diff --git a/src/renderer/store/slices/extensionsSlice.ts b/src/renderer/store/slices/extensionsSlice.ts
index e18437ff..9d21f833 100644
--- a/src/renderer/store/slices/extensionsSlice.ts
+++ b/src/renderer/store/slices/extensionsSlice.ts
@@ -237,15 +237,19 @@ export const createExtensionsSlice: StateCreator<AppState, [], [], ExtensionsSli
           };
         });
       } catch (err) {
-        set(() => {
+        set((prev) => {
           if (requestSeq !== pluginCatalogRequestSeq) {
             return {};
           }
 
+          const nextProjectPath = projectPath ?? null;
+          const isSameProjectContext = prev.pluginCatalogProjectPath === nextProjectPath;
+
           return {
+            pluginCatalog: isSameProjectContext ? prev.pluginCatalog : [],
             pluginCatalogLoading: false,
             pluginCatalogError: err instanceof Error ? err.message : 'Failed to load plugins',
-            pluginCatalogProjectPath: projectPath ?? null,
+            pluginCatalogProjectPath: nextProjectPath,
           };
         });
       } finally {
@@ -263,7 +267,13 @@ export const createExtensionsSlice: StateCreator<AppState, [], [], ExtensionsSli
   fetchPluginReadme: (pluginId: string) => {
     if (!api.plugins) return;
     const state = get();
-    if (pluginId in state.pluginReadmes || state.pluginReadmeLoading[pluginId]) return;
+    const cachedReadme = state.pluginReadmes[pluginId];
+    if (
+      (cachedReadme !== undefined && cachedReadme !== null) ||
+      state.pluginReadmeLoading[pluginId]
+    ) {
+      return;
+    }
 
     set((prev) => ({
       pluginReadmeLoading: { ...prev.pluginReadmeLoading, [pluginId]: true },
diff --git a/test/renderer/store/extensionsSlice.test.ts b/test/renderer/store/extensionsSlice.test.ts
index 278f61e1..906c89b9 100644
--- a/test/renderer/store/extensionsSlice.test.ts
+++ b/test/renderer/store/extensionsSlice.test.ts
@@ -167,6 +167,20 @@ describe('extensionsSlice', () => {
       expect(store.getState().pluginCatalogLoading).toBe(false);
     });
 
+    it('clears stale catalog when a different project fetch fails', async () => {
+      store.setState({
+        pluginCatalog: [makePlugin({ pluginId: 'project-a@m' })],
+        pluginCatalogProjectPath: '/tmp/project-a',
+      });
+      (api.plugins!.getAll as ReturnType<typeof vi.fn>).mockRejectedValue(new Error('boom'));
+
+      await store.getState().fetchPluginCatalog('/tmp/project-b');
+
+      expect(store.getState().pluginCatalog).toEqual([]);
+      expect(store.getState().pluginCatalogProjectPath).toBe('/tmp/project-b');
+      expect(store.getState().pluginCatalogError).toBe('boom');
+    });
+
     it('dedups concurrent requests for the same project key', async () => {
       let resolveFetch!: (plugins: EnrichedPlugin[]) => void;
       const inFlight = new Promise<EnrichedPlugin[]>((resolve) => {
@@ -243,6 +257,15 @@ describe('extensionsSlice', () => {
 
       expect(api.plugins!.getReadme).not.toHaveBeenCalled();
     });
+
+    it('retries README fetch when the cached value is null', () => {
+      store.setState({ pluginReadmes: { 'test@m': null } });
+      (api.plugins!.getReadme as ReturnType<typeof vi.fn>).mockResolvedValue(null);
+
+      store.getState().fetchPluginReadme('test@m');
+
+      expect(api.plugins!.getReadme).toHaveBeenCalledWith('test@m');
+    });
   });
 
   describe('mcpBrowse', () => {