src/engine/__tests__/game.test.ts

@@ -7,6 +7,7 @@ import {
   createGameState,
   enqueueAction,
   executeInstant,
+  maybeStartLoopAction,
   startAction,
   tickGame,
 } from '../game';
@@ -402,3 +403,46 @@ describe('executeInstant()', () => {
     expect(() => executeInstant(state, instantContent, 'buy_supply')).toThrow(/Cannot/);
   });
 });
+
+describe('loop idle runner', () => {
+  const loopContent = buildContent({
+    resources: [{ id: 'supplies', name: 'Supplies', startAmount: 0 }],
+    actions: [
+      {
+        id: 'rest',
+        name: 'Rest',
+        kind: 'loop',
+        group: { id: 'camp_loop', label: 'Camp' },
+        durationMs: 1000,
+        loopPriority: 0,
+        yields: [{ resourceId: 'supplies', amount: 1 }],
+      },
+    ],
+  });
+
+  it('defaults enabledLoopActionIds to empty', () => {
+    const state = createGameState(loopContent);
+    expect(state.enabledLoopActionIds).toEqual({});
+  });
+
+  it('starts enabled loop action when idle', () => {
+    const state = createGameState(loopContent);
+    state.enabledLoopActionIds = { rest: true };
+    maybeStartLoopAction(state, loopContent);
+    expect(state.activeActionId).toBe('rest');
+  });
+
+  it('does not start loop when queue has items', () => {
+    const state = createGameState(loopContent);
+    state.enabledLoopActionIds = { rest: true };
+    state.actionQueue.push('rest');
+    maybeStartLoopAction(state, loopContent);
+    expect(state.activeActionId).toBeNull();
+  });
+
+  it('does not start a disabled loop action', () => {
+    const state = createGameState(loopContent);
+    maybeStartLoopAction(state, loopContent);
+    expect(state.activeActionId).toBeNull();
+  });
+});

src/engine/__tests__/save.test.ts

@@ -70,6 +70,15 @@ describe('createSave()', () => {
     expect(save.state.currentStoryNodeId).toBe('route_a_beat');
     expect(save.state.seenStoryNodeIds).toHaveLength(2);
   });
+
+  it('snapshots enabledLoopActionIds in the save payload and isolates from mutation', () => {
+    const state = sampleState();
+    state.enabledLoopActionIds = { rest: true };
+    const save = createSave(state, 1700);
+    expect(save.state.enabledLoopActionIds).toEqual({ rest: true });
+    state.enabledLoopActionIds.rest = false;
+    expect(save.state.enabledLoopActionIds).toEqual({ rest: true });
+  });
 });
 
 describe('serialize / deserialize round-trip', () => {
@@ -84,6 +93,27 @@ describe('serialize / deserialize round-trip', () => {
     const restored = fromExportString(toExportString(save));
     expect(restored).toEqual(save);
   });
+
+  it('preserves enabledLoopActionIds through a round-trip', () => {
+    const state = sampleState();
+    state.enabledLoopActionIds = { rest: true, patrol: false };
+    const restored = deserializeSave(serializeSave(createSave(state, 1700)));
+    expect(restored.state.enabledLoopActionIds).toEqual({ rest: true, patrol: false });
+  });
+
+  it('defaults enabledLoopActionIds to {} when absent from save JSON', () => {
+    const json = JSON.stringify({
+      version: 1,
+      savedAt: 1700,
+      state: {
+        resources: { gold: 0 },
+        activeActionId: null,
+        actionElapsedMs: 0,
+      },
+    });
+    const restored = deserializeSave(json);
+    expect(restored.state.enabledLoopActionIds).toEqual({});
+  });
 });
 
 describe('invalid / tampered saves', () => {

src/engine/game.ts

@@ -26,6 +26,8 @@ export interface GameState {
   currentStoryNodeId: string;
   /** Story node ids the player has already seen. */
   seenStoryNodeIds: string[];
+  /** loop-kind action id -> whether the player has enabled it for idle running. */
+  enabledLoopActionIds: Record<string, boolean>;
 }
 
 export function createGameState(content: Content): GameState {
@@ -41,6 +43,7 @@ export function createGameState(content: Content): GameState {
     storyFlags: {},
     currentStoryNodeId: '',
     seenStoryNodeIds: [],
+    enabledLoopActionIds: {},
   };
 }
 
@@ -197,6 +200,26 @@ export function executeStoryAction(
   applyChoice(state, content, action.storyChoiceId);
 }
 
+/**
+ * Start the highest-priority enabled, available loop action when the game is idle.
+ * Invoked by the runtime AFTER each live tick — never from `tickGame`, so loop
+ * actions do not run during offline catch-up (which replays `tickGame` directly).
+ */
+export function maybeStartLoopAction(state: GameState, content: Content): void {
+  if (state.activeActionId !== null || state.actionQueue.length > 0) return;
+
+  const candidates = content.actions
+    .filter((a) => a.kind === 'loop' && state.enabledLoopActionIds[a.id])
+    .sort((a, b) => (a.loopPriority ?? 0) - (b.loopPriority ?? 0));
+
+  for (const action of candidates) {
+    if (isActionAvailable(state, content, action.id)) {
+      beginAction(state, content, action.id);
+      return;
+    }
+  }
+}
+
 /**
  * Advance the active action by `tickMs`. On completion, grants yields and
  * advances the queue — actions do not auto-repeat when the queue is empty.

src/engine/save.ts

@@ -32,6 +32,7 @@ export const gameStateSchema = z.object({
   storyFlags: z.record(z.string(), z.boolean()).default({}),
   currentStoryNodeId: z.string().default(''),
   seenStoryNodeIds: z.array(z.string()).default([]),
+  enabledLoopActionIds: z.record(z.string(), z.boolean()).default({}),
 });
 
 export const saveSchema = z.object({
@@ -55,6 +56,7 @@ export function createSave(state: GameState, now: number): SaveData {
       storyFlags: { ...state.storyFlags },
       currentStoryNodeId: state.currentStoryNodeId,
       seenStoryNodeIds: [...state.seenStoryNodeIds],
+      enabledLoopActionIds: { ...state.enabledLoopActionIds },
     },
   };
 }

src/state/__tests__/persistence.test.ts

@@ -98,6 +98,7 @@ describe('loadGame()', () => {
           storyFlags: {},
           currentStoryNodeId: '',
           seenStoryNodeIds: [],
+          enabledLoopActionIds: {},
         },
         1000,
       ),

src/state/persistence.ts

@@ -106,6 +106,7 @@ export async function loadGame(
       storyFlags: { ...save.state.storyFlags },
       currentStoryNodeId: save.state.currentStoryNodeId ?? '',
       seenStoryNodeIds: [...(save.state.seenStoryNodeIds ?? [])],
+      enabledLoopActionIds: { ...(save.state.enabledLoopActionIds ?? {}) },
     };
     savedAt = save.savedAt;
   } catch {