Buy an Apple TV, a Nest Hub and a SmartThings hub, and you probably own three Thread border routers. There is a good chance you also have three separate Thread networks. Each one carries only the devices that were added through its own ecosystem, and a mains-powered plug in one network will not relay traffic for a sensor in another.

Thread 1.4 adds a standard way to fix this, and in 2026 the big platforms finally started shipping it. It still does not happen on its own, and you need to know what you are merging before you start.

What makes two border routers part of the same network

A Thread network is defined by its security credentials, not by the radio range of its devices. The OpenThread primer puts it in one line: security credentials define the Thread network, and radio connectivity only decides how it splits into partitions. The credentials sit in what Thread calls the operational dataset: the network key, the network name, the PAN ID and extended PAN ID, the channel and a few other parameters.

A border router connects the Thread mesh to your Wi-Fi or Ethernet network. According to OpenThread, it has to provide at least four things: two-way IP connectivity, service discovery in both directions (mDNS on the home network, SRP inside the mesh), Thread over infrastructure to join partitions over IP links, and external commissioning, for example from a phone. It does not decide what your devices do. Control comes from Matter or Apple HomeKit running on top.

When a new border router is set up, it either receives an existing dataset or creates a new one. If it creates one, you have a new network. The Thread Group describes both outcomes:

  • If the border routers share credentials, all Thread devices form one mesh. Every mains-powered device that can route helps extend it, and several border routers give you redundant exits to the home network.
  • If they don't, each border router forms its own mesh, and each mesh only uses the routing devices that joined it.

The Thread Group also points out that devices in separate Thread networks can still talk to each other over IP. You lose range and redundancy, not basic function. In a small flat with a strong border router you may never notice. In a large house with a lock at the far end of the garden, three thin meshes are worse than one dense one, and the Home Assistant Thread documentation says the same: devices cannot roam between separate networks, and a denser mesh gives better link quality and lower latency.

Why it happened in the first place

Thread itself was never the problem. Border routers are configured by their own ecosystem, and before Thread 1.4 there was no standard way for one vendor's border router to get the dataset that another vendor created. Credentials were kept in each platform's own store: the iOS keychain, your Google account, Amazon's Credential Locker. Apple and Google did share credentials through their phone APIs, so a Google border router set up from a phone that already knew the Apple network could join it. Google's help page for the Google TV Streamer shows this: on iPhone, the Google Home app asks whether to join the existing iOS Thread network or create another one. If you tap "Don't Allow", you get a second network.

Other platforms were less open, and setup apps often just formed a fresh network because they could not see any credentials.

What Thread 1.4 adds

The Thread Group published Thread 1.4 in September 2024. For home users, its most visible feature is credential sharing between ecosystems. The 1.4 white paper describes the flow:

  1. You start sharing on the border router that already runs the network, usually from its app or settings, after the vendor confirms it is you.
  2. The border router generates a one-time passcode and shows it as a QR code or a nine-digit number.
  3. You scan or type the code into the other app (the candidate). Both sides derive a temporary key from it and open an encrypted DTLS session.
  4. The candidate reads the active and pending operational datasets, which means the network key, channel, PAN ID and the rest.
  5. Sharing mode ends when the candidate disconnects or a timeout runs out.

After that, the new border router can join the existing network instead of creating its own, and the phone can store the credentials for adding devices later.

Two things follow from this. Sharing is something you start by hand, so having a Thread 1.4 border router does not mean anything merges on its own. And both sides need to support it: the network's owner has to offer the code, and the app on the other side has to accept it.

Thread 1.4 also brings Thread over infrastructure, which lets border routers carry Thread traffic over Wi-Fi or Ethernet between distant parts of the mesh, plus standard diagnostics and a defined path to the internet through the border router. According to The Verge, citing the Thread Group, applications to certify new border routers on Thread 1.3 closed at the end of 2025, and since 1 January 2026 only Thread 1.4 is available for border router certification. That rule applies to new products, not to firmware already running in your home.

