In this paper, we investigate the ideal magnetohydrodynamics (MHD) equations on torus \(\mathbb{T}^d\) . For d = 3, we resolve the flexible part of Onsager-type conjecture for Elsässer energies of the ideal MHD equations. More precisely, for \(\beta < 1/3\) , we construct weak solutions \((u, b) \in C^\beta([0,T] \times \mathbb{T}^3)\) with both the total energy dissipation and failure of cross helicity conservation. The key idea of the proof relies on a symmetry reduction that embeds the ideal MHD system into a 2 \(\frac{1}{2}\) D Euler flow and the Newton-Nash iteration technique recently developed in V. Giri (Invent Math 238:691–768, 2024). For d = 2, we show the non-uniqueness of Hölder-continuous weak solutions with non-trivial magnetic fields. Specifically, for \(\beta < 1/5\) , there exist infinitely many solutions \((u, b) \in C^\beta([0,T] \times \mathbb{T}^2)\) with the same initial data while satisfying the total energy dissipation with non-vanishing velocity and magnetic fields. The new ingredient is developing a spatial-separation-driven iterative scheme that incorporates the magnetic field as a controlled perturbation within the convex integration framework for the velocity field, thereby providing sufficient oscillatory freedom for Nash-type perturbations in the 2D setting. As a byproduct, we prove that any Hölder-continuous Euler solution can be approximated by a sequence of Cβ-weak solutions for the ideal MHD equations in the Lp-topology for \(1\le p < \infty\) .
