# Models

> For the complete documentation index, see [llms.txt](https://learn.chatgpt.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to the page URL.

## GPT-5.5 retirement

On October 14, 2026, GPT-5.5 will retire from ChatGPT, ChatGPT Work, and Codex
on all plans, including consumer, Business, Enterprise, and Edu plans. This
retirement does not apply to the OpenAI API.

If you use Codex with ChatGPT sign-in, choose an available replacement before
October 14:

- On Plus, Pro, Business, Enterprise, and Edu plans, choose **GPT-6 Sol**
  (`gpt-6-sol`) when available.
- On Free and Go plans, choose **GPT-6 Luna** (`gpt-6-luna`) in the desktop app
  when available.

Replace `gpt-5.5` in workspace defaults, saved model settings, managed
configurations, custom agents, scheduled tasks, and scripts that select a model.

See [workspace model availability](https://learn.chatgpt.com/docs/enterprise/workspace-model-availability#prepare-for-the-gpt-55-retirement)
for administrator guidance.

<ContentModeSwitch group="codex-surface" id="app">



  


## Choose a model

In Work or Codex in the ChatGPT desktop app, use the model and reasoning control
beneath the composer to choose an available model and adjust its reasoning effort.

Higher reasoning effort can improve results for complex tasks, but it takes
longer and uses more tokens. Start with the default effort and increase it when
the task needs deeper planning or analysis.

**Ultra** mode goes
beyond a single-agent run. It uses
[subagents](https://learn.chatgpt.com/docs/agent-configuration/subagents) to accelerate complex work,
making it useful for larger tasks that can be split across subagents.

  

  <CodexModelSwitcher client:visible className="lg:mt-7" />



</ContentModeSwitch>

<ContentModeSwitch group="codex-surface" id="web">



  


## Choose a model

These recommendations apply to **ChatGPT Work** on the web. Use the
model and reasoning control beneath the composer to choose an available model
and adjust its reasoning effort.

Higher reasoning effort can improve results for complex tasks, but it takes
longer and uses more tokens. Start with the default effort and increase it when
the task needs deeper planning or analysis.

**Ultra** mode goes
beyond a single-agent run. It uses
[subagents](https://learn.chatgpt.com/docs/agent-configuration/subagents) to accelerate complex work,
making it useful for larger tasks that can be split across subagents.

  

  <CodexModelSwitcher client:visible className="lg:mt-7" />



</ContentModeSwitch>

<ContentModeSwitch group="codex-surface" id="cli">

## Choose a model

In an interactive CLI session, use `/model` to switch models or adjust
reasoning effort. You can also choose a model when you launch Codex with
`--model` or its `-m` alias:

```bash
codex --model gpt-6.1-sol
```


The same option works with non-interactive runs. For example:

```bash
codex exec -m gpt-6.1-sol "Review the current changes"
```


Higher reasoning effort can improve results for complex tasks, but it takes
longer and uses more tokens. Start with the default effort and increase it when
the task needs deeper planning or analysis.

**Ultra** mode goes
beyond a single-agent run. It uses
[subagents](https://learn.chatgpt.com/docs/agent-configuration/subagents) to accelerate complex work,
making it useful for larger tasks that can be split across subagents.

</ContentModeSwitch>

<ContentModeSwitch group="codex-surface" id="ide">



  


## Choose a model

Use the model switcher below the composer to choose an available model and
reasoning effort.

Higher reasoning effort can improve results for complex tasks, but it takes
longer and uses more tokens. Start with the default effort and increase it when
the task needs deeper planning or analysis.

**Ultra** mode goes
beyond a single-agent run. It uses
[subagents](https://learn.chatgpt.com/docs/agent-configuration/subagents) to accelerate complex work,
making it useful for larger tasks that can be split across subagents.

  

  <CodexModelSwitcher client:visible forceDark className="lg:mt-7" />



</ContentModeSwitch>

<a id="recommended-models"></a>
<a id="other-models"></a>
<a id="deprecated-codex-models"></a>
<a id="configure-your-default-local-model"></a>
<a id="choose-a-model-for-cloud-tasks"></a>
<a id="gpt-6-astra"></a>

<ContentModeSwitch group="codex-surface" ids="app,web,cli,ide">

## Recommended models

For complex coding and agentic workflows, use GPT-6.1 Sol when available to your
account and client. Use Luna for focused, repeatable tasks. Select `gpt-6.1-sol`
or `gpt-6-luna` in your model picker or saved configuration when available.

