test(agent): isolate env defaults

Author: Sakeeb91

tests/unit/test_agent_settings.py

@@ -1,9 +1,16 @@
 """Unit tests for agent settings defaults."""
 
+import pytest
+
 from app.config import AgentSettings
 
 
-def test_agent_settings_defaults() -> None:
+def test_agent_settings_defaults(monkeypatch: pytest.MonkeyPatch) -> None:
+    monkeypatch.delenv("AGENT_MODEL_BACKEND", raising=False)
+    monkeypatch.delenv("AGENT_USE_LEGACY_FALLBACK", raising=False)
+    monkeypatch.delenv("AGENT_INFERENCE_PROVIDER", raising=False)
+    monkeypatch.delenv("AGENT_INFERENCE_TIMEOUT", raising=False)
+
     settings = AgentSettings()
 
     assert settings.model_backend == "local"