Unclear Whether MCP servers still receive background-task tool calls through the remaining mechanism, and under what conditions, is not settled.
MCP (Model Context Protocol) servers are outside programs that give Claude Code extra tools. In one of the places where Claude Code calls an MCP tool, it no longer has the option of asking the server to run the call as a background task. That option used to track the task, watch it, and tell Claude "Running in background; you'll be notified when it completes." That place now always makes an ordinary tool call and waits for the answer.
A separate background-task mechanism for MCP tool calls is still present in another part of Claude Code.
This matters mainly to people who build MCP servers: one older route for background tool calls is gone, so a server should not rely on receiving background-task requests from it.
Whether MCP servers still receive background-task tool calls through the remaining mechanism, and under what conditions, is not settled.