A gas turbine engine article includes a silicon-containing ceramic substrate and an environmental barrier coating (EBC) system disposed on the substrate. The EBC system includes, from the substrate, a dense bond coat layer, a porous bond coat layer, and a topcoat layer in contact with the porous bond coat layer. The dense bond coat layer and the porous bond coat layer each include a silica matrix and oxygen-scavenging gas-evolution particles dispersed through the silica matrix. The porous bond coat layer includes engineered pores.