diff --git a/codex-rs/core/tests/suite/rmcp_client.rs b/codex-rs/core/tests/suite/rmcp_client.rs
index e5bc6a34b6..443213095d 100644
--- a/codex-rs/core/tests/suite/rmcp_client.rs
+++ b/codex-rs/core/tests/suite/rmcp_client.rs
@@ -691,6 +691,68 @@ async fn stdio_server_round_trip() -> anyhow::Result<()> {
     Ok(())
 }
 
+#[tokio::test(flavor = "multi_thread", worker_threads = 2)]
+async fn turn_skips_pending_optional_mcp_without_cached_tools() -> anyhow::Result<()> {
+    skip_if_no_network!(Ok(()));
+
+    let server = responses::start_mock_server().await;
+    let response_mock = responses::mount_sse_once(
+        &server,
+        responses::sse(vec![
+            responses::ev_response_created("resp-1"),
+            responses::ev_assistant_message("msg-1", "done"),
+            responses::ev_completed("resp-1"),
+        ]),
+    )
+    .await;
+    let pending_mcp_listener = tokio::net::TcpListener::bind("127.0.0.1:0").await?;
+    let pending_mcp_url = format!("http://{}/mcp", pending_mcp_listener.local_addr()?);
+
+    let fixture = test_codex()
+        .with_config(move |config| {
+            insert_mcp_server(
+                config,
+                "pending_optional",
+                McpServerTransportConfig::StreamableHttp {
+                    url: pending_mcp_url,
+                    bearer_token_env_var: None,
+                    http_headers: None,
+                    env_http_headers: None,
+                },
+                TestMcpServerOptions::default(),
+            );
+        })
+        .build(&server)
+        .await?;
+
+    let (_pending_mcp_connection, _) =
+        tokio::time::timeout(Duration::from_secs(5), pending_mcp_listener.accept())
+            .await
+            .context("optional MCP startup should reach the pending server")??;
+    tokio::time::timeout(Duration::from_secs(5), fixture.submit_turn("hello"))
+        .await
+        .context("turn should not wait for pending optional MCP startup")??;
+
+    let request = response_mock.single_request();
+    let body = request.body_json();
+    let tools = body["tools"].as_array().expect("model request tools");
+    assert!(
+        tools.iter().all(|tool| {
+            tool.get("name")
+                .or_else(|| tool.get("type"))
+                .and_then(Value::as_str)
+                .is_none_or(|name| !name.starts_with("mcp__pending_optional"))
+        }),
+        "pending optional MCP tools should be omitted: {tools:?}"
+    );
+
+    tokio::time::timeout(Duration::from_secs(2), fixture.codex.shutdown_and_wait())
+        .await
+        .context("shutdown should cancel pending optional MCP startup")??;
+
+    Ok(())
+}
+
 #[tokio::test(flavor = "multi_thread", worker_threads = 2)]
 async fn shutdown_cancels_startup_prewarm_waiting_for_mcp_startup() -> anyhow::Result<()> {
     skip_if_no_network!(Ok(()));