Models
Choose the right ChatGPT and Codex model for your work, speed, cost, and reasoning needs.
Choose a model
ChatGPT desktop app
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 to accelerate complex work, making it useful for larger tasks that can be split across subagents.
ChatGPT Work on the web
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 to accelerate complex work, making it useful for larger tasks that can be split across subagents.
Codex CLI
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:
codex --model gpt-5.6The same option works with non-interactive runs. For example:
codex exec -m gpt-5.6 "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 to accelerate complex work, making it useful for larger tasks that can be split across subagents.
Codex IDE extension
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 to accelerate complex work, making it useful for larger tasks that can be split across subagents.
Recommended models
gpt-5.6-sol
Flagship GPT-5.6 model with the strongest capability for complex coding, computer use, research, and cybersecurity.
Available in: ChatGPT desktop app, ChatGPT web, Codex CLI, Codex IDE extension, Codex cloud, ChatGPT Credits, API Access.
gpt-5.6-terra
Balanced GPT-5.6 model for everyday work, with performance competitive with GPT-5.5 at a lower cost.
Available in: ChatGPT desktop app, ChatGPT web, Codex CLI, Codex IDE extension, ChatGPT Credits, API Access.
Not available in: Codex cloud.
gpt-5.6-luna
Fast and affordable GPT-5.6 model that delivers strong capability at the lowest cost in the family.
Available in: ChatGPT desktop app, ChatGPT web, Codex CLI, Codex IDE extension, ChatGPT Credits, API Access.
Not available in: Codex cloud.
gpt-5.3-codex-spark
Text-only research preview model optimized for near-instant, real-time coding iteration. Available to ChatGPT Pro users.
Available in: ChatGPT desktop app, Codex CLI, Codex IDE extension.
Not available in: ChatGPT web, Codex cloud, ChatGPT Credits, API Access.
Choosing Sol, Terra, and Luna
Codex offers three GPT-5.6 models: Sol for detail and polish, Terra as the everyday workhorse, and Luna for clear, repeatable work. If you are unsure, start with Sol.
Where each model shines
- Sol, for complex, open-ended work. Choose Sol for ambiguous, difficult, or high-value tasks that need extra analysis, judgment, or polish, such as complex code changes, deep research, or polished documents. For narrower tasks, define what done looks like to keep the work focused.
- Terra, the pragmatic all-rounder. Choose Terra for everyday work that needs strong reasoning and tool use when you do not need Sol's full depth. It is a natural starting point for work you previously gave GPT-5.5.
- 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
Use the lowest reasoning effort that produces the result you need. Increase it 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.
There is no exact mapping from GPT-5.5 reasoning efforts to GPT-5.6. 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 your options, you'll have to enable it in your app settings.
Ultra uses 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.
If Ultra doesn't appear in the desktop app's model slider, go to Settings > Configuration, then turn on Ultra in model picker slider.
Other models
When you sign in with ChatGPT, Codex works best with the recommended models listed above.
View other models
gpt-5.5
Previous-generation frontier model for complex coding, computer use, knowledge work, and research workflows.
Available in: ChatGPT desktop app, ChatGPT web, Codex CLI, Codex IDE extension, ChatGPT Credits, API Access.
Not available in: Codex cloud.
gpt-5.4
Frontier model for professional work with strong coding, reasoning, tool use, and agentic workflow capabilities.
Available in: ChatGPT desktop app, ChatGPT web, Codex CLI, Codex IDE extension, ChatGPT Credits, API Access.
Not available in: Codex cloud.
gpt-5.4-mini
Fast, efficient mini model for responsive coding tasks and subagents.
Available in: ChatGPT desktop app, ChatGPT web, Codex CLI, Codex IDE extension, ChatGPT Credits, API Access.
Not available in: Codex cloud.
You can also point Codex at any model and provider that supports either the Chat Completions or Responses APIs to fit your specific use case.
Deprecated Codex models
The gpt-5.4 and gpt-5.4-mini models retire from Codex with ChatGPT sign-in on August 31, 2026. Replace gpt-5.4 with gpt-5.6-terra and gpt-5.4-mini with gpt-5.6-luna in workspace defaults, saved model settings, managed configurations, custom agents, and scheduled tasks.
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.
Configure your default local model
The ChatGPT desktop app, Codex CLI, and IDE extension use the same config.toml
configuration file. 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.
model = "gpt-5.6"Choose a model for cloud chats
Currently, you can't change the default model for Codex cloud chats.