diff --git a/sim/battle-actions.ts b/sim/battle-actions.ts
index d21ebc73dc62f..6b25f6a32e1cc 100644
--- a/sim/battle-actions.ts
+++ b/sim/battle-actions.ts
@@ -175,8 +175,9 @@ export class BattleActions {
 				const nextSwitch = this.battle.queue.shift();
 				switchersIn.push(nextSwitch!.pokemon!);
 			}
+			this.battle.prng.shuffle(this.battle.speedTieResolution);
 			this.battle.fieldEvent('SwitchIn', switchersIn);
-	
+
 			if (!pokemon.hp) return false;
 			pokemon.isStarted = true;
 			pokemon.draggedIn = null;
diff --git a/sim/battle.ts b/sim/battle.ts
index 00564644ff907..7d36a39ea0653 100644
--- a/sim/battle.ts
+++ b/sim/battle.ts
@@ -174,6 +174,7 @@ export class Battle {
 	lastDamage: number;
 	effectOrder: number;
 	quickClawRoll: boolean;
+	speedTieResolution: number[];
 
 	teamGenerator: ReturnType<typeof Teams.getGenerator> | null;
 
@@ -261,6 +262,10 @@ export class Battle {
 		this.lastDamage = 0;
 		this.effectOrder = 0;
 		this.quickClawRoll = false;
+		this.speedTieResolution = [];
+		for (let i = 0; i < this.activePerHalf * 2; i++) {
+			this.speedTieResolution.push(i / (this.activePerHalf * 2));
+		}
 
 		this.teamGenerator = null;
 
@@ -950,6 +955,14 @@ export class Battle {
 		}
 		if (handler.effectHolder && (handler.effectHolder as Pokemon).getStat) {
 			handler.speed = (handler.effectHolder as Pokemon).speed;
+			if (callbackName.endsWith('SwitchIn')) {
+				// Pokemon speeds including ties are resolved before all onSwitchIn handlers and aren't re-sorted in-between
+				// so we add a fractional speed to each Pokemon's respective event handlers by using their unique field position
+				// to index a randomly shuffled array of sequential numbers
+				const allSlots = 'abcdef';
+				const speedTieIndex = allSlots.indexOf((handler.effectHolder as Pokemon).getSlot().charAt(2));
+				handler.speed += this.speedTieResolution[speedTieIndex];
+			}
 		}
 		return handler;
 	}
diff --git a/test/sim/misc/multi-battle.js b/test/sim/misc/multi-battle.js
index ac39e23a26618..ee8c9a43af9c6 100644
--- a/test/sim/misc/multi-battle.js
+++ b/test/sim/misc/multi-battle.js
@@ -24,7 +24,7 @@ describe('Free-for-all', function () {
 		battle.makeChoices();
 		battle.lose('p2');
 		assert(battle.p2.activeRequest.wait);
-		battle.makeChoices('auto', '', 'move uturn', 'auto');
+		battle.makeChoices('auto', '', 'move uturn 1', 'auto');
 		battle.lose('p3');
 		battle.makeChoices();
 		assert.equal(battle.turn, 4);
diff --git a/test/sim/misc/terastal.js b/test/sim/misc/terastal.js
index 85642c411d8d5..372bed78b792b 100644
--- a/test/sim/misc/terastal.js
+++ b/test/sim/misc/terastal.js
@@ -35,9 +35,9 @@ describe("Terastallization", function () {
 
 	it('should give STAB correctly to the user\'s old types', function () {
 		battle = common.createBattle([[
-			{species: 'Ampharos', ability: 'static', moves: ['shockwave', 'swift'], teraType: 'Electric'},
+			{species: 'Ampharos', ability: 'shellarmor', moves: ['shockwave', 'swift'], teraType: 'Electric'},
 		], [
-			{species: 'Ampharos', ability: 'static', moves: ['shockwave', 'swift'], teraType: 'Normal'},
+			{species: 'Ampharos', ability: 'shellarmor', moves: ['shockwave', 'swift'], teraType: 'Normal'},
 		]]);
 		battle.makeChoices('move shockwave terastallize', 'move shockwave terastallize');
 		const teraDamage = battle.p2.active[0].maxhp - battle.p2.active[0].hp;
@@ -47,7 +47,7 @@ describe("Terastallization", function () {
 		const nonTeraDamage = battle.p1.active[0].maxhp - battle.p1.active[0].hp;
 		// 0 SpA Ampharos Shock Wave vs. 0 HP / 0 SpD Ampharos: 40-48
 		assert.bounded(nonTeraDamage, [40, 48],
-			"Terastallizing did not keep old type's STAB; actual damage: " + teraDamage);
+			"Terastallizing did not keep old type's STAB; actual damage: " + nonTeraDamage);
 
 		battle = common.createBattle([[
 			{species: 'Mimikyu', ability: 'disguise', item: 'laggingtail', moves: ['shadowclaw', 'waterfall', 'sleeptalk'], teraType: 'Water'},