The biggest mistake we made is that we conflated operating and operation mode.
Last October, when I was a Home Assistant neophyte (but not a home automation neophyte) I raised this very issue in this thread:
I used MQTT HVAC and was perplexed by the History Chart’s insistence to graph the operation mode (heat/cool/off) as opposed to the operating state (heating/cooling/idle). That’s not very useful and, as a Home Assistant newbie, I felt I must’ve configured something incorrectly. But no, it was a long-standing issue with the underlying climate component.
I looked at the source code of other climate platforms and learned it was left to the component’s author to decide which one of the two (the mode the thermostat is set to use versus what it’s currently doing) would represent the component’s state property. The History Chart graphs the component’s state property (keep this in mind, it will be important in a moment).
Anyway, this arrangement did not meet my concept of a proper History Chart so I created a custom version of MQTT HVAC and have upgraded it several times since October 2018 (to keep up with Home Assistant’s changes).
Fast forward to the present, and the ‘Climate 1.0’ initiative has addressed this issue. The climate component now has a clear separation of ‘church and state’ operation mode and operating state. The climate component’s state property represents the operation mode (auto/heat/cool/off, etc) whereas a separate attribute represents the operating state (heating/cooling).
HOWEVER, there was one little oversight in 0.96.0. Remember when I said the History Chart graphs the climate component’s state property? Well, it continues to do so in 0.96.0. That means it’s graphing the operation mode, not the operating state. Ooops!
That little bug was corrected in 0.96.1. There was also another bug corrected, specific to the Honeywell integration in 0.96.2. You should upgrade to the latest available release which is currently 0.96.2.