feat(vertex-anthropic): add support for custom Vertex AI Anthropic model

.changeset/vertex-anthropic-provider.md

@@ -0,0 +1,5 @@
+---
+'task-master-ai': minor
+---
+
+Add support for Vertex AI Anthropic provider to use Claude models through Google Vertex AI

apps/cli/src/commands/models/custom-providers.ts

@@ -125,6 +125,27 @@ export const customProviderConfigs: Record<
 			return true;
 		}
 	},
+	VERTEX_ANTHROPIC: {
+		id: '__CUSTOM_VERTEX_ANTHROPIC__',
+		name: '* Custom Vertex Anthropic model',
+		provider: CUSTOM_PROVIDERS.VERTEX_ANTHROPIC,
+		promptMessage: (role) =>
+			`Enter the custom Vertex AI Anthropic Model ID for the ${role} role (e.g., claude-sonnet-4-6):`,
+		checkEnvVars: () => {
+			if (
+				!process.env.GOOGLE_API_KEY &&
+				!process.env.GOOGLE_APPLICATION_CREDENTIALS
+			) {
+				console.error(
+					chalk.red(
+						'Error: Either GOOGLE_API_KEY or GOOGLE_APPLICATION_CREDENTIALS environment variable is required. Please set one before using Vertex Anthropic models.'
+					)
+				);
+				return false;
+			}
+			return true;
+		}
+	},
 	LMSTUDIO: {
 		id: '__CUSTOM_LMSTUDIO__',
 		name: '* Custom LMStudio model',

apps/cli/src/commands/models/types.ts

@@ -16,6 +16,7 @@ export const CUSTOM_PROVIDER_IDS = {
 	BEDROCK: '__CUSTOM_BEDROCK__',
 	AZURE: '__CUSTOM_AZURE__',
 	VERTEX: '__CUSTOM_VERTEX__',
+	VERTEX_ANTHROPIC: '__CUSTOM_VERTEX_ANTHROPIC__',
 	LMSTUDIO: '__CUSTOM_LMSTUDIO__',
 	OPENAI_COMPATIBLE: '__CUSTOM_OPENAI_COMPATIBLE__'
 } as const;

packages/tm-core/src/common/constants/providers.ts

@@ -26,6 +26,7 @@ export type ValidatedProvider = (typeof VALIDATED_PROVIDERS)[number];
 export const CUSTOM_PROVIDERS = {
 	AZURE: 'azure',
 	VERTEX: 'vertex',
+	VERTEX_ANTHROPIC: 'vertex-anthropic',
 	BEDROCK: 'bedrock',
 	OPENROUTER: 'openrouter',
 	OLLAMA: 'ollama',

scripts/modules/ai-services-unified.js

@@ -51,6 +51,7 @@ import {
 	OpenRouterAIProvider,
 	PerplexityAIProvider,
 	VertexAIProvider,
+	VertexAnthropicProvider,
 	XAIProvider,
 	ZAICodingProvider,
 	ZAIProvider
@@ -81,6 +82,7 @@ const PROVIDERS = {
 	bedrock: new BedrockAIProvider(),
 	azure: new AzureProvider(),
 	vertex: new VertexAIProvider(),
+	'vertex-anthropic': new VertexAnthropicProvider(),
 	'claude-code': new ClaudeCodeProvider(),
 	'codex-cli': new CodexCliProvider(),
 	'gemini-cli': new GeminiCliProvider(),
@@ -627,8 +629,11 @@ async function _unifiedServiceRunner(serviceType, params) {
 			// Prepare provider-specific configuration
 			let providerSpecificParams = {};
 
-			// Handle Vertex AI specific configuration
-			if (providerName?.toLowerCase() === 'vertex') {
+			// Handle Vertex AI specific configuration (both vertex and vertex-anthropic)
+			if (
+				providerName?.toLowerCase() === 'vertex' ||
+				providerName?.toLowerCase() === 'vertex-anthropic'
+			) {
 				providerSpecificParams = _getVertexConfiguration(
 					effectiveProjectRoot,
 					session

scripts/modules/task-manager/models.js

@@ -583,6 +583,11 @@ async function setModel(role, modelId, options = {}) {
 					determinedProvider = CUSTOM_PROVIDERS.VERTEX;
 					warningMessage = `Warning: Custom Vertex AI model '${modelId}' set. Please ensure the model is valid and accessible in your Google Cloud project.`;
 					report('warn', warningMessage);
+				} else if (providerHint === CUSTOM_PROVIDERS.VERTEX_ANTHROPIC) {
+					// Set provider without model validation since Vertex Anthropic models are managed by Google Cloud
+					determinedProvider = CUSTOM_PROVIDERS.VERTEX_ANTHROPIC;
+					warningMessage = `Warning: Custom Vertex AI Anthropic model '${modelId}' set. Please ensure the model is valid and accessible in your Google Cloud project.`;
+					report('warn', warningMessage);
 				} else if (providerHint === CUSTOM_PROVIDERS.GEMINI_CLI) {
 					// Gemini CLI provider - check if model exists in our list
 					determinedProvider = CUSTOM_PROVIDERS.GEMINI_CLI;
@@ -693,7 +698,7 @@ async function setModel(role, modelId, options = {}) {
 					success: false,
 					error: {
 						code: 'MODEL_NOT_FOUND_NO_HINT',
-						message: `Model ID "${modelId}" not found in Taskmaster's supported models. If this is a custom model, please specify the provider using --openrouter, --ollama, --bedrock, --azure, --vertex, --lmstudio, --openai-compatible, --gemini-cli, or --codex-cli.`
+						message: `Model ID "${modelId}" not found in Taskmaster's supported models. If this is a custom model, please specify the provider using --openrouter, --ollama, --bedrock, --azure, --vertex, --vertex-anthropic, --lmstudio, --openai-compatible, --gemini-cli, or --codex-cli.`
 					}
 				};
 			}

