polyxios reads and writes 3D mesh and point-cloud files through a single pair of functions, px.read() and px.write(). Formats (PLY, OBJ, MEDIT .mesh, VTK legacy, the VTK XML family including its parallel and multiblock variants, and 3D Gaussian Splat .splat) are provided by pluggable codecs that third-party packages can extend through the "polyxios.codecs" entry point group. Meshes are exposed as a PolyData container of NumPy arrays, with zero-copy memory mapping where a format allows it, and Cython kernels for the hot paths.