diff --git a/tests/test_cache_manager.py b/tests/test_cache_manager.py
index 83bf708..425df33 100644
--- a/tests/test_cache_manager.py
+++ b/tests/test_cache_manager.py
@@ -1,4 +1,5 @@
 from pathlib import Path
+from flask import Flask, session
 
 
 ROOT = Path(__file__).resolve().parents[1]
@@ -144,6 +145,57 @@ def test_clear_daily_sales_cache_removes_shared_view_cache_files(tmp_path, monke
     assert not cache_file.exists()
 
 
+def test_sales_analysis_preview_context_cache_avoids_reloading_options(tmp_path, monkeypatch):
+    from routes import sales_routes
+
+    app = Flask(__name__)
+    app.secret_key = "test"
+
+    class FakeDatabaseManager:
+        engine = object()
+
+    class FakeInspector:
+        def has_table(self, table_name):
+            return table_name == "realtime_sales_monthly"
+
+    preview_calls = {"count": 0}
+
+    def fake_preview_options(_engine, _table_name):
+        preview_calls["count"] += 1
+        return {
+            "categories": ["美妝"],
+            "brands": ["品牌"],
+            "vendors": ["廠商"],
+            "activities": ["活動"],
+            "payments": ["付款"],
+            "months": ["2026-05"],
+        }
+
+    rendered = []
+
+    def fake_render_template(template_name, **context):
+        rendered.append((template_name, context))
+        return context
+
+    monkeypatch.setattr(sales_routes, "_SALES_ANALYSIS_PAGE_CACHE_DIR", tmp_path)
+    monkeypatch.setattr(sales_routes, "DatabaseManager", FakeDatabaseManager)
+    monkeypatch.setattr(sales_routes, "inspect", lambda _engine: FakeInspector())
+    monkeypatch.setattr(sales_routes, "_fetch_sales_data_range", lambda *_args: "2026/05/01 - 2026/05/13")
+    monkeypatch.setattr(sales_routes, "_preview_sales_filter_options", fake_preview_options)
+    monkeypatch.setattr(sales_routes, "render_template", fake_render_template)
+    sales_routes._SALES_ANALYSIS_RESULT_CACHE.clear()
+
+    for _ in range(2):
+        with app.test_request_context("/sales_analysis"):
+            session["logged_in"] = True
+            response = sales_routes.sales_analysis()
+            assert response["no_filter"] is True
+            assert response["all_categories"] == ["美妝"]
+
+    assert preview_calls["count"] == 1
+    assert len(rendered) == 2
+
+
 def test_cache_dicts_are_only_defined_in_cache_manager():
     assignments = []
     for path in [ROOT / "app.py", *ROOT.glob("routes/*.py"), *ROOT.glob("services/*.py")]: