Hey , first to mention that I'm Taiwanese whose mother language is Chinese , Maybe will encounter some misuse of English words through communication.

I have checked your file in DepartmentOfForeignAffairs+Constructibles[Exchanges] , you copy the CityDeal option and remove the prerequisite

<DiplomaticContractContainsTermPrerequisite Flags="Prerequisite,Discard">WarToTruce</DiplomaticContractContainsTermPrerequisite>

then it works. I wonder how.

I wonder that its a Extension mod , it shouldn't remove the Prerequisite in the original files. As you say you add a new option , but I found CityDeal option in the original one. If its new , it should be called other name.

So I think , maybe you just add a null Prerequisite to the original CityDeal option , then throught it the option will show in the Diplomacy screen.

Then I want farther , I want to exchange stockpile , resource and technology in ColdWar. Because its Extension , so I just delete the Prerequisite

<DiplomaticContractContainsTermPrerequisite>
<DiplomaticRelationStatePrerequisite>

terms below the BoosterDeal , ResourceDeal , TechnologyDeal just leave the DiplomaticCustomCost like CityDeal , wish to add a null prerequisite. But it didn't work.

Then I try another way. Add a New Prerequisite in <DiplomaticRelationStatePrerequisite> .

It already have

<DiplomaticRelationStatePrerequisite>DiplomaticRelationStatePeace</DiplomaticRelationStatePrerequisite>

<DiplomaticRelationStatePrerequisite>DiplomaticRelationStateAlliance</DiplomaticRelationStatePrerequisite>

I add one term

<DiplomaticRelationStatePrerequisite>DiplomaticRelationStateColdWar</DiplomaticRelationStatePrerequisite>

If its an add on , it should works. But it didn't.

Finally I have no choice , just add the new Prequisite

<DiplomaticRelationStatePrerequisite>DiplomaticRelationStateColdWar</DiplomaticRelationStatePrerequisite>

below the three option and change to Conversion. Then it works.

I just can't understand the logic in Extension. Will it overwrite the same option? Or it will add new option with No Prequisute?(But seems not work in Other Deal) Or it will add a null Prerequisite in same option?

If my logic is right , when I add a ColdWar prerequisite in three options then let Extension to add on , It should be same with Coversion . It should work... But its just not...

I want it to stay in Extension to be Compatibility Friendly, can you help me?

I'm considering an advenced option , but this one first.

Okay , I have done the Test. Seems it will just overwrite the original files when you named the same option... so you are not create the new one or add new content to the same option... Its same with Conversion. But in conversion you need all files , Extension just overwrite part of it...

seems so?

@WayneNore Hello! Sorry for the late response, I was very busy before, didn't check my Steam much.

I am not sure about type of my mod anyway, someone in comments sent me message saying that my mod should be labeled Extension, so I changed it. I believe that it's wrong type, for the reasons you mentioned above, but my mod is too small, so I don't want to conflict with bigger and more interesting Conversion/Standalone mods. I should probably mention it in the description.

Did you tried Standalone type instead of Conversion type for your mod? I just checked manual and I don't know what's the real difference here.

About your example - yep, logic is clunky. It's hard to tell from your example without trying it for myself.

I added you on Steam, I believe it would be much easier to communicate.