Merge branch 'dev' into feat/retain-interruption-message

# Conflicts:
#	web-app/src/containers/ChatInput.tsx
#	web-app/src/hooks/useChat.ts

core/src/types/message/messageInterface.ts

@@ -20,6 +20,13 @@ export interface MessageInterface {
    */
   listMessages(threadId: string): Promise<ThreadMessage[]>
 
+  /**
+   * Updates an existing message in a thread.
+   * @param {ThreadMessage} message - The message to be updated (must have existing ID).
+   * @returns {Promise<ThreadMessage>} A promise that resolves to the updated message.
+   */
+  modifyMessage(message: ThreadMessage): Promise<ThreadMessage>
+
   /**
    * Deletes a specific message from a thread.
    * @param {string} threadId - The ID of the thread from which the message will be deleted.

web-app/src/containers/ChatInput.tsx

@@ -176,7 +176,6 @@ const ChatInput = ({
   const mcpExtension = extensionManager.get<MCPExtension>(ExtensionTypeEnum.MCP)
   const MCPToolComponent = mcpExtension?.getToolComponent?.()
 
-
   const handleSendMesage = async (prompt: string) => {
     if (!selectedModel) {
       setMessage('Please select a model to start chatting.')

web-app/src/containers/GenerateResponseButton.tsx

@@ -3,6 +3,8 @@ import { useMessages } from '@/hooks/useMessages'
 import { useTranslation } from '@/i18n/react-i18next-compat'
 import { Play } from 'lucide-react'
 import { useShallow } from 'zustand/react/shallow'
+import { useMemo } from 'react'
+import { MessageStatus } from '@janhq/core'
 
 export const GenerateResponseButton = ({ threadId }: { threadId: string }) => {
   const { t } = useTranslation()
@@ -13,7 +15,36 @@ export const GenerateResponseButton = ({ threadId }: { threadId: string }) => {
     }))
   )
   const sendMessage = useChat()
+
+  // Detect if last message is a partial assistant response (user stopped midway)
+  const isPartialResponse = useMemo(() => {
+    if (!messages || messages.length < 2) return false
+    const lastMessage = messages[messages.length - 1]
+    const secondLastMessage = messages[messages.length - 2]
+
+    return (
+      lastMessage?.role === 'assistant' &&
+      lastMessage?.status === MessageStatus.Stopped &&
+      secondLastMessage?.role === 'user' &&
+      !lastMessage?.metadata?.tool_calls
+    )
+  }, [messages])
+
   const generateAIResponse = () => {
+    if (isPartialResponse) {
+      const partialMessage = messages[messages.length - 1]
+      const userMessage = messages[messages.length - 2]
+      if (userMessage?.content?.[0]?.text?.value) {
+        sendMessage(
+          userMessage.content[0].text.value,
+          false,
+          undefined,
+          partialMessage.id
+        )
+      }
+      return
+    }
+
     const latestUserMessage = messages[messages.length - 1]
     if (
       latestUserMessage?.content?.[0]?.text?.value &&
@@ -39,7 +70,11 @@ export const GenerateResponseButton = ({ threadId }: { threadId: string }) => {
       className="mx-2 bg-main-view-fg/10 px-2 border border-main-view-fg/5 flex items-center justify-center rounded-xl gap-x-2 cursor-pointer pointer-events-auto"
       onClick={generateAIResponse}
     >
-      <p className="text-xs">{t('common:generateAiResponse')}</p>
+      <p className="text-xs">
+        {isPartialResponse
+          ? t('common:continueAiResponse')
+          : t('common:generateAiResponse')}
+      </p>
       <Play size={12} />
     </div>
   )

web-app/src/containers/ScrollToBottom.tsx

@@ -8,6 +8,7 @@ import { cn } from '@/lib/utils'
 import { ArrowDown } from 'lucide-react'
 import { useTranslation } from '@/i18n/react-i18next-compat'
 import { useAppState } from '@/hooks/useAppState'
+import { MessageStatus } from '@janhq/core'
 
 const ScrollToBottom = ({
   threadId,
@@ -28,11 +29,20 @@ const ScrollToBottom = ({
 
   const streamingContent = useAppState((state) => state.streamingContent)
 
+  // Check if last message is a partial assistant response and show continue buton (user interrupted)
+  const isPartialResponse =
+    messages.length >= 2 &&
+    messages[messages.length - 1]?.role === 'assistant' &&
+    messages[messages.length - 1]?.status === MessageStatus.Stopped &&
+    messages[messages.length - 2]?.role === 'user' &&
+    !messages[messages.length - 1]?.metadata?.tool_calls
+
   const showGenerateAIResponseBtn =
-    (messages[messages.length - 1]?.role === 'user' ||
+    ((messages[messages.length - 1]?.role === 'user' ||
       (messages[messages.length - 1]?.metadata &&
-        'tool_calls' in (messages[messages.length - 1].metadata ?? {}))) &&
-    !streamingContent
+        'tool_calls' in (messages[messages.length - 1].metadata ?? {})) ||
+      isPartialResponse) &&
+    !streamingContent)
 
   return (
     <div

web-app/src/containers/StreamingContent.tsx

@@ -2,6 +2,7 @@ import { useAppState } from '@/hooks/useAppState'
 import { ThreadContent } from './ThreadContent'
 import { memo, useMemo } from 'react'
 import { useMessages } from '@/hooks/useMessages'
+import { MessageStatus } from '@janhq/core'
 
 type Props = {
   threadId: string
@@ -48,12 +49,19 @@ export const StreamingContent = memo(({ threadId }: Props) => {
     return extractReasoningSegment(text)
   }, [lastAssistant])
 
-  if (!streamingContent || streamingContent.thread_id !== threadId) return null
+  if (!streamingContent || streamingContent.thread_id !== threadId) {
+    return null
+  }
 
   if (streamingReasoning && streamingReasoning === lastAssistantReasoning) {
     return null
   }
 
+  // Don't show streaming content if there's already a stopped message
+  if (lastAssistant?.status === MessageStatus.Stopped) {
+    return null
+  }
+
   // Pass a new object to ThreadContent to avoid reference issues
   // The streaming content is always the last message
   return (

web-app/src/hooks/__tests__/useChat.test.ts

@@ -1,6 +1,30 @@
-import { renderHook, act } from '@testing-library/react'
-import { describe, it, expect, vi, beforeEach } from 'vitest'
-import { useChat } from '../useChat'
+import { renderHook, act, waitFor } from '@testing-library/react'
+import { describe, it, expect, vi, beforeEach, afterEach } from 'vitest'
+import { MessageStatus, ContentType } from '@janhq/core'
+
+// Store mock functions for assertions - initialize immediately
+const mockAddMessage = vi.fn()
+const mockUpdateMessage = vi.fn()
+const mockGetMessages = vi.fn(() => [])
+const mockStartModel = vi.fn(() => Promise.resolve())
+const mockSendCompletion = vi.fn(() => Promise.resolve({
+  choices: [{
+    message: {
+      content: 'AI response',
+      role: 'assistant',
+    },
+  }],
+}))
+const mockPostMessageProcessing = vi.fn((toolCalls, builder, content) =>
+  Promise.resolve(content)
+)
+const mockCompletionMessagesBuilder = {
+  addUserMessage: vi.fn(),
+  addAssistantMessage: vi.fn(),
+  getMessages: vi.fn(() => []),
+}
+const mockSetPrompt = vi.fn()
+const mockResetTokenSpeed = vi.fn()
 