GPT-6.1 Sol offers near-Astra performance for complex work at a lower cost
than Astra. See [GPT-6.1 Sol](#gpt-61-sol) for its separate rollout.

In ChatGPT, GPT-6.1 Sol, GPT-6 Sol, and GPT-6 Luna are available in Work and
Codex. They aren't available in Chat.

GPT-5.6 Sol, GPT-5.6 Terra, and GPT-5.6 Luna remain available during the rollout. Selecting a
new model doesn't change workspace permissions or grant access to it.

For Ultrafast mode availability and credit usage on Pro $500 and eligible
Enterprise and Edu plans, see [Speed](https://learn.chatgpt.com/docs/agent-configuration/speed#ultrafast-mode).

<a id="app-compare-models"></a>



  <ModelDetails
    client:load
    name="gpt-6-astra"
    slug="gpt-6-astra"
    imageLabel="Astra"
    wallpaperUrl="/images/api/models/gpt-6-astra-texture.webp"
    description="Our most capable model for complex work across code, apps, and research, combining advanced reasoning, computer use, and stronger judgment."
    data={{
      features: [
        {
          title: "Capability",
          value: "",
          icons: [
            "openai.SparklesFilled",
            "openai.SparklesFilled",
            "openai.SparklesFilled",
            "openai.SparklesFilled",
            "openai.SparklesFilled",
          ],
        },
        {
          title: "Speed",
          value: "",
          icons: ["openai.Flash", "openai.Flash"],
        },
        { title: "ChatGPT desktop app", value: true },
        { title: "ChatGPT web", value: true },
        { title: "Codex CLI", value: true },
        { title: "Codex IDE extension", value: true },
        { title: "ChatGPT Credits", value: true },
        { title: "API Access", value: true },
      ],
    }}
  />

<ModelDetails
  client:load
  name="gpt-6.1-sol"
  slug="gpt-6.1-sol"
  imageLabel="6.1 Sol"
  wallpaperUrl="/images/api/models/gpt-6.1-sol-texture.webp"
  description="Near-Astra performance for complex work at a lower cost than Astra. Consider it for repeated, long-running work across code, apps, and documents."
  data={{
    features: [
      {
        title: "Capability",
        value: "",
        icons: [
          "openai.SparklesFilled",
          "openai.SparklesFilled",
          "openai.SparklesFilled",
          "openai.SparklesFilled",
          "openai.SparklesFilled",
        ],
      },
      {
        title: "Speed",
        value: "",
        icons: ["openai.Flash", "openai.Flash", "openai.Flash"],
      },
      { title: "Work and Codex in the desktop app", value: true },
      { title: "ChatGPT Work on the web", value: true },
      { title: "Codex CLI", value: true },
      { title: "Codex IDE extension", value: true },
      { title: "ChatGPT Credits", value: true },
      { title: "API Access", value: true },
    ],
  }}
/>

<ModelDetails
  client:load
  name="gpt-6-luna"
  slug="gpt-6-luna"
  imageLabel="6 Luna"
  wallpaperUrl="/images/api/models/gpt-5.6-luna.webp"
  description="Our most efficient model for focused, high-volume tasks, including summarization, extraction, and focused coding."
  data={{
    features: [
      {
        title: "Capability",
        value: "",
        icons: [
          "openai.SparklesFilled",
          "openai.SparklesFilled",
          "openai.SparklesFilled",
        ],
      },
      {
        title: "Speed",
        value: "",
        icons: ["openai.Flash", "openai.Flash", "openai.Flash", "openai.Flash"],
      },
      { title: "Work and Codex in the desktop app", value: true },
      { title: "ChatGPT Work on the web", value: true },
      { title: "Codex CLI", value: true },
      { title: "Codex IDE extension", value: true },
      { title: "ChatGPT Credits", value: true },
      { title: "API Access", value: true },
    ],
  }}
/>




Availability depends on the rollout, your sign-in method, and your client.
See [pricing](https://learn.chatgpt.com/docs/pricing) for plan access and usage, and
[workspace model availability](https://learn.chatgpt.com/docs/enterprise/workspace-model-availability)
for Enterprise access.

