vercel/ai · error · Error

The Anthropic model function cannot be called with the new k

Error message

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

What it means

Error "The Anthropic model function cannot be called with the new keyword." thrown in vercel/ai.

Source

Thrown at packages/google-vertex/src/anthropic/google-vertex-anthropic-provider.ts:235

      transformRequestBody: args => {
        // Remove model from args and add anthropic version
        const { model: _model, ...rest } = args;
        return {
          ...rest,
          anthropic_version: 'vertex-2023-10-16',
        };
      },
      // Google Vertex Anthropic doesn't support URL sources, force download and base64 conversion
      supportedUrls: () => ({}),
      // force the use of JSON tool fallback for structured outputs since beta header isn't supported
      supportsNativeStructuredOutput: false,
      // Vertex Anthropic doesn't support strict mode on tool definitions.
      supportsStrictTools: false,
    });

  const provider = function (modelId: GoogleVertexAnthropicModelId) {
    if (new.target) {
      throw new Error(
        'The Anthropic 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)

When it happens

Trigger: Thrown at packages/google-vertex/src/anthropic/google-vertex-anthropic-provider.ts:235 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of vercel/ai@69428b1f8b (2026-08-30). Data as JSON: /api/errors/9b01fb2ede7a1d48. Report an issue: GitHub.