To set gruvbox-dark as your permanent default theme in IPython, you need to modify your configuration file.
As of IPython 9.0+, the theme system has been unified. Add or uncomment the following line in your ipython_config.py:

c.TerminalInteractiveShell.theme_name = 'gruvbox-dark'

If you are on an older version of IPython (pre-9.0), you may need to set the highlighting_style instead:

c.TerminalInteractiveShell.highlighting_style = 'gruvbox-dark'

In IPython 9.x, the configuration option theme_name was introduced specifically for the TerminalIPythonApp class, rather than TerminalInteractiveShell. [1, 2] 
To fix the "Config option not recognized" error in your ipython_config.py, change the class prefix from TerminalInteractiveShell to TerminalIPythonApp:

c.TerminalIPythonApp.theme_name = 'gruvbox-dark'

The error occurs because IPython 9.13 (and the 9.x series) [renamed several configuration options](https://ipython.readthedocs.io/en/9.0.2/config/details.html) during the transition to the new theme system. While the command-line flag is --theme, the configuration file parameter for the standard terminal is typically handled by the TerminalInteractiveShell class or its base apps. [1] 
If both TerminalIPythonApp and TerminalInteractiveShell are failing to recognize theme_name, try these two standard methods for IPython 9.x:

In many 9.x builds, the theme is still technically mapped through the high-level highlighting configuration. Try adding this to your ipython_config.py:

c.TerminalInteractiveShell.highlighting_style = 'gruvbox-dark'

To fix this in IPython 9.13, you must use the updated [theme configuration system](https://ipython.readthedocs.io/en/9.0.1/config/details.html) which replaces the now-deprecated highlighting_style. [1, 2] 
The theme_name attribute was recently added to the InteractiveShell class to unify color handling. Update your ipython_config.py with this exact line: [3] 

c.InteractiveShell.theme_name = 'gruvbox-dark'