ds[np.array(1)] went down the index-list path, where tolist() returns a scalar and extracting a list of indices raised a confusing TypeError. h5py treats it as an integer index; so do we now. The h5py comparison keys include 0-d arrays (signed and unsigned) on each axis; they failed before. Co-Authored-By: Claude Opus 5.5 (1M context) <[email protected]>