feat(vscode-lm): add Copilot modelOptions for agent request classification

When the VS Code LM model vendor is "copilot", attach modelOptions
with copilot-integration-id to sendRequest calls. This allows the
Copilot backend to distinguish agent-initiated requests from
direct user chat, which may help with proper billing classification
of premium vs non-premium requests.

Requires VS Code >= 1.96 where modelOptions became stable; older
versions silently ignore the extra property.

Refs: #11289

src/api/providers/__tests__/vscode-lm.spec.ts

@@ -391,6 +391,63 @@ describe("VsCodeLmHandler", () => {
 
 			await expect(handler.createMessage(systemPrompt, messages).next()).rejects.toThrow("API Error")
 		})
+
+		it("should include modelOptions when model vendor is copilot", async () => {
+			// Create a Copilot-vendor mock model
+			const copilotModel = {
+				...mockLanguageModelChat,
+				vendor: "copilot",
+				name: "GPT-4o",
+			}
+			handler["client"] = copilotModel as any
+
+			const systemPrompt = "You are a helpful assistant"
+			const messages: Anthropic.Messages.MessageParam[] = [{ role: "user" as const, content: "Hello" }]
+
+			copilotModel.sendRequest.mockResolvedValueOnce({
+				stream: (async function* () {
+					yield new vscode.LanguageModelTextPart("Hi there")
+				})(),
+			})
+			copilotModel.countTokens.mockResolvedValue(5)
+
+			const stream = handler.createMessage(systemPrompt, messages)
+			const chunks = []
+			for await (const chunk of stream) {
+				chunks.push(chunk)
+			}
+
+			expect(copilotModel.sendRequest).toHaveBeenCalledWith(
+				expect.any(Array),
+				expect.objectContaining({
+					modelOptions: { "copilot-integration-id": "roo-code" },
+				}),
+				expect.anything(),
+			)
+		})
+
+		it("should NOT include modelOptions when model vendor is not copilot", async () => {
+			const systemPrompt = "You are a helpful assistant"
+			const messages: Anthropic.Messages.MessageParam[] = [{ role: "user" as const, content: "Hello" }]
+
+			mockLanguageModelChat.sendRequest.mockResolvedValueOnce({
+				stream: (async function* () {
+					yield new vscode.LanguageModelTextPart("Hi there")
+				})(),
+			})
+			mockLanguageModelChat.countTokens.mockResolvedValue(5)
+
+			const stream = handler.createMessage(systemPrompt, messages)
+			const chunks = []
+			for await (const chunk of stream) {
+				chunks.push(chunk)
+			}
+
+			// sendRequest should have been called without modelOptions
+			const callArgs = mockLanguageModelChat.sendRequest.mock.calls[0]
+			const requestOptions = callArgs[1]
+			expect(requestOptions.modelOptions).toBeUndefined()
+		})
 	})
 
 	describe("getModel", () => {
@@ -535,5 +592,53 @@ describe("VsCodeLmHandler", () => {
 			const promise = handler.completePrompt("Test prompt")
 			await expect(promise).rejects.toThrow("VSCode LM completion error: Completion failed")
 		})
+
+		it("should include modelOptions in completePrompt when model vendor is copilot", async () => {
+			const copilotModel = {
+				...mockLanguageModelChat,
+				vendor: "copilot",
+				name: "GPT-4o",
+				sendRequest: vi.fn(),
+				countTokens: vi.fn(),
+			}
+			handler["client"] = copilotModel as any
+
+			const responseText = "Completed text"
+			copilotModel.sendRequest.mockResolvedValueOnce({
+				stream: (async function* () {
+					yield new vscode.LanguageModelTextPart(responseText)
+					return
+				})(),
+			})
+
+			const result = await handler.completePrompt("Test prompt")
+			expect(result).toBe(responseText)
+			expect(copilotModel.sendRequest).toHaveBeenCalledWith(
+				expect.any(Array),
+				expect.objectContaining({
+					modelOptions: { "copilot-integration-id": "roo-code" },
+				}),
+				expect.anything(),
+			)
+		})
+
+		it("should NOT include modelOptions in completePrompt when model vendor is not copilot", async () => {
+			handler["client"] = mockLanguageModelChat
+
+			const responseText = "Completed text"
+			mockLanguageModelChat.sendRequest.mockResolvedValueOnce({
+				stream: (async function* () {
+					yield new vscode.LanguageModelTextPart(responseText)
+					return
+				})(),
+			})
+
+			const result = await handler.completePrompt("Test prompt")
+			expect(result).toBe(responseText)
+
+			const callArgs = mockLanguageModelChat.sendRequest.mock.calls[0]
+			const requestOptions = callArgs[1]
+			expect(requestOptions.modelOptions).toBeUndefined()
+		})
 	})
 })

