sse-polling

SEP-1699 server-initiated SSE disconnection + client reconnection with Last-Event-ID replay. Sessionful 2025 by definition (the feature lives on NodeStreamableHTTPServerTransport + an EventStore). eventStore resumability is a 2025-session concern with no 2026-07-28 per-request equivalent.

The long-operation tool emits two log notifications, calls ctx.http?.closeSSE() mid-stream, emits two more while the client is disconnected, then returns. The client transport reconnects after retryInterval (300 ms) with Last-Event-ID; the event store replays the buffered events. The client asserts the result arrived AND the post-disconnect log was delivered.

pnpm --filter @mcp-examples/sse-polling server -- --http --port 3001    # term 1
pnpm --filter @mcp-examples/sse-polling client -- --http http://127.0.0.1:3001/mcp    # term 2

Source: examples/sse-polling/README.md