diff --git a/src/data/moves/move.ts b/src/data/moves/move.ts
index ea101d24896..400b3f89ef4 100644
--- a/src/data/moves/move.ts
+++ b/src/data/moves/move.ts
@@ -8010,7 +8010,7 @@ export class MoveCondition {
 
 export class FirstMoveCondition extends MoveCondition {
   constructor() {
-    super((user, _target, _move) => user.summonData.waveTurnCount === 1);
+    super((user, _target, _move) => user.tempSummonData.waveTurnCount === 1);
   }
 
   getUserBenefitScore(user: Pokemon, _target: Pokemon, _move: Move): number {
diff --git a/src/data/pokemon-forms.ts b/src/data/pokemon-forms.ts
index f76462d2725..506908c5fc7 100644
--- a/src/data/pokemon-forms.ts
+++ b/src/data/pokemon-forms.ts
@@ -3,7 +3,7 @@ import type Pokemon from "../field/pokemon";
 import { StatusEffect } from "#enums/status-effect";
 import { allMoves } from "./moves/move";
 import { MoveCategory } from "#enums/MoveCategory";
-import type { Constructor, nil } from "#app/utils/common";
+import { isNullOrUndefined, type Constructor, type nil } from "#app/utils/common";
 import { Abilities } from "#enums/abilities";
 import { Moves } from "#enums/moves";
 import { Species } from "#enums/species";
@@ -369,12 +369,10 @@ export class SpeciesFormChangeMoveLearnedTrigger extends SpeciesFormChangeTrigge
 
 export abstract class SpeciesFormChangeMoveTrigger extends SpeciesFormChangeTrigger {
   public movePredicate: (m: Moves) => boolean;
-  public used: boolean;
 
-  constructor(move: Moves | ((m: Moves) => boolean), used = true) {
+  constructor(move: Moves | ((m: Moves) => boolean)) {
     super();
     this.movePredicate = typeof move === "function" ? move : (m: Moves) => m === move;
-    this.used = used;
   }
 }
 
@@ -383,7 +381,7 @@ export class SpeciesFormChangePreMoveTrigger extends SpeciesFormChangeMoveTrigge
 
   canChange(pokemon: Pokemon): boolean {
     const command = globalScene.currentBattle.turnCommands[pokemon.getBattlerIndex()];
-    return !!command?.move && this.movePredicate(command.move.move) === this.used;
+    return !isNullOrUndefined(command?.move) && this.movePredicate(command.move.move);
   }
 }
 
@@ -391,9 +389,7 @@ export class SpeciesFormChangePostMoveTrigger extends SpeciesFormChangeMoveTrigg
   description = i18next.t("pokemonEvolutions:Forms.postMove");
 
   canChange(pokemon: Pokemon): boolean {
-    return (
-      pokemon.summonData && !!pokemon.getLastXMoves(1).filter(m => this.movePredicate(m.move)).length === this.used
-    );
+    return this.movePredicate(pokemon.getLastXMoves()[0].move);
   }
 }
 
diff --git a/src/field/pokemon.ts b/src/field/pokemon.ts
index 7605f66f5be..6b77311e924 100644
--- a/src/field/pokemon.ts
+++ b/src/field/pokemon.ts
@@ -368,6 +368,8 @@ export default abstract class Pokemon extends Phaser.GameObjects.Container {
   public battleData: PokemonBattleData = new PokemonBattleData();
   /** Data that resets on switch or battle end (stat stages, battler tags, etc.) */
   public summonData: PokemonSummonData = new PokemonSummonData();
+  /** Similar to {@linkcode PokemonSummonData}, but is reset on reload (not saved to file). */
+  public tempSummonData: PokemonTempSummonData = new PokemonTempSummonData();
   /** Wave data correponding to moves/ability information revealed */
   public waveData: PokemonWaveData = new PokemonWaveData();
   /** Per-turn data like hit count & flinch tracking */
@@ -1427,7 +1429,6 @@ export default abstract class Pokemon extends Phaser.GameObjects.Container {
   getStat(stat: PermanentStat, bypassSummonData = true): number {
     if (
       !bypassSummonData &&
-      this.summonData &&
       this.summonData.stats[stat] !== 0
     ) {
       return this.summonData.stats[stat];
@@ -2156,10 +2157,9 @@ export default abstract class Pokemon extends Phaser.GameObjects.Container {
       }
     }
 
