a quantity determined only up to the action of a group G — no calculation fixes it; you perform a G-element and observe, or find independent structure that breaks G

The shape: a quantity fixed only up to a group action is not computable — it is resolved only by physically performing a group element (the antineutrino beam is U → U*) or by finding structure that breaks the group. Calibration question: when the Synthesist says "X is undetermined," is X undetermined up to a group action (this shape — resolve by performing) or genuinely open? It recurred across the Hall carrier sign, matter/antimatter, chirality and cosmic topology before it was named — the recurrence is its reach.