6 ms·

Addendum to GPT-5 system card: GPT-5-Codex

250 points by wertyk 1y ago

bayesianbot 1y ago
I've been extremely impressed (and actually had quite a good time) with GPT-5 and Codex so far. It seems to handle long context well, does a great job researching the code, never leaves things half-done (with long tasks it may leave some steps for later, but it never does 50% of a step and then just randomly mock a function like Gemini used to), and gives me good suggestions if I'm trying to do something I shouldn't. And the Codex CLI also seems to be getting constant, meaningful updates.
- EnPissant 1y ago
  My experience with Codex / Gpt-5: - The smartest model I have used. Solves problems better than Opus-4.1. - It can be lazy. With Claude Code / Opus, once given a problem, it will generally work until completion. Codex will often perform only the first few steps and then ask if I want to continue to do the rest. It does this even if I tell it to not stop until completion. - I have seen severe degradation near max context. For example, I have seen it just repeat the next steps every time I tell it to continue and I have to manually compact. I'm not sure if the problems are Gpt-5 or Codex. I suspect a better Codex could resolve them.
  - brookst 1y ago
    Claude seems to have gotten worse for me, with both that kind of laziness and a new pattern where it will write the test, write the code, run the test, and then declare that the test is working perfectly but there are problems in the (new) code that need to be fixed. Very frustrating, and happening more often.
    - elliot07 1y ago
      They for sure nerfed it within the last ~3 weeks. There's a measurable difference in quality.
      - conception 1y ago
        They actually just had a bug fix and it seems like it recently got a lot better in the last week or so
  - M4v3R 1y ago
    Context degradation is a real problem with all frontier LLMs. As a rule of thumb I try to never exceed 50% of available context window when working with either Claude Sonnet 4 or GPT-5 since the quality drops really fast from there.
    - EnPissant 1y ago
      I've never seen that level of extreme degradation (just making a small random change and repeating the same next steps infinitely) on Claude Code. Maybe Claude Code is more aggressive about auto compaction. I don't think Codex even compacts without /compact.
      - Jcampuzano2 1y ago
        I think some of it is not necessarily auto compaction but the tooling built in. For example claude code itself very frequently builds in to remind the model what its working on and should be doing which helps always keeps its tasks in the most recent context, and overall has some pretty serious thought put into its system prompt and tooling. But they have suffered quite a lot of degradation and quality issues recently. To be honest unless Anthropic does something very impactful sometime soon I think they're losing their moat they had with developers as more and more jump to codex and other tools. They kind of massively threw their lead imo.
        EnPissant 1y ago
        Yeah, I think you are right.
    - darkteflon 1y ago
      Agreed, and judicious use of subagents to prevent pollution of the main thread is another good mitigant.
    - faangguyindia 1y ago
      I cap my context at 50k tokens.
  - tanvach 1y ago
    I also noticed the laziness compared to Sonnet models but now I feel it’s a good feature. Sonnet models, now I realize, are way too eager to hammer out code with way more likelihood of bugs.
  - bayesianbot 1y ago
    I definitely agree with all of those points. I just really prefer it completing steps and asking me if we should continue to next step rather than doing half of the step and telling me it's done. And the context degradation seems quite random - sometimes it hits way earlier, sometimes we go through crazy amount of tokens and it all works out.
  - apigalore 1y ago
    Yes, this is the one thing stopping me from going to Codex completely. Currently, it's kind of annoying that Codex stops often and asks me what to do, and I just reply "continue". Even though I already gave it a checklist. With GPT‑5-Codex they do write: "During testing, we've seen GPT‑5-Codex work independently for more than 7 hours at a time on large, complex tasks, iterating on its implementation, fixing test failures, and ultimately delivering a successful implementation." https://openai.com/index/introducing-upgrades-to-codex/ https://openai.com/index/introducing-upgrades-to-codex/
- mritchie712 1y ago
  Have you used Claude Code? How does it compare?
  - mmaunder 1y ago
    It's objectively a big improvement over Claude Code. I'm rooting for anthropic, but they better make a big move or this will kill CC.
    - nightshift1 1y ago
      What are the usage limits like compared to Claude Code? Is it more like 5× or 20×? For twice the price, it would have to be very good.
      - naiv 1y ago
        https://help.openai.com/en/articles/11369540-using-codex-with-your-chatgpt-plan https://help.openai.com/en/articles/11369540-using-codex-wit... have to say not sure what this even means and what the exact definition of a message is in this context. with claude code max20 I was constantly hitting limits, with codex not once yet
        mmaunder 1y ago
        Same. We're not hitting limits at all with Codex and it's ridiculously good at managing and preserving its context window while getting a metric fuckton of work done. It's kind of unbelievable actually. I don't know re billing. Not my dept.
    - mike_hearn 1y ago
      Are you talking about Codex CLI or their GitHub integration? GPT-5 is a great model. I tried Codex CLI Rust, as they seem to be deprecating the JS version, and it is awful. I don't know what possessed them to try and write a TUI in Rust but it isn't working. The Claude Code UI is hugely superior.
- mmaunder 1y ago
  Agreed. We're hardcore Claude Code users and my CC usage trended down to zero pretty quickly after I started using Codex. The new model updates today are great. Very well done OpenAI team!! CC was an existential threat. You responded and absolutely killed it. Your move Anthropic.
  - Jcampuzano2 1y ago
    To be fair, Anthropic kinda did this to themselves. I consider it as a pretty massive throw on their end in terms of the fairly tight grasp they had on developer sentiment. Everyone else slowly caught up and/or surpassed them while they simultaneously had quality control issues and service degradation plaguing their system - ALL while having the most expensive models comparatively in terms of intelligence.
    - mmaunder 1y ago
      Agreed. I really wish Google would get their act together because I think they have the potential of being faster, cheaper with bigger context windows. They're so great at hardcore science and engineering, but they absolutely suck at products.
      - bjackman 1y ago
