Model Selection

The Built-in Agent uses the Vercel AI SDK under the hood, giving you access to models from OpenAI, Anthropic, and Google — plus the ability to use any custom AI SDK model.

Supported Models#

Specify a model using the "provider:model" format (or "provider/model" — both work).

OpenAI#

const agent = new BuiltInAgent({
  model: "openai:gpt-4.1",
});

Anthropic#

const agent = new BuiltInAgent({
  model: "anthropic:claude-sonnet-4-5",
});

Google#

const agent = new BuiltInAgent({
  model: "google:gemini-2.5-pro",
});

Environment Variables#

Set the API key for your chosen provider:

# OpenAI
OPENAI_API_KEY=sk-...

# Anthropic
ANTHROPIC_API_KEY=sk-ant-...

# Google
GOOGLE_API_KEY=...

Alternatively, pass the API key directly in your configuration:

const agent = new BuiltInAgent({
  model: "openai:gpt-4.1",
  apiKey: process.env.MY_OPENAI_KEY, 
});

Custom Models (AI SDK)#

For models not in the built-in list, you can pass any Vercel AI SDK LanguageModel instance directly:

import { BuiltInAgent } from "@copilotkit/runtime/v2";
import { createOpenAI } from "@ai-sdk/openai"; 

const customProvider = createOpenAI({ 
  apiKey: process.env.MY_API_KEY, 
  baseURL: "https://my-proxy.example.com/v1", 
}); 

const agent = new BuiltInAgent({
  model: customProvider("my-fine-tuned-model"), 
});

This works with any AI SDK provider — Azure OpenAI, AWS Bedrock, Ollama, or any OpenAI-compatible endpoint:

import { createAzure } from "@ai-sdk/azure";

const azure = createAzure({
  resourceName: "my-resource",
  apiKey: process.env.AZURE_API_KEY,
});

const agent = new BuiltInAgent({
  model: azure("my-deployment"),
});

How It Works#

Under the hood, the Built-in Agent resolves model strings to AI SDK provider instances:

• "openai:gpt-4.1" → @ai-sdk/openai → openai("gpt-4.1")
• "anthropic:claude-sonnet-4-5" → @ai-sdk/anthropic → anthropic("claude-sonnet-4-5")
• "google:gemini-2.5-pro" → @ai-sdk/google → google("gemini-2.5-pro")

Both "provider:model" and "provider/model" separators are supported and work identically.