Server-initiated notifications/resources/list_changed over the standalone GET SSE stream (sessionful 2025). The add_resource tool registers a new resource on the session's instance, which emits the notification over the GET stream the client opened via
ClientOptions.listChanged; the client calls the tool and asserts the notification arrived.
The original timer-driven unsolicited push (server emits on its own schedule) was traded for this tool-triggered approach for CI determinism — the list_changed-over-standalone-GET behaviour is still demonstrated; "server pushes on its own schedule" is no longer shown.
HTTP-only, sessionful 2025 by definition.