6 ms·

GPT-5-Codex-Mini – A more compact and cost-efficient version of GPT-5-Codex

56 points by wahnfrieden 1y ago

vessenes 1y ago
Looks like a leak: https://platform.openai.com/docs/models https://platform.openai.com/docs/models does not list it, and codex-mini-latest says that it's based on 4o. I wonder if it will be faster than codex; gpt-5-nano and -mini are still very slow for me on API, surprisingly so.
- ChadNauseam 1y ago
  I noticed the same thing with -mini. It can be even slower than the full fat version. I'm guessing their infra for it is very cost-optimized to help them offer it at such a low price
  - wahnfrieden 1y ago
    They also just announced that they’re giving Pro tier prioritized access to Codex models. Are you on Pro? If not you might be getting deprioritized.
  - vessenes 1y ago
    Yeah in my mind it was smaller -> faster. But seems like it might be 'a bit smaller and batched' to hit the price target.
- simonw 1y ago
  They announced it on Twitter yesterday: https://x.com/OpenAIDevs/status/1986861734619947305 https://x.com/OpenAIDevs/status/1986861734619947305 and https://x.com/OpenAIDevs/status/1986861736041853368 https://x.com/OpenAIDevs/status/1986861736041853368 > GPT-5-Codex-Mini allows roughly 4x more usage than GPT-5-Codex, at a slight capability tradeoff due to the more compact model. > Available in the CLI and IDE extension when you sign in with ChatGPT, with API support coming soon.
cmdtab 1y ago
If any open AI devs reading this comment section: is it possible for us to get api access at runable.com ?
bgwalter 1y ago
All "AI" providers cut corners in the models right now because the subsidized cost is unsustainable. Grok's latest update made it far worse than the version right after the Grok-4 release. It makes outright mistakes now. Copilot has cut corners long ago. Google "AI" was always horrible. The whole "AI" experiment was an outrageously expensive IP laundering parlor trick that is meeting economic realities now.
- stavros 1y ago
  That's a very long-winded way of saying "it was subsidized so it could capture a large market segment, and now that's stopping", which is what SV companies have done since checks notes forever.
  - bgwalter 1y ago
    An LLM would have generated four pages on this topic in order to increase the token count! LLMs are advertised for serious applications. I don't recall that CPUs generally hallucinate except for the FDIV bug. Or that AirBnB rents you apartments that don't exist in 30% of all cases. Or that Uber cars drive into a river during 20% of all rides.
    - stavros 1y ago
      Are we talking about economics, or about hallucinations? "CPUs don't hallucinate" would be a reasonable argument if CPUs were an alternative to LLMs, which they aren't, so I'm not really sure what argument you're making there. Seems like you're saying "a calculator makes fewer mistakes than an accountant", which is true, but I still pay an accountant to do my taxes, and not a calculator.
      - bgwalter 1y ago
        I was obviously responding to your "SV companies have been doing that forever". You have introduced the general topic.
mrdarkies 1y ago
[flagged]
lostmsu 1y ago
GPT-5 and GPT-5-Codex are already not clever enough for anything interesting.
- asadm 1y ago
  not correct. are you using high reasoning? i am using codex everyday.
  - pogue 1y ago
    What sort of stuff are you using it for?
    - asadm 1y ago
      computer vision things these days.
  - wahnfrieden 1y ago
    Medium reportedly uses even higher reasoning than high, when it chooses to. Whereas high is fixed at a high but not as high level.
- jeswin 1y ago
  What's your definition of interesting? I'm half way through writing a typescript to native code translator (via .Net) compiling a large enough subset of current code with a lot of help from GPT5 and Codex CLI. It has completely blown me away. I'd like to give you a concrete example which stood out (from by now, dozens). I wanted d.ts files from the .Net Standard Libs. One immediately obvious problem is that .Net would allow classes/interfaces to be redefined if the generic type arity is different. For example, there can be SomeClass<int> and SomeClass<int, int> which are completely separate. TypeScript of course, wouldn't allow this - you can have one with all types defined, but it'd obviously be a mess. I was stuck with (quite ugly): const users = new List_1<User>(...); instead of const users = new List<User>(...); So GPT comes up with this: declare const __unspecified: unique symbol; type __ = typeof __unspecified; // Your arity-anchored delegates exist elsewhere: // import("internal/System").Action_0 // import("internal/System").Action_1<T1> // import("internal/System").Action_2<T1, T2> // import("internal/System").Action_3<T1, T2, T3> // ... up to 17 export type Action< T1 = __, T2 = __, T3 = __, // ... continue through T17 = __ > = [T1] extends [__] ? import("internal/System").Action_0 : [T2] extends [__] ? import("internal/System").Action_1<T1> : [T3] extends [__] ? import("internal/System").Action_2<T1, T2> : /* next lines follow the same pattern … */ import("internal/System").Action_3<T1, T2, T3>; This lets me write: const a: Action<number> = (n) => {}; // OK (void) const f: Func<number, string> = (s) => 20; // OK (string -> number) A human could come up with this, of course. But doing this at scale (there are many such problems which crop up), would take a lot of effort. Btw I'm using Claude for the grunt work (because its faster), but GPT5 is doing all the architecture/thinking/planning/review.
simonw 1y ago
I managed to get GPT-5-Codex-Mini to draw me a pelican. It's not a very good one! https://static.simonwillison.net/static/2025/codex-hacking-mini.png https://static.simonwillison.net/static/2025/codex-hacking-m... For comparison, here's GPT-5-Codex (not mini) https://static.simonwillison.net/static/2025/codex-hacking-default.png https://static.simonwillison.net/static/2025/codex-hacking-d... and full GPT-5: https://static.simonwillison.net/static/2025/codex-hacking-gpt-5.png https://static.simonwillison.net/static/2025/codex-hacking-g... I had quite a fun time getting those pelicans though... since GPT-5 Codex Mini isn't officially available via API yet I instead had OpenAI's Codex CLI tool extend itself (in Rust) to add a "codex prompt ..." tool which uses their existing custom auth scheme and backend API, then used that to generate the pelicans. Full details here: https://simonwillison.net/2025/Nov/9/gpt-5-codex-mini/ https://simonwillison.net/2025/Nov/9/gpt-5-codex-mini/
- aurareturn 1y ago
  Just curious, do you think LLM makers are deliberately adding training data for your pelican test by now?
  - simonw 1y ago
    I'll know if they do, because I'll notice that a new model is suspiciously great at drawing pelicans riding bicycles while still sucking at drawing other things.
- RestartKernel 1y ago
  Can't believe I'm saying this, but GPT-5's pelican is its most impressive improvement over 4o I've seen. I wonder if Codex' MoE does not contain any expert fit for this task due to its fine-tuning on code.
  - wahnfrieden 1y ago
    Make sure you check GPT-5.1’s from a couple days ago
hnidiots3 1y ago
Codex isn’t even a good model.
- k4rli 1y ago
  It's been praised here. However in my experience Sonnet4.5 has produced as good if not better results.
  - conception 1y ago
    What I discovered is different models are simply just better at different things and it’s very hard to predict which one will be better than the others at a certain task. Thus no one has similar experiences as no one is doing the same things the same way ever.
- 7thpower 1y ago
  Based on what? It’s been great for me.
pietz 1y ago
Since they also limited the usage of codex CLI quite a bit, this might help. I really like the gpt-5-codex model. It has the most impressive dynamic reasoning effort I've seen. Responding instantly to simple questions while thinking very long when necessary. It's also interesting how close it is in many benchmarks to gpt-5. It's not just a good coding model. It's a great agentic model.

