diff --git a/klausur-service/backend/grid_build_core.py b/klausur-service/backend/grid_build_core.py
index 954aef8..e268244 100644
--- a/klausur-service/backend/grid_build_core.py
+++ b/klausur-service/backend/grid_build_core.py
@@ -1407,10 +1407,14 @@ async def _build_grid_core(
             # Rule (a2): isolated non-alphanumeric symbols (graphic OCR artifacts)
             # Small images/icons next to words get OCR'd as ">", "<", "~", etc.
             # Remove word boxes that contain NO letters or digits.
+            # Exception: meaningful punctuation used in textbooks (=, ;, :, -, etc.)
+            _KEEP_SYMBOLS = {'=', '(=', '=)', ';', ':', '-', '–', '—', '/', '+',
+                             '•', '·', '(', ')', '&', '*', '→', '←', '↔'}
             for i, wb in enumerate(wbs):
                 t = (wb.get("text") or "").strip()
                 if t and not re.search(r'[a-zA-Z0-9äöüÄÖÜß]', t) and len(t) <= 2:
-                    to_remove.add(i)
+                    if t not in _KEEP_SYMBOLS:
+                        to_remove.add(i)
 
             # Rule (b) + (c): overlap and duplicate detection
             # Sort by x for pairwise comparison