server-sent-events-tests

Tests the SSE surfaces per the [WHATWG SSE spec]: stream format, readyState lifecycle, Last-Event-ID reconnect-with-replay, and the HTTP/1.1 connection-pool ceiling.

When to use

• Real-time UI updates that don't need bidirectional communication (notifications, log tailers, build status, score tickers).
• Pre-deploy gate: SSE retry interval, replay via Last-Event-ID, and HTTP/1.1 connection limits all behave as designed.

Step 1 - Server-side event stream format

Per the [WHATWG SSE spec], response must use Content-Type: text/event-stream (UTF-8) and stream lines: