'ms-python.pylance' not found in Open VSX Registry – VSCodium

Direct Answer

There is no supported method to obtain proprietary Microsoft-published extensions such as Pylance for VSCodium without violating the Microsoft Marketplace Terms of Use. The Open VSX Registry cannot host these extensions unless Microsoft chooses to publish them there, and third-party redistribution is prohibited by their licenses. Manually repointing VSCodium to the Microsoft Marketplace endpoint works technically but breaches the terms and is not a compliant workflow.

Why Pylance Is Absent from Open VSX

Pylance is a closed-source, proprietary extension whose license restricts use to official Microsoft Visual Studio products (VS Code, VS Code Insiders, Visual Studio IDE). VSCodium is a community build of the open-source Code-OSS repository and is not a licensed Microsoft product. Microsoft publishes Pylance, C# DevKit, the .NET debugger, and several other extensions exclusively to the Visual Studio Marketplace; they do not appear in Open VSX because Microsoft has not uploaded them there.

Open VSX Cannot Be Extended to Host Proprietary Microsoft Extensions

Open VSX only hosts extensions that publishers (or the community under permissive licenses) have explicitly uploaded. Because Pylance's license forbids redistribution outside Microsoft products, no third party can legally mirror it to Open VSX. The only way Microsoft extensions appear on Open VSX is if Microsoft itself publishes them there—something it has not done for Pylance or its other proprietary tooling.

Implications of Manually Adding the Microsoft Marketplace Endpoint

Editing product.json to point at the Microsoft Marketplace makes the extensions installable, but:

• License violation: The Marketplace Terms of Use state offerings are intended only for in-scope Microsoft products.
• Validation differences: Extensions from the Microsoft Marketplace carry Microsoft signatures and may enforce product checks that fail or behave unexpectedly in VSCodium.
• Telemetry: Microsoft extensions may still send telemetry governed by Microsoft's privacy statements, independent of VSCodium's telemetry settings.
• Unsupported updates: Auto-update behavior can change between releases; there is no guarantee of continued compatibility.

Compliant Alternative: Use basedpyright with the Open-Source Python Extension

The open-source ms-python.python extension (available on Open VSX) provides editing, debugging, and test support. For the language-server features Pylance provides—type checking, completions, inlay hints—use basedpyright, a community-maintained fork of Pyright (the open-source engine underlying Pylance) published to Open VSX.

1. Install ms-python.python from Open VSX (Extensions view → search "Python").
2. Install basedpyright from Open VSX (search "basedpyright").
3. In settings.json, set "python.languageServer": "Pylance" is not available; instead ensure "python.analysis.typeCheckingMode": "basic" (or "strict") and basedpyright will activate automatically for .py files.

basedpyright delivers comparable type checking, diagnostics, and navigation. It may lag behind Pylance in certain inlay hints or notebook integration, but it is the closest functional substitute that respects licensing.

One Diagnostic Detail Needed

Which specific Microsoft-published extensions are you trying to use? Some (e.g., the base Python extension, Jupyter, Docker) are open-source and already on Open VSX; others (Pylance, C# DevKit, .NET MAUI) are proprietary. Knowing the exact list lets me confirm which have compliant Open VSX equivalents and which require a different toolchain.