When the CPython interpreter crashes - recent history entries are lost. An easy reproducer (on any Linux):

$ ulimit -v $((1024*256))
$ pip install -q gmpy2
$ python  # started with empty history
Python 3.14.0a2+ (heads/main:e2713409cf, Dec  2 2024, 07:50:36) [GCC 12.2.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> from gmpy2 import mpz
>>> mpz(2222222222222211111111122222222222222)**33322222
GNU MP: Cannot allocate memory (size=503998640)
Aborted
$ python  # history is empty, again :(
...

That "works" both in the old repl and in the new repl. Sometimes you even can't recover all session from the terminal screen.

IMO, if it's a feature - it's a misfeature. I would expect, that all entered input will be preserved in the history. Or such behavior can be optionally turned on. BTW, this feature "doesn't work" in the IPython shell.

Linked PRs

• gh-127495: Append to history file after every statement in PyREPL #132294