League Cup holders St Mirren scored an injury-time winner to complete a remarkable comeback in a seven-goal thriller with League 1 visitors East Kilbride.
Craig McLeish's side trailed last season's fourth-tier champions by three goals at the hour mark, before goals from Eseosa Sule, Ryan Carr, and Killian Phillips were followed by Malik Dijksteel's stoppage-time strike.
It leaves the Paisley side on nine points with a final-day meeting with Dunfermline Athletic deciding who will win the group.
Fellow top-flight side Falkirk are all but out of the competition, though, after a meek 1-1 away draw with League 1 Alloa Athletic, followed by a 4-2 loss in the bonus point penalty shootout.
John McGlynn's side took the lead through Scott Tanser before 16-year-old Rangers loanee Kyle Glasgow levelled, leaving both sides on four points and highly unlikely to progress regardless of their final group game result.
Dundee lost 7-6 in the bonus point shoot-out with League 1 side Ross County after a 1-1 draw in regular time. Finlay Robertson put Steven Pressley's side ahead before Brian Graham levelled.
Dundee can still progress with a win in their final game, but may need to rely on results elsewhere to secure a knockout berth.
Dundee United's hopes of progressing also remain alive after they thumped Spartans 4-0 in their final group-stage game, moving on to nine points and a plus-seven goal difference.
Lachie Rose scored a double either side of the interval, with Dylan Tait and Zac Sapsford adding late goals.
Kilmarnock continued their unbeaten start to the season with a narrow win over Hamilton Academical, thanks to Greg Kiltie's goal.
Should they avoid defeat in their final game against Peterhead, they are guaranteed progression to the last 16.
And Inverness Caledonian Thistle saw off Premiership visitors St Johnstone with a narrow 1-0 win, thanks to Alfie Stewart's early strike.
Simo Valakari can still guide his side into the knockout stages with a win over East Fife, but they may also need other results to fall in their favour.