Valdez, a 30-year-old left-hander from the Dominican Republic, struck out five Rangers batters and issued three walks before giving up the homer and departing to a standing ovation.
The pitcher, who threw 67 of his season-high 107 pitches for strikes, baffled the Rangers for eight innings, then opening the ninth by walking Robbie Grossman before Ezequiel Duran grounded into a double play.
One out from completing the no-hitter, Valdez walked Josh Smith to bring Seager to the plate, where the short stop smashed the ball into the right-field stands, lifting the Rangers to two runs in the final round.
Astros reliever Josh Hader took the mound, walked Marcus Semien, then induced Josh Jung to hit a fly ball out to right field to end the game, Valdez getting the victory to improve to 11-5 on the season.
Valdez threw his first no-hitter for the Astros on August 1, 2023, against visiting Cleveland, the 16th no-hitter for Houston but the first by a left-hander.
He would have joined Don Wilson, who threw two no-hitters in the 1960s, as the only Astros pitchers with multiple no-hitters.
