reflex-dev/reflex · warning · UserWarning

Do not override _add_style directly. Use add_style instead.

Error message

Do not override _add_style directly. Use add_style instead.

What it means

The style application pipeline in the builtin plugin (_apply_style) detects that a Component subclass overrode the private _add_style method instead of the public add_style hook. The private method is reserved for framework internals; overriding it breaks style composition, so Reflex raises a UserWarning as an error.

Source

Thrown at reflex/compiler/plugins/builtin.py:236

    @staticmethod
    def _apply_style(
        comp: Component, style: ComponentStyle, page_context: PageContext
    ) -> Component | None:
        """Apply app-level styles to a single component.

        Args:
            comp: The component to style.
            style: The app-level component style map.
            page_context: The active page context, used to obtain a page-local
                clone before rewriting ``style``.

        Returns:
            A page-local clone with the merged style, or ``None`` when the
            component has no type-level or app-level style to apply.
        """
        if type(comp)._add_style != Component._add_style:
            msg = "Do not override _add_style directly. Use add_style instead."
            raise UserWarning(msg)

        new_style = comp._add_style()
        component_style = comp._get_component_style(style)
        if not new_style and not component_style:
            return None

        style_vars = [new_style._var_data]
        if component_style:
            new_style.update(component_style)
            style_vars.append(component_style._var_data)
        new_style.update(comp.style)
        style_vars.append(comp.style._var_data)
        new_style._var_data = VarData.merge(*style_vars)

        owned = page_context.own(comp)
        owned.style = new_style
        return owned

View on GitHub (pinned to 45b8ed5ab7)

Solutions

1. Rename the override from _add_style to add_style in your custom component
2. Check Reflex docs/changelog for the current style-extension API for your version
3. If extending a built-in component, call super().add_style() appropriately

Example fix

# before
class MyComp(rx.Component):
    def _add_style(self):
        return {"padding": "1em"}
# after
class MyComp(rx.Component):
    def add_style(self):
        return {"padding": "1em"}

assert not ("_add_style" in MyComponent.__dict__), "override add_style, not _add_style"

def uses_public_style_hook(cls) -> bool:
    return "_add_style" not in cls.__dict__

When it happens

Trigger: Creating a custom Component subclass that defines _add_style() (matching it against Component._add_style via identity check). Overriding add_style() is the supported API.

Common situations: Component library authors copying internal Reflex component source that used _add_style, or code written against an older Reflex API where _add_style was the extension point.

Related errors

• Var-returning `@rx.memo` `{func_name}` cannot depend on hook
• Component-returning `@rx.memo` `{fn.__name__}` must return a
• Expected a Component, got {component_called!r} of type {type
• Only one of `data` or `fp` may be provided, not both.
• At least one of `data` or `fp` must be provided.

AI-assisted analysis of reflex-dev/reflex@45b8ed5ab7 (2026-08-28). Data as JSON: /api/errors/47d5cc34b9a91457. Report an issue: GitHub.