At low speed, systems behave linearly.
Near critical velocity, they do not.
The boundary condition held for days.
Hovering.
Not breached.
But not comfortably below.
In New York City, microstructure metrics showed rising order-to-trade ratios.
In London, latency arbitrage tightened spreads while deepening fragility.
In Tokyo, turnover reached historic intraday peaks.
Speed became endogenous.
Participants reacted to reaction speed itself.
Maya revised the model again.
"At critical regimes," she said,
"response ceases to scale proportionally."
She wrote the nonlinear correction term.
"Linear damping first," she explained.
"Nonlinear damping when displacement grows."
Keith studied the curve.
"So small moves decay normally."
"Yes."
"But larger ones behave differently."
Jasmine plotted effective stability curvature.
"Well deep near zero," she said.
"Flatter at the edges."
Which meant:
Contained shocks remained small.
But if velocity pushed displacement beyond threshold—
Resistance weakened temporarily.
In Chicago, intraminute price swings began clustering.
In Frankfurt, ETF arbitrage lag increased slightly during rapid moves.
In Singapore, macro strategies reduced position persistence further.
Adaptation had shortened cycles.
Now cycles overlapped.
A rapid shock struck.
Minor in origin.
Fast in execution.
Displacement crossed nonlinear threshold briefly.
Correction engaged.
But nonlinear damping delayed full response.
Price overshot more than linear model predicted.
Then snapped back.
Sharper than before.
Maya quantified the transition point.
"Beyond this," she said,
"nonlinear effects dominate."
Keith exhaled slowly.
"So the edge isn't a line."
"It's a curvature change."
In Hong Kong, overnight volatility printed brief spikes before compressing.
In Zurich, defensive positioning rose marginally.
In Washington, D.C., there was still no intervention.
The system corrected.
But with sharper angles.
Jasmine updated critical velocity metric.
Effective lambda weakening at high displacement.
Not failure.
But curvature softening.
Keith summarized quietly.
"So stability now depends on staying small."
Maya nodded.
"At high speed, magnitude matters more."
Chapter 206 does not destabilize.
It bends.
Linearity fades near boundary.
Small shocks contained.
Larger ones behave unpredictably.
Speed amplifies displacement.
Displacement triggers nonlinear response.
The system survives—
But with steeper edges.
Because at critical velocity,
Stability is no longer smooth.
It is conditional.
And conditional stability
Requires constant proximity to center.
Drift too far,
Move too fast—
And correction changes shape.