htmx-stream

HTMX + Server-Sent Events streaming

An HTMX page that subscribes to an SSE endpoint and updates a DOM element in real time as the server streams events. Demonstrates:

• Setting the SSE response headers correctly (text/event-stream, no-cache, keep-alive).
• Using http.Flusher to push individual events.
• Cleanly stopping on r.Context().Done() when the client disconnects.
• Pairing this with the htmx-sse extension on the browser side.

Run

cd examples/htmx-stream
go run .

Open http://localhost:8080. A random integer streams to the page every 100 ms. Close the tab and the goroutine exits — context cancellation is the only stop signal.

Event IDs

An application can attach an ID to an event:

msg := hyperserve.NewSSEMessage("ready")
msg.Event = "status"
msg.ID = "42"
fmt.Fprint(w, msg)

This adds id: 42 before the data lines. An empty ID omits the field and leaves the client's last event ID unchanged. IDs containing CR, LF, NUL, or invalid UTF-8 are omitted entirely; they are never rewritten into another ID. To deliberately reset the client's last event ID, write id:\n\n directly to the stream and flush it.

ID assignment, persistence, and replay from Last-Event-ID belong to the application. This random-number example does not retain events for replay. See the SSE specification for the browser's reconnection behavior.

Notes

This example uses raw text/event-stream for direct HTMX consumption. MCP's separate request-scoped SSE behavior is covered under resource subscriptions.