diff --git a/backend/tests/test_llm_and_rag.py b/backend/tests/test_llm_and_rag.py
index 5c838b4..47f2691 100644
--- a/backend/tests/test_llm_and_rag.py
+++ b/backend/tests/test_llm_and_rag.py
@@ -5,8 +5,9 @@ import pytest
 from sqlalchemy import select
 
 from wisegrade.llm import DeepSeekClient, ModelError, ScoreResult, validate_score
-from wisegrade.models import KnowledgeChunk
+from wisegrade.models import AppSetting, KnowledgeChunk
 from wisegrade.rag import ingest, retrieve, split_pages
+from wisegrade.settings_store import model_config, save_model_config
 
 
 def fake_embed(texts):
@@ -53,3 +54,12 @@ def test_project_isolation_and_chunk_metadata(db):
     hits = retrieve(db, course_version_id=1, project_id=101, category="stage3", query="实验数据", embedder=fake_embed)
     assert hits and all(hit["project_id"] == 101 and hit["page"] == 3 for hit in hits)
     assert "秘密" not in str(hits)
+
+
+def test_model_key_is_encrypted_and_hidden(db):
+    result = save_model_config(db, {"model": "deepseek-flash", "api_key": "test-private-key"})
+    assert result["api_key_configured"] is True
+    assert "api_key" not in result
+    stored = db.get(AppSetting, "api_key")
+    assert b"test-private-key" not in stored.encrypted_value
+    assert model_config(db)["model"] == "deepseek-flash"