Earth’s persistent habitability since the Archean remains poorly understood. Using an oxygen isotope ensemble approach—comprising shale, iron oxide, carbonate, silica, and phosphate records—we reconcile a multibillion-year history of seawater δ¹⁸O, temperature, and marine and terrestrial clay abundance. Our results reveal a rise in seawater δ¹⁸O and a temperate Proterozoic climate distinct to interpretations of a hot early Earth, indicating a strongly buffered climate system. Precambrian sediments are enriched in marine authigenic clay, with prominent reductions occurring in concert with Paleozoic and Cenozoic cooling, the expansion of siliceous life, and the radiation of land plants. These findings support the notion that shifts in the locus and extent of clay formation contributed to seawater ¹⁸O enrichment, clement early Earth conditions, major climate transitions, and climate stability through the reverse weathering feedback.