Before you upgrade your backend to GPT-5... read this post.

Just migrated to GPT-5 and immediately downgraded back to GPT-4.1.

You'd assume with a new SOTA model, you should and can easily just change the model in your code to 'GPT-5' - wrong.

A few frustrations I encountered that I did not see in any migration docs:

• 1. Temperature is deprecated
  You can no longer set custom temperature values. Remove it entirely or set it to 1. That's it. If you were using previous models, you probably had a different temperature than 1.
• Field name changes
  max_tokens → max_completion_tokens
• GPT-5 is way less creative than 4.1, especially for story writing or creative apps - it could pretty much break your app's functionality.

Check out other devs' frustrations on the openai forums.