Negotiate Alliance

is_available = trigger_if = {
	limit = {
		is_ai = yes
	}
	is_at_war = no
}
is_shown = scope:puppet_or_actor ?= {
	OR = {
		highest_held_title_tier >= 2
		scope:actor = {
			is_ai = no
		}
	}
	is_ruler = yes
	OR = {
		is_any_family_relation_or_spouse_trigger = {
			CHARACTER = scope:recipient
		}
		hostage_oath_of_friendship_trigger = yes
		has_opinion_modifier = {
			modifier = blood_brother_close_family_opinion
			target = scope:recipient
		}
		house ?= {
			house_head ?= scope:puppet_or_actor
			any_house_relation = {
				any_relation_house = {
					exists = house_head
					scope:recipient = house_head
				}
				has_house_relation_parameter = unlocks_house_head_negotiate_alliance
			}
		}
	}
}
scope:recipient = {
	this != scope:puppet_or_actor
	NOT = {
		is_allied_to = scope:puppet_or_actor
	}
	is_ruler = yes
}

As written in game/common/character_interactions/00_alliance.txt.

scope:recipient = {
	is_playable_character = yes
	is_imprisoned = no
	highest_held_title_tier < tier_hegemony
}
scope:puppet_or_actor ?= {
	is_playable_character = yes
	is_imprisoned = no
	NOT = {
		is_at_war_with = scope:recipient
	}
	highest_held_title_tier < tier_hegemony
	OR = {
		has_perk = defensive_negotiations_perk
		is_spouse_of = scope:recipient
		is_parent_of = scope:recipient
		is_grandparent_of = scope:recipient
		is_great_grandparent_of = scope:recipient
		is_child_of = scope:recipient
		is_grandchild_of = scope:recipient
		is_great_grandchild_of = scope:recipient
		is_uncle_or_aunt_of = scope:recipient
		is_nibling_of = scope:recipient
		is_sibling_of = scope:recipient
		has_opinion_modifier = {
			modifier = blood_brother_close_family_opinion
			target = scope:recipient
		}
		custom_description = {
			text = rulers_family_is_married_to_other_ruler_trigger
			subject = scope:recipient
			object = scope:puppet_or_actor
			scope:recipient = {
				any_spouse = {
					OR = {
						is_close_family_of = scope:puppet_or_actor
						is_nibling_of = scope:puppet_or_actor
						is_uncle_or_aunt_of = scope:puppet_or_actor
					}
				}
			}
		}
		custom_description = {
			text = rulers_family_is_married_to_other_ruler_trigger
			subject = scope:puppet_or_actor
			object = scope:recipient
			any_spouse = {
				OR = {
					is_close_family_of = scope:recipient
					is_nibling_of = scope:recipient
					is_uncle_or_aunt_of = scope:recipient
				}
			}
		}
		custom_description = {
			text = rulers_child_parent_sibling_is_married_to_other_rulers_trigger
			subject = scope:recipient
			object = scope:puppet_or_actor
			any_close_family_member = {
				OR = {
					is_parent_of = scope:puppet_or_actor
					is_child_of = scope:puppet_or_actor
					is_sibling_of = scope:puppet_or_actor
				}
				any_spouse = {
					OR = {
						is_parent_of = scope:recipient
						is_child_of = scope:recipient
						is_sibling_of = scope:recipient
					}
				}
			}
		}
		custom_description = {
			text = hostage_oath_of_friendship_trigger
			subject = scope:recipient
			object = scope:puppet_or_actor
			hostage_oath_of_friendship_trigger = yes
		}
		custom_tooltip = {
			text = house_relation_alliance_trigger
			house ?= {
				house_head ?= scope:puppet_or_actor
				any_house_relation = {
					any_relation_house = {
						exists = house_head
						scope:recipient = house_head
					}
					has_house_relation_parameter = unlocks_house_head_negotiate_alliance
				}
			}
		}
	}
}
custom_description = {
	text = has_already_rejected_renegotiation
	subject = scope:recipient
	NOT = {
		scope:puppet_or_actor = {
			has_opinion_modifier = {
				modifier = refused_alliance_opinion
				target = scope:recipient
			}
		}
	}
}

As written in game/common/character_interactions/00_alliance.txt.

