diff --git a/internal/app/app_test.go b/internal/app/app_test.go
index 37e09de..b34fc32 100644
--- a/internal/app/app_test.go
+++ b/internal/app/app_test.go
@@ -125,7 +125,7 @@ func TestSelectEngineCodexDefault(t *testing.T) {
 	if err != nil {
 		t.Fatalf("selectEngine error: %v", err)
 	}
-	if command != "codex exec --model gpt-5.4-mini" {
+	if command != "codex exec --model gpt-5.6-luna" {
 		t.Fatalf("command = %q", command)
 	}
 }
diff --git a/internal/config/config.go b/internal/config/config.go
index e35596c..6245634 100644
--- a/internal/config/config.go
+++ b/internal/config/config.go
@@ -52,7 +52,7 @@ const defaultPromptPreset = "default"
 
 // DefaultEngineArgs provides default CLI arguments for known engines.
 var DefaultEngineArgs = map[string][]string{
-	"codex":        {"exec", "--model", "gpt-5.4-mini"},
+	"codex":        {"exec", "--model", "gpt-5.6-luna"},
 	"claude":       {"-p", "--model", "haiku", "--settings", "{\"attribution\":{\"commit\":\"\",\"pr\":\"\"}}", "--no-session-persistence"},
 	"cursor-agent": {"-p"},
 	"gemini":       {"-m", "gemini-2.5-flash", "-p", "{{prompt}}"},
diff --git a/scripts/release-check.sh b/scripts/release-check.sh
index 6dc08e0..2793159 100755
--- a/scripts/release-check.sh
+++ b/scripts/release-check.sh
@@ -57,7 +57,7 @@ EOC
 engine = "codex"
 
 [engines.codex]
-args = ["exec", "--model", "gpt-5.4-mini"]
+args = ["exec", "--model", "gpt-5.6-luna"]
 EOC
         ;;
       *)