Toulouse scrapped out a 15-13 win at Pau to reach the summit of the Top 14 table, while Racing 92 left it late to earn a dramatic win over Grenoble.
With Clermont Auvergne not playing until Sunday, Toulouse took their opportunity to go top at the Stade du Hameau.
Pau were leading by three points at the break thanks to Peter Saili's try and eight points from the boot of Thibault Daubagna, with Lucas Tauzin's score and Thomas Ramos' penalty accounting for Toulouse's points.
A 46th-minute try from Arthur Bonneval put Toulouse in front, though, and that proved the only points of a low-scoring second half as the visitors racked up a fourth straight Top14 win.
In Paris, Virimi Vakatawa scored twice as Racing 92 defeated Grenoble 24-23 in a close-fought encounter.
Vakatawa's tries had helped Racing to a four-point half-time lead, but Fabien Alexandre dotted down with a little over 15 minutes remaining to give struggling Grenoble hope of a much-needed win.
But with the clock winding down, Olivier Klemenczak crossed and Teddy Iribaren added the extras to seal the tightest of wins and lift Racing to third.
Castres are just one spot behind Racing after inflicting more misery on Perpignan, who have lost all 10 of their league matches, in a 16-12 triumph in which Scott Spedding scored the game's only try for the away team.
Montpellier ended a three-match losing run in all competitions with a hard-fought 18-15 triumph at second-bottom Agen, Ruan Pienaar's 74th-minute try ultimately proving crucial.
Rounding out the action, Toulon's miserable season continued in a 36-25 loss at Bordeaux Begles. Romain Taofifenua's red card for a reckless late tackle four minutes before the break hindered the away side's cause.