Under the hood
Relayed session-inbox messages can now include attachments
What
Messages relayed through the session inbox (used for things like Slack messages reaching a session) can now carry attachments. The message event builder accepts an optional attachments argument and includes it in the message data sent to the session. The attachments field has also been added to the list of fields treated as untrusted, alongside the existing body, sender_display, and slack_permalink fields.
Why
This lets relayed messages carry file or media attachments rather than just text, while still treating that attachment data as untrusted input like the rest of the relayed message.