diff --git a/tests/test_app_startup_contracts.py b/tests/test_app_startup_contracts.py
new file mode 100644
index 0000000..f1ef5f0
--- /dev/null
+++ b/tests/test_app_startup_contracts.py
@@ -0,0 +1,63 @@
+import ast
+from pathlib import Path
+
+
+ROOT = Path(__file__).resolve().parents[1]
+
+
+def _python_files_to_scan():
+    return [ROOT / "app.py", *sorted((ROOT / "routes").glob("*.py"))]
+
+
+def test_app_defines_and_runs_metadata_self_check():
+    app_source = (ROOT / "app.py").read_text(encoding="utf-8")
+
+    assert "EXPECTED_METADATA_TABLES" in app_source
+    assert "def verify_metadata_tables()" in app_source
+    assert "Base.metadata.tables.keys()" in app_source
+    assert "realtime_sales_monthly" in app_source
+    assert "verify_metadata_tables()" in app_source
+
+
+def test_app_defines_and_runs_duplicate_route_self_check():
+    app_source = (ROOT / "app.py").read_text(encoding="utf-8")
+
+    assert "def verify_unique_routes()" in app_source
+    assert "app.url_map.iter_rules()" in app_source
+    assert "frozenset(rule.methods - {'HEAD', 'OPTIONS'})" in app_source
+    assert "verify_unique_routes()" in app_source
+
+
+def test_literal_render_templates_exist():
+    missing = []
+
+    for path in _python_files_to_scan():
+        tree = ast.parse(path.read_text(encoding="utf-8"), filename=str(path))
+        for node in ast.walk(tree):
+            if not isinstance(node, ast.Call):
+                continue
+            func = node.func
+            if not isinstance(func, ast.Name) or func.id != "render_template":
+                continue
+            if not node.args or not isinstance(node.args[0], ast.Constant):
+                continue
+            template_name = node.args[0].value
+            if not isinstance(template_name, str):
+                continue
+
+            candidates = [
+                ROOT / "templates" / template_name,
+                ROOT / "web" / "templates" / template_name,
+            ]
+            if not any(candidate.exists() for candidate in candidates):
+                missing.append(f"{path.relative_to(ROOT)}: {template_name}")
+
+    assert missing == []
+
+
+def test_vendor_blueprint_uses_web_templates_absolute_folder():
+    source = (ROOT / "routes" / "vendor_routes.py").read_text(encoding="utf-8")
+
+    assert "os.path.dirname(os.path.dirname(os.path.abspath(__file__)))" in source
+    assert "os.path.join(_base_dir, 'web', 'templates')" in source
+    assert "template_folder=_template_folder" in source