diff --git a/src/schedule/schedule_manager.cpp b/src/schedule/schedule_manager.cpp
index a16bc94..395b540 100644
--- a/src/schedule/schedule_manager.cpp
+++ b/src/schedule/schedule_manager.cpp
@@ -87,16 +87,20 @@ void ScheduleManager::refreshOnce() {
 
 void ScheduleManager::start(db::DatabaseManager& db, const std::string& timezone,
                             std::function<void()> onChanged) {
-    std::lock_guard<std::mutex> lock(mutex_);
-    if (started_) return;
-    started_ = true;
-    db_ = &db;
-    timezone_ = timezone;
-    onChanged_ = std::move(onChanged);
-    licenseKey_ = db.getKV(db::KV_LICENSE_KEY);
-    enabled_ = true; // config supplies the toggle via setEnabled()
+    {
+        std::lock_guard<std::mutex> lock(mutex_);
+        if (started_) return;
+        started_ = true;
+        db_ = &db;
+        timezone_ = timezone;
+        onChanged_ = std::move(onChanged);
+        licenseKey_ = db.getKV(db::KV_LICENSE_KEY);
+        enabled_ = true; // config supplies the toggle via setEnabled()
+    }
 
-    // Offline first: load any cached payload immediately.
+    // Offline first: load any cached payload immediately. Called outside the
+    // lock because loadCache() acquires mutex_ itself; holding it here would
+    // self-deadlock on the non-recursive mutex when a cache file exists.
     loadCache();
 
     stop_.store(false);
diff --git a/tests/test_schedule_engine.cpp b/tests/test_schedule_engine.cpp
index a7c11d7..9c154d6 100644
--- a/tests/test_schedule_engine.cpp
+++ b/tests/test_schedule_engine.cpp
@@ -297,6 +297,34 @@ TEST(ScheduleManagerTest, OfflineFallsBackToCache) {
     radiantwave::sync::schedule_cache::clear();
 }
 
+// Regression: start() must not deadlock when a cache file is present. It used
+// to hold mutex_ and then call loadCache(), which re-locked the same
+// non-recursive mutex (self-deadlock), blocking SDL_AppInit before the first
+// frame was ever presented — the kiosk sat on a black screen.
+TEST(ScheduleManagerTest, StartWithCachedPayloadDoesNotDeadlock) {
+    const std::string dir = tempCacheDir();
+    setenv("HOME", dir.c_str(), 1);
+
+    SchedulePayload p = dailyPayload();
+    ASSERT_TRUE(radiantwave::sync::schedule_cache::write(p, "\"cached\""));
+
+    const std::string dbPath =
+        (std::filesystem::temp_directory_path() / "rw_schedule_start_test.db")
+            .string();
+    std::filesystem::remove(dbPath);
+    radiantwave::db::DatabaseManager db;
+    ASSERT_TRUE(db.initialize(dbPath));
+
+    radiantwave::schedule::ScheduleManager manager;
+    manager.start(db, "UTC");
+    EXPECT_TRUE(manager.hasSchedule());
+    manager.shutdown();
+
+    db.close();
+    std::filesystem::remove(dbPath);
+    radiantwave::sync::schedule_cache::clear();
+}
+
 // ─── Phase 5: consume real Portal-generated payloads ───────────────────
 //
 // These fixtures were captured from a running Portal (GET