diff --git a/klausur-service/backend/cv_vocab_pipeline.py b/klausur-service/backend/cv_vocab_pipeline.py
index 837fcc6..42e7314 100644
--- a/klausur-service/backend/cv_vocab_pipeline.py
+++ b/klausur-service/backend/cv_vocab_pipeline.py
@@ -4727,6 +4727,7 @@ def _ocr_cell_crop(
     }
 
     if cw <= 0 or ch <= 0:
+        logger.debug("_ocr_cell_crop R%02d_C%d: zero-size crop (%dx%d)", row_idx, col_idx, cw, ch)
         return empty_cell
 
     # --- Pixel-density check: skip truly empty cells ---
@@ -4735,6 +4736,8 @@ def _ocr_cell_crop(
         if crop.size > 0:
             dark_ratio = float(np.count_nonzero(crop < 180)) / crop.size
             if dark_ratio < 0.005:
+                logger.debug("_ocr_cell_crop R%02d_C%d: skip empty (dark_ratio=%.4f, crop=%dx%d)",
+                             row_idx, col_idx, dark_ratio, cw, ch)
                 return empty_cell
 
     # --- Prepare crop for OCR ---
@@ -4787,6 +4790,11 @@ def _ocr_cell_crop(
         y_tol = max(15, ch)
         text = _words_to_reading_order_text(words, y_tolerance_px=y_tol)
         avg_conf = round(sum(w['conf'] for w in words) / len(words), 1)
+        logger.debug("_ocr_cell_crop R%02d_C%d: OCR raw text=%r conf=%.1f nwords=%d crop=%dx%d psm=%s engine=%s",
+                     row_idx, col_idx, text, avg_conf, len(words), cw, ch, psm, engine_name)
+    else:
+        logger.debug("_ocr_cell_crop R%02d_C%d: OCR returned NO words (crop=%dx%d psm=%s engine=%s)",
+                     row_idx, col_idx, cw, ch, psm, engine_name)
 
     # --- PSM 7 fallback for still-empty Tesseract cells ---
     if not text.strip() and engine_name == "tesseract" and ocr_img is not None:
@@ -4808,8 +4816,11 @@ def _ocr_cell_crop(
 
     # --- Noise filter ---
     if text.strip():
+        pre_filter = text
         text = _clean_cell_text_lite(text)
         if not text:
+            logger.debug("_ocr_cell_crop R%02d_C%d: _clean_cell_text_lite REMOVED %r",
+                         row_idx, col_idx, pre_filter)
             avg_conf = 0.0
 
     result = dict(empty_cell)