Architecture

The monorepo contains a pnpm workspace for applications and packages and a Cargo workspace for the agent crates.

apps/oppa (Tauri host + React UI)
        │
        ▼
   oppa-agent
   ├── oppa-auth ────────────┐
   ├── oppa-transport        │
   ├── oppa-storage          │
   ├── oppa-discovery        ├── infrastructure boundaries
   ├── oppa-renderer         │
   ├── oppa-spooler          │
   └── oppa-platform ────────┘
        │
        ▼
oppa-printer · oppa-protocol · oppa-product · oppa-core

The TypeScript side contains:

@openprinter/protocol → canonical TypeBox schemas, types, and codecs
@openprinter/server   → protocol sessions over host-owned transports
node-server example  → discovery/pairing host, WebSocket gateway, and job endpoints

Boundary rules

• apps/oppa is a host. Tauri commands translate typed UI requests into oppa-agent operations.
• oppa-agent must be usable without Tauri so a future headless shell can reuse the runtime.
• Low-level crates do not depend on UI code or Tauri.
• The protocol contains only generic printer-agent concepts.
• The server SDK verifies paired public credentials. Server applications own durable stores, rate limits, connection affinity, and cluster or broker routing; the SDK owns one protocol session.
• Credentials use secure platform storage and never the SQLite job database.
• Rendering produces an output representation; spoolers own submission and timeouts.
• Discovery failures degrade one provider rather than terminating the agent.

Protocol source of truth

The TypeBox definitions in @openprinter/protocol are canonical. A deterministic script emits a language-neutral JSON Schema. Both the Rust crate and TypeScript package validate the same committed fixtures, which prevents a protocol change from landing on only one side.

Evolution

The interfaces leave room for a headless Linux agent, service-mode installation, or alternative desktop shell. Those targets are not implemented by the initial workspace. New crates are added only when a responsibility cannot be represented cleanly by an existing boundary.