What
MCP servers can now deliver skills (slash commands) as downloadable tar.gz or zip archive bundles. Claude Code fetches, validates, and unpacks the archive, then registers its SKILL.md as a command — all transparently.
Usage
(Automatic — no user action required. Archive skills appear in the command list
alongside regular MCP skills once the server is connected.)Details
- Archives are fetched via the MCP
resources/readprotocol. - Supported formats:
application/gzip/application/x-gzip(tar.gz) andapplication/zip. - Cached by content hash or declared
digestfield; subsequent connections to the same server skip re-downloading if nothing changed. - Hard limits enforced: maximum archive size, maximum file count, maximum uncompressed size.
- Security: rejects path traversal entries, symlinks/hardlinks, sparse/GNU-extension tar entries, base-256 numeric fields, and entries that alias the same disk path under case-folding or dot-segment normalization.
- Requires the MCP server to declare a
digestor the archive's SHA-256 to be consistent between calls. - On load, shows progress message: "Downloading skill archive from \<server\>".
Evidence
Archive fetch and extraction (search for "Downloading skill archive from") — WUd() at line ~324105; tar parser (search for "tar archive contains an unsafe entry") — YZi at line ~323530
Strings lifted out of the shipped bundle, so the claim above can be checked against them.