 // Mock dependencies
 vi.mock('../usePrompt', () => ({
@@ -8,11 +32,16 @@ vi.mock('../usePrompt', () => ({
     (selector: any) => {
       const state = {
         prompt: 'test prompt',
-        setPrompt: vi.fn(),
+        setPrompt: mockSetPrompt,
       }
       return selector ? selector(state) : state
     },
-    { getState: () => ({ prompt: 'test prompt', setPrompt: vi.fn() }) }
+    {
+      getState: () => ({
+        prompt: 'test prompt',
+        setPrompt: mockSetPrompt
+      })
+    }
   ),
 }))
 
@@ -22,39 +51,58 @@ vi.mock('../useAppState', () => ({
       const state = {
         tools: [],
         updateTokenSpeed: vi.fn(),
-        resetTokenSpeed: vi.fn(),
+        resetTokenSpeed: mockResetTokenSpeed,
         updateTools: vi.fn(),
         updateStreamingContent: vi.fn(),
         updatePromptProgress: vi.fn(),
         updateLoadingModel: vi.fn(),
         setAbortController: vi.fn(),
+        streamingContent: undefined,
       }
       return selector ? selector(state) : state
     },
     {
       getState: vi.fn(() => ({
+        tools: [],
         tokenSpeed: { tokensPerSecond: 10 },
+        streamingContent: undefined,
       }))
     }
   ),
 }))
 
 vi.mock('../useAssistant', () => ({
-  useAssistant: (selector: any) => {
-    const state = {
-      assistants: [{
-        id: 'test-assistant',
-        instructions: 'test instructions',
-        parameters: { stream: true },
-      }],
-      currentAssistant: {
-        id: 'test-assistant',
-        instructions: 'test instructions',
-        parameters: { stream: true },
-      },
+  useAssistant: Object.assign(
+    (selector: any) => {
+      const state = {
+        assistants: [{
+          id: 'test-assistant',
+          instructions: 'test instructions',
+          parameters: { stream: true },
+        }],
+        currentAssistant: {
+          id: 'test-assistant',
+          instructions: 'test instructions',
+          parameters: { stream: true },
+        },
+      }
+      return selector ? selector(state) : state
+    },
+    {
+      getState: () => ({
+        assistants: [{
+          id: 'test-assistant',
+          instructions: 'test instructions',
+          parameters: { stream: true },
+        }],
+        currentAssistant: {
+          id: 'test-assistant',
+          instructions: 'test instructions',
+          parameters: { stream: true },
+        },
+      })
     }
-    return selector ? selector(state) : state
-  },
+  ),
 }))
 
 vi.mock('../useModelProvider', () => ({
@@ -62,14 +110,15 @@ vi.mock('../useModelProvider', () => ({
     (selector: any) => {
       const state = {
         getProviderByName: vi.fn(() => ({
-          provider: 'openai',
+          provider: 'llamacpp',
           models: [],
+          settings: [],
         })),
         selectedModel: {
           id: 'test-model',
           capabilities: ['tools'],
         },
-        selectedProvider: 'openai',
+        selectedProvider: 'llamacpp',
         updateProvider: vi.fn(),
       }
       return selector ? selector(state) : state
@@ -77,14 +126,15 @@ vi.mock('../useModelProvider', () => ({
     {
       getState: () => ({
         getProviderByName: vi.fn(() => ({
-          provider: 'openai',
+          provider: 'llamacpp',
           models: [],
+          settings: [],
         })),
         selectedModel: {
           id: 'test-model',
           capabilities: ['tools'],
         },
-        selectedProvider: 'openai',
+        selectedProvider: 'llamacpp',
         updateProvider: vi.fn(),
       })
     }
@@ -96,11 +146,11 @@ vi.mock('../useThreads', () => ({
     const state = {
       getCurrentThread: vi.fn(() => ({
         id: 'test-thread',
-        model: { id: 'test-model', provider: 'openai' },
+        model: { id: 'test-model', provider: 'llamacpp' },
       })),
       createThread: vi.fn(() => Promise.resolve({
         id: 'test-thread',
-        model: { id: 'test-model', provider: 'openai' },
+        model: { id: 'test-model', provider: 'llamacpp' },
       })),
       updateThreadTimestamp: vi.fn(),
     }
@@ -111,22 +161,33 @@ vi.mock('../useThreads', () => ({
 vi.mock('../useMessages', () => ({
   useMessages: (selector: any) => {
     const state = {
-      getMessages: vi.fn(() => []),
-      addMessage: vi.fn(),
+      getMessages: mockGetMessages,
+      addMessage: mockAddMessage,
+      updateMessage: mockUpdateMessage,
+      setMessages: vi.fn(),
     }
     return selector ? selector(state) : state
   },
 }))
 
 vi.mock('../useToolApproval', () => ({
-  useToolApproval: (selector: any) => {
-    const state = {
-      approvedTools: [],
-      showApprovalModal: vi.fn(),
-      allowAllMCPPermissions: false,
+  useToolApproval: Object.assign(
+    (selector: any) => {
+      const state = {
+        approvedTools: [],
+        showApprovalModal: vi.fn(),
+        allowAllMCPPermissions: false,
+      }
+      return selector ? selector(state) : state
+    },
+    {
+      getState: () => ({
+        approvedTools: [],
+        showApprovalModal: vi.fn(),
+        allowAllMCPPermissions: false,
+      })
     }
-    return selector ? selector(state) : state
-  },
+  ),
 }))
 
 vi.mock('../useToolAvailable', () => ({
@@ -162,38 +223,57 @@ vi.mock('@tanstack/react-router', () => ({
   })),
 }))
 
+vi.mock('../useServiceHub', () => ({
+  useServiceHub: vi.fn(() => ({
+    models: () => ({
+      startModel: mockStartModel,
+      stopModel: vi.fn(() => Promise.resolve()),
+      stopAllModels: vi.fn(() => Promise.resolve()),
+    }),
+    providers: () => ({
+      updateSettings: vi.fn(() => Promise.resolve()),
+    }),
+  })),
+}))
+
 vi.mock('@/lib/completion', () => ({
   emptyThreadContent: { thread_id: 'test-thread', content: '' },
   extractToolCall: vi.fn(),
-  newUserThreadContent: vi.fn(() => ({ thread_id: 'test-thread', content: 'user message' })),
-  newAssistantThreadContent: vi.fn(() => ({ thread_id: 'test-thread', content: 'assistant message' })),
-  sendCompletion: vi.fn(),
-  postMessageProcessing: vi.fn(),
-  isCompletionResponse: vi.fn(),
+  newUserThreadContent: vi.fn((threadId, content) => ({
+    thread_id: threadId,
+    content: [{ type: 'text', text: { value: content, annotations: [] } }],
+    role: 'user'
+  })),
+  newAssistantThreadContent: vi.fn((threadId, content) => ({
+    thread_id: threadId,
+    content: [{ type: 'text', text: { value: content, annotations: [] } }],
+    role: 'assistant'
+  })),
+  sendCompletion: mockSendCompletion,
+  postMessageProcessing: mockPostMessageProcessing,
+  isCompletionResponse: vi.fn(() => true),
 }))
 
