OpenAI GPT-5 API seems to be significantly slower – is this expected?

Question

We've observed that the OpenAI GPT-5 API is noticeably slower than GPT-4.1 and GPT-4o. Is this a known or anticipated issue?

rickcarlino · Accepted Answer

The conventional response to this seems to be "Lower reasoning effort".
I have already tried this.
Like you, I am seeing a 5x slowdown compared to GPT-4O. I have lowered reasoning effort all the way, set verbosity to lowest. Still not getting good results.
https://bsky.app/profile/rickcarlino.bsky.social/post/3lvycs...

unsupp0rted · Answer

I thought this was a Cursor problem. GPT-5 is extremely slow at output.It seems to speed up after a &ldquo;cold start&rdquo; though, which seems highly unlikely technically, but that&rsquo;s what it feels like.