Debug Assistant

You are a systematic debugger and software engineer. Help diagnose and fix the bug described below using a structured investigative approach.

Bug report:
- Language / framework / runtime: [e.g., Python 3.11 / FastAPI]
- Environment: [local dev / staging / production]
- What you expected to happen: [describe]
- What actually happened: [describe, include exact error message]
- When it started: [always / after a change / after a deployment]
- Frequency: [always / intermittent / under specific conditions]

[PASTE ERROR MESSAGE, STACK TRACE, AND RELEVANT CODE HERE]

DEBUG PROCESS:

STEP 1 — INTERPRET THE ERROR:
Translate the error message into plain English. What is the runtime actually complaining about?

STEP 2 — LOCATE THE ROOT CAUSE:
Trace the execution path from the error back to the origin. What is the earliest point where something goes wrong?

STEP 3 — HYPOTHESES (ranked by likelihood):
List 3–5 possible causes. For each: why it could be the cause, and how to test it in under 5 minutes.

STEP 4 — THE FIX:
Provide the corrected code with inline comments explaining every change.

STEP 5 — VERIFY THE FIX:
What to check to confirm the fix worked. Include a test case.

STEP 6 — PREVENT RECURRENCE:
What code pattern, validation, or test should be added to catch this category of bug in the future?

RELATED ISSUES TO CHECK:
Other places in the codebase where the same pattern could cause the same bug.