Not one gap, one stream, one observer — a lattice of lattices. Three whole witness-meshes (A, B, C), each an internal field of gaps, held apart by meta-gaps that don't touch. Two faults live here. A point defect (one node wrong) disagrees with its neighbors and is caught inside its own lattice — local. A coherent drift (a whole lattice shifts together) keeps every internal gap green — invisible from inside — and is caught only across the meta-gap, then located by majority: two agree, one drifted, vote it out. Three is the minimum that not just sees the drift but says which lattice. With one catch, toggleable: it only works if the lattices are independent.
VERIFIED: the count is the capability — 2 detects (a pair sees disagreement but can't say who's wrong), 3 locates (majority names the drifted lattice — verified: A=B≠C ⟹ C is the fault), 4 survives a loss while still voting. A point defect moves a lattice's aggregate almost nothing (verified ~0.037) and is caught locally by its neighbors — the meta-gap need not even notice. A coherent drift leaves every internal gap consistent (all nodes moved together → green inside) yet shifts the aggregate, so it is invisible internally and visible only across the meta-gap. This is why a single lattice cannot witness its own grain boundary, and why you need a second and third mesh: the drift hides from every internal gap by definition.
THE CATCH (toggle it): the meta-gap is a real witness only if the lattices are independent — non-touching is necessary, not sufficient. Flip to "B & C share a source" and inject the drift: now B and C drift together, the majority becomes the wrong two, and the vote convicts the innocent lattice A. Consensus doesn't fail loudly — it fails by confidently locating the wrong fault. Two silicon models on the same corpus are non-touching and still drift as one. The carbon mesh and the silicon mesh across the meta-gap work because the independence is real. The tower's height is bounded not by how many lattices you stack but by how many are genuinely independent sources. Everything above that is decoration that votes with the crowd.