What is the default Adoption game rule in CK3?

Default: Adoption is unlocked by the Compassionate Trait, certain Cultural Traditions, being infertile and childless, or being in a same-sex marriage. (patch 1.20.1.2)

Does changing the Adoption rule disable achievements?

Yes for “Always Allowed”: the file gives it the flag blocks_achievements. The other settings keep achievements on.

Game rule · Game Modes

Adoption

Forbidden
Default
Always Allowed ✕

Adoption is a game rule in Crusader Kings III (Game Modes) with 3 settings: Forbidden, Default (the default) and Always Allowed. “Always Allowed” disables achievements. Patch 1.20.1.2, from game/common/game_rules/00_game_rules.txt.

This section as JSON: /raw/game-rules.json

Quick answers (2)

What is the default Adoption game rule in CK3?: Default: Adoption is unlocked by the Compassionate Trait, certain Cultural Traditions, being infertile and childless, or being in a same-sex marriage. (patch 1.20.1.2)
Does changing the Adoption rule disable achievements?: Yes for “Always Allowed”: the file gives it the flag blocks_achievements. The other settings keep achievements on.

3 settings

Forbidden
The Adoption Interaction will be disabled under all circumstances.
The script checks it 5 times, in 5 places
Events 2
- A Child of the Court
- …, a Breakthrough
Cultural traditions 2
- Noble Adoption
- Dynastic Pragmatism
Character interactions 1
- Adopt
Every has_game_rule = no_adoption in game/common and game/events, by the top-level object it sits in.
no_adoption
Default
Default
Adoption is unlocked by the Compassionate Trait, certain Cultural Traditions, being infertile and childless, or being in a same-sex marriage.
default_adoption
Always Allowed
Disables achievements
The Adoption Interaction will be available to all characters as long as they are unmarried or the dominant partner in their marriage.
The script checks it 11 times, in 4 places
Character interactions 3
Scripted effects 1
- adopt_effect
Every has_game_rule = adoption_always_allowed in game/common and game/events, by the top-level object it sits in.
adoption_always_allowed

Source: game/common/game_rules/00_game_rules.txt line 356 (key adoption), modifiers from game/common/modifiers, names from the English localisation; Crusader Kings III 1.20.1.2.