Browser reports · Server decides

Last-Event-ID recovery on SSE reconnect

1 · stream 2 · drop 3 · reconnect 4 · replay

Browser

EventSource client

                remembered
              

                lastEventId
                —
              

                received
              

›_ node sse-server.js

Server

SSE producer

                emitted
              

                server decides
              

Replay missed id>3

Send snapshot state now

Ignore start fresh

✕

              connection lost
            