Dough turns soupy during the third coil fold in a 26C kitchen Technique

You can also bulk in the fridge for part of it. Two hours on the counter, then into the fridge for the rest, then shape cold. Not traditional but summer is summer and it makes the timing controllable again.

Six degrees is enormous in fermentation terms, roughly halving your bulk time. Your dough is not failing at the third fold, it is finishing bulk somewhere around fold two and then over-fermenting while you carry on with a routine built for a 20C kitchen. Three fixes that all work: use cooler water so your final dough temperature lands near 24C, cut your starter percentage roughly in half, and stop counting folds and start reading the dough. In summer I do two folds and my bulk is under three hours.

Drop hydration by five points for the summer too. 75 percent at 20C and 75 percent at 26C are not the same dough in the hand, and 70 gives you back some margin while you recalibrate.

Mix at night and bulk while you sleep if your kitchen drops in the small hours. My best summer loaves come from a 10pm mix with very little starter.