Artifact and skill file entries can now be an object specifying a source path and content type, not just a plain path string
What
When creating or publishing an Artifact or Skill, the files map used to only accept a plain path string for each file. It now also accepts an object with a from field (the source path) and a contentType field, letting a publish call specify a MIME/content type per uploaded file instead of only where it comes from.
The internal handler that admits these files, checking things like path traversal and size limits, was updated to read the source path from from when a file entry uses this new object form, rather than assuming it's always a bare string.
Why
This lets publishers control the content type of individual uploaded files (for example, forcing a file to be treated as plain text or a specific format) rather than relying on automatic detection.
The entry above is what we published on the day. These lines were added later, as Anthropic's own pages caught up, and they sit beside the original rather than replacing it.
.contentType("text/markdown")build-with-claude/skills-guide see the edit
Anthropic's documentation has since written up contentType, on skills-guide.