Concurrency and State

Structured concurrency with fibers, shared state with Ref and STM, coordination with Deferred and Semaphore, retry and repeat with Schedule, and incremental data with FlowStream.

• Fibers: structured child fibers, fork/join, and interruption.
• Supervision: restart policies for failing workers.
• Ref: atomic single-variable updates.
• Deferred and Semaphore: coordination primitives.
• STM: multi-variable atomic transactions.
• Queue and Hub: value handoff between fibers.
• SubscriptionRef: current state consumers can join late.
• Cache and memoize: single-flight lookups.
• Scheduling and retries: Schedule with Flow.retry and Flow.repeat.
• Streams: incremental FlowStream data.

The torture tests run every construct in this section under interruption, failure, and shutdown, and check every guarantee it makes.