Architecture

Rust crate dependency graph

moqtap-codec (MIT)           ← pure codec, no I/O. Drafts 07–17.
    │
    ├── moqtap-client (MIT)       ← outbound QUIC/WebTransport MoQT client
    │
    ├── moqtap-proxy (MIT)        ← transparent intercepting proxy framework
    │                             (uses codec + client's transport layer)
    │
    └── moqtap-trace (MIT)        ← TraceEvent model, .moqtrace file I/O

The CLI (moqtap-cli) ties the four crates together, providing peek (uses moqtap-client) and intercept (uses moqtap-proxy) commands, with optional .moqtrace output via moqtap-trace.

The Desktop app uses moqtap-client and moqtap-proxy via Tauri IPC, with a Vue 3 frontend and auto-generated TypeScript bindings via tauri-specta.

JavaScript library graph

@moqtap/codec                ← wire codec, drafts 07–17, zero dependencies
    ↓
@moqtap/trace                ← .moqtrace format, session recorder

The Browser Extension uses @moqtap/codec and @moqtap/trace for real-time decoding of WebTransport connections in the browser.

Design principles

• Codec is pure — moqtap-codec has zero runtime dependencies. It’s just bytes in, structs out.
• Lenient parsing — unknown fields produce warnings, not errors. A debug tool must show you what’s wrong.
• quinn for QUIC, wtransport for WebTransport — both are shared across drafts through the client’s transport module.
• Proxy observes without state — moqtap-proxy parses MoQT frames inline without buffering, emitting structured ProxyEvents. It forwards traffic unmodified by default.
• Multi-draft — codecs support drafts 07–17 via feature flags (Rust) or subpath imports (JS). Draft-specific logic is isolated so adding new drafts is additive.
• Auto-generated types — TypeScript types for the desktop app are derived from Rust structs via tauri-specta, ensuring the IPC contract never drifts.

Data flow

CLI — peek mode

User → moqtap peek → moqtap-client → quinn (QUIC) → MoQT Relay
                                          ↓
User ← terminal output ← TraceEvent ← quinn

CLI — intercept mode

MoQT Client → moqtap-proxy (listener) → moqtap-proxy (upstream) → MoQT Relay
                      ↓                           ↓
              ProxyEvent → terminal output / .moqtrace file

Desktop app

User (Vue UI) → Tauri IPC → Rust commands → quinn (QUIC) → MoQT Relay
                                                    ↓
User (Vue UI) ← Tauri events (60Hz batched) ← TraceEvent ← quinn

Browser extension

Page JS → content.ts (hooks WebTransport) → bridge → background.ts (decode + record)
                                                              ↓
                                              DevTools panel (Vue 3 UI)