1.5.1

## 🚀 Added

- **Nested Albumentations transforms.** `OneOf` and `Sequential` containers now work correctly inside the augmentation pipeline. Probability settings on container transforms are ignored — they always fire, keeping composition predictable. Inference pipelines can also pass `None` targets so the same transform object works for both training and inference. (#752)

    ```python
    from rfdetr import RFDETRSmall

    model = RFDETRSmall()
    model.train(
        dataset_dir="...",
        aug_config={
            "OneOf": [
                {"RandomBrightnessContrast": {"p": 0.5}},
                {"HueSaturationValue": {"p": 0.5}},
            ],
            "HorizontalFlip": {"p": 0.5},
        },
    )
    ```

## 🌱 Changed

- Dataset transform pipeline now uses torchvision-native `Compose`, `ToImage`, and `ToDtype` instead of custom implementations. `Normalize` defaults to ImageNet mean/std. (#745)

## 🔧 Fixed

- Fixed `RFDETRMedium` missing from the public API — `__all__` contained a duplicate `RFDETRSmall` entry instead. (#748)
- Fixed `AR50_90` reporting an incorrect value in `MetricsMLFlowSink` due to a wrong COCO evaluation index. (#735)
- Fixed supercategory filtering in `_load_classes` for COCO datasets with flat or mixed supercategory structures. (#744)
- Fixed a crash in geometric transforms (flip, crop, etc.) when a sample contains zero-area / empty masks. (#727)
- Fixed segmentation training on Colab — `DepthwiseConvBlock` now disables cuDNN for depthwise separable convolutions. (#728)
- Locked `onnxsim` to `<0.6.0` to prevent `pip install` from hanging indefinitely. (#749)

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## 🏆 Contributors

A special welcome to our new contributors and a big thank you to everyone who helped with this release:

* **tillfri** (@tillfri) – *Fix AR50_90 metric index in MLflow sink*
* **justin-alt-account** (@justin-alt-account) – *Fix `RFDETRMedium` missing from `__all__`*
* **Jirka Borovec** (@Borda) ([LinkedIn](https://www.linkedin.com/in/jirka-borovec/)) – *Nested Albumentations support, transform pipeline refactor, mask fix, supercategory fix, onnxsim pin, CI/testing infrastructure*

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**Full Changelog**: https://github.com/roboflow/rf-detr/compare/1.5.0...1.5.1