Extension Activation Failure: Product ID Mismatch in VSCodium

Short answer

VSCodium rejects extensions that explicitly declare the VS Code product ID ("vscode") in their package.json. There is no built‑in aliasing mechanism; the only reliable fixes are to use a compatible extension version or to modify the extension’s product field to match VSCodium’s ID ("vscode-codium").

Why the mismatch happens

Extensions may include a product or productId key that limits activation to a specific editor. When VSCodium loads such an extension, the extension host compares the declared ID against the editor’s own product ID. If they differ, the host logs an error and skips activation.

How to identify the offending ID

1. Open the extension’s package.json (usually found in ~/.vscode/extensions/publisher.extension-version/package.json).
2. Look for a product or productId key. The value will be something like "vscode" or "vscode-codium".
3. Open VSCodium’s Output panel (Ctrl+Shift+U), select Extension Host, and locate the line that says “Extension activation failed: product ID mismatch” to confirm the mismatch.

Fix #1 – Use a compatible extension version

Many popular extensions are published on the Open VSX Registry with a “codium” variant that removes the hard‑coded product ID. Install the Open VSX version instead of the VS Code marketplace copy:

code --install-extension publisher.extension --channel openvsx

Fix #2 – Patch the extension locally

If a compatible variant isn’t available, you can edit the extension’s package.json to match VSCodium’s ID:

1. Open the file as described above.
2. Replace the value of product (or productId) with "vscode-codium".
3. Restart VSCodium or run Ctrl+Shift+P → Reload Window.

After reloading, the extension should activate normally. If the extension still fails, the extension may rely on other VS Code‑specific APIs that are not available in VSCodium.

Can you alias the product ID?

As of VSCodium 1.78, the editor does not expose a configuration flag or environment variable to map a different product ID. The only documented approach is to use a version of the extension that declares the correct ID or to patch the extension yourself. Community discussions on GitHub suggest that future releases may add a codiumProductId override, but it is not yet implemented.

What to do if you’re unsure

Check the exact value reported in the Output panel. If it shows a mismatch like "vscode" → "vscode-codium", apply the steps above. If the message differs, let us know the exact IDs so we can adjust the recommendation.

Verification checklist

• Output panel shows no "product ID mismatch" after changes.
• Extension’s status in the sidebar changes from Failed to activate to Enabled.
• Reloading the window does not re‑trigger the error.