Glamorgan 302 and 111 for 3 (Byrom 40) lead Yorkshire 226 (Revis 50, Crane 5-55) by 187 runs
Mason Crane spun Glamorgan into the ascendancy against Yorkshire despite having plenty still to do to force a final-day result.
The legspinner took 5 for 55 to break the spine of Yorkshire's innings as they slipped from 87 for 1 to 226 all out. Crane took two wickets in an over, dismissing debutant Sam Whiteman for a sprightly 48 to start the slide, which was helped by overseas Ryan Hadley returning a three-for. Matthew Revis kept the visitors alive with a half-century.
Glamorgan finished the day on 111 for 3, leading by 187 runs heading into day four. Before play, Jonny Bairstow became the second injury sub in County Championship history after being off the field for all of day two due to a thumb injury sustained while keeping, confirmed to be a small fracture. Will Luxton came in for him while Dom Bess continued to lead Yorkshire on the field.
Hadley got the day underway and Yorkshire's intent was evident from ball one, as it needed to be in attempt to avoid the game petering out to a draw: Adam Lyth dismissing a full toss to the fence.
Timm van der Gugten opened Glamorgan's account for Division One wickets before Whiteman and Lyth played positively against Andy Gorvin and Ben Kellaway, who both struggled to replicate the tightness of Yorkshire's attack on the previous two days.
Crane's introduction brought instant intrigue. Even his loose balls showed signs of spin and once he had Whiteman and James Wharton in the same over every ball seemed a threat. The legspinner's ball to remove George Hill was near-perfect, almost unimaginable for day three of the season opener. A 14-over spell, straddled by lunch, put Glamorgan in control.
From 136 for 6, Bess and Revis continued to play positively, latching onto loose deliveries from seamers until Bess was adjudged lbw after a 41-run stand.
Revis, now batting with the tail, was forced to attack, bringing up his half-century by swinging a Hadley short ball into the stands - and continuing his form from 2025, when he topped the Yorkshire averages. But another short ball followed and he was strangled down the leg-side.
Coad and Jack White managed to reduce the deficit before Crane wrapped up his fifth five-wicket haul since joining Glamorgan in 2024.
With 45 overs still left to bat, and a 76-run lead, Glamorgan came out conservatively. The pitch's pace still offered little as it had done in the two previous days and Yorkshire's attack again achieved control.
With Crane as inspiration and three wickets of his own in the first innings, Bess came on for an unchanged 17-over spell in the 13th. He continued to tie down the hosts. Once Asa Tribe had gone for 19, attempting to pull a length ball, the standing-in captain, Bess, struck again with Dickson losing patience, caught at mid-on.
Eddie Byrom made a well-made 40 before departing at fine-leg then it was over to first-innings centurion, Colin Ingram, and Kiran Carlson to steer Glamorgan to the close.
