Fiber

A Fiber is dope’s async task. You write an ordinary async fn; the runtime runs it as a Fiber on one core. That’s the whole idea — it’s the async / await layer over the Manifold event machinery.

your async fn

→

Fiber branded to one core

→

one core never leaves it

Every fiber is branded to the core it was created on. You can’t send it to another thread — not by convention, by the type system. “Don’t move this across threads” is a compile error, not a code-review note. So fiber futures carry no Send bound; they don’t need one, and adding one would be a lie about how they run.

Day-to-day async code lives here: Connector / Listener front-ends, Io / Sleep, combinators, a Holding handle to a manifold-owned resource. The wakers behind it are the runtime’s Cell-based pointers — no atomic wakers, because a fiber is only ever woken on its own core.

	Manifold	Fiber
level	event state machine	async / await
you write	a machine over Events	ordinary async fn
crosses threads	never	never (enforced by the brand)

Most application code — including the handlers you write in sark — is fibers. Manifolds are the substrate they run on.