PK9 and PA9 Classes

Generation 9 introduces the latest Pokémon data formats: PK9 for Scarlet/Violet and PA9 for Z-A (Legends Z-A).

PK9 Class

Namespace: PKHeX.Core File: PKHeX.Core/PKM/PK9.cs

Format Specifications

Property	Value
SIZE_STORED	328 bytes (0x148)
SIZE_PARTY	344 bytes (0x158)
Generation	9
Context	EntityContext.Gen9
Games	Scarlet, Violet

Key Features

Terastallization

Gen 9’s main battle mechanic:

public byte TeraTypeOriginal { get; set; }
public byte TeraTypeOverride { get; set; }

TeraTypeOriginal: Natural Tera Type (based on species)
TeraTypeOverride: Changed Tera Type (0x19 = no override)

Obedience Level

public byte ObedienceLevel { get; set; }

Tracks the level at which the Pokémon will obey, based on badges.

Scale System

public byte Scale { get; set; }
public byte HeightScalar { get; set; }
public byte WeightScalar { get; set; }

Expanded size variation system from PLA.

Data Structure

Same block structure as PK8:

4 blocks of 80 bytes each
8-byte header
Total: 328 bytes stored, 344 party

Important Properties

Tech Records Continued

public bool GetMoveRecordFlag(int index) { get; set; }

Gen 9 continues using the Tech Record system.

Battle Version

public byte BattleVersion { get; set; }

Tracks which game version the Pokémon last battled in.

HOME Tracker

public ulong Tracker { get; set; }

Unique identifier for Pokémon HOME.

Tera Type System

public MoveType TeraType
{
    get
    {
        var val = TeraTypeOverride;
        if (val != 19) // 19 = no override
            return (MoveType)val;
        return (MoveType)TeraTypeOriginal;
    }
}

The effective Tera Type is the override if set, otherwise the original.

Relearn Move Management

public void FixRelearn()
{
    // Compresses relearn moves to remove gaps
    // If move 4 exists but move 3 is empty, shifts down
}

Ensures relearn moves are properly ordered without gaps.

PA9 Class

Namespace: PKHeX.Core File: PKHeX.Core/PKM/PA9.cs

Format Specifications

Property	Value
SIZE_STORED	328 bytes (0x148)
SIZE_PARTY	344 bytes (0x158)
Generation	9
Context	EntityContext.Gen9a
Games	Legends: Z-A

Key Features

Alpha Pokémon (Returning)

public bool IsAlpha { get; set; }

Alpha Pokémon return from Legends: Arceus.

Plus Records

New learning system:

public interface IPlusRecord
{
    bool GetPlusRecordFlag(int index) { get; set; }
}

Extended version of Tech Records for Z-A.

Data Structure

Same size as PK9 but with different internal structure:

Modified block layout for Alpha support
Plus Record flags replace some PK9 features
Different PersonalInfo table (PersonalTable.ZA)

Differences from PK9

Added Features

Alpha Pokémon
Plus Records system
Possibly modified battle mechanics

Removed Features

Terastallization (may not be in Z-A)
Some SV-specific marks/ribbons

Modified Features

Uses PersonalInfo9ZA instead of PersonalInfo9SV
Different move pools and availability

Comparison Table

Feature	PK9	PA9
Size (Stored)	328 bytes	328 bytes
Size (Party)	344 bytes	344 bytes
Block Size	80 bytes	80 bytes
Terastallization	Yes	No
Alpha	No	Yes
Plus Records	No	Yes
Tech Records	Yes	Yes
Scale System	Yes	Yes
Obedience Level	Yes	Yes
Contest Stats	No	Yes

Code Examples

Creating a PK9 with Tera Type

var pk9 = new PK9
{
    Species = 908, // Meowscarada
    Form = 0,
    CurrentLevel = 50,
    TeraTypeOriginal = (byte)MoveType.Grass,
    TeraTypeOverride = (byte)MoveType.Dark, // Changed Tera Type
    ObedienceLevel = 50,
    Ball = 1, // Poke Ball
};
pk9.SetRandomIVs(6);
pk9.RefreshChecksum();

