In the round of 16 (fourth round), the Ukrainian fell in a three-set duel to world No. 6 Linda Noskova of Czechia, finishing 5–7, 7–5, 3–6.
During the hard-fought encounter, broadcast cameras caught a heartwarming moment involving the Ukrainian player: a spectator sitting in the stands was captured live-sketching Kostyuk directly onto a notepad during active play.
The scene swiftly went viral online, prompting tournament media staff to publish a dedicated clip across official US Open social channels. Within hours, the video garnered over 500k views, 8k likes, and more than 200 comments.
The match marked the third career head-to-head meeting between the two players, tilting the rivalry record 2–1 in Noskova's favor.
Despite the exit, Kostyuk matched her personal tournament record at the US Open by advancing to the fourth round. Throughout 2026 Grand Slam play, Kostyuk produced standout runs by reaching the semifinals at both Roland Garros and Wimbledon, after an opening-round departure at the Australian Open.