Season 26 entrance league

The engines that will play in the season 26 entrance league are:

relegated from season 25 league 2: Velvet Tucano Wasp
played in season 25 entrance league: Booot Weiss Equisetum Winter Expositor Stash
new to TCEC (played in Swiss tournament): Obsidian Willow Stormphrax akimbo Altair
returning to TCEC: Berserk (season 24 premier division) Texel (season 17 league 2)

Final standings

Berserk, Obsidian, Velvet and Stormphrax advance to league 2. Berserk was the clear leader from the start, this was expected considering that it was in the premier division in season 24 and started in the entrance league because it didn't play in season 25. It won 13/15 game pairs with no loss. Obsidian and Velvet kept a small advantage over the other engines, Obsidian lost one game pair to Berserk while Velvet did not lose any game pair. There was a race for the fourth qualifying spot, with Storphrax and Altair leading and Equisetum and Booot not far behind. Altair had a small lead with two rounds left, but then Stormphrax won a game as black (against the bias, the only such win in the league) and equalized. Stormphrax advanced on a tiebreak.

The 4 qualifiers will play in league 2 together with:
played in season 25 league 1: Viridithas, ScorpioNN, Ginkgo (replaces Fritz), DeepSjeng
played in season 25 league 2: Arasan, BlackMarlin, Uralochka, Marvin

Interesting games

game 14, Berserk  - Weiss: Berserk captured a pawn and attacked on the king side. Weiss reduced to a RB vs RN position, Berserk slowly captured black pawns until there were none left, then exchanged the minor pieces. Berserk queened a passer and won.

game 18, Stormphrax - Wasp: The position seemed drawn after many early exchanges, however Stormphrax played better with only RBN vs RBN left. It captured a pawn and created a passer on the 7th rank, then gave it back and reduced to a B vs N ending. Stormphrax created another passer and used it to win.

game 19, Weiss - Equisetum: Weiss had a passer on the queen side and a pawn majority on the king side, Equisetum had a passer in the center. Weiss created a second passer and exchanged queens, the game eventually reached a rook ending. Equisetum captured one passer but lost more pawns, the game ended in a tablebase win.

game 24, Velvet - Booot: Velvet skewered rook and queen after Booot chose a bad square for its rook. Velvet captured a rook for a bishop, then later gave back the material for a passer in the center. Velvet gave its queen for a rook to connect a second passer and then queened one. The rook advantage was enough for a win.

game 29, Berserk  - Tucano: Berserk opened the queen side and created a passer, Tucano gave two pawns and pushed a passer to the 2nd rank. Berserk blocked with a rook, Tucano gave a rook for a bishop to capture the white passer. Berserk opened the king side, reduced to a QRB vs QBN position and captured the black passer. The black king was exposed and the game ended in mate.

game 33, Stormphrax - akimbo: The engines castled in opposite directions, both created passers on the same side as their king. The game reached a RBN vs RNN position and Stormphrax went a pawn up. akimbo had a passer on the 3rd rank that was blocked, Stormphrax traded knights and captured a second pawn. The game ended in a tablebase win.

game 44, Berserk - Obsidian: Berserk was a pawn up in a QRN vs QRB position, it managed to get its major pieces to the back rank and threatened the black king. Berserk reduced to a queen ending, then slowly pushed its king forward. Obsidian couldn't avoid a queening and the game ended in mate.

game 45, Equisetum - Winter: The engines castled in opposite directions and Equisetum attacked the king side. It gave a pawn and moved its major pieces to threaten the black king. Winter gave the pawn back, creating a white passer on the 7th rank. Equisetum went two pawns up, gave up the passer and reduced to a winning rook ending.

game 60, Equisetum - Velvet: Queens were off early and both kings moved without castling, the engines reduced to a RB vs RN position. Equisetum moved its rook to the 7th rank, the black pieces defended pawns passively. The white king moved forward, after exchanging minor pieces Equisetum captured two pawns. The game ended in a tablebase win.

