validMentionPrecedingChars top-level constant

String const validMentionPrecedingChars

The character that may precede a mention.

A mention is only recognized at the start of the input or when it is not preceded by a "word continuation" character. This mirrors twitter-text's validMentionPrecedingChars after dropping the dead (?:RT|rt):? clause.

The previous implementation kept the residual second alternative |(?:^|[^a-zA-Z0-9_+~.-]) (the left-over prefix of the removed RT: branch). Because it was OR-ed in, it made the whole group match after virtually any character (e.g. hi!@alice.bsky.social), which does not match the official behavior. Removing that residual leaves the single, correct alternative.

Implementation

const validMentionPrecedingChars = r'(?:^|[^a-zA-Z0-9_!#$%&*@＠])';