Codex Tip: Start a New Chat After Changing config.toml or Subagent Config

Melvin Vivas · X post · 2026-09-08 · Open on X

Topics: AI Dev Tools & Productivity, AI Agents, Tool Use & MCP · Level: intermediate

Summary

If you change the project-level Codex config.toml or subagent configuration, start a new chat. Otherwise the session keeps using the previous model settings and subagents. He found this by checking the Codex traces.

Key points

• Project-level config.toml and subagent configs load when a chat starts.
• An existing chat keeps the old model and subagent settings after you edit the config.
• Start a new chat for the changes to take effect.
• Check agent traces to see which configuration was actually used.

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

• Start a new Codex chat after editing config.toml or subagent configs.
• Check the traces to confirm which model and subagents were used.