diff --git a/backend/routers/media_assets.py b/backend/routers/media_assets.py
index 8b264df..4378131 100644
--- a/backend/routers/media_assets.py
+++ b/backend/routers/media_assets.py
@@ -103,6 +103,7 @@ _MAX_TAGS = 40
 _MAX_TAG_LEN = 48
 
 _MEDIA_ASSETS_TAGS_COLUMN: Optional[bool] = None
+_TRAINING_UNIT_EXERCISES_TABLE: Optional[bool] = None
 
 
 def _media_assets_tags_column_present(cur: Any) -> bool:
@@ -124,6 +125,24 @@ def _media_assets_tags_column_present(cur: Any) -> bool:
     return _MEDIA_ASSETS_TAGS_COLUMN
 
 
+def _training_unit_exercises_table_present(cur: Any) -> bool:
+    """True wenn planning-Migration (training_unit_exercises) im Schema liegt — sonst keine Einheiten-Links."""
+    global _TRAINING_UNIT_EXERCISES_TABLE
+    if _TRAINING_UNIT_EXERCISES_TABLE is not None:
+        return _TRAINING_UNIT_EXERCISES_TABLE
+    cur.execute(
+        """
+        SELECT 1
+          FROM information_schema.tables
+         WHERE table_schema = 'public'
+           AND table_name = 'training_unit_exercises'
+         LIMIT 1
+        """
+    )
+    _TRAINING_UNIT_EXERCISES_TABLE = cur.fetchone() is not None
+    return _TRAINING_UNIT_EXERCISES_TABLE
+
+
 def _normalize_media_tags(raw: Union[list[str], None]) -> list[str]:
     """PostgreSQL text[]; Einträge gekürzt und ohne Dubletten (case-insensitive)."""
     if raw is None:
@@ -173,7 +192,7 @@ def _usage_for_media_assets(cur: Any, asset_ids: list[int]) -> dict[int, dict[st
         title = (d.get("exercise_title") or "").strip() or f"Übung #{eid}"
         ex_by_asset[aid].append({"id": eid, "title": title})
     exercise_to_units: dict[int, list[dict]] = {}
-    if exercise_ids:
+    if exercise_ids and _training_unit_exercises_table_present(cur):
         cur.execute(
             """SELECT tue.exercise_id, tu.id AS unit_id, tu.planned_date,
                       COALESCE(tg.name, '') AS group_name
diff --git a/backend/version.py b/backend/version.py
index 04dc47d..317abc7 100644
--- a/backend/version.py
+++ b/backend/version.py
@@ -1,6 +1,6 @@
 # Shinkan Jinkendo Version Information
 
-APP_VERSION = "0.8.50"
+APP_VERSION = "0.8.51"
 BUILD_DATE = "2026-05-07"
 DB_SCHEMA_VERSION = "20260507046"
 
@@ -13,7 +13,7 @@ MODULE_VERSIONS = {
     "club_join_requests": "1.0.1",  # Depends(get_tenant_context)
     "admin_users": "1.0.0",  # GET /api/admin/users
     "platform_media_storage": "1.0.0",  # GET/PUT /api/admin/platform-media-storage (Superadmin-Pfad unter MEDIA_ROOT)
-    "media_assets": "1.5.0",  # tags TEXT[] + erweiterte Suche/Filter; usage Übungen+Einheiten; PATCH/Bulk tags; API media_kind club uploader
+    "media_assets": "1.5.1",  # usage: training_unit_exercises optional (Schema ohne planning-Tabelle)
     "groups": "0.1.0",
     "skills": "0.1.0",
     "methods": "0.1.0",
@@ -29,6 +29,13 @@ MODULE_VERSIONS = {
 }
 
 CHANGELOG = [
+    {
+        "version": "0.8.51",
+        "date": "2026-05-07",
+        "changes": [
+            "Medienbibliothek GET: Verknüpfung zu Trainingseinheiten nur wenn Tabelle training_unit_exercises existiert (ältere/kaputte Schemas → keine 500, Einheiten-Liste leer)",
+        ],
+    },
     {
         "version": "0.8.50",
         "date": "2026-05-07",