The Anthropic AWS model function cannot be called with the n

Error message

The Anthropic AWS model function cannot be called with the new keyword.

What it means

The Anthropic AWS provider returned by `createAnthropicAws()` is a factory function, not a constructor. Calling it with `new` is detected via `new.target` and rejected with this error so users get a clear message instead of a silently broken model object.

Source

Thrown at packages/anthropic-aws/src/anthropic-aws-provider.ts:245

    ...options.headers,
  });

  const createChatModel = (modelId: AnthropicModelId) =>
    new AnthropicLanguageModel(modelId, {
      provider: 'anthropic-aws.messages',
      baseURL: getBaseURL(),
      headers: getHeaders,
      fetch: fetchFunction,
      generateId: options.generateId,
      supportedUrls: () => ({
        'image/*': [/^https?:\/\/.*$/],
        'application/pdf': [/^https?:\/\/.*$/],
      }),
    });

  const provider = function (modelId: AnthropicModelId) {
    if (new.target) {
      throw new Error(
        'The Anthropic AWS model function cannot be called with the new keyword.',
      );
    }
    return createChatModel(modelId);
  };

  provider.specificationVersion = 'v4' as const;
  provider.languageModel = createChatModel;
  provider.chat = createChatModel;
  provider.messages = createChatModel;

  provider.embeddingModel = (modelId: string) => {
    throw new NoSuchModelError({ modelId, modelType: 'embeddingModel' });
  };
  provider.textEmbeddingModel = provider.embeddingModel;
  provider.imageModel = (modelId: string) => {
    throw new NoSuchModelError({ modelId, modelType: 'imageModel' });
  };

View on GitHub (pinned to 69428b1f8b)

Solutions

Call the provider as a plain function: `anthropicAws('claude-sonnet-4-...')`.
Remove `new` wherever the provider is invoked, including inside helpers that construct models.
Consult current @ai-sdk/anthropic-aws docs for the factory-call pattern.

Example fix

// before
const model = new anthropicAws('claude-sonnet-4-20250514');
// after
const model = anthropicAws('claude-sonnet-4-20250514');

Defensive patterns

Strategy: validation

Validate before calling

if (typeof anthropicAws !== 'function') throw new Error('anthropicAws must be called as a function, not constructed');
const model = anthropicAws('claude-sonnet-4-20250514');

Type guard

function isProviderFactory(v: unknown): v is (modelId: string, settings?: unknown) => unknown {
  return typeof v === 'function' && !/^class\s/.test(String(v));
}

Try / catch

try {
  const model = anthropicAws('claude-sonnet-4-20250514');
} catch (e) {
  if (e instanceof Error && e.message.includes('cannot be called with the new keyword')) {
    // drop the `new` keyword at the call site
  }
  throw e;
}

Prevention

Never instantiate AI SDK providers with `new`.
Add a lint/grep rule against `new anthropicAws`.
Follow current provider docs instead of class-based examples.

When it happens

Trigger: Writing `new anthropicAws('claude-...')` or `new anthropic('model-id', {...})` with the AWS provider, typically copying old constructor-style provider code.

Common situations: Migrating from older SDKs where providers were classes; IDE auto-completing with `new`; LLM-generated boilerplate using `new` on provider factories.

Related errors

AI-assisted analysis of vercel/ai@69428b1f8b (2026-08-30). Data as JSON: /api/errors/0d91611515b471a7. Report an issue: GitHub.