The 49ers feasted on three Seahawks' turnovers in the first half, taking a 21-13 lead into the locker room at halftime. The Seahawks now lead 23-21.
Sam Darnold opened the second half by throwing a second interception to cornerback Renardo Green, but the 49ers couldn't take advantage of their fourth takeaway. Eddy Pineiro missed a 52-yard field goal.
The Seahawks used the good field position for a 43-yard field goal by Jason Myers.
Only 3:04 later, Seattle had the lead.
Brock Purdy was picked by Nehemiah Pritchett, who returned the interception to the San Francisco 23. It set up Jaxon Smith-Njigba's 16-yard touchdown reception.
Purdy is 10-of-19 for 93 yards with a touchdown and an interception, and Darnold is 11-of-19 for 112 yards with a touchdown and two interceptions.
More info on: Renardo Green, Brock Purdy