Textualize/textual · error · ActiveModeError

Can't remove active mode

Error message

Can't remove active mode {mode!r}

What it means

ActiveModeError raised by App.remove_mode when trying to remove the currently active mode. The active mode owns the live screen stack and cannot be deleted out from under the app.

Solutions

1. Switch away first: await app.switch_mode("main") then await app.remove_mode("editor")
2. When iterating, skip the current mode

Example fix

# before
for mode in list(app._modes):
    await app.remove_mode(mode)  # hits active mode

# after
for mode in list(app._modes):
    if mode != app._current_mode:
        await app.remove_mode(mode)

if mode != app._current_mode:
    await app.remove_mode(mode)

try:
    await app.remove_mode(mode)
except ActiveModeError:
    await app.switch_mode('main')
    await app.remove_mode(mode)

When it happens

Trigger: await app.remove_mode(app._current_mode), i.e. removing the mode you are currently in.

Common situations: Cleanup routines that iterate all modes; removing a mode from within one of its own screens.

Related errors

• add_mode() must be called with a Screen type, not an…
• App is not running
• Cannot use '_default' as a custom mode.
• Duplicated mode name
• expected a callable or string, got

AI-assisted analysis of Textualize/textual@06dbeef4bb (2026-08-27). Data as JSON: /api/errors/9ced5385cc9cb8b5. Report an issue: GitHub.

Appendix: source

Thrown at src/textual/app.py:2712

                "add_mode() must be called with a Screen type, not an instance"
                f" (got instance of {type(base_screen).__name__})"
            )
        self._modes[mode] = base_screen

    def remove_mode(self, mode: str) -> AwaitComplete:
        """Removes a mode from the app.

        Screens that are running in the stack of that mode are scheduled for pruning.

        Args:
            mode: The mode to remove. It can't be the active mode.

        Raises:
            ActiveModeError: If trying to remove the active mode.
            UnknownModeError: If trying to remove an unknown mode.
        """
        if mode == self._current_mode:
            raise ActiveModeError(f"Can't remove active mode {mode!r}")
        elif mode not in self._modes:
            raise UnknownModeError(f"Unknown mode {mode!r}")
        else:
            del self._modes[mode]

        if mode not in self._screen_stacks:
            return AwaitComplete.nothing()

        stack = self._screen_stacks[mode]
        del self._screen_stacks[mode]

        async def remove_screens() -> None:
            """Remove screens."""
            for screen in reversed(stack):
                await self._replace_screen(screen)

        return AwaitComplete(remove_screens()).call_next(self)

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