diff --git a/ui/src/ui/app.test.ts b/ui/src/ui/app.test.ts
index 6a4007b2850..72a57758f5d 100644
--- a/ui/src/ui/app.test.ts
+++ b/ui/src/ui/app.test.ts
@@ -136,13 +136,10 @@ describe("OpenClawApp dictation recorder lifecycle", () => {
     await app.toggleChatDictation();
     const recorder = MockMediaRecorder.instances[0];
     recorder.emitData(new Blob(["audio"], { type: "audio/webm" }));
-    transcribeChatAudioMock.mockImplementationOnce(async () => {
-      expect(app.chatDictationChunks).toEqual([]);
-      return null;
-    });
+    const transcription = createDeferred<null>();
+    transcribeChatAudioMock.mockReturnValueOnce(transcription.promise);
 
     await app.toggleChatDictation();
-    await Promise.resolve();
 
     expect(app.chatDictationChunks).toEqual([]);
     expect(transcribeChatAudioMock).toHaveBeenCalledTimes(1);
@@ -150,6 +147,8 @@ describe("OpenClawApp dictation recorder lifecycle", () => {
       size: 5,
       type: "audio/webm",
     });
+    transcription.resolve(null);
+    await transcription.promise;
   });
 
   it("ignores duplicate starts while microphone permission is pending", async () => {
diff --git a/ui/src/ui/app.ts b/ui/src/ui/app.ts
index 83d25dfba6e..50da8be7577 100644
--- a/ui/src/ui/app.ts
+++ b/ui/src/ui/app.ts
@@ -1015,8 +1015,7 @@ export class OpenClawApp extends LitElement {
         if (this.chatDictationRecorder !== recorder) {
           return;
         }
-        const chunks = [...this.chatDictationChunks];
-        this.chatDictationChunks = [];
+        const chunks = this.chatDictationChunks.splice(0);
         const canceledByRequest = this.chatDictationCancelNextStop;
         this.chatDictationCancelNextStop = false;
         this.chatDictationRecorder = null;