</ContentModeSwitch>

<a id="gpt-6.1-sol"></a>

### GPT-6.1 Sol

The GPT-6.1 Sol launch rollout includes Plus, Pro, Business, Enterprise, and Edu
in Codex in the desktop app and CLI, and ChatGPT Work on the web and mobile.
For Enterprise and Edu, the plan keeps GPT-6.1 Sol off by default until an
administrator enables it.
Free and Go are not included at launch.

Standard and Fast modes are available where supported. Ultrafast is available
on Pro $500 and eligible Enterprise and Edu plans. See
[Ultrafast mode](https://learn.chatgpt.com/docs/agent-configuration/speed#ultrafast-mode) for plan and
workspace requirements.

Use `gpt-6.1-sol`. Available controls depend on your plan, client, and workspace
settings.
Reasoning effort ranges from Light to Ultra. Max and Ultra depend on your settings.

See [pricing](https://learn.chatgpt.com/docs/pricing) for credit usage and
[model selection](https://developers.openai.com/api/docs/guides/model-selection#when-to-consider-gpt-61-sol)
for guidance on comparing it with Astra and Luna. To see how its API
specifications differ from the previous Sol model, [compare GPT-6.1 Sol and
GPT-6 Sol](https://developers.openai.com/api/docs/models/compare?model=gpt-6.1-sol&model2=gpt-6-sol).

In the ChatGPT desktop app and ChatGPT Work on the web, start with the default
  Power setting available to your account. Move toward **Smarter** for deeper
  reasoning or **Faster** for faster, lower-cost work. Open **Advanced** to
  choose a specific model, reasoning effort, or speed.

<ContentModeSwitch group="codex-surface" ids="app,web,cli,ide">

<ContentModeSwitch group="codex-surface" ids="app,web">

The six Power presets shown are Luna High, GPT-6 Sol Light (selected
in this example), GPT-6 Sol Medium, Astra Light, Astra Medium, and Astra Extra
High. Some paid plans omit Astra Extra High. Advanced controls are illustrative;
available options and defaults vary by plan, client, workspace settings, and rollout.

</ContentModeSwitch>

<a id="choosing-sol-terra-and-luna"></a>

<a id="choosing-astra-sol-and-luna"></a>
<a id="app-choosing-astra-sol-and-luna"></a>
<a id="web-choosing-astra-sol-and-luna"></a>
<a id="cli-choosing-astra-sol-and-luna"></a>
<a id="ide-choosing-astra-sol-and-luna"></a>

## Choosing a model

Choose **Astra** when a task needs the strongest capability across steps and
tools. **GPT-6.1 Sol** offers near-Astra performance at a lower cost
than Astra. Use **GPT-6.1 Sol** when available to your account and client, and
**Luna** for clear, repeatable tasks.

### Where each model shines

- **Astra, for the hardest end-to-end work.** Choose Astra for complete workflows
  across code, apps, and research that need sustained reasoning and judgment.
  Give it the sources, templates, constraints, and checks that define a useful
  result. Astra is better at asking focused questions and incorporating your
  guidance while keeping the original goal and constraints in view.
- **GPT-6.1 Sol, for repeated, long-running work.** Consider GPT-6.1 Sol for
  work across code, apps, and documents when cost matters. Keep Astra for your
  most demanding work.
- **Luna, for clear, repeatable tasks.** Choose Luna for specific, high-volume
  tasks when you know what a good result looks like, such as extraction,
  classification, transformation, and structured summaries.

### Pick a reasoning effort

For GPT-6.1 Sol, start with the reasoning effort available by default in your
client and adjust based on the task. Start with **High** for Luna or **Light**
for Astra.
In configuration, Astra's Light setting is `low`. Increase the effort for tasks
that need more planning, analysis, or checking.

- **Light** in the ChatGPT desktop app, ChatGPT Work on the web, and IDE extension, or **Low** in the
  CLI, suits quick, well-scoped tasks.
- **Medium** balances speed and depth for tasks that need more planning.
- **High** and **Extra High** suit difficult work with multiple steps, sources,
  or tradeoffs.

Reasoning efforts don't map exactly between model generations. Try a familiar task
at a lower setting and adjust based on the result.

### Know when to use Max or Ultra

**Max** gives the selected model more time to reason about a single task. Use it
for the hardest problems, when depth matters more than speed or usage. If you
don't see Max in the ChatGPT desktop app, check your app settings.

