but in google assistant it shows all available modes including eco, auto, etc.
I’ve check the javascript code an it seems that the modes shold be taken from defined list and if it’s empty it gets all options set with a let clause. But it should not be the case.
I guess you’ve configured this using the GUI/WebUI?
In the latest version for the Google Assistant integration the parameter modes has been renamed to thermostatModes.
(cf. Migration Guide · openhab/openhab-google-assistant · Discussion #558 · GitHub)
The WebUI seems to still use the old naming for the predefined field.
You should be able to manually rename/define the parameter using the code editor.