I've been experimenting with this module on a local dev site. My setup is a mostly fresh Drupal 11 site with rc4 of this module.
I have a single-valued entity reference field and have configured it to use the "Default prompt for a single target reference" prompt. When I click to "Generate references with AI", I almost always get multiple options. Here's an example:

Looking at the default prompt, it is pretty clear that only 1 should be returned:
For the contents within the code block:
{contents}
Which one of the following | separated options are highly relevant and moderately relevant?
{possible_results}
Return a single selection from within the square brackets only and as a valid RFC8259 compliant JSON array within one array key highly without deviation.
Example:
{
"highly": [
"Your suggestion here"
]
}
Something odd is happening here...
-mike
Comments
Comment #2
scott_euser commentedThanks for reporting! I will try to take a look asap. I reckon the structured json it's requesting is probably better to also force single.
There is also by the way recently a FWA integration. You can turn off the generate button via the auto reference advanced settings within the content type and use the manage form display cog for several field types if you prefer the modal window route. I need to update the homepage with that once I've been through more rounds of testing in real world scenarios with it. Personally i find it a nicer UX.
Comment #4
scott_euser commentedOkay I've changed it to be radio buttons when the cardinality of the target field is 1; that should take care of it :)
Comment #5
ultimike@scott_euser -
Thanks for the quick response. I just manually tested the MR and I am still getting multiple results when using the `auto_reference__default_single` prompt. I'm not seeing radio buttons in the results (I assume you're talking about radio buttons in the results in the status message, right?)
But, I also checked out the Field Widget Action and that appears to be working as you described, including the radio buttons. I'm not crazy about the name, "Suggest from existing terms (Form)", as this can be used for things other than terms (my example is for related nodes) and the "(Form)" bit seems superfluous, but otherwise it is working as I expect (and I actually prefer using this as a FWA instead of the /admin/structure/types/manage/book_chapter/ai-autoreference configuration.
When using the FWA, are you sensing single vs. multiple by the cardinality of the field? I think that's the way to go. In fact, if you are comfortable with it, I'd remove the non-FWA method altogether.
thanks,
-mike
Comment #6
ultimikeAlso - I think you need to add a dependency on Field Widget Actions module.
-mike
Comment #7
scott_euser commentedYeah if we ultimately removing the original method then we could do a dependency - it is quite a bit nicer, open to opinions on that. Personally I'll never use the old method again :)
Still ill try to sort the radios within the message for the time being in case that feature stays. Maybe it's not detecting the target field cardinality.
Yeah good point on the form modal title - not sure if there is a generic enough term (eg Suggest relationships) or worth making it per field configurable.
Comment #8
ultimikeYeah, I'm the same. FWA is the way to go. I'm including this module in an AI course I'm writing and I marked the FWA method as "recommended".
Personally, I'd rip the band-aid off ASAP and get rid of the non-FWA method before a 1.0.0 release. Maybe write an update hook to convert everyone's configuration. Easier now than later...
Also - for the action name, why not, "Generate references with AI" - same thing as the button label in the non-FWA method?
-mike
Comment #9
scott_euser commentedSure that sounds good re the title
Only thing re the FWA route is that relies on ajax commands for each field widget rather than field type (eg currently have a MR open for checkboxes list/radios https://git.drupalcode.org/project/field_widget_actions/-/work_items/357...
Could be more fields too. I have tried the big Drupal CMS ones like Tagify though at least. The entity reference 'Add another' field widget is particularly problematic. What happens is the Insert button in the modal does nothing if the widget isn't something it recognises.
I suppose worst case scenario then people have to change to a different better supported widget and I could maintain a list on the module homepage.
I do definitely agree easier to support just one route and since it's not stable I suppose the handful of installs can't really complain (and I know I'm a few of the installs, using the underlying services programmatically without the UI at all, eg in migrate api scripts).
... All that said I think I'm convinced but I'll sleep on it first :)
Comment #11
scott_euser commentedI'll move a few things into follow-ups, thanks for the back and forth! I merged the progress on this + added some warnings on the edit form of the indiividual auto references where you choose the prompt that warn about choosing e.g. single for a cardinality multiple or vice versa