Josephson junction and show how the d-wave altermagnetic symmetry and geometric confinement shape its low-energy excitations. We find a clear distinction between the two d-wave symmetries: dx2−y2 order produces spin splitting, whereas dxy order preserves spin degeneracy and exhibits splitting of the ABS spectrum induced by intermode hybridization. Leveraging these novel features, we propose applying a transverse electric field to tune the system and realize a magnetic-field-free, parity-protected superconducting qubit that we call altermon.