Add store/load support for code mode (#14259)

adds support for transferring state across code mode invocations.

codex-rs/core/tests/suite/code_mode.rs

@@ -524,3 +524,96 @@ structuredContent=null"
 
     Ok(())
 }
+#[tokio::test(flavor = "multi_thread", worker_threads = 2)]
+async fn code_mode_can_store_and_load_values_across_turns() -> Result<()> {
+    skip_if_no_network!(Ok(()));
+
+    let server = responses::start_mock_server().await;
+    let mut builder = test_codex().with_config(move |config| {
+        let _ = config.features.enable(Feature::CodeMode);
+    });
+    let test = builder.build(&server).await?;
+
+    responses::mount_sse_once(
+        &server,
+        sse(vec![
+            ev_response_created("resp-1"),
+            ev_custom_tool_call(
+                "call-1",
+                "code_mode",
+                r#"
+import { store } from "@openai/code_mode";
+
+store("nb", { title: "Notebook", items: [1, true, null] });
+add_content("stored");
+"#,
+            ),
+            ev_completed("resp-1"),
+        ]),
+    )
+    .await;
+    let first_follow_up = responses::mount_sse_once(
+        &server,
+        sse(vec![
+            ev_assistant_message("msg-1", "stored"),
+            ev_completed("resp-2"),
+        ]),
+    )
+    .await;
+
+    test.submit_turn("store value for later").await?;
+
+    let first_request = first_follow_up.single_request();
+    let (first_output, first_success) =
+        custom_tool_output_text_and_success(&first_request, "call-1");
+    assert_ne!(
+        first_success,
+        Some(false),
+        "code_mode store call failed unexpectedly: {first_output}"
+    );
+    assert_eq!(first_output, "stored");
+
+    responses::mount_sse_once(
+        &server,
+        sse(vec![
+            ev_response_created("resp-3"),
+            ev_custom_tool_call(
+                "call-2",
+                "code_mode",
+                r#"
+import { load } from "openai/code_mode";
+
+add_content(JSON.stringify(load("nb")));
+"#,
+            ),
+            ev_completed("resp-3"),
+        ]),
+    )
+    .await;
+    let second_follow_up = responses::mount_sse_once(
+        &server,
+        sse(vec![
+            ev_assistant_message("msg-2", "loaded"),
+            ev_completed("resp-4"),
+        ]),
+    )
+    .await;
+
+    test.submit_turn("load the stored value").await?;
+
+    let second_request = second_follow_up.single_request();
+    let (second_output, second_success) =
+        custom_tool_output_text_and_success(&second_request, "call-2");
+    assert_ne!(
+        second_success,
+        Some(false),
+        "code_mode load call failed unexpectedly: {second_output}"
+    );
+    let loaded: Value = serde_json::from_str(&second_output)?;
+    assert_eq!(
+        loaded,
+        serde_json::json!({ "title": "Notebook", "items": [1, true, null] })
+    );
+
+    Ok(())
+}