Does VSCodium support proprietary Microsoft Marketplace extensions via product.json modification?

Direct Answer

VSCodium does not reliably support proprietary Microsoft Marketplace extensions, even after modifying product.json. The primary barrier is licensing enforcement within the extensions themselves, not just gallery configuration.

Confirmed Behavior vs. Likely Explanation

The product.json file in VSCodium defines the extensionsGallery endpoint, which defaults to Open VSX Registry. While technically possible to modify this to point to Microsoft Marketplace, proprietary extensions like C# Dev Kit and Live Share contain build-detection logic that actively blocks functionality when running on non-Microsoft builds.

This means that even if you successfully redirect the gallery and install the extension, activation will likely fail during runtime. The extension checks for specific build identifiers that only official VS Code installations possess.

Extensions Known to Fail

• C# Dev Kit - Requires official Microsoft VS Code build
• Live Share - Includes Microsoft-specific licensing checks
• IntelliSense for Sorbet - May have similar build restrictions

Stable Management Method

For extensions that do work with VSCodium:

1. Backup product.json - Location varies by OS: ~/.config/vscodium (Linux), ~/Library/Application Support/vscodium (macOS), %APPDATA%\vscodium (Windows)
2. Modify extensionsGallery to point to Microsoft endpoint if needed
3. Script reapplication - Create a post-update script to restore changes
4. Monitor releases - Check VSCodium changelogs for product.json handling changes

Important Caveats

Licensing Warning: Microsoft Marketplace extension terms may prohibit use in VSCodium builds. Always review individual extension licenses before attempting configuration changes.

Update Risk: VSCodium updates may overwrite product.json, requiring manual restoration or automated scripts.

Verification Steps

To determine if a specific extension will work:

• Check Open VSX for equivalent extensions
• Review extension package contents for build-checking code
• Test functionality after installation - look for activation errors in output logs

Missing Diagnostic Detail

What specific extension are you attempting to use, and what error messages appear in the VSCodium output log when it fails to activate? This will help determine if the issue is gallery configuration, licensing, or something else entirely.