For Samsung, there are two steps required. If you’d like, you can try the first one only, and if needed – add the second as well:
Disable Battery optimization* for Bob:
Open the Settings app → Apps → Search and select Bob
Select Battery → Optimize battery usage → on the top-left corner, tap and select All apps
Search for Bob and turn off the switch
Lock** Bob – prevent it from being closed by the OS:
Open the recent apps viewer from the “Square” icon of the Android bottom toolbar
Tap the 3-dots button on the top-right corner, above the apps screenshots, and select “Lock apps”
Find Bob and tap the open-lock icon. This switch it to a lock icon
Alternatively, some newer Samsungs has a different way to do this:
Open the App Switcher from the “3-lines” icon of the Android bottom toolbar
Find Bob and tap the icon on the top of the screenshot
Choose “Lock this app”
*Despite the term “Battery saver”, switching to this state should not change the usage in a significant way. Bob is already optimized to use a very low battery power. In fact, this is actually the guideline of both Android and iOS – not to explicitly close apps (excluding cases such as radio or navigation apps).
** This should not increase the battery usage, as in the background, the app is switched to Suspended mode, which keeps its resources to the minimum. In fact, this is actually the guideline of both Android and iOS – not to explicitly close apps (excluding cases such as radio or navigation apps).