Model Selection
Choose and configure models for your Built-in Agent.
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#
| Model | Specifier |
|---|---|
| GPT-5 | openai:gpt-5 |
| GPT-5 Mini | openai:gpt-5-mini |
| GPT-4.1 | openai:gpt-4.1 |
| GPT-4.1 Mini | openai:gpt-4.1-mini |
| GPT-4.1 Nano | openai:gpt-4.1-nano |
| GPT-5.4 Mini | openai:gpt-5.4-mini |
| o3 | openai:o3 |
| o3-mini | openai:o3-mini |
| o4-mini | openai:o4-mini |
const agent = new BuiltInAgent({
model: "openai:gpt-4.1",
});
Anthropic#
| Model | Specifier |
|---|---|
| Claude Sonnet 4.5 | anthropic:claude-sonnet-4-5 |
| Claude Sonnet 4 | anthropic:claude-sonnet-4 |
| Claude 3.7 Sonnet | anthropic:claude-3-7-sonnet |
| Claude Opus 4.1 | anthropic:claude-opus-4-1 |
| Claude Opus 4 | anthropic:claude-opus-4 |
| Claude 3.5 Haiku | anthropic:claude-3-5-haiku |
const agent = new BuiltInAgent({
model: "anthropic:claude-sonnet-4-5",
});
Google#
| Model | Specifier |
|---|---|
| Gemini 2.5 Pro | google:gemini-2.5-pro |
| Gemini 2.5 Flash | google:gemini-2.5-flash |
| Gemini 2.5 Flash Lite | google:gemini-2.5-flash-lite |
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, // [!code highlight]
});
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"; // [!code highlight]
const customProvider = createOpenAI({ // [!code highlight]
apiKey: process.env.MY_API_KEY, // [!code highlight]
baseURL: "https://my-proxy.example.com/v1", // [!code highlight]
}); // [!code highlight]
const agent = new BuiltInAgent({
model: customProvider("my-fine-tuned-model"), // [!code highlight]
});
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.
The Custom Agent lets you bring your own AI SDK, TanStack AI, or any custom LLM backend — while CopilotKit handles the rest.