diff --git a/apps/nextjs/src/components/assistant/assistant-notifications.spec.ts b/apps/nextjs/src/components/assistant/assistant-notifications.spec.ts
new file mode 100644
index 000000000..11ca3fd04
--- /dev/null
+++ b/apps/nextjs/src/components/assistant/assistant-notifications.spec.ts
@@ -0,0 +1,93 @@
+import { describe, expect, test } from "vitest";
+
+import { initialAssistantNotificationState, updateAssistantNotificationState } from "./assistant-notifications";
+
+describe("updateAssistantNotificationState", () => {
+  test("baselines the current response when notifications initialize", () => {
+    const update = updateAssistantNotificationState(initialAssistantNotificationState, {
+      conversationId: "conversation-a",
+      notificationKey: "response-a:complete",
+    });
+
+    expect(update.shouldNotify).toBe(false);
+    expect(update.state).toEqual({
+      initialized: true,
+      conversationId: "conversation-a",
+      notificationKey: "response-a:complete",
+    });
+  });
+
+  test("notifies when a response completes in the active conversation", () => {
+    const update = updateAssistantNotificationState(
+      {
+        initialized: true,
+        conversationId: "conversation-a",
+        notificationKey: null,
+      },
+      {
+        conversationId: "conversation-a",
+        notificationKey: "response-a:complete",
+      },
+    );
+
+    expect(update.shouldNotify).toBe(true);
+  });
+
+  test("does not count existing history when the selected conversation changes", () => {
+    const update = updateAssistantNotificationState(
+      {
+        initialized: true,
+        conversationId: "conversation-a",
+        notificationKey: "response-a:complete",
+      },
+      {
+        conversationId: "conversation-b",
+        notificationKey: "response-b:complete",
+      },
+    );
+
+    expect(update.shouldNotify).toBe(false);
+    expect(update.state.notificationKey).toBe("response-b:complete");
+  });
+
+  test("notifies for the next completion after switching conversations", () => {
+    const switched = updateAssistantNotificationState(
+      {
+        initialized: true,
+        conversationId: "conversation-a",
+        notificationKey: "response-a:complete",
+      },
+      {
+        conversationId: "conversation-b",
+        notificationKey: "response-b:complete",
+      },
+    );
+    const completed = updateAssistantNotificationState(switched.state, {
+      conversationId: "conversation-b",
+      notificationKey: "response-c:complete",
+    });
+
+    expect(completed.shouldNotify).toBe(true);
+  });
+
+  test("ignores running and repeated response states", () => {
+    const previous = {
+      initialized: true,
+      conversationId: "conversation-a",
+      notificationKey: "response-a:complete",
+    };
+
+    expect(
+      updateAssistantNotificationState(previous, {
+        conversationId: "conversation-a",
+        notificationKey: null,
+      }).shouldNotify,
+    ).toBe(false);
+    expect(
+      updateAssistantNotificationState(previous, {
+        conversationId: "conversation-a",
+        notificationKey: "response-a:complete",
+      }).shouldNotify,
+    ).toBe(false);
+  });
+});
diff --git a/apps/nextjs/src/components/assistant/assistant-notifications.ts b/apps/nextjs/src/components/assistant/assistant-notifications.ts
new file mode 100644
index 000000000..953b1581d
--- /dev/null
+++ b/apps/nextjs/src/components/assistant/assistant-notifications.ts
@@ -0,0 +1,32 @@
+export interface AssistantNotificationState {
+  initialized: boolean;
+  conversationId: string | null;
+  notificationKey: string | null;
+}
+
+export interface AssistantNotificationUpdate {
+  state: AssistantNotificationState;
+  shouldNotify: boolean;
+}
+
+export const initialAssistantNotificationState: AssistantNotificationState = {
+  initialized: false,
+  conversationId: null,
+  notificationKey: null,
+};
+
+export const updateAssistantNotificationState = (
+  previous: AssistantNotificationState,
+  current: Pick<AssistantNotificationState, "conversationId" | "notificationKey">,
+): AssistantNotificationUpdate => {
+  const state = { initialized: true, ...current };
+
+  if (!previous.initialized || previous.conversationId !== current.conversationId) {
+    return { state, shouldNotify: false };
+  }
+
+  return {
+    state,
+    shouldNotify: current.notificationKey !== null && current.notificationKey !== previous.notificationKey,
+  };
+};
diff --git a/apps/nextjs/src/components/assistant/assistant-provider.tsx b/apps/nextjs/src/components/assistant/assistant-provider.tsx
index d77362e6f..7d30b0581 100644
--- a/apps/nextjs/src/components/assistant/assistant-provider.tsx
+++ b/apps/nextjs/src/components/assistant/assistant-provider.tsx
@@ -39,6 +39,7 @@ import { createAssistantPromptInteraction } from "./assistant-spotlight";
 import { browserToolContracts } from "./assistant-tool-contracts";
 import { AssistantConfigureBoardSettingsTool } from "./assistant-board-settings-tool";
 import type { AssistantUIMessage } from "./assistant-message-metadata";
+import { initialAssistantNotificationState, updateAssistantNotificationState } from "./assistant-notifications";
 import { AssistantBoardWidget } from "./assistant-widget";
 
