Draw by insufficient material not implemented!

I lost on time when opponent had only K + B. This should be a draw. I can't play on Lichess if not the correct rules are implemented.

Draw by insufficient material is implemented. However, "insufficient material" is defined like this: there must not be a single sequence of moves that could lead to a win.

That means, if there exists a sequence that could lead to white getting checkmated, it's not a draw by insufficient material. And such sequences do exist, here is an example:

61. a5 Ke7 62. a6 Kf8 63. a7 Ke7 64. a8=B Kf8 65. Kg4 Ke8 66. Kh5 Kf8 67. Kh6 Ke8 68. Kh7 Kf8 69. d6 Ke8 70. Kh8 Kf8 71. Be4 Bxe3 72. Bh7 Bd4#

When your opponent has only King and one Bishop left, it's only a draw if you don't have any pieces left either - this is because there are still possible positions you could get yourself into (although not forced, but that doesn't matter) where your opponent could theoretically mate you with only king and bishop due to your piece blocking your king.

@Lygodactylus Playing with an increment, playing with more time available, or playing faster would prevent situations like this. Try the 180+180 time control.

So, If I lose all my time and my opponent only has the King, Lichess will put that it is a draw?

Yes, a lone king cannot checkmate.

Well, lichess uses the „correct rules“, others don‘t. Wanna see how mate is possible with „insufficient material“?

@Sarg0n please demonstrate a mate by black where white does not promote the a pawn to the bishop. @ProgramFOX has already shown this one.

In the black corner Kh8, Nh7 - Kf7, Bg7#

@Sarg0n you are right! @Lygodactylus as white was in a dead lost and completely resignable position and if he didn't lose on time, he would have been mated by force if he faced you in this position.