[connectors] Support connectors part 1 - App server & MCP (#9667)

In order to make Codex work with connectors, we add a built-in gateway
MCP that acts as a transparent proxy between the client and the
connectors. The gateway MCP collects actions that are accessible to the
user and sends them down to the user, when a connector action is chosen
to be called, the client invokes the action through the gateway MCP as
well.

 - [x] Add the system built-in gateway MCP to list and run connectors.
 - [x] Add the app server methods and protocol

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

@@ -0,0 +1,381 @@
+use std::borrow::Cow;
+use std::sync::Arc;
+use std::time::Duration;
+
+use anyhow::Result;
+use app_test_support::ChatGptAuthFixture;
+use app_test_support::McpProcess;
+use app_test_support::to_response;
+use app_test_support::write_chatgpt_auth;
+use axum::Json;
+use axum::Router;
+use axum::extract::State;
+use axum::http::HeaderMap;
+use axum::http::StatusCode;
+use axum::http::header::AUTHORIZATION;
+use axum::routing::post;
+use codex_app_server_protocol::AppInfo;
+use codex_app_server_protocol::AppsListParams;
+use codex_app_server_protocol::AppsListResponse;
+use codex_app_server_protocol::JSONRPCResponse;
+use codex_app_server_protocol::RequestId;
+use codex_core::auth::AuthCredentialsStoreMode;
+use codex_core::connectors::ConnectorInfo;
+use pretty_assertions::assert_eq;
+use rmcp::handler::server::ServerHandler;
+use rmcp::model::JsonObject;
+use rmcp::model::ListToolsResult;
+use rmcp::model::Meta;
+use rmcp::model::ServerCapabilities;
+use rmcp::model::ServerInfo;
+use rmcp::model::Tool;
+use rmcp::model::ToolAnnotations;
+use rmcp::transport::StreamableHttpServerConfig;
+use rmcp::transport::StreamableHttpService;
+use rmcp::transport::streamable_http_server::session::local::LocalSessionManager;
+use serde_json::json;
+use tempfile::TempDir;
+use tokio::net::TcpListener;
+use tokio::task::JoinHandle;
+use tokio::time::timeout;
+
+const DEFAULT_TIMEOUT: Duration = Duration::from_secs(10);
+
+#[tokio::test]
+async fn list_apps_returns_empty_when_connectors_disabled() -> 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_apps_list_request(AppsListParams {
+            limit: Some(50),
+            cursor: None,
+        })
+        .await?;
+
+    let response: JSONRPCResponse = timeout(
+        DEFAULT_TIMEOUT,
+        mcp.read_stream_until_response_message(RequestId::Integer(request_id)),
+    )
+    .await??;
+
+    let AppsListResponse { data, next_cursor } = to_response(response)?;
+
+    assert!(data.is_empty());
+    assert!(next_cursor.is_none());
+    Ok(())
+}
+
+#[tokio::test]
+async fn list_apps_returns_connectors_with_accessible_flags() -> Result<()> {
+    let connectors = vec![
+        ConnectorInfo {
+            connector_id: "alpha".to_string(),
+            connector_name: "Alpha".to_string(),
+            connector_description: Some("Alpha connector".to_string()),
+            logo_url: Some("https://example.com/alpha.png".to_string()),
+            install_url: None,
+            is_accessible: false,
+        },
+        ConnectorInfo {
+            connector_id: "beta".to_string(),
+            connector_name: "beta".to_string(),
+            connector_description: None,
+            logo_url: None,
+            install_url: None,
+            is_accessible: false,
+        },
+    ];
+
+    let tools = vec![connector_tool("beta", "Beta App")?];
+    let (server_url, server_handle) = start_apps_server(connectors.clone(), tools).await?;
+
+    let codex_home = TempDir::new()?;
+    write_connectors_config(codex_home.path(), &server_url)?;
+    write_chatgpt_auth(
+        codex_home.path(),
+        ChatGptAuthFixture::new("chatgpt-token")
+            .account_id("account-123")
+            .chatgpt_user_id("user-123")
+            .chatgpt_account_id("account-123"),
+        AuthCredentialsStoreMode::File,
+    )?;
+
+    let mut mcp = McpProcess::new(codex_home.path()).await?;
+    timeout(DEFAULT_TIMEOUT, mcp.initialize()).await??;
+
+    let request_id = mcp
+        .send_apps_list_request(AppsListParams {
+            limit: None,
+            cursor: None,
+        })
