When is IAsyncEnumerable<T> useful, and what cancellation and resource-lifetime issues do you handle?

In production I keep the resource lifetime and transport contract explicit. A database context or reader must remain alive for the enumeration, which can make returning an async sequence from a broad repository abstraction risky. For HTTP streaming I account for headers, partial responses, client disconnects, serialization format, proxy buffering, and the fact that an error after bytes are sent cannot become a normal error response. I bound producer work, propagate cancellation, and avoid yielding tracked entities that outlive their intended context. When consumers need retries, sorting, total counts, or repeatable access, a paged or materialized contract may be more honest than a stream.