How to run only Claude Code's workflow agents on one model

Claude Code v2.1.296 added CLAUDE_CODE_WORKFLOW_SUBAGENT_MODEL, an environment variable that runs every workflow agent on one model while other subagents keep their own.

Put it in the env block of your settings file.

// ~/.claude/settings.json
{
  "env": {
    "CLAUDE_CODE_WORKFLOW_SUBAGENT_MODEL": "<model>"
  }
}

The related CLAUDE_CODE_SUBAGENT_MODEL, which sets the default for all subagents, accepts an alias such as haiku or a full model name. The changelog doesn't spell out the value format for the new variable, and it isn't in the environment variable docs yet.

If a task runs lots of workflow agents, use it to put just the workflows on a lighter model and leave code-editing subagents on their usual one. On anything older than v2.1.296, run claude update first.