Align API error envelopes

backend/tests/test_frontend_api_client_error_parser.py

@@ -0,0 +1,22 @@
+from __future__ import annotations
+
+from pathlib import Path
+
+
+ROOT = Path(__file__).resolve().parents[2]
+
+
+def test_frontend_api_client_accepts_top_level_error_contract() -> None:
+    client = (ROOT / "frontend" / "src" / "services" / "api" / "client.ts").read_text(encoding="utf-8")
+
+    assert 'typeof payload?.error === "string"' in client
+    assert "payload?.message" in client
+    assert "payload?.details" in client
+
+
+def test_frontend_api_client_remains_legacy_error_tolerant() -> None:
+    client = (ROOT / "frontend" / "src" / "services" / "api" / "client.ts").read_text(encoding="utf-8")
+
+    assert "legacyError?.code" in client
+    assert "legacyError?.message" in client
+    assert "legacyError?.details" in client