# PH-SYM-002

**Name:** Reflection equivariance violation

**Severity:** warning

**Input modes:** adapter+dump

Discrete reflection equivariance (Z₂ action on each of two independent
axes of a 2D periodic square grid). The rule reflects the input across
each axis independently, queries the model on the reflected input,
applies the inverse reflection to the output, and compares against the
original output. The raw value is the relative discrepancy on a
calibrated noise-floor band; the rule fires when the model breaks
discrete reflection symmetry on a square-domain problem.