What is the Mittens chess bot?

The chess community is enthralled by a feline mystery: Chess.com released a new slate of bot profiles to play against, and one of them is most definitely not like the others. Scaredy Cat, rated 800, Angry Cat, rated 1000, Mr. Grumpers, rated 1200, and Catspurrov, rated 1400, behave just how you would expect them to. But then there’s Mittens, rated 1 – and there’s more to her than meets the eye.

Playing against Mittens will quickly make you realize that she is, in fact, incredibly strong, crushing opponents left and right in spectacular fashion. Apart from playing far beyond the level of most (if not all) human players, Mittens also has a devious little personality—at least based on the little chat lines she dishes out during the games:

Mittens chess bot chat lines

“Meow! I like chess, hehehe.”

“I exist at this chess board through all times and realities. Hehehe. Meow.”

“*ominously* All chess players eventually crumble under my mighty paws… I mean, meow! Hehehe.”

“Meow. I am become Mittens, the destroyer of kings. Hehehe.”

“Meow. Fate has brought you here, but I live here through all the time and space forever. Hehehe.”

“I am a tiger and you are in the jungle I call eternity. Hehehe.”

“The light that burns twice as bright burns half as long, hehehe. You are not long for this game.”

“We will exist playing this game against each other forever. Through all eternities and realities. Hehehehe. Meow.”

“*Knocks queen onto the floor* Your queen is gone. Hehehehe.”

“Meow. That looks like a check. Hehehehe.”

“*purring noise* A new queen! Hehehe.”

(after 40 moves) “You have triumphed in existing for longer than many before you. Hehehe. Meow.”

(after 100 moves) “A worthy adversary. I bow at finally meeting one. Meow. Hehehe.”

“The game ends soon. Do not grow weary, for I will soon triumph…Meow! Hehehehe.”

If you can clinch a draw, like Hikaru did, this is your reward:

“Draw. The prophecy must not be fulfilled. Hehehe.”

And, should you defeat her, likely with the assistance of Stockfish:

“WHAT???? HOW!!!!??? YOU CHEA- I mean… meow! Hehehehehehehehehehehehehehehehehehehehe-“

What is the real rating of the Mittens chat bot?

So what is Mittens’ rating? The chess.com announcement post only gives a question mark and a one-line description: “Mittens loves chess… But how good is she?”

It seems like she’s around the 3200-3500 rating range (in Chess.com terms, where the best human players, like Magnus Carlsen and Hikaru Nakamura, sport a 3000-3100 rating in the faster formats), as evidenced by her victories over the site’s otherwise strongest, 3200-rated bots, and her defeat to Stockfish 15, which is currently rated around 3700.

However, some have also suggested that the bot doesn’t actually play optimally but keeps a steady but not massive advantage, sometimes missing optimal or outright winning moves, as in this game against Nakamura:

2356-rated IM Eric Rosen also had good chances against the adorable machine:

Later, Dutch grandmaster Benjamin Bok scored an impressive victory over the cat after a deep positional sacrifice:

As the days went by, more and more players found a way to beat Mittens, even some lower-rated content creators like Nemo “akaNemsko” Zhou. Later, Hikaru speculated based on inside sources that the chess.com team turns Mittens’ rating and play strength up and down behind the scenes, making matters even more inscrutable.

Some have speculated that the bot is running Komodo Dragon 3, a different chess engine with slightly different properties than the almighty Stockfish. It remains to be seen whether chess.com will ever reveal what’s going on with the mysterious cat, or if the community will be able to figure it out on its own.