The reason confinement is hard, live: drive the normalized temperature gradient a/L_Ti past the critical value and turbulent transport stiffens — the effective confinement multiplier H_eff collapses. Reduced-order surrogate; GENE / CGYRO (the operating HPC workstream) retire it.
Honest gate There is no hard limit here — this is the confinement mechanism. Above the critical gradient the transport is stiff (gradient-clamped); the effective multiplier H_eff sets how much the turbulence degrades confinement. GENE / CGYRO resolve the real spectrum.