You'll noticeTier: how much it should matter to you
1Useful: my rating, 1 to 5
1Signal: worth watching, 1 to 5
MCPArea: what it touches
ImprovementsKind: in v2.1.321,
ImprovementsSection of the release
What
MCP servers are add-on programs that give Claude Code extra tools, and some of those tools take files. When Claude Code declines to send a file, its error now says "Claude Code didn't send any file or run the tool".
Claude Code now also refuses to attach a file whose name contains a line break or another control character (an invisible character that controls layout rather than showing as text). The error says so. Before, the error mentioned only characters that change the direction of text.
Why
The errors now state plainly that nothing was sent and nothing ran, so you know what happened when an upload is refused.
