tools/call never dispatched after Desktop update 2026-07-21 (Windows 11)

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

Problem Description After updating Claude Desktop on 2026-07-21, MCP Filesystem server responds correctly to initialize and tools/list, but tools/call is never dispatched when Claude attempts to use tools.
System
OS: Windows 11
Claude Desktop version: installed 2026-07-21
MCP Server: Filesystem (official extension from Settings > Developer)

Después de actualizar Claude Desktop el 2026-07-21, el servidor MCP Filesystem (extensión oficial) responde correctamente a initialize y tools/list, pero tools/call nunca se despacha cuando Claude intenta usar las herramientas.

• OS: Windows 11
• Claude Desktop version: instalada el 2026-07-21
• Servidor MCP: Filesystem (extensión oficial desde Settings > Developer)

Comportamiento actual

initialize: ✓ successful
tools/list: ✓ successful
tools/call: ✗ never dispatched (independent of server used)

• initialize: ✓ exitoso
• tools/list: ✓ exitoso
• tools/call: ✗ nunca se despacha

What Should Happen?

tools/call debería despacharse después de tools/list exitoso

Error Messages/Logs

Steps to Reproduce

1. Activar extensión oficial Filesystem desde Settings > Developer
2. Servidor aparece como "running"
3. Claude intenta usar herramientas del filesystem
4. tools/call nunca se ejecuta (visible en logs MCP)

Tested all three configurations:
• Official Filesystem extension only
• npx-based filesystem only
• Both simultaneously
Identical instant failure in all three permutations
Bug is independent of the server and lives in Desktop's tools/call dispatch layer

Claude Model

Not sure / Multiple models

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

Versión 1.24012.1 (0adcae)(Desktop) 2.1.217 (Claude Code)

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

VS Code integrated terminal

Additional Information

Already Tried
Restarted Desktop and PC multiple times
Left only official extension (no manual configuration)
Verified server appears as "running"
MCP logs confirm initialize and tools/list work correctly

Ya probé

• Reiniciar Desktop y PC múltiples veces
• Dejar solo extensión oficial (sin configuración manual)
• Verificar que servidor aparece "running"
• Logs MCP confirman initialize y tools/list funcionan

El problema comenzó exactamente después de la actualización del 2026-07-21, coincidiendo con incidentes resueltos ese día.