 vi.mock('@/lib/messages', () => ({
-  CompletionMessagesBuilder: vi.fn(() => ({
-    addUserMessage: vi.fn(),
-    addAssistantMessage: vi.fn(),
-    getMessages: vi.fn(() => []),
+  CompletionMessagesBuilder: vi.fn(() => mockCompletionMessagesBuilder),
+}))
+
+vi.mock('@/lib/instructionTemplate', () => ({
+  renderInstructions: vi.fn((instructions: string) => instructions),
+}))
+
+vi.mock('@/utils/reasoning', () => ({
+  ReasoningProcessor: vi.fn(() => ({
+    processReasoningChunk: vi.fn(() => null),
+    finalize: vi.fn(() => ''),
   })),
+  extractReasoningFromMessage: vi.fn(() => null),
 }))
 
 vi.mock('@/services/mcp', () => ({
   getTools: vi.fn(() => Promise.resolve([])),
 }))
 
-vi.mock('@/services/models', () => ({
-  startModel: vi.fn(() => Promise.resolve()),
-  stopModel: vi.fn(() => Promise.resolve()),
-  stopAllModels: vi.fn(() => Promise.resolve()),
-}))
-
-vi.mock('@/services/providers', () => ({
-  updateSettings: vi.fn(() => Promise.resolve()),
-}))
-
 vi.mock('@tauri-apps/api/event', () => ({
   listen: vi.fn(() => Promise.resolve(vi.fn())),
 }))
@@ -204,9 +284,41 @@ vi.mock('sonner', () => ({
   },
 }))
 
+// Import after mocks to avoid hoisting issues
+const { useChat } = await import('../useChat')
+const completionLib = await import('@/lib/completion')
+const messagesLib = await import('@/lib/messages')
+
 describe('useChat', () => {
   beforeEach(() => {
+    // Clear mock call history
     vi.clearAllMocks()
+
+    // Reset mock implementations
+    mockAddMessage.mockClear()
+    mockUpdateMessage.mockClear()
+    mockGetMessages.mockReturnValue([])
+    mockStartModel.mockResolvedValue(undefined)
+    mockSetPrompt.mockClear()
+    mockResetTokenSpeed.mockClear()
+    mockSendCompletion.mockResolvedValue({
+      choices: [{
+        message: {
+          content: 'AI response',
+          role: 'assistant',
+        },
+      }],
+    })
+    mockPostMessageProcessing.mockImplementation((toolCalls, builder, content) =>
+      Promise.resolve(content)
+    )
+    mockCompletionMessagesBuilder.addUserMessage.mockClear()
+    mockCompletionMessagesBuilder.addAssistantMessage.mockClear()
+    mockCompletionMessagesBuilder.getMessages.mockReturnValue([])
+  })
+
+  afterEach(() => {
+    vi.clearAllTimers()
   })
 
   it('returns sendMessage function', () => {
@@ -216,13 +328,270 @@ describe('useChat', () => {
     expect(typeof result.current).toBe('function')
   })
 
-  it('sends message successfully', async () => {
-    const { result } = renderHook(() => useChat())
+  describe('Continue with AI response functionality', () => {
+    it('should add new user message when troubleshooting is true and no continueFromMessageId', async () => {
+      const { result } = renderHook(() => useChat())
 
-    await act(async () => {
-      await result.current('Hello world')
+      await act(async () => {
+        await result.current('Hello world', true, undefined, undefined, undefined)
+      })
+
+      expect(completionLib.newUserThreadContent).toHaveBeenCalledWith(
+        'test-thread',
+        'Hello world',
+        undefined
+      )
+      expect(mockAddMessage).toHaveBeenCalledWith(
+        expect.objectContaining({
+          thread_id: 'test-thread',
+          role: 'user',
+        })
+      )
+      expect(mockCompletionMessagesBuilder.addUserMessage).toHaveBeenCalledWith(
+        'Hello world',
+        undefined
+      )
     })
 
