Anthropic

The anthropic provider supports the Anthropic /v1/messages endpoint.

Basic Example

client<llm> MyClient {
    provider anthropic
    options {
        model "claude-sonnet-4-20250514"
        temperature 0
    }
}

BAML-Specific Options

Option	Type	Default	Description
api_key	string	env.ANTHROPIC_API_KEY	API key for Authorization header
base_url	string	https://api.anthropic.com	Base URL for API
headers	object	-	Additional request headers

Default Headers

BAML automatically injects:

anthropic-version: 2023-06-01

Custom Headers

client<llm> MyClient {
    provider anthropic
    options {
        api_key env.MY_ANTHROPIC_KEY
        model "claude-sonnet-4-20250514"
        headers {
            "X-My-Header" "my-value"
        }
    }
}

Available Models

Model	Use Case	Release	Context
claude-opus-4-1-20250805	Complex coding, AI agents	Aug 2025	200K
claude-sonnet-4-20250514	Default choice, versatile	May 2025	200K-1M
claude-3-5-haiku-20241022	Fast, cost-efficient	Oct 2024	200K

See Anthropic Models for the complete list.

Provider Parameters

Option	Type	Default	Description
model	string	-	Model identifier
max_tokens	int	4096	Maximum response tokens
temperature	float	-	Sampling temperature
top_p	float	-	Nucleus sampling
top_k	int	-	Top-k sampling

note

Anthropic's default behavior converts PDFs to base64 while keeping other media types as URLs, since the API requires PDFs to be base64-encoded.

See the Anthropic API documentation for all options.

See Also

• AWS Bedrock (for Claude on AWS)
• Vertex AI (for Claude on GCP)
• Client Overview