{"version":"2.1.292","anchor":"mcp-serverdiscover-probe-memory-file-handling","canonical_anchor":"mcp-serverdiscover-probe-memory-file-handling","heading":"Protocol negotiation for local MCP servers now defaults on, with a safer memory file","tier":"notice","area":"MCP","scope":"individual","heads_up":true,"url":"https:\/\/changelogs.core-directive.com\/v\/2.1.292\/e\/mcp-serverdiscover-probe-memory-file-handling","release_url":"https:\/\/changelogs.core-directive.com\/v\/2.1.292","markdown":"### Protocol negotiation for local MCP servers now defaults on, with a safer memory file\n\nNegotiating the protocol version with local stdio MCP servers now falls back to on, and a broken record of past probes is ignored rather than trusted\n\n**What**\n\nThe switch that lets stdio MCP servers (local programs Claude Code talks to over standard input and output) use protocol-version negotiation now falls back to on when the server sends nothing. Before, it fell back to off. The flag server also returned it on for this site's account and for an account with no special settings, first seen on 2026-09-29.\n\nClaude Code can also remember what it learned from probing servers with server\/discover, which is how it asks a server what it supports. It reads this from a file and ignores the file if:\n\n- it is not a regular file\n\n- it is larger than a size limit\n\n- it cannot be read\n\nWhen the file is ignored, Claude Code notes this in its log and probes servers as if nothing had been remembered. Entries for stdio servers are kept apart from the others.\n\n**Why**\n\nLocal MCP servers can now get protocol negotiation without anyone having to turn it on remotely, and a damaged or oversized memory file cannot get in the way of connecting.\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: yes"}