keras-team/keras · error · ValueError

A KerasTensor cannot be used as input to a JAX function. A K

Error message

A KerasTensor cannot be used as input to a JAX function. A KerasTensor is a symbolic placeholder for a shape and dtype, used when constructing Keras Functional models or Keras Functions. You can only use it as input to a Keras layer or a Keras operation (from the namespaces `keras.layers` and `keras.ops`). You are likely doing something like:

```
x = Input(...)
...
jax_fn(x)  # Invalid.
```

What you should do instead is wrap `jax_fn` in a layer:

```
class MyLayer(Layer):
    def call(self, x):
        return jax_fn(x)

x = MyLayer()(x)
```

What it means

Error "A KerasTensor cannot be used as input to a JAX function. A KerasTensor is a symbolic placeholder for a shape and dtype, used when constructing Keras Functional models or Keras Functions. You can only use it as input to a Keras layer or a Keras operation (from the namespaces `keras.layers` and `keras.ops`). You are likely doing something like: ``` x = Input(...) ... jax_fn(x) # Invalid. ``` What you should do instead is wrap `jax_fn` in a layer: ``` class MyLayer(Layer): def call(self, x): return jax_fn(x) x = MyLayer()(x) ``` " thrown in keras-team/keras.

Source

Thrown at keras/src/backend/common/keras_tensor.py:171

            "You cannot convert it to an int."
        )

    def __float__(self):
        raise ValueError(
            "A KerasTensor is symbolic: it's a placeholder for a shape "
            "an a dtype. It doesn't have any actual numerical value. "
            "You cannot convert it to a float."
        )

    def __array__(self):
        raise ValueError(
            "A KerasTensor is symbolic: it's a placeholder for a shape "
            "an a dtype. It doesn't have any actual numerical value. "
            "You cannot convert it to a NumPy array."
        )

    def __jax_array__(self):
        raise ValueError(
            "A KerasTensor cannot be used as input to a JAX function. "
            "A KerasTensor is a symbolic placeholder for a shape and dtype, "
            "used when constructing Keras Functional models "
            "or Keras Functions. You can only use it as input to a Keras layer "
            "or a Keras operation (from the namespaces `keras.layers` "
            "and `keras.ops`). "
            "You are likely doing something like:\n\n"
            "```\n"
            "x = Input(...)\n"
            "...\n"
            "jax_fn(x)  # Invalid.\n"
            "```\n\n"
            "What you should do instead is wrap `jax_fn` in a layer:\n\n"
            "```\n"
            "class MyLayer(Layer):\n"
            "    def call(self, x):\n"
            "        return jax_fn(x)\n\n"
            "x = MyLayer()(x)\n"

View on GitHub (pinned to 7a34a03db6)

When it happens

Trigger: Thrown at keras/src/backend/common/keras_tensor.py:171 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/0ad0bb4376bc087e. Report an issue: GitHub.