Ever wanted to know how to customize the Claude Agent in Xcode 27+, then below is a helpful example.

You can customize things like model effort level and default model version per family.

Create/Edit ~/Library/Developer/Xcode/CodingAssistant/ClaudeAgentConfig/settings.json:

{
  "model": "claude-sonnet-5",
  "availableModels": ["sonnet", "opus"],
  "effortLevel": "high",
  "env": {
    "ANTHROPIC_DEFAULT_SONNET_MODEL": "claude-sonnet-5",
    "ANTHROPIC_DEFAULT_OPUS_MODEL": "claude-opus-5"
  }
}

Make sure to restart Xcode when you change the above file.

To check what model Xcode is using, prompt:

what model are you

Resources:

• Claude Model IDs
• Claude Env Variables