You'll noticeTier: how much it should matter to you
2Useful: my rating, 1 to 5
2Signal: worth watching, 1 to 5
MCPArea: what it touches
ImprovementsKind: in v2.1.321,
ImprovementsSection of the release
What
MCP servers are add-ons that give Claude extra tools, and some can ask Claude Code to upload files to them. Claude Code now checks those upload requests against a set of rules and rejects ones that are malformed. The rules cover the request's list of uploads and files, the upload method io.modelcontextprotocol/files/upload, and upload targets, which must accept a PUT request.
Why
This is part of Claude Code's support for the MCP files extension, the part of the protocol that lets servers ask for file uploads.
