diff --git a/.github/workflows/android.yml b/.github/workflows/android.yml
index db390d8..291a58a 100644
--- a/.github/workflows/android.yml
+++ b/.github/workflows/android.yml
@@ -52,8 +52,19 @@ jobs:
         with:
           distribution: temurin
           java-version: 17
-          # Caches ~/.gradle so the toolchain and dependencies are not re-downloaded every run.
-          cache: gradle
+
+      # Caches ~/.gradle so the toolchain and dependencies are not re-downloaded every run.
+      # Not setup-java's `cache: gradle`: that hashes *.gradle files at setup time, and
+      # android/ does not exist until prebuild, so it fails the job before anything builds.
+      # The lockfile and app.json are what actually decide the native dependency set.
+      - uses: actions/cache@v4
+        with:
+          path: |
+            ~/.gradle/caches
+            ~/.gradle/wrapper
+          key: gradle-${{ runner.os }}-${{ hashFiles('pnpm-lock.yaml', 'apps/mobile/app.json') }}
+          restore-keys: |
+            gradle-${{ runner.os }}-
 
       - name: Install dependencies
         run: pnpm install --frozen-lockfile
diff --git a/apps/api/src/context/detectors.ts b/apps/api/src/context/detectors.ts
index 51871ea..a8cdcda 100644
--- a/apps/api/src/context/detectors.ts
+++ b/apps/api/src/context/detectors.ts
@@ -1,6 +1,7 @@
 import { Types } from 'mongoose';
 import {
   SUGGEST_THRESHOLD,
+  addLocalDays,
   localMinutesOfDay,
   todayLocalDate,
   type Evidence,
@@ -217,8 +218,9 @@ export async function runDetectors(
     PersonalEventModel.find({ userId: uid, localDate }).lean<EventLean[]>(),
     PersonalEventModel.find({
       userId: uid,
-      localDate: { $lt: localDate },
-      timestamp: { $gte: new Date(Date.now() - 21 * 86_400_000) },
+      // Anchored on the day being evaluated, not the wall clock: a run for a past
+      // localDate must see the three weeks before THAT day, or its history is empty.
+      localDate: { $gte: addLocalDays(localDate, -21), $lt: localDate },
     }).lean<EventLean[]>(),
     UserPreferenceModel.findOne({ userId: uid }).lean(),
   ]);
diff --git a/apps/mobile/src/theme/ThemeProvider.persistence.test.ts b/apps/mobile/src/theme/ThemeProvider.persistence.test.ts
index 56cb634..42c2631 100644
--- a/apps/mobile/src/theme/ThemeProvider.persistence.test.ts
+++ b/apps/mobile/src/theme/ThemeProvider.persistence.test.ts
@@ -131,11 +131,18 @@ describe('hydrate', () => {
 });
 
 describe('setPreference', () => {
-  it('applies the choice to memory immediately', () => {
+  it('applies the choice to memory immediately', async () => {
     usePreferenceStore.getState().setPreference('dark');
     // Synchronous on purpose: the theme must flip on the very next render, not once a
     // device write has come back.
     expect(usePreferenceStore.getState().preference).toBe('dark');
+
+    // Not part of the assertion — it keeps the unawaited write from outliving this test.
+    // The `beforeEach` drain is one macrotask, and on a loaded CI runner the store's
+    // `await import()` takes longer than that. Left in flight it overlaps the next test's
+    // import, and Vitest then resolves that second import to the REAL async-storage
+    // module (`window is not defined`, swallowed by the store), so its write never happens.
+    await vi.waitFor(() => expect(setItem).toHaveBeenCalledWith(STORAGE_KEY, 'dark'));
   });
 
   it('persists the choice under the documented key', async () => {