What actually happens when you open a Python file in Cursor and the squiggly lines appear a second later? Most developers never ask. They install an extension, accept the defaults, and move on. But in 2026, the Python tooling stack inside AI code editors has become a real architectural decision, and the choice between Pylance, BasedPyright, and Ruff changes how your editor behaves, how fast it responds, and what your AI assistant can actually see.
The short version: Cursor is a fork of VS Code, and Microsoft does not license Pylance for forks. That single licensing fact reshapes the entire Python setup. Understanding it is the difference between a stack that fights you and one that quietly works.
Why the Python stack in Cursor is different from VS Code
VS Code ships with an official Python extension that pairs with Pylance, Microsoft’s closed-source language server. Pylance is built on Pyright, Microsoft’s open-source static type checker written in TypeScript and distributed through npm. The two are related but not the same: Pyright is the engine, Pylance is the polished, licensed product wrapped around it. (Static program analysis)
Cursor is a VS Code fork, so it uses Open VSX-compatible extensions rather than the Microsoft Marketplace. Microsoft’s licensing terms keep Pylance inside official VS Code. Cursor users who want type checking install Pyright directly, or more often BasedPyright, a community fork that ships stricter defaults and extra checks the open-source Pyright lacks.
This is not a small detail. It means the two editors run genuinely different Python architectures:
| Layer | VS Code | Cursor |
|---|---|---|
| Type checker | Pylance (closed, on Pyright) | Pyright or BasedPyright (open) |
| Linter and formatter | Ruff extension or Pylance features | Ruff with its native language server |
| Protocol | Language Server Protocol | Language Server Protocol |
| Extension source | Microsoft Marketplace | Open VSX-compatible registry |
The good news is that the Language Server Protocol (LSP) decouples editors from tooling. Any editor with an LSP client can host Pyright, BasedPyright, or Ruff’s server. That decoupling is why the same Python stack can run in VS Code, Cursor, Neovim, or anything else that speaks LSP. If you want the broader picture of how these editors diverge, there’s a useful breakdown of how cursor alternatives compare for beginners that walks through the same trade-offs.
Pyright, Pylance, and BasedPyright: what each one actually is
Pyright has been public since 2019 and runs in two modes: a command-line type checker and a language server. In server mode it implements LSP, which is how it plugs into any compatible editor. It is fast, written in TypeScript, and distributed via npm.
Pylance launched in 2020 as the closed-source VS Code extension built on Pyright. It adds IntelliSense behavior and other features that simply are not available outside VS Code. For most VS Code users this is invisible, because Pylance is the default and it works.
BasedPyright emerged around 2024 as a community fork. It adds stricter default type-checking rules, including checks like `reportAny` and `reportExplicitAny`, plus baseline support for tracking existing errors. It is distributed on PyPI as `basedpyright`. The fork exists precisely because the open-source Pyright leaves some strictness on the table, and teams that want aggressive type safety outside VS Code needed a home for those rules.
The practical takeaway: if you are in Cursor and you want the closest thing to Pylance’s type-checking experience, BasedPyright is usually the answer, not raw Pyright.
Ruff’s native language server changes the equation
Ruff is Astral’s Python linter and formatter written in Rust. It reimplements rules from Flake8, isort, pyupgrade, and several other tools, and it added a Black-compatible formatter in 2023. Speed is its headline feature, but the architecture matters more than the benchmarks.
In 2024, Ruff shipped a built-in language server, so it can run as an LSP backend in any LSP-capable editor, including Cursor and Vim as well as VS Code. Cursor users can run Ruff’s server directly for linting and formatting while BasedPyright handles type checking. Two servers, clean separation of concerns, no dependency on Microsoft’s extension model.
This is where a lot of setups go wrong. People install the Ruff VS Code extension and assume it is doing everything. In practice, the extension is a thin client, and understanding what runs where saves hours of confusion. A setup guide for configuring VS Code and Windsurf covers the wiring details that apply equally to Cursor.
A working Cursor Python configuration
Here is the sequence that actually holds up in practice:
- Install BasedPyright from PyPI in your project environment, not globally.
- Install Ruff the same way, pinned to a specific version.
- Point your editor’s Python language server setting at BasedPyright.
- Enable Ruff’s native server for linting and formatting.
- Disable or remove any leftover Pylance references, which will not load in Cursor anyway.
- Commit both tools to your project’s dependency file so every teammate gets identical behavior.
The most common mistake is installing these tools globally and then wondering why CI disagrees with the editor. Pin them per project. The second most common mistake is running both Ruff and a legacy linter like Flake8 at the same time, which produces duplicate warnings and slows everything down.
What this means for AI-assisted editing
Here is the part that rarely gets discussed. Your AI assistant’s quality depends heavily on what the language servers tell it. When BasedPyright reports a type error, the AI has a concrete signal to work from. When Ruff flags an unused import, the model can fix it precisely rather than guessing.
