Praggnanandhaa had forced a tiebreak against So after drawing his final Classical game against Dutch Grandmaster Anish Giri. With the two players level on points, the tournament rules came into effect, eventually leading to an Armageddon showdown to determine the champion.

So, who had occupied the top position for much of the tournament, held his nerve when it mattered most. In the decisive phase, the American played with the black pieces and managed to secure a draw, which was enough for him to claim the title under the Armageddon rules.

The result denied Praggnanandhaa what would have been another major triumph in an increasingly impressive career. The Indian youngster nevertheless produced a strong performance throughout the Sinquefield Cup, remaining firmly in contention for the title until the very end.

The final Classical round had already set the stage for a dramatic finish. Praggnanandhaa's draw against Giri meant that he could not secure the title outright and needed the tiebreak procedure to settle the contest with So. The American had been one of the most consistent performers during the tournament and carried considerable momentum into the final stages.

According to the tournament regulations, tied players first contest two rapid games. If those games fail to produce a winner, the title is decided by a final Armageddon game. The format is designed to ensure a decisive result, with the player having the black pieces receiving a crucial advantage.

In the Armageddon, White is given five minutes while Black receives four minutes. However, Black has the benefit of winning the match if the game ends in a draw. This makes the format particularly demanding for the player with the white pieces, who must take greater risks to force a victory.

Praggnanandhaa therefore had to play for a win in the final game, while So could afford to remain solid and allow the clock and the rules to work in his favour. The American successfully negotiated the game and held the draw, securing the Sinquefield Cup title.

The tournament is part of the prestigious Grand Chess Tour, which brings together many of the world's leading players across a series of elite events. A strong showing in St. Louis therefore represents a significant achievement for Praggnanandhaa, who continues to establish himself among the top players of his generation.

The Indian Grandmaster's runner-up finish also highlights his growing consistency at the highest level. Despite falling short in the final Armageddon, Praggnanandhaa remained competitive throughout the event and pushed the tournament leader all the way to the final tiebreak.

For So, the victory capped a successful tournament in which he maintained his position near the top for most of the rounds before holding his nerve in the decisive battle. Praggnanandhaa, meanwhile, will take confidence from his performance as he continues his campaign on the international circuit.

The dramatic finish once again underlined the unpredictable nature of elite chess, where a tournament can ultimately be decided by a single game and, in this case, a draw that proved enough for the player holding the black pieces.