diff --git a/apps/x/VIDEO_MODE.md b/apps/x/VIDEO_MODE.md
index b9cfc673..091ef415 100644
--- a/apps/x/VIDEO_MODE.md
+++ b/apps/x/VIDEO_MODE.md
@@ -46,7 +46,10 @@ never turns the coach on.
 
 In-call controls (identical bar on both surfaces): camera toggle (silhouette
 avatar while off, no webcam frames captured), screen share toggle, mascot ⇄
-"R" letter avatar, end call. Captions of the in-progress utterance and the
+"R" letter avatar, end call. While the assistant is thinking or speaking, a
+red **Stop** button appears on the mascot tile — it silences TTS instantly,
+skips queued voice segments, and aborts the run if it's still generating
+(stopping a run from anywhere, including the composer, also silences TTS). Captions of the in-progress utterance and the
 assistant's spoken line run along the bottom. Typing in the composer still
 works mid-call; frames ride along with typed messages too.
 
diff --git a/apps/x/apps/renderer/src/App.tsx b/apps/x/apps/renderer/src/App.tsx
index 4de60e33..f0017fb3 100644
--- a/apps/x/apps/renderer/src/App.tsx
+++ b/apps/x/apps/renderer/src/App.tsx
@@ -978,6 +978,9 @@ function App() {
   // t0 = utterance accepted, submit = message sent, speak = first TTS
   // speak(). Emitted as call_turn_latency when audio actually starts.
   const callTurnMarksRef = useRef<{ t0: number; submit?: number; speak?: number } | null>(null)
+  // Late-bound handle to handleStop (defined much further down) so early
+  // call handlers can stop the run without reordering the component.
+  const stopRunRef = useRef<(() => Promise<void>) | null>(null)
   // Read-aloud style: 'summary' for typed chat, forced to 'full' during a
   // call and restored after. Context decides — the user never picks it.
   const ttsModeRef = useRef<'summary' | 'full'>('summary')
@@ -1250,6 +1253,21 @@ function App() {
     await video.startScreenShare()
   }, [video])
 
+  // Interrupt the assistant: silence TTS immediately, skip anything already
+  // queued from the in-flight turn, and stop the run if it's still
+  // generating (if it already finished, stopping the speech is all there is
+  // to do). Wired to the Stop control next to the mascot on both surfaces.
+  const handleInterruptAssistant = useCallback(() => {
+    ttsRef.current.cancel()
+    setAssistantCaption('')
+    if (voiceSegments) {
+      spokenVoiceRef.current.count = voiceSegments.length
+    }
+    if (activeIsProcessing) {
+      void stopRunRef.current?.()
+    }
+  }, [voiceSegments, activeIsProcessing])
+
   // Current phase of the call (null when not in one).
   const videoCallStatus: 'listening' | 'thinking' | 'speaking' | null =
     inCall
@@ -1317,13 +1335,14 @@ function App() {
     return window.ipc.on('video:popout-action', ({ action }) => {
       if (action === 'toggle-camera') handleToggleCamera()
       else if (action === 'toggle-share') void handleToggleScreenShare()
+      else if (action === 'stop-speaking') handleInterruptAssistant()
       else if (action === 'end-call') endCall()
       else if (action === 'expand') {
         if (video.screenState === 'live') video.stopScreenShare()
         setCallMinimized(false)
       }
     })
-  }, [handleToggleCamera, handleToggleScreenShare, endCall, video])
+  }, [handleToggleCamera, handleToggleScreenShare, handleInterruptAssistant, endCall, video])
 
   // Enter to submit voice input, Escape to cancel
   useEffect(() => {
@@ -3027,12 +3046,18 @@ function App() {
     if (!runId) return
     setStopClickedAt(Date.now())
     setIsStopping(true)
+    // Stopping the run must also silence it — the TTS queue holds segments
+    // that were already extracted from the stream and would keep playing
+    // long after the turn is aborted.
+    ttsRef.current.cancel()
+    setAssistantCaption('')
     try {
       await sessionChat.stop()
     } catch (error) {
       console.error('Failed to stop turn:', error)
     }
   }, [runId, sessionChat])
+  stopRunRef.current = handleStop
 
   const handlePermissionResponse = useCallback(async (
     toolCallId: string,
@@ -6693,6 +6718,7 @@ function App() {
                 onToggleCamera={handleToggleCamera}
                 practiceMode={practiceMode}
                 onMinimize={() => void handleMinimizeCall()}
+                onInterrupt={handleInterruptAssistant}
                 ttsState={tts.state}
                 getTtsLevel={tts.getLevel}
                 status={videoCallStatus ?? 'listening'}
diff --git a/apps/x/apps/renderer/src/components/video-call-view.tsx b/apps/x/apps/renderer/src/components/video-call-view.tsx
index 8f95ce8c..38031b68 100644
--- a/apps/x/apps/renderer/src/components/video-call-view.tsx
+++ b/apps/x/apps/renderer/src/components/video-call-view.tsx
@@ -1,5 +1,5 @@
 import { useEffect, useRef, useState } from 'react'
-import { Minimize2, MonitorUp, PhoneOff, Presentation, User, Video, VideoOff } from 'lucide-react'
+import { Minimize2, MonitorUp, PhoneOff, Presentation, Square, User, Video, VideoOff } from 'lucide-react'
 
