What
The Write tool (the tool Claude uses to create or overwrite a file) already renamed a few alternative field names to the ones it expects. It now also recognises a longer list of these alternatives, called aliases:
pathandfileas aliases forfile_pathfile_text,file_content,new_text,body,textandcontentsas aliases forcontent
When the model sends one of these aliases alongside the real field and both hold exactly the same text, the alias is deleted. The result of the call then carries a short note such as "<alias> repeated <field> and was ignored."
Why
A file write that carries the same filename or file text twice under two different names is now cleaned up instead of carrying a redundant field forward. The note in the result shows exactly which field was dropped.