The simulations described above comprise the exploration block of Stage 1. At each iteration of our workflow, the explored configurations are down-sampled using our ensemblebased uncertainty metric, ϵ t (eq. 1). Sampled configurations are subsequently labeled with DFT single-point (DFT/SPE) calculations. We employ a sampling approach which uniformly selects configurations within a given uncertainty range (ϵ t,min < ϵ t < ϵ t,max broken into 10 bins), as detailed in the SI, to select a diverse range of configurations that encompass a spectrum of model uncertainty. The sampling is also dynamic so that more configurations are labeled per bin from reaction samplers (ie. Sella, MD, IRC) which have a higher max uncertainty (see Tables-S2-S3).