feat(ai-anthropic): support GCP Vertex for the antrophic adapter

.changeset/anthropic-client-injection.md

@@ -0,0 +1,6 @@
+---
+'@tanstack/ai-anthropic': minor
+---
+
+Add a client-injection factory for Anthropic-compatible clients with custom
+authentication and transport.

README.md

@@ -188,7 +188,7 @@ Official adapters include:
 | ------------------------------------------------------------------------------------ | ------------------------------------------------------------------------------ |
 | [`@tanstack/ai-openrouter`](https://tanstack.com/ai/latest/docs/adapters/openrouter) | 300+ models through one OpenRouter API, with per-request cost tracking         |
 | [`@tanstack/ai-openai`](https://tanstack.com/ai/latest/docs/adapters/openai)         | OpenAI chat, image, video, speech, transcription, realtime, and provider tools |
-| [`@tanstack/ai-anthropic`](https://tanstack.com/ai/latest/docs/adapters/anthropic)   | Anthropic Claude chat, thinking, tools, and structured outputs                 |
+| [`@tanstack/ai-anthropic`](https://tanstack.com/ai/latest/docs/adapters/anthropic)   | Anthropic Claude chat, thinking, tools, structured outputs, and custom clients |
 | [`@tanstack/ai-gemini`](https://tanstack.com/ai/latest/docs/adapters/gemini)         | Google Gemini chat, image, speech, and audio generation                        |
 | [`@tanstack/ai-ollama`](https://tanstack.com/ai/latest/docs/adapters/ollama)         | Local Ollama models                                                            |
 | [`@tanstack/ai-grok`](https://tanstack.com/ai/latest/docs/adapters/grok)             | xAI Grok chat, images, and realtime                                            |

