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The original was posted on /r/homeassistant by /u/Crafty-Lemon-9743 on 2026-06-29 18:25:45+00:00.
The recent matter.js update has prompted a mini smart home renaissance in our house because devices I've had sitting on the shelf for a year, waiting for matter to be fixed, are now working.
Among other things this involved some door sensors and corresponding automations to turn lights on when doors are opened, fairly standard.
Not everyone in the house is happy about this and I had an unexpected complaint along the lines of
"Is the light in room ___ a smart bulb?"
"Yes...?"
"The light was already on when I went in, has it been on all night?"
Confused, I checked the activity logs and everything is working as expected, door opens, light comes on, door closes, light turns off after a minute delay.
To cut a long story short, it turns out some family members are not quick at opening doors and so by the time the door is open, the light is already on, giving the illusion that the light has been on the entire time.
The fix was a 500ms delay so now people can see the light turning on as they're opening the door, and everyone is happy.
Meanwhile let's just appreciate how a door sensor can speak to home assistant and turn on a bulb fast enough that this is even a problem.