FrontendRemoteMcpToolDefinition.name validation error when many MCP servers are configured

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?

Claude Code fails with API validation error when registering MCP tool
definitions. The error occurs intermittently with the tool index changing
between sessions (observed at index 115 and 100), suggesting the issue is with
how tool names are generated server-side rather than a specific tool:

tools.100.FrontendRemoteMcpToolDefinition.name: String should match pattern
'^[a-zA-Z0-9_-]{1,64}$'

All locally-visible MCP tool names (228 checked) conform to the pattern — none
exceed 64 characters and all use only [a-zA-Z0-9_-]. The error appears to
originate from the API's internal naming of FrontendRemoteMcpToolDefinition
entries, not from the MCP servers themselves.

What Should Happen?

All MCP tool definitions should pass the API's own ^[a-zA-Z0-9_-]{1,64}$
validation, regardless of how many MCP servers are configured. The tool
registration should succeed without errors.

Error Messages/Logs

tools.115.FrontendRemoteMcpToolDefinition.name: String should match pattern
  '^[a-zA-Z0-9_-]{1,64}$'
  tools.100.FrontendRemoteMcpToolDefinition.name: String should match pattern
  '^[a-zA-Z0-9_-]{1,64}$'
  (Index changes between sessions — 115 first, then 100 after session restart)

Steps to Reproduce

1. Configure multiple MCP servers (21 total in my case — see list below)
2. Include 6 claude.ai remote integrations (Vercel, Supabase, Google Calendar,

Gmail, Canva, Asana)

1. Include 12 local workspace-mcp servers for Google services
2. Include plugin MCP servers (github, supabase, vercel, context7)
3. Start a new Claude Code session
4. The error appears during tool registration

MCP server list:
claude.ai Vercel, claude.ai Supabase, claude.ai Google Calendar,
claude.ai Gmail, claude.ai Canva, claude.ai Asana,
plugin:github:github, plugin:supabase:supabase, plugin:vercel:vercel,
plugin:context7:context7,
google-gmail, google-drive, google-calendar, google-docs,
google-sheets, google-tasks, google-contacts, google-slides,
google-forms, google-chat, google-appscript, google-search

Claude Model

Opus

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

2.1.81

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

_No response_