agentyk

Compose agents from values and run them.

An [Agent] is built entirely by value — a system prompt, a model ([ModelSpec]), capabilities ([Capability]), tools ([Tool]) — with no entity creation, no registration, and no ids to thread. Ids exist only as internal correlation handles on sessions and events.

This is the framework crate: builders, the default in-process executor, bundled drivers (sim; OpenAI/Anthropic behind http), the JSONL event log, and MCP support. The contract it drives — traits, the event protocol, and the turn state machine — lives in agentyk-core and is fully re-exported here; depend on core directly only when implementing a seam (a custom driver, capability, event log, or executor).

The domain language (events protocol, capabilities, drivers, the input → reason → act turn) is inherited from everruns; agentyk is the value-first core that everruns-core and everruns-runtime are intended to be rebuilt on top of.

use agentyk::{Agent, ModelSpec, SimDriver, SimTurn};

# #[tokio::main(flavor = "current_thread")]
# async fn main() -> agentyk::Result<()> {
let agent = Agent::builder()
    .name("greeter")
    .system_prompt("You are terse.")
    .model(ModelSpec::llmsim())
    .driver(SimDriver::new([SimTurn::text("hi!")]))
    .build()?;

let mut session = agent.session();
let turn = session.run("hello").await?;
assert_eq!(turn.response, "hi!");
assert!(!session.events().await?.is_empty());
# Ok(())
# }

With a real provider (feature http):

let agent = Agent::builder()
    .system_prompt("You are a coding agent.")
    .model(ModelSpec::anthropic("claude-sonnet-4-5").api_key(key))
    .capability(my_capability)
    .build()?;
let result = agent.run("list the files").await?;