Continuum or switch? A discontinuous regime boundary

Between a defended and a tracked setpoint there is a discontinuous jump at the R19 spinodal (0.6376), not a smooth gradient: just inside the spinodal the state holds the defended branch; just outside it falls to the tracking branch. The strategies are separated by a sharp regime boundary in the loop dynamics.

RT4 and Q3 (part 2). The defend/track distinction is qualitative: an R19 bistable boundary, not a continuum. The jump at the spinodal is reproducible [V]; the placement of any real species relative to the boundary is a separate empirical question.

The jump

Approaching the spinodal from inside, the defended state persists; crossing it, the state drops discontinuously to the other branch (True). That is the signature of bistability -- the same mathematics that makes the torpor transition a switch.

Range, qualitatively (Q3, part 3)

So the strategies differ over a RANGE that is not merely large but qualitatively partitioned: a metabolic factor of several-fold (previous chapter) PLUS a discontinuous regime boundary here. γ itself spans only ~1.22-1.50 across the panel and does not track the divide -- the real range is in the dynamics, not the promoter read.