#5804 added the on-disk segment budget to check_bucket_and_object_names, but PUT validates through check_put_object_args, which has its own checks and never calls it. An over-NAME_MAX key therefore still reached the disk layer and came back to the client as ENAMETOOLONG → InternalError 500, exactly the behavior #5785 reported.
Caught by re-running the acceptance suite against the locked build 4b2d79f5d, which contains #5804: S3-003 still failed with a 512-byte key.
Multipart is unaffected — check_new_multipart_args and check_multipart_object_args both route through check_object_args → check_bucket_and_object_names, which already carries the budget.
Verification: new test pins the same boundaries on check_put_object_args (255 ok / 256 rejected, byte-based via CJK, multi-segment long keys ok, __XLDIR__ budget for directory keys); cargo test -p rustfs-ecstore --lib -- bucket::utils 17 passed; cargo clippy -p rustfs-ecstore --all-targets clean; make pre-commit green.
Zhengchao An
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