fix: handle Mistral thinking content as reasoning chunks (#7106)

* fix: handle Mistral thinking content as reasoning chunks

- Add TypeScript interfaces for Mistral content types (text and thinking)
- Update createMessage to yield reasoning chunks for thinking content
- Update completePrompt to filter out thinking content in non-streaming mode
- Add comprehensive tests for reasoning content handling
- Follow the pattern used by other providers (Anthropic, OpenAI, Gemini, etc.)

Fixes #6842

* fix: resolve TypeScript type issue in completePrompt method

* fix: handle Mistral thinking content chunks in streaming responses

- Added ContentChunkWithThinking type helper to handle thinking chunks
- Properly converts thinking content to reasoning chunks in streaming
- Filters out thinking content in non-streaming completePrompt responses
- Confirmed that Mistral API does send thinking chunks with type 'thinking'
- Works with Mistral SDK v1.9.18

---------

Co-authored-by: Roo Code <[email protected]>
Co-authored-by: daniel-lxs <[email protected]>

Author: 3 people

pnpm-lock.yaml

@@ -1,5 +1,6 @@
 // Mock Mistral client - must come before other imports
 const mockCreate = vi.fn()
+const mockComplete = vi.fn()
 vi.mock("@mistralai/mistralai", () => {
 	return {
 		Mistral: vi.fn().mockImplementation(() => ({
@@ -21,6 +22,17 @@ vi.mock("@mistralai/mistralai", () => {
 					}
 					return stream
 				}),
+				complete: mockComplete.mockImplementation(async (_options) => {
+					return {
+						choices: [
+							{
+								message: {
+									content: "Test response",
+								},
+							},
+						],
+					}
+				}),
 			},
 		})),
 	}
@@ -29,7 +41,7 @@ vi.mock("@mistralai/mistralai", () => {
 import type { Anthropic } from "@anthropic-ai/sdk"
 import { MistralHandler } from "../mistral"
 import type { ApiHandlerOptions } from "../../../shared/api"
-import type { ApiStreamTextChunk } from "../../transform/stream"
+import type { ApiStreamTextChunk, ApiStreamReasoningChunk } from "../../transform/stream"
 
 describe("MistralHandler", () => {
 	let handler: MistralHandler
@@ -44,6 +56,7 @@ describe("MistralHandler", () => {
 		}
 		handler = new MistralHandler(mockOptions)
 		mockCreate.mockClear()
+		mockComplete.mockClear()
 	})
 
 	describe("constructor", () => {
@@ -122,5 +135,134 @@ describe("MistralHandler", () => {
 			mockCreate.mockRejectedValueOnce(new Error("API Error"))
 			await expect(handler.createMessage(systemPrompt, messages).next()).rejects.toThrow("API Error")
 		})
+
+		it("should handle thinking content as reasoning chunks", async () => {
+			// Mock stream with thinking content matching new SDK structure
+			mockCreate.mockImplementationOnce(async (_options) => {
+				const stream = {
+					[Symbol.asyncIterator]: async function* () {
+						yield {
+							data: {
+								choices: [
+									{
+										delta: {
+											content: [
+												{
+													type: "thinking",
+													thinking: [{ type: "text", text: "Let me think about this..." }],
+												},
+												{ type: "text", text: "Here's the answer" },
+											],
+										},
+										index: 0,
+									},
+								],
+							},
+						}
+					},
+				}
+				return stream
+			})
+
+			const iterator = handler.createMessage(systemPrompt, messages)
+			const results: (ApiStreamTextChunk | ApiStreamReasoningChunk)[] = []
+
+			for await (const chunk of iterator) {
+				if ("text" in chunk) {
+					results.push(chunk as ApiStreamTextChunk | ApiStreamReasoningChunk)
+				}
+			}
+
+			expect(results).toHaveLength(2)
+			expect(results[0]).toEqual({ type: "reasoning", text: "Let me think about this..." })
+			expect(results[1]).toEqual({ type: "text", text: "Here's the answer" })
+		})
+
+		it("should handle mixed content arrays correctly", async () => {
+			// Mock stream with mixed content matching new SDK structure
+			mockCreate.mockImplementationOnce(async (_options) => {
+				const stream = {
+					[Symbol.asyncIterator]: async function* () {
+						yield {
+							data: {
+								choices: [
+									{
+										delta: {
+											content: [
+												{ type: "text", text: "First text" },
+												{
+													type: "thinking",
+													thinking: [{ type: "text", text: "Some reasoning" }],
+												},
+												{ type: "text", text: "Second text" },
+											],
+										},
+										index: 0,
+									},
+								],
+							},
+						}
+					},
+				}
+				return stream
+			})
+
+			const iterator = handler.createMessage(systemPrompt, messages)
+			const results: (ApiStreamTextChunk | ApiStreamReasoningChunk)[] = []
+
+			for await (const chunk of iterator) {
+				if ("text" in chunk) {
+					results.push(chunk as ApiStreamTextChunk | ApiStreamReasoningChunk)
+				}
+			}
+
+			expect(results).toHaveLength(3)
+			expect(results[0]).toEqual({ type: "text", text: "First text" })
+			expect(results[1]).toEqual({ type: "reasoning", text: "Some reasoning" })
+			expect(results[2]).toEqual({ type: "text", text: "Second text" })
+		})
+	})
+
+	describe("completePrompt", () => {
+		it("should complete prompt successfully", async () => {
+			const prompt = "Test prompt"
+			const result = await handler.completePrompt(prompt)
+
+			expect(mockComplete).toHaveBeenCalledWith({
+				model: mockOptions.apiModelId,
+				messages: [{ role: "user", content: prompt }],
+				temperature: 0,
+			})
+
+			expect(result).toBe("Test response")
+		})
+
+		it("should filter out thinking content in completePrompt", async () => {
+			mockComplete.mockImplementationOnce(async (_options) => {
+				return {
+					choices: [
+						{
+							message: {
+								content: [
+									{ type: "thinking", text: "Let me think..." },
+									{ type: "text", text: "Answer part 1" },
+									{ type: "text", text: "Answer part 2" },
+								],
+							},
+						},
+					],
+				}
+			})
+
+			const prompt = "Test prompt"
+			const result = await handler.completePrompt(prompt)
+
+			expect(result).toBe("Answer part 1Answer part 2")
+		})
+
+		it("should handle errors in completePrompt", async () => {
+			mockComplete.mockRejectedValueOnce(new Error("API Error"))
+			await expect(handler.completePrompt("Test prompt")).rejects.toThrow("Mistral completion error: API Error")
+		})
 	})
 })

