PH-CON-002

Name: Energy conservation violation

Severity: error

Input modes: adapter+dump

Scope separation (read first): PH-CON-002 validates the production rule’s ability to measure wave-energy drift on analytically controlled conservative snapshots. It does not certify the accuracy of a wave-equation time integrator.

The F2 fixture splits into two distinct layers:

• F2 harness-level (authoritative): E(t) computed directly from analytical u_t, u_x, u_y — roundoff-only drift.

• Rule-verdict contract: analytical u snapshots fed to the rule; rule computes u_t via 2nd-order central FD internally → O(Δt²) drift with method-dependent tolerance.

Plan §17’s “leapfrog time-stepper over 1000 steps with 1e-8 tolerance” is not implemented in V1 — PH-CON-002 does not use a leapfrog stepper (it uses central-FD on supplied u snapshots), and any numerically-evolved fixture would be supplementary with its own tolerance per user’s revised Task 9 contract.

Pure numpy — no mesh assembly, no torch / scikit-fem.