-    // the type added to Pokemon from moves like Forest's Curse or Trick Or Treat
+    // check type added to Pokemon from moves like Forest's Curse or Trick Or Treat
     if (
       !ignoreOverride &&
-      this.summonData &&
       this.summonData.addedType &&
       !types.includes(this.summonData.addedType)
     ) {
@@ -4967,9 +4967,11 @@ export default abstract class Pokemon extends Phaser.GameObjects.Container {
   }
 
   transferTagsBySourceId(sourceId: number, newSourceId: number): void {
-    this.summonData.tags
-    .filter(t => t.sourceId === sourceId)
-    .forEach(t => (t.sourceId = newSourceId));
+    this.summonData.tags.forEach(t => {
+      if (t.sourceId === sourceId) {
+        t.sourceId = newSourceId;
+      }
+    })
   }
 
   /**
@@ -5646,7 +5648,10 @@ export default abstract class Pokemon extends Phaser.GameObjects.Container {
     return false;
   }
 
-
+  /**
+   * Reset this Pokemon's {@linkcode PokemonSummonData | SummonData} and {@linkcode PokemonTempSummonData | TempSummonData}
+   * in preparation for switching pokemon, as well as removing any relevant on-switch tags.
+   */
   resetSummonData(): void {
     const illusion: IllusionData | null = this.summonData.illusion;
     if (this.summonData.speciesForm) {
@@ -5654,8 +5659,10 @@ export default abstract class Pokemon extends Phaser.GameObjects.Container {
       this.updateFusionPalette();
     }
     this.summonData = new PokemonSummonData();
+    this.tempSummonData = new PokemonTempSummonData();
+
     this.setSwitchOutStatus(false);
-    // TODO: Why do we remove leech seed on resetting summon data? That should be a BattlerTag thing...
+    // TODO: Why do we tick down leech seed on switch
     if (this.getTag(BattlerTagType.SEEDED)) {
       this.lapseTag(BattlerTagType.SEEDED);
     }
@@ -7751,7 +7758,8 @@ export class PokemonSummonData {
   public tags: BattlerTag[] = [];
   public abilitySuppressed = false;
 
-  // Overrides for transform
+  // Overrides for transform.
+  // TODO: Move these into a separate class & add rage fist hit count
   public speciesForm: PokemonSpeciesForm | null = null;
   public fusionSpeciesForm: PokemonSpeciesForm | null = null;
   public ability: Abilities | undefined;
@@ -7772,16 +7780,6 @@ export class PokemonSummonData {
   /** Array containing all berries eaten in the last turn; used by {@linkcode Abilities.CUD_CHEW} */
   public berriesEatenLast: BerryType[] = [];
 
-  /**
-   * The number of turns this pokemon has spent in the active position since entering the battle.
-   * Currently exclusively used for positioning the battle cursor.
-   */
-  public turnCount = 1;
-  /**
-   * The number of turns this pokemon has spent in the active position since starting a new wave.
-   * Used for most "first turn only" conditions ({@linkcode Moves.FAKE_OUT | Fake Out}, {@linkcode Moves.FIRST_IMPRESSION | First Impression}, etc.)
-   */
-  public waveTurnCount = 1;
   /**
    * An array of all moves this pokemon has used since entering the battle.
    * Used for most moves and abilities that check prior move usage or copy already-used moves.
@@ -7796,6 +7794,26 @@ export class PokemonSummonData {
   }
 }
 
+ // TODO: Merge this inside `summmonData` but exclude from save if/when a save data serializer is added
+export class PokemonTempSummonData {
+  /**
+   * The number of turns this pokemon has spent without switching out.
+   * Only currently used for positioning the battle cursor.
+   */
+  turnCount: number = 1;
+
+    /**
+   * The number of turns this pokemon has spent in the active position since the start of the wave
+   * without switching out.
+   * Reset on switch and new wave, but not stored in `SummonData` to avoid being written to the save file.
+
+   * Used to evaluate "first turn only" conditions such as
+   * {@linkcode Moves.FAKE_OUT | Fake Out} and {@linkcode Moves.FIRST_IMPRESSION | First Impression}).
+   */
+  waveTurnCount = 1;
+
+}
+
 /**
  * Persistent data for a {@linkcode Pokemon}.
  * Resets at the start of a new battle (but not on switch).
@@ -7819,7 +7837,7 @@ export class PokemonBattleData {
 
