Greetings.

I've just got my hands on Humankind and so far I'm having a blast. Awesome game!

Nevertheless, I've just reached the Industrial era and there is something that is not working as I expected: my opponent choose the Spanish culture, which gives them the Expansionist trait. This in turn gives them the Ambition affinity bonus, which allows them to freely cross frontiers with their units, even when in a Closed Borders treaty.

Now I have rival units all around my cities, and I can do nothing about it. Also, according to the Wiki entry (https://humankind.fandom.com/wiki/Expansionist), the "Trespassing" grievances should be activating, but they are not (they activated in the past when some territories changed hands, and I could ask for some money in compensation then, but now I cannot even demand this).

Any idea why my rival can roam freely within my empire without triggering Trespassing grievances which I can leverage on the diplomacy screen?

Thanks

Thanks for the anwer! 

I'l try to cover your points, as I'm pretty sure they don't apply to this case:

glenjen75 wrote:

1) Is Spain now the vassal of another player that you have an Open Border treaty with? The treaty would then apply to them as well.

No, its a 1 on 1 on a Tiny map. There are no more empires in the game besides the two of us, and all Independent People are long gone at this point (Industrial era)

2) Are they actually mercenaries from an Independent People that was made a client state of Spain? They would likely have the Spanish player's symbol, but unless hired by Spain would not actually be Spanish troops. It can sometimes be difficult to distinguish between roaming mercenaries and owned troops until you seem them side by side.

As there are no Independent people left, (and they were gone ages ago, literally) I'm pretty sure they can't be mercs.

3) Have they been in your territory so long that the grievance has long since been resolved? AFAIK the grievance would only trigger when they crossed into your territory (or as you said, when territory changed hands). It's a one-time trigger for the grievance rather than an ongoing one - unless maybe the troops are crossing back and forth across the border. If Spain were not Expansionist, the health penalty (but not the grievance) for trespassing *would* be ongoing. 

No. We have been for quite some time now on a status quo, without angering each other. They crossed borders the following turn of becoming Spanish culture. I was monitoring most borders, so I actually saw most units (if not all) actually crossing them (to my surprise, as I dind't know about the spanish Ambition trait by then)

Well, I'm a bit stumped. 

For completeness sake, I'm assuming we aren't talking about diplomat units or outpost territories (dashed border).

If no one else offers a good explanation, feel free to submit to the Bug Report thread (there are instructions there about what files to include). The recent expansion overhauled the stealth system so I imagine there was some tinkering in the Tresspassing triggers.

Yes, they were regular military units ofc, not diplomats.

I've already finished that game anyway. Eventually the AI got bored and retreted to their territories (guess once it mapped the whole map). I still have some saves and will report the error if I find the issue again in the new game I'm starting now.