Unclear Where Claude Code uses this parser, and so which patterns a user writes are affected, is not stated.
What
Claude Code has its own parser for regular expressions, which are text patterns used to match strings. It was rewritten. It now understands:
- Counted repeats such as
{n,m} - Lookahead groups anywhere in the pattern, not only at the start
- Named groups
Before, it handled only the *, + and ? repeats and a lookahead at the very start of a pattern.
When it cannot handle a pattern, it now gives a specific reason, such as a lookbehind, a back-reference, a flags group, older pattern syntax, or a pattern that is too large.
Why
Patterns that use these features can now be read where they could not before, and a refused pattern now comes with a reason.
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Where Claude Code uses this parser, and so which patterns a user writes are affected, is not stated.