-    expect(result.current).toBeDefined()
+    it('should NOT add new user message when continueFromMessageId is provided', async () => {
+      const stoppedMessage = {
+        id: 'msg-123',
+        thread_id: 'test-thread',
+        role: 'assistant',
+        content: [{ type: 'text', text: { value: 'Partial response', annotations: [] } }],
+        status: MessageStatus.Stopped,
+        metadata: {},
+      }
+      mockGetMessages.mockReturnValue([stoppedMessage])
+
+      const { result } = renderHook(() => useChat())
+
+      await act(async () => {
+        await result.current('', true, undefined, undefined, 'msg-123')
+      })
+
+      expect(completionLib.newUserThreadContent).not.toHaveBeenCalled()
+      const userMessageCalls = mockAddMessage.mock.calls.filter(
+        (call: any) => call[0]?.role === 'user'
+      )
+      expect(userMessageCalls).toHaveLength(0)
+      expect(mockCompletionMessagesBuilder.addUserMessage).not.toHaveBeenCalled()
+    })
+
+    it('should add partial assistant message to builder when continuing', async () => {
+      const stoppedMessage = {
+        id: 'msg-123',
+        thread_id: 'test-thread',
+        role: 'assistant',
+        content: [{ type: 'text', text: { value: 'Partial response', annotations: [] } }],
+        status: MessageStatus.Stopped,
+        metadata: {},
+      }
+      mockGetMessages.mockReturnValue([stoppedMessage])
+
+      const { result } = renderHook(() => useChat())
+
+      await act(async () => {
+        await result.current('', true, undefined, undefined, 'msg-123')
+      })
+
+      // Should be called twice: once with partial message (line 517-521), once after completion (line 689)
+      const assistantCalls = mockCompletionMessagesBuilder.addAssistantMessage.mock.calls
+      expect(assistantCalls.length).toBeGreaterThanOrEqual(1)
+      // First call should be with the partial response content
+      expect(assistantCalls[0]).toEqual([
+        'Partial response',
+        undefined,
+        []
+      ])
+    })
+
+    it('should filter out stopped message from context when continuing', async () => {
+      const userMsg = {
+        id: 'msg-1',
+        thread_id: 'test-thread',
+        role: 'user',
+        content: [{ type: 'text', text: { value: 'Hello', annotations: [] } }],
+      }
+      const stoppedMessage = {
+        id: 'msg-123',
+        thread_id: 'test-thread',
+        role: 'assistant',
+        content: [{ type: 'text', text: { value: 'Partial', annotations: [] } }],
+        status: MessageStatus.Stopped,
+      }
+      mockGetMessages.mockReturnValue([userMsg, stoppedMessage])
+
+      const { result } = renderHook(() => useChat())
+
+      await act(async () => {
+        await result.current('', true, undefined, undefined, 'msg-123')
+      })
+
+      // The CompletionMessagesBuilder is called with filtered messages (line 507-512)
+      // The stopped message should be filtered out from the context
+      expect(messagesLib.CompletionMessagesBuilder).toHaveBeenCalled()
+      const builderCall = (messagesLib.CompletionMessagesBuilder as any).mock.calls[0]
+      expect(builderCall[0]).toEqual([userMsg]) // stopped message filtered out
+      expect(builderCall[1]).toEqual('test instructions')
+    })
+
+    it('should update existing message instead of adding new one when continuing', async () => {
+      const stoppedMessage = {
+        id: 'msg-123',
+        thread_id: 'test-thread',
+        role: 'assistant',
+        content: [{ type: 'text', text: { value: 'Partial', annotations: [] } }],
+        status: MessageStatus.Stopped,
+        metadata: {},
+      }
+      mockGetMessages.mockReturnValue([stoppedMessage])
+
+      const { result } = renderHook(() => useChat())
+
+      await act(async () => {
+        await result.current('', true, undefined, undefined, 'msg-123')
+      })
+
+      // finalizeMessage is called at line 700-708, which should update the message
+      expect(mockUpdateMessage).toHaveBeenCalledWith(
+        expect.objectContaining({
+          id: 'msg-123',
+          status: MessageStatus.Ready,
+        })
+      )
+    })
+
+    it('should start with previous content when continuing', async () => {
+      const stoppedMessage = {
+        id: 'msg-123',
+        thread_id: 'test-thread',
+        role: 'assistant',
+        content: [{ type: 'text', text: { value: 'Partial response', annotations: [] } }],
+        status: MessageStatus.Stopped,
+        metadata: {},
+      }
+      mockGetMessages.mockReturnValue([stoppedMessage])
+
+      mockSendCompletion.mockResolvedValue({
+        choices: [{
+          message: {
+            content: ' continued',
+            role: 'assistant',
+          },
+        }],
+      })
+
+      const { result } = renderHook(() => useChat())
+
+      await act(async () => {
+        await result.current('', true, undefined, undefined, 'msg-123')
+      })
+
+      // The accumulated text should contain the previous content plus new content
+      // accumulatedTextRef starts with 'Partial response' (line 490)
+      // Then gets ' continued' appended (line 585)
+      expect(mockUpdateMessage).toHaveBeenCalledWith(
+        expect.objectContaining({
+          id: 'msg-123',
+          content: expect.arrayContaining([
+            expect.objectContaining({
+              text: expect.objectContaining({
+                value: 'Partial response continued',
+              })
+            })
+          ])
+        })
+      )
+    })
+
+    it('should handle attachments correctly when not continuing', async () => {
+      const { result } = renderHook(() => useChat())
+      const attachments = [
+        {
+          name: 'test.png',
+          type: 'image/png',
+          size: 1024,
+          base64: 'base64data',
+          dataUrl: 'data:image/png;base64,base64data',
+        },
+      ]
+
+      await act(async () => {
+        await result.current('Message with attachment', true, attachments, undefined, undefined)
+      })
+
+      expect(completionLib.newUserThreadContent).toHaveBeenCalledWith(
+        'test-thread',
+        'Message with attachment',
+        attachments
+      )
+      expect(mockCompletionMessagesBuilder.addUserMessage).toHaveBeenCalledWith(
+        'Message with attachment',
+        attachments
+      )
+    })
+
+    it('should preserve message status as Ready after continuation completes', async () => {
+      const stoppedMessage = {
+        id: 'msg-123',
+        thread_id: 'test-thread',
+        role: 'assistant',
+        content: [{ type: 'text', text: { value: 'Partial', annotations: [] } }],
+        status: MessageStatus.Stopped,
+        metadata: {},
+      }
+      mockGetMessages.mockReturnValue([stoppedMessage])
+
+      const { result } = renderHook(() => useChat())
+
+      await act(async () => {
+        await result.current('', true, undefined, undefined, 'msg-123')
+      })
+
+      // finalContent is created at line 678-683 with status Ready when continuing
+      expect(mockUpdateMessage).toHaveBeenCalledWith(
+        expect.objectContaining({
+          id: 'msg-123',
+          status: MessageStatus.Ready,
+        })
+      )
+    })
+  })
+
+  describe('Normal message sending', () => {
+    it('sends message successfully without continuation', async () => {
+      const { result } = renderHook(() => useChat())
+
+      await act(async () => {
+        await result.current('Hello world')
+      })
+
+      expect(mockSendCompletion).toHaveBeenCalled()
+      expect(mockStartModel).toHaveBeenCalled()
+    })
+  })
+
+  describe('Error handling', () => {
+    it('should handle errors gracefully during continuation', async () => {
+      mockSendCompletion.mockRejectedValueOnce(new Error('API Error'))
+      const stoppedMessage = {
+        id: 'msg-123',
+        thread_id: 'test-thread',
+        role: 'assistant',
+        content: [{ type: 'text', text: { value: 'Partial', annotations: [] } }],
+        status: MessageStatus.Stopped,
+        metadata: {},
+      }
+      mockGetMessages.mockReturnValue([stoppedMessage])
+
+      const { result } = renderHook(() => useChat())
+
+      await act(async () => {
+        await result.current('', true, undefined, undefined, 'msg-123')
+      })
+
+      expect(result.current).toBeDefined()
+    })
   })
 })

web-app/src/hooks/__tests__/useMessages.test.ts

@@ -225,9 +225,25 @@ describe('useMessages', () => {
         })
       )
 
-      // Wait for async operation
+      // Message should be immediately available (optimistic update)
+      expect(result.current.messages['thread1']).toContainEqual(
+        expect.objectContaining({
+          id: messageToAdd.id,
+          thread_id: messageToAdd.thread_id,
+          role: messageToAdd.role,
+          content: messageToAdd.content,
+          metadata: expect.objectContaining({
+            assistant: expect.objectContaining({
+              id: expect.any(String),
+              name: expect.any(String),
+            }),
+          }),
+        })
+      )
+
+      // Verify persistence was attempted
       await vi.waitFor(() => {
-        expect(result.current.messages['thread1']).toContainEqual(mockCreatedMessage)
+        expect(mockCreateMessage).toHaveBeenCalled()
       })
     })
 

web-app/src/hooks/useAppState.ts

@@ -4,7 +4,7 @@ import { MCPTool } from '@/types/completion'
 import { useAssistant } from './useAssistant'
 import { ChatCompletionMessageToolCall } from 'openai/resources'
 
-type PromptProgress = {
+export type PromptProgress = {
   cache: number
   processed: number
   time_ms: number

web-app/src/hooks/useChat.ts

@@ -3,7 +3,7 @@ import { flushSync } from 'react-dom'
 import { usePrompt } from './usePrompt'
 import { useModelProvider } from './useModelProvider'
 import { useThreads } from './useThreads'
-import { useAppState } from './useAppState'
+import { useAppState, type PromptProgress } from './useAppState'
 import { useMessages } from './useMessages'
 import { useRouter } from '@tanstack/react-router'
 import { defaultModel } from '@/lib/models'
@@ -23,6 +23,7 @@ import {
   ChatCompletionMessageToolCall,
   CompletionUsage,
 } from 'openai/resources'
+import { MessageStatus, ContentType, ThreadMessage } from '@janhq/core'
 
 import { useServiceHub } from '@/hooks/useServiceHub'
 import { useToolApproval } from '@/hooks/useToolApproval'
@@ -38,6 +39,198 @@ import { useAssistant } from './useAssistant'
 import { useShallow } from 'zustand/shallow'
 import { TEMPORARY_CHAT_QUERY_ID, TEMPORARY_CHAT_ID } from '@/constants/chat'
 
