Activity vs. Workout

So far I’ve only used Xert indoors with prescribed workouts. Is Activity normally used to monitor outdoor rides if you aren’t using a GPS?
Is anyone using Activity with trainer control to just ride or to confirm current FTP or to generate a breakthrough?

Correct, ‘Activity’ is simply to record a ride, akin to a cycling computer. ‘Workout’ is a structured workout… If using the workout feature on Android, be sure to select ‘End Activity’ to save the Activity & the Workout!

The other day when the server was down I decided to make best use of the time.
At first I played with my Halcyon’s mobile app that includes a % resistance slider plus a default ERG workout which can be user-defined. Then I decided to switch to the Xert Android app and play with the Activity option.
Resistance started at the level I had set on the Halcyon app – low watts at a low cadence. After a 10 minute warm-up I decided to up the watts but couldn’t figure out how to do that on the mobile app(?).
I noticed cadence increased watts so I started spinning up every minute or so to see how high it would go. It appears the app knows how much watts you can crank out and keep spinning until you can’t. As watts rise the number goes from green to yellow to red and eventually you’ll top out at whatever cadence/watts you can maintain. I didn’t push it too far and scaled down once I reached 105 rpm.
After a few minutes of cooldown I ended the ride to see if the server was back up. It wasn’t, but when I ran the mobile app a few hours later it identified the workout activity as “GC Specialist”(?) with an upload icon. That worked fine.
I earned a breakthrough medallion. Just a single watt higher but I understand why that occurred.
What I’m unclear on is how the Xert mobile app provides this type of workout with trainer control during an Activity. What process is working in background to raise watts based on cadence in a graduated fashion? Is this Bioshift in reverse?
The activity in this case has all the merits of a self-administered RAMP test as long as you raise cadence a little bit every minute until you can’t go higher or hold it.

It sounds like you had it set to resistance (aka ‘slope’) mode, is that right? Slope mode means it sets the mechanical resistance of the unit, and then changes in wheel speed (through cadence or gear) results in more/less resistance.

Okay, that makes sense.
I have only used the trainer for ERG workouts in the past. Today I tested the Halcyon on its own before a Xert workout.
When you start pedaling the trainer auto-calibrates and defaults to 27% resistance according to the STAC Control Panel app.
As you increase cadence the resistance rises based on the speed of the rear rim passing through the magnetic jaws.
Is it just a coincidence that 105 rpm was getting close to the maximum watts I could generate on a RAMP test?
Do other smart trainers operate in the same way?
Is resistance mode how you would ride a Xert workout without trainer control?
Start the trainer in resistance mode then spin up/dpwn to match watts in the workout chart?

Yup. I was using a “dumb” resistance trainer while my KICKR was broken. You just change gears and cadence to match the power target in the workout.