GPT-5.3-Codex vs Claude Sonnet 5.5
Codex was OpenAI’s coding specialist in early 2026; Sonnet 5.5 is a newer general model that codes better on most current tests. Stay on Codex only if a workflow was built around it.
Choose GPT-5.3-Codex if
- Your coding workflow was built and tested on Codex.
- Terminal agents tuned to Codex’s behaviour.
- Large refactors in an established set-up.
Choose Claude Sonnet 5.5 if
- New coding work — Sonnet 5.5 is a generation newer.
- A million-token context against Codex’s 400K.
- Writing documents and slides alongside code.
Side by side
| GPT-5.3-Codex | Claude Sonnet 5.5 | |
|---|---|---|
| Made by | OpenAI | Anthropic |
| Released | February 2026 | September 2026 |
| Input price, per 1M tokens | $2.0125 | $2.30 |
| Output price, per 1M tokens | $16.10 | $11.50 |
| Cached input, per 1M tokens | $0.2013 | $0.23 |
| Batch (about half price) | No | Yes |
| Context window | 400K tokens | 1M tokens |
| Longest answer | 128K tokens | 128K tokens |
| Reads | Text, Images | Text, Images, PDFs |
| Thinks before answering | Always on | Yes, adjustable |
| Open weights | No | No |
| Runs in Sri Lanka | No | No |
Prices are Roar AI’s published rates, live from our price list. Specs are each lab’s own published figures.
What a real job costs
Take 1,000 requests, each about 3,000 tokens in and 1,000 out — a long prompt and a page of answer.
Claude Sonnet 5.5 does the same job for 1.2× less. Models that think before answering spend extra output tokens doing it, so on hard prompts the real gap can be wider than the rates suggest.
Use both, switch any time
On Roar AI both are on the same key and the same monthly invoice. Trying the other one is a one-word change:
client.chat.completions.create(model="gpt-5.3-codex", …) client.chat.completions.create(model="claude-sonnet-5-5", …)
Send the same prompts to both for a day and compare the answers on your own work — that settles it faster than any benchmark. Read the docs.