sympy fails to build with Python 3.14.0a6.

_________________________________ test_custom1 _________________________________
[gw2] linux -- Python 3.14.0 /usr/bin/python3
sympy/parsing/tests/test_custom_latex.py:41: in test_custom1
    parser = init_custom_parser(modification1)
sympy/parsing/tests/test_custom_latex.py:34: in init_custom_parser
    parser = LarkLaTeXParser(grammar_file=f.name, transformer=transformer)
sympy/parsing/latex/lark/latex_parser.py:52: in __init__
    self.parser = _lark.Lark(
/usr/lib/python3.14/site-packages/lark/lark.py:439: in __init__
    self.parser = self._build_parser()
/usr/lib/python3.14/site-packages/lark/lark.py:485: in _build_parser
    return _construct_parsing_frontend(
/usr/lib/python3.14/site-packages/lark/parser_frontends.py:257: in _construct_parsing_frontend
    return ParsingFrontend(lexer_conf, parser_conf, options)
/usr/lib/python3.14/site-packages/lark/parser_frontends.py:61: in __init__
    self.parser = create_parser(lexer_conf, parser_conf, options)
/usr/lib/python3.14/site-packages/lark/parser_frontends.py:215: in create_earley_parser
    return f(lexer_conf, parser_conf, resolve_ambiguity=resolve_ambiguity,
/usr/lib/python3.14/site-packages/lark/parser_frontends.py:193: in create_earley_parser__dynamic
    return xearley.Parser(lexer_conf, parser_conf, earley_matcher.match, **kw)
/usr/lib/python3.14/site-packages/lark/parsers/xearley.py:34: in __init__
    BaseParser.__init__(self, lexer_conf, parser_conf, term_matcher, resolve_ambiguity,
/usr/lib/python3.14/site-packages/lark/parsers/earley.py:35: in __init__
    analysis = GrammarAnalyzer(parser_conf)
/usr/lib/python3.14/site-packages/lark/parsers/grammar_analysis.py:158: in __init__
    raise GrammarError("Using an undefined rule: %s" % sym)
E   lark.exceptions.GrammarError: Using an undefined rule: NonTerminal('latex_string')
_________________________________ test_custom2 _________________________________
[gw2] linux -- Python 3.14.0 /usr/bin/python3
sympy/parsing/tests/test_custom_latex.py:58: in test_custom2
    parser = init_custom_parser(modification2, CustomTransformer)
sympy/parsing/tests/test_custom_latex.py:34: in init_custom_parser
    parser = LarkLaTeXParser(grammar_file=f.name, transformer=transformer)
sympy/parsing/latex/lark/latex_parser.py:52: in __init__
    self.parser = _lark.Lark(
/usr/lib/python3.14/site-packages/lark/lark.py:439: in __init__
    self.parser = self._build_parser()
/usr/lib/python3.14/site-packages/lark/lark.py:485: in _build_parser
    return _construct_parsing_frontend(
/usr/lib/python3.14/site-packages/lark/parser_frontends.py:257: in _construct_parsing_frontend
    return ParsingFrontend(lexer_conf, parser_conf, options)
/usr/lib/python3.14/site-packages/lark/parser_frontends.py:61: in __init__
    self.parser = create_parser(lexer_conf, parser_conf, options)
/usr/lib/python3.14/site-packages/lark/parser_frontends.py:215: in create_earley_parser
    return f(lexer_conf, parser_conf, resolve_ambiguity=resolve_ambiguity,
/usr/lib/python3.14/site-packages/lark/parser_frontends.py:193: in create_earley_parser__dynamic
    return xearley.Parser(lexer_conf, parser_conf, earley_matcher.match, **kw)
/usr/lib/python3.14/site-packages/lark/parsers/xearley.py:34: in __init__
    BaseParser.__init__(self, lexer_conf, parser_conf, term_matcher, resolve_ambiguity,
/usr/lib/python3.14/site-packages/lark/parsers/earley.py:35: in __init__
    analysis = GrammarAnalyzer(parser_conf)
/usr/lib/python3.14/site-packages/lark/parsers/grammar_analysis.py:158: in __init__
    raise GrammarError("Using an undefined rule: %s" % sym)
E   lark.exceptions.GrammarError: Using an undefined rule: NonTerminal('latex_string')

https://docs.python.org/3.14/whatsnew/3.14.html

For the build logs, see:
https://copr-be.cloud.fedoraproject.org/results/@python/python3.14/fedora-rawhide-x86_64/08783586-sympy/

For all our attempts to build sympy with Python 3.14, see:
https://copr.fedorainfracloud.org/coprs/g/python/python3.14/package/sympy/

Testing and mass rebuild of packages is happening in copr.
You can follow these instructions to test locally in mock if your package builds with Python 3.14:
https://copr.fedorainfracloud.org/coprs/g/python/python3.14/

Let us know here if you have any questions.

Python 3.14 is planned to be included in Fedora 43.
To make that update smoother, we're building Fedora packages with all pre-releases of Python 3.14.
A build failure prevents us from testing all dependent packages (transitive [Build]Requires),
so if this package is required a lot, it's important for us to get it fixed soon.

We'd appreciate help from the people who know this package best,
but if you don't want to work on this now, let us know so we can try to work around it on our side.