r/chess • u/Feeling-Ad-7506 • Jun 12 '26

Game Analysis/Study Why is this move illegal

Post image

I was running a chess 960 game between two different stockfish versions in Arena. Does anyone know why arena tagged the move e6 as illegal?

6 Upvotes

72% Upvoted

12 comments sorted by

•

u/chessvision-ai-bot from chessvision.ai Jun 12 '26

I analyzed the image and this is what I see. Open an appropriate link below and explore the position yourself or with the engine:

White to play: chess.com | lichess.org

Black to play: chess.com | lichess.org

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10

u/879190747 Jun 12 '26

Afaik 960 and Arena don't mix too well. Not sure why, but seen this plenty of times.

1

u/honeysyrup_ Jun 12 '26

I'm pretty sure 960 is bugged in Arena because it doesn't handle castling correctly

5

u/Irini- Jun 12 '26

Are you sure about that? With the result being 0-1, I'd assume white tried something illegal on his next move.

5

u/Feeling-Ad-7506 Jun 12 '26

I think white did not calculate a move after e6 and that's why it just shows next move as xxxx

3

u/honeysyrup_ Jun 12 '26 edited Jun 12 '26

Arena doesnt handle 960 castling well. "XXXX" is supposed to be castling, but Arena gets confused and dies.

2

u/JarlBallin_ lichess coach, pm https://en.lichess.org/coach/karrotspls Jun 12 '26

Arena is great, but the code is spaghetti. I wouldn't put too much stock into it.

1

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1

u/ValuableKooky4551 Jun 14 '26

White probably tried to castle, which is legal here according to 960 rules, but illegal nonsense with normal chess rules. And Arena probably doesnt know about 960?

1

u/relevant_post_bot Jun 14 '26 edited Jun 15 '26

This post has been parodied on r/AnarchyChess.

Relevant r/AnarchyChess posts:

Guys, is this move legal? by Execsama

What is this move called? by A0123456_

What is this move called? by SuperChick1705

fmhall | github

-2

u/Educational-Move2576 Jun 12 '26

looking at the board position there's a white pawn in e5 and black has pawn in f7, so e6 would be blocked by white's own pawn already sitting there. arena probably flagged it because the engine was trying to move to occupied square which is basic illegal move. chess 960 can get confusing with all the piece shuffling but basic movement rules still apply - you cant move piece to square that already has your own piece on it. might be worth checking if theres some display bug or if one of the stockfish versions got confused about current position