MCP Startup Tax

Description

Dominant latency factor in Claude Code startup for users with 5+ MCP servers installed. Each MCP server process must complete a list_tools discovery call before the session starts. 7 servers averaging 400ms each = 2.8s startup overhead minimum before first message. MCP Tool Search's lazy loading (v2.1.40) eliminated the cost of tool DEFINITIONS but not server process spawn — so the tax still applies, it just shrank.

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src-20260409-f2ae567df131