OpenAI's GPT-5 Codex
GPT‑5-Codex is a version of GPT‑5 LLM that is built specifically for agentic and interactive coding tasks
OpenAI recommends using GPT-5-Codex only for agentic and interactive coding use cases.
Here is what they’ve claimed in their launch blog post👇
It’s trained on complex, real-world engineering tasks such as building full projects from scratch, adding features and tests, debugging, performing large-scale refactors, and conducting code reviews. It’s more steerable, adheres better to AGENTS.md(opens in a new window) instructions, and produces higher-quality code—just tell it what you need without writing long instructions on style or code cleanliness.
They’ve recently started providing inference via API.
Things to keep in mind:
- It is available only in Responses API
- And it does not provide verbosity parameter.
How to get started?
You can start using this by setting the model id as gpt-5-codex
curl https://api.openai.com/v1/responses \
-H "Content-Type: application/json" \
-H "Authorization: Bearer $OPENAI_API_KEY" \
-d '{
"model": "gpt-5-codex",
"input": "Tell me a three sentence bedtime story about a unicorn."
}'
References
