2028: App Clip payment cards can only be sent over iMessage

App Clip payment cards can only be sent over iMessage. The request included an app_clip part while explicitly requesting SMS or RCS. This is an HTTP 409 error.

• Omit preferred_service — it defaults to iMessage for App Clip cards — or set it to iMessage
• App Clip cards never fall back to SMS/RCS. If the recipient isn’t reachable over iMessage, the send instead fails asynchronously with a message.failed webhook carrying code 4005
• Check iMessage capability before sending

• Sending payment links
• Protocol Selection
• Error Codes