+// Helper to create thread content with consistent structure
+const createThreadContent = (
+  threadId: string,
+  text: string,
+  toolCalls: ChatCompletionMessageToolCall[],
+  messageId?: string
+) => {
+  const content = newAssistantThreadContent(threadId, text, {
+    tool_calls: toolCalls.map((e) => ({
+      ...e,
+      state: 'pending',
+    })),
+  })
+  // If continuing from a message, preserve the message ID
+  if (messageId) {
+    return { ...content, id: messageId }
+  }
+  return content
+}
+
+// Helper to cancel animation frame cross-platform
+const cancelFrame = (handle: number | undefined) => {
+  if (handle === undefined) return
+  if (typeof cancelAnimationFrame !== 'undefined') {
+    cancelAnimationFrame(handle)
+  } else {
+    clearTimeout(handle)
+  }
+}
+
+// Helper to finalize and save a message
+const finalizeMessage = (
+  finalContent: ThreadMessage,
+  addMessage: (message: ThreadMessage) => void,
+  updateStreamingContent: (content: ThreadMessage | undefined) => void,
+  updatePromptProgress: (progress: PromptProgress | undefined) => void,
+  updateThreadTimestamp: (threadId: string) => void,
+  updateMessage?: (message: ThreadMessage) => void,
+  continueFromMessageId?: string
+) => {
+  // If continuing from a message, update it; otherwise add new message
+  if (continueFromMessageId && updateMessage) {
+    updateMessage({ ...finalContent, id: continueFromMessageId })
+  } else {
+    addMessage(finalContent)
+  }
+  updateStreamingContent(emptyThreadContent)
+  updatePromptProgress(undefined)
+  updateThreadTimestamp(finalContent.thread_id)
+}
+
+// Helper to process streaming completion
+const processStreamingCompletion = async (
+  // eslint-disable-next-line @typescript-eslint/no-explicit-any
+  completion: AsyncIterable<any>,
+  abortController: AbortController,
+  activeThread: Thread,
+  accumulatedText: { value: string },
+  toolCalls: ChatCompletionMessageToolCall[],
+  currentCall: ChatCompletionMessageToolCall | null,
+  updateStreamingContent: (content: ThreadMessage | undefined) => void,
+  updateTokenSpeed: (message: ThreadMessage, increment?: number) => void,
+  setTokenSpeed: (message: ThreadMessage, tokensPerSecond: number, totalTokens: number) => void,
+  updatePromptProgress: (progress: PromptProgress | undefined) => void,
+  timeToFirstToken: number,
+  tokenUsageRef: { current: CompletionUsage | undefined },
+  continueFromMessageId?: string,
+  updateMessage?: (message: ThreadMessage) => void,
+  continueFromMessage?: ThreadMessage
+) => {
+  // High-throughput scheduler: batch UI updates on rAF (requestAnimationFrame)
+  let rafScheduled = false
+  let rafHandle: number | undefined
+  let pendingDeltaCount = 0
+  const reasoningProcessor = new ReasoningProcessor()
+
+  const flushStreamingContent = () => {
+    const currentContent = createThreadContent(
+      activeThread.id,
+      accumulatedText.value,
+      toolCalls,
+      continueFromMessageId
+    )
+
+    // When continuing, update the message directly instead of using streamingContent
+    if (continueFromMessageId && updateMessage && continueFromMessage) {
+      updateMessage({
+        ...continueFromMessage, // Preserve original message metadata
+        content: currentContent.content, // Update content
+        status: MessageStatus.Stopped, // Keep as Stopped while streaming
+      })
+    } else {
+      updateStreamingContent(currentContent)
+    }
+
+    if (tokenUsageRef.current) {
+      setTokenSpeed(
+        currentContent,
+        tokenUsageRef.current.completion_tokens /
+          Math.max((Date.now() - timeToFirstToken) / 1000, 1),
+        tokenUsageRef.current.completion_tokens
+      )
+    } else if (pendingDeltaCount > 0) {
+      updateTokenSpeed(currentContent, pendingDeltaCount)
+    }
+    pendingDeltaCount = 0
+    rafScheduled = false
+  }
+
+  const scheduleFlush = () => {
+    if (rafScheduled || abortController.signal.aborted) return
+    rafScheduled = true
+    const doSchedule = (cb: () => void) => {
+      if (typeof requestAnimationFrame !== 'undefined') {
+        rafHandle = requestAnimationFrame(() => cb())
+      } else {
+        // Fallback for non-browser test environments
+        const t = setTimeout(() => cb(), 0) as unknown as number
+        rafHandle = t
+      }
+    }
+    doSchedule(() => {
+      // Check abort status before executing the scheduled callback
+      if (abortController.signal.aborted) {
+        rafScheduled = false
+        return
+      }
+      flushStreamingContent()
+    })
+  }
+
+  try {
+    for await (const part of completion) {
+      // Check if aborted before processing each part
+      if (abortController.signal.aborted) {
+        break
+      }
+
+      // Handle prompt progress if available
+      if ('prompt_progress' in part && part.prompt_progress) {
+        // Force immediate state update to ensure we see intermediate values
+        flushSync(() => {
+          updatePromptProgress(part.prompt_progress)
+        })
+        // Add a small delay to make progress visible
+        await new Promise((resolve) => setTimeout(resolve, 100))
+      }
+
+      // Error message
+      if (!part.choices) {
+        throw new Error(
+          'message' in part
+            ? (part.message as string)
+            : (JSON.stringify(part) ?? '')
+        )
+      }
+
+      if ('usage' in part && part.usage) {
+        tokenUsageRef.current = part.usage
+      }
+
+      if (part.choices[0]?.delta?.tool_calls) {
+        extractToolCall(part, currentCall, toolCalls)
+        // Schedule a flush to reflect tool update
+        scheduleFlush()
+      }
+      const deltaReasoning = reasoningProcessor.processReasoningChunk(part)
+      if (deltaReasoning) {
+        accumulatedText.value += deltaReasoning
+        pendingDeltaCount += 1
+        // Schedule flush for reasoning updates
+        scheduleFlush()
+      }
+      const deltaContent = part.choices[0]?.delta?.content || ''
+      if (deltaContent) {
+        accumulatedText.value += deltaContent
+        pendingDeltaCount += 1
+        // Batch UI update on next animation frame
+        scheduleFlush()
+      }
+    }
+  } finally {
+    // Always clean up scheduled RAF when stream ends (either normally or via abort)
+    cancelFrame(rafHandle)
+    rafHandle = undefined
+    rafScheduled = false
+
+    // Finalize reasoning (close any open think tags)
+    accumulatedText.value += reasoningProcessor.finalize()
+  }
+}
+
 export const useChat = () => {
   const [
     updateTokenSpeed,
@@ -86,6 +279,7 @@ export const useChat = () => {
 
