First-class support for Anthropic-compatible LLM providers in TanStack AI

[thanhdaon]

Many LLM providers now offer Anthropic-compatible APIs, but TanStack AI's @tanstack/ai-anthropic adapter currently doesn't support custom base URLs. This limits developers from using cost-effective alternatives or specialized models that follow the Anthropic API standard.

Proposed Solution

Add baseURL support to the AnthropicConfig interface, similar to how the OpenAI adapter works:

  import { anthropic } from '@tanstack/ai-anthropic';
  import { chat } from '@tanstack/ai';

  // Current limitation - this doesn't work
  const adapter = anthropic({
    apiKey: process.env.GLM_API_KEY,
    baseURL: 'https://open.bigmodel.cn/api/paas/v4', // ❌ Not supported
  });

  // Proposed solution
  const adapter = anthropic({
    apiKey: process.env.GLM_API_KEY,
    baseURL: 'https://open.bigmodel.cn/api/paas/v4', // ✅ Should work
  });

  const stream = chat({
    adapter,
    model: 'glm-4.6',
    messages: [{ role: 'user', content: 'Hello!' }],
  });