        I think this is being downvoted coz it doesn't seem to be really responding to the thread, and maybe it isn't, but for anyone who hasn't tried Gemini CLI: My experience after a month or so of heavy use is exactly this. The AI is rock solid. I'm pretty consistently impressed with its ability to derive insights from the code, when it works. But the client is flaky, the backend is flaky, and the overall experience for me is always "I wish I could just use Claude". Say 1 in 10 queries craps out (often the client OOMs even though I have 192Gb of RAM). Sounds like a 10% reliability issue but actually it just pushes me into "fuck this I'll just do it myself" so it knocks out like 50% of the value of the product. (Still, I wouldn't be surprised if this can be fixed over the next few months, it could easily be very competitive IMO).
- FergusArgyll 1y ago
  It doesn't seem to have any internal tools it can use. For example, web search; It just runs curl in the terminal. Compared to Gemini CLI that's rough but it does handle pasting much better... Maybe I'm just using both wrong...
  - ollybee 1y ago
    web search too is off by default
  - gizmodo59 1y ago
    Use --search option when you start codex
    - FergusArgyll 1y ago
      Thanks!
  - Tiberium 1y ago
    It does have web search - it's just not enabled by default. You can enable it with --search or in the config, then it can absolutely search, for example finding manuals/algorithms.
    - FergusArgyll 1y ago
      Thanks!
- catlover76 1y ago
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- robotswantdata 1y ago
  Agreed ditched my Claude code max for the $200 pro ChatGPT. Gemini cli is too inconsistent, good for documentation tasks. Don’t let it write code for you
  - icelancer 1y ago
    Gemini's tool calling being so bad is pretty amazing. Hopefully in the next iteration they fix it, because the model itself is very good.
    - robbrulinski 1y ago
      That has been my experience as well with every Gemini model, ugh!
    - nowittyusername 1y ago
      This is a recurring theme with Google. Their models are phenomenal but the systems around them are so bad that it degrades the whole experience. Veo3 great model horrible website, and so on...
      - brianjking 1y ago
        Their massive increase in token processing since Veo3 and nano banana have been released would say otherwise... Or we're all just used to eating things we don't like and smiling.
- DanielVZ 1y ago
  Can someone compare it to cursor? So far i see people compare it with Claude code but I’ve had much more success and cost effectiveness with cursor than Claude code
  - bionhoward 1y ago
    Doesn’t compare, because Cursor has a privacy mode. Why would anyone want to pay OpenAI or Anthropic to train their bots on your business codebase? You know where that leads? Unemployment!
- vitorgrs 1y ago
  Gemini seems to be pretty awful as agentic coding. It always finish the task, and when I see the result, it just breaks my code. Not sure the fault it's "doing bad code", I guess it's just not being good at being agentic. Saw this on Gemini CLI and other tools. GLM, Kimi, Qwen-Code all behaves better for me. Probably Gemini 3 will fix this, as Gemini 2.5 Pro it's "old" by now.
  - faangguyindia 1y ago
    Gemini CLI is bad, model itself is really good.
- troupo 1y ago
  > then just randomly mock a function like Gemini used to Claude Code does that on longer tasks. Time to give Codex a try I guess.
Difwif 1y ago
Is this available to use now in Codex? Should I see a new /model?
- andrewmunsell 1y ago
  Yes, but I had to update the Codex CLI manually via NPM to see it. The VS Code extension auto-updated for me
withinboredom 1y ago
Codex always appears to use spaces, even when the project uses tabs (aka, a Go file). It's so annoying.
- wahnfrieden 1y ago
  Just use a linter hook to standardize style
- asadm 1y ago
  this + any coding conventions should ALWAYS be a post process. DO NOT include them in your prompt, you are losing model accuracy over these tiny things.
  - withinboredom 1y ago
    It helps to actually be able to read the diffs of its proposals/changes in the terminal. The changing from tabs -> spaces on every line it touches generally results in unreadable messes. I have a pretty complex project, so I need to keep an eye on it to ensure it doesn't go off the rails and delete all the code to get a build to pass (it wouldn't be the first time).
    - wahnfrieden 1y ago
      You are poisoning your context making it focus on an unusual requirement contrary to most of its training data. It’s a formatter task, not an LLM task In fact you should convert your code to spaces at least before LLM sees it. It’ll improve your results by looking more like its training data.
      - ameliaquining 1y ago
        Presumably the Go source files in the training corpus used tabs?
      - withinboredom 1y ago
        Go uses tabs. Full stop. There is no Go code with spaces. Not if they're using the built-in formatter, anyway. In any case, this is about the diff codex is outputting, not the code I commit. With Claude, I generally don't need to run `go fmt`, but with codex, it is absolutely necessary.
lvl155 1y ago
I think it would be cool to see *nix “emulation” integrated into coding AIs. I don’t think it’s necessary to run these agents inside of container as most people are right now. That’s a lot of overhead.
- simonw 1y ago
  You mean instead of them running the code that they are writing they pretend to run the code and the model shows what it thinks would happen? I don't like that at all. Actually running the code is the single most effective protection we have against coding mistakes, from both humans and machines. I think it's absolutely worth the complexity and performance overhead of hooking up a real container environment. Not to mention you can run a useful code execution container in 100MB of RAM on a single CPU (or slice thereof). Simulating that with an LLM takes at least one GPU and 100GB or more of VRAM.
  - lvl155 1y ago
    I understand your point but I basically find myself running all my agents in barebones containers and they’re basically short-run make-or-kill types. And once we ramp up agent counts, possibly into the thousands, that could add up rapidly. Of course, you would run milestone tests on actual container/envs but I think there might be a need for lighter solutions for rapid agent dev runs.
    - withinboredom 1y ago
      You do realize that there is virtually no overhead in running containers, right? That's the entire point of their existence. They're just processes, with specific permissions (to generalize it). Your computer can run thousands of processes without sweating.
      - lvl155 1y ago
        > You do realize that there is virtually no overhead in running containers, right? That's the entire point of their existence. No, I didn’t know running containers used “virtually no overhead.” It appears I can run millions of containers without any resource constraint? Is that some sort of cheat code?
sergiotapia 1y ago
