diff --git a/sim/battle.js b/sim/battle.js
index 846fead727b03..47aa54b462d5c 100644
--- a/sim/battle.js
+++ b/sim/battle.js
@@ -135,8 +135,6 @@ class Battle extends Dex.ModdedDex {
 		this.abilityOrder = 0;
 		/** @type {''} */
 		this.NOT_FAILURE = '';
-		/** @type {boolean} */
-		this.LEGACY_API_DO_NOT_USE = false;
 
 		/** @type {PRNG} */
 		this.prng = options.prng || new PRNG(options.seed || undefined);
@@ -3183,13 +3181,10 @@ class Battle extends Dex.ModdedDex {
 	 * @param {string[]} inputs
 	 */
 	makeChoices(...inputs) {
-		const oldFlag = this.LEGACY_API_DO_NOT_USE;
-		this.LEGACY_API_DO_NOT_USE = false;
 		for (const [i, input] of inputs.entries()) {
 			this.sides[i].choose(input);
 		}
 		this.commitDecisions();
-		this.LEGACY_API_DO_NOT_USE = oldFlag;
 	}
 
 	commitDecisions() {
@@ -3197,12 +3192,9 @@ class Battle extends Dex.ModdedDex {
 
 		let oldQueue = this.queue;
 		this.queue = [];
-		let oldFlag = this.LEGACY_API_DO_NOT_USE;
-		this.LEGACY_API_DO_NOT_USE = false;
 		for (const side of this.sides) {
 			side.autoChoose();
 		}
-		this.LEGACY_API_DO_NOT_USE = oldFlag;
 		let p1choice = this.p1.getChoice();
 		if (p1choice) this.inputLog.push(`>p1 ${p1choice}`);
 		let p2choice = this.p2.getChoice();
diff --git a/sim/side.js b/sim/side.js
index 5e61706913e3d..891d5db01f022 100644
--- a/sim/side.js
+++ b/sim/side.js
@@ -467,7 +467,6 @@ class Side {
 		if (ultra) this.choice.ultra = true;
 		if (zMove) this.choice.zMove = true;
 
-		if (this.battle.LEGACY_API_DO_NOT_USE && !this.battle.checkActions()) return this;
 		return true;
 	}
 
@@ -548,7 +547,6 @@ class Side {
 			target: targetPokemon,
 		});
 
-		if (this.battle.LEGACY_API_DO_NOT_USE && !this.battle.checkActions()) return this;
 		return true;
 	}
 
@@ -602,7 +600,6 @@ class Side {
 			});
 		}
 
-		if (this.battle.LEGACY_API_DO_NOT_USE && !this.battle.checkActions()) return this;
 		return true;
 	}
 
@@ -628,7 +625,6 @@ class Side {
 			pokemon: pokemon,
 		});
 
-		if (this.battle.LEGACY_API_DO_NOT_USE && !this.battle.checkActions()) return this;
 		return true;
 	}
 
@@ -787,28 +783,9 @@ class Side {
 		this.choice.actions.push({
 			choice: 'pass',
 		});
-		if (this.battle.LEGACY_API_DO_NOT_USE && !this.battle.checkActions()) return this;
 		return true;
 	}
 
-	/**
-	 * @return {boolean | Side}
-	 */
-	chooseDefault() {
-		if (!this.battle.LEGACY_API_DO_NOT_USE) throw new Error(`This is a legacy API, it's called autoChoose now`);
-		if (this.isChoiceDone()) {
-			throw new Error(`You've already chosen actions for ${this.id}.`);
-		}
-		if (this.currentRequest === 'teampreview') {
-			this.chooseTeam();
-		} else if (this.currentRequest === 'switch') {
-			while (this.chooseSwitch() !== true && !this.isChoiceDone());
-		} else if (this.currentRequest === 'move') {
-			while (this.chooseMove() !== true && !this.isChoiceDone());
-		}
-		return this;
-	}
-
 	/**
 	 * Automatically finish a choice if not currently complete
 	 */
diff --git a/test/common.js b/test/common.js
index bdfdb837a3284..8735fb829bc67 100644
--- a/test/common.js
+++ b/test/common.js
@@ -112,7 +112,6 @@ class TestTools {
 			// will be used.
 			seed: options.seed || DEFAULT_SEED,
 		});
-		battle.LEGACY_API_DO_NOT_USE = true;
 		if (teams) {
 			for (let i = 0; i < teams.length; i++) {
 				assert(Array.isArray(teams[i]), "Team provided is not an array");
diff --git a/test/simulator/misc/decisions.js b/test/simulator/misc/decisions.js
index 0b21724450fe2..3c28e9982ceaf 100644
--- a/test/simulator/misc/decisions.js
+++ b/test/simulator/misc/decisions.js
@@ -1164,17 +1164,19 @@ describe('Choice internals', function () {
 		]);
 
 		assert.strictEqual(battle.turn, 1);
-		p1.chooseMove(1).chooseSwitch(4);
-		assert(!p2.chooseSwitch(3));
-		p2.chooseMove(1).chooseMove(1);
+		p1.choose('move recover, switch 4');
+		assert(!p2.choose('switch 3'));
+		p2.choose('move recover, move recover');
+		battle.checkActions();
 
 		assert.strictEqual(battle.turn, 2);
 		assert.strictEqual(p1.active[0].name, 'Mew');
 		assert.strictEqual(p1.active[1].name, 'Ekans');
 
-		p1.chooseSwitch(4).chooseMove(1);
-		assert(!p2.chooseSwitch(3));
-		p2.chooseMove(1).chooseMove(1);
+		p1.choose('switch 4, move leer');
+		assert(!p2.choose('switch 3'));
+		p2.choose('move recover, move recover');
+		battle.checkActions();
 
 		assert.strictEqual(battle.turn, 3);
 		assert.strictEqual(p1.active[0].name, 'Bulbasaur');