Async & Coroutine Patterns -- Correctness Patterns

Prerequisite skills: unity-scripting (coroutines, Awaitable API, yield types), unity-lifecycle (destruction timing, destroyCancellationToken)

These patterns target async bugs that are especially dangerous because they often work during testing and fail in production: exceptions silently swallowed, objects destroyed mid-await, and thread context violations.

PATTERN: Awaitable Double-Await

WHEN: Storing an Awaitable instance and awaiting it more than once

WRONG (Claude default):

Awaitable task = Awaitable.WaitForSecondsAsync(2f);
await task; // First await -- works
await task; // Second await -- UNDEFINED BEHAVIOR (may complete instantly or throw)