fix: preserve thinking block (#11901)

* fix: preserve thinking block

* test: add coverage for reasoning parts in assistant messages (#11902)

* Initial plan

* test: add test coverage for reasoning parts in assistant messages

Co-authored-by: DeJeune <67425183+DeJeune@users.noreply.github.com>

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: DeJeune <67425183+DeJeune@users.noreply.github.com>

---------

Co-authored-by: Copilot <198982749+Copilot@users.noreply.github.com>

src/renderer/src/aiCore/prepareParams/__tests__/message-converter.test.ts

@@ -109,6 +109,20 @@ const createImageBlock = (
   ...overrides
 })
 
+const createThinkingBlock = (
+  messageId: string,
+  overrides: Partial<Omit<ThinkingMessageBlock, 'type' | 'messageId'>> = {}
+): ThinkingMessageBlock => ({
+  id: overrides.id ?? `thinking-block-${++blockCounter}`,
+  messageId,
+  type: MessageBlockType.THINKING,
+  createdAt: overrides.createdAt ?? new Date(2024, 0, 1, 0, 0, blockCounter).toISOString(),
+  status: overrides.status ?? MessageBlockStatus.SUCCESS,
+  content: overrides.content ?? 'Let me think...',
+  thinking_millsec: overrides.thinking_millsec ?? 1000,
+  ...overrides
+})
+
 describe('messageConverter', () => {
   beforeEach(() => {
     convertFileBlockToFilePartMock.mockReset()
@@ -229,6 +243,23 @@ describe('messageConverter', () => {
         }
       ])
     })
+
+    it('includes reasoning parts for assistant messages with thinking blocks', async () => {
+      const model = createModel()
+      const message = createMessage('assistant')
+      message.__mockContent = 'Here is my answer'
+      message.__mockThinkingBlocks = [createThinkingBlock(message.id, { content: 'Let me think...' })]
+
+      const result = await convertMessageToSdkParam(message, false, model)
+
+      expect(result).toEqual({
+        role: 'assistant',
+        content: [
+          { type: 'text', text: 'Here is my answer' },
+          { type: 'reasoning', text: 'Let me think...' }
+        ]
+      })
+    })
   })
 
   describe('convertMessagesToSdkMessages', () => {

src/renderer/src/aiCore/prepareParams/messageConverter.ts

@@ -3,6 +3,7 @@
  * 将 Cherry Studio 消息格式转换为 AI SDK 消息格式
  */
 
+import type { ReasoningPart } from '@ai-sdk/provider-utils'
 import { loggerService } from '@logger'
 import { isImageEnhancementModel, isVisionModel } from '@renderer/config/models'
 import type { Message, Model } from '@renderer/types'
@@ -163,13 +164,13 @@ async function convertMessageToAssistantModelMessage(
   thinkingBlocks: ThinkingMessageBlock[],
   model?: Model
 ): Promise<AssistantModelMessage> {
-  const parts: Array<TextPart | FilePart> = []
+  const parts: Array<TextPart | ReasoningPart | FilePart> = []
   if (content) {
     parts.push({ type: 'text', text: content })
   }
 
   for (const thinkingBlock of thinkingBlocks) {
-    parts.push({ type: 'text', text: thinkingBlock.content })
+    parts.push({ type: 'reasoning', text: thinkingBlock.content })
   }
 
   for (const fileBlock of fileBlocks) {