Capture Checking is an upcoming feature that brings capability tracking into Scala’s type system, offering a new way to express and control effects in direct style, all without requiring monads or other heavy abstractions.

This talk introduces the core ideas behind Capture Checking, how it fits into Scala’s type system, and the kinds of bugs it can prevent. We’ll walk through practical examples that show how capabilities can improve safety and clarity in everyday code, and give a peek into how the compiler enforces these guarantees.

We’ll also talk about where things stand today: what’s implemented, what’s experimental, and what open questions remain. The goal is to give you a clear, realistic picture of Capture Checking as it exists now – its motivations, its mechanics, and its potential.

Whether you’re new to capabilities or wondering how effect tracking will evolve in Scala, this is your starting point.