Now, after conflict_handler and argument_default have been documented, we can deprecate prefix_chars. @savannahostrowski, are you interesting? We should just add a runtime warning in the _ArgumentGroup constructor, test, and documentation (the deprecated instruction and something in What's New).

Originally posted by @serhiy-storchaka in #89819 (comment)

https://docs.python.org/3/library/argparse.html#argument-groups

Linked PRs

• gh-125542: Deprecate prefix_chars in ArgumentParser.add_argument_group #125563