I signed up to OpenAI, verified my identity, and added my credit card, bought $10 of credits. But when I installed Codex and tried to make a simple code bugfix, I got rate limited nearly immediately. As in, after 3 "steps" the agent took. Are you meant to only use Codex with their $200 "unlimited" plans? Thanks!
- wahnfrieden 1y ago
  Use Plus first
  - sergiotapia 1y ago
    Thank you - so to confirm Codex _requires_ basically the Plus or $200 plans otherwise it just does not work?
    - Tiberium 1y ago
      You can use Codex CLI with an API key instead of a subscription, but then you won't have access to this new GPT-5 Codex model, since it's not out on the API yet. But normal GPT-5 in Codex is perfectly fine.
      - sergiotapia 1y ago
        That's what was in my OP, I used the API approach, but the rate limits were insanely low (seemingly?) the agent died after 3 steps in a single question.
        embirico 1y ago
        when was that @sergiotapia? last week we just upped the base rate limit for new API accounts
        sergiotapia 1y ago
        This was September 11th, 2025. gpt-5-2025-08-07 38.887K input tokens That was my usage, and I got rate limited. Thank you for your tips!
darkteflon 1y ago
Does Codex have token-hiding (cf Anthropic’s “subagents”)? I was tempted to give Codex a try but a colleague was stung by their pricing. Apparently if you go over your Pro plan allocation, they just quietly and automatically start billing you per-token?
- steveklabnik 1y ago
  I tried Codex with the $20/month plan recently and it did exactly what Claude Code does, stop and tell you “sorry, you’re out of credit, come back in x days.”
  - darkteflon 1y ago
    Thank you, glad to hear it. Sounds like my colleague might have had it misconfigured. I’ll give Codex a try then.
    - embirico 1y ago
      Hey, I work on Codex—absolutely no way that a user on a Pro plan would somehow silently move to token-based billing. You just hit a limit and have to wait for the reset. (Which also sucks, and which we're also improving early warnings of.)
      - darkteflon 1y ago
        Thanks for that, appreciate the clarification. I’ll check with my colleague and report back on his experience. Certainly don’t want to misrepresent.
6thbit 1y ago
Direct link to the pdf https://cdn.openai.com/pdf/97cc5669-7a25-4e63-b15f-5fd5bdc4d149/gpt-5-codex-system-card.pdf https://cdn.openai.com/pdf/97cc5669-7a25-4e63-b15f-5fd5bdc4d...
jumploops 1y ago
Interesting, the new model uses a different prompt in Codex CLI that's ~half the size (10KB vs. 23KB) of the previous prompt[0][1]. SWE-bench performance is similar to normal gpt-5, so it seems the main delta with `gpt-5-codex` is on code refactors (via internal refactor benchmark 33.9% -> 51.3%). As someone who recently used Codex CLI (`gpt-5-high`) to do a relatively large refactor (multiple internal libs to dedicated packages), I kept running into bugs introduced when the model would delete a file and then rewrite it (missing crucial or important details). My approach would have been to just the copy the file over and then make package-specific changes, so maybe better tool calling is at play here. Additionally, they claim the new model is more steerable (both with AGENTS.md and generally). In my experience, Codex CLI w/gpt-5 is already a lot more steerable than Claude Code, but any improvements are welcome! [0]https://github.com/openai/codex/blob/main/codex-rs/core/gpt_5_codex_prompt.md https://github.com/openai/codex/blob/main/codex-rs/core/gpt_... [1]https://github.com/openai/codex/blob/main/codex-rs/core/prompt.md https://github.com/openai/codex/blob/main/codex-rs/core/prom... (comment reposted from other thread)
- robotswantdata 1y ago
  saw the same behaviour What worked was getting it to first write a detailed implementation plan for a “junior contractor” then attempt it in phases (clearing task window each time) and told to use /tmp to copy files and transform them then update the original. Looking forward to trying the new model out on the next refactor!
  - jumploops 1y ago
    Yes, regardless of tool, I always create a separate plan doc for larger changes Will try adding the instructions specific to refactors (i.e. copy/move files, don't rewrite when possible) I've also found it helpful, especially for certain regressions, to basically create a new branch for any Codex/CC assisted task (even if part of a larger task). Makes it easier to identify regressions due to recent changes (i.e. look at git diff, it worked previously) Telling the "agent" to manage git leads to more context pollution than I want, so I manage all commits/branches myself, but I'm sure that will change as the tools improve/they do more RL on full-cycle software dev
ionwake 1y ago
Can someone explain what this all means? Has codex just been updated to use chat-gpt 5 ? Or is this just extra info?
- amrrs 1y ago
  It is a new version of GPT-5 that's been primarily optimized for coding. Hence this confusing name - GPT-5-Codex. This model is available inside all OpenAI codex products. Yet to be available on Api The model is supposed to be better at code reviews and Comments than the other GPT-5 variant. It can also think/work upto 7 hours.
  - ionwake 1y ago
    Amazing cheers
- simonw 1y ago
  I posted some notes here that might be useful: https://simonwillison.net/2025/Sep/15/gpt-5-codex/ https://simonwillison.net/2025/Sep/15/gpt-5-codex/ Even shorter version: - New coding-specialist model called GPT-5-Codex, coming soon to the API but for now available in their Codex CLI, VS Code and Codex Cloud products - New code review product (part of Codex Cloud) that can review PRs for you - New model promises better code review, less pointless comments and can vary its reasoning effort for simple vs complex tasks
  - naiv 1y ago
    The pelican is not so convincing though :) So a bit in line with what Theo mentioned in his video that he was not happy with the ui capabilities
    - ionwake 1y ago
      Good point I forgot about the pelican!
  - ionwake 1y ago
simonw 1y ago
This should probably be merged with the other GPT-5-Codex thread at https://news.ycombinator.com/item?id=45252301 https://news.ycombinator.com/item?id=45252301 since nobody in this thread is talking about the system card addendum.
WhitneyLand 1y ago
Apparently today is the first release with MCP support. Updates (v0.36) https://github.com/openai/codex/releases https://github.com/openai/codex/releases
- artdigital 1y ago
  Codex had MCP support for a long long time
  - WhitneyLand 1y ago
    Really, I thought I had checked for it a couple months ago and didn’t see it? Commented after I saw this added in today’s release notes: “initial MCP interface and docs”
zapnuk 1y ago
It would be nice if this model would be good enough to update their typscript sdk (+agents library) to use, or at least support, zod v4 - they still use v3. Had to spend quite a long time to figure out a dependency error...
hereme888 1y ago
