fix(sse): flush stream headers eagerly so clients connect instantly#1295
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The SSE stream handler set the response headers and then entered the read loop without writing anything, so Kestrel buffered the headers until the first body write - which was the heartbeat up to 15s away. The browser's fetch() resolves on response headers, so the dashboard sat on "connecting" for up to 15s on every connect/reconnect with an idle stream. Write a no-op ":connected" SSE comment and flush immediately after Connect() so the headers go out at once and the client flips to "connected" right away. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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What
On the dashboard, the Overview "System status" card sat on Connecting ("Waiting for the stream to come online") for up to 15 seconds after every connect/reconnect on an idle stream.
Why
The client flips to Connected only when its
fetch()to/api/v1/sse/streamresolves — andfetch()on a streaming response resolves when the response headers arrive. The server handler (SseEndpoints.cs) set the headers and then entered the read loop without writing anything, so Kestrel buffered the headers until the first body write — which was the heartbeat, up toHeartbeatInterval(15s) away. With no traffic andEvents this session: 0, the browser sat pending the whole interval.How
Write a no-op
:connectedSSE comment and flush immediately afterConnect(), so the headers go out at once and the client connects instantly. Two lines.Notes
src/BuildingBlocks/Web/Sse(protected) — change is minimal and self-contained.Webproject builds clean (0 warnings).🤖 Generated with Claude Code