This guide explains how to configure Xcode's built-in Claude Code integration to work with third-party API endpoints instead of the official Anthropic API.
Xcode normally requires signing in through the UI with an Anthropic account or API key and doesn't offer any bypass. Even if the Xcode internal claude can use your third-party endpoint Xcode won't send any query because YoU ARe NOt LOgGeD IN. To bypass this when using a third-party endpoint, set a placeholder API key override, which you cannot do through the UI:
defaults write com.apple.dt.Xcode IDEChatClaudeAgentAPIKeyOverride ' '