What probably matters to youSection of the release
What
Messages sent to Claude can carry file attachments. Two changes affect how those messages are handled:
A new system message type, file_attachments_missing, reports which attachments on an incoming message did not arrive. For each file it gives a reason: download, too_large, write, no_token, not_finished or count_cap. One finding says only Claude Code Remote workers send it. The SDK (the kit for building programs on top of Claude Code) treats it like other informational notices such as instruction_size_warning.
When messages are waiting in a queue, Claude Code sometimes combines them into one. Queued messages that have file attachments and are not set to ask Claude a question (shouldQuery false) are no longer combined.
Why
Programs built on the SDK may start receiving the new message type and can tell users which files did not arrive and why. Not combining queued messages that have attachments keeps each attachment with its own message.
