{"version":"2.1.271","anchor":"new-instrumentation-firstcommandmountjoin-wait-in-first-com","canonical_anchor":"new-instrumentation-firstcommandmountjoin-wait-in-first-com","heading":"New instrumentation: firstCommandMountJoin wait in first-command startup","tier":"internal","area":"Elsewhere","scope":null,"heads_up":null,"url":"https:\/\/changelogs.core-directive.com\/v\/2.1.271\/e\/new-instrumentation-firstcommandmountjoin-wait-in-first-com","release_url":"https:\/\/changelogs.core-directive.com\/v\/2.1.271","markdown":"### New instrumentation: firstCommandMountJoin wait in first-command startup\n\nStartup now measures an added \"firstCommandMountJoin\" wait before the first command runs\n\n**What**\n\nDuring interactive startup, after the existing wait for MCP servers to be ready (`mcp_prewait_ms`), Claude Code now also waits for and measures a new `firstCommandMountJoin` step before running the first command.\n\n**Why**\n\nThis adds visibility into another part of startup timing, letting slowdowns before the first command runs be tracked more precisely.\n\n- Area: Elsewhere\n- Tier: Under the hood\n- Useful: 1\/5\n- Signal: 1\/5"}