From 2b6a163a683bc562cb025d5c76bdc35ea0694e87 Mon Sep 17 00:00:00 2001
From: Seal Wang <soulmatelynch@outlook.com>
Date: Tue, 1 Sep 2026 18:50:26 +0800
Subject: [PATCH 1/2] fix(server): complete empty listen subscriptions

---
 packages/server/src/server/listenRouter.ts    | 11 +++++++-
 .../server/createMcpHandlerListen.test.ts     | 26 +++++++++++++++++++
 2 files changed, 36 insertions(+), 1 deletion(-)

diff --git a/packages/server/src/server/listenRouter.ts b/packages/server/src/server/listenRouter.ts
index 40c4a38cf2..64e1f302ca 100644
--- a/packages/server/src/server/listenRouter.ts
+++ b/packages/server/src/server/listenRouter.ts
@@ -213,6 +213,15 @@ export function createListenRouter(options: ListenRouterOptions): ListenRouter {
                 );
                 writeNotification(ack.method, ack.params);
 
+                // A stream that honoured no notification types can never
+                // deliver an event. Acknowledge that outcome, then complete
+                // it instead of retaining a socket, bus subscription, and
+                // keep-alive timer indefinitely.
+                if (Object.keys(honored).length === 0) {
+                    teardown(true);
+                    return;
+                }
+
                 // Only after the ack frame is enqueued does delivery activate.
                 unsubscribe = bus.subscribe(event => {
                     if (closed || !listenFilterAccepts(honored, event)) return;
@@ -232,7 +241,7 @@ export function createListenRouter(options: ListenRouterOptions): ListenRouter {
             }
         });
 
-        if (signal !== undefined) {
+        if (!closed && signal !== undefined) {
             if (signal.aborted) {
                 teardown(false);
             } else {
diff --git a/packages/server/test/server/createMcpHandlerListen.test.ts b/packages/server/test/server/createMcpHandlerListen.test.ts
index fe17aa7536..26118b720a 100644
--- a/packages/server/test/server/createMcpHandlerListen.test.ts
+++ b/packages/server/test/server/createMcpHandlerListen.test.ts
@@ -170,6 +170,32 @@ describe('createMcpHandler — subscriptions/listen', () => {
         await handler.close();
     });
 
+    it('acknowledges and completes an empty honored filter without opening a subscription', async () => {
+        vi.useFakeTimers();
+        try {
+            const subscribe = vi.fn(() => () => {});
+            const bus: ServerEventBus = { publish() {}, subscribe };
+            const handler = createMcpHandler(() => new McpServer({ name: 'no-listen-capabilities', version: '1.0.0' }), {
+                bus,
+                keepAliveMs: 1000
+            });
+
+            const response = await handler.fetch(listenRequest(12, { toolsListChanged: true }));
+            const text = await response.text();
+
+            expect(text).toContain('notifications/subscriptions/acknowledged');
+            expect(text).toContain('"notifications":{}');
+            expect(text).toContain('"resultType":"complete"');
+            expect(text.indexOf('notifications/subscriptions/acknowledged')).toBeLessThan(text.indexOf('"resultType":"complete"'));
+            expect(subscribe).not.toHaveBeenCalled();
+            expect(vi.getTimerCount()).toBe(0);
+
+            await handler.close();
+        } finally {
+            vi.useRealTimers();
+        }
+    });
+
     it('delivers only opted-in change types, each stamped with the subscription id', async () => {
         const handler = createMcpHandler(trivialFactory(), { keepAliveMs: 0 });
         const response = await handler.fetch(listenRequest(7, { toolsListChanged: true, resourceSubscriptions: ['file:///a'] }));

From c549642f07c2b494644c4a27d438c28ef08f3b9b Mon Sep 17 00:00:00 2001
From: Seal Wang <soulmatelynch@outlook.com>
Date: Fri, 4 Sep 2026 15:35:45 +0800
Subject: [PATCH 2/2] test(e2e): retain a subscribed stream for capacity guard

---
 .changeset/complete-empty-listen-subscriptions.md | 5 +++++
 test/e2e/scenarios/subscriptions.test.ts          | 2 +-
 2 files changed, 6 insertions(+), 1 deletion(-)
 create mode 100644 .changeset/complete-empty-listen-subscriptions.md

diff --git a/.changeset/complete-empty-listen-subscriptions.md b/.changeset/complete-empty-listen-subscriptions.md
new file mode 100644
index 0000000000..82b5e616c3
--- /dev/null
+++ b/.changeset/complete-empty-listen-subscriptions.md
@@ -0,0 +1,5 @@
+---
+'@modelcontextprotocol/server': patch
+---
+
+Complete subscriptions that do not honor any requested notification types instead of retaining an idle SSE connection.
diff --git a/test/e2e/scenarios/subscriptions.test.ts b/test/e2e/scenarios/subscriptions.test.ts
index ce644fa430..ef3a42e444 100644
--- a/test/e2e/scenarios/subscriptions.test.ts
+++ b/test/e2e/scenarios/subscriptions.test.ts
@@ -276,7 +276,7 @@ verifies('subscriptions:listen:capacity-guard', async () => {
                     jsonrpc: '2.0',
                     id,
                     method: 'subscriptions/listen',
-                    params: { _meta: modernEnvelopeMeta(), notifications: {} }
+                    params: { _meta: modernEnvelopeMeta(), notifications: { toolsListChanged: true } }
                 })
             })
         );