diff --git a/codex-rs/core/src/codex_delegate.rs b/codex-rs/core/src/codex_delegate.rs
index 45319ed284..c060c4db16 100644
--- a/codex-rs/core/src/codex_delegate.rs
+++ b/codex-rs/core/src/codex_delegate.rs
@@ -178,7 +178,7 @@ pub(crate) async fn run_codex_thread_one_shot(
         models_manager,
         parent_session,
         parent_ctx,
-        None,
+        /*parent_trace*/ None,
         child_cancel.clone(),
         subagent_source,
         initial_history,
diff --git a/codex-rs/core/src/codex_delegate_tests.rs b/codex-rs/core/src/codex_delegate_tests.rs
index 174ec206b4..6add3212fa 100644
--- a/codex-rs/core/src/codex_delegate_tests.rs
+++ b/codex-rs/core/src/codex_delegate_tests.rs
@@ -588,9 +588,10 @@ async fn guardian_review_span_uses_parent_turn_trace_context() {
     let parent_trace = test_trace_context("00000000000000000000000000000011", "0000000000000022");
     turn.trace_id = Some("00000000000000000000000000000011".to_string());
     turn.trace_context = Some(parent_trace.clone());
-    let trace = crate::guardian::guardian_review_trace_for_test(Arc::new(turn), None)
-        .await
-        .expect("guardian review trace");
+    let trace =
+        crate::guardian::guardian_review_trace_for_test(Arc::new(turn), /*parent_trace*/ None)
+            .await
+            .expect("guardian review trace");
     let actual =
         codex_otel::context_from_w3c_trace_context(&trace).expect("actual guardian review trace");
     let expected =