The analysis kernel is generated from two independent flags: `parity` (fold north/south latitude pairs, on whenever nlat is even, so always for the Gauss grid) and `subgroups` (use subgroupAdd for the reduction, only when the device reports the feature). Parity mode declares wpv/wmv in place of wfv, and the subgroup branch of the accumulation loop honored that -- but the shared-memory tree-reduction fallback hardcoded wfv. So parity + no subgroups emitted a reference to an undeclared variable: WGSL compile error in leg_analys: 111:15 unresolved identifier 'wfv' which every GPU lacking the `subgroups` feature hit on startup. Give the fallback the same parity split the subgroup path has: c0 accumulates even (l-m) against wpv, c1 odd against wmv. Verified by forcing SHT_SUBGROUPS=false in the headless runner: the error reproduces at exactly 111:15 before, and after the fix the suite passes with analys accuracy 7.42e-7 vs the f64 CPU reference, matching the subgroup path's 7.39e-7.