Vexing Bauble

• WWizards of the Coast2024-06-07
  Official Ruling
  If a spell is cast with an alternative cost that includes mana (such as flashback), Vexing Bauble's first ability won't trigger and won't counter that spell. Similarly, if a spell is cast without paying its mana cost, but the player did pay mana for additional costs such as from kicker or from Thorn of Amethyst, Vexing Bauble's first ability won't trigger and won't counter that spell.
• WWizards of the Coast2024-06-07
  Official Ruling
  Players may cast spells that they know Vexing Bauble will counter. Any abilities that trigger when spells are cast will still trigger and resolve if appropriate, and any effects that count how many spells are cast will still count those spells if appropriate.

Rulings via Scryfall

• WO
  Wizards of the Coast2024-12-16

  Vexing Bauble was banned in legacy on December 16, 2024. While the inclusion of Vexing Bauble is a rather recent development in the Legacy metagame, it has proven to be a successful and powerful one. With a concerning win rate among decks that include multiple main-deck copies of Vexing Bauble and its inherent strength against a pillar of the format, it has been banned in Legacy. Source: https://magic.wizards.com/en/news/announcements/banned-and-restricted-december-16-2024
• WO
  Wizards of the Coast2024-08-26

  Vexing Bauble was restricted in vintage on August 26, 2024. A player who goes first and can resolve a Vexing Bauble before their opponent takes a turn effectively shuts them out of playing all their cool cards. In the spirit of keeping Vintage about Vintage, Vexing Bauble is restricted. Source: https://magic.wizards.com/en/news/announcements/august-26-2024-banned-and-restricted-announcement