JuliaCon 2026

This joint talk by Sebastian Pfitzner and Shuhei Kadowaki presents two major additions to the Julia VS Code experience.

Sebastian covers recent improvements to the julia-vscode extension, including automatic Julia installation for new user onboarding, and introduces how JETLS integrates into the extension architecture.

Shuhei then presents JETLS, a new language server built on JET.jl's abstract interpretation based code analysis and JuliaLowering.jl's code lowering with source provenance tracking. JuliaLowering.jl performs macro expansion and lowering while preserving the mapping between source locations and lowered code, which enables JETLS to provide accurate go-to-definition, references, and rename that work correctly through macro expansions. Combined with JET.jl's type inference, this gives JETLS the level of code intelligence developers expect from modern language servers like rust-analyzer -- such as type on hover and inlay type hints -- unlike the existing LanguageServer.jl.

We conclude with a live demo comparing JETLS and the existing language server on real-world Julia code. Time permitting, we also demonstrate JETLS's CLI, which exposes the same type-aware diagnostics outside the language server protocol, enabling CI pipelines and AI coding agents to leverage JETLS's analysis directly.