Want to understand the mechanism of cheat detection

Accept that cheat detected literally means cheat detected, and that it proves the player used Lichess analysis for an ongoing game. Me and glbert have the experience of how things work on lichess (in fact glbert taught me a few years ago), you dont

@rr19042003 said in #10:

does it mean that
1.cheating has been committed by the player?

yes.

Or 2. The positions in tactical puzzle and actual game were similar and hence

nope. as said earlier, once you start the game, lichess turns off the engine in the puzzle tab. without engine, no cheat detected. you have to actively go back to the other tab, and turn the engine on. and the position there cannot be "similar". it has to literally be a position that occurred in the game. you will probably understand that this is very unlikely. but even if it were to happen, turning on the engine on a position that occurred in the game would be cheating anyway.

here is what most likely has happened, in my experience:

1. your friend simply cheated.
2. they did not want to admit it, so they decided to lie right to your face.
3. they have no idea how "cheat detected" actually works, so they had to come up with a scenario on the fly.
4. since they have no idea how it works, the scenario they came up with made no sense whatsoever.
5. we are telling you so in the forums, but you will not believe us, because you trust your friend over us.
6. i am going to tell you to go to lichess.dev, and try to do exactly what your friend claims to have done. your friend should show you the puzzle, he can go to his puzzle history. replay that game on lichess.dev, while the engine is running on the puzzle. watch what happens. which will be:
7. nothing. because your friend was lying.

Thanks for the suggestions @glbert
Your scenarios look very likely to have happened. Lets see. Thanks for the detailed explanations. I actually dont have much of coding knowledge but no problem, I will also look into it. Once again thanks for the points.

I think there are some players who "allow" themselves to use analysis during the openings because they feel that's "known" theory and therefore open to all.

In correspondence chess it often is (not sure about the correspondence games on this site, I don't play them). In live games it never is, and that definitely includes this site.

It is also illegal to have a printed sheet of paper in front of you with lines on it. By the way, whilst in OTB it would obviously be detected, I wonder if any players have ever tried to cheat with some "encrypted" way of bringing their theory in with them? Someone very clever would find a way that, say, some dot patterns on a garment would actually be their lines...

In any case we can assume the member was lying and that he was referring to live opening analysis. (Would you get "cheat detected" looking at the lines without the evaluations on, because ideally that would trigger it too)

@glbert one more thing to ask
I completely accept that cheating may have happened in opening 8 moves. (Though he played same Reti opening almost 50 times against me) but okay, you r experienced so it would be foolish not to take your consideration.
But why does lichess not give a temporary ban of 1-2 days or a permanent account ban for these IDs?
I mean why is the leniency shown to them just by deducting rating?
According to your info, tab has been switched during the game and he has explicitly tried to make engine 'ON' due to which the message came.
Then why is this not taken as an action of a permanent ban? Please make me understand.
Thanks

was someone else watching him play?

@rr19042003 said in #15:

@glbert one more thing to ask
I completely accept that cheating may have happened in opening 8 moves. (Though he played same Reti opening almost 50 times against me) but okay, you r experienced so it would be foolish not to take your consideration.
But why does lichess not give a temporary ban of 1-2 days or a permanent account ban for these IDs?
I mean why is the leniency shown to them just by deducting rating?
According to your info, tab has been switched during the game and he has explicitly tried to make engine 'ON' due to which the message came.
Then why is this not taken as an action of a permanent ban? Please make me understand.
Thanks

If you do this multiple times, then there's no more leniency and you're marked.

First time is pardoned because Lichess acknowledges the rare exceptions in which where this happens without real intention to cheat, e.g. a coach playing with a student

indeed. the first time(s?) you get a slap on the wrist, it's lichess's way of saying: don't be silly. also, nothing much really happened at that point, because it mainly means that your opponent was trying to cheat, but did not succeed.
i expect anyone who lost a game like this ends up on some sort of watch list though, for later review. because there's definitely people who just move on to different methods.

@glbert said in #4:

that scenario would not trigger cheat detected.

Wow that's one of my fears, glad to now that even if I forgot an analysis of a puzzle (in another tab) that will not count as cheating

Few question about the fact that engine is turned off automatically and that user have to analyze a position that occurs in game to be considered cheating (I like corner cases by the way).

I expect Lichess use a command form server to all tabs opened by an user (websocket?) to shutdown engine. But if for some reason the websocket is reconnecting maybe you find an engine on later, like the user activated it? (even if the user didn't and simply the command didn't reach a specific tab).

Another corner case that cross my mind, what if an user that would like to cheat switch on an engine and start analysing a position that had occurred, but is not actual anymore.
It will raise a red flag? Because IMHO it should

@earlpurple said in #14:

[...] In correspondence chess it often is (not sure about the correspondence games on this site, I don't play them). In live games it never is, and that definitely includes this site. [...]

Here's the chart for engine, opening-book or endgame-tablebase usage on Lichess:
https://lichess.org/how-to-cheat?key=fair-play