The concept of mode has been deprecated, there is now only the agent field in the config.
An agent can be cycled through as your primary agent with <tab> or you can spawn a subagent by @ mentioning it. if you include a description of when to use it, the primary agent will try to automatically use it
Full docs here: https://opencode.ai/docs/agents/
adamdotdevin
Dax Raad
Dax