diff --git a/packages/client/src/hooks/useMessageQueue.test.ts b/packages/client/src/hooks/useMessageQueue.test.ts
new file mode 100644
index 00000000..2ce21945
--- /dev/null
+++ b/packages/client/src/hooks/useMessageQueue.test.ts
@@ -0,0 +1,87 @@
+import { describe, test, expect, mock } from 'bun:test';
+import { renderHook, act } from '@testing-library/react';
+import { useMessageQueue } from './useMessageQueue';
+
+function createOptions(sendFn: (message: string) => Promise<void>) {
+  return {
+    sendFn,
+    createNewChat: mock(async () => 'chat-id'),
+    connected: true,
+    loading: false,
+    hasPendingApproval: false,
+  };
+}
+
+describe('useMessageQueue', () => {
+  test('processes a later message after an earlier send rejects', async () => {
+    const sendFn = mock((message: string) => {
+      if (message === 'fails') {
+        return Promise.reject(new Error('upload failed'));
+      }
+      return Promise.resolve();
+    });
+
+    const { result } = renderHook(() => useMessageQueue(createOptions(sendFn)));
+
+    await act(async () => {
+      await expect(result.current.sendMessage('fails')).rejects.toThrow('upload failed');
+    });
+
+    await act(async () => {
+      await result.current.sendMessage('second');
+    });
+
+    expect(sendFn).toHaveBeenCalledTimes(2);
+    expect(sendFn).toHaveBeenNthCalledWith(1, 'fails', undefined, undefined);
+    expect(sendFn).toHaveBeenNthCalledWith(2, 'second', undefined, undefined);
+  });
+
+  function queueBehindFailingSend() {
+    let rejectA: (error: Error) => void = () => {};
+    const sendFn = mock((message: string) => {
+      if (message === 'A') {
+        return new Promise<void>((_resolve, reject) => {
+          rejectA = reject;
+        });
+      }
+      return Promise.resolve();
+    });
+    const { result } = renderHook(() => useMessageQueue(createOptions(sendFn)));
+    return { sendFn, result, rejectA: (error: Error) => rejectA(error) };
+  }
+
+  test('resolves a queued caller only once its message has been sent', async () => {
+    const { result } = queueBehindFailingSend();
+
+    let bSettled = false;
+    await act(async () => {
+      result.current.sendMessage('A').catch(() => {});
+      await new Promise((resolve) => setTimeout(resolve, 0));
+      result.current.sendMessage('B').then(() => { bSettled = true; }, () => { bSettled = true; });
+      await new Promise((resolve) => setTimeout(resolve, 0));
+    });
+
+    expect(bSettled).toBe(false);
+  });
+
+  test('delivers a message queued behind a failing send', async () => {
+    const { sendFn, result, rejectA } = queueBehindFailingSend();
+
+    let sendAPromise: Promise<void> = Promise.resolve();
+    let sendBPromise: Promise<void> = Promise.resolve();
+    await act(async () => {
+      sendAPromise = result.current.sendMessage('A');
+      await new Promise((resolve) => setTimeout(resolve, 0));
+      sendBPromise = result.current.sendMessage('B');
+      await new Promise((resolve) => setTimeout(resolve, 0));
+    });
+
+    await act(async () => {
+      rejectA(new Error('upload failed'));
+      await expect(sendAPromise).rejects.toThrow('upload failed');
+      await sendBPromise;
+    });
+
+    expect(sendFn.mock.calls.map((call) => call[0])).toEqual(['A', 'B']);
+  });
+});
diff --git a/packages/client/src/hooks/useMessageQueue.ts b/packages/client/src/hooks/useMessageQueue.ts
index 087ab19a..a2aaec33 100644
--- a/packages/client/src/hooks/useMessageQueue.ts
+++ b/packages/client/src/hooks/useMessageQueue.ts
@@ -46,6 +46,13 @@ export interface UseMessageQueueReturn {
   sendMessage: (message: string, options?: SendMessageOptions) => Promise<void>;
 }
 
+interface QueuedMessage {
+  message: string;
+  options?: SendMessageOptions;
+  resolve: () => void;
+  reject: (error: unknown) => void;
+}
+
 /**
  * Hook for queuing and sending programmatic messages.
  *
@@ -64,7 +71,7 @@ export function useMessageQueue({
   loading,
   hasPendingApproval,
 }: UseMessageQueueOptions): UseMessageQueueReturn {
-  const pendingMessagesRef = useRef<Array<{ message: string; options?: SendMessageOptions }>>([]);
+  const pendingMessagesRef = useRef<QueuedMessage[]>([]);
   const isProcessingQueueRef = useRef(false);
 
   // Use refs for callbacks that may change between renders.
@@ -90,72 +97,87 @@ export function useMessageQueue({
     hasPendingApprovalRef.current = hasPendingApproval;
   }, [hasPendingApproval]);
 