 /**
  * Temporary data for a {@linkcode Pokemon}.
- * Resets on new wave/battle start.
+ * Resets on new wave/battle start (but not on switch).
  */
 export class PokemonWaveData {
   /** Whether the pokemon has endured due to a {@linkcode BattlerTagType.ENDURE_TOKEN} */
@@ -7866,7 +7884,7 @@ export class PokemonTurnData {
   public extraTurns = 0;
   /**
    * All berries eaten by this pokemon in this turn.
-   * Saved into {@linkcode PokemonSummonData | SummonData} by {@linkcode Abilities.CUD_CHEW) on turn end.
+   * Saved into {@linkcode PokemonSummonData | SummonData} by {@linkcode Abilities.CUD_CHEW} on turn end.
    * @see {@linkcode PokemonSummonData.berriesEatenLast}
   */
   public berriesEaten: BerryType[] = []
diff --git a/src/phases/battle-end-phase.ts b/src/phases/battle-end-phase.ts
index 5ccef2c71eb..b4bb28fe55e 100644
--- a/src/phases/battle-end-phase.ts
+++ b/src/phases/battle-end-phase.ts
@@ -60,7 +60,7 @@ export class BattleEndPhase extends BattlePhase {
 
     for (const pokemon of globalScene.getField()) {
       if (pokemon) {
-        pokemon.summonData.waveTurnCount = 1;
+        pokemon.tempSummonData.waveTurnCount = 1;
       }
     }
 
diff --git a/src/phases/field-phase.ts b/src/phases/field-phase.ts
index 98c1ced510f..c37f0e960e7 100644
--- a/src/phases/field-phase.ts
+++ b/src/phases/field-phase.ts
@@ -6,8 +6,7 @@ type PokemonFunc = (pokemon: Pokemon) => void;
 
 export abstract class FieldPhase extends BattlePhase {
   executeForAll(func: PokemonFunc): void {
-    const field = globalScene.getField(true).filter(p => p.summonData);
-    for (const pokemon of field) {
+    for (const pokemon of globalScene.getField(true)) {
       func(pokemon);
     }
   }
diff --git a/src/phases/mystery-encounter-phases.ts b/src/phases/mystery-encounter-phases.ts
index 011dd26db92..fd0c4ef7949 100644
--- a/src/phases/mystery-encounter-phases.ts
+++ b/src/phases/mystery-encounter-phases.ts
@@ -229,8 +229,7 @@ export class MysteryEncounterBattleStartCleanupPhase extends Phase {
 
     // Lapse any residual flinches/endures but ignore all other turn-end battle tags
     const includedLapseTags = [BattlerTagType.FLINCHED, BattlerTagType.ENDURING];
-    const field = globalScene.getField(true).filter(p => p.summonData);
-    field.forEach(pokemon => {
+    globalScene.getField(true).forEach(pokemon => {
       const tags = pokemon.summonData.tags;
       tags
         .filter(
diff --git a/src/phases/switch-summon-phase.ts b/src/phases/switch-summon-phase.ts
index 67691d7e225..bb31f87cc3d 100644
--- a/src/phases/switch-summon-phase.ts
+++ b/src/phases/switch-summon-phase.ts
@@ -33,10 +33,10 @@ export class SwitchSummonPhase extends SummonPhase {
    * @param fieldIndex - Position on the battle field
    * @param slotIndex - The index of pokemon (in party of 6) to switch into
    * @param doReturn - Whether to render "comeback" dialogue
-   * @param player - (Optional) `true` if the switch is from the player
+   * @param player - Whether the switch came from the player or enemy; default `true`
    */
-  constructor(switchType: SwitchType, fieldIndex: number, slotIndex: number, doReturn: boolean, player?: boolean) {
-    super(fieldIndex, player !== undefined ? player : true);
+  constructor(switchType: SwitchType, fieldIndex: number, slotIndex: number, doReturn: boolean, player = true) {
+    super(fieldIndex, player);
 
