effect-fiber

Use Effect.forkChild to attach a fiber to the parent, Effect.forkScoped to tie it to a Scope, or Effect.forkDetach for fully detached work. The v3 names Effect.fork and Effect.forkDaemon no longer exist in v4.

FiberHandle manages one fiber with latest-wins replacement, FiberMap manages keyed fibers where a new run under an existing key interrupts the previous one, and FiberSet is a grow-only collection with no replacement semantics. All three interrupt their fibers when the owning scope closes.

Forked fibers start on the next scheduler tick by default, and children forked with forkChild are interrupted when the parent completes. Use startImmediately: true, yield* Effect.yieldNow, or switch to forkScoped/forkDetach depending on the intended lifetime.

No, Fiber.await always succeeds with an Exit value for inspection. Use Fiber.join to propagate the fiber's failure into the current fiber, or inspect the Exit with Exit.isSuccess and Cause helpers.

Capture a synchronous runner with FiberHandle.runtime, FiberMap.runtime, or FiberSet.runtime inside a scoped effect, then call it from event handlers. For raw fibers, fiber.interruptUnsafe() sends an interruption signal without waiting.

Use Effect.all or Effect.forEach when you only need concurrent results; use FiberSet when you need lifecycle control over an unbounded set of background tasks. Bound admission with a Semaphore since FiberSet applies no backpressure on its own.