# LlmBench Kotlin Multiplatform Architecture

> Explore the shared KMP core, platform clients, and Compose-first UI strategy that power LlmBench across Android, with planned desktop and iOS support.

LlmBench is built as a Kotlin Multiplatform (KMP) workspace that separates shared domain logic from platform-specific clients. This architecture lets Android, desktop, and iOS clients reuse the same core while preserving native capabilities where they matter most.

## Shared module

The shared Kotlin Multiplatform module contains portable logic that runs on every target:

<CardGroup>
  <Card title="Provider/model registry" icon="database">
    Central registry of supported providers and models, including metadata and adapter interfaces.
  </Card>

  <Card title="Profile + prompt tools" icon="message">
    Utilities for parsing, validating, and applying portable AI profiles and prompts.
  </Card>

  <Card title="Portable domain logic" icon="code">
    Business rules, comparison logic, and other domain code that does not depend on platform APIs.
  </Card>
</CardGroup>

## Platform clients

Each platform owns the parts of the stack that require native behavior:

### Android app

The Android app is the first shipping client and owns:

- **WebView host and file chooser**: Renders provider web interfaces and handles file uploads through the platform picker
- **Provider tweaks and mobile performance**: Applies userscripts and CSS adaptations for mobile layout
- **Custom Tabs, intents, and Keystore**: Handles external authentication flows and secure credential storage

### Desktop app (planned)

A desktop client will reuse the shared KMP core while providing native WebView or browser integration appropriate for desktop operating systems.

### iOS app (planned)

An iOS client will reuse the same shared core with platform-specific WebView and storage implementations.

## Backend strategy

Backends are optional, not the default. LlmBench prefers client-side processing where possible. If a feature truly needs a backend, the project prefers a small stateless service and evaluates free tiers (Cloudflare, Google Cloud, AWS, Oracle) based on actual requirements rather than choosing infrastructure first.

## UI strategy: Compose-first

LlmBench uses Jetpack Compose as the primary UI toolkit. Shared UI moves into Compose Multiplatform only where it does not weaken:

- Native WebView behavior
- File upload handling
- Authentication flows
- Secure storage access

<Note>
  Mobile UX is a product constraint: long chats must stay responsive, file upload must work, and provider tweaks should reduce wasted chrome and animation without breaking provider pages.
</Note>

## Architecture diagram

```text
shared (Kotlin Multiplatform)
├── provider/model registry
├── profile + prompt tools
└── portable domain logic

platform clients
├── Android app
│   ├── WebView host + file chooser
│   ├── provider tweaks / mobile performance
│   └── Custom Tabs / intents / Keystore
├── Desktop app (planned)
└── iOS app (planned)
```