diff --git a/backend/tests/test_ajax_contracts.py b/backend/tests/test_ajax_contracts.py
new file mode 100644
index 0000000..6e93761
--- /dev/null
+++ b/backend/tests/test_ajax_contracts.py
@@ -0,0 +1,46 @@
+"""Contract tests for AJAX endpoints used by the Next.js frontend."""
+import pytest
+
+from autometabuilder.web.server import app
+
+
+@pytest.fixture
+def client():
+    with app.test_client() as client:
+        yield client
+
+
+def test_workflow_graph_contract(client):
+    response = client.get("/api/workflow/graph")
+    assert response.status_code == 200
+    payload = response.get_json()
+    assert payload is not None, "workflow graph response should be JSON"
+    assert isinstance(payload.get("nodes"), list)
+    assert isinstance(payload.get("edges"), list)
+    counts = payload.get("count", {})
+    assert counts.get("nodes", 0) >= 1
+    assert counts.get("edges", 0) >= 0
+
+
+def test_workflow_plugins_contract(client):
+    response = client.get("/api/workflow/plugins")
+    assert response.status_code == 200
+    payload = response.get_json()
+    assert isinstance(payload, dict)
+    plugins = payload.get("plugins", {})
+    assert isinstance(plugins, dict)
+    assert "core.load_context" in plugins
+
+
+def test_navigation_and_translation_contract(client):
+    nav_response = client.get("/api/navigation")
+    assert nav_response.status_code == 200
+    nav_payload = nav_response.get_json()
+    assert isinstance(nav_payload, dict)
+    assert isinstance(nav_payload.get("items"), list)
+    trans_response = client.get("/api/translation-options")
+    assert trans_response.status_code == 200
+    trans_payload = trans_response.get_json()
+    assert isinstance(trans_payload, dict)
+    translations = trans_payload.get("translations", {})
+    assert "en" in translations