GameRule Codec and Serialization

GameRule Codec & Serialization

Topic	Specification
Serialization Failure	SavedDataStorage.encodeUnchecked crash during world save
Fix Release	1.8.15
Integer Bounds	min = Integer.MIN_VALUE (or Math.min(Integer.MIN_VALUE, defaultValue))

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🛠️ The Integer GameRule Codec Fix

In Minecraft 26.2, dynamic GameRules are serialized into level.dat / game_rules.dat via SavedDataStorage.encodeUnchecked. In earlier library versions, integer GameRules registered without explicit minimum bounds caused the GameRule codec to enforce strict positive bounds (min = 0), throwing an IllegalStateException when serializing negative integer values or default thresholds.

The Fix in DynamicGameRuleManager

// IntegerBuilder initialization fix in DynamicGameRuleManager
public class IntegerBuilder {
    private int min = Integer.MIN_VALUE;
    private int max = Integer.MAX_VALUE;

    public GameRule<Integer> register() {
        int effectiveMin = Math.min(min, defaultValue);
        int effectiveMax = Math.max(max, defaultValue);
        // Uses Codec.INT.intRange(effectiveMin, effectiveMax) to prevent encodeUnchecked bounds check failure
        GameRule<Integer> rule = new GameRule<>(
            GameRuleType.INT, defaultValue, Codec.INT.intRange(effectiveMin, effectiveMax), 
            FeatureFlagSet.of(), category, visitor
        );
        return Registry.register(BuiltInRegistries.GAME_RULE, Identifier.parse(ruleName), rule);
    }
}

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🔒 NBT Namespace Safety

Always namespace dynamic GameRules with modid:rule_name ([ERR-20260510-002]). Unnamespaced dynamic GameRules fail to serialize cleanly into vanilla level saved data, causing silent data loss upon server restart.

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🔗 Related Pages

• Dynamic GameRules Manager
• Client GameRule & GUI Helpers