Grant Vassal

is_shown = scope:recipient != scope:puppet_or_actor
OR = {
	AND = {
		exists = scope:recipient.liege
		scope:recipient.liege ?= scope:puppet_or_actor
	}
	AND = {
		exists = scope:puppet_or_actor.liege
		scope:puppet_or_actor.liege ?= scope:recipient
	}
	AND = {
		scope:puppet_or_actor.faith.religious_head ?= scope:recipient
		scope:recipient = {
			top_liege = this
		}
	}
}
scope:recipient.highest_held_title_tier > tier_barony

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

scope:recipient = {
	is_landed = yes
	NOT = {
		has_trait = gallivanter
	}
}
NOT = {
	scope:puppet_or_actor = {
		is_at_war_with = scope:recipient
	}
}
trigger_if = {
	limit = {
		exists = scope:secondary_actor
	}
	NOT = {
		scope:secondary_actor = {
			is_at_war_with = scope:recipient
		}
	}
	scope:recipient.primary_title.tier > scope:secondary_actor.primary_title.tier
}
trigger_if = {
	limit = {
		scope:puppet_or_actor = {
			is_ai = yes
		}
		exists = scope:secondary_actor
	}
	trigger_if = {
		limit = {
			NOT = {
				scope:recipient.primary_title = {
					any_in_de_jure_hierarchy = {
						holder = scope:secondary_actor
					}
				}
			}
		}
		scope:recipient.vassal_count < scope:recipient.vassal_limit
	}
	scope:secondary_actor = {
		NOT = {
			has_character_flag = ai_should_not_transfer
		}
	}
}
trigger_if = {
	limit = {
		scope:recipient.highest_held_title_tier <= tier_county
	}
	scope:recipient = {
		highest_held_title_tier > tier_county
	}
}
trigger_else = {
	scope:puppet_or_actor = {
		custom_description = {
			text = basic_valid_vassal_to_tranfer
			object = scope:recipient
			any_vassal = {
				NOT = {
					highest_held_title_tier = tier_barony
				}
				scope:recipient.highest_held_title_tier > highest_held_title_tier
			}
		}
	}
}
NAND = {
	scope:puppet_or_actor ?= {
		is_ai = yes
		government_has_mechanic = administrative
	}
	scope:recipient ?= {
		NOT = {
			government_has_mechanic = administrative
		}
	}
	scope:secondary_actor ?= {
		government_has_mechanic = administrative
	}
}
custom_tooltip = {
	text = ritsuryo_to_soryo_invalid_to_transfer
	NAND = {
		scope:puppet_or_actor ?= {
			has_government = japan_administrative_government
		}
		scope:recipient ?= {
			has_government = japan_administrative_government
		}
		scope:secondary_actor ?= {
			has_government = japan_feudal_government
		}
	}
}
custom_tooltip = {
	text = cannot_transfer_bloc_leader_as_vassal_tt
	NOT = {
		scope:secondary_actor ?= {
			exists = house.house_confederation.leading_house
			house.house_confederation.leading_house ?= house
			is_house_head = yes
		}
	}
}