Checking Tera Type

var pk9 = new PK9(data);

if (pk9.TeraTypeOverride != 19)
{
    Console.WriteLine($"Tera Type changed to: {(MoveType)pk9.TeraTypeOverride}");
}
else
{
    Console.WriteLine($"Original Tera Type: {(MoveType)pk9.TeraTypeOriginal}");
}

Creating an Alpha PA9

var pa9 = new PA9
{
    Species = 901, // Ursaluna (Blood Moon?)
    CurrentLevel = 70,
    IsAlpha = true,
    HeightScalar = 255,
    WeightScalar = 255,
};
pa9.SetRandomIVs(6);
pa9.RefreshChecksum();

Setting Scale Values

var pk9 = new PK9
{
    Species = 25, // Pikachu
    Scale = 128,      // Average scale
    HeightScalar = 150,
    WeightScalar = 100,
};

Fixing Relearn Moves

var pk9 = new PK9(data);

// Before: [Move1, 0, 0, Move4]
pk9.FixRelearn();
// After:  [Move1, Move4, 0, 0]

Handler Update System

public void UpdateHandler(ITrainerInfo tr)
{
    if (IsEgg)
    {
        // Eggs get link trade data if traded
        const ushort location = Locations.LinkTrade6;
        if (MetLocation != location && !BelongsTo(tr))
        {
            var date = EncounterDate.GetDateSwitch();
            SetLinkTradeEgg(date.Day, date.Month, date.Year, location);
        }
        return;
    }

    // Update handler if OT doesn't match
    if (!TradeOT(tr))
        TradeHT(tr);
}

New Gen 9 Features

Unhatched Eggs

public bool IsUnhatchedEgg => Version == 0 && IsEgg;

Eggs that haven’t been given a version yet.

Enhanced Shiny Calculation

public override uint PSV => ((PID >> 16) ^ (PID & 0xFFFF)) >> 4;
public override uint TSV => (uint)(TID16 ^ SID16) >> 4;

Gen 9 uses 4-bit shift (1/4096 shiny rate) instead of 3-bit.

Characteristic

public override int Characteristic => 
    EntityCharacteristic.GetCharacteristicInit0(EncryptionConstant, IV32);

Based on Encryption Constant and IVs.

Migration from Gen 8

When migrating from Gen 8 to Gen 9:

Encryption Constant preserved
PID preserved
IVs preserved
Tera Type assigned based on species
Obedience Level set based on current level
Scale values generated
Tech Records preserved
Ribbons preserved where applicable

Core Classes

PKM Formats

Save File Types

Editing

Legality

Utilities

​PK9 and PA9 Classes

​PK9 Class

​Format Specifications

​Key Features

​Terastallization

​Obedience Level

​Scale System

​Data Structure

​Important Properties

​Tech Records Continued

​Battle Version

​HOME Tracker

​Tera Type System

​Relearn Move Management

​PA9 Class

​Format Specifications

​Key Features

​Alpha Pokémon (Returning)

​Plus Records

​Data Structure

​Differences from PK9

​Added Features

​Removed Features

​Modified Features

​Comparison Table

​Code Examples

​Creating a PK9 with Tera Type

​Checking Tera Type

​Creating an Alpha PA9

​Setting Scale Values

​Fixing Relearn Moves

​Handler Update System

​New Gen 9 Features

​Unhatched Eggs

​Enhanced Shiny Calculation

​Characteristic

​Migration from Gen 8

​See Also

Build docs developers (and LLMs) love

PK9 and PA9 Classes

PK9 Class

Format Specifications

Key Features

Terastallization

Obedience Level

Scale System

Data Structure

Important Properties

Tech Records Continued

Battle Version

HOME Tracker

Tera Type System

Relearn Move Management

PA9 Class

Format Specifications

Key Features

Alpha Pokémon (Returning)

Plus Records

Data Structure

Differences from PK9

Added Features

Removed Features

Modified Features

Comparison Table

Code Examples

Creating a PK9 with Tera Type

Checking Tera Type

Creating an Alpha PA9

Setting Scale Values

Fixing Relearn Moves

Handler Update System

New Gen 9 Features

Unhatched Eggs

Enhanced Shiny Calculation

Characteristic

Migration from Gen 8

See Also