GPT-5.4 is not supported when using Codex with a ChatGPT account

ChatGPT Support
1

I went to the official pricing website (cannot insert link here) and then clicked on “Get Plus”
This is listed as features:
Codex on the web, in the CLI, in the IDE extension, and on iOS

  1. Cloud-based integrations like automatic code review and Slack integration
  2. The latest models, including GPT-5.5, GPT-5.4, and GPT-5.4 mini
  3. GPT-5.4 mini for higher usage limits on routine local messages
  4. Flexibly extend usage with ChatGPT credits
  5. Other ChatGPT features as part of the Plus plan

I downloaded the Codex GUI Client and choose GPT-5.4 .. Prompt is fired. Feedback is:

“The ‘gpt-5.4’ model is not supported when using Codex with a ChatGPT account.”

Why?

2

Welcome to the community, @Mo9 !

Recently, OpenAI removed some earlier models from ChatGPT / Codex.

You can still access those models via the API, though, I’m pretty sure.

However, 5.4 should be available? Do any of the models work for you?

Again, good to have you with us.

3

Hi @PaulBellow Yes according to the subscription page 5.4 should be available. It is listed as model and I can select it but as soon as I try to fire a prompt the request is rejected with the mentioned error message. Doesnt matter which codex client Im using, the request is rejected.
GPT 5.5 works. But its way more expensive. So Im forced to use the expensive option. Is that on purpose?..

API key might work but I dont want to setup an agent environment with API key, I want to use the Codex agent /Cli/GUI.

4

In Codex CLI, when you type /model what list do you get?

5

Select Model and Effort
Access legacy models by running codex -m <model_name> or in your config.toml

  1. gpt-5.5 (default) Frontier model for complex coding, research, and real-world work.
    › 2. gpt-5.4 (current) Strong model for everyday coding.
  2. gpt-5.4-mini Small, fast, and cost-efficient model for simpler coding tasks.
6

more details:

╭──────────────────────────────────────────────╮
│ >_ OpenAI Codex (v0.139.0) │
│ │
│ model: gpt-5.4 medium /model to change │
│ directory: D:\github\cockpit │
╰──────────────────────────────────────────────╯

Tip: New Use /fast to enable our fastest inference with increased plan usage.

› test

■ {“type”:“error”,“status”:400,“error”:{“type”:“invalid_request_error”,“message”:“The ‘gpt-5.4’ model is not supported
when using Codex with a ChatGPT account.”}}

7

Hi,

I am using Codex through ChatGPT and I can see GPT-5.4 in model picker.

IMG_4062
IMG_40621170×487 26.2 KB

8

Ok so you can select it, but then you get an error.

That’s definitely not right!

Thanks for the report.

Hopefully staff see this.

9

Hi I can see it too but any request with it is rejected

10

Thanks, all!

No promises, but I’ve passed this along to get some eyes on it.

Appreciate you reporting, @Mo9, and hope you stick around. We’ve got a wealth of information and a great group of people here!

11

As mentioned, that doesn’t sound right, because I can’t reproduce the error​:thinking:

12

Inside Codex GUI Client I see this

Plus plan
(€23/mo)
Expanded Codex usage, GPT-5.5 Thinking

So it seems like I got kinda scammed…

On top of that I was running out of credits already after 5 prompts…This is so weird.

I dont think I will stay with Codex…

13

I don’t believe that is the case. There is a logical explanation here even if it’s a bug of some kind or an inconsistency with the documentation.

Unfortunately, for serious Codex use a Pro account is recommended.

Of late rate limits have been significantly tightened as quotas have been reduced to better reflect cost of inference.

Though of course you can use an API account instead and pay as you go …