Edge cases for this feature

Before QA finds them for you, loudly.

Brainstorm edge cases for the feature below. Cover empty and enormous inputs, wrong types, interrupted flows, duplicate submissions, and anything about time zones or locales that could bite. Group them by how likely they are in reality, and mark which ones I can reasonably ignore.

Feature:

Finding coverage gaps. Working out which behaviours, edge cases and error paths nothing currently checks.