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>
The reconnect + events.list backfill in c283d88 is correct but never ran:
the previous v2 Node Function was killed at ~27 s (well before the 20 min
reconnect budget could matter), so streams always died after the first MCP
tool batch.
Move the proxy to a Netlify Edge Function (Deno runtime) which has no
streaming-duration cap as long as we keep writing to the response body.
Same reconnect / backfill / dedupe-by-event-id pattern; same NDJSON wire
protocol to the browser. Implemented with plain fetch() against the
Anthropic REST API (npm packages on Edge are beta) so we have no SDK
runtime dependency.
Frontend now POSTs to /api/agent-proxy. The Anthropic SDK is removed
from the package; @netlify/edge-functions is added for ambient types.
Co-Authored-By: alex <alex@semipublic.co>
Devin AI
alex