src/api/providers/vscode-lm.ts

@@ -14,6 +14,40 @@ import { convertToVsCodeLmMessages, extractTextCountFromMessage } from "../trans
 import { BaseProvider } from "./base-provider"
 import type { SingleCompletionHandler, ApiHandlerCreateMessageMetadata } from "../index"
 
+/**
+ * The vendor string used by GitHub Copilot models in the VS Code LM API.
+ */
+const COPILOT_VENDOR = "copilot"
+
+/**
+ * Checks whether the given model client is backed by GitHub Copilot.
+ *
+ * @param client - A VS Code LanguageModelChat instance (may be null during init).
+ * @returns `true` when the model's vendor matches the Copilot vendor string.
+ */
+function isCopilotModel(client: vscode.LanguageModelChat | null): boolean {
+	return client?.vendor?.toLowerCase() === COPILOT_VENDOR
+}
+
+/**
+ * Builds model-specific options for GitHub Copilot requests.
+ *
+ * These options are forwarded by the VS Code Copilot Chat extension to the
+ * Copilot backend and help it properly categorise requests that originate
+ * from agent/extension activity (as opposed to direct user chat).
+ *
+ * Requires VS Code >= 1.96 where `modelOptions` on
+ * `LanguageModelChatRequestOptions` became stable.  On older versions the
+ * extra property is silently ignored.
+ *
+ * @see https://github.com/RooCodeInc/Roo-Code/issues/11289
+ */
+function buildCopilotModelOptions(): Record<string, unknown> {
+	return {
+		"copilot-integration-id": "roo-code",
+	}
+}
+
 /**
  * Converts OpenAI-format tools to VSCode Language Model tools.
  * Normalizes the JSON Schema to draft 2020-12 compliant format required by
@@ -393,11 +427,17 @@ export class VsCodeLmHandler extends BaseProvider implements SingleCompletionHan
 		let accumulatedText: string = ""
 
 		try {
-			// Create the response stream with required options
+			// Create the response stream with required options.
+			// When the model is backed by GitHub Copilot we attach
+			// modelOptions so that the Copilot backend can properly
+			// categorise agent-initiated requests for billing purposes.
+			// `modelOptions` requires VS Code >= 1.96; older versions
+			// silently ignore the extra property.
 			const requestOptions: vscode.LanguageModelChatRequestOptions = {
 				justification: `Roo Code would like to use '${client.name}' from '${client.vendor}', Click 'Allow' to proceed.`,
 				tools: convertToVsCodeLmTools(metadata?.tools ?? []),
-			}
+				...(isCopilotModel(client) ? { modelOptions: buildCopilotModelOptions() } : {}),
+			} as vscode.LanguageModelChatRequestOptions
 
 			const response: vscode.LanguageModelChatResponse = await client.sendRequest(
 				vsCodeLmMessages,
@@ -565,9 +605,12 @@ export class VsCodeLmHandler extends BaseProvider implements SingleCompletionHan
 	async completePrompt(prompt: string): Promise<string> {
 		try {
 			const client = await this.getClient()
+			const requestOptions = {
+				...(isCopilotModel(client) ? { modelOptions: buildCopilotModelOptions() } : {}),
+			} as vscode.LanguageModelChatRequestOptions
 			const response = await client.sendRequest(
 				[vscode.LanguageModelChatMessage.User(prompt)],
-				{},
+				requestOptions,
 				new vscode.CancellationTokenSource().token,
 			)
 			let result = ""