[app-server] Add a method to list experimental features. (#10721)

- [x] Add a method to list experimental features.

codex-rs/app-server/tests/suite/v2/experimental_feature_list.rs

@@ -0,0 +1,66 @@
+use std::time::Duration;
+
+use anyhow::Result;
+use app_test_support::McpProcess;
+use app_test_support::to_response;
+use codex_app_server_protocol::ExperimentalFeature;
+use codex_app_server_protocol::ExperimentalFeatureListParams;
+use codex_app_server_protocol::ExperimentalFeatureListResponse;
+use codex_app_server_protocol::JSONRPCResponse;
+use codex_app_server_protocol::RequestId;
+use codex_core::features::FEATURES;
+use codex_core::features::Stage;
+use pretty_assertions::assert_eq;
+use tempfile::TempDir;
+use tokio::time::timeout;
+
+const DEFAULT_TIMEOUT: Duration = Duration::from_secs(10);
+
+#[tokio::test]
+async fn experimental_feature_list_returns_experimental_feature_metadata() -> Result<()> {
+    let codex_home = TempDir::new()?;
+    let mut mcp = McpProcess::new(codex_home.path()).await?;
+
+    timeout(DEFAULT_TIMEOUT, mcp.initialize()).await??;
+
+    let request_id = mcp
+        .send_experimental_feature_list_request(ExperimentalFeatureListParams::default())
+        .await?;
+
+    let response: JSONRPCResponse = timeout(
+        DEFAULT_TIMEOUT,
+        mcp.read_stream_until_response_message(RequestId::Integer(request_id)),
+    )
+    .await??;
+
+    let actual = to_response::<ExperimentalFeatureListResponse>(response)?;
+    let expected_data = FEATURES
+        .iter()
+        .filter_map(|spec| {
+            let Stage::Experimental {
+                name,
+                menu_description,
+                announcement,
+            } = spec.stage
+            else {
+                return None;
+            };
+
+            Some(ExperimentalFeature {
+                flag_name: spec.key.to_string(),
+                display_name: name.to_string(),
+                description: menu_description.to_string(),
+                announcement: announcement.to_string(),
+                enabled: spec.default_enabled,
+                default_enabled: spec.default_enabled,
+            })
+        })
+        .collect::<Vec<_>>();
+    let expected = ExperimentalFeatureListResponse {
+        data: expected_data,
+        next_cursor: None,
+    };
+
+    assert_eq!(actual, expected);
+    Ok(())
+}

codex-rs/app-server/tests/suite/v2/mod.rs

@@ -6,6 +6,7 @@ mod compaction;
 mod config_rpc;
 mod dynamic_tools;
 mod experimental_api;
+mod experimental_feature_list;
 mod initialize;
 mod model_list;
 mod output_schema;