Updated: 2026-10-05 · Applies to: Thread (Thread Group); Home Assistant 2026.x with the OTBR app; ZBT-2 from HA 2025.10.1

Thread

What it is: A low-power mesh protocol for IoT in homes and buildings. Like Zigbee it runs on IEEE 802.15.4, but it is an open IPv6-based protocol with network-layer security. Thread Group By itself it doesn't control devices. It's only a transport; control is handled by a higher-level protocol, typically Matter or Apple HomeKit. HA docs

How it works

Low power, low bandwidth: ideal for battery devices and things that send little data (switches, motion sensors). HA docs
IPv6-only: devices communicate over IPv6 inside and outside the mesh. HA docs
A border router connects the Thread network to other IP networks (Wi-Fi, Ethernet). Without one, the Thread network can't reach other networks. OpenThread It only forwards packets, doesn't see their content and doesn't control devices. HA docs Minimally it supports: OpenThread
- bidirectional IP connectivity between Thread and Wi-Fi/Ethernet,
- service discovery (mDNS on Wi-Fi/Ethernet, SRP on Thread),
- merging Thread partitions over IP (Thread-over-infrastructure),
- external commissioning, e.g. from a phone.
Multiple border routers in one network: they increase coverage and remove the single point of failure. HA docs
OpenThread is Google's open-source Thread implementation and almost all border routers are built on it. Its border router (OTBR) uses an RCP design: the radio only does sub-MAC and PHY, the rest runs on the host. It also offers NAT64 for IPv4 networks. OpenThread HA docs

Versions and standards

The standard is maintained and certified by the Thread Group (commissioning, network functionality, interoperability). The vendor picks the application layer separately. Thread Group
HA can use any border router but can configure only OpenThread with the REST API (the OpenThread Border Router app). According to the docs the Thread integration in HA is still a work in progress. HA docs

Gotchas

Separate vendor networks: HA, Apple and Google each create their own Thread network with different credentials, and devices don't roam between them. Credentials can be imported into HA via the Companion app, and a new HA border router can join an existing network. HA docs
Channel: Thread channels 11–24 can overlap with 2.4 GHz Wi-Fi (1, 6, 11). The least affected is channel 26, 25 can also help. Change the channel ideally before adding devices; some won't move to the new channel by themselves. Interference shows up in the log as ChannelAccessFailure. HA docs Wi-Fi channels: see Wi-Fi 7.
IPv6 on the network: HA must have working IPv6. Mesh Wi-Fi that aggressively filters multicast can block mDNS discovery of the border router. HA docs
Thread logo ≠ Matter: a Thread device may use HomeKit or a proprietary protocol. HA docs
The ZBT-2 adapter supports both Thread and Zigbee, but only one protocol at a time. It can be switched later. ZBT-2 docs
Unlike Zigbee, the adapter stores nothing in Thread mode; all network data is held by Home Assistant. That is why the reset button has no effect in Thread mode. ZBT-2 docs

Implementation and integrations

Home Assistant: the Thread integration appears automatically when HA detects a border router. HA becomes a border router with the OpenThread Border Router app and a Thread radio (Yellow, Connect ZBT-1/ZBT-2). HA docs
The ZBT-2 with OpenThread RCP firmware works as a border router with the OTBR app in HA. ZBT-2 docs
SMLIGHT SLZB (SLZB-OS) in OpenThread Border Router mode: connects Thread devices (e.g. Matter over Thread) to the home network, typically with HA, Google Home or Apple HomeKit. SLZB-OS manual
Border routers from other ecosystems: Google (Nest Hub 2nd gen, Nest Hub Max, Nest Wifi Pro, Google TV Streamer), Apple (HomePod 2nd gen, HomePod mini, Apple TV 4K 2nd and 3rd gen), plus Nanoleaf and Amazon. HA docs

Zigbee: same radio (802.15.4), but without IP
Matter: application layer on top of Thread
Wi-Fi 7: shared 2.4 GHz band

Sources