docs/adapters/anthropic.md

@@ -61,7 +61,46 @@ const config: Omit<AnthropicTextConfig, "apiKey"> = {
 
 const adapter = createAnthropicChat("claude-sonnet-4-6", process.env.ANTHROPIC_API_KEY!, config);
 ```
-
+
+## Custom Anthropic Client
+
+Use `createAnthropicChatWithClient` when authentication or transport is
+provided by an Anthropic-compatible client. The adapter only requires the
+client's `beta.messages.create` capability; message mapping, streaming, tools,
+media, usage, and structured output still follow the same TanStack adapter
+path.
+
+For example, Anthropic's Vertex client can discover Google Cloud credentials
+through Application Default Credentials:
+
+```bash
+npm install @tanstack/ai-anthropic @anthropic-ai/vertex-sdk
+```
+
+```typescript
+import { AnthropicVertex } from "@anthropic-ai/vertex-sdk";
+import {
+  createAnthropicChatWithClient,
+  type AnthropicMessagesClient,
+} from "@tanstack/ai-anthropic";
+
+const projectId = process.env.GOOGLE_CLOUD_PROJECT;
+
+if (!projectId) {
+  throw new Error("GOOGLE_CLOUD_PROJECT is required");
+}
+
+const client = new AnthropicVertex({
+  projectId,
+  region: "eu",
+}) satisfies AnthropicMessagesClient;
+
+const adapter = createAnthropicChatWithClient("claude-sonnet-5", client);
+```
+
+The injected client must implement the Anthropic Beta Messages protocol.
+Endpoint-specific model and feature support remains the caller's
+responsibility.
 
 ## Example: Chat Completion
 
@@ -257,7 +296,7 @@ ANTHROPIC_API_KEY=sk-ant-...
 
 ## API Reference
 
-Every factory pair follows the same shape: the short factory (`anthropicText`, `anthropicSummarize`) reads `ANTHROPIC_API_KEY` from the environment, while `createAnthropicChat` / `createAnthropicSummarize` take an explicit API key. Both take `model` as the first argument.
+Every factory pair follows the same shape: the short factory (`anthropicText`, `anthropicSummarize`) reads `ANTHROPIC_API_KEY` from the environment, while `createAnthropicChat` / `createAnthropicSummarize` take an explicit API key. Both take `model` as the first argument. For custom authentication or transport, `createAnthropicChatWithClient` accepts an Anthropic-compatible Messages client instead.
 
 ### `anthropicText(model, config?)` / `createAnthropicChat(model, apiKey, config?)`
 
@@ -268,6 +307,15 @@ Creates an Anthropic chat adapter.
 - `model` - Claude model id (e.g. `"claude-sonnet-5"`, `"claude-fable-5"`, `"claude-opus-4-8"`)
 - `config?.baseURL` - Custom base URL (optional)
 
+### `createAnthropicChatWithClient(model, client)`
+
+Creates an Anthropic chat adapter using an injected client.
+
+**Parameters:**
+
+- `model` - Claude model id
+- `client` - Client exposing `beta.messages.create`
+
 ### `anthropicSummarize(model, config?)` / `createAnthropicSummarize(model, apiKey, config?)`
 
 Creates an Anthropic summarization adapter.

docs/config.json

@@ -640,7 +640,7 @@
           "label": "Anthropic",
           "to": "adapters/anthropic",
           "addedAt": "2026-04-15",
-          "updatedAt": "2026-07-04"
+          "updatedAt": "2026-07-23"
         },
         {
           "label": "Google Gemini",

packages/ai-anthropic/package.json

@@ -66,6 +66,8 @@
     "zod": "^4.0.0"
   },
   "devDependencies": {
+    "@anthropic-ai/sdk-v112": "npm:@anthropic-ai/sdk@0.112.4",
+    "@anthropic-ai/vertex-sdk": "^0.19.0",
     "@tanstack/ai": "workspace:*",
     "@vitest/coverage-v8": "4.0.14",
     "zod": "^4.2.0"

packages/ai-anthropic/src/adapters/text.ts

@@ -64,7 +64,10 @@ import type {
   AnthropicMessageMetadataByModality,
   AnthropicTextMetadata,
 } from '../message-types'
-import type { AnthropicClientConfig } from '../utils/client'
+import type {
+  AnthropicClientConfig,
+  AnthropicMessagesClient,
+} from '../utils/client'
 
 /**
  * The block type carried by an Anthropic provider-executed (server) tool's
@@ -202,6 +205,10 @@ export function computeAnthropicBetas(
  */
 export interface AnthropicTextConfig extends AnthropicClientConfig {}
 
+export type AnthropicTextAdapterConfig =
+  | AnthropicTextConfig
+  | { client: AnthropicMessagesClient }
+
 /**
  * Anthropic-specific provider options for text/chat
  */
@@ -234,6 +241,24 @@ type ResolveToolCapabilities<TModel extends string> =
     ? NonNullable<AnthropicChatModelToolCapabilitiesByName[TModel]>
     : readonly []
 
+type SdkAnthropicMessagesClient = {
+  beta: {
+    messages: Pick<Anthropic_SDK['beta']['messages'], 'create'>
+  }
+}
+
+/**
+ * Restore the package SDK's precise overloads at the adapter boundary.
+ * Alternative clients may use a separate Anthropic 0.x SDK whose declarations
+ * drift while implementing the same Messages protocol at runtime.
+ */
+function asSdkAnthropicMessagesClient(
+  client: AnthropicMessagesClient,
+): SdkAnthropicMessagesClient {
+  // oxlint-disable-next-line eslint-js/no-restricted-syntax -- The public callable deliberately erases version-specific SDK overloads; restore this package's SDK type at the internal boundary.
+  return client as unknown as SdkAnthropicMessagesClient
