Scarlets survived a real scare from Connacht to seal a a bonus-point 36-27 victory in a nine-try thriller in Llanelli.
The defending Guinness PRO14 champions were again impressive in attack, but their defence left something to be desired as Connacht scored four tries to their opponents' five.
In the end, it was Wayne Pivac's side who came out on top, with replacement lock Tadhg Beirne scoring the crucial try, adding to earlier efforts from Johnny McNicholl, man of the match Steffan Evans, Rhys Patchell and Leigh Halfpenny.
Connacht gave as good as they got and Tiernan O'Halloran's second try gave Jack Carty the chance to tie the game. The fly-half couldn't take it though and it meant O'Halloran's earlier effort, plus scores from Carty himself and Cian Kelleher, could only earn the Irish side a four-try bonus point.
An entertaining first period started with a bang.
First, McNicholl found himself on the end of a powerful Jonathan Davies break to open the scoring and Halfpenny added the simple conversion.
Connacht promptly went up the other end and responded, Carty picking up a loose Scott Williams pass to make his way to the line and add the extras to his own score.
It failed to hide the fact Scarlets were the more dangerous side and young Wales prospect Evans scorched clear from 40 metres to score and then created a simple finish for Patchell.
Halfpenny converted the second of those scores and the only worry for home coach Pivac was losing Wales prop Rob Evans after he collided with team-mate Josh Macleod.
Carty had kicked three points from a scrum penalty immediately won after Rob Evans had departed, but there was still time for three more tries before half-time.
Two quick scores for Connacht came via wingers O'Halloran and Kelleher, both flowing team moves which the Scarlets should have prevented.
Carty converted Kelleher's effort, but Halfpenny's conversion of his own try ended a breathless first half with the Scarlets 26-22 ahead.
Pivac's side should have been further clear, but in a tight second half the home outfit remained very much in a contest.
McNicholl put Williams away for a clean break, but his long pass couldn't find Steffan Evans. Darragh Leader missed with a long range effort for Connacht, but Halfpenny showed him how it should be done with the first points after the interval.
The second half, like the first, was end-to-end and Connacht remained well in the game. O'Halloran's second gave Carty the opportunity to level the scores, but his kick drifted wide.
Scarlets breathed a sigh of relief and went up the end to seal victory as Beirne - who is set to play his rugby in Ireland next season - dived over and Halfpenny converted.