src/api/providers/__tests__/mistral.spec.ts

@@ -11,6 +11,14 @@ import { ApiStream } from "../transform/stream"
 import { BaseProvider } from "./base-provider"
 import type { SingleCompletionHandler, ApiHandlerCreateMessageMetadata } from "../index"
 
+// Type helper to handle thinking chunks from Mistral API
+// The SDK includes ThinkChunk but TypeScript has trouble with the discriminated union
+type ContentChunkWithThinking = {
+	type: string
+	text?: string
+	thinking?: Array<{ type: string; text?: string }>
+}
+
 export class MistralHandler extends BaseProvider implements SingleCompletionHandler {
 	protected options: ApiHandlerOptions
 	private client: Mistral
@@ -48,26 +56,38 @@ export class MistralHandler extends BaseProvider implements SingleCompletionHand
 			temperature,
 		})
 
-		for await (const chunk of response) {
-			const delta = chunk.data.choices[0]?.delta
+		for await (const event of response) {
+			const delta = event.data.choices[0]?.delta
 
 			if (delta?.content) {
-				let content: string = ""
-
 				if (typeof delta.content === "string") {
-					content = delta.content
+					// Handle string content as text
+					yield { type: "text", text: delta.content }
 				} else if (Array.isArray(delta.content)) {
-					content = delta.content.map((c) => (c.type === "text" ? c.text : "")).join("")
+					// Handle array of content chunks
+					// The SDK v1.9.18 supports ThinkChunk with type "thinking"
+					for (const chunk of delta.content as ContentChunkWithThinking[]) {
+						if (chunk.type === "thinking" && chunk.thinking) {
+							// Handle thinking content as reasoning chunks
+							// ThinkChunk has a 'thinking' property that contains an array of text/reference chunks
+							for (const thinkingPart of chunk.thinking) {
+								if (thinkingPart.type === "text" && thinkingPart.text) {
+									yield { type: "reasoning", text: thinkingPart.text }
+								}
+							}
+						} else if (chunk.type === "text" && chunk.text) {
+							// Handle text content normally
+							yield { type: "text", text: chunk.text }
+						}
+					}
 				}
-
-				yield { type: "text", text: content }
 			}
 
-			if (chunk.data.usage) {
+			if (event.data.usage) {
 				yield {
 					type: "usage",
-					inputTokens: chunk.data.usage.promptTokens || 0,
-					outputTokens: chunk.data.usage.completionTokens || 0,
+					inputTokens: event.data.usage.promptTokens || 0,
+					outputTokens: event.data.usage.completionTokens || 0,
 				}
 			}
 		}
@@ -97,7 +117,11 @@ export class MistralHandler extends BaseProvider implements SingleCompletionHand
 			const content = response.choices?.[0]?.message.content
 
 			if (Array.isArray(content)) {
-				return content.map((c) => (c.type === "text" ? c.text : "")).join("")
+				// Only return text content, filter out thinking content for non-streaming
+				return (content as ContentChunkWithThinking[])
+					.filter((c) => c.type === "text" && c.text)
+					.map((c) => c.text || "")
+					.join("")
 			}
 
 			return content || ""

src/api/providers/mistral.ts

@@ -429,7 +429,7 @@
 		"@aws-sdk/credential-providers": "^3.848.0",
 		"@google/genai": "^1.0.0",
 		"@lmstudio/sdk": "^1.1.1",
-		"@mistralai/mistralai": "^1.3.6",
+		"@mistralai/mistralai": "^1.9.18",
 		"@modelcontextprotocol/sdk": "^1.9.0",
 		"@qdrant/js-client-rest": "^1.14.0",
 		"@roo-code/cloud": "^0.19.0",