{"version":"2.1.281","anchor":"mcp-discovery-cache-now-keyed-on-whether-the-mcp-apps-host-i","canonical_anchor":"mcp-discovery-cache-now-keyed-on-whether-the-mcp-apps-host-i","heading":"MCP discovery cache now keyed on whether the MCP Apps host is enabled","tier":null,"area":null,"url":"https:\/\/changelogs.core-directive.com\/v\/2.1.281\/e\/mcp-discovery-cache-now-keyed-on-whether-the-mcp-apps-host-i","release_url":"https:\/\/changelogs.core-directive.com\/v\/2.1.281","markdown":"### MCP discovery cache now keyed on whether the MCP Apps host is enabled\n\nThe MCP discovery cache is now kept separately depending on whether the MCP Apps host is enabled\n\n**Unclear.** Whether `CLAUDE_CODE_MCP_APPS_HOST` is an environment variable or a setting, and how a user turns it on, is not shown.\n\n**What**\n\nClaude Code saves what it learns from MCP servers (Model Context Protocol servers, which give Claude extra tools) in a discovery cache. The cache is a stored copy, so Claude Code does not have to ask the servers again. The cache's file name and lookup key now record whether the MCP Apps host is enabled, which gives one copy for each case. When a cache entry is written or deleted, both copies are now handled.\n\n`CLAUDE_CODE_MCP_APPS_HOST` is what turns on the `io.modelcontextprotocol\/ui` extension capability.\n\n**Why**\n\nWhen the MCP Apps host is turned on or off, Claude Code no longer reuses discovery results that were saved under the other setting."}