diff --git a/llm-api/plan_session_router.py b/llm-api/plan_session_router.py
index ddcfee6..67b1e21 100644
--- a/llm-api/plan_session_router.py
+++ b/llm-api/plan_session_router.py
@@ -1,8 +1,8 @@
 # -*- coding: utf-8 -*-
 """
-plan_session_router.py – v0.1.0 (WP-15)
+plan_session_router.py – v0.2.0 (WP-15)
 
-CRUD-Minimum für Plan-Sessions (POST/GET).
+CRUD-Minimum für Plan-Sessions (POST/GET) mit Referenz-Validierung.
 Kompatibel zum Qdrant-Client-Stil der bestehenden Router.
 """
 from fastapi import APIRouter, HTTPException
@@ -21,6 +21,7 @@ router = APIRouter(tags=["plan_sessions"])
 # Konfiguration
 # -----------------
 PLAN_SESSION_COLLECTION = os.getenv("PLAN_SESSION_COLLECTION", "plan_sessions")
+PLAN_COLLECTION = os.getenv("PLAN_COLLECTION", "plans")
 
 # -----------------
 # Modelle
@@ -86,6 +87,10 @@ def _get_by_field(collection: str, key: str, value: Any) -> Optional[Dict[str, A
 @router.post("/plan_sessions", response_model=PlanSession)
 def create_plan_session(s: PlanSession):
     _ensure_collection(PLAN_SESSION_COLLECTION)
+    # Referenz auf Plan prüfen
+    if not _get_by_field(PLAN_COLLECTION, "id", s.plan_id):
+        raise HTTPException(status_code=422, detail=f"Unknown plan_id: {s.plan_id}")
+
     # Normalisieren
     s.used_equipment = _norm_list(s.used_equipment)
     payload = s.model_dump()