game 67, Winter - Stormphrax: There were only a few exchanges after the start and the position was closed for a long time. After exchanging queens Stormphrax gave a knight for 4 pawns and the position opened. The game reached a RBB vs RB position, Winter slowly captured pawns and by move 114 each engine had two remaining pawns. Winter queened a passer and mated.

game 68, Obsidian - Willow: Willow kept its king uncastled and struggled to develop its king side rook. The rook was exchanged a few moves after it was freed, and the game reached a RBN vs RBN position. Obsidian went a pawn up, Willow gave a bishop for a pawn to avoid connected passers. Stormphrax reduced to a tablebase win with one last pawn left.

game 83, Obsidian - Weiss: Obsidian had a pawn majority on the queen side and it pushed its pawns forward. The black pieces were mostly passive, the game reached a RRN vs RRB position with white a pawn up. Weiss lost more material and the game ended in a tablebase win.

game 84, Velvet - Stormphrax: Stormphrax gave a pawn and the engines opened the king side. All rooks and most pawns were exchanged, Stormphrax pushed a passer forward and Velvet gave a bishop to stop it. The white king was exposed to check but eventually found a safe square, the game ended in a tablebase win.

game 104, Berserk - Equisetum: Berserk went up a pawn, the engines slowly exchanged pieces and the game reached a QB vs QN position. Berserk created a passer, Equisetum captured it but Berserk created another and reduced to a queen ending. The engines traded pawns and the game ended in a tablebase win.

game 105, akimbo - Equisetum: akimbo went up a pawn, Equisetum traded both its bishops for white knights. The game reached a RBB vs RNN position, akimbo had a passer in the center blocked by a knight. akimbo increased the pressure and eventually captured a knight for a pawn, then captured the remaining black pawns and forced mate.

game 110, Altair - Booot: There were only a few exchanges after the start, the engines mostly shuffled. After move 47 Booot exposed the white king while Altair pushed a passer to the 7th rank. Booot lost a knight for the passer, Altair created more passers and Booot lost more material until it was mated.

game 113, Obsidian - akimbo: Evals started to increase after move 25, a series of exchanges opened the center 15 moves later. The game reached a rook ending, Obsidian captured the isolated black pawns and pushed connected passers. The game ended in a tablebase win.

Standings after RR1: Berserk +7, Obsidian +5, Velvet +3, Stormphrax Altair +2, Equisetum +1, Willow Tucano akimbo 0, Booot Wasp Weiss -1, Texel -3, Winter Stash -4, Expositor -6. Berserk leads after winning all games as white and drawing all games as black. Obsidian in 2nd place has only one loss to Berserk. Of the new engines Stormphrax and Altair also have a good chance of  advancing, Altair has no loss so far.

game 122, Equisetum - Willow: The engines shuffled for a long time, on move 113 they started to exchange pieces and pawns and the game reached a RB vs RB position. Equisetum was a pawn up with a passer, after another long shuffle Equisetum found a way to improve. It used a passer to capture a piece, the game ended in a tablebase win.

game 138, Wasp - Stormphrax: Both engines had a passer in the center, but the black passer was isolated. Wasp placed a strong bishop on f6, after some shuffling Stormprax decided to exchange the bishop for a rook. Both passers were captured, the game reached a RR vs RN position. Wasp captured all the remaining black pawns, the game ended in a tablebase win.

game 140, Berserk - Altair: Berserk created a passer in the center, then gave a rook and two pawns for a bishop to push the passer to the 6th rank. The game reached a RBB vs RRN position, Altair also pushed a passer forward but it had a pinned rook. Eventually both passers were captured and the engines reduced to a RB vs R ending with black two pawns up. The game ended in a tablebase win.

game 145, Booot - akimbo: The engines castled in opposite directions and Booot tried to attack on the king side. In a series of exchanges Booot traded BN for R and opened files, creating a passer. akimbo played inaccurately, after exchanging queens Booot pushed the passer forward, akimbo lost a knight for it. The game reached a RN vs BN position and ended in a tablebase win.

game 152, Stormphrax - Willow: In a series of exchanges the engines reduced to a QRR vs QRR position with white a pawn up. All rooks were then exchanged and Stormphrax created a pawn majority on the queen side. Stormphrax captured another pawn and exchanged queens, the game ended in a tablebase win.

game 167, Altair - Willow: The game reached a RN vs RN position with white a pawn up and all pawns on the king side. The engines shuffled and exchanged rooks, on move move 67 Willow played the wrong knight move. The white king managed to move behind the black pawns, Altair captured two pawns and won.

game 177, Texel - akimbo: Texel slowly moved its pieces to the king side in a closed position, then opened the king side in a series of exchanges that started on move 41. Texel gave 3 pawns and attacked the black king, akimbo lost material and the game ended in a tablebase win.

game 180, Velvet - Equisetum: Queens were off early and both kings moved without castling. Equisetum had a passer on the king side, it gave a rook for a knight and the engines reduced to a RR vs RB position. The black passer on the 3rd rank wasn't strong enough, Velvet managed to capture all the black pawns, queen a passer and mate.

game 184, Altair - Weiss: Weiss kept its king uncastled, blocking the king side rook. Altair opened the queen side and doubled queen and rook on the open c file. Weiss exchanged queens and the game reached a RRB vs RRB position. Altair created a passer, the black king side rook finally came out to block. Eventually Weiss lost both rooks for the passer, and Altair mated.

game 197, Velvet - Willow: Willow captured a pawn but Velvet trapped a black rook and captured it for a bishop. The engines reduced to a R vs B ending and the game ended in a tablebase win.

game 200, Tucano - Altair: There were almost no exchanges after the start, the engines mainly shuffled for a long time. Altair pushed pawns on the queen side and after a pawn exchange on move 43 the queen side opened. The first pieces were exchanged on move 50. Tucano blocked a black passer on the queen side and created a passer in the center. Altair gave a knight for two pawns and tried to attack the white king, Tucano exchanged queens and pushed the passer to the 7th rank. The black king was trapped, Tucano finished the game with a rook sacrifice and a mate with minor pieces.

Standings with 5 rounds to go: Berserk +10, Obsidian +7, Velvet +6, Altair Stormphrax +3, Equisetum +2, Booot +1, akimbo Weiss Tucano -1, Willow Texel -2, Wasp -4, Stash -6, Expositor -7, Winter -8. The top three places are practically determined, the fourth engine to advance is still open. Both Altair and Stormphrax lost a game to a weaker engine (Wasp and Tucano), both have a good chance of advancing. Equisetum and Booot have a smaller chance, Booot has two critical games left as white against Altair and Stormphrax.

Top standings with 2 rounds to go: Berserk +12, Obsidian +7, Velvet +6, Altair +4, Stormphrax +3, Equisetum +2, Booot +1. The only changes after 3 more rounds are that Berserk extended its lead and Altair won a game and is now alone in fourth place. Equisetum failed to win as white against Texel, Booot drew as white against Stormphrax, both are unlikely to advance. Stormphrax failed to beat Expositor as white and its chance of catching Altair up are small. 

game 225, Equisetum - akimbo: Equisetum captured a pawn early, the engines reduced to a RN vs RB position with white a pawn up. Equisetum had a passer, akimbo played inaccurately and after exchanging minor pieces Equisetum created a second passer. Equisetum then reduced to a tablebase win.

game 228, Texel - Stormphrax: Texel gave a pawn early, Stormphrax equalized easily and the engines mostly shuffled in a closed position. On move 113 Stormphrax opened the king side, it created two passers and pushed one to the 2nd rank. Stormphrax gave a rook for a bishop and captured more pawns. After exchanging queens Texel lost material to avoid a queening, and eventually was mated.

Top standings before the last round: Berserk +13, Obsidian +8, Velvet +7, Altair Stormphrax +4, Equisetum +3, Booot +1. Stormphrax won a game as black, the only black win of the league. Booot drew as white against Altair and is out of the race. Stormphrax has a tiebreak advantage over Altair and now has a better chance of advancing. Equisetum is still in the race, but its last game is in black and its chances are very small.

In the last round Altair beat Expositor, but then Stormphrax beat Stash and Stormphrax advances on tiebreak.