Introduction

Uni is the standard library Scala 3 didn't ship with.

Logging, object wiring, JSON & MessagePack, reactive streams, HTTP clients and servers, RPC, and a browser UI toolkit — small, composable pieces that work identically on the JVM, in the browser and Node.js (Scala.js), and as native binaries (Scala Native), with almost no external dependencies.

It distills the most-used building blocks of the Airframe ecosystem into one cohesive, Scala-3-first library.

Get going in 30 seconds

Add one dependency (Installation) and you have all of it — no à-la-carte modules to assemble.

A quick taste

Object wiring, structured logging, and lifecycle management — three things you usually reach for three libraries for — in a handful of lines:

import wvlet.uni.design.Design
import wvlet.uni.log.LogSupport

class GreeterService extends LogSupport:
  def greet(name: String): String =
    info(s"Greeting ${name}")      // logs with source file + line
    s"Hello, ${name}!"

@main def main =
  Design.newDesign
    .bindSingleton[GreeterService]
    .build[GreeterService] { greeter =>   // wired, started, and cleaned up
      println(greeter.greet("Uni"))
    }

Why Uni?

• 🪶 Minimal dependencies — foundational utilities without dragging in a heavy framework.
• 🌍 One codebase, three runtimes — the same source compiles for JVM, Scala.js, and Scala Native.
• 🧩 Composable — small, focused APIs designed to combine, not to lock you in.
• ⚡ Scala 3 first — built around derives, given, enums, and macros.
• 🔋 Production-tested — battle-hardened code, refined from the Airframe ecosystem.

What's inside

Core

Module	Description
Design	Object wiring with lifecycle management
Logging	Logging with source-location tracking
Surface	Compile-time type introspection
FileSystem	Cross-platform file I/O with IOPath

Data & Serialization

Module	Description
JSON	Pure-Scala JSON parser and DSL
MessagePack	Compact binary serialization
Weaver	Derivation-based codecs — JSON / MessagePack / Map from one derives Weaver

Async & Control Flow

Module	Description
Rx	Reactive streams and async data flows
Control	Retry, circuit breaker, rate limiter, cache, resources
BackgroundTask	Cancellable, progress-pollable background workers

HTTP & RPC

Module	Description
HTTP	Cross-platform client and server (Netty / Node.js / Native)
RPC	Type-safe remote calls, with client code generation
WebSocket	Cross-platform bidirectional WebSocket client
Server-Sent Events	One-way server→client streaming

UI & CLI

Module	Description
CLI	Terminal styling, progress bars, command launching
Web UI	Reactive browser UIs with RxElement (Scala.js)

Testing

Module	Description
UniTest	Lightweight, expressive, cross-platform test framework

Next steps

• 📦 Installation — add Uni to your sbt / Scala CLI project
• 🧭 Design Principles — the architecture and the why
• 🔍 Core Utilities — start exploring the foundational APIs