Having a nightmare trying to get Matter bulbs to turn on to both a specific brightness AND color temp at the same time - only one attribute gets applied, and HA optimistically reports that both attributes have been applied. So if I want lights to come on dim and warm in the evening (from off) it won't work. From what I have read, it seems likely that the Matter server is using MoveToLevelWithOnOff and MoveToColorTemperature commands rather than attribute_writes. Has anybody found a solution to this and does Matter.js improve things?
#Writing multiple light attributes with Matter
brave bough
minor saddle
The commands are the correct way to tell the bulbs to change brightness or color. The relevant attributes (such as CurrentLevel on the Level Control cluster) are read-only.
Either you have a bulb which is buggy and cannot handle commands for level and color arriving in quick succession, or there is a problem with your network that is causing some of the commands to get lost.
The expected command sequence for this is that HA will send a MoveToColorTemperature command with the "ExecuteIfOff" bit set to change the color temperature without turning the bulb on, then send the MoveToLevelWithOnOff command to actually turn the bulb on (possibly with a transition/fade).
brave bough
It should definitely be possible for these bulbs (Ikea kajplats) - if I control them in Apple Home I can turn them on to a new colour and brightness without any transitions at all, so whatever implementation Apple are using works
minor saddle
All I can say is that the matter integration is sending the correct command sequence to achieve that, to my understanding. It might be informative to share the matter server logs while this issue is happening.