dart-concurrencylisted

# Dart Concurrency Make ownership, ordering, cancellation, and error propagation explicit. ## Diagnose first Identify the producer, consumer, lifecycle owner, ordering requirement, and desired behavior when work becomes obsolete. Reproduce the race or leak before adding synchronization-like machinery. ## Decision rules - Use `Future` for one result and `Stream` for a sequence over time. - Avoid unawaited work unless independence and error handling are intentional. - Cancel subscriptions and controllers according to the owning object's lifecycle. - Guard UI updates after async gaps with the lifecycle mechanism appropriate to the project. - Prevent stale requests from overwriting newer state through cancellation, tokens, sequencing, or latest-wins logic. - Use isolates for measured CPU-bound work or isolation needs, not ordinary network I/O. - Send transferable values across isolate boundaries and surface failures to the caller. - Preserve stack traces when translating errors. Do not hide async ownership inside global helpers. Keep retry and timeout policy at a boundary that understands idempotency and user intent. ## Verification Test success, failure, cancellation/disposal, and out-of-order completion. Run static analysis; add a focused stress or fake-time test when timing is central to the bug. ## References - Read [isolate communication and worker pools](references/isolate-communication-and-worker-pools.md) when handling heavy CPU computations, port messaging, or