Where the big platforms stand (October 2026)

Support has been arriving in stages, and it is worth checking the current state for the exact device you own:

  • Google: in June 2026 the Google TV Streamer got a Thread 1.4 update with a "Share Thread network credentials" option under Settings > Network & Internet. It asks you to confirm your identity and then shows a QR code and a sharing code. The screen warns that the code gives the receiving app administrative access to the network, so it should only go to apps you trust. In August 2026 Android Authority reported, based on user reports, that Nest Hub, Nest Hub (2nd gen), Nest Hub Max and Nest Wifi Pro were also receiving Thread 1.4. Google had not announced it.
  • Apple: Thread 1.4 appeared on the Apple TV in the tvOS 27 developer beta in June 2026. At that point The Verge found no option to share credentials in the beta. The iOS 27 SDK includes an API that asks a nearby Apple TV running tvOS 27 to enter sharing mode and return a nine-digit one-time code, which means apps can start sharing with your permission. Apple's own Home app had no visible button for it when The Verge looked.
  • Samsung SmartThings: since October 2025, select hubs (including the Aeotec Smart Home Hub and Smart Home Hub 2) can join another ecosystem's network with a QR code or one-time code, or share their own network the same way. The menu is "Manage Thread Network", with "Join another network" and "Share SmartThings network".
  • Amazon: Amazon's developer documentation lists its Echo and eero border routers as Thread 1.1 or 1.3. Instead of the 1.4 flow, it offers the Credential Locker API, which lets Alexa add-ons read Thread credentials with your consent. In June 2026 The Verge reported that Amazon had promised Thread 1.4 for this year.
  • Home Assistant: the Thread panel lists every border router it finds through mDNS, grouped by network, and shows which credentials it knows. The companion app can send credentials from the phone to Home Assistant and back. An OpenThread border router added in Home Assistant joins the preferred network if it does not have a network of its own yet.

Check how many networks you have

Border routers announce themselves on the local network as the _meshcop._udp service. The TXT record includes the network name (nn), the extended PAN ID (xp), the Thread version (tv) and the vendor and model names (vn, mn). On a Linux computer on the same network, this lists them:

avahi-browse -rt _meshcop._udp

On a phone or Mac, any DNS-SD browser app shows the same records. Group the results by extended PAN ID. One value means one network. Three values mean three networks, whatever the names say. The tv field tells you which border routers already run 1.4. If you use Home Assistant, the Thread panel shows the same grouping without the command line.

Merge them, step by step

  1. Pick the network to keep. Choose the ecosystem whose border routers cover the house best and whose devices you have the most of. Moving devices to another network usually means removing them and adding them again, so keep the network that holds most of them.
  2. Update everything first. Credential sharing needs Thread 1.4 on the border router that shares, and support in the app that receives.
  3. Use the sharing flow where it exists. On the border router that owns the network, start sharing (on a Google TV Streamer: "Share Thread network credentials"), then scan the QR code or enter the code in the other app, such as SmartThings with "Join another network". Do it within the time limit, and only with apps you trust: the code gives administrative access to the network.
  4. Where it doesn't, go through the phone. Apple and Google border routers have long used the phone's credential store. Setting up a new border router from a phone that already knows the main network gives it the chance to join. When an app asks whether to use an existing Thread network, say yes.
  5. Move devices if you have to. A device stays on the network it was commissioned into. If an important device sits on the wrong network, remove it from that ecosystem and add it again once the border routers share a network.

Problems that have nothing to do with credentials

Merging networks does not help if the border router cannot reach the rest of the home network properly:

  • Keep border routers and controllers on the same network segment. Discovery runs on mDNS. Google's troubleshooting steps ask you to check that the phone and border router are on the same Wi-Fi network, and Nuki says the same for its Matter over Thread lock. If you split the house into VLANs, keep border routers, hubs and the phones you use for setup on the same one, or make sure mDNS and IPv6 cross the boundary.
  • Thread needs IPv6. Thread is an IPv6-only protocol, and the Home Assistant documentation warns that devices can join the mesh but stay unreachable when IPv6 is missing anywhere on the path: on the host, in Docker, in a virtual machine or in the router.
  • Wi-Fi interference. Thread uses the same 2.4 GHz band as Wi-Fi. Home Assistant's documentation says Thread channels 11-24 can overlap with common Wi-Fi channels and recommends channel 26 when Wi-Fi traffic is heavy. In a merged network, the network owner sets the channel.
  • A phone is not a border router. Nuki warns that some iPhones with a Thread radio (15 Pro, 16, 16 Pro, 17, 17 Pro) can create a temporary Thread network during pairing. A lock added that way loses its connection when you leave home, the phone runs out of battery or it turns that network off. You still need a permanent border router.

Is it worth the effort?

If everything responds quickly and nothing drops out, several networks are not a problem you have to fix today. The Thread Group itself wrote in 2023 that most users would not see a practical issue with several meshes. Merging pays off in larger homes, with battery devices at the edge of range, and when the routing devices you own (plugs, bulbs, blinds) are spread across ecosystems so none of them forms a decent mesh. In that case, pick one network now and add every new Thread device to it. That is easier than sorting it out later.