The "Oh shit..." moment.

[Eelco de Groot]

Congratulation Eelco, you have correctly shown, that 11..d4!? might be a viable alternative.
I enjoyed it very much, when suddenly 11...d4!? emerged, so i decided to pose this puzzle so everyone had a chance to experience that too.
As promised, i post some preliminary lines:

Thanks! I think it was a nice find!

[pgn][Event "World Chess Championship 2018"] [Site "London"] [Date "2018.11.10"] [Round "2"] [White "Carlsen, Magnus"] [Black "Caruana, Fabiano"] [Result "1/2-1/2"] [WhiteElo "2835"] [BlackElo "2832"] 1.d4 Nf6 2.Nf3 d5 3.c4 e6 4.Nc3 Be7 5.Bf4 O-O 6.e3 c5 7.dxc5 Bxc5 8.Qc2 Nc6 9.a3 Qa5 10.Rd1 Rd8 11.Be2 ( 11.Nd2 d4 12.Nb3 Qb6 13.Na4 Bb4+ 14.axb4 ( 14.Ke2!? ) 14...Qxb4+ 15.Nd2 Qa5 16.Qb3!? ( 16.b3 e5 17.Bg5 Nb4 18.Qc1 Bg4 19.Be2 b5 20.Nb2 Na2 21.Qa1 Bxe2 22.Kxe2 Nc3+ 23.Kf1 Qb4 24.Rc1 Nce4 25.Nxe4 Nxe4 26.Bxd8 Rxd8 27. exd4 Nd2+ 28.Kg1 Nxb3 29.Nd3 Qe7 30.Qc3 Nxc1 31.Qxc1 Rxd4 32.Nb2 Qb4 33.h3 bxc4 34.Kh2 $11 ) 16...e5 17.Bg5 Nb4 18.Be2 Bd7 19.Bxf6 gxf6 20.Ra1 ( 20.Nc3 dxc3 21.bxc3 Na6 22.Ne4 Kg7 23.O-O Nc5 24.Nxc5 Qxc5 25. Qxb7 Be6 26.h3 $14 ) 20...dxe3 21.fxe3 b5 22.Qc3 ( 22.cxb5?! Be6 23.Qd1 Rac8 24.O-O Nc2 25.Nc3 Nxa1 $13 ) 22...bxa4 23.O-O $14 f5 24.Nf3 f6 25.Nh4 Nc6 26.Qa3 Qd2 27.Rf2 Rab8 28. c5 Kh8!? $14 ) 11...Ne4 12.O-O Nxc3 13.bxc3 h6 14.a4 Ne7 15.Ne5 Bd6 16.cxd5 Nxd5 17.Bf3 Nxf4 18.exf4 Bxe5 19.Rxd8+ Qxd8 20.fxe5 Qc7 21.Rb1 Rb8 22.Qd3 Bd7 23.a5 Bc6 24.Qd6 Qxd6 25.exd6 Bxf3 26.gxf3 Kf8 27.c4 Ke8 28.a6 b6 29.c5 Kd7 30. cxb6 axb6 31.a7 Ra8 32.Rxb6 Rxa7 33.Kg2 e5 34.Rb4 f5 35.Rb6 Ke6 36.d7+ Kxd7 37.Rb5 Ke6 38.Rb6+ Kf7 39.Rb5 Kf6 40.Rb6+ Kg5 41.Rb5 Kf4 42.Rb4+ e4 43.fxe4 fxe4 44.h3 Ra5 45.Rb7 Rg5+ 46.Kf1 Rg6 47.Rb4 Rg5 48.Rb7 Rg6 49.Rb4 1/2-1/2 [/pgn]

Note that the pgn-viewer incorrectly renders "+=" as "=".

I think $14 is rendered correctly, and $11 for = My GUI does that for me.