Local stability is scanned across exact slope magnitudes. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.

highlighted = computed this step

A small slope is an accepted local contract

The first checked source has slope one half at the fixed point.

m=12<1|m|=\left|\frac{1}{2}\right|<1
Accepted slope sourceThe slope and accepted bit are source-bound.slope=1/2slopeMagnitude=1/2acceptedBit=1 bit

The threshold uses magnitude, not sign

The neutral reflection row has slope negative one. Its magnitude is one, so it is not accepted by the less-than-one contract.

mapmmacceptedcontract12121neutral110repel32320\begin{array}{c|c|c|c}\text{map}&m&|m|&\text{accepted}\\\text{contract}&\frac{1}{2}&\frac{1}{2}&1\\\text{neutral}&-1&1&0\\\text{repel}&\frac{3}{2}&\frac{3}{2}&0\\\end{array}
Neutral slope boundaryNegative one is rejected because its magnitude is one.slope=-1slopeMagnitude=1acceptedBit=0 bit