diff --git a/cli/planoai/config_generator.py b/cli/planoai/config_generator.py
index 934df8be..f97df5fc 100644
--- a/cli/planoai/config_generator.py
+++ b/cli/planoai/config_generator.py
@@ -70,10 +70,16 @@ def migrate_inline_routing_preferences(config_yaml):
     errored, so existing v0.3.0 configs keep compiling. Any top-level
     preference already defined by the user is preserved as-is.
 
-    Also bumps ``version`` to ``v0.4.0`` when migration produced any entry,
-    so brightstaff's v0.4.0 gate for top-level ``routing_preferences``
-    accepts the rendered config.
+    Also bumps ``version`` to ``v0.4.0`` up front (when the config is
+    ``v0.3.0`` or older) so brightstaff's v0.4.0 gate for top-level
+    ``routing_preferences`` accepts the rendered config, including configs
+    that already declare top-level ``routing_preferences`` on a v0.3.0
+    version string.
     """
+    current_version = str(config_yaml.get("version", ""))
+    if _version_tuple(current_version) < (0, 4, 0):
+        config_yaml["version"] = "v0.4.0"
+
     model_providers = config_yaml.get("model_providers") or []
     if not model_providers:
         return
@@ -129,10 +135,6 @@ def migrate_inline_routing_preferences(config_yaml):
         merged.append(entry)
     config_yaml["routing_preferences"] = merged
 
-    current_version = str(config_yaml.get("version", ""))
-    if _version_tuple(current_version) < (0, 4, 0):
-        config_yaml["version"] = "v0.4.0"
-
     print(
         "WARNING: inline routing_preferences under model_providers is deprecated "
         "and has been auto-migrated to top-level routing_preferences. Update your "
diff --git a/cli/test/test_config_generator.py b/cli/test/test_config_generator.py
index bb56153f..3836ce53 100644
--- a/cli/test/test_config_generator.py
+++ b/cli/test/test_config_generator.py
@@ -672,7 +672,7 @@ model_providers:
     assert "wildcard" in str(excinfo.value).lower()
 
 
-def test_migration_noop_when_no_inline_preferences():
+def test_migration_bumps_version_even_without_inline_preferences():
     plano_config = """
 version: v0.3.0
 
@@ -689,4 +689,23 @@ model_providers:
     migrate_inline_routing_preferences(config_yaml)
 
     assert "routing_preferences" not in config_yaml
-    assert config_yaml["version"] == "v0.3.0"
+    assert config_yaml["version"] == "v0.4.0"
+
+
+def test_migration_does_not_downgrade_newer_versions():
+    plano_config = """
+version: v0.5.0
+
+listeners:
+  - type: model
+    name: model_listener
+    port: 12000
+
+model_providers:
+  - model: openai/gpt-4o
+    access_key: $OPENAI_API_KEY
+"""
+    config_yaml = yaml.safe_load(plano_config)
+    migrate_inline_routing_preferences(config_yaml)
+
+    assert config_yaml["version"] == "v0.5.0"