123 lines
6.4 KiB
Markdown
123 lines
6.4 KiB
Markdown
# MLX Server
|
|
|
|
Native macOS app for running local LLMs on Apple Silicon via [MLX](https://github.com/ml-explore/mlx). Built with SwiftUI, it provides both a **chat UI** and an embedded **OpenAI-compatible API server**. Supports vision, tool use, and thinking mode.
|
|
|
|
## Supported Models
|
|
|
|
| Alias | Model | Context | Capabilities |
|
|
|-------|-------|---------|-------------|
|
|
| `gemma` | `mlx-community/gemma-3-4b-it-4bit` | 128k | Vision, tool use (`tool_code` blocks) |
|
|
| `qwen` | `mlx-community/Qwen3-VL-4B-Instruct-4bit` | 256k | Vision, tool use (`<tool_call>` tags) |
|
|
| `qwen3.5-9b` | `mlx-community/Qwen3.5-9B-4bit` | 256k | Thinking mode, tool use |
|
|
|
|
Any model in MLX format on HuggingFace can be added — there is no restriction on uploader or architecture.
|
|
|
|
## Quick Start
|
|
|
|
Requires macOS 15+, Xcode 16.4+, and `xcodegen` (`brew install xcodegen`).
|
|
|
|
```bash
|
|
./build.sh # Debug build
|
|
open "build/Debug/MLX Server.app"
|
|
```
|
|
|
|
## App Features
|
|
|
|
- **Chat interface** with markdown rendering, image attachments (file picker, drag & drop, clipboard paste, Finder copy-paste)
|
|
- **Model picker** in toolbar with local/download status indicators and re-download button
|
|
- **Download progress modal** — shows file progress, percentage, and speed when downloading a new model
|
|
- **Thinking mode** — models like Qwen3.5 can reason internally before responding; thinking content appears in a collapsible box. Toggle on/off in Settings.
|
|
- **Streaming responses** with live token display
|
|
- **Export chat** — File > Export Chat (Cmd+Shift+S) saves conversations as Markdown or RTF (Pages-compatible)
|
|
- **Status bar** showing model name, context window, tokens/sec, token counts, GPU memory, API server status
|
|
- **Keyboard shortcuts**: `Cmd+N` (new chat), `Cmd+Return` (send), `Escape` (stop), `Cmd+1/2/3/4` (switch models), `Cmd+Shift+S` (export)
|
|
- **Settings** (`Cmd+,`): default model, thinking mode toggle, system prompt, API port, API auto-start, idle unload timeout
|
|
- **Idle auto-unload** — model is unloaded after configurable idle time (resets on both user input and model output), reloaded on next request
|
|
|
|
## API Server
|
|
|
|
The embedded API server (toggle in toolbar) runs on port 1234 by default. Standard OpenAI-compatible endpoints:
|
|
|
|
- `GET /v1/models` — lists available models with `context_window` sizes
|
|
- `POST /v1/chat/completions` — chat completions (streaming and non-streaming)
|
|
- `GET /health` — health check
|
|
|
|
### Model Swapping
|
|
|
|
Send any model ID or alias in the `model` field. If it differs from the currently loaded model, the server swaps automatically:
|
|
|
|
```bash
|
|
curl http://localhost:1234/v1/chat/completions \
|
|
-H "Content-Type: application/json" \
|
|
-d '{"model": "gemma", "messages": [{"role": "user", "content": "Hello"}]}'
|
|
```
|
|
|
|
### Vision
|
|
|
|
Pass images as base64 data URIs in the `image_url` content part:
|
|
|
|
```json
|
|
{
|
|
"model": "gemma",
|
|
"messages": [{
|
|
"role": "user",
|
|
"content": [
|
|
{"type": "text", "text": "What's in this image?"},
|
|
{"type": "image_url", "image_url": {"url": "data:image/png;base64,..."}}
|
|
]
|
|
}]
|
|
}
|
|
```
|
|
|
|
### Tool Use
|
|
|
|
Pass tools in the `tools` field (OpenAI format). The server handles model-specific formatting (Gemma `tool_code` blocks, Qwen `<tool_call>` XML tags) and parses tool calls from output automatically. When tools are present during streaming, output is buffered to strip tool-call markup before sending to the client.
|
|
|
|
## Project Structure
|
|
|
|
```
|
|
MLXServer/
|
|
├── MLXServerApp.swift — App entry point, GPU cache config
|
|
├── ContentView.swift — Main layout, toolbar, keyboard shortcuts
|
|
├── Models/
|
|
│ ├── ModelConfig.swift — Model definitions, alias/repoId resolution
|
|
│ └── ChatMessage.swift — Chat message data model, thinking tag parser
|
|
├── ViewModels/
|
|
│ ├── ModelManager.swift — Model loading/switching, download tracking, idle unload
|
|
│ └── ChatViewModel.swift — Chat state, ChatSession, API server lifecycle
|
|
├── Views/
|
|
│ ├── ModelPickerView.swift — Toolbar model selector with re-download
|
|
│ ├── ChatMessagesView.swift — Scrollable message list with markdown + thinking blocks
|
|
│ ├── ChatInputView.swift — Text input + image attach (paste, drag, picker)
|
|
│ ├── DownloadModalView.swift — Model download progress overlay
|
|
│ ├── StatusBarView.swift — Model info, tok/s, GPU memory, API status
|
|
│ ├── MonitorView.swift — Inference statistics monitor
|
|
│ └── SettingsView.swift — System prompt, thinking mode, API, idle settings
|
|
├── Commands/
|
|
│ └── SaveChatCommands.swift — File menu export command
|
|
├── Server/
|
|
│ ├── APIServer.swift — NWListener HTTP server, SSE streaming, KV cache reuse
|
|
│ ├── APIModels.swift — OpenAI-compatible Codable structs
|
|
│ ├── ToolCallParser.swift — Parses tool calls from model output
|
|
│ └── ToolPromptBuilder.swift — Model-specific tool prompt formatting
|
|
└── Utilities/
|
|
├── LocalModelResolver.swift — Offline-first HuggingFace cache resolution (sandbox + system)
|
|
├── ChatExporter.swift — Export conversations to Markdown or RTF
|
|
├── FocusedValues.swift — FocusedValue keys for menu bar integration
|
|
└── Preferences.swift — UserDefaults wrapper
|
|
|
|
project.yml — xcodegen project spec (dependencies, settings, deployment target)
|
|
build.sh — One-command build script (xcodegen + xcodebuild)
|
|
```
|
|
|
|
## Key Design Decisions
|
|
|
|
- Uses `mlx-swift-lm` (`MLXVLM` / `VLMModelFactory`) for inference — loads any MLX-format model from HuggingFace
|
|
- **Offline-first**: `LocalModelResolver` checks both the sandboxed app container and `~/.cache/huggingface/hub/` for locally-cached models before downloading
|
|
- **No duplicate storage**: custom `HubApi` with blob cache disabled — models are stored once in the snapshot cache
|
|
- **KV cache reuse** across API requests — reuses `ChatSession` when conversation history prefix matches
|
|
- **Thinking mode**: `enable_thinking` passed via Jinja template context; `<think>` tags parsed in real-time during streaming
|
|
- HTTP server built on `Network.framework` (`NWListener`) — no third-party server dependencies
|
|
- Model-specific prompt formatting: Gemma uses `tool_code` blocks, Qwen uses `<tool_call>` XML tags
|
|
- GPU cache limit set to 20 MB; cache cleared on model unload
|