Register an icon for the .mcpb document type in Claude Desktop

[jorisroling]

Summary

On macOS (and Windows), .mcpb bundles show the generic blank-document icon in Finder/Explorer, because no installed application registers the .mcpb UTI / file extension with a document icon.

Why it matters

Claude Desktop is the app that opens and installs .mcpb files, so it would be the natural owner of the file-type icon. Registering the .mcpb document type with a recognizable Claude "extension" icon would give every bundle — from any vendor — a consistent, branded, trustworthy look at rest, and signal "double-click to install into Claude" rather than an anonymous blank page.

Bundle authors have no clean way to brand the type themselves: per-file custom Finder icons (resource fork + SetFile -a C) are fragile and don't survive normal distribution paths (email, re-zipping, etc.), and they only ever brand a single file rather than the type.

Proposed

• macOS: declare the .mcpb document type in Claude Desktop's Info.plist via CFBundleDocumentTypes + an exported UTI with an .icns.
• Windows: register the equivalent file-type association + default icon for .mcpb.

Result: every .mcpb shows a consistent Claude-branded document icon system-wide, independent of who built it.

Joris Röling (p.o.)