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Three pages carried names the 2026-07-28 specification does not use: "Multi-Round-Trip Results" for the pattern the specification titles Multi Round-Trip Requests (MRTR) and serves at basic/patterns/mrtr - the results are the `InputRequiredResult` wire type, not the feature - plus "Completions" for the utility the specification titles Completion, and "Notification Subscriptions" for the pattern it titles Subscriptions. Retitle the three pages to the specification's names, move them to /server/mrtr/ and /client/mrtr/, /server/completion/, and /server/subscriptions/ following the specification's slugs, update every internal reference, and keep the URLs published with v1.3.0 working via jekyll-redirect-from. The Discovery page keeps its title but moves from /server/discovery/ to /server/discover/, matching the specification's slug and the `server/discover` RPC, with its published URL redirected the same way.
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| layout | title | nav_order | redirect_from | |
|---|---|---|---|---|
| default | Subscriptions | 12 |
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Subscriptions
subscriptions/listen is the long-lived notification subscription stream of MCP 2026-07-28 (SEP-2575),
replacing the legacy HTTP GET listening stream.
Subscribing
The client opts in via the notifications filter (toolsListChanged / promptsListChanged / resourcesListChanged / resourceSubscriptions),
the server acknowledges the honored subset with notifications/subscriptions/acknowledged as the first stream message,
and every delivered notification carries the correlating io.modelcontextprotocol/subscriptionId in _meta.
The honored subset follows the capabilities the server declares (listChanged and subscribe flags).
The client opens the stream with a subscriptions/listen request:
{
"jsonrpc": "2.0",
"id": "listen-1",
"method": "subscriptions/listen",
"params": {
"notifications": { "toolsListChanged": true, "resourceSubscriptions": ["file:///a.txt"] },
"_meta": {
"io.modelcontextprotocol/protocolVersion": "2026-07-28",
"io.modelcontextprotocol/clientInfo": { "name": "my_client", "version": "1.0.0" },
"io.modelcontextprotocol/clientCapabilities": {}
}
}
}
The first SSE event on the stream is the acknowledgement:
{
"jsonrpc": "2.0",
"method": "notifications/subscriptions/acknowledged",
"params": {
"notifications": { "toolsListChanged": true, "resourceSubscriptions": ["file:///a.txt"] },
"_meta": { "io.modelcontextprotocol/subscriptionId": "listen-1" }
}
}
Transport Support
The stream is served on the Streamable HTTP modern path; stdio answers -32601.
Limits and Keepalives
Concurrent streams are capped by max_listen_subscriptions: (default 1000; pass nil to remove the cap), and each stream receives an SSE keepalive
comment frame every listen_keepalive_interval: seconds (default 15) so a dropped connection frees its slot; pass listen_keepalive_interval: nil
when an upstream proxy already keeps the stream alive.
transport = MCP::Server::Transports::StreamableHTTPTransport.new(
server,
max_listen_subscriptions: 500,
listen_keepalive_interval: 30,
)
A stream stays open until the client closes the connection; on graceful shutdown via transport.close,
each open stream receives its subscriptions/listen response before closing.
See Notifications for the notification types themselves and their session scoping.