reflex-dev/reflex · error · ValueError

OTP field `length` is required when passing children explici

Error message

OTP field `length` is required when passing children explicitly.

What it means

The OTP field wrapper auto-generates length input slots only when you pass no children; with explicit children it cannot infer the count, so you must pass length explicitly (as a static int) so it can wire up paste/caret behavior.

Source

Thrown at packages/reflex-components-internal/src/reflex_components_internal/components/base/otp_field.py:179

        Args:
            *children: Optional children to include in place of the default inputs.
            **props: Additional properties to apply to the OTP field root.

        Returns:
            The OTP field component.

        Raises:
            ValueError: If `length` is missing when children are supplied, or
                if `length` is not a positive integer when children are
                auto-generated.
            TypeError: If `length` is not an integer when children are
                auto-generated (a Var can only be used with explicit children).
        """
        if children:
            if "length" not in props:
                msg = "OTP field `length` is required when passing children explicitly."
                raise ValueError(msg)
        else:
            length = props.setdefault("length", 6)
            if not isinstance(length, int) or isinstance(length, bool):
                msg = (
                    "OTP field high-level wrapper requires a static integer `length`."
                    " Pass children explicitly for dynamic lengths."
                )
                raise TypeError(msg)
            if length <= 0:
                msg = "OTP field `length` must be a positive integer."
                raise ValueError(msg)
            children = tuple(OTPFieldInput.create() for _ in range(length))

        return OTPFieldRoot.create(*children, **props)


class OTPField(ComponentNamespace):
    """Namespace for OTP field components."""

View on GitHub (pinned to 45b8ed5ab7)

Solutions

1. Pass an explicit integer: rx.otp_field(*slots, length=4)
2. Or pass no children and use length=N (default 6) to auto-generate slots
3. Remember length must be a static int when children are auto-generated; only explicit-children mode needs the prop here

Example fix

# before
rx.otp_field(rx.otp_field.slot(), rx.otp_field.slot())
# after
rx.otp_field(rx.otp_field.slot(), rx.otp_field.slot(), length=2)

if children and 'length' not in kwargs:
    kwargs['length'] = len(children)
rx.otp_field(*children, **kwargs)

When it happens

Trigger: rx.otp_field(rx.otp_field.slot(), rx.otp_field.slot()) without length=4 — children given but length omitted.

Common situations: Customizing slot rendering (custom separators, styling) by passing children manually and forgetting length; trying to use a Var length (not allowed without static behavior).

Related errors

• OTP field high-level wrapper requires a static integer `leng
• OTP field `length` must be a positive integer.
• ChildrenTypeError(component=cls.__name__, child=child)
• Do not override _add_style directly. Use add_style instead.
• The component `{comp_name}` cannot have `{child_name}` as a

AI-assisted analysis of reflex-dev/reflex@45b8ed5ab7 (2026-08-28). Data as JSON: /api/errors/9533b9a5c9f90f09. Report an issue: GitHub.