CLAUDE_CODE_MCP_SERVER_URL

Updated October 13, 2026 by Alex Sorokoletov

CLAUDE_CODE_MCP_SERVER_URL is a Claude Code environment variable: The companion to MCP_SERVER_NAME, providing the server endpoint URL. Also removed. Together these formed a pair for routing MCP requests through a single helper process. Added in v2.1.85 and still present in v2.1.294. It is not in the official reference.

How to set it

For one session, export it in the shell that starts Claude Code:

export CLAUDE_CODE_MCP_SERVER_URL=<value>
claude

To apply it to every session, add it to the env object of a settings file:

// ~/.claude/settings.json
{
  "env": {
    "CLAUDE_CODE_MCP_SERVER_URL": "<value>"
  }
}

Release notes that mention it

• Claude Code v2.1.87 — 2 New Environment Variables: OAuth Console and Trusted Devices
• Claude Code v2.1.85 — 6 New Environment Variables: MCP Server Config and a 7 MB Diet
• Claude Code Version Tracker: Undocumented Env Vars, Feature Gates & Models

Related variables

• MCP_REMOTE_SERVER_CONNECTION_BATCH_SIZE: Remote MCP connection batch size.
• MCP_SERVER_CONNECTION_BATCH_SIZE: Concurrent MCP server connections.
• ANTHROPIC_BASE_URL: Custom endpoint for Anthropic services.
• CLAUDE_CODE_API_BASE_URL: Custom Claude Code API base URL for proxies.
• CLAUDE_CODE_GB_BASE_URL: An internal base URL override, possibly for a "gradebook" or grading service used during internal testing.
• CLAUDE_CODE_MCP_TOOL_IDLE_TIMEOUT
• CLAUDE_CODE_PROXY_URL: Full proxy URL, injected into the helper subprocess's environment.
• DATABASE_URL

Frequently asked questions

All variables, searchable: Claude Code environment variables.