Direct Answers
1. Switching to Microsoft Marketplace without editing product.json: No documented, supported procedure exists. VSCodium's build process hard-codes the extensionsGallery configuration to Open VSX endpoints. The only way to use the Microsoft Marketplace UI is to modify product.json or use an unofficial patch, both of which may break signature verification, auto-updates, or conflict with VSCodium's telemetry-free policy.
2. Permanently unavailable extensions due to licensing: There is no authoritative public list. Publishers decide per extension whether to publish to Open VSX. Popular extensions like ms-vscode.cpptools, ms-python.python (Microsoft-authored versions), and some Azure/DevOps tooling are Microsoft Marketplace-only, but availability changes when publishers add or remove entries. You must check each extension ID on Open VSX directly.
3. Version lag and API compatibility: VSCodium typically trails upstream VS Code by days to weeks. Extensions that declare engines.vscode requiring newly released APIs will fail to activate or show compatibility warnings until VSCodium rebases onto the matching VS Code commit. The extension host enforces this version check at runtime.
Confirmed Facts vs. Likely Explanations
| Confirmed | Likely / Requires Verification |
|---|
product.json points to Open VSX; no UI setting to change it | Editing product.json to Microsoft endpoints works but may break updates |
Manual .vsix install via "Install from VSIX" works | Manual installs bypass license checks; may violate extension terms |
Extension host enforces engines.vscode against running version | Exact lag varies per release; not strictly tied to major version number |
| No central list of Microsoft-exclusive extensions | Publisher decisions change; current check required per extension |
Practical Steps for Users
- Verify your gallery configuration: Open
product.json in your VSCodium install directory and confirm extensionsGallery.serviceUrl and itemUrl reference open-vsx.org. - Check extension availability: Search the extension ID on Open VSX. If absent, it is not discoverable via the default UI.
- Install Microsoft-exclusive extensions manually: Download the
.vsix from Microsoft Marketplace (browser), then in VSCodium Extensions view → ⋮ menu → "Install from VSIX...". Note: no automatic updates; repeat for each version. - Assess API compatibility: Compare VSCodium's About version with the upstream VS Code release notes. If an extension requires an API introduced after your VSCodium base commit, it will not activate.
One Diagnostic Detail Needed
Which specific extension IDs are you trying to use? Confirming their presence on Open VSX and their declared engines.vscode range will determine whether manual .vsix install is viable or if you must wait for a VSCodium rebase.
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