Meta's Pyrefly sabotages competing Python extensions without telling you

FFossAndFurious about 8 hours ago 23 commentsRead Article on github.com

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Discussion (23 Comments)Read Original on HackerNews

kinto•about 4 hours ago

hi - pyrefly developer here. this was an oversight made by me a while ago during our beta launch.

thanks for reporting. we have a full response [here](https://github.com/facebook/pyrefly/issues/3292#issuecomment...) in the github issue

FossAndFurious•about 8 hours ago

Pyrefly is Meta's new Python type checker and VS Code extension, released earlier this year. While auditing the VSIX before installing it, I found that on activation it silently writes `disableLanguageServices = true` to the user's global settings for three named extensions: basedpyright, windsurfpyright, and cursorpyright.

The write uses `ConfigurationTarget.Global`, so it affects all workspaces. There is no `deactivate()` cleanup, so the setting persists after Pyrefly is uninstalled.

This was verified by live reproduction: installed Pyrefly alongside basedpyright, opened a Python file, and observed the key appear in `settings.json`. Uninstalled Pyrefly — key remained, basedpyright still broken.

The code is in plain TypeScript in the public repo (`lsp/src/extension-interop.ts`), added December 2025. This isn't obfuscated or hidden — it just hasn't been noticed.

Bug report with full details, source references, and reproduction steps: https://github.com/facebook/pyrefly/issues/3292

The fix is straightforward: ask the user before touching settings they didn't set, and restore them in `deactivate()`.

IceDane•about 7 hours ago

Have you just completely retired your brain in favor of a bidirectional pipe to an LLM?

Esophagus4•about 6 hours ago

I’ll answer that once my brain’s usage limit resets at 10:30pm

zgeor•about 2 hours ago

Turn on extra usage. But dont forget to set a limit!

PufPufPuf•about 7 hours ago

"it's not X, m-dash, it's Y"

refulgentis•about 7 hours ago

A, B, C.

A, B, C — D.

queenkjuul•about 4 hours ago

I'm confused, I'm looking for the emdash key on my phone and can't find it--how do you type yours?

agency•about 4 hours ago

You press and hold the hyphen key on iPhone — like this! And I'm a human :)

jaen•about 7 hours ago

Noticed this myself as a VSCode-derivative user.

But I think this is just because having multiple Python extensions enabled generally breaks the UX...

Since VSCode doesn't really have a nice way for multiple language extensions to cooperate, this looks like just a quick hack to make the initial UX better, unlikely to be "malicious".

EDIT: Silent downvotes, really? Prejudice is strong here...

pityJuke•about 7 hours ago

Could they not gate this behind a notification on install?

Lihh27•about 6 hours ago

Disabling conflicting extensions, sure. Writing to global settings and leaving the mess behind after uninstall is not the same thing.

axus•about 7 hours ago

Never attribute to malice what can be explained by vibe-coding

PufPufPuf•about 7 hours ago

Fixed title: Pyrefly automatically disables conflicting extensions on installation.

That's a convenient thing to do: if user installs Pyrefly, they probably want to use Pyrefly. Everyone likes a good outrage against Meta, but this is a nothingburger.

NewsaHackO•about 7 hours ago

Yeah, I think the OP is overreacting. I am pretty sure it even says it in the initial installation instructions and gives a clear reason why it interferes with other language servers. In the "Features" section of the VsCodium extensions "Adds language features from Pyrefly's analysis like go-to definition, hover, etc. (full list here) and disables Pylance completely (VSCode's built-in Python extension)". I suspect there is an element of LLM-sycophancy-driven activism here.

d_sem•about 7 hours ago

OP is an LLM.

LaurensBER•about 7 hours ago

Agreed, it should definitely be documented and undone on uninstall but the action itself is reasonable.

I spent some time figuring out how to disable the default language server after installing Ty.

hamandcheese•about 7 hours ago

> but the action itself is reasonable.

I'm not outraged (the intentions were probably good), but I also strongly disagree. Don't touch my config without my consent.

OutOfHere•about 6 hours ago

Speaking of sabotage, Microsoft's SwiftKey keyboard app sabotages the use of a competing search engine (DuckDuckGo) in Firefox in Android for me. When typing a multi-word quoted search phrase, it doesn't allow it to be typed correctly.

3darl•about 7 hours ago

This is typical in the Python space. Windows is also broken after installing Conda.

Given that now one has to pray that one does not get Shai Hulud when using PyPI, the best thing Meta could do is switch Instagram to PHP/Hack and PyTorch back to Lua (or Haskell or whatever).

gavmor•about 6 hours ago

Wow, I wasn't going to say it, but I was thinking it—python libraries and clobbering my environment? Name a more iconic duo.

jqpabc123•about 7 hours ago

Once again; if it has a Meta label, it most likely has added "features" you may not expect ... or want.

gavmor•about 6 hours ago

From the people who brought you "move fast and break things."