feat(agent-chat): complete core workflow and strengthen auth rate limiting

backend/tests/integration/test_agent_chat_session_persistence.py

@@ -0,0 +1,20 @@
+from __future__ import annotations
+
+from decimal import Decimal
+
+from v1.agent_chat.service import aggregate_session_cost
+
+
+def test_aggregate_session_cost_sums_non_negative_values() -> None:
+    total = aggregate_session_cost([Decimal("0.010000"), Decimal("0.002500")])
+    assert total == Decimal("0.012500")
+
+
+def test_aggregate_session_cost_rejects_negative_value() -> None:
+    try:
+        aggregate_session_cost([Decimal("-0.010000")])
+        raised = False
+    except ValueError:
+        raised = True
+
+    assert raised is True