public enum HeatingCoolingMode

Maintaining a band between Trait.TARGET_HEATING_TEMPERATURE and Trait.TARGET_COOLING_TEMPERATURE, choosing for itself which to run.

A target only. Trait.CURRENT_HEATING_COOLING never reports it, because at any given moment the thermostat is heating, cooling or idle – “auto” describes the policy, not the state.

While this is the target, Trait.TARGET_TEMPERATURE reports no value: there is no single setpoint to report, and answering with either threshold would silently be the wrong one half the time.

A mode this API cannot name, carried so it is not misreported as something it is not.

Matter’s thermostat has EmergencyHeat, Precooling, FanOnly, Dry and Sleep, none of which HomeKit can express and none of which have a portable meaning. Folding them into OFF would tell an app a running dehumidifier is idle. Read TraitValue.getRawPlatformValue() for Matter’s own ordinal when you need to know which.

Writing this is rejected with HomeError.INVALID_ARGUMENT – an API that cannot name a mode cannot ask for it either.

Reads a mode out of a trait value, total: a value that is not an enum, or whose ordinal is outside this set, answers OFF.

OFF rather than OTHER as the fallback, deliberately: OTHER means “the accessory named a mode we cannot express”, which is a claim about the accessory. A value this code could not read at all is not evidence of that.