Tabs that trade width for attention - the chosen one springs open past its own size to let its label in, the last one folds back to an icon.
The wobble is only width. Each tab is its own pill - the selected one springs open to let its label in, the one you left folds back to a circle. Nothing else moves: no scale, no squash, the height never changes.
The spring is measured, not guessed. A 16.5% overshoot peaking at 270ms pins the damping ratio at 0.50 and the frequency at ~14 rad/s - so stiffness: 200, damping: 14.1. That overshoot is the wobble: the pill opens about a sixth wider than it needs to be, hangs there for a beat, then pulls back.
One spring does all of it. A single value runs 0 → 1 and the pill's width, the room the label sits in, its fade and its 8px blur are all reads of that value, so when it overshoots past 1 the pill and the label overshoot together. Two springs look almost right and are subtly out of step. Under reduced motion it goes critically damped - still opens, just never bounces.