     this.switchType = switchType;
     this.slotIndex = slotIndex;
@@ -121,14 +121,23 @@ export class SwitchSummonPhase extends SummonPhase {
 
   switchAndSummon() {
     const party = this.player ? this.getParty() : globalScene.getEnemyParty();
-    const switchedInPokemon = party[this.slotIndex];
+    const switchedInPokemon: Pokemon | undefined = party[this.slotIndex];
     this.lastPokemon = this.getPokemon();
+
     applyPreSummonAbAttrs(PreSummonAbAttr, switchedInPokemon);
     applyPreSwitchOutAbAttrs(PreSwitchOutAbAttr, this.lastPokemon);
-    if (this.switchType === SwitchType.BATON_PASS && switchedInPokemon) {
-      (this.player ? globalScene.getEnemyField() : globalScene.getPlayerField()).forEach(enemyPokemon =>
+    if (!switchedInPokemon) {
+      this.end();
+      return;
+    }
+
+    if (this.switchType === SwitchType.BATON_PASS) {
+      // If switching via baton pass, update opposing tags coming from the prior pokemon
+      (this.player ? globalScene.getEnemyField() : globalScene.getPlayerField()).forEach((enemyPokemon: Pokemon) =>
         enemyPokemon.transferTagsBySourceId(this.lastPokemon.id, switchedInPokemon.id),
       );
+
+      // If the recipient pokemon lacks a baton, give our baton to it during the swap
       if (
         !globalScene.findModifier(
           m =>
@@ -141,14 +150,8 @@ export class SwitchSummonPhase extends SummonPhase {
             m instanceof SwitchEffectTransferModifier &&
             (m as SwitchEffectTransferModifier).pokemonId === this.lastPokemon.id,
         ) as SwitchEffectTransferModifier;
-        if (
-          batonPassModifier &&
-          !globalScene.findModifier(
-            m =>
-              m instanceof SwitchEffectTransferModifier &&
-              (m as SwitchEffectTransferModifier).pokemonId === switchedInPokemon.id,
-          )
-        ) {
+
+        if (batonPassModifier) {
           globalScene.tryTransferHeldItemModifier(
             batonPassModifier,
             switchedInPokemon,
@@ -161,49 +164,48 @@ export class SwitchSummonPhase extends SummonPhase {
         }
       }
     }
-    if (switchedInPokemon) {
-      party[this.slotIndex] = this.lastPokemon;
-      party[this.fieldIndex] = switchedInPokemon;
-      const showTextAndSummon = () => {
-        globalScene.ui.showText(
-          this.player
-            ? i18next.t("battle:playerGo", {
-                pokemonName: getPokemonNameWithAffix(switchedInPokemon),
-              })
-            : i18next.t("battle:trainerGo", {
-                trainerName: globalScene.currentBattle.trainer?.getName(
-                  !(this.fieldIndex % 2) ? TrainerSlot.TRAINER : TrainerSlot.TRAINER_PARTNER,
-                ),
-                pokemonName: this.getPokemon().getNameToRender(),
-              }),
-        );
-        /**
-         * If this switch is passing a Substitute, make the switched Pokemon match the returned Pokemon's state as it left.
-         * Otherwise, clear any persisting tags on the returned Pokemon.
-         */
-        if (this.switchType === SwitchType.BATON_PASS || this.switchType === SwitchType.SHED_TAIL) {
-          const substitute = this.lastPokemon.getTag(SubstituteTag);
-          if (substitute) {
-            switchedInPokemon.x += this.lastPokemon.getSubstituteOffset()[0];
-            switchedInPokemon.y += this.lastPokemon.getSubstituteOffset()[1];
-            switchedInPokemon.setAlpha(0.5);
-          }
-        } else {
-          switchedInPokemon.resetSummonData();
+
+    party[this.slotIndex] = this.lastPokemon;
+    party[this.fieldIndex] = switchedInPokemon;
+    const showTextAndSummon = () => {
+      globalScene.ui.showText(
+        this.player
+          ? i18next.t("battle:playerGo", {
+              pokemonName: getPokemonNameWithAffix(switchedInPokemon),
+            })
+          : i18next.t("battle:trainerGo", {
+              trainerName: globalScene.currentBattle.trainer?.getName(
+                !(this.fieldIndex % 2) ? TrainerSlot.TRAINER : TrainerSlot.TRAINER_PARTNER,
+              ),
+              pokemonName: this.getPokemon().getNameToRender(),
+            }),
+      );
+
+      /**
+       * If this switch is passing a Substitute, make the switched Pokemon matches the returned Pokemon's state as it left.
+       * Otherwise, clear any persisting tags on the returned Pokemon.
+       */
+      if (this.switchType === SwitchType.BATON_PASS || this.switchType === SwitchType.SHED_TAIL) {
+        const substitute = this.lastPokemon.getTag(SubstituteTag);
+        if (substitute) {
+          switchedInPokemon.x += this.lastPokemon.getSubstituteOffset()[0];
+          switchedInPokemon.y += this.lastPokemon.getSubstituteOffset()[1];
+          switchedInPokemon.setAlpha(0.5);
         }
-        this.summon();
-      };
-      if (this.player) {
-        showTextAndSummon();
       } else {
-        globalScene.time.delayedCall(1500, () => {
-          this.hideEnemyTrainer();
-          globalScene.pbTrayEnemy.hide();
-          showTextAndSummon();
-        });
+        switchedInPokemon.resetSummonData();
       }
+      this.summon();
+    };
+
+    if (this.player) {
+      showTextAndSummon();
     } else {
-      this.end();
+      globalScene.time.delayedCall(1500, () => {
+        this.hideEnemyTrainer();
+        globalScene.pbTrayEnemy.hide();
+        showTextAndSummon();
+      });
     }
   }
 
