diff --git a/codex-rs/exec/src/lib.rs b/codex-rs/exec/src/lib.rs
index d27cec1f57..6d1c4e5854 100644
--- a/codex-rs/exec/src/lib.rs
+++ b/codex-rs/exec/src/lib.rs
@@ -335,6 +335,7 @@ pub async fn run_main(cli: Cli, arg0_paths: Arg0DispatchPaths) -> anyhow::Result
     // Load configuration and determine approval policy
     let overrides = ConfigOverrides {
         model,
+        model_reasoning_effort: None,
         review_model: None,
         config_profile,
         // Default to never ask for approvals in headless mode. Feature flags can override.