GPT-5.5 Codex reasoning-token clustering may be leading to degraded performance

GPT-5.5 Codex Reasoning-Token Clustering Issue

A problem has been found with GPT-5.5 Codex. It's a large language model that helps with coding tasks. The issue is with reasoning-token clustering. It seems to be causing the model to perform worse.

What is reasoning-token clustering?

Reasoning-token clustering is a way to group similar ideas together. In the context of GPT-5.5 Codex, it's used to identify and organize the relationships between different code elements. This helps the model understand how they work together. However, it appears that this feature is not working as expected.

The problem

The issue is that the model is not able to distinguish between similar code elements. This is causing it to make mistakes and produce bad code. The developers are not sure why this is happening. They're asking for help to figure out the problem. If you're interested in learning more, check out the GitHub issue here: https://github.com/openai/codex/issues/30364.