[BUG] Single session startup triggers 429 rate limit on client_data endpoint, causing false "1 MCP server failed" status

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?

When starting a single Claude Code session, the startup process fires 8 parallel requests to api.anthropic.com/api/oauth/claude_cli/client_data within ~20ms, triggering a 429 rate limit on the server side.

04:43:36.722Z [ERROR] AxiosError: [url=https://api.anthropic.com/api/oauth/claude_cli/client_data,status=429,body=Rate limited.]
04:43:36.723Z [ERROR] AxiosError: [url=https://api.anthropic.com/api/oauth/claude_cli/client_data,status=429,body=Rate limited.]
04:43:36.731Z [ERROR] AxiosError: [url=https://api.anthropic.com/api/oauth/claude_cli/client_data,status=429,body=Rate limited.]
04:43:36.731Z [ERROR] AxiosError: [url=https://api.anthropic.com/api/oauth/claude_cli/client_data,status=429,body=Rate limited.]
04:43:36.731Z [ERROR] AxiosError: [url=https://api.anthropic.com/api/oauth/claude_cli/client_data,status=429,body=Rate limited.]
04:43:36.732Z [ERROR] AxiosError: [url=https://api.anthropic.com/api/oauth/claude_cli/client_data,status=429,body=Rate limited.]
04:43:36.740Z [ERROR] AxiosError: [url=https://api.anthropic.com/api/oauth/claude_cli/client_data,status=429,body=Rate limited.]
04:43:36.741Z [ERROR] AxiosError: [url=https://api.anthropic.com/api/oauth/claude_cli/client_data,status=429,body=Rate limited.]

This causes the status bar to display "1 MCP server failed", even though both MCP servers (claude-in-chrome and claude.ai Mermaid Chart) successfully connect shortly after. The failed status appears to be a transient artifact of the rate limiting during the authorization check phase.

Expected behavior: A single session startup should not trigger rate limiting against its own API. Requests to the same endpoint should be deduplicated or serialized during initialization.

Environment:

• macOS (Darwin 25.3.0)
• Claude Code (latest auto-update channel)
• Only 1 session running

What Should Happen?

reduce the call

Error Messages/Logs

04:43:36.722Z [ERROR] AxiosError: [url=https://api.anthropic.com/api/oauth/claude_cli/client_data,status=429,body=Rate limited.]
  04:43:36.723Z [ERROR] AxiosError: [url=https://api.anthropic.com/api/oauth/claude_cli/client_data,status=429,body=Rate limited.]
  04:43:36.731Z [ERROR] AxiosError: [url=https://api.anthropic.com/api/oauth/claude_cli/client_data,status=429,body=Rate limited.]
  04:43:36.731Z [ERROR] AxiosError: [url=https://api.anthropic.com/api/oauth/claude_cli/client_data,status=429,body=Rate limited.]
  04:43:36.731Z [ERROR] AxiosError: [url=https://api.anthropic.com/api/oauth/claude_cli/client_data,status=429,body=Rate limited.]
  04:43:36.732Z [ERROR] AxiosError: [url=https://api.anthropic.com/api/oauth/claude_cli/client_data,status=429,body=Rate limited.]
  04:43:36.740Z [ERROR] AxiosError: [url=https://api.anthropic.com/api/oauth/claude_cli/client_data,status=429,body=Rate limited.]
  04:43:36.741Z [ERROR] AxiosError: [url=https://api.anthropic.com/api/oauth/claude_cli/client_data,status=429,body=Rate limited.]

-------------------------------------------
/mcp

Manage MCP servers                                                                                                                                                                                                                                                                                                    
                                                                                                                                                                                                                                                                                                                     
   2 servers                                                                                                                                                                                                                                                                                                             
                                                                                                                                                                                                                                                                                                                         
                                                                                                                                                                                                                                                                                                                         
     claude.ai                                                                                                                                                                                                                                                                                                           
                                                                                                                                                                                                                                                                                                                       
   ❯ claude.ai Mermaid Chart · ✔ connected                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  
     Built-in MCPs (always available)                                                                                                                                                                                                                                                                                
                                                                                                                                                                                                                                                                                                                     
     claude-in-chrome · ✔ connected

Steps to Reproduce

1. start claude code with "claude"
2. /exit
3. status shows "1 MCP server failed · /mcp"

Claude Model

Opus

Is this a regression?

No, this never worked

Last Working Version

_No response_

Claude Code Version

2.1.66

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

_No response_