Determinism

Regenerating a corpus from its configuration and seed is held to two different bars, and confusing them is the mistake this page exists to prevent.

Ground truth is exact. Labels — bounding boxes, target range and velocity, class identifiers, signal-to-noise values — are computed in the plan layer from decided values and never pass through a parallel floating-point reduction. A label that moves between two runs is a defect, not noise, and no tolerance applies to it anywhere.

Waveforms need only be physically equivalent, within a relative tolerance. A ray-traced solve spreads work across threads and sums each contribution as its thread finishes; floating-point addition is not associative, so identical rays under an identical seed give different last bits when summed in a different order. That is a reduction order, not a seeding defect — the same solve pinned to one worker is exactly reproducible. Measured on the shipped ray-traced path, the run-to-run difference is about 1.6e-13 V absolute, roughly 3e-06 relative; the release gate allows 1e-05 relative L2 and reddens above it.

The release gate checks both bars separately and reports the measured waveform deviation, so headroom is visible rather than assumed. Tolerance is declared per configuration in ci/golden_paths/manifest.json and defaults to zero, so a path containing no environment-bound node is still held to byte identity.

A node declaring ReproClass.DETERMINISTIC promises byte-identical output and that promise is unchanged; what does not hold is byte identity of a whole published corpus whose graph contains an environment-bound node.

No general byte-identical guarantee applies across every backend, dependency version, hardware target, configuration, or hosted-model response. Annotation prose is intentionally non-deterministic. For an executable scope and exact checks, use Golden Paths and the installed-wheel qualification test rather than legacy seed-hierarchy or release-gate designs.

The reasoning, the measured figures, and how the two bars are separated in practice are in engineering principles.