diff --git a/acestep/ui/gradio/events/results/batch_management.py b/acestep/ui/gradio/events/results/batch_management.py
index 7db51ac6..1627548c 100644
--- a/acestep/ui/gradio/events/results/batch_management.py
+++ b/acestep/ui/gradio/events/results/batch_management.py
@@ -186,6 +186,7 @@ def generate_next_batch_background(
     next_batch_idx = current_batch_index + 1
 
     if next_batch_idx in batch_queue and batch_queue[next_batch_idx].get("status") == "completed":
+        total_batches = max(total_batches, next_batch_idx + 1)
         return (
             batch_queue, total_batches,
             t("messages.batch_ready", n=next_batch_idx + 1),
diff --git a/acestep/ui/gradio/events/results/batch_navigation.py b/acestep/ui/gradio/events/results/batch_navigation.py
index 3c8d5c4d..39ed187c 100644
--- a/acestep/ui/gradio/events/results/batch_navigation.py
+++ b/acestep/ui/gradio/events/results/batch_navigation.py
@@ -86,6 +86,11 @@ def navigate_to_next_batch(autogen_enabled, current_batch_index, total_batches,
     Yields:
         Two tuples of 49 Gradio component updates each.
     """
+    # Derive actual total from batch_queue so we never rely on a stale
+    # total_batches state value (the background generator may have added
+    # batches after total_batches was last written to the Gradio state).
+    total_batches = max(total_batches, len(batch_queue))
+
     if current_batch_index >= total_batches - 1:
         gr.Warning(t("messages.at_last_batch"))
         yield tuple([gr.update()] * 49)
diff --git a/acestep/ui/gradio/events/results/batch_navigation_test.py b/acestep/ui/gradio/events/results/batch_navigation_test.py
new file mode 100644
index 00000000..66625d8e
--- /dev/null
+++ b/acestep/ui/gradio/events/results/batch_navigation_test.py
@@ -0,0 +1,105 @@
+"""Unit tests for batch_navigation module.
+
+Focuses on the navigate_to_next_batch guard logic that previously
+relied on a potentially stale ``total_batches`` Gradio state value.
+"""
+
+import unittest
+from unittest.mock import patch, MagicMock
+
+
+def _make_batch(audio_path="/tmp/audio.flac"):
+    """Return a minimal completed batch dict for testing."""
+    return {
+        "status": "completed",
+        "audio_paths": [audio_path],
+        "generation_info": "test info",
+        "seeds": "42",
+        "codes": "",
+        "scores": [""] * 8,
+        "allow_lm_batch": False,
+        "batch_size": 2,
+        "generation_params": {},
+        "lm_generated_metadata": None,
+        "extra_outputs": {},
+    }
+
+
+# Patch Gradio helpers that are unavailable in a headless test environment.
+@patch("acestep.ui.gradio.events.results.batch_navigation.gr")
+@patch("acestep.ui.gradio.events.results.batch_navigation.t", side_effect=lambda key, **kw: key)
+class NavigateToNextBatchTests(unittest.TestCase):
+    """Tests for navigate_to_next_batch."""
+
+    def _run_first_yield(self, gen):
+        """Advance the generator to its first yield and return the tuple."""
+        return next(gen)
+
+    def test_stale_total_batches_allows_navigation(self, _mock_t, mock_gr):
+        """Navigation should succeed when batch_queue has the next batch
+        even if total_batches state is stale (not yet incremented)."""
+        mock_gr.update = MagicMock(side_effect=lambda **kw: ("update", kw))
+        mock_gr.skip = MagicMock(return_value="skip")
+        mock_gr.Warning = MagicMock()
+
+        from acestep.ui.gradio.events.results.batch_navigation import navigate_to_next_batch
+
+        batch_queue = {0: _make_batch(), 1: _make_batch()}
+        # total_batches=1 is stale; actual queue has 2 entries.
+        gen = navigate_to_next_batch(
+            autogen_enabled=True,
+            current_batch_index=0,
+            total_batches=1,
+            batch_queue=batch_queue,
+        )
+        result = self._run_first_yield(gen)
+
+        # Should NOT have warned "at_last_batch".
+        mock_gr.Warning.assert_not_called()
+        # The 11th element (index 10) is the new batch index.
+        self.assertEqual(result[10], 1)
+
+    def test_no_next_batch_when_truly_last(self, _mock_t, mock_gr):
+        """Warning should fire when there really is no next batch."""
+        mock_gr.update = MagicMock(return_value="update")
+        mock_gr.Warning = MagicMock()
+
+        from acestep.ui.gradio.events.results.batch_navigation import navigate_to_next_batch
+
+        batch_queue = {0: _make_batch()}
+        gen = navigate_to_next_batch(
+            autogen_enabled=False,
+            current_batch_index=0,
+            total_batches=1,
+            batch_queue=batch_queue,
+        )
+        result = self._run_first_yield(gen)
+
+        mock_gr.Warning.assert_called_once()
+        # All 49 outputs should be gr.update() no-ops.
+        self.assertEqual(len(result), 49)
+
+    def test_batch_not_in_queue(self, _mock_t, mock_gr):
+        """Warning should fire when total_batches suggests a next batch
+        exists but the queue does not actually contain it."""
+        mock_gr.update = MagicMock(return_value="update")
+        mock_gr.Warning = MagicMock()
+
+        from acestep.ui.gradio.events.results.batch_navigation import navigate_to_next_batch
+
+        # total_batches=3 but queue only has batch 0.
+        batch_queue = {0: _make_batch()}
+        gen = navigate_to_next_batch(
+            autogen_enabled=False,
+            current_batch_index=0,
+            total_batches=3,
+            batch_queue=batch_queue,
+        )
+        result = self._run_first_yield(gen)
+
+        mock_gr.Warning.assert_called_once()
+        self.assertEqual(len(result), 49)
+
+
+if __name__ == "__main__":
+    unittest.main()