@bgl Yep, aware of Static Hermes. The big difference is that its annotations define a sound, stricter language: typed arrays aren't ordinary JavaScript arrays, and once something's annotated, that annotation is enforced, not just advisory. In Oseo an annotation is only a hint; a number can still turn out to be a string at runtime, and the compiled generic path has to handle that correctly regardless. Static Hermes also still routes untyped code through Hermes's own interpreter and JIT tiers, so it's really two systems stitched together. Oseo has no VM tier at all: typed and untyped values share one JavaScript semantics, and annotations only pick which already-compiled native path runs. Different platform too: Static Hermes lives inside React Native's engine, Oseo is aiming to be a self-contained native binary, server-side for now.