on_accept = scope:puppet_or_actor = {
	trigger_event = char_interaction.0235
	stress_and_fulfillment_impact = {
		shy = minor_stress_impact_gain
	}
	if = {
		limit = {
			scope:hook = yes
			has_usable_hook = scope:recipient
		}
		use_hook = scope:recipient
	}
	if = {
		limit = {
			scope:influence = yes
		}
		change_influence = major_influence_loss
	}
}
scope:recipient = {
	custom_tooltip = negotiate_alliance_effect_recipient_tooltip
}
hidden_effect = {
	if = {
		limit = {
			scope:puppet_or_actor = {
				OR = {
					is_spouse_of = scope:recipient
					is_child_of = scope:recipient
					is_parent_of = scope:recipient
					is_sibling_of = scope:recipient
					is_grandparent_of = scope:recipient
					is_great_grandparent_of = scope:recipient
					is_grandchild_of = scope:recipient
					is_great_grandchild_of = scope:recipient
					is_uncle_or_aunt_of = scope:recipient
					is_nibling_of = scope:recipient
				}
			}
		}
		scope:puppet_or_actor = {
			create_alliance = {
				target = scope:recipient
				allied_through_owner = scope:puppet_or_actor
				allied_through_target = scope:recipient
			}
		}
	}
	else_if = {
		limit = {
			scope:recipient = {
				any_spouse = {
					OR = {
						is_close_family_of = scope:puppet_or_actor
						is_nibling_of = scope:puppet_or_actor
						is_uncle_or_aunt_of = scope:puppet_or_actor
					}
				}
			}
		}
		scope:recipient = {
			random_spouse = {
				limit = {
					OR = {
						is_close_family_of = scope:puppet_or_actor
						is_nibling_of = scope:puppet_or_actor
						is_uncle_or_aunt_of = scope:puppet_or_actor
					}
				}
				save_scope_as = recipient_spouse
			}
		}
		scope:puppet_or_actor = {
			create_alliance = {
				target = scope:recipient
				allied_through_owner = scope:recipient_spouse
				allied_through_target = scope:recipient
			}
		}
	}
	else_if = {
		limit = {
			scope:puppet_or_actor = {
				any_spouse = {
					OR = {
						is_close_family_of = scope:recipient
						is_nibling_of = scope:recipient
						is_uncle_or_aunt_of = scope:recipient
					}
				}
			}
		}
		scope:puppet_or_actor = {
			random_spouse = {
				limit = {
					OR = {
						is_close_family_of = scope:recipient
						is_nibling_of = scope:recipient
						is_uncle_or_aunt_of = scope:recipient
					}
				}
				save_scope_as = actor_spouse
			}
		}
		scope:puppet_or_actor = {
			create_alliance = {
				target = scope:recipient
				allied_through_owner = scope:puppet_or_actor
				allied_through_target = scope:actor_spouse
			}
		}
	}
	else_if = {
		limit = {
			scope:puppet_or_actor = {
				any_close_family_member = {
					OR = {
						is_child_of = scope:puppet_or_actor
						is_parent_of = scope:puppet_or_actor
						is_sibling_of = scope:puppet_or_actor
					}
					any_spouse = {
						OR = {
							is_child_of = scope:recipient
							is_parent_of = scope:recipient
							is_sibling_of = scope:recipient
						}
					}
				}
			}
		}
		scope:puppet_or_actor = {
			random_close_family_member = {
				limit = {
					OR = {
						is_child_of = scope:puppet_or_actor
						is_parent_of = scope:puppet_or_actor
						is_sibling_of = scope:puppet_or_actor
					}
					any_spouse = {
						OR = {
							is_child_of = scope:recipient
							is_parent_of = scope:recipient
							is_sibling_of = scope:recipient
						}
					}
				}
				save_scope_as = actor_spouse
				random_spouse = {
					limit = {
						OR = {
							is_child_of = scope:recipient
							is_parent_of = scope:recipient
							is_sibling_of = scope:recipient
						}
					}
					save_scope_as = recipient_spouse
				}
			}
		}
		scope:puppet_or_actor = {
			create_alliance = {
				target = scope:recipient
				allied_through_owner = scope:actor_spouse
				allied_through_target = scope:recipient_spouse
			}
		}
	}
	else_if = {
		limit = {
			scope:puppet_or_actor = {
				has_perk = defensive_negotiations_perk
			}
		}
		scope:puppet_or_actor = {
			create_alliance = {
				target = scope:recipient
				allied_through_owner = scope:puppet_or_actor
				allied_through_target = scope:recipient
			}
		}
		scope:recipient = {
			add_opinion = {
				modifier = perk_negotiated_alliance_opinion
				target = scope:puppet_or_actor
			}
		}
	}
	else_if = {
		limit = {
			scope:puppet_or_actor = {
				hostage_oath_of_friendship_trigger = yes
			}
		}
		scope:puppet_or_actor = {
			create_alliance = {
				target = scope:recipient
				allied_through_owner = scope:puppet_or_actor
				allied_through_target = scope:recipient
			}
		}
	}
}
add_clan_unity_interaction_effect = {
	CHARACTER = scope:puppet_or_actor
	TARGET = scope:recipient
	VALUE = minor_unity_gain
	DESC = clan_unity_alliance.desc
	REVERSE_NON_HOUSE_TARGET = no
}
on_decline = scope:puppet_or_actor = {
	trigger_event = char_interaction.0236
}
scope:puppet_or_actor = {
	add_opinion = {
		modifier = refused_alliance_opinion
		target = scope:recipient
	}
}
add_clan_unity_interaction_effect = {
	CHARACTER = scope:puppet_or_actor
	TARGET = scope:recipient
	VALUE = minor_unity_loss
	DESC = clan_unity_all
# … (cut here; the rest is in the file)

As written in game/common/character_interactions/00_alliance.txt.