Headless startup changes how it waits for deferred MCP servers

What

MCP servers are add-on programs that give Claude extra tools. In headless sessions (runs with no chat screen, such as claude -p or remote sessions), Claude Code can wait for these servers to finish starting before it handles the first command. Two changes adjust that wait. Both sit behind the tengu_headless_mcp_prewait gate, a switch Anthropic controls remotely, and nothing has been read about that gate.

• A new skipFullyDeferredServers policy lets startup skip waiting for pending stdio servers (servers run as local programs) that the conversation does not need. The skipped servers are passed as skipServerNames, and this applies both to the wait before the first command and to the wait after plugins sync. If a server was skipped at first but is no longer skippable when the first command runs, Claude Code may wait for it after all.
• Connections to servers set through mcp_set_servers are now deferred only when the gate is on and the main conversation has not yet sent its first request. A new step, joinAfterFirstRequest, waits for servers that were still connecting early on.

Why

Headless and remote sessions can start faster when they are not held up by MCP servers the conversation never uses. The second change covers servers added after the first request: under the old rule they could be deferred and then never waited for.