jax-ml/jax · error · ValueError

new int config value must be None or of type int, got {new_v

Error message

new int config value must be None or of type int, got {new_val} of type {type(new_val)}

What it means

The parser for int_state rejects new values that are not None and not int (bool passes since bool subclasses int; str and float do not). Raised when setting the flag via context manager or config.update.

Source

Thrown at jax/_src/config.py:716

  Returns:
    A contextmanager to control the thread-local state value.
  """
  if not isinstance(default, int):
    raise TypeError(f"Default value must be of type int, got {default} "
                    f"of type {getattr(type(default), '__name__', type(default))}")
  name = name.lower()
  default_env = os.getenv(name.upper())
  if default_env is not None:
    try:
      default = int(default_env)
    except ValueError:
      raise ValueError(f"Invalid value \"{default_env}\" for JAX flag {name}")
  config._contextmanager_flags.add(name)

  def parser(new_val):
    if new_val is not None and not isinstance(new_val, int):
      raise ValueError(f'new int config value must be None or of type int, '
                       f'got {new_val} of type {type(new_val)}')
    if new_val is not None and validator is not None:
      validator(new_val)
    return new_val

  s = State[int](name, default, help, update_global_hook,
                 update_thread_local_hook, parser,
                 include_in_jit_key=include_in_jit_key,
                 include_in_trace_context=include_in_trace_context)
  config.add_option(name, s, int, meta_args=[], meta_kwargs={"help": help})
  setattr(Config, name, property(lambda _: s.value))
  return s


def float_state(
    name: str,
    default: float,
    help: str,

View on GitHub (pinned to 1e1c6a8fc0)

Solutions

1. Convert before setting: int(value)
2. Validate the raw input is an integer string early (e.g. argparse type=int)

Example fix

// before
jax.config.update('jax_my_flag', args.limit)  # argparse str
// after
jax.config.update('jax_my_flag', int(args.limit))

if new_val is not None and (isinstance(new_val, bool) or not isinstance(new_val, int)):
    raise ValueError(f'expected int or None, got {type(new_val)}')

def is_int_or_none(v) -> bool:
    return v is None or (isinstance(v, int) and not isinstance(v, bool))

try:
    jax.config.update('jax_my_flag', val)
except ValueError:
    jax.config.update('jax_my_flag', int(val))

When it happens

Trigger: jax.config.update('jax_my_flag', '128') or with my_flag(3.5): — string or float instead of int.

Common situations: Values sourced from argparse (strings), JSON/YAML configs, or user input being passed to an int-backed flag without conversion.

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_env}" for JAX flag {name}
• Invalid value "{default}" for JAX flag {name}
• new enum value must be in {enum_values}, got {new_val} of ty
• new enum value must be None or in {enum_values}, got {new_va
• Invalid value "{default_str}" for JAX flag {name}

AI-assisted analysis of jax-ml/jax@1e1c6a8fc0 (2026-08-27). Data as JSON: /api/errors/8334e7fa4c3114e3. Report an issue: GitHub.