diff --git a/src/engine/__tests__/automation.test.ts b/src/engine/__tests__/automation.test.ts
index 3fbbfa8..8839051 100644
--- a/src/engine/__tests__/automation.test.ts
+++ b/src/engine/__tests__/automation.test.ts
@@ -2,6 +2,7 @@ import { describe, expect, it } from 'vitest';
 import { buildContent } from '../../content/schema';
 import {
   addToAutomationQueue,
+  automationUnlockThreshold,
   clearAutomationQueue,
   isAutomationUnlocked,
   removeFromAutomationQueue,
@@ -32,10 +33,32 @@ function automationContent() {
         durationMs: 100,
         yields: [{ resourceId: 'renown', amount: 1 }],
       },
+      {
+        id: 'train',
+        name: 'Train',
+        group: DEFAULT_GROUP,
+        durationMs: 100,
+        yields: [{ resourceId: 'renown', amount: 1 }],
+        automation: { unlockAfterManualCompletions: 2 },
+      },
     ],
   });
 }
 
+describe('automationUnlockThreshold()', () => {
+  it('returns the action-specific automation threshold when configured', () => {
+    const content = automationContent();
+
+    expect(automationUnlockThreshold(content, 'train')).toBe(2);
+  });
+
+  it('defaults to one manual completion when automation config is absent', () => {
+    const content = automationContent();
+
+    expect(automationUnlockThreshold(content, 'survey')).toBe(1);
+  });
+});
+
 describe('isAutomationUnlocked()', () => {
   it('returns false before the first manual completion when an action unlocks after one', () => {
     const content = automationContent();
@@ -109,6 +132,15 @@ describe('automation queue CRUD', () => {
     expect(() => removeFromAutomationQueue(state, 1)).toThrow(RangeError);
   });
 
+  it('throws RangeError when removing a non-integer index', () => {
+    const content = automationContent();
+    const state = createGameState(content);
+    state.automationQueue = ['forage'];
+
+    expect(() => removeFromAutomationQueue(state, 0.5)).toThrow(RangeError);
+    expect(state.automationQueue).toEqual(['forage']);
+  });
+
   it('empties the queue', () => {
     const content = automationContent();
     const state = createGameState(content);
diff --git a/src/engine/automation.ts b/src/engine/automation.ts
index 08c6969..e618e38 100644
--- a/src/engine/automation.ts
+++ b/src/engine/automation.ts
@@ -37,7 +37,7 @@ export function addToAutomationQueue(state: GameState, content: Content, actionI
 }
 
 export function removeFromAutomationQueue(state: GameState, index: number): void {
-  if (index < 0 || index >= state.automationQueue.length) {
+  if (!Number.isInteger(index) || index < 0 || index >= state.automationQueue.length) {
     throw new RangeError(`Automation queue index ${index} is out of range`);
   }
   state.automationQueue.splice(index, 1);
diff --git a/src/engine/game.ts b/src/engine/game.ts
index 94f823e..74aedda 100644
--- a/src/engine/game.ts
+++ b/src/engine/game.ts
@@ -103,11 +103,7 @@ function grantYields(state: GameState, content: Content, actionId: string): void
   }
 }
 
-export function recordManualCompletion(
-  state: GameState,
-  content: Content,
-  actionId: string,
-): void {
+export function recordManualCompletion(state: GameState, content: Content, actionId: string): void {
   if (!content.actionsById[actionId]) return;
   state.manualCompletionCounts[actionId] = (state.manualCompletionCounts[actionId] ?? 0) + 1;
 }