   const getMessages = useMessages((state) => state.getMessages)
   const addMessage = useMessages((state) => state.addMessage)
+  const updateMessage = useMessages((state) => state.updateMessage)
   const setMessages = useMessages((state) => state.setMessages)
   const setModelLoadError = useModelLoad((state) => state.setModelLoadError)
   const router = useRouter()
@@ -149,7 +343,7 @@ export const useChat = () => {
       })
     }
     return currentThread
-  }, [createThread, retrieveThread, router, setMessages])
+  }, [createThread, retrieveThread, router, setMessages, serviceHub])
 
   const restartModel = useCallback(
     async (provider: ProviderObject, modelId: string) => {
@@ -264,7 +458,8 @@ export const useChat = () => {
         base64: string
         dataUrl: string
       }>,
-      projectId?: string
+      projectId?: string,
+      continueFromMessageId?: string
     ) => {
       const activeThread = await getCurrentThread(projectId)
       const selectedProvider = useModelProvider.getState().selectedProvider
@@ -277,26 +472,54 @@ export const useChat = () => {
       setAbortController(activeThread.id, abortController)
       updateStreamingContent(emptyThreadContent)
       updatePromptProgress(undefined)
-      // Do not add new message on retry
-      if (troubleshooting)
+
+      // Find the message to continue from if provided
+      const continueFromMessage = continueFromMessageId
+        ? messages.find((m) => m.id === continueFromMessageId)
+        : undefined
+
+      // Do not add new message on retry or when continuing
+      if (troubleshooting && !continueFromMessageId)
         addMessage(newUserThreadContent(activeThread.id, message, attachments))
       updateThreadTimestamp(activeThread.id)
       usePrompt.getState().setPrompt('')
       const selectedModel = useModelProvider.getState().selectedModel
+
+      // If continuing, start with the previous content
+      const accumulatedTextRef = {
+        value: continueFromMessage?.content?.[0]?.text?.value || ''
+      }
+      let currentAssistant: Assistant | undefined | null
+
       try {
         if (selectedModel?.id) {
           updateLoadingModel(true)
           await serviceHub.models().startModel(activeProvider, selectedModel.id)
           updateLoadingModel(false)
         }
-        const currentAssistant = useAssistant.getState().currentAssistant
+        currentAssistant = useAssistant.getState().currentAssistant
+
+        // Filter out the stopped message from context if continuing
+        const contextMessages = continueFromMessageId
+          ? messages.filter((m) => m.id !== continueFromMessageId)
+          : messages
+
         const builder = new CompletionMessagesBuilder(
-          messages,
+          contextMessages,
           currentAssistant
             ? renderInstructions(currentAssistant.instructions)
             : undefined
         )
-        if (troubleshooting) builder.addUserMessage(message, attachments)
+        if (troubleshooting && !continueFromMessageId) {
+          builder.addUserMessage(message, attachments)
+        } else if (continueFromMessage) {
+          // When continuing, add the partial assistant response to the context
+          builder.addAssistantMessage(
+            continueFromMessage.content?.[0]?.text?.value || '',
+            undefined,
+            []
+          )
+        }
 
         let isCompleted = false
 
@@ -349,7 +572,6 @@ export const useChat = () => {
           )
 
           if (!completion) throw new Error('No completion received')
-          let accumulatedText = ''
           const currentCall: ChatCompletionMessageToolCall | null = null
           const toolCalls: ChatCompletionMessageToolCall[] = []
           const timeToFirstToken = Date.now()
@@ -357,13 +579,19 @@ export const useChat = () => {
           try {
             if (isCompletionResponse(completion)) {
               const message = completion.choices[0]?.message
-              accumulatedText = (message?.content as string) || ''
+              // When continuing, append to existing content; otherwise replace
+              const newContent = (message?.content as string) || ''
+              if (continueFromMessageId && accumulatedTextRef.value) {
+                accumulatedTextRef.value += newContent
+              } else {
+                accumulatedTextRef.value = newContent
+              }
 
               // Handle reasoning field if there is one
               const reasoning = extractReasoningFromMessage(message)
               if (reasoning) {
-                accumulatedText =
-                  `<think>${reasoning}</think>` + accumulatedText
+                accumulatedTextRef.value =
+                  `<think>${reasoning}</think>` + accumulatedTextRef.value
               }
 
