{"version":"2.1.309","anchor":"headless-mcp-wiring-now-also-runs-when-the-host-handed-mcp-l","canonical_anchor":"headless-mcp-wiring-now-also-runs-when-the-host-handed-mcp-l","heading":"SDK sessions set up MCP tools when the host passes in MCP listings","tier":"notice","area":"SDK","scope":"individual","heads_up":false,"url":"https:\/\/changelogs.core-directive.com\/v\/2.1.309\/e\/headless-mcp-wiring-now-also-runs-when-the-host-handed-mcp-l","release_url":"https:\/\/changelogs.core-directive.com\/v\/2.1.309","markdown":"### SDK sessions set up MCP tools when the host passes in MCP listings\n\nIn print and SDK sessions, MCP setup now also runs when the host program hands Claude Code its MCP listings\n\n**What**\n\nIn print mode and SDK sessions, where Claude Code runs without its interactive screen under another program called the host, Claude Code sets up connections to MCP servers, which supply extra tools. This setup used to run only in one kind of session. It now also runs when the host has handed Claude Code its MCP listings.\n\nIn that new case the tool list is built from the declared server names, but Claude Code does not listen for sign-in renewals or for changes to a server's tool list.\n\n**Why**\n\nThis changes when programs built on the SDK get MCP tools wired up for them.\n\n- Area: SDK\n- Tier: You'll notice\n- Useful: 2\/5\n- Signal: 2\/5\n- Scope: individual\n- Heads-up: no"}