keras-team/keras · error · RuntimeError

Backend '{backend.backend()}' must implement the Trainer cla

Error message

Backend '{backend.backend()}' must implement the Trainer class.

What it means

Error "Backend '{backend.backend()}' must implement the Trainer class." thrown in keras-team/keras.

Source

Thrown at keras/src/models/model.py:37

from keras.src.trainers import trainer as base_trainer
from keras.src.utils import io_utils
from keras.src.utils import summary_utils
from keras.src.utils import traceback_utils

if backend.backend() == "tensorflow":
    from keras.src.backend.tensorflow.trainer import (
        TensorFlowTrainer as Trainer,
    )
elif backend.backend() == "jax":
    from keras.src.backend.jax.trainer import JAXTrainer as Trainer
elif backend.backend() == "torch":
    from keras.src.backend.torch.trainer import TorchTrainer as Trainer
elif backend.backend() == "numpy":
    from keras.src.backend.numpy.trainer import NumpyTrainer as Trainer
elif backend.backend() == "openvino":
    from keras.src.backend.openvino.trainer import OpenVINOTrainer as Trainer
else:
    raise RuntimeError(
        f"Backend '{backend.backend()}' must implement the Trainer class."
    )


@keras_export(["keras.Model", "keras.models.Model"])
class Model(Trainer, base_trainer.Trainer, Layer):
    """A model grouping layers into an object with training/inference features.

    There are three ways to instantiate a `Model`:

    ## With the "Functional API"

    You start from `Input`,
    you chain layer calls to specify the model's forward pass,
    and finally, you create your model from inputs and outputs:

    ```python
    inputs = keras.Input(shape=(37,))

View on GitHub (pinned to 7a34a03db6)

When it happens

Trigger: Thrown at keras/src/models/model.py:37 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of keras-team/keras@7a34a03db6 (2026-08-25). Data as JSON: /api/errors/765be2e74ec4981a. Report an issue: GitHub.