# Technical design

How the [product](../product/README.md) is built.

```mermaid
flowchart LR
    subgraph APPS["Apps · one shared client library"]
        DESKTOP["muxy-app<br/>desktop · Rust + GPUI"]
        TUI["muxy<br/>CLI and terminal UI · Ratatui"]
        PHONE["Phone apps<br/>muxy-mobile SDK"]
    end
    SERVER["muxy-server<br/>Ghostty terminals · history · projects"]
    REMOTE["muxy-server<br/>on another computer"]
    DESKTOP <-->|"Unix socket"| SERVER
    TUI <-->|"Unix socket"| SERVER
    DESKTOP <-->|"SSH · muxy stdio"| REMOTE
    TUI <-->|"SSH · muxy stdio"| REMOTE
    PHONE <-->|"TLS"| SERVER
    PHONE <-->|"SSH · muxy stdio"| REMOTE
```

The big ideas:

1. **The server owns the terminals.** Each session is a Ghostty terminal on the
   server, with its history. Apps never parse terminal output. They receive rows
   of styled text and draw them.
2. **Only changes are sent.** About 60 times a second the server sends the rows
   that changed. A slow app gets one merged update, never a backlog.
3. **One client library.** The desktop app, the terminal UI, and the phone apps
   all use the same Rust client and protocol.
4. **The protocol only grows.** New fields and messages don't break older
   builds.

## Read next

1. [Architecture](./architecture.md): processes, crates, and how a keystroke
   travels.
2. [Protocol](./protocol.md): how apps and the server talk, and the
   compatibility rules.
3. [Mobile](./mobile.md): how phones pair and connect.
4. [Decisions](./decisions.md): the key choices and why they were made.
5. [Constraints](./constraints.md): supported platforms and hard-won lessons.