@@ -221,15 +223,15 @@ export class SwitchSummonPhase extends SummonPhase {
     const lastPokemonHasForceSwitchAbAttr =
       this.lastPokemon.hasAbilityWithAttr(PostDamageForceSwitchAbAttr) && !this.lastPokemon.isFainted();
 
-    // Compensate for turn spent summoning
-    // Or compensate for force switch move if switched out pokemon is not fainted
+    // Compensate for turn spent summoning/forced switch if switched out pokemon is not fainted.
+    // Needed as we increment turn counters in `TurnEndPhase`.
     if (
       currentCommand === Command.POKEMON ||
       lastPokemonIsForceSwitchedAndNotFainted ||
       lastPokemonHasForceSwitchAbAttr
     ) {
-      pokemon.summonData.turnCount--;
-      pokemon.summonData.waveTurnCount--;
+      pokemon.tempSummonData.turnCount--;
+      pokemon.tempSummonData.waveTurnCount--;
     }
 
     if (this.switchType === SwitchType.BATON_PASS && pokemon) {
@@ -247,7 +249,7 @@ export class SwitchSummonPhase extends SummonPhase {
       pokemon.turnData.switchedInThisTurn = true;
     }
 
-    this.lastPokemon?.resetSummonData();
+    this.lastPokemon.resetSummonData();
 
     globalScene.triggerPokemonFormChange(pokemon, SpeciesFormChangeActiveTrigger, true);
     // Reverts to weather-based forms when weather suppressors (Cloud Nine/Air Lock) are switched out
diff --git a/src/phases/turn-end-phase.ts b/src/phases/turn-end-phase.ts
index c7868324209..756c497802b 100644
--- a/src/phases/turn-end-phase.ts
+++ b/src/phases/turn-end-phase.ts
@@ -56,8 +56,8 @@ export class TurnEndPhase extends FieldPhase {
       globalScene.applyModifiers(TurnStatusEffectModifier, pokemon.isPlayer(), pokemon);
       globalScene.applyModifiers(TurnHeldItemTransferModifier, pokemon.isPlayer(), pokemon);
 
-      pokemon.summonData.turnCount++;
-      pokemon.summonData.waveTurnCount++;
+      pokemon.tempSummonData.turnCount++;
+      pokemon.tempSummonData.waveTurnCount++;
     };
 
     this.executeForAll(handlePokemon);
diff --git a/src/phases/turn-start-phase.ts b/src/phases/turn-start-phase.ts
index 622b9cdcbd1..b802780bbb8 100644
--- a/src/phases/turn-start-phase.ts
+++ b/src/phases/turn-start-phase.ts
@@ -72,19 +72,16 @@ export class TurnStartPhase extends FieldPhase {
     // This occurs before the main loop because of battles with more than two Pokemon
     const battlerBypassSpeed = {};
 
