OpenAI discontinues GPT-5.3 Codex model, users report issues with replacements
Fans of the fast, low-cost GPT-5.3 Codex face error as OpenAI sunsets the model.
Deep Dive
A Reddit user reports encountering a 400 error when using the "gpt-5.3-codex" model with a ChatGPT account, calling it the best model—fast, reliable, and low on token consumption. The user expresses worry, claiming successor models 5.4 and 5.5 are worse and more expensive.
Key Points
- GPT-5.3 Codex model deprecated with error: 'model is not supported when using Codex with a ChatGPT account'
- Users report model was fast, reliable, and low token consumption; alternatives 5.4/5.5 seen as worse and pricier
- The change impacts developers relying on Codex for AI-assisted coding; no official communication from OpenAI
Why It Matters
Loss of a preferred coding model may increase costs and reduce efficiency for ChatGPT Codex users.