               if (message?.tool_calls) {
@@ -373,161 +601,25 @@ export const useChat = () => {
                 tokenUsage = completion.usage
               }
             } else {
-              // High-throughput scheduler: batch UI updates on rAF (requestAnimationFrame)
-              let rafScheduled = false
-              let rafHandle: number | undefined
-              let pendingDeltaCount = 0
-              const reasoningProcessor = new ReasoningProcessor()
-              const scheduleFlush = () => {
-                if (rafScheduled || abortController.signal.aborted) return
-                rafScheduled = true
-                const doSchedule = (cb: () => void) => {
-                  if (typeof requestAnimationFrame !== 'undefined') {
-                    rafHandle = requestAnimationFrame(() => cb())
-                  } else {
-                    // Fallback for non-browser test environments
-                    const t = setTimeout(() => cb(), 0) as unknown as number
-                    rafHandle = t
-                  }
-                }
-                doSchedule(() => {
-                  // Check abort status before executing the scheduled callback
-                  if (abortController.signal.aborted) {
-                    rafScheduled = false
-                    return
-                  }
-
-                  const currentContent = newAssistantThreadContent(
-                    activeThread.id,
-                    accumulatedText,
-                    {
-                      tool_calls: toolCalls.map((e) => ({
-                        ...e,
-                        state: 'pending',
-                      })),
-                    }
-                  )
-                  updateStreamingContent(currentContent)
-                  if (tokenUsage) {
-                    setTokenSpeed(
-                      currentContent,
-                      tokenUsage.completion_tokens /
-                        Math.max((Date.now() - timeToFirstToken) / 1000, 1),
-                      tokenUsage.completion_tokens
-                    )
-                  } else if (pendingDeltaCount > 0) {
-                    updateTokenSpeed(currentContent, pendingDeltaCount)
-                  }
-                  pendingDeltaCount = 0
-                  rafScheduled = false
-                })
-              }
-              const flushIfPending = () => {
-                if (!rafScheduled) return
-                if (
-                  typeof cancelAnimationFrame !== 'undefined' &&
-                  rafHandle !== undefined
-                ) {
-                  cancelAnimationFrame(rafHandle)
-                } else if (rafHandle !== undefined) {
-                  clearTimeout(rafHandle)
-                }
-                // Do an immediate flush
-                const currentContent = newAssistantThreadContent(
-                  activeThread.id,
-                  accumulatedText,
-                  {
-                    tool_calls: toolCalls.map((e) => ({
-                      ...e,
-                      state: 'pending',
-                    })),
-                  }
-                )
-                updateStreamingContent(currentContent)
-                if (tokenUsage) {
-                  setTokenSpeed(
-                    currentContent,
-                    tokenUsage.completion_tokens /
-                      Math.max((Date.now() - timeToFirstToken) / 1000, 1),
-                    tokenUsage.completion_tokens
-                  )
-                } else if (pendingDeltaCount > 0) {
-                  updateTokenSpeed(currentContent, pendingDeltaCount)
-                }
-                pendingDeltaCount = 0
-                rafScheduled = false
-              }
-              try {
-                for await (const part of completion) {
-                  // Check if aborted before processing each part
-                  if (abortController.signal.aborted) {
-                    break
-                  }
-
-                  // Handle prompt progress if available
-                  if ('prompt_progress' in part && part.prompt_progress) {
-                    // Force immediate state update to ensure we see intermediate values
-                    flushSync(() => {
-                      updatePromptProgress(part.prompt_progress)
-                    })
-                    // Add a small delay to make progress visible
-                    await new Promise((resolve) => setTimeout(resolve, 100))
-                  }
-
-                  // Error message
-                  if (!part.choices) {
-                    throw new Error(
-                      'message' in part
-                        ? (part.message as string)
-                        : (JSON.stringify(part) ?? '')
-                    )
-                  }
-
-                  if ('usage' in part && part.usage) {
-                    tokenUsage = part.usage
-                  }
-
-                  if (part.choices[0]?.delta?.tool_calls) {
-                    extractToolCall(part, currentCall, toolCalls)
-                    // Schedule a flush to reflect tool update
-                    scheduleFlush()
-                  }
-                  const deltaReasoning =
-                    reasoningProcessor.processReasoningChunk(part)
-                  if (deltaReasoning) {
-                    accumulatedText += deltaReasoning
-                    pendingDeltaCount += 1
-                    // Schedule flush for reasoning updates
-                    scheduleFlush()
-                  }
-                  const deltaContent = part.choices[0]?.delta?.content || ''
-                  if (deltaContent) {
-                    accumulatedText += deltaContent
-                    pendingDeltaCount += 1
-                    // Batch UI update on next animation frame
-                    scheduleFlush()
-                  }
-                }
-              } finally {
-                // Always clean up scheduled RAF when stream ends (either normally or via abort)
-                if (rafHandle !== undefined) {
-                  if (typeof cancelAnimationFrame !== 'undefined') {
-                    cancelAnimationFrame(rafHandle)
-                  } else {
-                    clearTimeout(rafHandle)
-                  }
-                  rafHandle = undefined
-                  rafScheduled = false
-                }
-
-                // Only finalize and flush if not aborted
-                if (!abortController.signal.aborted) {
-                  // Finalize reasoning (close any open think tags)
-                  accumulatedText += reasoningProcessor.finalize()
-                  // Ensure any pending buffered content is rendered at the end
-                  flushIfPending()
-                }
-              }
+              const tokenUsageRef = { current: tokenUsage }
+              await processStreamingCompletion(
+                completion,
+                abortController,
+                activeThread,
+                accumulatedTextRef,
+                toolCalls,
+                currentCall,
+                updateStreamingContent,
+                updateTokenSpeed,
+                setTokenSpeed,
+                updatePromptProgress,
+                timeToFirstToken,
+                tokenUsageRef,
+                continueFromMessageId,
+                updateMessage,
+                continueFromMessage
+              )
+              tokenUsage = tokenUsageRef.current
             }
           } catch (error) {
             const errorMessage =
@@ -561,7 +653,7 @@ export const useChat = () => {
           }
           // TODO: Remove this check when integrating new llama.cpp extension
           if (
-            accumulatedText.length === 0 &&
+            accumulatedTextRef.value.length === 0 &&
             toolCalls.length === 0 &&
             activeThread.model?.id &&
             activeProvider?.provider === 'llamacpp'
@@ -573,16 +665,29 @@ export const useChat = () => {
           }
 
           // Create a final content object for adding to the thread
-          const finalContent = newAssistantThreadContent(
+          let finalContent = newAssistantThreadContent(
             activeThread.id,
-            accumulatedText,
+            accumulatedTextRef.value,
             {
               tokenSpeed: useAppState.getState().tokenSpeed,
               assistant: currentAssistant,
             }
           )
 
-          builder.addAssistantMessage(accumulatedText, undefined, toolCalls)
+          // If continuing from a message, preserve the ID and set status to Ready
+          if (continueFromMessageId) {
+            finalContent = {
+              ...finalContent,
+              id: continueFromMessageId,
+              status: MessageStatus.Ready,
+            }
+          }
+
+          // Normal completion flow (abort is handled after loop exits)
+          // Don't add assistant message to builder if continuing - it's already there
+          if (!continueFromMessageId) {
+            builder.addAssistantMessage(accumulatedTextRef.value, undefined, toolCalls)
+          }
           const updatedMessage = await postMessageProcessing(
             toolCalls,
             builder,
@@ -592,10 +697,15 @@ export const useChat = () => {
             allowAllMCPPermissions ? undefined : showApprovalModal,
             allowAllMCPPermissions
           )
-          addMessage(updatedMessage ?? finalContent)
-          updateStreamingContent(emptyThreadContent)
-          updatePromptProgress(undefined)
-          updateThreadTimestamp(activeThread.id)
+          finalizeMessage(
+            updatedMessage ?? finalContent,
+            addMessage,
+            updateStreamingContent,
+            updatePromptProgress,
+            updateThreadTimestamp,
+            updateMessage,
+            continueFromMessageId
+          )
 
