Built In Agent Model Identifiers - Copilotkit

BuiltInAgent model identifiers — the full set of "provider/model" strings that resolveModel accepts out of the box.

Shape

"provider/model" or "provider:model" — both separators are normalized. Case-insensitive on the provider segment.

typescript

new BuiltInAgent({ model: "openai/gpt-4o" });
new BuiltInAgent({ model: "anthropic:claude-sonnet-4.5" });

Supported providers

Provider	Env var	Notes
`openai`	`OPENAI_API_KEY`	Lazily creates `@ai-sdk/openai`
`anthropic`	`ANTHROPIC_API_KEY`	Lazily creates `@ai-sdk/anthropic`
`google` / `gemini` / `google-gemini`	`GOOGLE_API_KEY`	`@ai-sdk/google` under the hood
`vertex`	(GCP auth)	`@ai-sdk/google-vertex`

Pass apiKey on the constructor to override env vars.

Pinned identifiers in the union type

These are the concrete strings typed in BuiltInAgentModel:

openai/gpt-5            openai/gpt-5-mini
openai/gpt-4.1          openai/gpt-4.1-mini        openai/gpt-4.1-nano
openai/gpt-4o           openai/gpt-4o-mini
openai/o3               openai/o3-mini             openai/o4-mini

anthropic/claude-sonnet-4.5   anthropic/claude-sonnet-4
anthropic/claude-3.7-sonnet   anthropic/claude-opus-4.1
anthropic/claude-opus-4       anthropic/claude-3.5-haiku

google/gemini-2.5-pro   google/gemini-2.5-flash    google/gemini-2.5-flash-lite

Any other valid model id is still accepted — the type is BuiltInAgentModel = "openai/gpt-5" | ... | (string & {}), and the AI SDK provider will accept any id it knows about. The pinned union is for autocomplete, not an exhaustive allowlist.

Passing a LanguageModel instance directly

Instead of a string, pass a pre-configured LanguageModel:

typescript

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

const openai = createOpenAI({ apiKey: process.env.OPENAI_API_KEY });
new BuiltInAgent({ model: openai("gpt-4o") });

This bypasses resolveModel entirely.

Source: packages/runtime/src/agent/index.ts:82-109, 176-249.