make copilot-fast callable from api (#1697)

* make copilot-fast callable from api

* Update src/platform/endpoint/common/modelAliasRegistry.ts

Co-authored-by: Copilot <[email protected]>

---------

Co-authored-by: Copilot <[email protected]>
Co-authored-by: Logan Ramos <[email protected]>

Author: 3 people

src/extension/conversation/vscode-node/languageModelAccess.ts

@@ -14,6 +14,7 @@ import { getTextPart } from '../../../platform/chat/common/globalStringUtils';
 import { EmbeddingType, getWellKnownEmbeddingTypeInfo, IEmbeddingsComputer } from '../../../platform/embeddings/common/embeddingsComputer';
 import { IEndpointProvider } from '../../../platform/endpoint/common/endpointProvider';
 import { CustomDataPartMimeTypes } from '../../../platform/endpoint/common/endpointTypes';
+import { ModelAliasRegistry } from '../../../platform/endpoint/common/modelAliasRegistry';
 import { encodeStatefulMarker } from '../../../platform/endpoint/common/statefulMarkerContainer';
 import { AutoChatEndpoint } from '../../../platform/endpoint/node/autoChatEndpoint';
 import { IAutomodeService } from '../../../platform/endpoint/node/automodeService';
@@ -201,6 +202,17 @@ export class LanguageModelAccess extends Disposable implements IExtensionContrib
 			};
 
 			models.push(model);
+
+			// Register aliases for this model
+			const aliases = ModelAliasRegistry.getAliases(model.id);
+			for (const alias of aliases) {
+				models.push({
+					...model,
+					id: alias,
+					family: alias,
+					isUserSelectable: false,
+				});
+			}
 		}
 
 		this._currentModels = models;
@@ -215,7 +227,7 @@ export class LanguageModelAccess extends Disposable implements IExtensionContrib
 		progress: vscode.Progress<vscode.LanguageModelResponsePart2>,
 		token: vscode.CancellationToken
 	): Promise<any> {
-		const endpoint = this._chatEndpoints.find(e => e.model === model.id);
+		const endpoint = this._chatEndpoints.find(e => e.model === ModelAliasRegistry.resolveAlias(model.id));
 		if (!endpoint) {
 			throw new Error(`Endpoint not found for model ${model.id}`);
 		}
@@ -231,7 +243,7 @@ export class LanguageModelAccess extends Disposable implements IExtensionContrib
 		text: string | vscode.LanguageModelChatMessage | vscode.LanguageModelChatMessage2,
 		token: vscode.CancellationToken
 	): Promise<number> {
-		const endpoint = this._chatEndpoints.find(e => e.model === model.id);
+		const endpoint = this._chatEndpoints.find(e => e.model === ModelAliasRegistry.resolveAlias(model.id));
 		if (!endpoint) {
 			throw new Error(`Endpoint not found for model ${model.id}`);
 		}

src/platform/endpoint/common/modelAliasRegistry.ts

@@ -0,0 +1,50 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+export class ModelAliasRegistry {
+	private readonly _aliasToModelId = new Map<string, string>();
+	private readonly _modelIdToAliases = new Map<string, string[]>();
+	private static readonly _instance = new ModelAliasRegistry();
+
+	private constructor() { }
+
+	private static _updateAliasesForModelId(modelId: string): void {
+		const aliases: string[] = [];
+		for (const [alias, mappedModelId] of this._instance._aliasToModelId.entries()) {
+			if (mappedModelId === modelId) {
+				aliases.push(alias);
+			}
+		}
+
+		if (aliases.length > 0) {
+			this._instance._modelIdToAliases.set(modelId, aliases);
+		} else {
+			this._instance._modelIdToAliases.delete(modelId);
+		}
+	}
+
+	static registerAlias(alias: string, modelId: string): void {
+		this._instance._aliasToModelId.set(alias, modelId);
+		this._updateAliasesForModelId(modelId);
+	}
+
+	static deregisterAlias(alias: string): void {
+		const modelId = this._instance._aliasToModelId.get(alias);
+		this._instance._aliasToModelId.delete(alias);
+		if (modelId) {
+			this._updateAliasesForModelId(modelId);
+		}
+	}
+
+	static resolveAlias(alias: string): string {
+		return this._instance._aliasToModelId.get(alias) ?? alias;
+	}
+
+	static getAliases(modelId: string): string[] {
+		return this._instance._modelIdToAliases.get(modelId) ?? [];
+	}
+}
+
+ModelAliasRegistry.registerAlias('copilot-fast', 'gpt-4o-mini');

src/platform/endpoint/node/modelMetadataFetcher.ts

@@ -22,6 +22,7 @@ import { IExperimentationService } from '../../telemetry/common/nullExperimentat
 import { ITelemetryService } from '../../telemetry/common/telemetry';
 import { ICAPIClientService } from '../common/capiClient';
 import { ChatEndpointFamily, IChatModelInformation, ICompletionModelInformation, IEmbeddingModelInformation, IModelAPIResponse, isChatModelInformation, isCompletionModelInformation, isEmbeddingModelInformation } from '../common/endpointProvider';
+import { ModelAliasRegistry } from '../common/modelAliasRegistry';
 import { getMaxPromptTokens } from './chatEndpoint';
 
 export interface IModelMetadataFetcher {
@@ -159,10 +160,10 @@ export class ModelMetadataFetcher extends Disposable implements IModelMetadataFe
 	public async getChatModelFromFamily(family: ChatEndpointFamily): Promise<IChatModelInformation> {
 		await this._taskSingler.getOrCreate(ModelMetadataFetcher.ALL_MODEL_KEY, this._fetchModels.bind(this));
 		let resolvedModel: IModelAPIResponse | undefined;
+		family = ModelAliasRegistry.resolveAlias(family) as ChatEndpointFamily;
+
 		if (family === 'gpt-4.1') {
 			resolvedModel = this._familyMap.get('gpt-4.1')?.[0] ?? this._familyMap.get('gpt-4o')?.[0];
-		} else if (family === 'copilot-fast') {
-			resolvedModel = this._familyMap.get('gpt-4o-mini')?.[0];
 		} else if (family === 'copilot-base') {
 			resolvedModel = this._copilotBaseModel;
 		} else {