fix: separate codex mcp into codex mcp-server and codex app-server (#4471)
This is a very large PR with some non-backwards-compatible changes. Historically, `codex mcp` (or `codex mcp serve`) started a JSON-RPC-ish server that had two overlapping responsibilities: - Running an MCP server, providing some basic tool calls. - Running the app server used to power experiences such as the VS Code extension. This PR aims to separate these into distinct concepts: - `codex mcp-server` for the MCP server - `codex app-server` for the "application server" Note `codex mcp` still exists because it already has its own subcommands for MCP management (`list`, `add`, etc.) The MCP logic continues to live in `codex-rs/mcp-server` whereas the refactored app server logic is in the new `codex-rs/app-server` folder. Note that most of the existing integration tests in `codex-rs/mcp-server/tests/suite` were actually for the app server, so all the tests have been moved with the exception of `codex-rs/mcp-server/tests/suite/mod.rs`. Because this is already a large diff, I tried not to change more than I had to, so `codex-rs/app-server/tests/common/mcp_process.rs` still uses the name `McpProcess` for now, but I will do some mechanical renamings to things like `AppServer` in subsequent PRs. While `mcp-server` and `app-server` share some overlapping functionality (like reading streams of JSONL and dispatching based on message types) and some differences (completely different message types), I ended up doing a bit of copypasta between the two crates, as both have somewhat similar `message_processor.rs` and `outgoing_message.rs` files for now, though I expect them to diverge more in the near future. One material change is that of the initialize handshake for `codex app-server`, as we no longer use the MCP types for that handshake. Instead, we update `codex-rs/protocol/src/mcp_protocol.rs` to add an `Initialize` variant to `ClientRequest`, which takes the `ClientInfo` object we need to update the `USER_AGENT_SUFFIX` in `codex-rs/app-server/src/message_processor.rs`. One other material change is in `codex-rs/app-server/src/codex_message_processor.rs` where I eliminated a use of the `send_event_as_notification()` method I am generally trying to deprecate (because it blindly maps an `EventMsg` into a `JSONNotification`) in favor of `send_server_notification()`, which takes a `ServerNotification`, as that is intended to be a custom enum of all notification types supported by the app server. So to make this update, I had to introduce a new variant of `ServerNotification`, `SessionConfigured`, which is a non-backwards compatible change with the old `codex mcp`, and clients will have to be updated after the next release that contains this PR. Note that `codex-rs/app-server/tests/suite/list_resume.rs` also had to be update to reflect this change. I introduced `codex-rs/utils/json-to-toml/src/lib.rs` as a small utility crate to avoid some of the copying between `mcp-server` and `app-server`.
This commit is contained in:
Michael Bolin
GitHub
133
codex-rs/app-server/src/message_processor.rs
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133
codex-rs/app-server/src/message_processor.rs
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use std::path::PathBuf;
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use crate::codex_message_processor::CodexMessageProcessor;
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use crate::error_code::INVALID_REQUEST_ERROR_CODE;
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use crate::outgoing_message::OutgoingMessageSender;
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use codex_protocol::mcp_protocol::ClientInfo;
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use codex_protocol::mcp_protocol::ClientRequest;
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use codex_protocol::mcp_protocol::InitializeResponse;
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use codex_core::AuthManager;
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use codex_core::ConversationManager;
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use codex_core::config::Config;
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use codex_core::default_client::USER_AGENT_SUFFIX;
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use codex_core::default_client::get_codex_user_agent;
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use mcp_types::JSONRPCError;
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use mcp_types::JSONRPCErrorError;
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use mcp_types::JSONRPCNotification;
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use mcp_types::JSONRPCRequest;
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use mcp_types::JSONRPCResponse;
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use std::sync::Arc;
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pub(crate) struct MessageProcessor {
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outgoing: Arc<OutgoingMessageSender>,
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codex_message_processor: CodexMessageProcessor,
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initialized: bool,
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}
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impl MessageProcessor {
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/// Create a new `MessageProcessor`, retaining a handle to the outgoing
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/// `Sender` so handlers can enqueue messages to be written to stdout.
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pub(crate) fn new(
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outgoing: OutgoingMessageSender,
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codex_linux_sandbox_exe: Option<PathBuf>,
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config: Arc<Config>,
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) -> Self {
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let outgoing = Arc::new(outgoing);
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let auth_manager = AuthManager::shared(config.codex_home.clone());
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let conversation_manager = Arc::new(ConversationManager::new(auth_manager.clone()));
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let codex_message_processor = CodexMessageProcessor::new(
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auth_manager,
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conversation_manager,
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outgoing.clone(),
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codex_linux_sandbox_exe,
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config,
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);
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Self {
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outgoing,
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codex_message_processor,
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initialized: false,
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}
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}
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pub(crate) async fn process_request(&mut self, request: JSONRPCRequest) {
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let request_id = request.id.clone();
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if let Ok(request_json) = serde_json::to_value(request)
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&& let Ok(codex_request) = serde_json::from_value::<ClientRequest>(request_json)
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{
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match codex_request {
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// Handle Initialize internally so CodexMessageProcessor does not have to concern
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// itself with the `initialized` bool.
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ClientRequest::Initialize { request_id, params } => {
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if self.initialized {
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let error = JSONRPCErrorError {
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code: INVALID_REQUEST_ERROR_CODE,
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message: "Already initialized".to_string(),
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data: None,
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};
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self.outgoing.send_error(request_id, error).await;
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return;
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} else {
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let ClientInfo {
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name,
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title: _title,
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version,
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} = params.client_info;
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let user_agent_suffix = format!("{name}; {version}");
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if let Ok(mut suffix) = USER_AGENT_SUFFIX.lock() {
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*suffix = Some(user_agent_suffix);
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}
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let user_agent = get_codex_user_agent();
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let response = InitializeResponse { user_agent };
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self.outgoing.send_response(request_id, response).await;
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self.initialized = true;
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return;
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}
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}
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_ => {
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if !self.initialized {
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let error = JSONRPCErrorError {
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code: INVALID_REQUEST_ERROR_CODE,
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message: "Not initialized".to_string(),
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data: None,
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};
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self.outgoing.send_error(request_id, error).await;
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return;
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}
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}
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}
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self.codex_message_processor
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.process_request(codex_request)
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.await;
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} else {
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let error = JSONRPCErrorError {
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code: INVALID_REQUEST_ERROR_CODE,
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message: "Invalid request".to_string(),
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data: None,
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};
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self.outgoing.send_error(request_id, error).await;
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}
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}
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pub(crate) async fn process_notification(&self, notification: JSONRPCNotification) {
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// Currently, we do not expect to receive any notifications from the
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// client, so we just log them.
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tracing::info!("<- notification: {:?}", notification);
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}
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/// Handle a standalone JSON-RPC response originating from the peer.
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pub(crate) async fn process_response(&mut self, response: JSONRPCResponse) {
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tracing::info!("<- response: {:?}", response);
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let JSONRPCResponse { id, result, .. } = response;
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self.outgoing.notify_client_response(id, result).await
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}
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/// Handle an error object received from the peer.
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pub(crate) fn process_error(&mut self, err: JSONRPCError) {
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tracing::error!("<- error: {:?}", err);
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}
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}
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