1.6.1

## 🗑️ Deprecated

- **ONNX export simplification removed.** `RFDETR.export(..., simplify=..., force=...)` — both arguments are now no-ops and emit a `DeprecationWarning`. RF-DETR no longer runs ONNX simplification automatically; remove these arguments from your calls. They will be removed in v1.8. (#861)

## 🔧 Fixed

- Fixed `RFDETR.train()`: a missing `rfdetr[train]` install (e.g. plain `pip install rfdetr` in Colab) now raises an `ImportError` with an actionable message — `pip install "rfdetr[train,loggers]"` — instead of a raw `ModuleNotFoundError` with no install hint. (#858)
- Fixed `AUG_AGGRESSIVE` preset: `translate_percent` was `(0.1, 0.1)` — a degenerate range that forced Albumentations `Affine` to always translate right/down by exactly 10%. Corrected to `(-0.1, 0.1)` for symmetric bidirectional translation. (#863)
- Fixed PTL training path: `latest.ckpt` and per-interval checkpoints (`checkpoint_interval_N.ckpt`) are now properly written and restored on resume. (#847)
- Fixed `BestModelCallback` and checkpoint monitor raising `MisconfigurationException` on non-eval epochs when `eval_interval > 1` — monitor key absence is now handled gracefully. (#848)
- Fixed `protobuf` version constraint in the `loggers` extra to guard against TensorBoard descriptor crash (`TypeError: Descriptors cannot be created directly`) with protobuf ≥ 4. (#846)
- Fixed duplicate `ModelCheckpoint` state keys when `checkpoint_interval=1`; `last.ckpt` is omitted in that configuration to avoid collision. (#859)

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## 🏆 Contributors

Thank you to everyone who helped with this release:

* **Jirka Borovec** (@Borda) ([LinkedIn](https://www.linkedin.com/in/jirka-borovec/)) – *Patch fixes: PTL checkpoint restore, BestModelCallback crash, duplicate checkpoint keys, Colab ImportError, protobuf pin, AUG_AGGRESSIVE translation, ONNX simplify deprecation*

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**Full changelog**: https://github.com/roboflow/rf-detr/compare/1.6.0...1.6.1