I never got AI workout on my side. Every time I just got “AI workout could not be generated” message. Do I need to set up anything before using it?
Nothing to set up. But maybe you can share the XSS target (low, high, peak) for a workout it cannot generate?
I suppose that is “Optional XSS”? If that is the case, then it is “(183 | 0.0 | 0.0 )”. Probably the 0.0 here is the issue?
Maybe you can share a screenshot?
Is there a limited time constraint for the day? I don’t think it’s possible to do 183 low stain in under 2.5 hours.
The workout generator only cares about the XSS targets and difficulty as far as I know. Not how long time it takes. It will basically adjust the interval targets, durations and number of intervals to match the XSS targets without a too high difficulty.
I believe @blairc is correct that 3 hours is beyond what the current version Autogen is intended to create.
What is your status stars count?
Autogen is typically used to create a HIT workout to ride indoors when the suggested list is limited in scope or a simplified HIT workout to ride outdoors.
The Library primarily consists of workouts in the 30 minute to 2 hour range.
However, for a long duration LIT workout you really don’t need a specific workout.
(183 | 0.0 | 0.0 ) means a low strain endurance workout with no high or peak strain.
183 XSS = 3 hours @ 60 XSS/hour (Moderate Difficulty) or 3-1/2 hours Easy (40-50 XSS/hr).
Indoors you could select this Free Ride workout and ride it in Slope mode hovering around LTP while watching whatever you want on the big screen. Or this workout under ERG control (AUTO).
Outdoors would be Z2 ride for ~3 hours or however long it takes to reach ~180 XSS.
That screen indicates you have completed your training today and currently have a surplus.
There is no workout you need to select or one to generate.
1 XSS remaining can be ignored.
Your screenshot indicates tomorrow’s recommendation will be an endurance workout (form = yellow/tired).
Let’s say that advice is going to be 95 XSS Endurance at 2-diamond difficulty and your availiability is 90 minutes.
First off there should be plenty of endurance level workouts to choose from in that range but you should also be able to run Autogen.
If Autogen cannot be run successfully at the beginning of any day to create an alternate workout, you should file a support request with support@xertonline.com.
Thank all for the comments. I think I understand how it works now. I figured I need to remove the planned workout from the planner first, and then regenerate using AI.
Good to know Autogen works for any duration.
I doubt I’ll ever use Autogen for endurance workouts considering there are better options.
Your examples demonstrate how simple workouts can achieve the strain goal for the day without any need to load a workout on a head unit.
While some may prefer to do that I’d elect to perform the Climber workout outdoors by riding 3+ hours and inserting 8-10 short intervals at or above my 10-minute power with plenty of easy pedaling in-between.
For Pure Endurance I’d simply ride below LTP as much as possible for 3+ hours.
Indoors I’m unlikely to enjoy 3 hours on a trainer. 
Outdoors OTOH would be fun.
Garmin owners can alternately monitor XSS Buckets or the Dashboard app to accomplish either goal.
Xert: The Freedom to Ride – any which way you want. 
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