src/determinism.rs

This file is where every nondeterministic input the engine touches enters, through a trait you can replace.

Swap in a fixed clock and seeded generators and the same run produces the same bytes. That is the precondition for byte-stable replay and cassette-era tooling.

You install these seams through LoopManagers::with_clock and with_id_gen.

Key items

Clock gives you SystemClock, the default, or FixedClock::new(SystemTime).

Your engine stamps gate records and telemetry from the managers’ clock seam, so no hidden SystemTime::now() bypasses it.

IdGen gives you UuidIdGen, the default, or SeededIdGen::new(seed). The seeded form reproduces its id sequence from the seed alone.

Those ids keep v4 version and variant bits, so they stay parse-compatible with what you get from the default.

Rng gives you ThreadLocalRng, the default, or SeededRng::new(seed). The stream handler’s jitter draws through this seam.

Behavior notes

Each seeded type’s entire state is its seed, which seed() exposes. So a fresh generator built from that seed replays the sequence from the start.

These seams are why “same run, same bytes” is testable, and why your gate-record timestamps read 0 before the engine stamps them.

For the deep dive on where the seams install, see Managers.