Try.withTimeout uses virtual threads (Thread.ofVirtual())

Context

Try.withTimeout needs to run user-supplied code with a wall-clock deadline. Options were:

• Platform threads via ExecutorService
• Virtual threads via Thread.ofVirtual()
• CompletableFuture with a shared pool

Decision

Use Thread.ofVirtual().start(task) to spawn a lightweight carrier for the timed operation. The calling thread blocks on FutureTask.get(timeout, unit) and interrupts the virtual thread on timeout.

Consequences

• No ExecutorService lifecycle to manage; threads are fire-and-forget.
• Near-zero overhead for blocking I/O inside the timeout block (virtual thread parks, not blocks a carrier).
• The CancellationException branch (external cancellation of the internal FutureTask) is unreachable from outside the method — accepted as an untestable defensive guard.
• Requires Java 21+ (virtual threads GA); already met by the Java 25 baseline (ADR-001).

Alternatives considered

• Platform threads via ExecutorService: requires lifecycle management and heavier overhead for blocking I/O.
• CompletableFuture with a shared pool: uses the common ForkJoin pool, which is inappropriate for blocking operations.