diff --git a/tests/e2e/test_proxy_auth_middleware.py b/tests/e2e/test_proxy_auth_middleware.py
index 3db86079..23047455 100644
--- a/tests/e2e/test_proxy_auth_middleware.py
+++ b/tests/e2e/test_proxy_auth_middleware.py
@@ -36,6 +36,25 @@ def main_module():
         return main
 
 
+@pytest.fixture(autouse=True)
+def _empty_user_table(main_module):
+    """Give every test an instance with no accounts yet.
+
+    Proxy provisioning keys off whether the instance already has an admin, so
+    two tests sharing a user table are really asserting the order they happened
+    to run in. The suite runs with xdist, where each worker gets its own
+    CONFIG_DIR, so that order changes whenever the test count does.
+    """
+
+    def _clear() -> None:
+        for user in main_module.user_db.list_users():
+            main_module.user_db.delete_user(user["id"])
+
+    _clear()
+    yield
+    _clear()
+
+
 class TestProxyAuthMiddleware:
     def test_skips_for_non_proxy_mode(self, main_module):
         with (
@@ -231,6 +250,92 @@ class TestProxyAuthMiddleware:
             assert db_user is not None
             assert db_user["username"] == username
 
+    def test_first_account_is_admin_and_later_ones_are_not(self, main_module):
+        """The bootstrap account is an admin; after that the default role decides."""
+        with (
+            patch.object(main_module, "get_auth_mode", return_value="proxy"),
+            patch.object(
+                main_module.app_config,
+                "get",
+                side_effect=_config_getter({"PROXY_AUTH_USER_HEADER": "X-Auth-User"}),
+            ),
+        ):
+            with main_module.app.test_request_context(
+                "/api/releases",
+                headers={"X-Auth-User": "first_proxy_user"},
+            ):
+                assert main_module.proxy_auth_middleware() is None
+                assert main_module.session.get("is_admin") is True
+
+            # The instance now has an admin, so nobody is at risk of being locked
+            # out and the next account follows PROXY_AUTH_DEFAULT_ROLE.
+            with main_module.app.test_request_context(
+                "/api/releases",
+                headers={"X-Auth-User": "second_proxy_user"},
+            ):
+                assert main_module.proxy_auth_middleware() is None
+                assert main_module.session.get("is_admin") is False
+
+    def test_default_role_admin_promotes_later_accounts(self, main_module):
+        main_module.user_db.create_user(
+            username="existing_admin",
+            role="admin",
+            auth_source="proxy",
+        )
+
+        with (
+            patch.object(main_module, "get_auth_mode", return_value="proxy"),
+            patch.object(
+                main_module.app_config,
+                "get",
+                side_effect=_config_getter(
+                    {
+                        "PROXY_AUTH_USER_HEADER": "X-Auth-User",
+                        "PROXY_AUTH_DEFAULT_ROLE": "admin",
+                    }
+                ),
+            ),
+            main_module.app.test_request_context(
+                "/api/releases",
+                headers={"X-Auth-User": "later_proxy_admin"},
+            ),
+        ):
+            assert main_module.proxy_auth_middleware() is None
+            assert main_module.session.get("is_admin") is True
+
+    def test_existing_user_keeps_its_stored_role(self, main_module):
+        main_module.user_db.create_user(
+            username="existing_admin",
+            role="admin",
+            auth_source="proxy",
+        )
+        main_module.user_db.create_user(
+            username="known_plain_user",
+            role="user",
+            auth_source="proxy",
+        )
+
+        with (
+            patch.object(main_module, "get_auth_mode", return_value="proxy"),
+            patch.object(
+                main_module.app_config,
+                "get",
+                side_effect=_config_getter(
+                    {
+                        "PROXY_AUTH_USER_HEADER": "X-Auth-User",
+                        "PROXY_AUTH_DEFAULT_ROLE": "admin",
+                    }
+                ),
+            ),
+            main_module.app.test_request_context(
+                "/api/releases",
+                headers={"X-Auth-User": "known_plain_user"},
+            ),
+        ):
+            assert main_module.proxy_auth_middleware() is None
+            # The stored role wins; the default only applies to new accounts.
+            assert main_module.session.get("is_admin") is False
+
     def test_returns_401_when_header_missing_on_protected_path(self, main_module):
         with (
             patch.object(main_module, "get_auth_mode", return_value="proxy"),