BUILD-INTEROP-CONTRACT-GRID-UNDER-MAP-BOTH-PROVIDERS asks for a provider matrix:
the same assertions, once per engine, with identical counts. Interoperability
that holds on one provider and not the other is not interoperability.
It is not a formality here. The map half of this link resolves a religion family
through its own legend, and the legend is drawn by the map engine — MapLibre
drops an entire layer in silence for one misplaced paint property, which would
surface as a link delivering nothing while the Mapbox run stayed green.
So the gate now runs the whole measurement under ?provider=mapbox and
?provider=maplibre, and then asserts the two agree: the same starting total, the
same rows for the same family, and the same rows over the composite's wire. A
per-engine pass with different numbers would mean the same choice narrows to
different peoples depending on which engine a partner embedded.
MEASURED, identical to the row on both:
mapbox 2,107 groups · Buddhism 83 direct · 83 linked · mutant 0
maplibre 2,107 groups · Buddhism 83 direct · 83 linked · mutant 0
The mutant still runs first on each engine, so a green here still means the gate
can tell a right mapping from a wrong one — twice over now.
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