Use the SFT + RL CAPI proxy model to power the Search Subagent

package.json

@@ -4016,7 +4016,7 @@
 					},
 					"github.copilot.chat.searchSubagent.enabled": {
 						"type": "boolean",
-						"default": false,
+						"default": true,
 						"markdownDescription": "%github.copilot.config.searchSubagent.enabled%",
 						"tags": [
 							"advanced",

src/extension/prompt/node/searchSubagentToolCallingLoop.ts

@@ -9,6 +9,7 @@ import { IAuthenticationChatUpgradeService } from '../../../platform/authenticat
 import { ChatLocation, ChatResponse } from '../../../platform/chat/common/commonTypes';
 import { IConfigurationService } from '../../../platform/configuration/common/configurationService';
 import { IEndpointProvider } from '../../../platform/endpoint/common/endpointProvider';
+import { ProxyAgenticSearchEndpoint } from '../../../platform/endpoint/node/proxyAgenticSearchEndpoint';
 import { ILogService } from '../../../platform/log/common/logService';
 import { IRequestLogger } from '../../../platform/requestLogger/node/requestLogger';
 import { IExperimentationService } from '../../../platform/telemetry/common/nullExperimentationService';
@@ -38,7 +39,7 @@ export class SearchSubagentToolCallingLoop extends ToolCallingLoop<ISearchSubage
 		@IInstantiationService private readonly instantiationService: IInstantiationService,
 		@ILogService logService: ILogService,
 		@IRequestLogger requestLogger: IRequestLogger,
-		@IEndpointProvider private readonly endpointProvider: IEndpointProvider,
+		@IEndpointProvider endpointProvider: IEndpointProvider,
 		@IToolsService private readonly toolsService: IToolsService,
 		@IAuthenticationChatUpgradeService authenticationChatUpgradeService: IAuthenticationChatUpgradeService,
 		@ITelemetryService telemetryService: ITelemetryService,
@@ -61,16 +62,12 @@ export class SearchSubagentToolCallingLoop extends ToolCallingLoop<ISearchSubage
 		return context;
 	}
 
-	private async getEndpoint(request: ChatRequest) {
-		let endpoint = await this.endpointProvider.getChatEndpoint(this.options.request);
-		if (!endpoint.supportsToolCalls) {
-			endpoint = await this.endpointProvider.getChatEndpoint('gpt-4.1');
-		}
-		return endpoint;
+	private async getEndpoint() {
+		return this.instantiationService.createInstance(ProxyAgenticSearchEndpoint);
 	}
 
 	protected async buildPrompt(buildPromptContext: IBuildPromptContext, progress: Progress<ChatResponseReferencePart | ChatResponseProgressPart>, token: CancellationToken): Promise<IBuildPromptResult> {
-		const endpoint = await this.getEndpoint(this.options.request);
+		const endpoint = await this.getEndpoint();
 		const renderer = PromptRenderer.create(
 			this.instantiationService,
 			endpoint,
@@ -83,7 +80,7 @@ export class SearchSubagentToolCallingLoop extends ToolCallingLoop<ISearchSubage
 	}
 
 	protected async getAvailableTools(): Promise<LanguageModelToolInformation[]> {
-		const endpoint = await this.getEndpoint(this.options.request);
+		const endpoint = await this.getEndpoint();
 		const allTools = this.toolsService.getEnabledTools(this.options.request, endpoint);
 
 		// Only include tools relevant for search operations.
@@ -100,7 +97,7 @@ export class SearchSubagentToolCallingLoop extends ToolCallingLoop<ISearchSubage
 	}
 
 	protected async fetch({ messages, finishedCb, requestOptions }: ToolCallingLoopFetchOptions, token: CancellationToken): Promise<ChatResponse> {
-		const endpoint = await this.getEndpoint(this.options.request);
+		const endpoint = await this.getEndpoint();
 		return endpoint.makeChatRequest2({
 			debugName: SearchSubagentToolCallingLoop.ID,
 			messages,