56 points by wahnfrieden 1y ago

Looks like a leak: https://platform.openai.com/docs/models https://platform.openai.com/docs/models does not list it, and codex-mini-latest says that it's based on 4o. I wonder if it will be faster than codex; gpt-5-nano and -mini are still very slow for me on API, surprisingly so.

ChadNauseam 1y ago
I noticed the same thing with -mini. It can be even slower than the full fat version. I'm guessing their infra for it is very cost-optimized to help them offer it at such a low price
- wahnfrieden 1y ago
  They also just announced that they’re giving Pro tier prioritized access to Codex models. Are you on Pro? If not you might be getting deprioritized.
- vessenes 1y ago
  Yeah in my mind it was smaller -> faster. But seems like it might be 'a bit smaller and batched' to hit the price target.
simonw 1y ago
They announced it on Twitter yesterday: https://x.com/OpenAIDevs/status/1986861734619947305 https://x.com/OpenAIDevs/status/1986861734619947305 and https://x.com/OpenAIDevs/status/1986861736041853368 https://x.com/OpenAIDevs/status/1986861736041853368 > GPT-5-Codex-Mini allows roughly 4x more usage than GPT-5-Codex, at a slight capability tradeoff due to the more compact model. > Available in the CLI and IDE extension when you sign in with ChatGPT, with API support coming soon.

cmdtab 1y ago

If any open AI devs reading this comment section: is it possible for us to get api access at runable.com ?

bgwalter 1y ago

All "AI" providers cut corners in the models right now because the subsidized cost is unsustainable. Grok's latest update made it far worse than the version right after the Grok-4 release. It makes outright mistakes now. Copilot has cut corners long ago. Google "AI" was always horrible. The whole "AI" experiment was an outrageously expensive IP laundering parlor trick that is meeting economic realities now.

stavros 1y ago
That's a very long-winded way of saying "it was subsidized so it could capture a large market segment, and now that's stopping", which is what SV companies have done since checks notes forever.
- bgwalter 1y ago
  An LLM would have generated four pages on this topic in order to increase the token count! LLMs are advertised for serious applications. I don't recall that CPUs generally hallucinate except for the FDIV bug. Or that AirBnB rents you apartments that don't exist in 30% of all cases. Or that Uber cars drive into a river during 20% of all rides.
  - stavros 1y ago
    Are we talking about economics, or about hallucinations? "CPUs don't hallucinate" would be a reasonable argument if CPUs were an alternative to LLMs, which they aren't, so I'm not really sure what argument you're making there. Seems like you're saying "a calculator makes fewer mistakes than an accountant", which is true, but I still pay an accountant to do my taxes, and not a calculator.
    - bgwalter 1y ago
      I was obviously responding to your "SV companies have been doing that forever". You have introduced the general topic.

