Core runtime engine for Common Agent Runtime.

The runtime loop:

1. Receive a proposal (batch of actions from a model)
2. Build a DAG from state_dependencies
3. Execute each level (concurrent if no ABORT actions, sequential otherwise)
4. Validate, execute with idempotency + timeout + retry, commit
5. On abort: rollback state to pre-proposal snapshot

car-engine

Core runtime engine for the Common Agent Runtime.

What it does

The engine receives action proposals from a model, builds a dependency DAG, and executes actions concurrently where possible. It handles validation, idempotency, timeouts, retries, and state rollback on abort. Integrates with car-policy for rule enforcement and car-eventlog for audit logging.

Usage

use car_engine::{Runtime, ToolExecutor, CostBudget};
use car_ir::ActionProposal;

// Register tools and execute proposals
let runtime = Runtime::new(state, policy, eventlog, tools);
let result = runtime.execute(&proposal).await?;

Crate features

• DAG-based concurrent execution
• Result caching with ResultCache
• Rate limiting with RateLimiter
• Capability-based tool access control
• Checkpoint/restore for crash recovery

Part of CAR -- see the main repo for full documentation.