diff --git a/web/app/components/base/markdown-blocks/__tests__/think-block.spec.tsx b/web/app/components/base/markdown-blocks/__tests__/think-block.spec.tsx
index e8b956cbbf..4f22468157 100644
--- a/web/app/components/base/markdown-blocks/__tests__/think-block.spec.tsx
+++ b/web/app/components/base/markdown-blocks/__tests__/think-block.spec.tsx
@@ -163,25 +163,16 @@ describe('ThinkBlock', () => {
       expect(screen.getByText(/Thought/)).toBeInTheDocument()
     })
 
-    it('should NOT stop timer when isResponding is undefined (outside ChatContextProvider)', () => {
-      // Render without ChatContextProvider
+    it('should stop timer when isResponding is undefined (historical conversation outside active response)', () => {
+      // Render without ChatContextProvider — simulates historical conversation
       render(
         <ThinkBlock data-think={true}>
           <p>Content without ENDTHINKFLAG</p>
         </ThinkBlock>,
       )
 
-      // Initial state should show "Thinking..."
-      expect(screen.getByText(/Thinking\.\.\./)).toBeInTheDocument()
-
-      // Advance timer
-      act(() => {
-        vi.advanceTimersByTime(2000)
-      })
-
-      // Timer should still be running (showing "Thinking..." not "Thought")
-      expect(screen.getByText(/Thinking\.\.\./)).toBeInTheDocument()
-      expect(screen.getByText(/\(2\.0s\)/)).toBeInTheDocument()
+      // Timer should be stopped immediately — isResponding undefined means not in active response
+      expect(screen.getByText(/Thought/)).toBeInTheDocument()
     })
   })
 
diff --git a/web/app/components/base/markdown-blocks/think-block.tsx b/web/app/components/base/markdown-blocks/think-block.tsx
index f920218152..184ed89274 100644
--- a/web/app/components/base/markdown-blocks/think-block.tsx
+++ b/web/app/components/base/markdown-blocks/think-block.tsx
@@ -39,9 +39,10 @@ const removeEndThink = (children: any): any => {
 
 const useThinkTimer = (children: any) => {
   const { isResponding } = useChatContext()
+  const endThinkDetected = hasEndThink(children)
   const [startTime] = useState(() => Date.now())
   const [elapsedTime, setElapsedTime] = useState(0)
-  const [isComplete, setIsComplete] = useState(false)
+  const [isComplete, setIsComplete] = useState(() => endThinkDetected)
   const timerRef = useRef<NodeJS.Timeout | null>(null)
 
   useEffect(() => {
@@ -61,11 +62,10 @@ const useThinkTimer = (children: any) => {
   useEffect(() => {
     // Stop timer when:
     // 1. Content has [ENDTHINKFLAG] marker (normal completion)
-    // 2. isResponding is explicitly false (user clicked stop button)
-    // Note: Don't stop when isResponding is undefined (component used outside ChatContextProvider)
-    if (hasEndThink(children) || isResponding === false)
+    // 2. isResponding is not true (false = user clicked stop, undefined = historical conversation)
+    if (endThinkDetected || !isResponding)
       setIsComplete(true)
-  }, [children, isResponding])
+  }, [endThinkDetected, isResponding])
 
   return { elapsedTime, isComplete }
 }