src/ai-providers/google-vertex-anthropic.js

@@ -0,0 +1,59 @@
+/**
+ * google-vertex-anthropic.js
+ * AI provider implementation for Anthropic models on Google Vertex AI using Vercel AI SDK.
+ * This provider uses the createVertexAnthropic client to route requests to the
+ * publishers/anthropic endpoint instead of publishers/google.
+ *
+ * Extends VertexAIProvider — only the client factory and display name differ.
+ */
+
+import { createVertexAnthropic } from '@ai-sdk/google-vertex/anthropic';
+import { VertexAIProvider } from './google-vertex.js';
+
+export class VertexAnthropicProvider extends VertexAIProvider {
+	constructor() {
+		super();
+		this.name = 'Google Vertex AI (Anthropic)';
+	}
+
+	/**
+	 * Creates and returns a Google Vertex AI Anthropic client instance.
+	 * Uses createVertexAnthropic to route to the publishers/anthropic endpoint.
+	 * @param {object} params - Parameters for client initialization
+	 * @param {string} [params.apiKey] - Google API key
+	 * @param {string} params.projectId - Google Cloud project ID
+	 * @param {string} params.location - Google Cloud location (e.g., "us-central1")
+	 * @param {object} [params.credentials] - Service account credentials object
+	 * @param {string} [params.baseURL] - Optional custom API endpoint
+	 * @returns {Function} Google Vertex AI Anthropic client function
+	 * @throws {Error} If required parameters are missing or initialization fails
+	 */
+	getClient(params) {
+		try {
+			const { apiKey, projectId, location, credentials, baseURL } = params;
+			const fetchImpl = this.createProxyFetch();
+
+			// Configure auth options - either API key or service account
+			const authOptions = {};
+			if (apiKey) {
+				authOptions.googleAuthOptions = {
+					...credentials,
+					apiKey
+				};
+			} else if (credentials) {
+				authOptions.googleAuthOptions = credentials;
+			}
+
+			// Return Vertex AI Anthropic client (publishers/anthropic endpoint)
+			return createVertexAnthropic({
+				...authOptions,
+				project: projectId,
+				location,
+				...(baseURL && { baseURL }),
+				...(fetchImpl && { fetch: fetchImpl })
+			});
+		} catch (error) {
+			this.handleError('client initialization', error);
+		}
+	}
+}

src/ai-providers/google-vertex.js

@@ -4,7 +4,6 @@
  */
 
 import { createVertex } from '@ai-sdk/google-vertex';
-import { resolveEnvVariable } from '../../scripts/modules/utils.js';
 import { log } from '../../scripts/modules/utils.js';
 import { BaseAIProvider } from './base-provider.js';
 

src/ai-providers/index.js

@@ -14,6 +14,7 @@ export { OllamaAIProvider } from './ollama.js';
 export { BedrockAIProvider } from './bedrock.js';
 export { AzureProvider } from './azure.js';
 export { VertexAIProvider } from './google-vertex.js';
+export { VertexAnthropicProvider } from './google-vertex-anthropic.js';
 export { ClaudeCodeProvider } from './claude-code.js';
 export { GeminiCliProvider } from './gemini-cli.js';
 export { GrokCliProvider } from './grok-cli.js';

tests/unit/ai-services-unified.test.js

@@ -231,6 +231,13 @@ jest.unstable_mockModule('../../src/ai-providers/index.js', () => ({
 		getRequiredApiKeyName: jest.fn(() => null),
 		isRequiredApiKey: jest.fn(() => false)
 	})),
+	VertexAnthropicProvider: jest.fn(() => ({
+		generateText: jest.fn(),
+		streamText: jest.fn(),
+		generateObject: jest.fn(),
+		getRequiredApiKeyName: jest.fn(() => null),
+		isRequiredApiKey: jest.fn(() => false)
+	})),
 	ClaudeCodeProvider: jest.fn(() => mockClaudeProvider),
 	GeminiCliProvider: jest.fn(() => ({
 		generateText: jest.fn(),

tests/unit/scripts/modules/task-manager/models-baseurl.test.js

@@ -54,6 +54,7 @@ jest.unstable_mockModule('@tm/core', () => ({
 		CLAUDE_CODE: 'claude-code',
 		AZURE: 'azure',
 		VERTEX: 'vertex',
+		VERTEX_ANTHROPIC: 'vertex-anthropic',
 		GEMINI_CLI: 'gemini-cli',
 		CODEX_CLI: 'codex-cli',
 		OPENAI_COMPATIBLE: 'openai-compatible'