diff --git a/src/openjd/model/v2023_09/_model.py b/src/openjd/model/v2023_09/_model.py
index 8d7ae71a..763fb053 100644
--- a/src/openjd/model/v2023_09/_model.py
+++ b/src/openjd/model/v2023_09/_model.py
@@ -758,15 +758,6 @@ def _requires_oneof(cls, values: dict[str, Any], info: ValidationInfo) -> dict[s
 
         on_enter = values.get("onEnter")
         on_exit = values.get("onExit")
-        # Base 2023-09 (§3.5) requires onEnter whenever a script is present;
-        # RFC 0008 relaxes this to "at least one action" when the
-        # WRAP_ACTIONS extension is declared. The strict base rule is only
-        # applied at template decode (context present) — job-instantiation
-        # re-validation has no parsing context, matching the other extension
-        # gates in this module.
-        if context is not None and "WRAP_ACTIONS" not in extensions:
-            if on_enter is None:
-                raise ValueError("onEnter is required.")
         if on_enter is None and on_exit is None:
             raise ValueError("Must define one of: onEnter or onExit")
         return values
diff --git a/test/openjd/model_v0/v2023_09/test_action.py b/test/openjd/model_v0/v2023_09/test_action.py
index d415f4a0..a8b86d3c 100644
--- a/test/openjd/model_v0/v2023_09/test_action.py
+++ b/test/openjd/model_v0/v2023_09/test_action.py
@@ -164,6 +164,7 @@ class TestEnvironmentActions:
         "data",
         (
             pytest.param({"onEnter": {"command": "foo"}}, id="has onEnter"),
+            pytest.param({"onExit": {"command": "foo"}}, id="has onExit"),
             # For making sure our pre-validator logic is correct
             pytest.param(
                 {
@@ -187,26 +188,35 @@ def test_parse_success(self, data: dict[str, Any]) -> None:
         # THEN
         # no exception was raised.
 
-    def test_parse_onexit_only_with_wrap_actions_extension(self) -> None:
-        # RFC 0008: with the WRAP_ACTIONS extension declared, an environment
-        # may define any single action without a standalone onEnter.
+    @pytest.mark.parametrize(
+        "supported_extensions",
+        (
+            pytest.param([], id="no extensions"),
+            pytest.param(["EXPR", "WRAP_ACTIONS"], id="EXPR and WRAP_ACTIONS"),
+        ),
+    )
+    def test_parse_onexit_only(self, supported_extensions: list[str]) -> None:
+        # An environment may define onExit without onEnter; either ordinary
+        # action alone satisfies the one-of requirement, with or without an
+        # extension being declared.
 
         # GIVEN
-        context = ModelParsingContext(supported_extensions=["EXPR", "WRAP_ACTIONS"])
+        context = ModelParsingContext(supported_extensions=supported_extensions)
 
         # WHEN
-        _parse_model(model=EnvironmentActions, obj={"onExit": {"command": "foo"}}, context=context)
+        actions = _parse_model(
+            model=EnvironmentActions, obj={"onExit": {"command": "foo"}}, context=context
+        )
 
         # THEN
-        # no exception was raised.
+        assert actions.onEnter is None
+        assert actions.onExit is not None
+        assert actions.onExit.command == "foo"
 
     @pytest.mark.parametrize(
         "data",
         (
             pytest.param({}, id="empty object"),
-            # §3.5: base 2023-09 requires onEnter whenever a script is
-            # present (the WRAP_ACTIONS extension relaxes this).
-            pytest.param({"onExit": {"command": "foo"}}, id="onExit only"),
             pytest.param({"onEnter": {"command": "foo"}, "onUnknown": "blah"}, id="unknown field"),
         ),
     )
@@ -219,3 +229,15 @@ def test_parse_fails(self, data: dict[str, Any]) -> None:
 
         # THEN
         assert len(excinfo.value.errors()) > 0
+
+    def test_parse_fails_no_actions_message(self) -> None:
+        # An actions object with neither ordinary action must be rejected with
+        # the one-of message; this is the only remaining constraint on which
+        # ordinary actions an environment defines.
+
+        # WHEN
+        with pytest.raises(ValidationError) as excinfo:
+            _parse_model(model=EnvironmentActions, obj={})
+
+        # THEN
+        assert "Must define one of: onEnter or onExit" in str(excinfo.value)
diff --git a/test/openjd/model_v0/v2023_09/test_environment_template.py b/test/openjd/model_v0/v2023_09/test_environment_template.py
index 864e1345..ed0ca37a 100644
--- a/test/openjd/model_v0/v2023_09/test_environment_template.py
+++ b/test/openjd/model_v0/v2023_09/test_environment_template.py
@@ -21,6 +21,16 @@ class TestEnvironmentTemplate:
                 {"specificationVersion": "environment-2023-09", "environment": ENVIRONMENT},
                 id="minimum required",
             ),
+            pytest.param(
+                {
+                    "specificationVersion": "environment-2023-09",
+                    "environment": {
+                        "name": "Foo",
+                        "script": {"actions": {"onExit": {"command": "foo"}}},
+                    },
+                },
+                id="script with onExit only",
+            ),
             pytest.param(
                 {
                     "specificationVersion": "environment-2023-09",
diff --git a/test/openjd/model_v0/v2023_09/test_job_template.py b/test/openjd/model_v0/v2023_09/test_job_template.py
index d58d4baa..8a96a89c 100644
--- a/test/openjd/model_v0/v2023_09/test_job_template.py
+++ b/test/openjd/model_v0/v2023_09/test_job_template.py
@@ -73,6 +73,20 @@ class TestJobTemplate:
                 },
                 id="with least environments",
             ),
+            pytest.param(
+                {
+                    "specificationVersion": "jobtemplate-2023-09",
+                    "name": "Foo",
+                    "steps": [STEP_TEMPLATE],
+                    "jobEnvironments": [
+                        {
+                            "name": "Foo",
+                            "script": {"actions": {"onExit": {"command": "foo"}}},
+                        }
+                    ],
+                },
+                id="with environment defining onExit only",
+            ),
             pytest.param(
                 {
                     "specificationVersion": "jobtemplate-2023-09",