-    globalScene
-      .getField(true)
-      .filter(p => p.summonData)
-      .map(p => {
-        const bypassSpeed = new BooleanHolder(false);
-        const canCheckHeldItems = new BooleanHolder(true);
-        applyAbAttrs(BypassSpeedChanceAbAttr, p, null, false, bypassSpeed);
-        applyAbAttrs(PreventBypassSpeedChanceAbAttr, p, null, false, bypassSpeed, canCheckHeldItems);
-        if (canCheckHeldItems.value) {
-          globalScene.applyModifiers(BypassSpeedChanceModifier, p.isPlayer(), p, bypassSpeed);
-        }
-        battlerBypassSpeed[p.getBattlerIndex()] = bypassSpeed;
-      });
+    globalScene.getField(true).map(p => {
+      const bypassSpeed = new BooleanHolder(false);
+      const canCheckHeldItems = new BooleanHolder(true);
+      applyAbAttrs(BypassSpeedChanceAbAttr, p, null, false, bypassSpeed);
+      applyAbAttrs(PreventBypassSpeedChanceAbAttr, p, null, false, bypassSpeed, canCheckHeldItems);
+      if (canCheckHeldItems.value) {
+        globalScene.applyModifiers(BypassSpeedChanceModifier, p.isPlayer(), p, bypassSpeed);
+      }
+      battlerBypassSpeed[p.getBattlerIndex()] = bypassSpeed;
+    });
 
     // The function begins sorting orderedTargets based on command priority, move priority, and possible speed bypasses.
     // Non-FIGHT commands (SWITCH, BALL, RUN) have a higher command priority and will always occur before any FIGHT commands.
diff --git a/src/ui/battle-info.ts b/src/ui/battle-info.ts
index e96bf8b8cf2..cabe897d7b6 100644
--- a/src/ui/battle-info.ts
+++ b/src/ui/battle-info.ts
@@ -794,7 +794,7 @@ export default class BattleInfo extends Phaser.GameObjects.Container {
     const nameSizeTest = addTextObject(0, 0, displayName, TextStyle.BATTLE_INFO);
     nameTextWidth = nameSizeTest.displayWidth;
 
-    const gender = pokemon.summonData?.illusion?.gender ?? pokemon.gender;
+    const gender = pokemon.summonData.illusion?.gender ?? pokemon.gender;
     while (
       nameTextWidth >
       (this.player || !this.boss ? 60 : 98) -
diff --git a/src/ui/fight-ui-handler.ts b/src/ui/fight-ui-handler.ts
index fc194bff962..5a0978a934d 100644
--- a/src/ui/fight-ui-handler.ts
+++ b/src/ui/fight-ui-handler.ts
@@ -127,7 +127,7 @@ export default class FightUiHandler extends UiHandler implements InfoToggle {
     messageHandler.commandWindow.setVisible(false);
     messageHandler.movesWindowContainer.setVisible(true);
     const pokemon = (globalScene.getCurrentPhase() as CommandPhase).getPokemon();
-    if (pokemon.summonData.turnCount <= 1) {
+    if (pokemon.tempSummonData.turnCount <= 1) {
       this.setCursor(0);
     } else {
       this.setCursor(this.getCursor());
diff --git a/src/ui/target-select-ui-handler.ts b/src/ui/target-select-ui-handler.ts
index 914914b2a4e..5e14e5f7771 100644
--- a/src/ui/target-select-ui-handler.ts
+++ b/src/ui/target-select-ui-handler.ts
@@ -71,7 +71,7 @@ export default class TargetSelectUiHandler extends UiHandler {
    */
   resetCursor(cursorN: number, user: Pokemon): void {
     if (!isNullOrUndefined(cursorN)) {
-      if ([BattlerIndex.PLAYER, BattlerIndex.PLAYER_2].includes(cursorN) || user.summonData.waveTurnCount === 1) {
+      if ([BattlerIndex.PLAYER, BattlerIndex.PLAYER_2].includes(cursorN) || user.tempSummonData.waveTurnCount === 1) {
         // Reset cursor on the first turn of a fight or if an ally was targeted last turn
         cursorN = -1;
       }