Debug and harden trial-assignment Python code

The simplified snippet has several serious correctness and reliability flaws that can corrupt experiment data, bias metrics, and cause operational failures in production. Below I identify ten distinct issues, describe their failure modes and impact on metrics, propose concrete fixes, and provide a hardened pseudocode sketch. 1. Non-deterministic assignment / lack of stickiness Failure mode random.random() is evaluated every time the function is called. The same user_id can…