           isCompleted = !toolCalls.length
           // Do not create agent loop if there is no need for it
@@ -605,8 +715,109 @@ export const useChat = () => {
             availableTools = []
           }
         }
+
+        // IMPORTANT: Check if aborted AFTER the while loop exits
+        // The while loop exits when abort is true, so we handle it here
+        // Only save interrupted messages for llamacpp provider
+        // Other providers (OpenAI, Claude, etc.) handle streaming differently
+        if (
+          abortController.signal.aborted &&
+          accumulatedTextRef.value.length > 0 &&
+          activeProvider?.provider === 'llamacpp'
+        ) {
+          // If continuing, update the existing message; otherwise add new
+          if (continueFromMessageId && continueFromMessage) {
+            // Preserve the original message metadata
+            updateMessage({
+              ...continueFromMessage,
+              content: [
+                {
+                  type: ContentType.Text,
+                  text: {
+                    value: accumulatedTextRef.value,
+                    annotations: [],
+                  },
+                },
+              ],
+              status: MessageStatus.Stopped,
+              metadata: {
+                ...continueFromMessage.metadata,
+                tokenSpeed: useAppState.getState().tokenSpeed,
+                assistant: currentAssistant,
+              },
+            })
+          } else {
+            // Create final content for the partial message with Stopped status
+            const partialContent = {
+              ...newAssistantThreadContent(
+                activeThread.id,
+                accumulatedTextRef.value,
+                {
+                  tokenSpeed: useAppState.getState().tokenSpeed,
+                  assistant: currentAssistant,
+                }
+              ),
+              status: MessageStatus.Stopped,
+            }
+            addMessage(partialContent)
+          }
+          updatePromptProgress(undefined)
+          updateThreadTimestamp(activeThread.id)
+        }
       } catch (error) {
-        if (!abortController.signal.aborted) {
+        // If aborted, save the partial message even though an error occurred
+        // Only save for llamacpp provider - other providers handle streaming differently
+        const streamingContent = useAppState.getState().streamingContent
+        const hasPartialContent = accumulatedTextRef.value.length > 0 ||
+          (streamingContent && streamingContent.content?.[0]?.text?.value)
+
+        if (
+          abortController.signal.aborted &&
+          hasPartialContent &&
+          activeProvider?.provider === 'llamacpp'
+        ) {
+          // Use streaming content if available, otherwise use accumulatedTextRef
+          const contentText = streamingContent?.content?.[0]?.text?.value || accumulatedTextRef.value
+
+          // If continuing, update the existing message; otherwise add new
+          if (continueFromMessageId && continueFromMessage) {
+            // Preserve the original message metadata
+            updateMessage({
+              ...continueFromMessage,
+              content: [
+                {
+                  type: ContentType.Text,
+                  text: {
+                    value: contentText,
+                    annotations: [],
+                  },
+                },
+              ],
+              status: MessageStatus.Stopped,
+              metadata: {
+                ...continueFromMessage.metadata,
+                tokenSpeed: useAppState.getState().tokenSpeed,
+                assistant: currentAssistant,
+              },
+            })
+          } else {
+            const partialContent = {
+              ...newAssistantThreadContent(
+                activeThread.id,
+                contentText,
+                {
+                  tokenSpeed: useAppState.getState().tokenSpeed,
+                  assistant: currentAssistant,
+                }
+              ),
+              status: MessageStatus.Stopped,
+            }
+            addMessage(partialContent)
+          }
+          updatePromptProgress(undefined)
+          updateThreadTimestamp(activeThread.id)
+        } else if (!abortController.signal.aborted) {
+          // Only show error if not aborted
           if (error && typeof error === 'object' && 'message' in error) {
             setModelLoadError(error as ErrorObject)
           } else {
@@ -628,12 +839,14 @@ export const useChat = () => {
       updateStreamingContent,
       updatePromptProgress,
       addMessage,
+      updateMessage,
       updateThreadTimestamp,
       updateLoadingModel,
       getDisabledToolsForThread,
       allowAllMCPPermissions,
       showApprovalModal,
       updateTokenSpeed,
+      setTokenSpeed,
       showIncreaseContextSizeModal,
       increaseModelContextSize,
       toggleOnContextShifting,

web-app/src/hooks/useMessages.ts

@@ -8,6 +8,7 @@ type MessageState = {
   getMessages: (threadId: string) => ThreadMessage[]
   setMessages: (threadId: string, messages: ThreadMessage[]) => void
   addMessage: (message: ThreadMessage) => void
+  updateMessage: (message: ThreadMessage) => void
   deleteMessage: (threadId: string, messageId: string) => void
   clearAllMessages: () => void
 }
@@ -40,16 +41,52 @@ export const useMessages = create<MessageState>()((set, get) => ({
         assistant: selectedAssistant,
       },
     }
-    getServiceHub().messages().createMessage(newMessage).then((createdMessage) => {
-      set((state) => ({
-        messages: {
-          ...state.messages,
-          [message.thread_id]: [
-            ...(state.messages[message.thread_id] || []),
-            createdMessage,
-          ],
-        },
-      }))
+
+    // Optimistically update state immediately for instant UI feedback
+    set((state) => ({
+      messages: {
+        ...state.messages,
+        [message.thread_id]: [
+          ...(state.messages[message.thread_id] || []),
+          newMessage,
+        ],
+      },
+    }))
+
+    // Persist to storage asynchronously
+    getServiceHub().messages().createMessage(newMessage).catch((error) => {
+      console.error('Failed to persist message:', error)
+    })
+  },
+  updateMessage: (message) => {
+    const assistants = useAssistant.getState().assistants
+    const currentAssistant = useAssistant.getState().currentAssistant
+
+    const selectedAssistant =
+      assistants.find((a) => a.id === currentAssistant?.id) || assistants[0]
+
+    const updatedMessage = {
+      ...message,
+      metadata: {
+        ...message.metadata,
+        assistant: selectedAssistant,
+      },
+    }
+
+    // Optimistically update state immediately for instant UI feedback
+    set((state) => ({
+      messages: {
+        ...state.messages,
+        [message.thread_id]: (state.messages[message.thread_id] || []).map((m) =>
+          m.id === message.id ? updatedMessage : m
+        ),
+      },
+    }))
+
+    // Persist to storage asynchronously using modifyMessage instead of createMessage
+    // to prevent duplicates when updating existing messages
+    getServiceHub().messages().modifyMessage(updatedMessage).catch((error) => {
+      console.error('Failed to persist message update:', error)
     })
   },
   deleteMessage: (threadId, messageId) => {

web-app/src/hooks/useTools.ts

@@ -23,8 +23,9 @@ export const useTools = () => {
         updateTools(data)
 
         // Initialize default disabled tools for new users (only once)
-        if (!isDefaultsInitialized() && data.length > 0 && mcpExtension?.getDefaultDisabledTools) {
-          const defaultDisabled = await mcpExtension.getDefaultDisabledTools()
+        const mcpExt = mcpExtension as MCPExtension & { getDefaultDisabledTools?: () => Promise<string[]> }
+        if (!isDefaultsInitialized() && data.length > 0 && mcpExt?.getDefaultDisabledTools) {
+          const defaultDisabled = await mcpExt.getDefaultDisabledTools()
           if (defaultDisabled.length > 0) {
             setDefaultDisabledTools(defaultDisabled)
             markDefaultsAsInitialized()

web-app/src/locales/en/common.json

@@ -135,6 +135,7 @@
   "enterApiKey": "Enter API Key",
   "scrollToBottom": "Scroll to bottom",
   "generateAiResponse": "Generate AI Response",
+  "continueAiResponse": "Continue with AI Response",
   "addModel": {
     "title": "Add Model",
     "modelId": "Model ID",

web-app/src/services/messages/default.ts

@@ -40,6 +40,20 @@ export class DefaultMessagesService implements MessagesService {
     )
   }
 
+  async modifyMessage(message: ThreadMessage): Promise<ThreadMessage> {
+    // Don't modify messages on server for temporary chat - it's local only
+    if (message.thread_id === TEMPORARY_CHAT_ID) {
+      return message
+    }
+
+    return (
+      ExtensionManager.getInstance()
+        .get<ConversationalExtension>(ExtensionTypeEnum.Conversational)
+        ?.modifyMessage(message)
+        ?.catch(() => message) ?? message
+    )
+  }
+
   async deleteMessage(threadId: string, messageId: string): Promise<void> {
     // Don't delete messages on server for temporary chat - it's local only
     if (threadId === TEMPORARY_CHAT_ID) {

web-app/src/services/messages/types.ts

@@ -7,5 +7,6 @@ import { ThreadMessage } from '@janhq/core'
 export interface MessagesService {
   fetchMessages(threadId: string): Promise<ThreadMessage[]>
   createMessage(message: ThreadMessage): Promise<ThreadMessage>
+  modifyMessage(message: ThreadMessage): Promise<ThreadMessage>
   deleteMessage(threadId: string, messageId: string): Promise<void>
 }