@@ -7451,6 +7451,10 @@ export default function ChatView(props: ChatViewProps) {
         return;
       }
     }
+    // Stop drains the queue. A queued send whose upload was still running at
+    // that moment must not start a turn afterwards; it checks this before
+    // dispatch and hands the message back to the composer instead.
+    const drainGenerationAtTake = useQueuedMessageStore.getState().drainGeneration;
     // A queued send that fails goes back to the head of the queue, held. The
     // messages behind it keep their order and wait; the composer is not
     // touched, which also keeps a failure after navigation off the new
@@ -7495,6 +7499,15 @@ export default function ChatView(props: ChatViewProps) {
       }
     }
 
+    if (
+      queuedMessage &&
+      useQueuedMessageStore.getState().drainGeneration !== drainGenerationAtTake
+    ) {
+      sendInFlightRef.current = false;
+      restoreQueuedMessagesToComposer([queuedMessage]);
+      return;
+    }
+
     const resolvedSubmissionIntent =
       submissionIntent === "background" && isLocalDraftThread ? "background" : "foreground";
     if (
 
@@ -23,7 +23,7 @@ function makeMessage(prompt: string): Omit<QueuedComposerMessage, "id"> {
 
 describe("queuedMessageStore", () => {
   beforeEach(() => {
-    useQueuedMessageStore.setState({ queuesByThreadKey: {} });
+    useQueuedMessageStore.setState({ queuesByThreadKey: {}, drainGeneration: 0 });
   });
 
   it("keeps messages in submission order per thread", () => {
@@ -93,7 +93,9 @@ describe("queuedMessageStore", () => {
     enqueue("thread-b", makeMessage("other"));
 
     expect(drain("thread-a").map((message) => message.prompt)).toEqual(["first", "second"]);
+    expect(useQueuedMessageStore.getState().drainGeneration).toBe(1);
     expect(drain("thread-a")).toEqual([]);
+    expect(useQueuedMessageStore.getState().drainGeneration).toBe(1);
     expect(useQueuedMessageStore.getState().queuesByThreadKey["thread-b"]).toHaveLength(1);
   });
 });
 
@@ -37,6 +37,12 @@ export interface QueuedComposerMessage {
 
 interface QueuedMessageStoreState {
   queuesByThreadKey: Record<string, QueuedComposerMessage[]>;
+  /**
+   * Bumped by `drain`. A send that took a message before a drain and finishes
+   * its upload after it compares this to the value it captured and gives up,
+   * so Stop cannot be followed by a queued message starting a new turn.
+   */
+  drainGeneration: number;
   enqueue: (threadKey: string, message: Omit<QueuedComposerMessage, "id">) => QueuedComposerMessage;
   /**
    * Removes one message and returns it, or null when another caller already
@@ -64,6 +70,7 @@ const EMPTY_QUEUE: QueuedComposerMessage[] = [];
 /** In-memory only: a queued message is a live intent, not a draft worth persisting. */
 export const useQueuedMessageStore = create<QueuedMessageStoreState>()((set, get) => ({
   queuesByThreadKey: {},
+  drainGeneration: 0,
   enqueue: (threadKey, message) => {
     const entry: QueuedComposerMessage = { ...message, id: randomUUID() };
     set((state) => ({
@@ -139,7 +146,7 @@ export const useQueuedMessageStore = create<QueuedMessageStoreState>()((set, get
     set((state) => {
       const queuesByThreadKey = { ...state.queuesByThreadKey };
       delete queuesByThreadKey[threadKey];
-      return { queuesByThreadKey };
+      return { queuesByThreadKey, drainGeneration: state.drainGeneration + 1 };
     });
     return queue;
   },