diff --git a/backend/app/services/whisper_service.py b/backend/app/services/whisper_service.py
index 418a6d5..017b08d 100644
--- a/backend/app/services/whisper_service.py
+++ b/backend/app/services/whisper_service.py
@@ -241,8 +241,21 @@ class WhisperService:
                 refined["original_pause_point"] = original  # Preserve for debugging
 
                 if warning:
-                    warnings.append(f"Cue {placement['ad_cue_index']}: {warning}")
-                    logger.warning(f"Pause point refinement warning for cue {placement['ad_cue_index']}: {warning}")
+                    # Special handling for first AD cue: if no sentence break found,
+                    # insert at the very beginning of the video to avoid mid-sentence insertion
+                    if placement["ad_cue_index"] == 0:
+                        refined["pause_point"] = 0.0
+                        warnings.append(
+                            f"Cue 0: No sentence break found within search window of {original:.2f}s, "
+                            "inserting AD at video start (0.0s)"
+                        )
+                        logger.info(
+                            f"First AD cue: No sentence break found near {original:.2f}s, "
+                            "using video start (0.0s) to avoid mid-sentence insertion"
+                        )
+                    else:
+                        warnings.append(f"Cue {placement['ad_cue_index']}: {warning}")
+                        logger.warning(f"Pause point refinement warning for cue {placement['ad_cue_index']}: {warning}")
                 elif abs(snapped - original) > 0.1:
                     logger.info(
                         f"Refined pause point for cue {placement['ad_cue_index']}: "