A while back I compared all the different LLM’s (i.e. GPT, Claude) in various Copilot services (i.e. Chat, Cowork) here:
https://blog.ciaops.com/2026/08/17/comparing-llms-in-copilot-services-round-7-final/
The ultimate winner was:
Opus 5 (Cowork)
which cost US$22 to complete the work.
Microsoft has just announced that Fable 5.1 is available in Cowork so I took it for a spin through the same prompt I used in the recent testing. The results are here (as judged by Grok):
and the new winner is now:
Fable 5.1 (Cowork)
you can see the result for yourself here:
along with all the others outputs:
https://github.com/directorcia/general/tree/master/Copilot/Comparisons/20260816
Here is an update on the costs in Cowork for each model:
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
In summary then, the new best model, Fable 5.1, produces the best results from my standard prompt and is also the most expensive to use using that prompt.
The comparison report for all document paramteres has been updated here:
https://github.com/directorcia/general/blob/master/Copilot/Comparisons/20260816-File-paramters.md
The next updated model that we expect to see will probably be GPT 6.0 which is expected in the October timeframe if not sooner. As soon as it becomes available I’ll test it and update this information.
CIAOPS 