> ## Documentation Index
> Fetch the complete documentation index at: https://docs.arupa.dev/llms.txt
> Use this file to discover all available pages before exploring further.

# Introduction

> Understand the role of Plugins.

A plugin is a deployable unit that adds a feature to an Arupa application. It
contains the feature-specific code, while the Arupa Kernel provides the shared
runtime and application integration. This keeps the Kernel responsible for
common concerns and lets plugins focus on their own business logic.

The Kernel manages the plugin lifecycle: it loads the plugin package, starts
the selected backend, registers the plugin, and connects the resources declared
by the plugin to the application. A plugin can expose HTTP routes, static
resources, Socket.IO namespaces and events, and plugin-to-plugin message
handlers. The Kernel routes requests and events to the corresponding plugin
and enforces the access policy declared for each resource.

Plugins can run as WASM modules or gRPC components. During registration, a
plugin returns its identity and the resources it provides. Its handlers then
implement the feature behavior and use the Kernel Host API when they need
shared application capabilities, such as logging, key-value storage,
configuration updates, Socket.IO messages, or communication with another
plugin.

Each plugin is described by a manifest containing metadata such as its name,
version, backend type, contract version, entry path, and startup command. The
manifest and backend artifact are packaged together so the Kernel can discover
and load the plugin as a single unit.

The rest of this section covers the package format, plugin protocol, Host API,
and the available transports.