[AHMETHAKANBEZIR1]

Subspace documents an integer or tuple of feature indices, but Subspace((0, 2), kernel) indexes each 1D coordinate with a multidimensional tuple and raises IndexError. List indices, also allowed by the Sequence[int] annotation, are rejected by JAX indexing.

Convert a sequence of feature indices to an index array before selecting coordinates. Preserve the existing scalar-integer path, including its scalar result.

Validation on Windows / Python 3.12.14 / JAX 0.12.0 / Equinox 0.13.8, CPU:

• On unchanged main: 8 failing cases / 1 passing singleton-tuple control; all nine pass after the fix.
• New and existing transform tests: 14 passed.
• Full suite with default float32: 179 passed, 2 skipped; with JAX_ENABLE_X64=1: 179 passed, 2 skipped. The skips are optional george/celerite comparisons.
• Source doctests: 3 passed. Configured pre-commit hooks and git diff --check pass; a news fragment is included.

Tests cover tuples/lists, reordered, negative, and singleton feature selections. A weighted-coordinate RBF reference checks covariance values and input gradients under JIT; a GP likelihood is compared with the explicitly selected covariance.

Prepared autonomously with OpenAI Codex, including code and tests; no independent human review is claimed.