Codex just ate up my remaining turns for the day for a clearly defined patch that should have taken just a few actions. Anyone else experienced that?
- arresin 1y ago
  Yes. I believe it’s a bug from their issues page
- _9za9 1y ago
  Yes. "Failed. You've hit your usage limit. Upgrade to Pro (https://openai.com/chatgpt/pricing https://openai.com/chatgpt/pricing) or try again in 3 days 10 minutes." I can't use the IDE codex at all now it seems.
mindwok 1y ago
Codex with GPT-5-High is extremely good. Like many I was a bit "meh" about the GPT 5 release, however once I started using it with Codex it became clear there was a substantial improvement in a capability I wasn't really paying attention to, which is tool calling. Or more specifically, when to call a tool. Ask GPT-5-High a question about your codebase and watch the things it looks for, and things it searches for (if you use --search). It has very good taste on how to navigate and solve a problem.
bezzi 1y ago
is this model just acting super slow with you guys too?
- naiv 1y ago
  Feels slower than GPT-5 and I understood it that medium should be a lot faster than high but for me it's almost the same , so I don't see a reason preferring medium.
tschellenbach 1y ago
is it already supported in cursor? don't see it just yet
- mindwok 1y ago
  It's not available via the API yet, so probably not.
- toomanyflops 1y ago
  while not available as a specific model to use in cursor, it is available via openai’s codex extension on vscode/cursor
bionhoward 1y ago
Meh, what’s the point if it’s got no privacy, which companies want to let OpenAI read your codebase? Cursor keeps winning because of privacy mode IMHO, there is no level of capability which outweighs privacy mode
- Topfi 1y ago
  Maybe I misunderstand you, but looking at their own documentation on the topic, I hardly see any advantage in terms of privacy when using Cursor Privacy Mode over OpenAIs Data Controls: > OpenAI > We rely on many of OpenAI's models to give AI responses. Requests may be sent to OpenAI even if you have an Anthropic (or someone else's) model selected in chat (e.g. for summarization)*. We have a zero data retention agreement with OpenAI. Source: https://cursor.com/security https://cursor.com/security I will say that the Security page by the Cursor team is a very nice overview, even going into Auth, etc. and applaud that, but see nothing here that differentiates their use of e.g. OpenAI models from the agreements OpenAI offers themselves. Essentially, I don't see why anyone would have such severely heightened trust in Cursor over competitors in this area. If they only provided self hosted models, I could understand it, but not the way they operate. Personally, both because of the way and on what LLMs have been trained on, on top of my expectation in terms of privacy, regardless of model provider assurances, I'd treat any LLM derived/assisted/reviewed code as public the second you send it to some providers server hosted model and some form of FOSS to boot. Basically, if you used Cursor, Codex, Augment or anything of that sort, I'd reduce any future privacy expectations straight away, might as well put it on public Github for everyone to see. Only self-hosting on prem is an option for keeping control of your codebase, though personally, I'd still consider licensing such code as FOSS, considering no model wasn't trained on EUPL, GPL, etc. Personal (very much philosophical and not at all legal, as that goes into what training is, weights, etc. arguments that can go on eternal) opinion, but I'd argue whether you are MSFT or a small startup, if you derive a significant amount of new code from LLMs, arguing that copyleft shouldn't be at the very least on the mind of your legal department isn't reasonable, but of course, this will have to be decided by courts and likely in favour of those with the best legal teams. I doubt if any of the "80% of our code is written by LLMs" were true, that'd convince a court to enforce copyleft upon the product in question, but personally, that'd be my viewpoint. Regardless of licensing, if you send your code to Cursor, purely privacy wise, you shouldn't have reservations about OpenAI.
curtisszmania 1y ago
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8cvor6j844qw_d6 1y ago
Anyone can share their thoughts on Claude Code vs Codex? I've just started out trying out Claude Code and am not sure how Codex compares on React projects. From my initial usage, it seems Claude Code planning mode is superior than its normal? mode, and giving it an overall direction to proceed and rather than just stating a desired feature seems to produce better results. It also does better if a large task are split into very small sub-tasks.
- arthurcolle 1y ago
  claude code for first 3-4 months was a monster. it's been optimized
- nowittyusername 1y ago
  I've used Claude Code for about 3 months now. Was a big fan until recent changes lobotomized it. So I switched over to codex about 2 weeks ago and loving it so far, way better experience. Today with the introduction of the new model, i been refactoring old claude code project all day and so far things are looking good. I am very impressed, OpenAI cooked hard here...
hamish-b 1y ago
My problem _still_ with all of the codex/gpt based offerings is that they think for way too long. After using Claude 4 models through cursor max/ampcode I feel much more effective given it's speed. Ironically, Claude Code feels just as slow as codex/gpt (even with my company patching through AWS bedrock). Only makes me feel more that the consumer modes have perverse incentives.
- strangescript 1y ago
  I almost never have to reprompt GPT-5-high (now gpt-5-codex-high) where I would be reprompting claude code all the time. It feels like its faster, doing more, but its taking more of the developers time by getting things wrong.
- hmottestad 1y ago
  It’s great for multitasking. I’ve cloned one of the repos I work on into a new folder and use Codex CLI in there. I feed it bug reports that users have submitted, while I work on bigger tasks.
foft 1y ago
I've had great results with Codex, though I found ChatGPT 5 was giving much better results than the existing model. So ended up using that directly instead. So very excited to have the model upgraded in Codex itself. The main issues with Codex now seem to be the very poor stability (it seems to be down almost 50% of the time) and lack of custom containers. Hoping those get solved soon, particularly the stability. I also wonder where the price will end up, it currently seems unsustainably cheap.
- raincole 1y ago
  > I also wonder where the price will end up, it currently seems unsustainably cheap. Jetbrains has a $30/mo subscription (with gpt5 backend) and the quota burns so fast. Assuming Jetbrains is at breakeven price, either OpenAI has some secret sauce or they're losing money for Codex.
anshumankmr 1y ago
So is this a new model or just a different checkpoint for coding?
esafak 1y ago
Does OpenAI demand biometrics to use GPT-5-Codex?
mkoygh76k 1y ago
lhb8ubk88/.mves

