In the last round of the Copilot LLM challenge Fable 5.1 came out on top. You can find that here:
https://blog.ciaops.com/2026/09/02/we-have-a-new-llm-in-copilot-winner/
That was then and this is now. Less than a month later a new model from OpenAI, GPT 6 Astra has become available in Copilot (Cowork specifically). I therefore pitted Astra 6 against the reigning champion Fable 5.1. The result is, unsurprisingly, that we have a new winner:
GPT 6 Astra
and you can see the results for yourself here:
https://github.com/directorcia/general/blob/master/Copilot/Comparisons/20260917-Cowork-Grok-eval.md
with all the outputs here:
https://github.com/directorcia/general/tree/master/Copilot/Comparisons/20260816
Interestingly, there was only a small improvement last time when Fable 5.1 pipped Opus 5 by 8.7 to 8.5 in the overall score. This time however Astra won by a significant margin of 9.03 to 8.30.
Again, not unsurprisingly, where Astra lost out was on cost, almost doubling the cost of Fable 5.1 as you can see:
Astra 6 = 6,067 credits
Fable 5.1 = 3,453 credits
Fable 5 (Preview) = 3,387 credits [Model no longer shown]
Fable 5 (Copilot)(Preview) = 3,373.8 credits [Model no longer shown]
GPT 5.6 Sol = 2,800.50 credits
Sonnet 5 = 2,509.3 credits
Opus 4.8 = 2,487 credits [Model no longer shown]
Opus 5 = 2,240 credits
GPT 5.5 = 1,200 credits
GPT 5.6 Terra = 260 credits
So the latest model is the best (unsurprising). The latest model is also the most expensive (unsurprising).
I have also updated the summary report for all the documents created by the different models here:
https://github.com/directorcia/general/blob/master/Copilot/Comparisons/20260816-File-paramters.md
I’m sure there will be more model releases coming soon but my rudimentary testing certainly indicates they are improving, if somewhat more expensive each time.
CIAOPS 