NSTextAttachment.character symbol suddenly not available anymore resulting in compiler error

I published the latest update of my AppKit app in September with macOS 26.0.

I just wanted to create a new update, but compiling on macOS 26.4 now fails because of the symbol NSTextAttachment.character which is referenced in my code. The error is

Type 'NSTextAttachment' has no member 'character'

I've never experienced before that a symbol suddenly is not available anymore without even a deprecation notice from one OS release to the next, let alone a minor release. Is this a bug in macOS or Xcode, or should I start worrying about symbols becoming unavailable anytime?

NSTextAttachment.character symbol suddenly not available anymore resulting in compiler error
 
 
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