Attachment verification runs only when peer messaging is enabled, which is off by default.
What
When another session sends file attachments, they are now checked before Claude sees them: the attachment list is schema-parsed and capped in count, each path must sit inside the transfer staging directory, must be a regular file, and must match the declared size and hash. Verified files are copied into an uploads directory with owner-only permissions. This runs only with peer messaging enabled.
Details
- A file that fails any check is logged with a
[peer-file-transfer]prefix and surfaces as a notice, rather than being attached silently.
Evidence
transfer path is outside the file-transfer spool
Strings lifted out of the shipped bundle, so the claim above can be checked against them.