pretender event - no casus beli

[Lithuanian2]

Playing as Lithuania I got a Polish pretender event. There were two options: send him away or help him fight for Polish throne. Naturally I chose the latter, however I was surprised because I received -3 stability hit. -1 because of same faith and -2 because no casus belli. However pretender = clear casus, no?

 

[ConjurerDragon]

Playing as Lithuania I got a Polish pretender event. There were two options: send him away or help him fight for Polish throne. Naturally I chose the latter, however I was surprised because I received -3 stability hit. -1 because of same faith and -2 because no casus belli. However pretender = clear casus, no?

If you report a bug in this forum you should first state what game you were playing. FtG vanilla? FtG AGCEEP or some other mod?

If AGCEEP you probably mean this random event:

event = {
   id = 96009112
   trigger = {
       NOT = { owned = { province = 1614 data = -1 } } #not for the Pope (MUS)
       ai = no
       stability = -2
       NOT = { year = 1789 }
       NOT = { religion = pagan }
   }
   random = yes
   name = "EVENTNAME_RANDOM112" #Pretender to the Throne
   desc = "EVENTHIST_RANDOM112"
   #-#After a domestic conflict the defeated leaders would try to gain support from neighbouring countries. Usually they would end up wandering across the countryside leaving a trail of unpaid bills behind them, but sometimes a country with an axe to grind against their homeland would support their claims.

   action_a = {
       name = "ACTIONNAME_RANDOM112A" #Send him away
       command = { type = relation which = -1 value = 10 }
   }
   action_b = {
       name = "ACTIONNAME_RANDOM112B" #Support his claim
       command = { type = war which = -3 }
       command = { type = badboy value = -2 }
       command = { type = relation which = -3 value = -35 }
       command = { type = treasury value = -150 }
       command = { type = INF which = -2 value = 5000 }
       command = { type = CAV which = -2 value = 2000 }
   }
}

If you gain a casus belli in an event then that will be clearly shown ingame if you hover the cursor over the option. In this event you gain no CB and the WAR command causes you to suffer the same penalties as if you would have declared war yourself, e.g. for breaking a royal marriage, breaking an alliance, breaking a truce, declaring without CB...
https://forum.paradoxplaza.com/forum/index.php?threads/diplomacy-faq-v1-08.172908/