Function anthropic_agent_builder 

pub fn anthropic_agent_builder(client: &Client, model: &str) -> AnthropicBuilder

Wrap an existing Anthropic client into an agent builder with prompt caching.

Enables Anthropic’s automatic prompt caching: a top-level cache_control breakpoint that the API places on the last cacheable block and advances as the conversation grows. On Iris’s multi-turn tool loops, where every turn otherwise re-sends the whole transcript at full input price, cached turns are billed at a fraction of that cost. Caching is unconditional: prompts below the model’s cacheable minimum are simply not cached by the API.