What
MCP servers are outside programs that give Claude Code extra tools. When Claude Code connects to one, it normally sends several separate requests: a greeting, then requests for the server's tools, prompts and resources. New code for remote (CCR) sessions asks the server to send all of that along with the first reply, using an X-MCP-Prefetch header. If the server confirms with an X-CCR-MCP-Prefetch marker, the later requests are answered from that first reply. If this fails, Claude Code falls back to sending the normal requests.
Why
Fewer back-and-forth requests should make MCP servers ready sooner in remote sessions.
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