Is there a mypy plugin or other tool to check this via static analysis before runtime? To my knowledge jaxtyping can only be checked at runtime.

I doubt it, since jaxtyping supports some quite advanced stuff:

    def full(size: int, fill: float) -> Float[Array, "{size}"]:
        return jax.numpy.full((size,), fill)

    class SomeClass:
        some_value = 5

        def full(self, fill: float) -> Float[Array, "{self.some_value}+3"]:
            return jax.numpy.full((self.some_value + 3,), fill)