fix(vscode-lm): order text parts before tool calls in assistant messages (#10573)

Author: daniel-lxs

src/api/transform/__tests__/vscode-lm-format.spec.ts

@@ -143,9 +143,11 @@ describe("convertToVsCodeLmMessages", () => {
 		expect(result).toHaveLength(1)
 		expect(result[0].role).toBe("assistant")
 		expect(result[0].content).toHaveLength(2)
-		const [toolCall, textContent] = result[0].content as [MockLanguageModelToolCallPart, MockLanguageModelTextPart]
-		expect(toolCall.type).toBe("tool_call")
+		// Text must come before tool calls so that tool calls are at the end,
+		// properly followed by user message with tool results
+		const [textContent, toolCall] = result[0].content as [MockLanguageModelTextPart, MockLanguageModelToolCallPart]
 		expect(textContent.type).toBe("text")
+		expect(toolCall.type).toBe("tool_call")
 	})
 
 	it("should handle image blocks with appropriate placeholders", () => {

src/api/transform/vscode-lm-format.ts

@@ -114,9 +114,18 @@ export function convertToVsCodeLmMessages(
 					{ nonToolMessages: [], toolMessages: [] },
 				)
 
-				// Process tool messages first then non-tool messages
+				// Process non-tool messages first, then tool messages
+				// Tool calls must come at the end so they are properly followed by user message with tool results
 				const contentParts = [
-					// Convert tool messages to ToolCallParts first
+					// Convert non-tool messages to TextParts first
+					...nonToolMessages.map((part) => {
+						if (part.type === "image") {
+							return new vscode.LanguageModelTextPart("[Image generation not supported by VSCode LM API]")
+						}
+						return new vscode.LanguageModelTextPart(part.text)
+					}),
+
+					// Convert tool messages to ToolCallParts after text
 					...toolMessages.map(
 						(toolMessage) =>
 							new vscode.LanguageModelToolCallPart(
@@ -125,14 +134,6 @@ export function convertToVsCodeLmMessages(
 								asObjectSafe(toolMessage.input),
 							),
 					),
-
-					// Convert non-tool messages to TextParts after tool messages
-					...nonToolMessages.map((part) => {
-						if (part.type === "image") {
-							return new vscode.LanguageModelTextPart("[Image generation not supported by VSCode LM API]")
-						}
-						return new vscode.LanguageModelTextPart(part.text)
-					}),
 				]
 
 				// Add the assistant message to the list of messages