c9d36b04bf
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.
73 lines
2.5 KiB
Markdown
73 lines
2.5 KiB
Markdown
---
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layout: default
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title: Subscriptions
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nav_order: 12
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redirect_from:
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- /server/notification-subscriptions/
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---
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# Subscriptions
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`subscriptions/listen` is the long-lived notification subscription stream of MCP 2026-07-28 (SEP-2575),
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replacing the legacy HTTP GET listening stream.
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## Subscribing
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The client opts in via the `notifications` filter (`toolsListChanged` / `promptsListChanged` / `resourcesListChanged` / `resourceSubscriptions`),
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the server acknowledges the honored subset with `notifications/subscriptions/acknowledged` as the first stream message,
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and every delivered notification carries the correlating `io.modelcontextprotocol/subscriptionId` in `_meta`.
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The honored subset follows the capabilities the server declares (`listChanged` and `subscribe` flags).
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The client opens the stream with a `subscriptions/listen` request:
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```json
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{
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"jsonrpc": "2.0",
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"id": "listen-1",
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"method": "subscriptions/listen",
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"params": {
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"notifications": { "toolsListChanged": true, "resourceSubscriptions": ["file:///a.txt"] },
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"_meta": {
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"io.modelcontextprotocol/protocolVersion": "2026-07-28",
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"io.modelcontextprotocol/clientInfo": { "name": "my_client", "version": "1.0.0" },
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"io.modelcontextprotocol/clientCapabilities": {}
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}
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}
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}
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```
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The first SSE event on the stream is the acknowledgement:
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```json
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{
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"jsonrpc": "2.0",
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"method": "notifications/subscriptions/acknowledged",
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"params": {
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"notifications": { "toolsListChanged": true, "resourceSubscriptions": ["file:///a.txt"] },
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"_meta": { "io.modelcontextprotocol/subscriptionId": "listen-1" }
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}
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}
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```
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## Transport Support
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The stream is served on the Streamable HTTP modern path; stdio answers `-32601`.
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## Limits and Keepalives
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Concurrent streams are capped by `max_listen_subscriptions:` (default 1000; pass `nil` to remove the cap), and each stream receives an SSE keepalive
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comment frame every `listen_keepalive_interval:` seconds (default 15) so a dropped connection frees its slot; pass `listen_keepalive_interval: nil`
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when an upstream proxy already keeps the stream alive.
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```ruby
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transport = MCP::Server::Transports::StreamableHTTPTransport.new(
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server,
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max_listen_subscriptions: 500,
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listen_keepalive_interval: 30,
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)
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```
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A stream stays open until the client closes the connection; on graceful shutdown via `transport.close`,
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each open stream receives its `subscriptions/listen` response before closing.
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See [Notifications](/server/notifications/) for the notification types themselves and their session scoping.
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