fix: harden request handling, pipeline containment, and startup boundaries

backend/tests/test_anthropic_llm.py

@@ -0,0 +1,13 @@
+"""Focused tests for Anthropic response parsing."""
+
+import pytest
+
+from app.adapters.anthropic.llm import _RecommendationObjectParser
+from app.ports.protocols import RecommenderOutputError
+
+
+def test_parser_missing_object_start_raises_typed_output_error() -> None:
+    parser = _RecommendationObjectParser()
+
+    with pytest.raises(RecommenderOutputError, match="object start position"):
+        parser._finish_object()