-  const processMessageQueue = useCallback(async () => {
-    if (isProcessingQueueRef.current || pendingMessagesRef.current.length === 0) {
-      return;
-    }
+  const sendQueuedMessage = useCallback(async (message: string, options?: SendMessageOptions) => {
+    const { newChat = false, attachments = [], openChat = true, metadata, forwardedProps } = options ?? {};
 
-    isProcessingQueueRef.current = true;
+    if (newChat) {
+      await createNewChatRef.current({ metadata });
+    }
 
-    while (pendingMessagesRef.current.length > 0) {
-      const { message, options } = pendingMessagesRef.current.shift()!;
-      const { newChat = false, attachments = [], openChat = true, metadata, forwardedProps } = options ?? {};
+    // Convert File[] to FileAttachment[]
+    const fileAttachments: FileAttachment[] = await Promise.all(
+      attachments.map(async (file) => {
+        let preview: string | undefined;
+        if (file.type.startsWith('image/')) {
+          preview = await new Promise<string | undefined>((resolve) => {
+            const reader = new FileReader();
+            reader.onload = () => resolve(typeof reader.result === 'string' ? reader.result : undefined);
+            reader.onerror = () => resolve(undefined);
+            reader.readAsDataURL(file);
+          });
+        }
+        return {
+          id: crypto.randomUUID(),
+          file,
+          preview,
+        };
+      })
+    );
 
-      if (newChat) {
-        await createNewChatRef.current({ metadata });
-      }
+    await sendFnRef.current(message, fileAttachments.length > 0 ? fileAttachments : undefined, forwardedProps);
 
-      // Convert File[] to FileAttachment[]
-      const fileAttachments: FileAttachment[] = await Promise.all(
-        attachments.map(async (file) => {
-          let preview: string | undefined;
-          if (file.type.startsWith('image/')) {
-            preview = await new Promise<string | undefined>((resolve) => {
-              const reader = new FileReader();
-              reader.onload = () => resolve(typeof reader.result === 'string' ? reader.result : undefined);
-              reader.onerror = () => resolve(undefined);
-              reader.readAsDataURL(file);
-            });
-          }
-          return {
-            id: crypto.randomUUID(),
-            file,
-            preview,
-          };
-        })
-      );
-
-      await sendFnRef.current(message, fileAttachments.length > 0 ? fileAttachments : undefined, forwardedProps);
-
-      if (openChat && setOpenRef.current) {
-        setOpenRef.current(true);
-      }
+    if (openChat && setOpenRef.current) {
+      setOpenRef.current(true);
+    }
+  }, []);
 
-      // Wait for loading and pending approval to complete before processing next message
-      await new Promise<void>((resolve) => {
-        const checkReady = () => {
-          setTimeout(() => {
-            if (!loadingRef.current && !hasPendingApprovalRef.current) {
-              resolve();
-            } else {
-              checkReady();
-            }
-          }, 100);
-        };
-        checkReady();
-      });
+  const waitUntilIdle = useCallback(() => new Promise<void>((resolve) => {
+    const checkReady = () => {
+      setTimeout(() => {
+        if (!loadingRef.current && !hasPendingApprovalRef.current) {
+          resolve();
+        } else {
+          checkReady();
+        }
+      }, 100);
+    };
+    checkReady();
+  }), []);
+
+  // Each queued message settles its own caller's promise, so one failing send
+  // neither blocks nor discards the messages queued behind it.
+  const processMessageQueue = useCallback(async () => {
+    if (isProcessingQueueRef.current) {
+      return;
     }
 
-    isProcessingQueueRef.current = false;
-  }, []);
+    isProcessingQueueRef.current = true;
+    try {
+      while (pendingMessagesRef.current.length > 0) {
+        const entry = pendingMessagesRef.current.shift()!;
+        try {
+          await sendQueuedMessage(entry.message, entry.options);
+        } catch (error) {
+          entry.reject(error);
+          continue;
+        }
+        entry.resolve();
+        await waitUntilIdle();
+      }
+    } finally {
+      isProcessingQueueRef.current = false;
+    }
+  }, [sendQueuedMessage, waitUntilIdle]);
 
-  const sendMessage = useCallback(async (message: string, options?: SendMessageOptions): Promise<void> => {
+  const sendMessage = useCallback((message: string, options?: SendMessageOptions): Promise<void> => {
     if (!connected) {
-      throw new Error('Not connected to UseAI server');
+      return Promise.reject(new Error('Not connected to UseAI server'));
     }
 
-    pendingMessagesRef.current.push({ message, options });
-    await processMessageQueue();
+    return new Promise<void>((resolve, reject) => {
+      pendingMessagesRef.current.push({ message, options, resolve, reject });
+      void processMessageQueue();
+    });
   }, [connected, processMessageQueue]);
 
   return { sendMessage };