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

on_accept = if = {
	limit = {
		scope:puppet_or_actor = {
			any_patroned_holy_order = {
				leader.capital_county.holder ?= {
					target_is_same_character_or_above = scope:secondary_actor
				}
			}
		}
		scope:recipient = {
			highest_held_title_tier >= tier_duchy
		}
	}
	scope:puppet_or_actor = {
		custom_tooltip = holy_order_control_loss_warning_tt
	}
}
scope:puppet_or_actor = {
	send_interface_toast = {
		type = event_toast_effect_good
		title = grant_vassal_interaction_notification
		right_icon = scope:recipient
		left_icon = scope:secondary_actor
		if = {
			limit = {
				scope:puppet_or_actor = {
					is_vassal_of = scope:recipient
				}
			}
			add_truce_both_ways = {
				character = scope:secondary_actor
				days = 3650
				name = TRUCE_GRANT_INDEPENDENCE
			}
		}
		create_title_and_vassal_change = {
			type = granted
			save_scope_as = change
			add_claim_on_loss = no
		}
		scope:secondary_actor = {
			change_liege = {
				liege = scope:recipient
				change = scope:change
			}
		}
		resolve_title_and_vassal_change = scope:change
		scope:recipient = {
			add_opinion = {
				target = scope:puppet_or_actor
				modifier = granted_vassal
			}
		}
	}
}
add_clan_unity_interaction_effect = {
	CHARACTER = scope:puppet_or_actor
	TARGET = scope:recipient
	VALUE = miniscule_unity_gain
	DESC = clan_unity_grant_vassal.desc
	REVERSE_NON_HOUSE_TARGET = yes
}
hidden_effect = {
	if = {
		limit = {
			fp3_struggle_involves_one_supporter_and_one_detractor = {
				FIRST = scope:puppet_or_actor
				SECOND = scope:recipient
			}
			scope:puppet_or_actor = {
				any_character_struggle = {
					involvement = involved
					phase_has_catalyst = catalyst_grants_vassal_to_de_jure_liege_supporter_detractor
					is_secondary_character_involvement_involved_trigger = {
						CHAR = scope:recipient
					}
				}
			}
			scope:recipient.primary_title = {
				any_this_title_or_de_jure_above = {
					holder = scope:secondary_actor
				}
			}
		}
		scope:puppet_or_actor = {
			every_character_struggle = {
				involvement = involved
				activate_struggle_catalyst = {
					catalyst = catalyst_grants_vassal_to_de_jure_liege_supporter_detractor
					character = scope:puppet_or_actor
				}
				log_debug_variable_for_persian_struggle_effect = {
					VAR = concession_catalyst_grants_vassal_to_de_jure_liege_supporter_detractor
				}
			}
		}
	}
	if = {
		limit = {
			scope:recipient = {
				government_has_flag = government_is_nomadic
			}
		}
		while = {
			limit = {
				scope:secondary_actor ?= {
					any_held_title = {
						vassal_grant_de_jure_shift_trigger = yes
					}
				}
			}
			scope:secondary_actor ?= {
				random_held_title = {
					limit = {
						vassal_grant_de_jure_shift_trigger = yes
					}
					set_de_jure_liege_title = scope:recipient.primary_title
				}
			}
		}
	}
}
if = {
	limit = {
		scope:puppet_or_actor = {
			is_ai = no
		}
	}
	scope:secondary_actor = {
		if = {
			limit = {
				any_held_title = {
					any_claimant = {
						this = scope:recipient
					}
				}
			}
			ordered_held_title = {
				order_by = tier
				limit = {
					any_claimant = {
						this = scope:recipient
					}
				}
				save_scope_as = highest_claim
			}
			scope:recipient = {
				claimant_jealousy_immunity_effect = yes
			}
		}
		every_held_title = {
			limit = {
				tier >= tier_county
				tier = scope:secondary_actor.primary_title.tier
			}
			save_scope_as = title_transfered
			scope:puppet_or_actor = {
				title_granting_controversy_effect = {
					TITLE = scope:title_transfered
					INTERACTION = grant_vassal_interaction
				}
			}
		}
		every_in_list = {
			list = strong_claimants
			limit = {
				NOT = {
					this = scope:recipient
				}
			}
			save_scope_as = claimer
			scope:secondary_actor = {
				ordered_held_title = {
					limit = {
						any_claimant = {
							this = scope:claimer
						}
					}
					save_scope_as = highest_denied_claim
				}
			}
			claimant_rivalry_mercy_effect = yes
		}
	}
	if = {
		limit = {
			NOT = {
				scope:secondary_actor = {
					any_held_title = {
						any_this_title_or_de_jure_above = {
							holder ?= scope:recipient
						}
					}
				}
			}
		}
		scope:secondary_actor = {
			add_opinion = {
				modifier = subordinated_to_non_de_jure_liege_opinion
				target = scope:puppet_or_actor
				opinion = -30
			}
		}
	}
}
on_decline = scope:puppet_or_actor = {
	trigger_event = char_interaction.0211
}
add_clan_unity_interaction_effect = {
	CHARACTER = scope:recipient
	TARGET = scope:puppet_or_actor
	VALUE = miniscule_unity_loss
	DESC = clan_unity_grant_vassal_decline.desc
	REVERSE_NON_HOUSE_TARGET = no
}

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