Require bitsandbytes>=0.50.0 and drop the _check_is_size warning filter

[behroozazarkhalili]

Resolves #6447.

What

Raises the bitsandbytes floor to >=0.50.0 in the quantization and dev extras, and removes the pytest filter that silenced its _check_is_size FutureWarning.

Why the trigger has fired

bitsandbytes replaced every torch._check_is_size call with torch._check in bitsandbytes-foundation/bitsandbytes#1940, merged 2026-05-07 and shipped in 0.50.0 (2026-07-25). Counted directly at the release tags rather than inferred from dates:

tag	_check_is_size in bitsandbytes/_ops.py
0.49.2	8
0.50.0	0
0.50.1	0

The resolver already picks up 0.50.1 today, so the filter is dead in practice. Recording the minimum is what makes that a guarantee instead of a coincidence, which is the condition the issue names.

Verification

Applying each version of the filterwarnings list programmatically and then calling torch._check_is_size(1):

pyproject	filter entries	warning surfaced
before	14	no
after	13	yes

Exactly one entry is removed and it is the intended one. Boundary check on the new specifier: 0.49.2 does not satisfy >=0.50.0, 0.50.0 and 0.50.1 do. Both requirement strings parse as valid PEP 508. pytest --collect-only still loads the config (231 tests collected in tests/test_utils.py).

Scanning the installed environment, only bitsandbytes and torch itself call _check_is_size. torch's remaining callers are in fx/passes/runtime_assert.py, fx/experimental/symbolic_shapes.py, _dynamo/trace_rules.py, and export/_patches.py, none of which sit on TRL's eager training path, so removing the filter does not unmask a second source.

Out of scope

The other bitsandbytes filter, inner dimension (\d+) is not aligned for fast kernel, stays. Its upstream issue bitsandbytes-foundation/bitsandbytes#2027 is still open, so its "remove once" condition has not been met.

Sibling issue #6466 is not yet actionable either: it needs triton >= 3.8.0 and the latest release on PyPI is 3.7.1.

---

Note

Low Risk
Dependency floor and pytest warning-filter cleanup only; no runtime or security logic changes. Users on bitsandbytes < 0.50.0 will need to upgrade when using the quantization extra.

Overview
Pins bitsandbytes to >=0.50.0 in the quantization and dev extras so the library no longer uses deprecated torch._check_is_size.

Removes the matching pytest filterwarnings entry for that FutureWarning, which is fixed upstream in 0.50.0. Other bitsandbytes warning filters are unchanged.

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