diff --git a/backend/app/api/enterprise.py b/backend/app/api/enterprise.py
index 86eef7afd..4c46a6fc3 100644
--- a/backend/app/api/enterprise.py
+++ b/backend/app/api/enterprise.py
@@ -1067,10 +1067,10 @@ async def get_notification_bar_public(
 @router.get("/system-settings/{key}")
 async def get_system_setting(
     key: str,
-    current_user: User = Depends(get_current_user),
+    current_user: User = Depends(require_role("platform_admin")),
     db: AsyncSession = Depends(get_db),
 ):
-    """Get a system setting by key."""
+    """Get a platform-level system setting (platform admin only)."""
     result = await db.execute(select(SystemSetting).where(SystemSetting.key == key))
     setting = result.scalar_one_or_none()
     if not setting:
@@ -1082,13 +1082,10 @@ async def get_system_setting(
 async def update_system_setting(
     key: str,
     data: SettingUpdate,
-    current_user: User = Depends(get_current_admin),
+    current_user: User = Depends(require_role("platform_admin")),
     db: AsyncSession = Depends(get_db),
 ):
-    """Create or update a system setting."""
-    # Platform-level settings (e.g. PUBLIC_BASE_URL) require platform_admin
-    if key == "platform" and not _is_platform_admin_user(current_user):
-        raise HTTPException(status_code=403, detail="Only platform admin can modify platform settings")
+    """Create or update a platform-level system setting (platform admin only)."""
     result = await db.execute(select(SystemSetting).where(SystemSetting.key == key))
     setting = result.scalar_one_or_none()
     if setting:
diff --git a/backend/tests/test_system_settings_api.py b/backend/tests/test_system_settings_api.py
new file mode 100644
index 000000000..36b29f189
--- /dev/null
+++ b/backend/tests/test_system_settings_api.py
@@ -0,0 +1,87 @@
+"""Authorization regression coverage for platform system settings."""
+
+import uuid
+from types import SimpleNamespace
+
+import httpx
+import pytest
+from fastapi import FastAPI
+
+from app.api.enterprise import router
+from app.core.security import get_current_user
+from app.database import get_db
+
+
+app = FastAPI()
+app.include_router(router, prefix="/api")
+
+
+class _Result:
+    def scalar_one_or_none(self):
+        return None
+
+
+class _Session:
+    async def execute(self, _statement: object) -> _Result:
+        return _Result()
+
+
+async def _get_db():
+    yield _Session()
+
+
+@pytest.fixture
+def client():
+    transport = httpx.ASGITransport(app=app)
+
+    async def _build():
+        return httpx.AsyncClient(transport=transport, base_url="http://test")
+
+    return _build
+
+
+@pytest.fixture(autouse=True)
+def clear_dependency_overrides():
+    yield
+    app.dependency_overrides.clear()
+
+
+@pytest.mark.asyncio
+@pytest.mark.parametrize("method", ["get", "put"])
+async def test_org_admin_cannot_read_or_modify_platform_system_settings(client, method: str) -> None:
+    app.dependency_overrides[get_current_user] = lambda: SimpleNamespace(
+        id=uuid.uuid4(),
+        role="org_admin",
+        identity=None,
+        tenant_id=uuid.uuid4(),
+        is_active=True,
+    )
+    app.dependency_overrides[get_db] = _get_db
+
+    async with await client() as ac:
+        if method == "get":
+            response = await ac.get("/api/enterprise/system-settings/system_email_platform")
+        else:
+            response = await ac.put(
+                "/api/enterprise/system-settings/system_email_platform",
+                json={"value": {"SYSTEM_SMTP_PASSWORD": "attacker-value"}},
+            )
+
+    assert response.status_code == 403
+
+
+@pytest.mark.asyncio
+async def test_member_cannot_read_platform_system_settings(client) -> None:
+    app.dependency_overrides[get_current_user] = lambda: SimpleNamespace(
+        id=uuid.uuid4(),
+        role="member",
+        identity=None,
+        tenant_id=uuid.uuid4(),
+        is_active=True,
+    )
+    app.dependency_overrides[get_db] = _get_db
+
+    async with await client() as ac:
+        response = await ac.get("/api/enterprise/system-settings/jina_api_key")
+
+    assert response.status_code == 403