Claude Desktop crashes on invalid semver in manifest version field

[IvanK-Nitro]

Description

Claude Desktop crashes with a fatal error when an installed MCPB extension has a version string that doesn't conform to semver (3 segments). The entire app becomes unusable — not just the extension.

Steps to Reproduce

1. Create an .mcpb bundle with a 4-segment version in manifest.json:

   {
     "version": "2024.03.31.01"
   }

2. Open the .mcpb file with Claude Desktop — the extension installs but the app crashes
3. On every subsequent launch, the app crashes again before the UI loads
4. The user cannot uninstall the broken extension from the UI
5. Installing a corrected bundle (valid semver like "0.1.0") also fails because the old extension crashes the app first

Expected Behavior

• Claude Desktop should validate the version string and show a user-friendly error for that extension, not crash the entire app
• A broken extension should not prevent the app from starting or block installation of other extensions

Actual Behavior

The app throws a fatal error boundary crash:

[error] TypeError: Invalid Version: 2024.03.31.01
[error] [BOOTSTRAP] Fatal error boundary triggered {"errorMessage":"Invalid Version: 2024.03.31.01","errorCode":"19FYAIU"}

Workaround

Manually delete the broken extension from the filesystem:

rm -rf ~/Library/Application\ Support/Claude/Claude\ Extensions/<extension-folder>
rm -f ~/Library/Application\ Support/Claude/Claude\ Extensions\ Settings/<extension-folder>.json

Then restart Claude Desktop and install the corrected bundle.

Environment

• macOS (Apple Silicon)
• Claude Desktop (latest as of 2026-04-14)
• manifest_version: "0.4"

Notes

• The mcpb validate CLI does not currently flag non-semver version strings — adding validation there would catch this before distribution
• A screen recording of the crash is available if needed