make concurrent

tests/test_config.py

@@ -39,6 +39,17 @@ def test_defaults_explore_agent_to_luna_low() -> None:
     assert settings.explore_variant == "low"
 
 
+def test_defaults_to_two_concurrent_jobs() -> None:
+    settings = Settings(_env_file=None)  # type: ignore[call-arg]
+    assert settings.max_concurrent_jobs == 2
+
+
+@pytest.mark.parametrize("value", [0, 33])
+def test_rejects_unsafe_job_concurrency(value: int) -> None:
+    with pytest.raises(ValidationError):
+        Settings(_env_file=None, max_concurrent_jobs=value)  # type: ignore[call-arg]
+
+
 def test_reads_comma_delimited_install_scripts_from_environment(monkeypatch) -> None:
     monkeypatch.setenv("AGENTCI_INSTALL_SCRIPTS", "python,dotnet")