• Status: Accepted
• Date: 2026-09-14

Context

Using one shared asynchronous executor is efficient for the default case, but a slow backend can delay unrelated backends. A separate worker per backend improves isolation at the cost of a thread and queue per opted-in backend.

Decision

The shared TaskExecutor remains the default. Backends that support it expose Config::use_dedicated_executor; when enabled for an asynchronous backend, it owns a SingleThreadExecutor with its own queue, policy, wait, and shutdown lifecycle. Platform-specific backends that cannot provide this behavior keep their documented limitations.

Consequences

Applications can choose throughput/resource sharing or isolation per backend. The feature is already tested for lifecycle, mixed shared/dedicated operation, and macro configuration. Changing the default is a separate compatibility and resource-usage decision.