# Architecture

MoonLab is organized around four deep public Modules.

- **sim** compiles Scenarios and owns deterministic Virtual Time, Enabled Actions, Envelopes, Timers, Stable Storage, faults, Observations, correctness checks, and one Simulation Run.
- **explore** owns seeded campaigns, exact Replay, Failure Signatures, and the bounded Shrinker.
- **artifact** owns strict versioned Replay JSON, Trace JSONL, and Run Report JSON data contracts.
- **runner** owns static Scenario registration, command behavior, exit classification, and Native artifact-file orchestration.

```mermaid
flowchart LR
  Model["Typed System Model"] --> Compile["Scenario compile"]
  Compile --> Sim["sim: one bounded run"]
  Sim --> Explore["explore: campaign/replay/shrink"]
  Sim --> Artifact["artifact: replay/trace/report"]
  Explore --> Artifact
  Artifact --> Runner["runner: registered CLI"]
  Runner --> Native["Native files and terminal"]
```

The portable Modules do not access host time, randomness, filesystems, processes, threads, or sockets. Simulated network and storage behavior are implementations inside `sim`, not external Adapter Interfaces. Important choices are recorded under `docs/adr/`; domain terminology lives in `CONTEXT.md`.