 interface AssistantContextValue {
@@ -478,14 +479,15 @@ const AssistantRuntime = ({ children }: PropsWithChildren) => {
 
 const AssistantPreferenceSync = () => {
   const preferences = useAssistantPreferences();
-  const threadId = useAuiState((state) => state.threadListItem.remoteId);
+  // The local id distinguishes every thread immediately, including threads that do not have a remote id yet.
+  const conversationId = useAuiState((state) => state.threadListItem.id);
   const threadModelId = useAuiState((state) => state.threadListItem.custom?.modelId);
   const previousSyncKeyRef = useRef<string | null>(null);
   const modelCatalogKey = preferences.models.map((model) => model.id).join("\0");
 
   useEffect(() => {
     if (preferences.models.length === 0) return;
-    const syncKey = `${threadId ?? "new"}:${modelCatalogKey}`;
+    const syncKey = `${conversationId}:${modelCatalogKey}`;
     if (previousSyncKeyRef.current === syncKey) return;
     previousSyncKeyRef.current = syncKey;
     const storedModelId = typeof threadModelId === "string" ? threadModelId : null;
@@ -494,7 +496,7 @@ const AssistantPreferenceSync = () => {
         ? storedModelId
         : preferences.defaultModelId;
     if (nextModelId) preferences.setModelId(nextModelId);
-  }, [modelCatalogKey, preferences, threadId, threadModelId]);
+  }, [conversationId, modelCatalogKey, preferences, threadModelId]);
 
   return null;
 };
@@ -547,13 +549,16 @@ const EnabledAssistantProvider = ({ children }: PropsWithChildren) => {
   const pendingAction = getPendingAssistantAction(latestAssistantMessage);
   const assistantIsRunning = isRunning || queuedPrompt !== null;
   const notificationKey = getNotificationKey(latestAssistantMessage);
-  const initializedRef = useRef(false);
-  const lastNotifiedKeyRef = useRef<string | null>(null);
+  const notificationStateRef = useRef(initialAssistantNotificationState);
 
   const markRead = useCallback(() => {
-    lastNotifiedKeyRef.current = notificationKey;
+    notificationStateRef.current = {
+      initialized: true,
+      conversationId,
+      notificationKey,
+    };
     setUnreadCount(0);
-  }, [notificationKey]);
+  }, [conversationId, notificationKey]);
   const open = useCallback(() => {
     markRead();
     setActivityDismissed(false);
@@ -607,25 +612,21 @@ const EnabledAssistantProvider = ({ children }: PropsWithChildren) => {
 
   useEffect(() => {
     if (isLoading) return;
-
-    if (!initializedRef.current) {
-      initializedRef.current = true;
-      lastNotifiedKeyRef.current = notificationKey;
-      return;
-    }
-
-    if (notificationKey === null || notificationKey === lastNotifiedKeyRef.current) return;
+    const update = updateAssistantNotificationState(notificationStateRef.current, {
+      conversationId,
+      notificationKey,
+    });
+    notificationStateRef.current = update.state;
+    if (!update.shouldNotify) return;
     setActivityDismissed(false);
 
     if (opened) {
-      lastNotifiedKeyRef.current = notificationKey;
       setUnreadCount(0);
       return;
     }
 
-    lastNotifiedKeyRef.current = notificationKey;
     setUnreadCount((current) => current + 1);
-  }, [isLoading, notificationKey, opened]);
+  }, [conversationId, isLoading, notificationKey, opened]);
 
   useHotkeys([[hotkeys.openAssistant, open, { preventDefault: true }]]);