Netlify Edge Functions empirically cap a single streaming response at
~60s wall-clock, regardless of activity. Confirmed against Netlify's
own canonical SSE example (edge-functions-examples.netlify.app/sse)
which also cuts at +60.1s. The Anthropic Managed Agent session is
fine for several minutes; the cap is per-HTTP-response.
This commit splits a long brief across multiple HTTP responses, while
keeping the UX of one continuous stream:
netlify/edge-functions/agent-proxy.ts
- Accept either a new-session payload {stationName, stationLocation,
stationWebsite} or a resume payload {sessionId, lastEventId,
startedAt}.
- On resume, skip session creation + user.message send. Just reopen
the live SSE stream and backfill via
GET /v1/sessions/{id}/events?after_id=lastEventId (deduped by
event.id), then keep tailing.
- Single AbortController per segment. A 54s timer aborts the upstream,
the for-await loops exit, and we write one final NDJSON line:
{type:'segment_end', sessionId, lastEventId, startedAt}.
- The 20-min OVERALL_BUDGET_MS is enforced via Date.now() - startedAt
so it spans across all segments.
- Refactor main loop so every iteration is openStream + backfill +
tail. Cleaner than the previous initial-stream + reconnect-only-on-
drop pattern.
src/App.jsx
- readStream() now returns a {sessionId, lastEventId, startedAt}
payload if it saw a segment_end, or null if the stream ended
cleanly.
- handleSubmit() loops, reopening /api/agent-proxy with the resume
payload until readStream returns null. Spinner/status state stays
on across segments so the UI shows one continuous stream.
README.md
- Document the segmented-streaming protocol and why it exists.
Co-Authored-By: alex <alex@semipublic.co>
Devin AI
8e44de5271