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

4 tlogan 3 8/9/2025, 6:55:17 PM

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?

Comments (3)

unsupp0rted · 2h ago

I thought this was a Cursor problem. GPT-5 is extremely slow at output.

It seems to speed up after a “cold start” though, which seems highly unlikely technically, but that’s what it feels like.

rickcarlino · 3h ago

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...

tlogan · 2h ago

OK - so we are not crazy.

The official response seems to be: set reasoning to the lowest and service_tier to priority, and it should work as fast as GPT-4o. But that is not the case.

They are probably still tuning it. Or maybe GPT-5 is not meant to be replacement for GPT-4o / GPT-4.1. Or this is going to be a new normal (slowest).

Remote Work Comes to Piloting Ships (wsj.com)

Redis 8.2 is GA and brings more performance, efficiency, and new commands (redis.io)

Initial findings from the DecodeME genome-wide association study of ME/CFS (research.ed.ac.uk)

Surprising, but Inevitable: Stories, Jokes, Puzzles, and Proofs (danfabulich.medium.com)

My experiences with AI agents and what I'm worried about (speculumx.at)

Are We There Yet? The Jetsons and the City of the Future (2023) [pdf] (cinemadev.cntv.usc.edu)

Microglia to the Rescue (science.org)

Consent and Compromise: How We Got Access to 22 Internal Microsoft Services (research.eye.security)

Agent.md (ampcode.com)

TSMC targets AI acceleration with A14 process and 'System on Wafer-X' (networkworld.com)

Publishing free eBook designed and written by GPT-5 – "The Human Transformer" (2472241684911.gumroad.com)

Height Comparison Chart (heightcomparisonchart.com)

Dilemma of Spent Geothermal Water Injection into Rock Masses (mdpi.com)

Today Linus Torvalds told a Google engineer that his code is garbage (twitter.com)

NASA's SpaceX Crew-10 Mission Returns, Splashes Down Off California (nasa.gov)

Memory Corruption Vulnerabilities

From trixie, armel is no longer supported as a regular architecture (debian.org)

Show HN: GPU Profiling That's Useful in 60 Seconds (keysandcaches.com)

Mar-a-Lago Face (en.wikipedia.org)

GradeLab – AI That Grades Handwritten Exams with 98% Accuracy

Wikipedia editors fight AI-generated mistakes (washingtonpost.com)

Qryptr: Airgapped ECC Text Messenger (qryptr.com)

The Rise and Fall of Bayesian Statistics (johndcook.com)

Show HN: Tohum – Project Provisoning Tool (tohum.rs)

Exposing Novel Prompt Injections, "Toxic Flows" in Agentic Systems (invariantlabs.ai)

Show HN: Cerebras Code Monitor – TUI for monitoring rate limits (github.com)

Starfish-killing bacteria revealed as cause of biggest undersea disease outbreak (nhm.ac.uk)

Evidence Found for Planet Around Closest Sun-Like Star (caltech.edu)

Curious about the training data of OpenAI's new GPT-OSS models? I was too (twitter.com)

List of Individual Rocks (en.wikipedia.org)

Labyrinth with AI – get to the target without being caught (game.saas-tips-sports.com)

Do you hate Jupyter notebooks? introducing bashnota (Open Source) (offline.bashnota.com)

Engineer tries teaching an Octopus to play Piano [video] (youtube.com)

I made an app that lets you build your own GPT-like AI agents trained in minutes (chatvia.ai)

Every watt matters: How low-power memory is transforming data centers (micron.com)

Mic Drop, a multiplayer karaoke game that tests your lyrical knowledge (micdrop.gg)

Show HN: A Personalized News Podcast Generator (Open Source, BYOK) (github.com)

Show HN: TimerMe – A fast, theme-aware productivity timer built with HonoX (github.com)

Making a centrifuge to launch to orbit (SpinLaunch) (wired.com)

How to Determine What Is Important (medium.com)

"The Hollow Men" at 100 (prufrock.substack.com)

Why is GPT-5 a generational leap in reasoning? (coderabbit.ai)

Delaware's AI Sandbox (aigovernancelead.substack.com)

AI-Agent-Host (github.com)

Giving AI 'a dose of evil' may make it less evil, headline in robot apocalypse (pcgamer.com)

Synchronizing Clocks by Leveraging Local Clock Properties (2022) (usenix.org)

New noise cameras pit drivers of fast cars against their neighbors (wsj.com)

Show HN: Raiz – Simple CLI for managing and tracing requirements (github.com)

Microsft to require cloud account for MW10 extended security updates (tomshardware.com)

Retirement of Microsoft Lens (support.microsoft.com)

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

Comments (3)