Aru won stage five of the Tour to La Planche des Belles Filles with a well-timed attack, pulling back 20 seconds on Froome in the process, but the three-time Tour victor said he would not make the same mistake twice.
Bardet won Stage 12 ahead of Rigoberto Uran and Aru, who seized the race lead from Froome by six seconds.
The Team Dimension Data rider had been part of a 12-man break which went away early on the stage, and the two-time Tour stage victor attacked solo on the climb of the Port de Bales.
Fabio Aru snatched the overall race lead from Britain's Chris Froome in a dramatic finish to the 214 kilometre stage 12 of the Tour de France, with local favourite Romain Bardet earning victory in Peyragudes. "I just put on my helmet and it comes out like that".
I had a bad moment here at the end. Froome tried to respond but didn't have the legs to follow - yet Bardet did.
How Froome might have wished for the legs he had on these same roads in 2012, when he was made to wait for Sir Bradley Wiggins when he wanted to attack in search of a stage win.
New Zealand's George Bennett, riding for Team LottoNL-Jumbo, finished eighth in the stage, 27 seconds behind Bardet, to move up to ninth overall, 4 minutes and 24 seconds behind Aru. "Ramps of over 20 per cent, that's a really hard finish and I can only say congratulations to Romain Bardet for winning the stage and to Fabio Aru for taking the yellow jersey".
BENOIT TESSIER REUTERS Romain Bardet of France pulls away from Fabio Aru and Rigoberto Uran to win stage 12 of the Tour de France
"Today was a chance, I just needed the right combination", the 36-year-old said.
Cummings held a gap of two minutes over the summit of the climb - and was given a lifeline when Froome and Aru overcooked a bend at the start of the penultimate climb and were forced into a grass verge.
It is the first ever time a Team Sky rider has given up the yellow jersey in the Tour de France to anyone outside of his team.
Aru's teammate Jakob Fuglsang, who broke two bones in a crash during Wednesday's stage, struggled at the back and dropped out of contention after starting the day in fifth place overall.
In kph, Chris Froome's maximum speed in the descent from the Port de Bales. Nieve went straight onto the grass between lorries and camping caravans.
The Colombian Nairo Quintana, he has been distanced from the slopes of the Peyresourde.