degrade optional workspace writes safely

tests/test_full_stack_contract.py

@@ -115,6 +115,25 @@ def test_invalid_schema_returns_structured_validation_error():
     assert "type='object'" in " ".join(result.warnings)
 
 
+def test_optional_workspace_write_is_skipped_without_a_workspace():
+    class NoWorkspaceContext:
+        @property
+        def workspace(self):
+            raise PermissionError("no workspace bound")
+
+    warnings = []
+    asyncio.run(
+        agent_module._write_workspace_output(
+            NoWorkspaceContext(),
+            "outputs/data-workflows/test.workflow.json",
+            {"ok": True},
+            warnings,
+        )
+    )
+
+    assert warnings == ["workspace write skipped: no workspace bound"]
+
+
 def test_workflow_spec_has_no_secret_fields():
     schema = {"type": "object", "properties": {"Name": {"type": "string"}}, "required": ["Name"]}
     profile = agent_module._profile_source_data("x.csv", "text/csv", b"Name\nAda\n")