4.6 Cross-config conversion
The ID’s core promise: the name works even if your config never heard of it. When an operation names an interop ID the active config does not contain, conversion routes through the built-in identities and the interchange roles (aces_interchange; cie_xyz_d65_interchange for display-referred spaces): source space → interchange anchor → target space, across config boundaries. Two configs that have never seen each other, with completely different space names, convert exactly — because both are anchored to the same interchange point.
This is also where the never-guess floor gets teeth: a config that provides no interchange anchor gets a clear error, not an approximate conversion. The demo converts pixels between two genuinely different configs by ID alone, and shows the failure mode when the anchor is missing.
Interchange anchoring, config evolution, and scoped contexts are OpenColorIO’s home turf. OpenImageIO backfills the recommendation-described lookups today (findColorSpaceForID, LocateBuiltinColorSpace); each is a natural candidate for OpenColorIO itself, and OpenImageIO’s design delegates natively as OpenColorIO grows the capability — generously, not territorially: the point is one shared behavior, wherever it lives.