# PH-CON-001

**Name:** Mass conservation violation

**Severity:** error

**Input modes:** adapter+dump

**Scope separation (read first):** PH-CON-001 validates the production
rule's ability to measure **integral conservation drift on
analytically controlled source-free snapshots**. It does not certify
the accuracy of a heat-equation time integrator. The F2 fixture is
explicitly analytical-snapshot (`u = cos(2πx) cos(2πy) · exp(−8π²κt)`,
exact solution of 2D periodic heat with zero spatial mean at all t),
not a numerically-evolved FD solution.

Heat mass conservation check: for source-free periodic heat equation,
total mass `∫_Ω u dV` is invariant in `t`. Rule emits
`max_t |M(t) − M(0)| / max(|M(0)|, ‖u_0‖_{L¹})`; shipped-default
relative threshold 1e-4.