jax-ml/jax · error · ValueError

new enum value must be in {enum_values}, got {new_val} of ty

Error message

new enum value must be in {enum_values}, got {new_val} of type {type(new_val)}.

What it means

The parser created by enum_state rejects any new value set on the flag that is not a str (exact type check, subclasses excluded) or is not in enum_values. It fires when calling the context manager or config update with a bad value.

Source

Thrown at jax/_src/config.py:514

      JIT cache key.
    extra_validator: optional function to validate the value of the config
      option.

  Returns:
    A contextmanager to control the thread-local state value.
  """
  if not isinstance(default, str):
    raise TypeError(f"Default value must be of type str, got {default} "
                    f"of type {getattr(type(default), '__name__', type(default))}")
  name = name.lower()
  default = os.getenv(name.upper(), default)
  if default not in enum_values:
    raise ValueError(f"Invalid value \"{default}\" for JAX flag {name}")
  config._contextmanager_flags.add(name)

  def parser(new_val):
    if type(new_val) is not str or new_val not in enum_values:
      raise ValueError(f"new enum value must be in {enum_values}, "
                       f"got {new_val} of type {type(new_val)}.")
    if extra_validator is not None:
      extra_validator(new_val)
    return new_val

  s = State[str](
      name,
      default,
      help,
      update_global_hook=update_global_hook,
      update_thread_local_hook=update_thread_local_hook,
      parser=parser,
      include_in_jit_key=include_in_jit_key,
      include_in_trace_context=include_in_trace_context,
  )
  config.add_option(
      name, s, 'enum',
      meta_args=[],

View on GitHub (pinned to 1e1c6a8fc0)

Solutions

1. Pass the string member: with my_flag(MyEnum.FOO.value):
2. Double-check the string is one of the enum_values listed in the flag's help

Example fix

// before
with jax.my_flag(MyEnum.FOO):
    ...
// after
with jax.my_flag('foo'):
    ...

if not (type(new_val) is str and new_val in enum_values):
    raise ValueError(f'expected one of {enum_values}, got {new_val!r}')

def is_enum_value(v, values) -> bool:
    return type(v) is str and v in values

try:
    with my_flag(val):
        ...
except ValueError as e:
    if 'new enum value' in str(e):
        val = DEFAULT; my_flag(val).__enter__()

When it happens

Trigger: with my_flag(MyEnum.FOO): ... (Enum member instead of its string value), or jax.config.update('my_flag', 'invalid').

Common situations: Programmatically toggling an enum-backed flag (profiler trace level, compilation cache mode) with an Enum object or a typo'd string.

Understand the failure class

Background: "Invalid value" and "allowed values are" config errors: what your library rejected and how to fix it — this error's family across 41 libraries.

Related errors

• Invalid value "{default}" for JAX flag {name}
• new enum value must be None or in {enum_values}, got {new_va
• Invalid value "{default_str}" for JAX flag {name}
• Default value must be of type str, got {default} of type {ge
• Default value must be of type str or None, got {default} of

AI-assisted analysis of jax-ml/jax@1e1c6a8fc0 (2026-08-27). Data as JSON: /api/errors/cc9341b183b56a34. Report an issue: GitHub.