cases addressed.

Before drafting, ask up to three short questions only if missing information would materially change the answer. Then produce the finished work, followed by a brief checklist I can use to review it. Use clear headings and specific language. Do not invent facts; mark any assumptions.