{"version":"2.1.295","anchor":"mcp-protocol-negotiation-for-claudeai-proxy-servers-now-def","canonical_anchor":"mcp-protocol-negotiation-for-claudeai-proxy-servers-now-def","heading":"claude.ai connectors now use automatic MCP protocol negotiation by default","tier":"notice","area":"MCP","scope":"individual","heads_up":true,"url":"https:\/\/changelogs.core-directive.com\/v\/2.1.295\/e\/mcp-protocol-negotiation-for-claudeai-proxy-servers-now-def","release_url":"https:\/\/changelogs.core-directive.com\/v\/2.1.295","markdown":"### claude.ai connectors now use automatic MCP protocol negotiation by default\n\nMCP servers reached through claude.ai connectors now agree a protocol version automatically unless the server explicitly turns this off\n\n**What**\n\nConnectors that come through your claude.ai account reach MCP servers (outside programs that give Claude Code extra tools). Claude Code can either use the older fixed way of talking to them or negotiate, meaning the two sides agree which version of the protocol to use. The fallback for this choice has moved from off to on, so these connections now negotiate automatically unless the server sends an explicit off, in which case they stay on the older way.\n\nWhile negotiation is still in progress, only these messages may be sent: `server\/discover`, `initialize`, `notifications\/initialized`, `ping`, `tools\/list`, `tools\/call`, `notifications\/cancelled` and `notifications\/roots\/list_changed`. Any other request fails with the stored error.\n\nIn the most recent reading, the flag server returned this setting on for this site's account and for an anonymous check, along with the matching setting for HTTP connections.\n\n**Why**\n\nclaude.ai connector servers will use the newer negotiation wherever the server does not override it, so their behaviour may differ from before.\n\n- Flag `tengu_mcp_protocol_negotiation_claudeai`: On for this account, and not off by default (read for one account on one subscription tier against v2.1.295; 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_protocol_negotiation_http`: On for this account, and not off by default (read for one account on one subscription tier against v2.1.295; 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- Area: MCP\n- Tier: You'll notice\n- Useful: 3\/5\n- Signal: 2\/5\n- Scope: individual\n- Heads-up: yes"}