A New Era for Python Type Checking in PyCharm
In the latest PyCharm release (2026.1.2), developers can now tap into Pyrefly as an external type provider. This integration dramatically accelerates the IDE's code insight features—from autocompletion and hover information to error diagnostics—by offloading the heavy lifting to a lightning-fast, Rust-based engine. If you work with large, complex Python codebases and crave quicker feedback, this update is worth exploring.
Understanding the Pyrefly Language Server Protocol
What Is LSP?
LSP stands for Language Server Protocol, a standardized communication framework that enables code editors to connect with language servers. Instead of each IDE reinventing the wheel for every language feature, LSP allows a single server to deliver rich code intelligence across different tools. The protocol supports:
- Smart code completions
- Hover information (e.g., quick documentation previews)
- Go to definition and other navigation actions
- Type-related error checking and diagnostics
The magic of LSP lies in its reusability: you can use the same language server in PyCharm, VS Code, or even in a CI pipeline, without reimplementing the logic each time.
Pyrefly: Meta's Next-Gen Type Checker
Pyrefly is Meta's latest Python type checker, built entirely in Rust as a successor to the OCaml-based Pyre. By rewriting the core in Rust, Pyrefly achieves significantly faster performance and better cross-platform compatibility. It's not just a port—it's a more capable and robust tool designed to handle large-scale Python codebases with high precision and low overhead. Key benefits include:
- Higher performance and efficiency – Rust's memory safety and speed translate to near-instant type analysis.
- Enhanced code intelligence – As an external type provider, Pyrefly powers type inference, diagnostics, quick documentation, and inlay hints.
- Scalability – Ideal for sprawling projects where traditional engines struggle.
Key Advantages of Enabling Pyrefly
Turning on Pyrefly in PyCharm brings tangible improvements for developers who prioritize speed and robust typing. The Rust-based architecture delivers faster responses across all code insight features, while maintaining the same level of accuracy. This is particularly valuable for teams working on large, dynamic Python codebases that need to stay performant. By delegating analysis to Pyrefly via LSP, PyCharm can focus on what it does best—editing and project management—without compromising on intelligence.
Enabling Pyrefly in PyCharm 2026.1.2
Step-by-Step Activation
Getting started with Pyrefly is straightforward. Follow these steps:
- Open your Python project in PyCharm.
- Look at the bottom bar of the IDE window. You'll see a Type widget (by default showing the built-in type engine).
- Click on the widget and select the option to use Pyrefly as the type provider.
- If Pyrefly is not already installed, PyCharm will automatically download and set it up for you.
- Once activated, a new Pyrefly icon appears in the same area. Hover over it to check the installed version and verify it's running.
What to Expect Once Enabled
After switching, all code insight features—type inference, inlay hints, quick documentation, and diagnostics—are powered by Pyrefly. You should notice a noticeable speed bump as the IDE responds faster to typing and navigation. Note: The integration currently works for local interpreter configurations only. Support for Docker, Docker Compose, WSL, SSH, and multi-module projects is planned for future releases.
Embrace Pyrefly today and experience a smoother, faster Python development workflow in PyCharm 2026.1.2.