{"version":"2.1.292","anchor":"mcp-protocol-negotiation-skipped-for-stdio-when-set-to-auto","canonical_anchor":"mcp-protocol-negotiation-skipped-for-stdio-when-set-to-auto","heading":"Local MCP servers now use protocol negotiation by default","tier":"notice","area":"MCP","scope":"individual","heads_up":true,"url":"https:\/\/changelogs.core-directive.com\/v\/2.1.292\/e\/mcp-protocol-negotiation-skipped-for-stdio-when-set-to-auto","release_url":"https:\/\/changelogs.core-directive.com\/v\/2.1.292","markdown":"### Local MCP servers now use protocol negotiation by default\n\nStdio MCP servers now use automatic protocol negotiation unless a server-side setting explicitly turns it off\n\n**What**\n\nStdio MCP servers (tool servers that run as a local program on your machine) now use automatic protocol negotiation, where Claude Code probes the server to agree on a protocol version. They fall back to the older handshake only when the server-side setting comes back explicitly off. Before, with no value from the server, they used the older handshake. The setting has read on for this site's account and for the anonymous baseline since 2026-09-29.\n\nOther details:\n\n- In automatic mode, stdio servers can skip an earlier check that probed the older listing method\n\n- HTTP servers already used negotiation by default\n\n- claude.ai proxy and remote proxy connections still fall back to the older handshake\n\n- The log line for the older HTTP and server-sent events fallback now says \"this server\" instead of \"this connector\"\n\n**Why**\n\nLocal MCP servers may now connect with the newer protocol directly, without going through the older probe first.\n\n- Flag `tengu_mcp_protocol_negotiation_stdio`: On for this account, and not off by default (read for one account on one subscription tier against v2.1.292; this account: on, anonymous baseline: on, compiled default: on) These values were read against a different version of Claude Code, so treat them as the nearest reading available instead of one taken on this release.\n- Flag `tengu_mcp_legacy_sse_fallback`: Not enough to say (read for one account on one subscription tier against v2.1.292; this account: no value returned, anonymous baseline: no value returned, compiled default: on) These values were read against a different version of Claude Code, so treat them as the nearest reading available instead of one taken on this release.\n- Area: MCP\n- Tier: You'll notice\n- Useful: 3\/5\n- Signal: 2\/5\n- Scope: individual\n- Heads-up: yes"}