diff --git a/codex-rs/core/tests/suite/multi_agent_resume.rs b/codex-rs/core/tests/suite/multi_agent_resume.rs
index b263522d6f..d9de811116 100644
--- a/codex-rs/core/tests/suite/multi_agent_resume.rs
+++ b/codex-rs/core/tests/suite/multi_agent_resume.rs
@@ -149,7 +149,8 @@ fn configure_multi_agent_v2_with_role(
         .expect("test config should allow feature update");
     config.multi_agent_v2.subagent_developer_instructions =
         Some(SUBAGENT_DEVELOPER_INSTRUCTIONS.to_string());
-    config.multi_agent_v2.max_concurrent_threads_per_session = 3;
+    // Keep the root, worker, grandchild, and sibling resident until explicit shutdown.
+    config.multi_agent_v2.max_concurrent_threads_per_session = 4;
     let role_path = config.codex_home.join("durable-worker-role.toml");
     std::fs::write(
         &role_path,