Eric Allam
1d13b7976a
## Summary
Realtime streams get a live "last value" mode: subscribe from the latest
record instead of replaying the whole history, keep memory bounded, and
resume across reloads. Plus a new `useSessionStream` hook for reading a
Session's channels from React.
## `useRealtimeStream`: start-from-latest, bounded, resumable
```tsx
const { parts, lastEventId } = useRealtimeStream<Frame>(runId, "frames", {
from: "latest", // skip history, only new records after connect
maxParts: 1, // keep just the most recent (bounded memory)
lastEventId: saved, // resume from a persisted cursor (survives reload)
onParts: (batch) => save(batch.at(-1)?.id), // per-batch event ids
accessToken,
});
```
`from`, `lastEventId` (option and return), and the batching also apply
to `streams.read()` and `fetchStream()`.
## `useSessionStream`: read a Session channel from React (new)
A read-only hook for a Session's `out` (default) or `in` channel, with
the same start / bound / resume options. `useSession` is reserved for
two-way (read and write).
```tsx
const { records, lastEventId } = useSessionStream<Frame>(sessionId, {
io: "out",
from: "latest",
maxRecords: 5,
onRecords: (batch) => {/* each throttled batch, with event ids */},
accessToken,
});
```
## Access-token refresh
Long-lived subscriptions can survive token expiry: pass
`refreshAccessToken` and a 401/403 triggers one re-mint and reconnect.
With no refresher, auth errors stay terminal exactly as before.
```tsx
const { parts } = useRealtimeStream<Frame>(runId, "frames", {
accessToken,
// called on a 401/403 to mint a fresh public token from your backend
refreshAccessToken: async () => {
const res = await fetch("/api/realtime-token");
return (await res.json()).token;
},
});
```
It is also available on `useApiClient` / `TriggerAuthContext`, so every
hook under a provider shares one refresher.
## Notes
Server support (S2 `tail_offset` / Redis `$`, and the start-position
header on the run and session SSE routes) ships here; a client passing
`from: "latest"` against an older server degrades safely to a full
replay. Resume, bounded memory, batched callbacks, and token refresh are
client-only.
Supersedes #4808 and #4809, folded in here. Verified end to end on an
isolated stack: `from: "latest"` on the run and session paths against
real S2, `lastEventId` resume across a reload, bounded memory, batched
callbacks, and a real 401 to token-refresh to reconnect.
Development
Install and initial setup
pnpm install
Running the app
pnpm run dev --filter docs
View the app locally
It runs locally here:
http://localhost:3050