Glamorgan 181 for 2 (Carlson 76*, Root 53*) trail Worcestershire 455 for 8 (Libby 184, D'Oliveira 174) by 274 runs
Kiran Carlson and Billy Root led a powerful Glamorgan fightback after centurions Jake Libby and Brett D'Oliveira had earlier rewritten the record books for Worcestershire in the Bob Willis Trophy encounter at Blackfinch New Road.
Libby and D'Oliveira set a new partnership record for Worcestershire for any wicket against their Welsh opponents of 318 out of a total of 455 for 8 from their 120 overs and then Ed Barnard dismissed Glamorgan openers Nick Selman and Charlie Hemphrey. But Carlson and Root batted with plenty of fluency in the final session in each completing half-centuries and their unbroken stand was worth 137 in 44 overs by the close when the Glamorgan total stood on 181 for 2.
Carlson ended on 76 off 147 balls with 12 fours and Root faced 134 deliveries with six boundaries and at the close was unbeaten on 53. It was an encouraging contrast for Glamorgan to last week's opening BWT encounter at Taunton when they were bowled out for 131 and 166 in suffering a 289-run defeat to Somerset.
The Libby-D'Oliveira stand surpassed the previous Worcestershire best of 287 by Graeme Hick and Tim Curtis for the second wicket at Neath 34 years ago.
Libby also achieved his career best score, beating his 144 for Nottinghamshire versus Durham four years ago, and went onto make 184. He batted for more than seven hours, faced 319 balls and struck one six and 18 fours to take his run tally to 286 in three knocks since a winter move from Nottinghamshire.
D'Oliveira advanced to 174 before he was dismissed and clearly enjoys facing the Glamorgan bowlers. The 28-year-old scored a double-century against them in 2016 at Cardiff and another hundred batting at No. 9 at the same venue last season - in addition to nine wickets. He faced 262 deliveries hit one six and 21 boundaries.
Worcestershire resumed on 309 for 3 and Libby and D'Oliveira were initially watchful against the second new ball attack of Michael Hogan, who picked up three wickets on day one, and Timm van der Gugten.
The scoring rate gradually quickened and Libby went past his previous highest score when he clipped van der Gugten through midwicket for two. He completed his 150 with a cover drive for three off Hogan.
The new partnership record was achieved with a chop for two off spinner Kieran Bull by D'Oliveira who then reached his 150 with a single off the same bowler. After such dominance by bat over ball, it came out of the blue when Libby gave Bull the charge and was stumped at 388 for 4.
Worcestershire secured their fifth batting point with seven balls to spare of the 110 overs before late wickets were sacrificed in the chase for runs. Riki Wessels was caught and bowled by Graham Wagg and D'Oliveira's splendid knock ended when he tried to steer Wagg down to third man and departed to a fine low catch by keeper Chris Cooke.
Wagg (3 for 66) claimed a third scalp as Ed Barnard holed out to Hogan at long-off. Worcestershire Club captain Joe Leach swatted Bull over the midwicket boundary for six before he was caught in the deep attempting a similar hit to the next delivery.
When Glamorgan launched their reply, Selman and Hemphrey looked secure in advancing the total to 39 but the situation changed after Barnard's introduction to the attack.
The last ball of his first over accounted for Selman, who nicked a delivery which moved away from him through to keeper Ben Cox. It became 44-2 when Hemphrey was leg before to the England Lions allrounder in his third over.
But that was the last success of the day for Worcestershire as Carlson and Root joined forces and batted impressively. Root cut Barnard for two fours in an over and Carlson completed his half-century with a boundary off Charlie Morris and in the process also brought up the 100 partnership in 29 overs.