### Frame metrics

frame_id —
sim_time —
dt —
mass —
energy —
Δm/m —
ΔE/E —
max|∇·B| —
ρ_min —

Orszag-Tang vortex. 128² ideal MHD on a 2π×2π periodic grid. Lax-Friedrichs scheme, CFL-adaptive dt, γ=5/3. Resets at t=π. The kernel is written in Rail and compiled to ARM64 by the project's self-hosting compiler. Each frame's hash is signed by a Pi witness with Ed25519 — same chain that drives /entropy.