Why I built determinism into a physics engine from day one (and what I learned)

Here's the full article, ready to paste: Title: Why I built determinism into a physics engine from day one (and what I learned) Most physics engines treat determinism as an optional feature. I wanted to build one where it was the constraint everything else was designed around. The core problem Floating point math isn't deterministic by default across compilers, platforms, or even optimization levels. For lockstep multiplayer or replay verification, that's a dealbreaker. What bitwise determinism actually requires Getting identical results across runs on the same binary means controlling three things: FP evaluation mode — MSVC needs /fp:precise, GCC/Clang need -ffp-contract=off Memory allocation order — any non-deterministic allocator breaks replay Execution order — multithreading requires a deterministic parallel mode UPE enforces all three. State is CRC64-hashed every frame. Proof logs are generated as part of CI. If the hash drifts, the build fails. What this unlocks Once you have a d