Documentation Index
Fetch the complete documentation index at: https://mintlify.com/middleapi/orpc/llms.txt
Use this file to discover all available pages before exploring further.
oRPC supports server-sent events (SSE) and streaming through async iterators. The same type safety that applies to regular procedures extends to streaming responses.
eventIterator()
Use the eventIterator() helper (re-exported from @orpc/contract) to define a typed async generator:
import { eventIterator, os } from '@orpc/server'
import * as z from 'zod'
const subscribe = os
.input(z.object({ topic: z.string() }))
.output(
eventIterator(
z.object({ message: z.string(), timestamp: z.number() }),
),
)
.handler(async function* ({ input }) {
while (true) {
const event = await waitForNextEvent(input.topic)
yield { message: event.text, timestamp: Date.now() }
}
})
for await (const event of await orpc.subscribe({ topic: 'news' })) {
console.log(event.message, event.timestamp)
}
EventPublisher
For pub/sub patterns, use EventPublisher to broadcast events to multiple concurrent subscribers:
import { EventPublisher, os } from '@orpc/server'
import * as z from 'zod'
// A shared publisher — typically stored in app state or a Durable Object
const publisher = new EventPublisher<{
planetUpdated: { id: number; name: string }
}>()
// Subscribe procedure: streams events to the client
const subscribe = os
.output(eventIterator(z.object({ id: z.number(), name: z.string() })))
.handler(async function* ({ signal }) {
yield* publisher.subscribe('planetUpdated', { signal })
})
// Publish procedure: pushes an event to all subscribers
const publishUpdate = os
.input(z.object({ id: z.number(), name: z.string() }))
.handler(async ({ input }) => {
publisher.publish('planetUpdated', input)
})
id, event, retry) to individual events using withEventMeta:
import { withEventMeta, os } from '@orpc/server'
const subscribe = os
.output(eventIterator(z.string()))
.handler(async function* () {
yield withEventMeta('hello', {
id: '1',
event: 'greeting',
retry: 5000,
})
})
Stream utilities
@orpc/server re-exports several stream conversion utilities:
import {
eventIteratorToStream, // AsyncIterator → ReadableStream
eventIteratorToUnproxiedDataStream, // for raw data streams
streamToEventIterator, // ReadableStream → AsyncIterator
} from '@orpc/server'
Streaming procedures are not supported inside batch requests. Call them directly. 