# What is OS⁴

OS⁴ is a FreeBSD-based operating system with the Harmonia agent runtime integrated at the system level — not as a userspace application, but as a native component of the OS.

## Why a Dedicated OS

Running an agent as an application on top of a general-purpose OS introduces unnecessary abstraction. OS⁴ eliminates that layer:

| Benefit | Description |
|---------|-------------|
| **Direct hardware access** | Process scheduling, I/O, and memory management without abstraction overhead |
| **Tighter orchestration loops** | The agent observes and controls system-level resources directly |
| **Faster evolution cycles** | Hot patching and binary rollout happen at the OS level with lower latency |
| **Security boundary** | The agent operates within FreeBSD's proven, audited security model |

## FreeBSD Heritage

FreeBSD was chosen for specific technical reasons:

- **Stability** — battle-tested in production environments from Netflix to WhatsApp
- **Clean kernel design** — well-documented, modular, and auditable
- **ZFS** — enterprise-grade storage with snapshots, compression, and data integrity
- **Jails** — lightweight isolation for workload separation
- **BSD license** — permissive licensing compatible with commercial deployment

## Included Harmonia Stack

OS⁴ ships the full Harmonia runtime pre-installed:

- **Common Lisp orchestration** runtime (SBCL)
- **Rust capability layer** (13 core crates + tools + frontends)
- **9-port I/O boundary** (vault, store, router, lineage, matrix, tool-runtime, baseband, swarm, evolution)
- **Declarative configuration** via S-expressions
- **Harmonic machine** for task scheduling and scoring
- **Ouroboros and Phoenix** evolution engines

## Next Steps

- [Getting Started](/docs/os4/getting-started) — download, boot, and configure
- [Platforms](/docs/os4/platforms) — supported architectures and hardware targets
- [Harmonia Architecture](/docs/harmonia/architecture) — runtime stack details