{"version":"2.1.274","anchor":"tengu-mcp-protocol-negotiation-http-fallback-flips-from-lega","canonical_anchor":"mcp-http-protocol-negotiation-default-flips-to-enabled-via-t","heading":"HTTP MCP servers now default to auto-negotiating protocol version","tier":"notice","area":"MCP","scope":null,"heads_up":null,"url":"https:\/\/changelogs.core-directive.com\/v\/2.1.274\/e\/tengu-mcp-protocol-negotiation-http-fallback-flips-from-lega","release_url":"https:\/\/changelogs.core-directive.com\/v\/2.1.274","markdown":"### HTTP MCP servers now default to auto-negotiating protocol version\n\nMCP servers of type 'http' now default to auto-negotiating the protocol version instead of falling back to legacy mode\n\n**What**\n\nFor MCP servers configured with type `http`, the fallback behavior for protocol-version negotiation changed: it now defaults to `auto` mode (attempting version probing\/auto-negotiation) instead of going straight to legacy mode. This is controlled by the gate `tengu_mcp_protocol_negotiation_http`, which now defaults to enabled (true) unless explicitly turned off. Other MCP connection types (claudeai, stdio, ccr-proxy) are unaffected and still default to legacy fallback.\n\n**Why**\n\nAuto-negotiation lets Claude Code and an HTTP-based MCP server agree on the best protocol version to use, rather than always assuming the older legacy protocol. This can improve compatibility and unlock newer protocol features automatically for HTTP MCP servers, without any configuration change needed.\n\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 v2.1.274; 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- Names: `tengu_mcp_protocol_negotiation_http`\n- Tier: You'll notice\n- Useful: 3\/5\n- Signal: 2\/5"}