fix: check ps_sync_state instead of ps_buckets for sync completion

ps_buckets is only populated when checkpoint messages are received,
which may not happen even though data syncs. ps_sync_state tracks
when sync actually completed and is more reliable.

Author: binarylogic

internal/powersync/sync.go

@@ -157,7 +157,7 @@ func (s *Sync) IsRunning() bool {
 	return s.cancel != nil
 }
 
-// WaitForFirstSync blocks until the first sync completes (data in ps_buckets).
+// WaitForFirstSync blocks until the first sync completes.
 // Returns an error if the context is cancelled or sync fails.
 func (s *Sync) WaitForFirstSync(ctx context.Context) error {
 	ticker := time.NewTicker(100 * time.Millisecond)
@@ -173,10 +173,11 @@ func (s *Sync) WaitForFirstSync(ctx context.Context) error {
 				return err
 			}
 
-			// Check if ps_buckets has data
+			// Check if sync has completed by looking at ps_sync_state
+			// This table is populated when PowerSync finishes its first sync
 			if s.db != nil {
 				var count int64
-				err := s.db.QueryRow("SELECT COUNT(*) FROM ps_buckets").Scan(&count)
+				err := s.db.QueryRow("SELECT COUNT(*) FROM ps_sync_state").Scan(&count)
 				if err == nil && count > 0 {
 					return nil
 				}

internal/powersync/sync_test.go

@@ -459,15 +459,15 @@ func TestSync_TransientErrorRetries(t *testing.T) {
 func TestSync_WaitForFirstSync(t *testing.T) {
 	t.Parallel()
 
-	t.Run("returns when ps_buckets has data", func(t *testing.T) {
+	t.Run("returns when ps_sync_state has data", func(t *testing.T) {
 		t.Parallel()
 
 		db := powersynctest.OpenTestDBWithSchema(t)
 
 		mock := &powersynctest.MockStreamer{
 			ConnectFunc: func(ctx context.Context, req *powersync.StreamingSyncRequest, handler powersync.LineHandler) error {
-				// Simulate sync by inserting data into ps_buckets
-				_, err := db.Exec("INSERT INTO ps_buckets (name) VALUES ('test')")
+				// Simulate sync completion by inserting into ps_sync_state
+				_, err := db.Exec("INSERT INTO ps_sync_state (priority, last_synced_at) VALUES (0, datetime('now'))")
 				if err != nil {
 					return err
 				}