Boosting Type Checking in PyCharm 2026.1.2 with Pyrefly LSP Integration

PyCharm 2026.1.2 introduces a powerful option to supercharge your code insight features: enabling Pyrefly as an external type provider through the Language Server Protocol (LSP). This integration dramatically accelerates type inference, diagnostics, and other intelligence features, especially for large Python projects. Below, we answer key questions about this new capability.

What is Pyrefly and how does it differ from Pyre?

Pyrefly is Meta's next-generation Python type checker, rebuilt from scratch in Rust to replace its predecessor, Pyre (written in OCaml). The shift to Rust brings significantly faster performance and better cross-platform portability. Pyrefly is not just a port; it’s engineered to be more capable and robust, offering an efficient toolset for maintaining large-scale Python codebases with high precision and minimal overhead. Unlike Pyre, Pyrefly integrates seamlessly with the LSP, allowing it to power code intelligence in any editor that speaks the protocol.

Boosting Type Checking in PyCharm 2026.1.2 with Pyrefly LSP Integration — Source: blog.jetbrains.com

What is the Language Server Protocol (LSP) and why does it matter?

The Language Server Protocol (LSP) is a standardized communication protocol between code editors or IDEs and language servers. It enables a single language server to provide code intelligence features—such as code completion, hover information, go-to-definition, and error diagnostics—across multiple tools. The key benefit is that language-specific logic doesn't need to be reimplemented for each editor, IDE, or CI pipeline. By using LSP, Pyrefly can deliver its advanced type checking to PyCharm and other compatible environments with minimal integration effort.

What benefits does Pyrefly bring to PyCharm users?

Integrating Pyrefly via LSP offers three major advantages:

Higher performance and efficiency – The Rust-based architecture makes Pyrefly dramatically faster than built-in type engines, reducing latency in code insight features.
Enhanced code intelligence – Pyrefly powers type inference, type-related diagnostics, quick documentation, and inlay hints, all of which become more responsive.
Scalability – Designed for large, complex Python codebases, Pyrefly maintains high precision even with thousands of files, keeping resource usage low.

These benefits are particularly valuable for developers working on large projects where performance and robust typing are critical.

How do I enable Pyrefly in PyCharm 2026.1.2?

Enabling Pyrefly is straightforward. Look for the Type widget at the bottom of the PyCharm window. By default, the IDE uses its built-in type engine. Click on the widget and select the option to switch to Pyrefly. If Pyrefly is not yet installed on your system, PyCharm will automatically download and set it up for you. Once active, a Pyrefly icon appears in the bottom bar; hovering over it shows the version being used. You can switch back to the built-in engine anytime.

Are there any limitations to the Pyrefly integration?

Currently, the integration works only with local interpreter configurations. Support for Docker, Docker Compose, WSL, SSH, and multi-module projects is planned for future releases. If your project relies on any of these remote or containerized environments, you may need to wait for an update. For local projects, however, the experience is smooth and provides a noticeable performance boost.

When should I choose Pyrefly over PyCharm's built-in type engine?

Pyrefly is ideal for developers dealing with large, complex Python codebases where performance and accurate type inference are top priorities. If your project has thousands of files or heavy use of dynamic typing, you’ll notice a significant speed improvement in code completion, error checking, and navigation. For smaller or simpler projects, the built-in engine may suffice, but there’s no harm in trying Pyrefly—you can always switch back. The choice ultimately depends on your project’s scale and your need for faster insight features.

What future enhancements are planned for Pyrefly in PyCharm?

The development team is actively working on expanding support to Docker, Docker Compose, WSL, SSH, and multi-module projects. These additions will make Pyrefly accessible to a broader range of development setups. Additionally, ongoing optimizations in the LSP communication and Pyrefly’s Rust core are expected to further improve performance and feature parity with the built-in engine. Keep an eye on PyCharm updates for announcements about these enhancements.

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