Codex 5.3 vs Claude Opus 4.6 Side by Side in Cursor

Melvin Vivas · X post · 2026-03-01 · Open on X

Topics: AI Dev Tools & Productivity, LLM Fundamentals · Level: beginner

Summary

The creator says he stopped using OpenAI models for coding after GPT-5.2, but Codex 5.3 won him back. He now runs Codex 5.3 side by side with Claude Opus 4.6 in Cursor.

Key points

• The creator stopped using OpenAI models for coding after version 5.2.
• He says Codex 5.3 'hits different', a clear improvement for coding.
• He runs Codex 5.3 and Claude Opus 4.6 side by side in Cursor.
• Comparing several models in one editor helps you pick the best one per task.

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
• Claude Opus 4.6 · tool · anthropic.com · paid
  Anthropic's Claude Opus model, version 4.6, which Claude Code was running in this comparison.
  Also in: GLM-5.1 vs Claude Code (Opus 4.6): One-Shot Three.js Racing Game Eval (Melvin Vivas on X · notes), GLM-5.1 Reportedly Beats Claude Opus 4.6 on Cybersecurity (Melvin Vivas on X · notes), MiniMax 2.7 One-Shots a Linear Clone at 95% Lower Cost (Melvin Vivas on X · notes), When one coding model gets stuck, switch to another (Melvin Vivas on X · notes)
• Cursor · tool · x.com · free · recommended by both Bashiri Smith & Melvin Vivas
  AI-native code editor (VS Code with AI built in).
  Also in: GLM 5.3 and GLM 5.3 Flash now in Cursor (Melvin Vivas on X · notes), Grok Bot Can Now Hand Off Coding Tasks to Cursor (Melvin Vivas on X · notes), Why Plan Mode Still Matters in AI Coding Assistants (Codex, Claude, Cursor) (Melvin Vivas on X · notes), Why Plan Mode Still Matters in AI Coding Agents (Codex, Claude, Cursor) (Melvin Vivas on X · notes) and 121 more

Try this

• Compare coding models side by side in your editor.