mrdarkies 1y ago

[flagged]

lostmsu 1y ago

GPT-5 and GPT-5-Codex are already not clever enough for anything interesting.

asadm 1y ago
not correct. are you using high reasoning? i am using codex everyday.
- pogue 1y ago
  What sort of stuff are you using it for?
  - asadm 1y ago
    computer vision things these days.
- wahnfrieden 1y ago
  Medium reportedly uses even higher reasoning than high, when it chooses to. Whereas high is fixed at a high but not as high level.
jeswin 1y ago
What's your definition of interesting? I'm half way through writing a typescript to native code translator (via .Net) compiling a large enough subset of current code with a lot of help from GPT5 and Codex CLI. It has completely blown me away. I'd like to give you a concrete example which stood out (from by now, dozens). I wanted d.ts files from the .Net Standard Libs. One immediately obvious problem is that .Net would allow classes/interfaces to be redefined if the generic type arity is different. For example, there can be SomeClass<int> and SomeClass<int, int> which are completely separate. TypeScript of course, wouldn't allow this - you can have one with all types defined, but it'd obviously be a mess. I was stuck with (quite ugly): const users = new List_1<User>(...); instead of const users = new List<User>(...); So GPT comes up with this: declare const __unspecified: unique symbol; type __ = typeof __unspecified; // Your arity-anchored delegates exist elsewhere: // import("internal/System").Action_0 // import("internal/System").Action_1<T1> // import("internal/System").Action_2<T1, T2> // import("internal/System").Action_3<T1, T2, T3> // ... up to 17 export type Action< T1 = __, T2 = __, T3 = __, // ... continue through T17 = __ > = [T1] extends [__] ? import("internal/System").Action_0 : [T2] extends [__] ? import("internal/System").Action_1<T1> : [T3] extends [__] ? import("internal/System").Action_2<T1, T2> : /* next lines follow the same pattern … */ import("internal/System").Action_3<T1, T2, T3>; This lets me write: const a: Action<number> = (n) => {}; // OK (void) const f: Func<number, string> = (s) => 20; // OK (string -> number) A human could come up with this, of course. But doing this at scale (there are many such problems which crop up), would take a lot of effort. Btw I'm using Claude for the grunt work (because its faster), but GPT5 is doing all the architecture/thinking/planning/review.

simonw 1y ago

I managed to get GPT-5-Codex-Mini to draw me a pelican. It's not a very good one! https://static.simonwillison.net/static/2025/codex-hacking-mini.png https://static.simonwillison.net/static/2025/codex-hacking-m... For comparison, here's GPT-5-Codex (not mini) https://static.simonwillison.net/static/2025/codex-hacking-default.png https://static.simonwillison.net/static/2025/codex-hacking-d... and full GPT-5: https://static.simonwillison.net/static/2025/codex-hacking-gpt-5.png https://static.simonwillison.net/static/2025/codex-hacking-g... I had quite a fun time getting those pelicans though... since GPT-5 Codex Mini isn't officially available via API yet I instead had OpenAI's Codex CLI tool extend itself (in Rust) to add a "codex prompt ..." tool which uses their existing custom auth scheme and backend API, then used that to generate the pelicans. Full details here: https://simonwillison.net/2025/Nov/9/gpt-5-codex-mini/ https://simonwillison.net/2025/Nov/9/gpt-5-codex-mini/

aurareturn 1y ago
Just curious, do you think LLM makers are deliberately adding training data for your pelican test by now?
- simonw 1y ago
  I'll know if they do, because I'll notice that a new model is suspiciously great at drawing pelicans riding bicycles while still sucking at drawing other things.
RestartKernel 1y ago
Can't believe I'm saying this, but GPT-5's pelican is its most impressive improvement over 4o I've seen. I wonder if Codex' MoE does not contain any expert fit for this task due to its fine-tuning on code.
- wahnfrieden 1y ago
  Make sure you check GPT-5.1’s from a couple days ago

hnidiots3 1y ago

Codex isn’t even a good model.

k4rli 1y ago
It's been praised here. However in my experience Sonnet4.5 has produced as good if not better results.
- conception 1y ago
  What I discovered is different models are simply just better at different things and it’s very hard to predict which one will be better than the others at a certain task. Thus no one has similar experiences as no one is doing the same things the same way ever.
7thpower 1y ago
Based on what? It’s been great for me.

pietz 1y ago

Since they also limited the usage of codex CLI quite a bit, this might help. I really like the gpt-5-codex model. It has the most impressive dynamic reasoning effort I've seen. Responding instantly to simple questions while thinking very long when necessary. It's also interesting how close it is in many benchmarks to gpt-5. It's not just a good coding model. It's a great agentic model.