diff --git a/src/everything/resources/subscriptions.ts b/src/everything/resources/subscriptions.ts
index 854a8633a2..9d2044147c 100644
--- a/src/everything/resources/subscriptions.ts
+++ b/src/everything/resources/subscriptions.ts
@@ -166,3 +166,22 @@ export const stopSimulatedResourceUpdates = (sessionId?: string) => {
     subsUpdateIntervals.delete(sessionId);
   }
 };
+
+/**
+ * Removes a session from every URI's subscriber set, dropping any URI entry
+ * that ends up with no remaining subscribers.
+ *
+ * A session that disconnects without explicitly unsubscribing otherwise stays
+ * in `subscriptions` for the life of the process. Call this from the
+ * transport's `cleanup(sessionId)` when a session ends.
+ *
+ * @param {string} [sessionId]
+ */
+export const removeSubscriber = (sessionId?: string) => {
+  for (const [uri, subscribers] of subscriptions) {
+    subscribers.delete(sessionId);
+    if (subscribers.size === 0) {
+      subscriptions.delete(uri);
+    }
+  }
+};
diff --git a/src/everything/server/index.ts b/src/everything/server/index.ts
index f1459cc812..182a5a084a 100644
--- a/src/everything/server/index.ts
+++ b/src/everything/server/index.ts
@@ -6,6 +6,7 @@ import {
 import {
   setSubscriptionHandlers,
   stopSimulatedResourceUpdates,
+  removeSubscriber,
 } from "../resources/subscriptions.js";
 import { registerConditionalTools, registerTools } from "../tools/index.js";
 import { registerResources, readInstructions } from "../resources/index.js";
@@ -110,6 +111,8 @@ export const createServer: () => ServerFactoryResponse = () => {
       // Stop any simulated logging or resource updates that may have been initiated.
       stopSimulatedLogging(sessionId);
       stopSimulatedResourceUpdates(sessionId);
+      // Drop this session from any resource subscriptions it left open.
+      removeSubscriber(sessionId);
       // Clean up task store timers
       taskStore.cleanup();
       if (initializeTimeout) clearTimeout(initializeTimeout);