+        .await?;
+
+    let response: JSONRPCResponse = timeout(
+        DEFAULT_TIMEOUT,
+        mcp.read_stream_until_response_message(RequestId::Integer(request_id)),
+    )
+    .await??;
+
+    let AppsListResponse { data, next_cursor } = to_response(response)?;
+
+    let expected = vec![
+        AppInfo {
+            id: "beta".to_string(),
+            name: "Beta App".to_string(),
+            description: None,
+            logo_url: None,
+            install_url: Some("https://chatgpt.com/apps/beta/beta".to_string()),
+            is_accessible: true,
+        },
+        AppInfo {
+            id: "alpha".to_string(),
+            name: "Alpha".to_string(),
+            description: Some("Alpha connector".to_string()),
+            logo_url: Some("https://example.com/alpha.png".to_string()),
+            install_url: Some("https://chatgpt.com/apps/alpha/alpha".to_string()),
+            is_accessible: false,
+        },
+    ];
+
+    assert_eq!(data, expected);
+    assert!(next_cursor.is_none());
+
+    server_handle.abort();
+    Ok(())
+}
+
+#[tokio::test]
+async fn list_apps_paginates_results() -> Result<()> {
+    let connectors = vec![
+        ConnectorInfo {
+            connector_id: "alpha".to_string(),
+            connector_name: "Alpha".to_string(),
+            connector_description: Some("Alpha connector".to_string()),
+            logo_url: None,
+            install_url: None,
+            is_accessible: false,
+        },
+        ConnectorInfo {
+            connector_id: "beta".to_string(),
+            connector_name: "beta".to_string(),
+            connector_description: None,
+            logo_url: None,
+            install_url: None,
+            is_accessible: false,
+        },
+    ];
+
+    let tools = vec![connector_tool("beta", "Beta App")?];
+    let (server_url, server_handle) = start_apps_server(connectors.clone(), tools).await?;
+
+    let codex_home = TempDir::new()?;
+    write_connectors_config(codex_home.path(), &server_url)?;
+    write_chatgpt_auth(
+        codex_home.path(),
+        ChatGptAuthFixture::new("chatgpt-token")
+            .account_id("account-123")
+            .chatgpt_user_id("user-123")
+            .chatgpt_account_id("account-123"),
+        AuthCredentialsStoreMode::File,
+    )?;
+
+    let mut mcp = McpProcess::new(codex_home.path()).await?;
+    timeout(DEFAULT_TIMEOUT, mcp.initialize()).await??;
+
+    let first_request = mcp
+        .send_apps_list_request(AppsListParams {
+            limit: Some(1),
+            cursor: None,
+        })
+        .await?;
+    let first_response: JSONRPCResponse = timeout(
+        DEFAULT_TIMEOUT,
+        mcp.read_stream_until_response_message(RequestId::Integer(first_request)),
+    )
+    .await??;
+    let AppsListResponse {
+        data: first_page,
+        next_cursor: first_cursor,
+    } = to_response(first_response)?;
+
+    let expected_first = vec![AppInfo {
+        id: "beta".to_string(),
+        name: "Beta App".to_string(),
+        description: None,
+        logo_url: None,
+        install_url: Some("https://chatgpt.com/apps/beta/beta".to_string()),
+        is_accessible: true,
+    }];
+
+    assert_eq!(first_page, expected_first);
+    let next_cursor = first_cursor.ok_or_else(|| anyhow::anyhow!("missing cursor"))?;
+
+    let second_request = mcp
+        .send_apps_list_request(AppsListParams {
+            limit: Some(1),
+            cursor: Some(next_cursor),
+        })
+        .await?;
+    let second_response: JSONRPCResponse = timeout(
+        DEFAULT_TIMEOUT,
+        mcp.read_stream_until_response_message(RequestId::Integer(second_request)),
+    )
+    .await??;
+    let AppsListResponse {
+        data: second_page,
+        next_cursor: second_cursor,
+    } = to_response(second_response)?;
+
+    let expected_second = vec![AppInfo {
+        id: "alpha".to_string(),
+        name: "Alpha".to_string(),
+        description: Some("Alpha connector".to_string()),
+        logo_url: None,
+        install_url: Some("https://chatgpt.com/apps/alpha/alpha".to_string()),
+        is_accessible: false,
+    }];
+
+    assert_eq!(second_page, expected_second);
