diff --git a/codex-rs/core/src/tools/tool_dispatch_trace_tests.rs b/codex-rs/core/src/tools/tool_dispatch_trace_tests.rs
index b025fa4367..dba0127dc6 100644
--- a/codex-rs/core/src/tools/tool_dispatch_trace_tests.rs
+++ b/codex-rs/core/src/tools/tool_dispatch_trace_tests.rs
@@ -273,6 +273,22 @@ async fn missing_code_mode_wait_traces_only_the_wait_tool_call() -> anyhow::Resu
     session.services.code_mode_service =
         crate::tools::code_mode::CodeModeService::new(Arc::clone(&provider));
     session.services.code_mode_session_provider = provider;
+    assert_eq!(
+        session
+            .services
+            .code_mode_service
+            .execute(ExecuteRequest {
+                tool_call_id: "setup-call".to_string(),
+                enabled_tools: Vec::new(),
+                source: String::new(),
+                yield_time_ms: None,
+                max_output_tokens: None,
+            })
+            .await
+            .err()
+            .as_deref(),
+        Some("execute is not supported by this test session")
+    );
     attach_test_trace(&mut session, &turn, temp.path())?;
 
     let registry = ToolRegistry::with_handler_for_test(Arc::new(CodeModeWaitHandler));
diff --git a/codex-rs/core/tests/suite/code_mode.rs b/codex-rs/core/tests/suite/code_mode.rs
index e1b02292ef..d5b065ce57 100644
--- a/codex-rs/core/tests/suite/code_mode.rs
+++ b/codex-rs/core/tests/suite/code_mode.rs
@@ -1866,7 +1866,7 @@ text("after terminate");
 }
 
 #[tokio::test(flavor = "multi_thread", worker_threads = 2)]
-async fn code_mode_wait_returns_error_for_unknown_session() -> Result<()> {
+async fn code_mode_wait_returns_error_without_a_session() -> Result<()> {
     skip_if_no_network!(Ok(()));
 
     let server = responses::start_mock_server().await;
@@ -1909,17 +1909,10 @@ async fn code_mode_wait_returns_error_for_unknown_session() -> Result<()> {
     assert_ne!(success, Some(true));
 
     let items = function_tool_output_items(&request, "call-1");
-    assert_eq!(items.len(), 2);
-    assert_regex_match(
-        concat!(
-            r"(?s)\A",
-            r"Script failed\nWall time \d+\.\d seconds\nOutput:\n\z"
-        ),
-        text_item(&items, /*index*/ 0),
-    );
+    assert_eq!(items.len(), 1);
     assert_eq!(
-        text_item(&items, /*index*/ 1),
-        "Script error:\nexec cell 999999 not found"
+        text_item(&items, /*index*/ 0),
+        "code mode session is unavailable"
     );
 
     Ok(())