Fix useSyncExternalStore by returning a stable store from ManagedToolsState.getStore() and resolving the store once in useManagedTools for subscribe and getSnapshot.

Author: BobDickinson

core/mcp/state/managedToolsState.ts

@@ -24,6 +24,10 @@ export class ManagedToolsState {
   private readonly store = createStore<{ tools: Tool[] }>()((_set) => ({
     tools: [],
   }));
+  private readonly readOnlyStore: ManagedToolsReadOnlyStore = {
+    getState: () => this.store.getState(),
+    subscribe: (listener) => this.store.subscribe(listener),
+  };
   private client: InspectorClient | null = null;
   private unsubscribe: (() => void) | null = null;
   private _metadata: Record<string, string> | undefined = undefined;
@@ -56,10 +60,7 @@ export class ManagedToolsState {
 
   /** Read-only store for subscription (e.g. useStore(manager.getStore(), s => s.tools)). */
   getStore(): ManagedToolsReadOnlyStore {
-    return {
-      getState: () => this.store.getState(),
-      subscribe: (listener) => this.store.subscribe(listener),
-    };
+    return this.readOnlyStore;
   }
 
   getTools(): Tool[] {

core/react/useManagedTools.ts

@@ -17,9 +17,10 @@ const NOOP_SUBSCRIBE = () => () => {};
 export function useManagedTools(
   managedToolsState: ManagedToolsState | null | undefined,
 ): UseManagedToolsResult {
+  const store = managedToolsState?.getStore() ?? null;
   const tools = useSyncExternalStore(
-    managedToolsState?.getStore()?.subscribe ?? NOOP_SUBSCRIBE,
-    () => managedToolsState?.getStore()?.getState()?.tools ?? EMPTY_TOOLS,
+    store?.subscribe ?? NOOP_SUBSCRIBE,
+    store ? () => store.getState().tools : () => EMPTY_TOOLS,
   );
 
   const refresh = useCallback(