Matter 1.6.1 Finalises Groupcast
Group addressing moves out of provisional status and becomes the recommended way to command many devices at once, which ends the staggered response that has made Matter look worse than Zigbee in demos.
The Connectivity Standards Alliance has released Matter 1.6.1, a maintenance update on top of June's 1.6. It adds no new device types, and the significant change is that Groupcast is now final rather than provisional, and is the recommended method for handling device groups.
What Groupcast replaces is worth describing, because it explains why this is more than a version bump. Before it, a controller managing groups had to coordinate membership, encryption keys and permissions across several separate clusters, and each group needed its own address. Groupcast uses shared multicast addresses with secure group key filtering, so one command reaches many devices at once and there is no per-group address allocation to run out of.
The user-visible effect has a name: the popcorn effect, where commanding a room's lights produces a visibly staggered ripple as each device is contacted in turn. Lights, fans, thermostats and window coverings are the device classes called out as beneficiaries. Anyone who has demonstrated Matter next to Zigbee knows this is the comparison Matter has been losing, and it was never a radio problem.
The release also adds optional volume and mute controls for doorbell chimes, with a sensible refinement: muting now silences the sound while leaving flashing-light notifications active. Backward compatibility is explicit — existing bindings, groups and automations survive the firmware update.
Two caveats for anyone planning against this. Implementation trails the specification: Groupcast support exists in a draft pull request for Matter.js with no public release date. And "recommended" in a CSA specification is the step before certification test plans change, which is where device and controller firmware schedules actually get set.
The scaling point matters most outside the home. Commercial lighting on a single floor can need hundreds of groups, which is exactly where per-group address allocation became a hard ceiling rather than an inefficiency. For controller vendors there is a simpler benefit: one cluster to implement instead of four.