Crate car_multi 

Multi-agent coordination for Common Agent Runtime.

Provides six coordination patterns:

Pattern	Description
Swarm	N agents on the same problem (parallel, sequential, or debate)
Pipeline	Linear chain — each agent’s output feeds the next
Supervisor	One agent reviews workers, iterates until approval
Delegator	Main agent spawns specialists mid-run via a tool
MapReduce	Fan-out to N mappers, reduce into a single result
Vote	N agents answer independently, majority wins

How agents communicate

Agents communicate through three mechanisms:

1. Shared state — all agents in a coordination group share the same Arc<StateStore> and Arc<EventLog> via SharedInfra. Agents can read each other’s state writes.

2. Task enrichment — orchestrators pass prior agents’ outputs into the next agent’s task prompt (e.g., sequential swarm, supervisor feedback).

3. Mailbox — async channel-based messaging for real-time inter-agent communication during execution.

The AgentRunner trait

Since the runtime doesn’t own the model, the caller implements AgentRunner to drive the model loop. car-multi orchestrates when and how agents run; the caller decides what each agent does.

use car_multi::{AgentRunner, AgentSpec, AgentOutput, Mailbox, MultiError};
use car_engine::Runtime;

struct MyRunner { /* OpenAI client, etc. */ }

#[async_trait::async_trait]
impl AgentRunner for MyRunner {
    async fn run(
        &self,
        spec: &AgentSpec,
        task: &str,
        runtime: &Runtime,
        mailbox: &Mailbox,
    ) -> Result<AgentOutput, MultiError> {
        // 1. Call your LLM with spec.system_prompt + task
        // 2. Parse response into ActionProposal
        // 3. runtime.execute(&proposal).await
        // 4. Return AgentOutput
        todo!()
    }
}

Re-exports

pub use error::MultiError;

pub use mailbox::Mailbox;

pub use runner::AgentRunner;

pub use shared::SharedInfra;

pub use types::AgentOutput;

pub use types::AgentSpec;

pub use types::Message;

pub use types::MessageKind;

pub use patterns::delegator::Delegator;

pub use patterns::delegator::DelegatorResult;

pub use patterns::map_reduce::MapReduce;

pub use patterns::map_reduce::MapReduceResult;

pub use patterns::pipeline::Pipeline;

pub use patterns::pipeline::PipelineResult;

pub use patterns::supervisor::Supervisor;

pub use patterns::supervisor::SupervisorResult;

pub use patterns::swarm::Swarm;

pub use patterns::swarm::SwarmMode;

pub use patterns::swarm::SwarmResult;

pub use patterns::fleet::Fleet;

pub use patterns::fleet::FleetResult;

pub use patterns::vote::Vote;

pub use patterns::vote::VoteResult;

Modules

error

Error types for multi-agent coordination.

mailbox

Async channel-based mailbox for inter-agent messaging.

patterns

Coordination patterns for multi-agent systems.

runner

AgentRunner trait — the caller’s model loop abstraction.

shared

Shared infrastructure — creates Runtimes that share state, log, and policies.

types

Core types for multi-agent coordination.