{"version":"2.1.319","anchor":"sdk-mcp-servers-can-run-in-a-modern-protocol-mode","canonical_anchor":"sdk-mcp-servers-can-run-in-a-modern-protocol-mode","heading":"SDK MCP servers can connect without the usual setup handshake","tier":"use","area":"SDK","scope":"individual","heads_up":false,"url":"https:\/\/changelogs.core-directive.com\/v\/2.1.319\/e\/sdk-mcp-servers-can-run-in-a-modern-protocol-mode","release_url":"https:\/\/changelogs.core-directive.com\/v\/2.1.319","markdown":"### SDK MCP servers can connect without the usual setup handshake\n\nIn-process SDK MCP servers marked as modern now connect with saved capabilities and a response cache, skipping the setup handshake\n\n**Unclear.** It is not clear what sets the `modern` flag, so SDK users cannot tell how to turn this mode on.\n\n**What**\n\nWith the SDK, which is the kit for building programs on top of Claude Code, you can run MCP servers inside your own program. MCP (Model Context Protocol) is the standard Claude Code uses for outside tools. Previously every such server connected the same way. Now Claude Code checks a per-server `modern` flag. When it is set, Claude Code connects using capabilities it already discovered and a store for cached responses, and skips the initialize handshake that normally opens the connection.\n\n**Why**\n\nThis is early support for a newer, stateless version of the MCP protocol for SDK servers, where a server does not need to remember earlier exchanges.\n\n- Area: SDK\n- Names: `modern`\n- Tier: Use it now\n- Useful: 4\/5\n- Signal: 4\/5\n- Scope: individual\n- Heads-up: no"}