Client queries and streams

Import ServerFn from effective-rsc/client to query a Server Function for a value or consume its stream. The helpers expose results as Effects, Streams, or atoms, with typed failures and cancellation.

Helper	Server return type	Client result
`ServerFn.query(fn)`	Non-stream value	Function returning `Effect<Output, ServerFnError>`
`ServerFn.queryAtom(fn)`	Non-stream value	`Atom.AtomResultFn<Args, Output, ServerFnError>`
`ServerFn.stream(fn)`	Effect `Stream<A>`	Function returning `Stream<A, ServerFnError>`
`ServerFn.streamAtom(fn)`	Effect `Stream<A>`	Atom of the latest chunk; may also fail with `Cause.NoSuchElementError` for an empty stream

Function helpers take the original encoded arguments: ServerFn.query(lookupAuthor)({ authorId }). Atom setters take an argument tuple: lookup([{ authorId }]).

Value helpers reject any return union containing a ReadableStream. Stream helpers require every return alternative to be a ReadableStream, as exposed by a streaming Server Function reference.

Queries and streams do not trigger a route refresh. For React forms and useActionState, pass the native Server Function reference directly.

Cancellation and atoms

Interrupting a query Effect cancels its pending invocation. A stream consumer owns its browser request through completion or interruption. Each atom helper supersedes its own in-flight run when called again; Atom.Interrupt cancels it explicitly. Plain query calls run independently.

With @effect/atom-react, provide a RegistryProvider above consumers; a Client Component wrapper can be rendered by the root Layout. A nested provider gives its subtree a separate registry. useAtomInitialValues can seed values. Shared atom instances share state within that registry; create separate instances when reads should be independent.

Read successes and failure causes from AsyncResult. streamAtom keeps the latest chunk; Atom.pull can accumulate chunks from an Effect Stream. Pulling does not add network backpressure.