I thought I understood Matter and Thread. I was wrong. 
My goal was simple: create a stronger Thread mesh for some Meross Matter-over-Thread battery motion sensors. Since mains-powered Thread devices act as routers, I bought Aqara T2 Matter-over-Thread bulbs expecting them to strengthen the same Thread network.
The problem was that they did not.
My setup
-
Homey Self-Hosted Server running on Linux Mint (Matter controller, no Thread radio)
-
eero Thread Border Routers
-
Multiple Amazon Echo devices acting as Thread Border Routers
-
Aqara M3
-
Aqara T2 Matter-over-Thread bulbs:
- GU10 RGB CCT
- E27 White CCT
-
Meross Matter-over-Thread battery motion sensors
-
Onvis Matter-over-Thread switch
The discovery
While commissioning Matter devices through Alexa, I noticed I was being offered a choice of Thread networks.
I could see:
eero-thread-ffc4AqaraHome-C495
The problem became clear: I did not have one Thread network. I had multiple Thread networks.
The Aqara M3 had created its own Thread network, separate from the eero Thread network.
My assumption had been that Matter/Thread devices would naturally combine into one mesh. The reality is that Matter provides interoperability, but the device still has to be commissioned onto the correct Thread network.
The failed attempts
I tried commissioning an Aqara T2 bulb using the Matter QR code and selecting the eero Thread network.
Alexa offered the choice, but commissioning failed at the final stage (credential generation).
I repeated this several times without success.
The breakthrough
I changed one variable.
I:
- Powered down the Aqara M3.
- Powered down the other Aqara Thread bulbs.
- Reset one Aqara T2 bulb.
- Added it through Alexa using the Matter QR code.
- Selected the eero Thread network.
This time it commissioned quickly and successfully.
Alexa showed it connected via an Echo Dot, and Homey Developer confirmed:
d0:7c:27:29:4e:f2:6f:df (eero-thread-ffc4)
The bulb was now genuinely part of the eero Thread network.
Adding it to Homey
I then used Matter Multi-Admin to share the device to Homey.
Homey added it quickly and could control it.
Alexa retained full colour control. Homey currently exposes only on/off and brightness, which appears to be a Homey Matter capability mapping issue rather than a Thread issue.
The unexpected lesson
The key lesson for me:
Matter Multi-Admin shares control of a device. It does not merge Thread networks.
The Thread network is decided during commissioning.
The practical solution was:
Turn off the Thread network you do not want, then commission the device.
Once commissioned onto the desired Thread network, the device stayed there even after the Aqara M3 was powered back on.
Final result
I now have:
eero Thread network:
- Meross motion sensors
- Onvis switch
- Migrated Aqara T2 bulbs
Aqara Thread network:
- Remaining Aqara devices connected through the M3
The process was far more complicated than I expected, but the final solution was surprisingly simple.
Hopefully this helps someone else avoid the weeks of experimentation I went through!
