Under the hood
No documentation found
User messages in the SDK now support an internal file_attachments field
What
The schema for user-role messages used by the Claude Code SDK now accepts an optional file_attachments array. Each entry can include file_uuid, file_name, is_image, sha256, and file_size, matching the shape already used by SDKUserMessageReplay.
Why
This appears intended for remote clients that need to attach files to a prompt, giving them a defined structure for describing attached files alongside a message.
Names in the bundlefile_attachments