It was the final week of the 2025–2026 postseason eligibility as Harrison made his debut, facing off against a 4-time champion named Allegra Kuney, who was one win away from punching in the final official spot in the 2026 Jeopardy! Tournament of Champions. Harrison was a struggler after he missed the Daily Double clue in THE RULES OF THE GAME as the 24th clue of the Jeopardy! round, but he persevered by going from worst to first from the start to the end of the Double Jeopardy! round, making sure Allegra doesn't win her fifth game, but all three players were over the $10,000 going into Final Jeopardy! Allegra and Harrison came up with the correct question in Final Jeopardy!, and with a cover bet, Harrison became the new champion, and Allegra unfortunately missed out on winning her fifth game; however, she was qualified as the 10th seed going into the 2026 Jeopardy! Tournament of Champions.
Harrison won over $20,000 per regular-season play game until his eighth game. His seventh game dethroned Paolo Pasco as the biggest money-winner of season 42. With 11 out of 13 runaway victories, Harrison became the 19th super-champion in Jeopardy! history, and with fourteen victories, he has the 13th-longest winning streak in Jeopardy! history. Also, with $373,999 (excluding the consolation prize), that helped him become the 14th biggest money-winner in regular-season play and 31st biggest winner in Jeopardy! history. However, Harrison is the only super-champion to have under 60% of Daily Doubles correct (17/31). Harrison also broke two one-game winning records in his regular-season play run, surpassing Jonathan Hugendubler's $40,000 win on September 8, 2025.
Harrison was the only super-champion to get Final Jeopardy! incorrect in his final regular-season play game while in the lead (just like Ken Jennings and Scott Riccardi), which made his loss a shocking upset by fans, but despite losing the game to Libby Jones, Harrison is set to return for the 2027 Jeopardy! Tournament of Champions in the winter of 2027.