- Add OpenAI/ChatGPT as separate subscription option (--openai flag) - Implement native tier cross-fallback (Claude → OpenAI → Gemini) - Change fallback order: Native → OpenCode Zen → GitHub Copilot → Z.ai - Add explore agent special logic: max20 → haiku, else → grok-code - Add critical warning when Claude is not configured - Add tests for ChatGPT-only and explore agent cases