 import { MascotFaceIcon, TalkingHead } from '@/components/talking-head'
 import type { TTSState } from '@/hooks/useVoiceTTS'
@@ -19,6 +19,8 @@ interface VideoCallViewProps {
   practiceMode?: boolean
   /** Shrink to the floating pill without touching any devices. */
   onMinimize: () => void
+  /** Stop the assistant: silence speech and abort the run if still going. */
+  onInterrupt: () => void
   ttsState: TTSState
   /** Live TTS output level — drives the mascot's mouth animation. */
   getTtsLevel: () => number
@@ -52,6 +54,7 @@ export function VideoCallView({
   onToggleScreenShare,
   practiceMode,
   onMinimize,
+  onInterrupt,
   ttsState,
   getTtsLevel,
   status,
@@ -147,6 +150,18 @@ export function VideoCallView({
           <span className="absolute bottom-3 left-3 rounded-md bg-black/50 px-2 py-0.5 text-sm text-white">
             Rowboat
           </span>
+          {status !== 'listening' && (
+            <button
+              type="button"
+              onClick={onInterrupt}
+              className="absolute bottom-3 right-3 flex items-center gap-1.5 rounded-md bg-red-600/90 px-2.5 py-1 text-sm font-medium text-white transition-colors hover:bg-red-500"
+              aria-label="Stop the assistant"
+              title={status === 'speaking' ? 'Stop speaking' : 'Stop responding'}
+            >
+              <Square className="h-3 w-3 fill-current" />
+              Stop
+            </button>
+          )}
           <button
             type="button"
             onClick={() => setMascotVisible((v) => !v)}
diff --git a/apps/x/apps/renderer/src/components/video-popout.tsx b/apps/x/apps/renderer/src/components/video-popout.tsx
index c0814798..a3c50436 100644
--- a/apps/x/apps/renderer/src/components/video-popout.tsx
+++ b/apps/x/apps/renderer/src/components/video-popout.tsx
@@ -1,5 +1,5 @@
 import { useCallback, useEffect, useRef, useState } from 'react'
-import { Maximize2, MonitorUp, PhoneOff, User, Video, VideoOff } from 'lucide-react'
+import { Maximize2, MonitorUp, PhoneOff, Square, User, Video, VideoOff } from 'lucide-react'
 
 import { TalkingHead } from '@/components/talking-head'
 
@@ -80,7 +80,7 @@ export function VideoPopout() {
   // so the mascot still animates while the assistant speaks in the main window.
   const getLevel = useCallback(() => 0.45 + 0.35 * Math.sin(performance.now() / 90), [])
 
-  const sendAction = useCallback((action: 'toggle-camera' | 'toggle-share' | 'end-call' | 'expand') => {
+  const sendAction = useCallback((action: 'toggle-camera' | 'toggle-share' | 'stop-speaking' | 'end-call' | 'expand') => {
     void window.ipc.invoke('video:popoutAction', { action }).catch(() => {})
   }, [])
 
@@ -131,6 +131,19 @@ export function VideoPopout() {
               {statusDisplay.label}
             </span>
           )}
+          {(state.status === 'speaking' || state.status === 'thinking') && (
+            <button
+              type="button"
+              onClick={() => sendAction('stop-speaking')}
+              className="absolute bottom-1 right-1.5 flex items-center gap-1 rounded bg-red-600/90 px-1.5 py-0.5 text-[10px] font-medium text-white hover:bg-red-500"
+              style={noDragRegion}
+              aria-label="Stop the assistant"
+              title={state.status === 'speaking' ? 'Stop speaking' : 'Stop responding'}
+            >
+              <Square className="h-2.5 w-2.5 fill-current" />
+              Stop
+            </button>
+          )}
         </div>
         {/* Live caption of the in-progress utterance, floating over the tiles */}
         {state.interimText && (
diff --git a/apps/x/packages/shared/src/ipc.ts b/apps/x/packages/shared/src/ipc.ts
index e54df4e8..a6784839 100644
--- a/apps/x/packages/shared/src/ipc.ts
+++ b/apps/x/packages/shared/src/ipc.ts
@@ -1451,7 +1451,7 @@ const ipcSchemas = {
   // main app window (handled in the main process).
   'video:popoutAction': {
     req: z.object({
-      action: z.enum(['toggle-camera', 'toggle-share', 'end-call', 'expand']),
+      action: z.enum(['toggle-camera', 'toggle-share', 'stop-speaking', 'end-call', 'expand']),
     }),
     res: z.object({}),
   },
@@ -1469,7 +1469,7 @@ const ipcSchemas = {
   // Push channel: main → app window with a popout control-bar action.
   'video:popout-action': {
     req: z.object({
-      action: z.enum(['toggle-camera', 'toggle-share', 'end-call', 'expand']),
+      action: z.enum(['toggle-camera', 'toggle-share', 'stop-speaking', 'end-call', 'expand']),
     }),
     res: z.null(),
   },