{"version":"2.1.292","anchor":"mcp-stdio-restart-once-with-serverdiscover-when-legacy-ini","canonical_anchor":"mcp-stdio-restart-once-with-serverdiscover-when-legacy-ini","heading":"Local MCP servers get one retry with the newer handshake when the old one fails","tier":"notice","area":"MCP","scope":"individual","heads_up":false,"url":"https:\/\/changelogs.core-directive.com\/v\/2.1.292\/e\/mcp-stdio-restart-once-with-serverdiscover-when-legacy-ini","release_url":"https:\/\/changelogs.core-directive.com\/v\/2.1.292","markdown":"### Local MCP servers get one retry with the newer handshake when the old one fails\n\nIf a stdio MCP server remembered as old-style fails to start, Claude Code forgets that and restarts it once with the newer handshake\n\n**What**\n\nClaude Code remembers when a stdio MCP server (a tool server that runs as a local program on your machine) only spoke the older handshake on an earlier connection. Now, if that server returns an error to the older handshake, Claude Code throws away what it remembered and restarts the server once using the newer discovery handshake. Before, only a different failure case tried the newer handshake again on a fresh connection.\n\nThe log messages for this were reworded, and the timeout handling when connecting to stdio servers changed.\n\nThe server-controlled setting for protocol negotiation on stdio servers now defaults to on when the server sends nothing. It has read on for this site's account and for the anonymous baseline since 2026-09-29.\n\n**Why**\n\nStdio MCP servers now try the newer protocol by default, and a server that was wrongly remembered as old-style gets a second chance instead of staying stuck on the older handshake.\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- Area: MCP\n- Tier: You'll notice\n- Useful: 2\/5\n- Signal: 1\/5\n- Scope: individual\n- Heads-up: no"}