GPT-6 Astra vs Opus 5.5: Which AI Model to Use for Each Job
TL;DR
GPT-6 Astra costs two and a half times more than Claude Opus 5.5 per token, but the pricier model is not better at everything. In a YouTube website test, Opus 5.5 scored higher. Astra leads on hard math and science. The simple plan: use Opus 5.5 in Claude Code for websites, apps and code, and save GPT-6 Astra for hard math and science.
👉 https://www.skool.com/claudecodeclub
GPT-6 Astra vs Opus 5.5: two new models, 19 days apart
OpenAI released GPT-6 Astra on September 4, 2026. Anthropic released Claude Opus 5.5 on September 22. A reel by Phani K comparing the two got 612,900 views in two days, because everyone wants to know which one to pay for.
What each model costs
- GPT-6 Astra: $10 per million input tokens and $50 per million output tokens.
- Claude Opus 5.5: $4 per million input tokens and $20 per million output tokens.
- The gap: GPT-6 Astra costs 2.5 times more per token. A token is a small piece of a word that the AI reads or writes.
The fine print: the price per token is not the price per job. Each model can use more or fewer tokens depending on its effort setting, so test your own work before you decide.
Which model builds the better website
The YouTuber Code Bear gave both models the same hotel website brief, one in Claude Code and one in Codex. The final score out of 90 was 83.5 for Opus 5.5 and 76.5 for GPT-6 Astra.
Vellum's tests point the same way for code. On Terminal-Bench 4.0, which tests running commands and fixing build errors, Opus 5.5 scored 66.4% and GPT-6 Astra scored 57.7%.
Where GPT-6 Astra wins
GPT-6 Astra leads on hard math and science. On FrontierMath Tier 4, a set of very hard math problems, Vellum reports 97.6% for Astra against 73.2% for Opus 5. On Terminal-Bench Science, Astra scored 64.6% and Opus 5.5 scored 58.7%.
The plan: split the work between the two models
- Websites, apps and code: use Opus 5.5 in Claude Code.
- Hard math and science: use GPT-6 Astra.
- Everything in between: start with Opus 5.5 because it costs less, and switch only if the answer is not good enough.
Prompts to try:
promptBuild a one-page website for [my business]. Use a clean layout, a hero section, three sections about what I offer, and a contact form. Explain each file you make in one sentence.promptI do [my kind of work]. List the 5 jobs I do most often and tell me which ones are coding or building jobs and which ones are hard math or science jobs, so I know which AI model to use for each.👉 https://www.skool.com/claudecodeclub
Common questions
Is GPT-6 Astra better than Opus 5.5?
Not for everything. GPT-6 Astra leads on hard math and science. Opus 5.5 scored higher in Code Bear's website test and on Terminal-Bench 4.0, so it is the better pick for building.
How much more does GPT-6 Astra cost than Opus 5.5?
On list price, 2.5 times more. GPT-6 Astra is $10 per million input tokens and $50 per million output tokens. Opus 5.5 is $4 and $20.
Which model should I use in Claude Code?
Opus 5.5, because it is Anthropic's model and it scored higher on code and website tests.
Does the cheaper price per token mean a cheaper job?
Not always. The cost of a job also depends on how many tokens the model uses, so check your own jobs.
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