A new foundation for an old world. RustUO is an Ultima Online server written from scratch in Rust, designed to run on a single deterministic simulation thread without pausing to save.
- library crates
- 26
- lines of Rust
- ~490k
Under the hood
- Designed for approximately 5,000 concurrent players per shard, with an 8 ms simulation tick
- No save pauses: continuous write-ahead logging and checkpoints, with at most one simulation tick lost in a crash
- Game content scripted in Luau, with hot reloading and era rulesets selected at runtime
- Hardened with 24-hour fuzzing campaigns, 1,000-cycle crash/restart tests, and deterministic simulated-disk testing
- Built using parallel teams of AI coding agents, guided by architecture decision records and enforced crate layering