**Ultra** uses [subagents](https://learn.chatgpt.com/docs/agent-configuration/subagents) to handle
separate parts of a complex task in parallel. Choose it when you can divide the
work into meaningful parts. Most tasks do not need Max or Ultra.

GPT-6 Luna supports reasoning efforts up to **Max**, but not **Ultra**.

In the CLI, use `/model`, choose a model, then select **More reasoning…**
to see its supported Max or Ultra options.

If your model supports Ultra but it doesn't appear in the desktop app's model
slider, go to **Settings** > **Configuration**, then turn on
**Ultra in model picker slider**.

</ContentModeSwitch>

<ContentModeSwitch group="codex-surface" ids="app,cli,ide">

## Other models

When you sign in with ChatGPT, Codex works best with the recommended models listed above.

<ToggleSection title="View other models">
  

    <ModelDetails
      client:load
      name="gpt-5.5"
      slug="gpt-5.5"
      imageLabel="5.5"
      wallpaperUrl="/images/api/models/gpt-5.5.jpg"
      description="Previous-generation flagship model. Retires from ChatGPT, ChatGPT Work, and Codex on October 14, 2026; remains available on the OpenAI API."
      data={{
        features: [
          {
            title: "Capability",
            value: "",
            icons: [
              "openai.SparklesFilled",
              "openai.SparklesFilled",
              "openai.SparklesFilled",
              "openai.SparklesFilled",
            ],
          },
          {
            title: "Speed",
            value: "",
            icons: ["openai.Flash", "openai.Flash", "openai.Flash"],
          },
          { title: "ChatGPT desktop app", value: true },
          { title: "ChatGPT web", value: true },
          { title: "Codex CLI", value: true },
          { title: "Codex IDE extension", value: true },
          { title: "ChatGPT Credits", value: true },
          { title: "API Access", value: true },
        ],
      }}
    />

  

</ToggleSection>

For a custom model provider or gateway, use a compatible Responses API endpoint.
See [Custom model providers](https://learn.chatgpt.com/docs/config-file/config-advanced#custom-model-providers)
for configuration and [Gateway compatibility](https://learn.chatgpt.com/docs/enterprise/gateway-compatibility)
for streaming, tool, and conversation requirements. Current Codex releases don't
support `wire_api = "chat"` or a Chat Completions-only endpoint.

## Deprecated Codex models

GPT-5.3-Codex-Spark retired on September 14, 2026, and is no longer available
in the ChatGPT desktop app, Codex CLI, or IDE extension. Update saved
configurations, custom agents, and scripts that select `gpt-5.3-codex-spark`
to use an [available model](https://learn.chatgpt.com/docs/models#recommended-models). See the
[Spark retirement notice](https://learn.chatgpt.com/docs/changelog#codex-2026-09-14-codex-spark-deprecation).

GPT-5.5 retires from Codex with ChatGPT sign-in on October 14, 2026. Replace
`gpt-5.5` with a model available to your account and client. See
[GPT-5.5 retirement](https://learn.chatgpt.com/docs/models#gpt-55-retirement) for plan-specific
replacements and the migration checklist.

The `gpt-5.4` and `gpt-5.4-mini` models retired from Codex with ChatGPT sign-in
on August 31, 2026. Replace `gpt-5.4` with `gpt-6-sol` and
`gpt-5.4-mini` with `gpt-6-luna` when available to your plan and client.
In Enterprise and Edu, an administrator must enable Luna first. Update workspace
defaults, saved model settings, managed configurations, custom agents, and
scheduled tasks with an available replacement.

The `gpt-5.2` and `gpt-5.3-codex` models are already deprecated in Codex when
you sign in with ChatGPT. Update scripts, configuration files, and
`codex exec --model` commands that still reference those models.

The OpenAI API and Codex authenticated with your own API key aren't affected
by the GPT-5.4 retirement. For current API model availability, see the
[API models page](https://developers.openai.com/api/docs/models).

## Configure your default local model

The ChatGPT desktop app, Codex CLI, and IDE extension use the same `config.toml`
[configuration file](https://learn.chatgpt.com/docs/config-file/config-basic). To specify a model, add a
`model` entry to your configuration file. If you don't specify a model, the
ChatGPT desktop app, Codex CLI, or IDE extension uses a recommended model.

```toml
model = "gpt-6.1-sol"
```


</ContentModeSwitch>