---
title: Core architecture
description: The stable seams between composition, portable Kernel mechanisms, host scheduling, and Plugin execution.
---

## Four ownership layers

### App Composition

Authoring-time intent: Instances, package inputs, configuration, execution
classes, placement, and explicit Capability bindings. Authoring tools resolve
this into one complete Plan before boot.

### Portable Kernel

A host-neutral state machine for graph validation, staged activation, readiness,
typed invocation, scopes, cancellation, supervision, shutdown, and bounded
diagnostics. It depends on no Tokio, OS, network, filesystem, database, or
product API.

### Runtime Driver

The host implementation of scheduling, monotonic time, wakeups, cancellation
lanes, joins, and shutdown translation. Tokio, browser JavaScript, and WASIp2
are Driver profiles rather than Kernel branches.

### Execution Adapter

The owner of Plugin generation and endpoint mechanics: native factories, Bun
child processes, future host-supported sources, isolation, framing, and
Adapter-specific failure classification.

## The deletion test

A concern belongs in the Kernel only when deleting the Kernel would force every
Runner and Adapter to reimplement it. HTTP, PostgreSQL, Auth, secrets,
OpenTelemetry, UI, and product workflows fail that test: removing their selected
Plugins removes their complexity.

## Dependency direction

```text
product Plugins / authoring / examples
                 ↓
Drivers and Execution Adapters
                 ↓
portable protocols and core Interfaces
                 ↓
App Plan + Kernel
```

Core never depends back on a concrete Driver, Adapter, Plugin, CLI, or example.