Order book — per-side 2048-slot price ladder indexed directly by tick, with a sorted-vector fallback for out-of-window prices and self-healing re-anchoring. O(1) top-of-book.

Ingest — zero-copy message framing over mmap, chunked reads, or io_uring; a dedicated publisher thread streams snapshots over an SPSC queue.

Determinism — an FNV-1a fingerprint over every level of every book is byte-identical between the native binary and the WebAssembly build on the same input.

Backtester — the OFI signal runs on every symbol in one pass, with a latency sweep, walk-forward split, cost stress, and sanity guards; the browser Strategy Lab runs custom JavaScript strategies against the same rebuilt book.