So in my case, we leave the physical light switches on all the time, we use motion sensors or ZigBee wireless switches to control the lights. If the automation

So in my case, we leave the physical light switches on all the time, we use motion sensors or ZigBee wireless switches to control the lights. If the automation falls over we just switch them on and off using the switches. If family are visiting I switch the house to "guest mode" which deactivates the motion sensors and various other automations and we use the light switches like normal. The term "critical path" is when a whole system depends on that thing to function; it is in the critical path. For example, if I couldn't use the lights at all when the home automation server is down, or your Mac won't run any programs when the phone-home server is down, those things are on the critical path, without them the system fails.