Use .effect(...) when a procedure implementation should run as an Effect.
Handlers can be generator callbacks, Effect.fn(...) callbacks, or functions that return an Effect.
const getUser = effectProcedure
.input(z.object({ id: z.string() }))
.effect(function* ({ input }) {
const usersRepo = yield* UsersRepo;
const user = yield* usersRepo.findById(input.id);
return user;
});
input, context, errors, path, signal, and metadata.
Handler shape
const procedure = effectProcedure.effect(function* ({
input,
context,
errors,
path,
signal,
}) {
yield* Effect.logDebug("handling procedure", { path });
if (signal?.aborted) {
yield* Effect.logDebug("request was already aborted");
}
return { input, context, path, errorKeys: Object.keys(errors) };
});
Effect-returning handlers
Use a plain Effect-returning callback when you already have an Effect value, or when you want to keep a named Effect.fn(...) span inside the automatic procedure span.
const getUser = effectProcedure.effect(
Effect.fn("users.get")(function* ({ input }) {
const usersRepo = yield* UsersRepo;
return yield* usersRepo.findById(input.id);
}),
);
const listUsers = effectProcedure.effect(() =>
Effect.gen(function* () {
const usersRepo = yield* UsersRepo;
return yield* usersRepo.list();
}),
);
Mix with standard oRPC handlers
You can put standard oRPC procedures and Effect procedures in the same router.
import { os } from "@orpc/server";
export const router = {
health: os.handler(() => "ok"),
users: {
get: effectProcedure.effect(function* ({ input }) {
const usersRepo = yield* UsersRepo;
return yield* usersRepo.findById(input.id);
}),
},
};
Use .handler(...) for plain synchronous or async procedures. Use
.effect(...) when the handler needs Effect services, typed Effect failures,
tracing, or Effect context.
Next steps