+}
+
 // ===========================
 // Adapter Implementation
 // ===========================
@@ -266,11 +291,14 @@ export class AnthropicTextAdapter<
   override readonly kind = 'text' as const
   readonly name = 'anthropic' as const
 
-  private readonly client: Anthropic_SDK
+  private readonly client: SdkAnthropicMessagesClient
 
-  constructor(config: AnthropicTextConfig, model: TModel) {
+  constructor(config: AnthropicTextAdapterConfig, model: TModel) {
     super({}, model)
-    this.client = createAnthropicClient(config)
+    this.client =
+      'client' in config
+        ? asSdkAnthropicMessagesClient(config.client)
+        : createAnthropicClient(config)
   }
 
   async *chatStream(
@@ -1468,6 +1496,23 @@ export function createAnthropicChat<
   return new AnthropicTextAdapter({ apiKey, ...config }, model)
 }
 
+/**
+ * Creates an Anthropic chat adapter with an injected Messages client.
+ * Type resolution happens here at the call site.
+ */
+export function createAnthropicChatWithClient<
+  TModel extends (typeof ANTHROPIC_MODELS)[number],
+>(
+  model: TModel,
+  client: AnthropicMessagesClient,
+): AnthropicTextAdapter<
+  TModel,
+  ResolveProviderOptions<TModel>,
+  ResolveInputModalities<TModel>
+> {
+  return new AnthropicTextAdapter({ client }, model)
+}
+
 /**
  * Creates an Anthropic text adapter with automatic API key detection.
  * Type resolution happens here at the call site.

packages/ai-anthropic/src/index.ts

@@ -7,9 +7,12 @@ export {
   AnthropicTextAdapter,
   anthropicText,
   createAnthropicChat,
+  createAnthropicChatWithClient,
+  type AnthropicTextAdapterConfig,
   type AnthropicTextConfig,
   type AnthropicTextProviderOptions,
 } from './adapters/text'
+export type { AnthropicMessagesClient } from './utils/client'
 export type { AnthropicSystemPromptMetadata } from './text/text-provider-options'
 
 // Summarize - thin factory functions over @tanstack/ai's ChatStreamSummarizeAdapter

packages/ai-anthropic/src/utils/client.ts

@@ -6,6 +6,27 @@ export interface AnthropicClientConfig extends ClientOptions {
   apiKey: string
 }
 
+type AnyAnthropicMessagesCreate = (
+  params: never,
+  ...args: Array<never>
+) => unknown
+
+/**
+ * The minimal Anthropic client surface used by the text adapter.
+ *
+ * The callable is intentionally type-erased because alternative Anthropic
+ * clients can depend on a different 0.x release of the Anthropic SDK. Their
+ * request and response declarations may drift even when the runtime Messages
+ * protocol remains compatible.
+ */
+export interface AnthropicMessagesClient {
+  readonly beta: {
+    readonly messages: {
+      readonly create: AnyAnthropicMessagesCreate
+    }
+  }
+}
+
 /**
  * Creates an Anthropic SDK client instance
  */

packages/ai-anthropic/tests/anthropic-adapter.test.ts

@@ -6,6 +6,7 @@ import {
   type StreamChunk,
   type UIMessage,
 } from '@tanstack/ai'
+import { createAnthropicChatWithClient } from '../src'
 import { AnthropicTextAdapter } from '../src/adapters/text'
 import type { AnthropicTextProviderOptions } from '../src/adapters/text'
 import { ANTHROPIC_MAX_NONSTREAMING_TOKENS } from '../src/model-meta'
@@ -77,6 +78,35 @@ function createTextStream(text: string) {
   })()
 }
 
+describe('Anthropic client injection', () => {
+  beforeEach(() => {
+    vi.clearAllMocks()
+  })
+
+  it('uses the injected messages client instead of constructing one', async () => {
+    const create = vi.fn().mockResolvedValueOnce(createTextStream('Hello'))
+    const client = {
+      beta: {
+        messages: {
+          create,
+        },
+      },
+    }
+
+    const adapter = createAnthropicChatWithClient('claude-opus-4-1', client)
+
+    for await (const _ of chat({
+      adapter,
+      messages: [{ role: 'user', content: 'Hi' }],
+    })) {
+      // consume stream
+    }
+
+    expect(create).toHaveBeenCalledOnce()
+    expect(mocks.betaMessagesCreate).not.toHaveBeenCalled()
+  })
+})
+
 describe('Anthropic adapter option mapping', () => {
   beforeEach(() => {
     vi.clearAllMocks()

packages/ai-anthropic/tests/client-injection-type-safety.test.ts

@@ -0,0 +1,18 @@
+import { expectTypeOf, it } from 'vitest'
+import type AnthropicSdkV112 from '@anthropic-ai/sdk-v112'
+import type { AnthropicVertex } from '@anthropic-ai/vertex-sdk'
+import type { AnthropicMessagesClient } from '../src'
+
+type V112MessagesClient = {
+  readonly beta: {
+    readonly messages: Pick<AnthropicSdkV112['beta']['messages'], 'create'>
+  }
+}
+
+it('accepts the official Vertex client', () => {
+  expectTypeOf<AnthropicVertex>().toExtend<AnthropicMessagesClient>()
+})
+
+it('accepts clients backed by a newer Anthropic SDK version', () => {
+  expectTypeOf<V112MessagesClient>().toExtend<AnthropicMessagesClient>()
+})

testing/e2e/package.json

@@ -12,6 +12,7 @@
     "postinstall": "playwright install chromium"
   },
   "dependencies": {
+    "@anthropic-ai/sdk": "^0.97.1",
     "@copilotkit/aimock": "^1.34.0",
     "@modelcontextprotocol/sdk": "^1.29.0",
     "@openrouter/sdk": "0.13.20",