Runners-up last year and winners in 2023, Somerset’s T20 pedigree was again in evidence at Sophia Gardens.
The seam attack of Matt Henry, Riley Meredith and captain Lewis Gregory reduced Glamorgan to 49-5 in the ninth over and the innings did not recover.
A total of 130-9 never looked to be enough as T20 specialist Tom Kohler-Cadmore hit 38, with Gregory scoring the winning run with 20 balls to spare.
Middlesex captain Stevie Eskinazi had asked Surrey to bat first in the London derby and he must have regretted it when Jacks was hitting to all parts.
He fell three short of his hundred and the loss of wickets in the latter overs kept the score to 194-8.
In reply, Middlesex lost wickets at regular intervals, with New Zealand white-ball skipper Mitchell Santner impressing with 3-25.
But it was left to Jacks to grab the last wicket as Surrey bowled their rivals out for just 119.
Essex opted to chase at Ambassador Cruise Line Ground, in Chelmsford, in search of that elusive win, but they watched Kent opener Tawenda Muyeye strike his maiden T20 century with 100 off 59 balls as they racked up an imposing 219-3.
Dean Elgar struck 50, but Matt Parkinson produced his T20 best figures of 5-23 to leave the chase in tatters.
T20 captain Simon Harmer smashed four successive sixes as he hit 55 off 21 balls before he was last man out as they were bowled out for 172.
Gloucestershire’s defence of their T20 crown began with six straight losses, but they made it two wins in a row in a Bristol thriller.
David Payne starred with the ball taking 3-20 as Hampshire were squeezed to 124-9.
But despite D’Arcy Short’s 49, things got tense as Liam Dawson and Benny Howell slowed up the scoring, and with three needed off Chris Wood’s final over and then one off the last ball, Payne hit it for six to secure victory.
Friday night’s T20 scorecards