diff --git a/internal/runtime/executor/codex_executor.go b/internal/runtime/executor/codex_executor.go
index 4297795c..c24e9589 100644
--- a/internal/runtime/executor/codex_executor.go
+++ b/internal/runtime/executor/codex_executor.go
@@ -203,6 +203,9 @@ func (e *CodexExecutor) ExecuteStream(ctx context.Context, auth *cliproxyauth.Au
 			body, _ = sjson.SetBytes(body, "reasoning.effort", "medium")
 		case "gpt-5-codex-mini-high":
 			body, _ = sjson.SetBytes(body, "reasoning.effort", "high")
+		default:
+			// For base "gpt-5-codex-mini", set reasoning.effort to "medium" by default
+			body, _ = sjson.SetBytes(body, "reasoning.effort", "medium")
 		}
 	}