Claude Desktop on Windows breaks filesystem MCP tool calls after `tools/list`
simpleowo · reddit · 2026-07-22
A Windows 11 user reports that Claude Desktop 1.24012.1.0 on the MSIX build can complete MCP startup and tools/list, but never dispatches tools/call for the filesystem server.
They tried the official filesystem extension, custom mcpServers entries with both npx and node, renaming the server, and editing config.json live — but every path fails with UtilityProcess Check: Extension [name] not found in installed extensions. The issue blocks access to an Obsidian vault and appears to be a Windows-specific Claude Desktop bug pending an Anthropic fix.
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