+    assert!(second_cursor.is_none());
+
+    server_handle.abort();
+    Ok(())
+}
+
+#[derive(Clone)]
+struct AppsServerState {
+    expected_bearer: String,
+    expected_account_id: String,
+    response: serde_json::Value,
+}
+
+#[derive(Clone)]
+struct AppListMcpServer {
+    tools: Arc<Vec<Tool>>,
+}
+
+impl AppListMcpServer {
+    fn new(tools: Arc<Vec<Tool>>) -> Self {
+        Self { tools }
+    }
+}
+
+impl ServerHandler for AppListMcpServer {
+    fn get_info(&self) -> ServerInfo {
+        ServerInfo {
+            capabilities: ServerCapabilities::builder().enable_tools().build(),
+            ..ServerInfo::default()
+        }
+    }
+
+    fn list_tools(
+        &self,
+        _request: Option<rmcp::model::PaginatedRequestParam>,
+        _context: rmcp::service::RequestContext<rmcp::service::RoleServer>,
+    ) -> impl std::future::Future<Output = Result<ListToolsResult, rmcp::ErrorData>> + Send + '_
+    {
+        let tools = self.tools.clone();
+        async move {
+            Ok(ListToolsResult {
+                tools: (*tools).clone(),
+                next_cursor: None,
+                meta: None,
+            })
+        }
+    }
+}
+
+async fn start_apps_server(
+    connectors: Vec<ConnectorInfo>,
+    tools: Vec<Tool>,
+) -> Result<(String, JoinHandle<()>)> {
+    let state = AppsServerState {
+        expected_bearer: "Bearer chatgpt-token".to_string(),
+        expected_account_id: "account-123".to_string(),
+        response: json!({ "connectors": connectors }),
+    };
+    let state = Arc::new(state);
+    let tools = Arc::new(tools);
+
+    let listener = TcpListener::bind("127.0.0.1:0").await?;
+    let addr = listener.local_addr()?;
+
+    let mcp_service = StreamableHttpService::new(
+        {
+            let tools = tools.clone();
+            move || Ok(AppListMcpServer::new(tools.clone()))
+        },
+        Arc::new(LocalSessionManager::default()),
+        StreamableHttpServerConfig::default(),
+    );
+
+    let router = Router::new()
+        .route("/aip/connectors/list_accessible", post(list_connectors))
+        .with_state(state)
+        .nest_service("/api/codex/apps", mcp_service);
+
+    let handle = tokio::spawn(async move {
+        let _ = axum::serve(listener, router).await;
+    });
+
+    Ok((format!("http://{addr}"), handle))
+}
+
+async fn list_connectors(
+    State(state): State<Arc<AppsServerState>>,
+    headers: HeaderMap,
+) -> Result<impl axum::response::IntoResponse, StatusCode> {
+    let bearer_ok = headers
+        .get(AUTHORIZATION)
+        .and_then(|value| value.to_str().ok())
+        .is_some_and(|value| value == state.expected_bearer);
+    let account_ok = headers
+        .get("chatgpt-account-id")
+        .and_then(|value| value.to_str().ok())
+        .is_some_and(|value| value == state.expected_account_id);
+
+    if bearer_ok && account_ok {
+        Ok(Json(state.response.clone()))
+    } else {
+        Err(StatusCode::UNAUTHORIZED)
+    }
+}
+
+fn connector_tool(connector_id: &str, connector_name: &str) -> Result<Tool> {
+    let schema: JsonObject = serde_json::from_value(json!({
+        "type": "object",
+        "additionalProperties": false
+    }))?;
+    let mut tool = Tool::new(
+        Cow::Owned(format!("connector_{connector_id}")),
+        Cow::Borrowed("Connector test tool"),
+        Arc::new(schema),
+    );
+    tool.annotations = Some(ToolAnnotations::new().read_only(true));
+
+    let mut meta = Meta::new();
+    meta.0
+        .insert("connector_id".to_string(), json!(connector_id));
+    meta.0
+        .insert("connector_name".to_string(), json!(connector_name));
+    tool.meta = Some(meta);
+    Ok(tool)
+}
+
+fn write_connectors_config(codex_home: &std::path::Path, base_url: &str) -> std::io::Result<()> {
+    let config_toml = codex_home.join("config.toml");
+    std::fs::write(
+        config_toml,
+        format!(
+            r#"
+chatgpt_base_url = "{base_url}"
+
+[features]
+connectors = true
+"#
+        ),
+    )
+}

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

@@ -1,5 +1,6 @@
 mod account;
 mod analytics;
+mod app_list;
 mod collaboration_mode_list;
 mod config_rpc;
 mod initialize;