Turning on a Matter air conditioner from Home Assistant could switch it to heating, even if it had been cooling before it was turned off. Pull request #181458, merged into the development branch on 23 October 2026 and marked as a breaking change, fixes that. It is due in Home Assistant 2026.11.

Where the heating came from

Many manufacturers present their air conditioners over Matter as a thermostat rather than as a room air conditioner, because more controllers understand that device type. Home Assistant may then offer both heating and cooling, but no automatic heat/cool mode. In that case, the generic climate.turn_on action ignored the previous mode and picked the first mode in a fixed order: heat/cool, then heat, then cool. Quick toggles on dashboards and voice commands went through that path.

The Matter 1.6 Thermostat cluster has no standard setting for the mode a device should use when turned on, and no command to resume the last mode. Writing SystemMode only changes the current mode.

What changes

From 2026.11, a Matter climate entity remembers its last mode other than off and returns to it when turned on, whether from a dashboard, a voice command or an action. An air conditioner turned off while cooling resumes cooling. Home Assistant reads the mode from the device's SystemMode attribute and keeps it in the entity's restore data, so it survives a restart. If the device reports a mode at startup, that one wins over the stored value.

Calling climate.turn_on on an entity that is already running no longer changes its mode. Devices with a separate power switch, such as Matter room air conditioners, are now actually switched on. Before, Home Assistant only changed the mode, so a unit that was switched off stayed off. If such a device kept its mode while off, only the power goes on and the mode stays untouched.

When Home Assistant knows no previous mode, the old fallback order still applies.

Who needs to check their automations

The change matters if a script or automation relies on climate.turn_on choosing heating or heat/cool on a Matter device. The release note asks you to call climate.set_hvac_mode with the mode you want instead:

action: climate.set_hvac_mode
target:
  entity_id: climate.living_room_ac
data:
  hvac_mode: heat

The author says other integrations already work this way. Z-Wave JS remembers the mode set before turning off, KNX remembers the modes the device reports and Samsung Infrared stores the last mode other than off in restore data.

Tested devices

The change was tested with the Aqara Thermostat W200, an infrared air conditioner bridged by the Aqara Hub M3, another bridged by the SwitchBot Hub 2, and a virtual room air conditioner created with Google's Matter Virtual Device tool.