src/platform/configuration/common/configurationService.ts

@@ -689,7 +689,7 @@ export namespace ConfigKey {
 		export const PromptFileContext = defineAndMigrateExpSetting<boolean>('chat.advanced.promptFileContextProvider.enabled', 'chat.promptFileContextProvider.enabled', true);
 		export const DefaultToolsGrouped = defineAndMigrateExpSetting<boolean>('chat.advanced.tools.defaultToolsGrouped', 'chat.tools.defaultToolsGrouped', false);
 		export const Gpt5AlternativePatch = defineAndMigrateExpSetting<boolean>('chat.advanced.gpt5AlternativePatch', 'chat.gpt5AlternativePatch', false);
-		export const SearchSubagentToolEnabled = defineSetting<boolean>('chat.searchSubagent.enabled', ConfigType.ExperimentBased, false);
+		export const SearchSubagentToolEnabled = defineSetting<boolean>('chat.searchSubagent.enabled', ConfigType.ExperimentBased, true);
 		export const InlineEditsTriggerOnEditorChangeAfterSeconds = defineAndMigrateExpSetting<number | undefined>('chat.advanced.inlineEdits.triggerOnEditorChangeAfterSeconds', 'chat.inlineEdits.triggerOnEditorChangeAfterSeconds', undefined);
 		export const InlineEditsNextCursorPredictionDisplayLine = defineAndMigrateExpSetting<boolean>('chat.advanced.inlineEdits.nextCursorPrediction.displayLine', 'chat.inlineEdits.nextCursorPrediction.displayLine', true);
 		export const InlineEditsNextCursorPredictionCurrentFileMaxTokens = defineAndMigrateExpSetting<number>('chat.advanced.inlineEdits.nextCursorPrediction.currentFileMaxTokens', 'chat.inlineEdits.nextCursorPrediction.currentFileMaxTokens', xtabPromptOptions.DEFAULT_OPTIONS.currentFile.maxTokens);

src/platform/endpoint/node/proxyAgenticSearchEndpoint.ts

@@ -0,0 +1,75 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+import { RequestType } from '@vscode/copilot-api';
+import { TokenizerType } from '../../../util/common/tokenizer';
+import { IInstantiationService } from '../../../util/vs/platform/instantiation/common/instantiation';
+import { IAuthenticationService } from '../../authentication/common/authentication';
+import { IChatMLFetcher } from '../../chat/common/chatMLFetcher';
+import { IConfigurationService } from '../../configuration/common/configurationService';
+import { ILogService } from '../../log/common/logService';
+import { IFetcherService } from '../../networking/common/fetcherService';
+import { IExperimentationService } from '../../telemetry/common/nullExperimentationService';
+import { ITelemetryService } from '../../telemetry/common/telemetry';
+import { ITokenizerProvider } from '../../tokenizer/node/tokenizer';
+import { ICAPIClientService } from '../common/capiClient';
+import { IDomainService } from '../common/domainService';
+import { IChatModelInformation } from '../common/endpointProvider';
+import { ChatEndpoint } from './chatEndpoint';
+
+export class ProxyAgenticSearchEndpoint extends ChatEndpoint {
+
+	constructor(
+		@IDomainService domainService: IDomainService,
+		@ICAPIClientService capiClientService: ICAPIClientService,
+		@IFetcherService fetcherService: IFetcherService,
+		@ITelemetryService telemetryService: ITelemetryService,
+		@IAuthenticationService authService: IAuthenticationService,
+		@IChatMLFetcher chatMLFetcher: IChatMLFetcher,
+		@ITokenizerProvider tokenizerProvider: ITokenizerProvider,
+		@IInstantiationService instantiationService: IInstantiationService,
+		@IConfigurationService configurationService: IConfigurationService,
+		@IExperimentationService experimentationService: IExperimentationService,
+		@ILogService logService: ILogService,
+	) {
+		const model = 'agentic-search-v1';
+		const modelInfo: IChatModelInformation = {
+			id: model,
+			name: model,
+			version: 'unknown',
+			model_picker_enabled: false,
+			is_chat_default: false,
+			is_chat_fallback: false,
+			capabilities: {
+				type: 'chat',
+				family: model,
+				tokenizer: TokenizerType.O200K,
+				supports: { streaming: true, parallel_tool_calls: true, tool_calls: true, vision: false },
+				limits: {
+					max_prompt_tokens: 128000,
+					max_output_tokens: 16000,
+				}
+			}
+		};
+		super(
+			modelInfo,
+			domainService,
+			capiClientService,
+			fetcherService,
+			telemetryService,
+			authService,
+			chatMLFetcher,
+			tokenizerProvider,
+			instantiationService,
+			configurationService,
+			experimentationService,
+			logService
+		);
+	}
+
+	override get urlOrRequestMetadata() {
+		return { type: RequestType.ProxyChatCompletions };
+	}
+}