GPT-5.4 Is Available in OpenAI Codex

Melvin Vivas · X post · 2026-04-02 · Open on X

Topics: AI Dev Tools & Productivity · Level: beginner

Summary

This short post says the GPT-5.4 model is now available in OpenAI's Codex coding agent and tells readers to try it.

Key points

• GPT-5.4 can now be used inside OpenAI Codex.
• The creator recommends trying it for coding tasks.

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
• GPT-5.4 · tool · openai.com · paid
  OpenAI frontier model (Thinking and Pro variants) for reasoning, coding and agents.
  Also in: Opinion: GPT-5.4 in Cursor 3 Replaces Opus for Coding (Melvin Vivas on X · notes), Splitting AI Tools: Cursor 3 + GPT-5.4 for Code, Claude for Learning (Melvin Vivas on X · notes), Creator's Coding Setup: Cursor 3 with GPT 5.4 (Melvin Vivas on X · notes), Open-Source GLM-5.1 Beats GPT-5.4 on SWE-Bench Pro (Melvin Vivas on X · notes) and 2 more

Try this

• Try GPT-5.4 in Codex