250 points by wertyk 1y ago

I've been extremely impressed (and actually had quite a good time) with GPT-5 and Codex so far. It seems to handle long context well, does a great job researching the code, never leaves things half-done (with long tasks it may leave some steps for later, but it never does 50% of a step and then just randomly mock a function like Gemini used to), and gives me good suggestions if I'm trying to do something I shouldn't. And the Codex CLI also seems to be getting constant, meaningful updates.

EnPissant 1y ago
My experience with Codex / Gpt-5: - The smartest model I have used. Solves problems better than Opus-4.1. - It can be lazy. With Claude Code / Opus, once given a problem, it will generally work until completion. Codex will often perform only the first few steps and then ask if I want to continue to do the rest. It does this even if I tell it to not stop until completion. - I have seen severe degradation near max context. For example, I have seen it just repeat the next steps every time I tell it to continue and I have to manually compact. I'm not sure if the problems are Gpt-5 or Codex. I suspect a better Codex could resolve them.
- brookst 1y ago
  Claude seems to have gotten worse for me, with both that kind of laziness and a new pattern where it will write the test, write the code, run the test, and then declare that the test is working perfectly but there are problems in the (new) code that need to be fixed. Very frustrating, and happening more often.
  - elliot07 1y ago
    They for sure nerfed it within the last ~3 weeks. There's a measurable difference in quality.
    - conception 1y ago
      They actually just had a bug fix and it seems like it recently got a lot better in the last week or so
- M4v3R 1y ago
  Context degradation is a real problem with all frontier LLMs. As a rule of thumb I try to never exceed 50% of available context window when working with either Claude Sonnet 4 or GPT-5 since the quality drops really fast from there.
  - EnPissant 1y ago
    I've never seen that level of extreme degradation (just making a small random change and repeating the same next steps infinitely) on Claude Code. Maybe Claude Code is more aggressive about auto compaction. I don't think Codex even compacts without /compact.
    - Jcampuzano2 1y ago
      I think some of it is not necessarily auto compaction but the tooling built in. For example claude code itself very frequently builds in to remind the model what its working on and should be doing which helps always keeps its tasks in the most recent context, and overall has some pretty serious thought put into its system prompt and tooling. But they have suffered quite a lot of degradation and quality issues recently. To be honest unless Anthropic does something very impactful sometime soon I think they're losing their moat they had with developers as more and more jump to codex and other tools. They kind of massively threw their lead imo.
      - EnPissant 1y ago
        Yeah, I think you are right.
  - darkteflon 1y ago
    Agreed, and judicious use of subagents to prevent pollution of the main thread is another good mitigant.
  - faangguyindia 1y ago
    I cap my context at 50k tokens.
- tanvach 1y ago
  I also noticed the laziness compared to Sonnet models but now I feel it’s a good feature. Sonnet models, now I realize, are way too eager to hammer out code with way more likelihood of bugs.
- bayesianbot 1y ago
  I definitely agree with all of those points. I just really prefer it completing steps and asking me if we should continue to next step rather than doing half of the step and telling me it's done. And the context degradation seems quite random - sometimes it hits way earlier, sometimes we go through crazy amount of tokens and it all works out.
- apigalore 1y ago
  Yes, this is the one thing stopping me from going to Codex completely. Currently, it's kind of annoying that Codex stops often and asks me what to do, and I just reply "continue". Even though I already gave it a checklist. With GPT‑5-Codex they do write: "During testing, we've seen GPT‑5-Codex work independently for more than 7 hours at a time on large, complex tasks, iterating on its implementation, fixing test failures, and ultimately delivering a successful implementation." https://openai.com/index/introducing-upgrades-to-codex/ https://openai.com/index/introducing-upgrades-to-codex/
mritchie712 1y ago
Have you used Claude Code? How does it compare?
- mmaunder 1y ago
  It's objectively a big improvement over Claude Code. I'm rooting for anthropic, but they better make a big move or this will kill CC.
  - nightshift1 1y ago
    What are the usage limits like compared to Claude Code? Is it more like 5× or 20×? For twice the price, it would have to be very good.
    - naiv 1y ago
      https://help.openai.com/en/articles/11369540-using-codex-with-your-chatgpt-plan https://help.openai.com/en/articles/11369540-using-codex-wit... have to say not sure what this even means and what the exact definition of a message is in this context. with claude code max20 I was constantly hitting limits, with codex not once yet
      - mmaunder 1y ago
        Same. We're not hitting limits at all with Codex and it's ridiculously good at managing and preserving its context window while getting a metric fuckton of work done. It's kind of unbelievable actually. I don't know re billing. Not my dept.
  - mike_hearn 1y ago
    Are you talking about Codex CLI or their GitHub integration? GPT-5 is a great model. I tried Codex CLI Rust, as they seem to be deprecating the JS version, and it is awful. I don't know what possessed them to try and write a TUI in Rust but it isn't working. The Claude Code UI is hugely superior.
mmaunder 1y ago
Agreed. We're hardcore Claude Code users and my CC usage trended down to zero pretty quickly after I started using Codex. The new model updates today are great. Very well done OpenAI team!! CC was an existential threat. You responded and absolutely killed it. Your move Anthropic.
- Jcampuzano2 1y ago
  To be fair, Anthropic kinda did this to themselves. I consider it as a pretty massive throw on their end in terms of the fairly tight grasp they had on developer sentiment. Everyone else slowly caught up and/or surpassed them while they simultaneously had quality control issues and service degradation plaguing their system - ALL while having the most expensive models comparatively in terms of intelligence.
  - mmaunder 1y ago
    Agreed. I really wish Google would get their act together because I think they have the potential of being faster, cheaper with bigger context windows. They're so great at hardcore science and engineering, but they absolutely suck at products.
    - bjackman 1y ago
      I think this is being downvoted coz it doesn't seem to be really responding to the thread, and maybe it isn't, but for anyone who hasn't tried Gemini CLI: My experience after a month or so of heavy use is exactly this. The AI is rock solid. I'm pretty consistently impressed with its ability to derive insights from the code, when it works. But the client is flaky, the backend is flaky, and the overall experience for me is always "I wish I could just use Claude". Say 1 in 10 queries craps out (often the client OOMs even though I have 192Gb of RAM). Sounds like a 10% reliability issue but actually it just pushes me into "fuck this I'll just do it myself" so it knocks out like 50% of the value of the product. (Still, I wouldn't be surprised if this can be fixed over the next few months, it could easily be very competitive IMO).
FergusArgyll 1y ago
It doesn't seem to have any internal tools it can use. For example, web search; It just runs curl in the terminal. Compared to Gemini CLI that's rough but it does handle pasting much better... Maybe I'm just using both wrong...
- ollybee 1y ago
  web search too is off by default
- gizmodo59 1y ago
  Use --search option when you start codex
  - FergusArgyll 1y ago
    Thanks!
- Tiberium 1y ago
  It does have web search - it's just not enabled by default. You can enable it with --search or in the config, then it can absolutely search, for example finding manuals/algorithms.
  - FergusArgyll 1y ago
    Thanks!
catlover76 1y ago
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robotswantdata 1y ago
Agreed ditched my Claude code max for the $200 pro ChatGPT. Gemini cli is too inconsistent, good for documentation tasks. Don’t let it write code for you
- icelancer 1y ago
  Gemini's tool calling being so bad is pretty amazing. Hopefully in the next iteration they fix it, because the model itself is very good.
  - robbrulinski 1y ago
    That has been my experience as well with every Gemini model, ugh!
  - nowittyusername 1y ago
    This is a recurring theme with Google. Their models are phenomenal but the systems around them are so bad that it degrades the whole experience. Veo3 great model horrible website, and so on...
    - brianjking 1y ago
      Their massive increase in token processing since Veo3 and nano banana have been released would say otherwise... Or we're all just used to eating things we don't like and smiling.
DanielVZ 1y ago
Can someone compare it to cursor? So far i see people compare it with Claude code but I’ve had much more success and cost effectiveness with cursor than Claude code
- bionhoward 1y ago
  Doesn’t compare, because Cursor has a privacy mode. Why would anyone want to pay OpenAI or Anthropic to train their bots on your business codebase? You know where that leads? Unemployment!
vitorgrs 1y ago
Gemini seems to be pretty awful as agentic coding. It always finish the task, and when I see the result, it just breaks my code. Not sure the fault it's "doing bad code", I guess it's just not being good at being agentic. Saw this on Gemini CLI and other tools. GLM, Kimi, Qwen-Code all behaves better for me. Probably Gemini 3 will fix this, as Gemini 2.5 Pro it's "old" by now.
- faangguyindia 1y ago
  Gemini CLI is bad, model itself is really good.
troupo 1y ago
> then just randomly mock a function like Gemini used to Claude Code does that on longer tasks. Time to give Codex a try I guess.

