Frontier Model as Orchestrator, Local Open Models as Subagents

Melvin Vivas · X post · 2026-09-14 · Open on X

Topics: AI Agents, Tool Use & MCP, AI System Design & Architecture · Level: intermediate

Summary

The creator describes a chat-and-code app he is building with Codex's help. A frontier model acts as the orchestrator and hands work to local or open models running as subagents, which keeps costs down while the strong model handles planning.

Key points

• Architecture: a frontier model orchestrates and plans, and delegates subtasks to subagents.
• The subagents run on local or open-weight models to cut cost and API usage.
• The app supports both chat and coding workflows.
• The creator is using Codex to build it.

Resources mentioned

• OpenAI Codex · tool · openai.com · paid
  OpenAI's coding agent. In the diagram it writes code, fixes review findings and drives the build loop. The creator also used it to make this video.
  Also in: An agent bot that installs and drives Codex on its own (Melvin Vivas on X · notes), Asking a Coder bot to install Codex (Melvin Vivas on X · notes), Sign in with ChatGPT: Setting Usage Limits for Each App (Melvin Vivas on X · notes), Codex Cloud Environments Must Be Saved & Published Before Use (Melvin Vivas on X · notes) and 240 more

Try this

• Build a chat-and-code app where a frontier model orchestrates and local or open models run as subagents.