Recommended models
OpenAI's newest frontier model for complex coding, computer use, knowledge work, and research workflows in Codex.
Flagship frontier model for professional work that brings the industry-leading coding capabilities of GPT-5.3-Codex together with stronger reasoning, tool use, and agentic workflows.
Fast, efficient mini model for responsive coding tasks and subagents.
Industry-leading coding model for complex software engineering. Its coding capabilities now also power GPT-5.4.
Text-only research preview model optimized for near-instant, real-time coding iteration. Available to ChatGPT Pro users.
For most tasks in Codex, start with gpt-5.5 when it appears in your model
picker. It is strongest for complex coding, computer use, knowledge work, and
research workflows. GPT-5.5 is currently available in Codex when you sign in
with ChatGPT; it isn’t available with API-key authentication. During the
rollout, continue using gpt-5.4 if gpt-5.5 is not yet available. Use
gpt-5.4-mini when you want a faster, lower-cost option for lighter coding
tasks or subagents. The gpt-5.3-codex-spark model is available in research
preview for ChatGPT Pro subscribers and is optimized for near-instant,
real-time coding iteration.
Alternative models
Previous general-purpose model for coding and agentic tasks, including hard debugging tasks that benefit from deeper deliberation.
Other models
When you sign in with ChatGPT, Codex works best with the models listed above.
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.
Support for the Chat Completions API is deprecated and will be removed in future releases of Codex.
Configuring models
Configure your default local model
The 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 Codex app, CLI, or IDE Extension defaults to a recommended model.
model = "gpt-5.5"If gpt-5.5 isn’t available in your account yet, use gpt-5.4.
Choosing a different local model temporarily
In the Codex CLI, you can use the /model command during an active thread to change the model. In the IDE extension, you can use the model selector below the input box to choose your model.
To start a new Codex CLI thread with a specific model or to specify the model for codex exec you can use the --model/-m flag:
codex -m gpt-5.5Choosing your model for cloud tasks
Currently, you can’t change the default model for Codex cloud tasks.