Rename an iMessage group chat with space.group.setName(): 
await space.group.setName("Product launch");
Renaming requires an existing group conversation on a line that supports group metadata. On the free plan, group creation is not included — renaming applies to groups you create on paid or dedicated lines.

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DM display names

For direct messages, set your bot’s display name through the management API or CLI so recipients see a friendly sender: 
sky skyline profile update --display-name "Acme Support"
See Spaces and users for profile and participant resolution.