Difwif 1y ago

Is this available to use now in Codex? Should I see a new /model?

andrewmunsell 1y ago
Yes, but I had to update the Codex CLI manually via NPM to see it. The VS Code extension auto-updated for me

withinboredom 1y ago

Codex always appears to use spaces, even when the project uses tabs (aka, a Go file). It's so annoying.

wahnfrieden 1y ago
Just use a linter hook to standardize style
asadm 1y ago
this + any coding conventions should ALWAYS be a post process. DO NOT include them in your prompt, you are losing model accuracy over these tiny things.
- withinboredom 1y ago
  It helps to actually be able to read the diffs of its proposals/changes in the terminal. The changing from tabs -> spaces on every line it touches generally results in unreadable messes. I have a pretty complex project, so I need to keep an eye on it to ensure it doesn't go off the rails and delete all the code to get a build to pass (it wouldn't be the first time).
  - wahnfrieden 1y ago
    You are poisoning your context making it focus on an unusual requirement contrary to most of its training data. It’s a formatter task, not an LLM task In fact you should convert your code to spaces at least before LLM sees it. It’ll improve your results by looking more like its training data.
    - ameliaquining 1y ago
      Presumably the Go source files in the training corpus used tabs?
    - withinboredom 1y ago
      Go uses tabs. Full stop. There is no Go code with spaces. Not if they're using the built-in formatter, anyway. In any case, this is about the diff codex is outputting, not the code I commit. With Claude, I generally don't need to run `go fmt`, but with codex, it is absolutely necessary.

lvl155 1y ago

I think it would be cool to see *nix “emulation” integrated into coding AIs. I don’t think it’s necessary to run these agents inside of container as most people are right now. That’s a lot of overhead.

simonw 1y ago
You mean instead of them running the code that they are writing they pretend to run the code and the model shows what it thinks would happen? I don't like that at all. Actually running the code is the single most effective protection we have against coding mistakes, from both humans and machines. I think it's absolutely worth the complexity and performance overhead of hooking up a real container environment. Not to mention you can run a useful code execution container in 100MB of RAM on a single CPU (or slice thereof). Simulating that with an LLM takes at least one GPU and 100GB or more of VRAM.
- lvl155 1y ago
  I understand your point but I basically find myself running all my agents in barebones containers and they’re basically short-run make-or-kill types. And once we ramp up agent counts, possibly into the thousands, that could add up rapidly. Of course, you would run milestone tests on actual container/envs but I think there might be a need for lighter solutions for rapid agent dev runs.
  - withinboredom 1y ago
    You do realize that there is virtually no overhead in running containers, right? That's the entire point of their existence. They're just processes, with specific permissions (to generalize it). Your computer can run thousands of processes without sweating.
    - lvl155 1y ago
      > You do realize that there is virtually no overhead in running containers, right? That's the entire point of their existence. No, I didn’t know running containers used “virtually no overhead.” It appears I can run millions of containers without any resource constraint? Is that some sort of cheat code?

sergiotapia 1y ago

I signed up to OpenAI, verified my identity, and added my credit card, bought $10 of credits. But when I installed Codex and tried to make a simple code bugfix, I got rate limited nearly immediately. As in, after 3 "steps" the agent took. Are you meant to only use Codex with their $200 "unlimited" plans? Thanks!

