Teams drag-and-drop upload fails only from macOS screenshot thumbnail / markup window

I’m encountering a reproducible issue with Microsoft Teams file uploads that appears to be specific to the drag-and-drop source on macOS.

Steps to reproduce

1. On macOS, take a screenshot using:
   • Cmd + Shift + 4 or Cmd + Shift + 5
2. When the floating screenshot thumbnail / markup window appears (bottom-right of screen), do not save the file manually
3. Drag the screenshot directly from the floating thumbnail or markup window
4. Drop it into the Teams message compose box in:
   • a 1:1 chat, or
   • a group chat

Result

• Upload gets stuck on Uploading

Environment

• macOS
• Teams Web (Chrome)
• Teams macOS desktop app