effect-scope

Use Effect.acquireRelease with an acquire effect and a release function; the release finalizer is registered on the current scope and runs when that scope closes. Wrap the usage in Effect.scoped to eliminate Scope from the requirements and bound the resource's lifetime to that block.

acquireRelease registers cleanup on the ambient Scope, so the resource can outlive a single callback, while acquireUseRelease brackets acquire, use, and release in one effect with no Scope requirement. Choose acquireUseRelease when the resource lifetime is exactly one callback.

No, Layer.scoped and Layer.scopedDiscard were removed in v4. Layer.effect and Layer.effectDiscard already eliminate Scope from the construction effect, releasing acquired resources when the layer is torn down.

Leaks happen when Scope is eliminated at the application root instead of the narrowest correct boundary, so every resource lives until the root scope closes. Place Effect.scoped close to each use site, or use per-item scopes inside loops.

Use ScopedRef.fromAcquire to hold a resource-backed reference, then ScopedRef.set to replace it; set acquires the replacement first and releases the previous value's scope. Replacement is synchronized and uninterruptible, and a failed acquisition leaves the current value untouched.