reflex-dev/reflex · error · ValueError

Cannot set update interval without caching.

Error message

Cannot set update interval without caching.

What it means

Raised when a ComputedVar is declared with cache=False but an update interval is supplied. Caching must be enabled for rx.memo/cache=True before interval-based refresh makes sense, so reflex rejects the combination at decoration time.

Source

Thrown at packages/reflex-base/src/reflex_base/vars/base.py:2980

        initial_value: The initial value of the computed var.
        cache: Whether to cache the computed value.
        deps: Explicit var dependencies to track.
        auto_deps: Whether var dependencies should be auto-determined.
        interval: Interval at which the computed var should be updated.
        backend: Whether the computed var is a backend var.
        **kwargs: additional attributes to set on the instance

    Returns:
        A ComputedVar instance.

    Raises:
        ValueError: If caching is disabled and an update interval is set.
        VarDependencyError: If user supplies dependencies without caching.
        ComputedVarSignatureError: If the getter function has more than one argument.
    """
    if cache is False and interval is not None:
        msg = "Cannot set update interval without caching."
        raise ValueError(msg)

    if cache is False and (deps is not None or auto_deps is False):
        msg = "Cannot track dependencies without caching."
        raise VarDependencyError(msg)

    if fget is not None:
        sign = inspect.signature(fget)
        if len(sign.parameters) != 1:
            raise ComputedVarSignatureError(fget.__name__, signature=str(sign))

        if inspect.iscoroutinefunction(fget):
            computed_var_cls = AsyncComputedVar
        else:
            computed_var_cls = ComputedVar
        return computed_var_cls(
            fget,
            initial_value=initial_value,
            cache=cache,

View on GitHub (pinned to 45b8ed5ab7)

Solutions

1. Remove the interval argument, or
2. Set cache=True (the default) and keep the interval, e.g. @rx.memo(interval=5)

Example fix

# before
@rx.memo(cache=False, interval=5)
def total(self) -> int: ...
# after
@rx.memo(interval=5)
def total(self) -> int: ...

import inspect
sig = inspect.signature(rx.memo)
params = {k: v.default for k, v in sig.parameters.items()}
# in tests: assert not (kwargs.get('cache') is False and kwargs.get('interval') is not None)

When it happens

Trigger: @rx.memo(cache=False, interval=5) or rx.computed(var_name, cache=False, interval=...) — any computed var decorator/signature where cache is explicitly False and interval is not None.

Common situations: Developer disables caching to always recompute, then also tries to add interval throttling; or copies a cached-var example but flips cache to False.

Related errors

• Cannot track dependencies without caching.
• Do not override _add_style directly. Use add_style instead.
• No default value or factory provided.
• UntypedComputedVarError(var_name=fget.__name__)
• Unexpected keyword arguments: {tuple(kwargs)}

AI-assisted analysis of reflex-dev/reflex@45b8ed5ab7 (2026-08-28). Data as JSON: /api/errors/7ebdff1c63980dc6. Report an issue: GitHub.