A. For several models of random constraint satisfaction problems, it was conjectured by physicists and later proved that a sharp satis ability transition occurs. For random k-and related models it happens at clause density α α sat 2 k . Just below the threshold, further results suggest that the solution space has a " " structure of a large bounded number of near-orthogonal clusters inside {0, 1} N .In the unsatis able regime α > α sat , it is natural to consider the problem of max-satis ability: violating the least number of constraints.is is a combinatorial optimization problem on the random energy landscape de ned by the problem instance. For a simpli ed variant, the strong refutation problem, there is strong evidence that an algorithmic transition occurs around α N k/2−1 . For α bounded in N, a very precise estimate of the max-sat value was obtained by Achlioptas, Naor, and Peres (2007), but it is not sharp enough to indicate the nature of the energy landscape. Later work (Sen, 2016; Panchenko, 2016) shows that for α very large (roughly, Ω(64 k )) the max-sat value approaches the mean-eld (complete graph) limit: this is conjectured to have an " " structure where near-optimal con gurations form clusters within clusters, in an ultrametric hierarchy of in nite depth inside {0, 1} N . A stronger form of was shown in several recent works to have algorithmic implications (again, in complete graphs). Consequently we nd it of interest to understand how the model transitions from near α sat , to (conjecturally) for large α. In this paper we show that in the random regular kmodel, the description breaks down already above α 4 k /k 3 . is is proved by an explicit perturbation in the parameter space. e choice of perturbation is inspired by the "bug proliferation" mechanism proposed by physicists (Montanari and Ricci-Tersenghi, 2003;Krzakala, Pagnani, and Weigt, 2004), corresponding roughly to a percolation-like threshold for a subgraph of dependent variables.