GPT-5.3-Codex
OpenAI’s coding specialist from early 2026, made for agents that work in a terminal.
About GPT-5.3-Codex
GPT-5.3-Codex was OpenAI’s dedicated model for Codex, its coding agent. It combined the coding of the earlier Codex model with the reasoning of GPT-5.2, and at launch scored 77.3% on Terminal-Bench 2.0 and 56.8% on SWE-Bench Pro. OpenAI says engineers used early versions of it to help debug its own training.
It always reasons, from low to extra-high effort. The general GPT-6 models have since caught up and passed it on coding, so it makes most sense where a workflow was built around it.
Where it’s strong
Coding agents that work in a terminal.
Large refactors that touch many files.
Workflows already built around Codex.
Where to be careful
A generation behind GPT-6 on agentic coding.
Its knowledge stops at August 2025, and its 400K context is smaller than current flagships’.
Price
For scale: 1,000 requests of about 3,000 tokens in and 1,000 out cost $22.14 — a long prompt and a page of answer each. Every rate is published and stays the same from one request to the next. See every model.
Specs
gpt-5.3-codexCall it
Use the OpenAI SDK you already have — point it at Roar AI and name the model. Read the docs.
from openai import OpenAI
client = OpenAI(base_url="https://api.roar-ai.com/v1", api_key="roar_live_…")
reply = client.chat.completions.create(
model="gpt-5.3-codex",
messages=[{"role": "user", "content": "Summarise this contract in plain English."}],
)Compare GPT-5.3-Codex
Questions
How much does GPT-5.3-Codex cost?
Input is $2.0125 per 1M tokens; output is $16.10 per 1M tokens. For scale, 1,000 requests of about 3,000 tokens in and 1,000 out cost $22.14. The rate is published and does not change from one request to the next.
Can I use GPT-5.3-Codex alongside other models?
Yes. Every model on Roar AI is on the same API key and the same monthly invoice, so switching from GPT-5.3-Codex to another model is a change to one word in your code.
Is GPT-5.3-Codex open source?
No. OpenAI does not publish the weights, so it is only available through an API like this one.