Can I use MiniMax as my default and OpenAI for complex tasks

Yes. Use MiniMax as the default and switch models per session when needed. Fallbacks are for errors, not “hard tasks,” so use /model or a separate agent.
Option A: switch per session
{
env: { MINIMAX_API_KEY: "sk-...", OPENAI_API_KEY: "sk-..." },
agents: {
defaults: {
model: { primary: "minimax/MiniMax-M2.1" },
models: {
"minimax/MiniMax-M2.1": { alias: "minimax" },
"openai/gpt-5.2": { alias: "gpt" },
},
},
},
}
Then:
/model gpt
Option B: separate agents
Agent A default: MiniMax
Agent B default: OpenAI
Route by agent or use /agent to switch
Docs: Models, Multi-Agent Routing, MiniMax, OpenAI.