Verify native profile runtime behavior

internal/framework/llm/runtime_assembly_test.go

@@ -124,6 +124,46 @@ func TestNewRuntimeAllowsUnselectedPartialProfiles(t *testing.T) {
 	}
 }
 
+func TestNativeProfileInheritancePreservesControlsAndMergesProviderValues(t *testing.T) {
+	cfg, main := runtimeAssemblyFixture(t, "  proposal_profile: \"child profile\"\n", map[string]string{
+		"unrelated-name.yaml": `profiles:
+  "parent~/shared":
+    backend: offline
+    temperature: 0.4
+    top_p: 0.7
+    extra_params:
+      routing:
+        retained: from-parent
+        overridden: parent
+        cleared: remove-me
+  "child profile":
+    extends: "parent~/shared"
+    model: child-model
+    extra_params:
+      routing:
+        overridden: child
+        child_only: present
+        cleared: null
+`,
+	})
+	runtime, err := NewRuntime(context.Background(), cfg, main, &http.Client{Transport: rejectingTransport{}})
+	if err != nil {
+		t.Fatal(err)
+	}
+	profile := runtime.Profiles["proposal"]
+	target := profile.EffectiveModelParams
+	if profile.ProfileID != "child profile" || target.Model != "child-model" || target.Temperature != 0.4 || target.TopP != 0.7 {
+		t.Fatalf("inherited profile target = %+v", target)
+	}
+	routing, ok := target.ExtraParams["routing"].(map[string]any)
+	if !ok || routing["retained"] != "from-parent" || routing["overridden"] != "child" || routing["child_only"] != "present" {
+		t.Fatalf("recursively inherited provider values = %#v", target.ExtraParams)
+	}
+	if value, exists := routing["cleared"]; !exists || value != nil {
+		t.Fatalf("null did not replace the inherited provider value: %#v", routing)
+	}
+}
+
 func TestMissingSelectedProfileDirectoryIsOperatorInputError(t *testing.T) {
 	cfg, main := runtimeAssemblyFixture(t, "  proposal_profile: proposal\n", map[string]string{
 		"definitions.yml": "profiles:\n  proposal:\n    backend: offline\n    model: proposal-model\n",