fix: make session MCP startup lazy

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

@@ -2755,7 +2755,7 @@ async fn thread_resume_with_overrides_defers_updated_at_until_turn_start() -> Re
 }
 
 #[tokio::test]
-async fn thread_resume_fails_when_required_mcp_server_fails_to_initialize() -> Result<()> {
+async fn thread_resume_returns_before_required_mcp_server_initializes() -> Result<()> {
     let server = create_mock_responses_server_repeating_assistant("Done").await;
     let codex_home = TempDir::new()?;
     let rollout = setup_rollout_fixture(codex_home.path(), &server.uri())?;
@@ -2770,24 +2770,13 @@ async fn thread_resume_fails_when_required_mcp_server_fails_to_initialize() -> R
             ..Default::default()
         })
         .await?;
-    let err: JSONRPCError = timeout(
-        DEFAULT_READ_TIMEOUT,
-        mcp.read_stream_until_error_message(RequestId::Integer(resume_id)),
-    )
-    .await??;
-
-    assert!(
-        err.error
-            .message
-            .contains("required MCP servers failed to initialize"),
-        "unexpected error message: {}",
-        err.error.message
-    );
-    assert!(
-        err.error.message.contains("required_broken"),
-        "unexpected error message: {}",
-        err.error.message
-    );
+    let _: ThreadResumeResponse = to_response(
+        timeout(
+            DEFAULT_READ_TIMEOUT,
+            mcp.read_stream_until_response_message(RequestId::Integer(resume_id)),
+        )
+        .await??,
+    )?;
 
     Ok(())
 }

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

@@ -586,7 +586,7 @@ async fn thread_start_ephemeral_remains_pathless() -> Result<()> {
 }
 
 #[tokio::test]
-async fn thread_start_fails_when_required_mcp_server_fails_to_initialize() -> Result<()> {
+async fn thread_start_returns_before_required_mcp_server_initializes() -> Result<()> {
     let server = create_mock_responses_server_repeating_assistant("Done").await;
 
     let codex_home = TempDir::new()?;
@@ -599,24 +599,13 @@ async fn thread_start_fails_when_required_mcp_server_fails_to_initialize() -> Re
         .send_thread_start_request(ThreadStartParams::default())
         .await?;
 
-    let err: JSONRPCError = timeout(
-        DEFAULT_READ_TIMEOUT,
-        mcp.read_stream_until_error_message(RequestId::Integer(req_id)),
-    )
-    .await??;
-
-    assert!(
-        err.error
-            .message
-            .contains("required MCP servers failed to initialize"),
-        "unexpected error message: {}",
-        err.error.message
-    );
-    assert!(
-        err.error.message.contains("required_broken"),
-        "unexpected error message: {}",
-        err.error.message
-    );
+    let _: ThreadStartResponse = to_response(
+        timeout(
+            DEFAULT_READ_TIMEOUT,
+            mcp.read_stream_until_response_message(RequestId::Integer(req_id)),
+        )
+        .await??,
+    )?;
 
     Ok(())
 }

codex-rs/core/src/mcp_tool_call.rs

@@ -320,6 +320,7 @@ async fn handle_approved_mcp_tool_call(
     let arguments_value = invocation.arguments.clone();
     let connector_id = metadata.and_then(|metadata| metadata.connector_id.as_deref());
     let connector_name = metadata.and_then(|metadata| metadata.connector_name.as_deref());
+    sess.ensure_mcp_connection_manager_initialized().await;
     let server_origin = sess
         .services
         .mcp_connection_manager
@@ -1480,6 +1481,7 @@ pub(crate) async fn lookup_mcp_tool_metadata(
     server: &str,
     tool_name: &str,
 ) -> Option<McpToolApprovalMetadata> {
+    sess.ensure_mcp_connection_manager_initialized().await;
     let tools = sess
         .services
         .mcp_connection_manager
@@ -1575,6 +1577,7 @@ async fn lookup_mcp_app_usage_metadata(
     server: &str,
     tool_name: &str,
 ) -> Option<McpAppUsageMetadata> {
+    sess.ensure_mcp_connection_manager_initialized().await;
     let tools = sess
         .services
         .mcp_connection_manager

codex-rs/core/src/session/handlers.rs

@@ -468,7 +468,7 @@ pub async fn dynamic_tool_response(sess: &Arc<Session>, id: String, response: Dy
 }
 
 pub async fn refresh_mcp_servers(sess: &Arc<Session>, refresh_config: McpServerRefreshConfig) {
-    let mut guard = sess.pending_mcp_server_refresh_config.lock().await;
+    let mut guard = sess.pending_mcp_server_refresh.lock().await;
     *guard = Some(refresh_config);
 }