In VS Code, Pylance provides that signal through a closed pipeline. In Cursor, the signal comes from open servers that you control and can inspect. That transparency is an advantage for teams debugging why the AI keeps suggesting a particular fix. If you want to go deeper on how AI edits interact with your code, there’s a solid explanation of how Cursor’s patch versus rewrite modes actually change your code that is worth reading before you trust a bulk edit.
The architecture also affects shared rules. When a team wants consistent AI behavior across a repo, the language server configuration becomes the source of truth. A guide to sharing AI rules across one repo in Cursor and VS Code covers how to keep that consistent.
Where the 2027 question gets genuinely uncertain
It would be dishonest to pretend the 2026–2027 picture is settled. Several things could shift:
- Cursor’s extension model could change, altering how Microsoft-licensed extensions behave.
- Pylance licensing could loosen, though nothing suggests it will.
- BasedPyright and Ruff could converge on overlapping features, reducing the number of moving parts.
- Pyright and BasedPyright feature parity after early 2025 is not something to assume; check each project’s changelog.
What is unlikely to change is the underlying principle. LSP decouples editors from tooling, and that decoupling is why open servers keep winning in forks. Bet on the protocol, not on any single vendor’s bundle.
If you are weighing a move between editors, a comparison of Antigravity, Cursor, and Claude Code for 2026 lays out how the broader tooling market is shifting, and a head-to-head on which AI code editor actually wins gives you the competitive context.
Practical guidance for choosing your stack
For most Python teams in Cursor, the sensible default is BasedPyright plus Ruff. It is fast, fully open, reproducible in CI, and does not depend on a license that excludes your editor. The trade-off is configuration effort: you wire up two servers instead of accepting one bundle.
For teams staying in VS Code, Pylance plus Ruff is the path of least resistance. You get Microsoft’s polished IntelliSense and Ruff’s speed, and you never think about licensing.
The mistake to avoid is mixing assumptions. Do not assume the Cursor experience matches VS Code, and do not assume a tool that works in one will load in the other. A checklist for evaluating AI code editors helps you test these assumptions before committing a whole team.
One more practical note: run your type checker and linter in CI with the exact same versions your editor uses. Editor-only type checking is a comfort, not a guarantee. The teams that get burned are the ones where the editor is clean and the pipeline is not.
Conclusion
The Python tooling difference between Cursor and VS Code comes down to open protocols versus closed bundles. Pylance is excellent, but it is licensed to one editor. Pyright, BasedPyright, and Ruff are open, speak LSP, and therefore run anywhere. In 2026 that flexibility is the safer bet, and it is likely to remain so as editors keep changing. Pick open servers, pin your versions, and let the protocol do the work.
Frequently asked questions
Why can’t I use Pylance in Cursor?
Pylance is a closed-source extension licensed by Microsoft for official VS Code only. Cursor is a VS Code fork that uses a different extension registry, so Pylance will not load. Use Pyright or BasedPyright instead.
Is BasedPyright better than Pyright?
Not universally. BasedPyright adds stricter default rules and baseline support, which suits teams that want aggressive type safety. Plain Pyright is simpler. Try BasedPyright first if you are coming from Pylance and want similar strictness.
Do I need both Ruff and BasedPyright?
Yes, for most setups. They do different jobs. BasedPyright handles type checking; Ruff handles linting and formatting. Running both gives you complete coverage without overlap.
Does Ruff work outside VS Code?
Yes. Ruff ships a native language server that runs in any LSP-capable editor, including Cursor and Neovim. You are not locked into the VS Code extension.
Will my Python setup break when Cursor updates?
It can, which is why you pin tool versions in your project. Editor updates rarely break LSP-based servers, but version drift between your editor and CI is a common source of surprises.
What is the single most important architecture decision here?
Choosing open LSP servers over a closed bundle. That choice keeps your Python tooling portable across editors and reproducible in CI, regardless of which editor your team prefers next year.
The remaining uncertainty is not about whether LSP survives, but about who owns the pieces around it. Watch the licensing surface, not the feature lists. If Cursor’s extension marketplace rules shift, or if Microsoft relaxes Pylance’s terms, the calculus changes overnight. Neither is likely, but both are worth monitoring in release notes rather than assuming stability. The safer habit is to treat your Python language server configuration as infrastructure: versioned, reviewed, and documented in the repo so a new teammate can reproduce it in minutes.
There is also a quieter risk worth naming. Forks like Cursor move fast, and their bundled defaults can drift between releases. A tool that worked in January may be silently upgraded in June. Pinning BasedPyright and Ruff in your dependency file protects you from that drift, but only if your editor actually reads the project environment rather than a globally installed copy. Verify that first, before debugging anything else.
Finally, resist the temptation to chase feature parity for its own sake. BasedPyright’s strictness is useful only if your team acts on the errors it surfaces. A server that reports cleanly but is ignored is worse than no server at all, because it creates false confidence. The architecture decision that matters in 2027 is not which fork wins; it is whether your team treats open, pinned, CI-verified tooling as a first-class part of the codebase. Teams that do will move between editors without friction. Teams that do not will keep hitting the same licensing wall every time their tools change.
