diff --git a/packages/vscode-ide-companion/src/webview/hooks/message/useMessageHandling.test.tsx b/packages/vscode-ide-companion/src/webview/hooks/message/useMessageHandling.test.tsx
new file mode 100644
index 000000000..3c805b4fb
--- /dev/null
+++ b/packages/vscode-ide-companion/src/webview/hooks/message/useMessageHandling.test.tsx
@@ -0,0 +1,97 @@
+/**
+ * @license
+ * Copyright 2025 Qwen Team
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+/** @vitest-environment jsdom */
+
+import { act } from 'react';
+import { createRoot, type Root } from 'react-dom/client';
+import { afterEach, beforeEach, describe, expect, it } from 'vitest';
+import { useMessageHandling, type TextMessage } from './useMessageHandling.js';
+
+type MessageHandlingApi = ReturnType<typeof useMessageHandling>;
+
+function renderHookHarness() {
+  const container = document.createElement('div');
+  document.body.appendChild(container);
+  const root = createRoot(container);
+
+  let latestApi: MessageHandlingApi | null = null;
+
+  function Harness() {
+    latestApi = useMessageHandling();
+    return null;
+  }
+
+  act(() => {
+    root.render(<Harness />);
+  });
+
+  return {
+    container,
+    root,
+    get api(): MessageHandlingApi {
+      if (!latestApi) {
+        throw new Error('Hook API is not available');
+      }
+      return latestApi;
+    },
+  };
+}
+
+describe('useMessageHandling', () => {
+  let root: Root | null = null;
+  let container: HTMLDivElement | null = null;
+
+  beforeEach(() => {
+    (
+      globalThis as typeof globalThis & { IS_REACT_ACT_ENVIRONMENT?: boolean }
+    ).IS_REACT_ACT_ENVIRONMENT = true;
+  });
+
+  afterEach(() => {
+    if (root) {
+      act(() => {
+        root?.unmount();
+      });
+      root = null;
+    }
+    if (container) {
+      container.remove();
+      container = null;
+    }
+  });
+
+  it('keeps the original stream timestamp when a tool call splits one assistant reply into multiple segments', () => {
+    const rendered = renderHookHarness();
+    root = rendered.root;
+    container = rendered.container;
+
+    act(() => {
+      rendered.api.startStreaming(1_000);
+    });
+
+    act(() => {
+      rendered.api.appendStreamChunk('before tool call');
+    });
+
+    act(() => {
+      rendered.api.breakAssistantSegment();
+    });
+
+    act(() => {
+      rendered.api.appendStreamChunk('after tool call');
+    });
+
+    const assistantMessages = rendered.api.messages.filter(
+      (message): message is TextMessage => message.role === 'assistant',
+    );
+
+    expect(assistantMessages).toHaveLength(2);
+    expect(assistantMessages.map((message) => message.timestamp)).toEqual([
+      1_000, 1_000,
+    ]);
+  });
+});
diff --git a/packages/vscode-ide-companion/src/webview/hooks/message/useMessageHandling.ts b/packages/vscode-ide-companion/src/webview/hooks/message/useMessageHandling.ts
index ff6af0125..0ac2726ba 100644
--- a/packages/vscode-ide-companion/src/webview/hooks/message/useMessageHandling.ts
+++ b/packages/vscode-ide-companion/src/webview/hooks/message/useMessageHandling.ts
@@ -35,6 +35,8 @@ export const useMessageHandling = () => {
   const streamingMessageIndexRef = useRef<number | null>(null);
   // Track the index of the current aggregated thinking message
   const thinkingMessageIndexRef = useRef<number | null>(null);
+  // Preserve one stable timestamp for all message segments in the same turn.
+  const currentStreamTimestampRef = useRef<number | null>(null);
 
   /**
    * Add message
@@ -54,6 +56,9 @@ export const useMessageHandling = () => {
    * Start streaming response
    */
   const startStreaming = useCallback((timestamp?: number) => {
+    const resolvedTimestamp =
+      typeof timestamp === 'number' ? timestamp : Date.now();
+    currentStreamTimestampRef.current = resolvedTimestamp;
     // Create an assistant placeholder message immediately so tool calls won't jump before it
     setMessages((prev) => {
       // Record index of the placeholder to update on chunks
@@ -63,8 +68,8 @@ export const useMessageHandling = () => {
         {
           role: 'assistant',
           content: '',
-          // Use provided timestamp (from extension) to keep ordering stable
-          timestamp: typeof timestamp === 'number' ? timestamp : Date.now(),
+          // Use one stable turn timestamp so later split segments sort correctly.
+          timestamp: resolvedTimestamp,
         },
       ];
     });
@@ -89,7 +94,11 @@ export const useMessageHandling = () => {
         if (idx === null) {
           idx = next.length;
           streamingMessageIndexRef.current = idx;
-          next.push({ role: 'assistant', content: '', timestamp: Date.now() });
+          next.push({
+            role: 'assistant',
+            content: '',
+            timestamp: currentStreamTimestampRef.current ?? Date.now(),
+          });
         }
 
         if (idx < 0 || idx >= next.length) {
@@ -122,6 +131,7 @@ export const useMessageHandling = () => {
     setIsStreaming(false);
     streamingMessageIndexRef.current = null;
     thinkingMessageIndexRef.current = null;
+    currentStreamTimestampRef.current = null;
   }, []);
 
   /**
@@ -173,7 +183,7 @@ export const useMessageHandling = () => {
             assistantIdx >= 0 &&
             assistantIdx < next.length
               ? next[assistantIdx].timestamp
-              : Date.now();
+              : (currentStreamTimestampRef.current ?? Date.now());
           next.push({
             role: 'thinking',
             content: '',