wahnfrieden 1y ago
Use Plus first
- sergiotapia 1y ago
  Thank you - so to confirm Codex _requires_ basically the Plus or $200 plans otherwise it just does not work?
  - Tiberium 1y ago
    You can use Codex CLI with an API key instead of a subscription, but then you won't have access to this new GPT-5 Codex model, since it's not out on the API yet. But normal GPT-5 in Codex is perfectly fine.
    - sergiotapia 1y ago
      That's what was in my OP, I used the API approach, but the rate limits were insanely low (seemingly?) the agent died after 3 steps in a single question.
      - embirico 1y ago
        when was that @sergiotapia? last week we just upped the base rate limit for new API accounts
        sergiotapia 1y ago
        This was September 11th, 2025. gpt-5-2025-08-07 38.887K input tokens That was my usage, and I got rate limited. Thank you for your tips!

darkteflon 1y ago

Does Codex have token-hiding (cf Anthropic’s “subagents”)? I was tempted to give Codex a try but a colleague was stung by their pricing. Apparently if you go over your Pro plan allocation, they just quietly and automatically start billing you per-token?

steveklabnik 1y ago
I tried Codex with the $20/month plan recently and it did exactly what Claude Code does, stop and tell you “sorry, you’re out of credit, come back in x days.”
- darkteflon 1y ago
  Thank you, glad to hear it. Sounds like my colleague might have had it misconfigured. I’ll give Codex a try then.
  - embirico 1y ago
    Hey, I work on Codex—absolutely no way that a user on a Pro plan would somehow silently move to token-based billing. You just hit a limit and have to wait for the reset. (Which also sucks, and which we're also improving early warnings of.)
    - darkteflon 1y ago
      Thanks for that, appreciate the clarification. I’ll check with my colleague and report back on his experience. Certainly don’t want to misrepresent.

6thbit 1y ago

Direct link to the pdf https://cdn.openai.com/pdf/97cc5669-7a25-4e63-b15f-5fd5bdc4d149/gpt-5-codex-system-card.pdf https://cdn.openai.com/pdf/97cc5669-7a25-4e63-b15f-5fd5bdc4d...

jumploops 1y ago

Interesting, the new model uses a different prompt in Codex CLI that's ~half the size (10KB vs. 23KB) of the previous prompt[0][1]. SWE-bench performance is similar to normal gpt-5, so it seems the main delta with `gpt-5-codex` is on code refactors (via internal refactor benchmark 33.9% -> 51.3%). As someone who recently used Codex CLI (`gpt-5-high`) to do a relatively large refactor (multiple internal libs to dedicated packages), I kept running into bugs introduced when the model would delete a file and then rewrite it (missing crucial or important details). My approach would have been to just the copy the file over and then make package-specific changes, so maybe better tool calling is at play here. Additionally, they claim the new model is more steerable (both with AGENTS.md and generally). In my experience, Codex CLI w/gpt-5 is already a lot more steerable than Claude Code, but any improvements are welcome! [0]https://github.com/openai/codex/blob/main/codex-rs/core/gpt_5_codex_prompt.md https://github.com/openai/codex/blob/main/codex-rs/core/gpt_... [1]https://github.com/openai/codex/blob/main/codex-rs/core/prompt.md https://github.com/openai/codex/blob/main/codex-rs/core/prom... (comment reposted from other thread)

robotswantdata 1y ago
saw the same behaviour What worked was getting it to first write a detailed implementation plan for a “junior contractor” then attempt it in phases (clearing task window each time) and told to use /tmp to copy files and transform them then update the original. Looking forward to trying the new model out on the next refactor!
- jumploops 1y ago
  Yes, regardless of tool, I always create a separate plan doc for larger changes Will try adding the instructions specific to refactors (i.e. copy/move files, don't rewrite when possible) I've also found it helpful, especially for certain regressions, to basically create a new branch for any Codex/CC assisted task (even if part of a larger task). Makes it easier to identify regressions due to recent changes (i.e. look at git diff, it worked previously) Telling the "agent" to manage git leads to more context pollution than I want, so I manage all commits/branches myself, but I'm sure that will change as the tools improve/they do more RL on full-cycle software dev

ionwake 1y ago

Can someone explain what this all means? Has codex just been updated to use chat-gpt 5 ? Or is this just extra info?

amrrs 1y ago
It is a new version of GPT-5 that's been primarily optimized for coding. Hence this confusing name - GPT-5-Codex. This model is available inside all OpenAI codex products. Yet to be available on Api The model is supposed to be better at code reviews and Comments than the other GPT-5 variant. It can also think/work upto 7 hours.
- ionwake 1y ago
  Amazing cheers
simonw 1y ago
I posted some notes here that might be useful: https://simonwillison.net/2025/Sep/15/gpt-5-codex/ https://simonwillison.net/2025/Sep/15/gpt-5-codex/ Even shorter version: - New coding-specialist model called GPT-5-Codex, coming soon to the API but for now available in their Codex CLI, VS Code and Codex Cloud products - New code review product (part of Codex Cloud) that can review PRs for you - New model promises better code review, less pointless comments and can vary its reasoning effort for simple vs complex tasks
- naiv 1y ago
  The pelican is not so convincing though :) So a bit in line with what Theo mentioned in his video that he was not happy with the ui capabilities
  - ionwake 1y ago
    Good point I forgot about the pelican!
- ionwake 1y ago

simonw 1y ago

This should probably be merged with the other GPT-5-Codex thread at https://news.ycombinator.com/item?id=45252301 https://news.ycombinator.com/item?id=45252301 since nobody in this thread is talking about the system card addendum.

