Anthropic Provider

Handles the Anthropic Messages API with SSE streaming. Selected automatically when ModelConfig.api == ApiProtocol::AnthropicMessages.

Usage

#![allow(unused)]
fn main() {
use phi_core::BasicAgent;
use phi_core::provider::ModelConfig;

let api_key = std::env::var("ANTHROPIC_API_KEY").unwrap();
let agent = BasicAgent::new(ModelConfig::anthropic(
    "claude-sonnet-4-20250514",
    "Claude Sonnet 4",
    &api_key,
));
}

Features

Streaming SSE

Uses reqwest-eventsource to parse Anthropic's SSE stream. Events handled:

• message_start — Input token usage, cache stats
• content_block_start — Text, thinking, or tool_use block
• content_block_delta — Text, thinking, input JSON, or signature deltas
• content_block_stop — Block complete
• message_delta — Stop reason, output usage
• message_stop — Stream complete

Extended Thinking

Set thinking_level to enable thinking with a token budget:

Thinking content is streamed as Content::Thinking with a cryptographic signature for verification.

Cache Control

Automatic prompt caching via cache_control markers:

• System prompt: Always cached with {"type": "ephemeral"}
• Second-to-last message: Gets cache_control on its last content block, creating a cache breakpoint

This means on repeated calls, only the latest message is processed at full price.

Configuration

Environment Variables