WhitneyLand 1y ago

Apparently today is the first release with MCP support. Updates (v0.36) https://github.com/openai/codex/releases https://github.com/openai/codex/releases

artdigital 1y ago
Codex had MCP support for a long long time
- WhitneyLand 1y ago
  Really, I thought I had checked for it a couple months ago and didn’t see it? Commented after I saw this added in today’s release notes: “initial MCP interface and docs”

zapnuk 1y ago

It would be nice if this model would be good enough to update their typscript sdk (+agents library) to use, or at least support, zod v4 - they still use v3. Had to spend quite a long time to figure out a dependency error...

hereme888 1y ago

Codex just ate up my remaining turns for the day for a clearly defined patch that should have taken just a few actions. Anyone else experienced that?

arresin 1y ago
Yes. I believe it’s a bug from their issues page
_9za9 1y ago
Yes. "Failed. You've hit your usage limit. Upgrade to Pro (https://openai.com/chatgpt/pricing https://openai.com/chatgpt/pricing) or try again in 3 days 10 minutes." I can't use the IDE codex at all now it seems.

mindwok 1y ago

Codex with GPT-5-High is extremely good. Like many I was a bit "meh" about the GPT 5 release, however once I started using it with Codex it became clear there was a substantial improvement in a capability I wasn't really paying attention to, which is tool calling. Or more specifically, when to call a tool. Ask GPT-5-High a question about your codebase and watch the things it looks for, and things it searches for (if you use --search). It has very good taste on how to navigate and solve a problem.

bezzi 1y ago

is this model just acting super slow with you guys too?

naiv 1y ago
Feels slower than GPT-5 and I understood it that medium should be a lot faster than high but for me it's almost the same , so I don't see a reason preferring medium.

tschellenbach 1y ago

is it already supported in cursor? don't see it just yet

mindwok 1y ago
It's not available via the API yet, so probably not.
toomanyflops 1y ago
while not available as a specific model to use in cursor, it is available via openai’s codex extension on vscode/cursor

bionhoward 1y ago

Meh, what’s the point if it’s got no privacy, which companies want to let OpenAI read your codebase? Cursor keeps winning because of privacy mode IMHO, there is no level of capability which outweighs privacy mode

Topfi 1y ago
Maybe I misunderstand you, but looking at their own documentation on the topic, I hardly see any advantage in terms of privacy when using Cursor Privacy Mode over OpenAIs Data Controls: > OpenAI > We rely on many of OpenAI's models to give AI responses. Requests may be sent to OpenAI even if you have an Anthropic (or someone else's) model selected in chat (e.g. for summarization)*. We have a zero data retention agreement with OpenAI. Source: https://cursor.com/security https://cursor.com/security I will say that the Security page by the Cursor team is a very nice overview, even going into Auth, etc. and applaud that, but see nothing here that differentiates their use of e.g. OpenAI models from the agreements OpenAI offers themselves. Essentially, I don't see why anyone would have such severely heightened trust in Cursor over competitors in this area. If they only provided self hosted models, I could understand it, but not the way they operate. Personally, both because of the way and on what LLMs have been trained on, on top of my expectation in terms of privacy, regardless of model provider assurances, I'd treat any LLM derived/assisted/reviewed code as public the second you send it to some providers server hosted model and some form of FOSS to boot. Basically, if you used Cursor, Codex, Augment or anything of that sort, I'd reduce any future privacy expectations straight away, might as well put it on public Github for everyone to see. Only self-hosting on prem is an option for keeping control of your codebase, though personally, I'd still consider licensing such code as FOSS, considering no model wasn't trained on EUPL, GPL, etc. Personal (very much philosophical and not at all legal, as that goes into what training is, weights, etc. arguments that can go on eternal) opinion, but I'd argue whether you are MSFT or a small startup, if you derive a significant amount of new code from LLMs, arguing that copyleft shouldn't be at the very least on the mind of your legal department isn't reasonable, but of course, this will have to be decided by courts and likely in favour of those with the best legal teams. I doubt if any of the "80% of our code is written by LLMs" were true, that'd convince a court to enforce copyleft upon the product in question, but personally, that'd be my viewpoint. Regardless of licensing, if you send your code to Cursor, purely privacy wise, you shouldn't have reservations about OpenAI.

curtisszmania 1y ago

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8cvor6j844qw_d6 1y ago

Anyone can share their thoughts on Claude Code vs Codex? I've just started out trying out Claude Code and am not sure how Codex compares on React projects. From my initial usage, it seems Claude Code planning mode is superior than its normal? mode, and giving it an overall direction to proceed and rather than just stating a desired feature seems to produce better results. It also does better if a large task are split into very small sub-tasks.

arthurcolle 1y ago
claude code for first 3-4 months was a monster. it's been optimized
nowittyusername 1y ago
I've used Claude Code for about 3 months now. Was a big fan until recent changes lobotomized it. So I switched over to codex about 2 weeks ago and loving it so far, way better experience. Today with the introduction of the new model, i been refactoring old claude code project all day and so far things are looking good. I am very impressed, OpenAI cooked hard here...

hamish-b 1y ago

My problem _still_ with all of the codex/gpt based offerings is that they think for way too long. After using Claude 4 models through cursor max/ampcode I feel much more effective given it's speed. Ironically, Claude Code feels just as slow as codex/gpt (even with my company patching through AWS bedrock). Only makes me feel more that the consumer modes have perverse incentives.

strangescript 1y ago
I almost never have to reprompt GPT-5-high (now gpt-5-codex-high) where I would be reprompting claude code all the time. It feels like its faster, doing more, but its taking more of the developers time by getting things wrong.
hmottestad 1y ago
It’s great for multitasking. I’ve cloned one of the repos I work on into a new folder and use Codex CLI in there. I feed it bug reports that users have submitted, while I work on bigger tasks.

foft 1y ago

I've had great results with Codex, though I found ChatGPT 5 was giving much better results than the existing model. So ended up using that directly instead. So very excited to have the model upgraded in Codex itself. The main issues with Codex now seem to be the very poor stability (it seems to be down almost 50% of the time) and lack of custom containers. Hoping those get solved soon, particularly the stability. I also wonder where the price will end up, it currently seems unsustainably cheap.

raincole 1y ago
> I also wonder where the price will end up, it currently seems unsustainably cheap. Jetbrains has a $30/mo subscription (with gpt5 backend) and the quota burns so fast. Assuming Jetbrains is at breakeven price, either OpenAI has some secret sauce or they're losing money for Codex.

anshumankmr 1y ago

So is this a new model or just a different checkpoint for coding?

esafak 1y ago

Does OpenAI demand biometrics to use GPT-5-Codex?

mkoygh76k 1y ago

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