A while back I compared the different LLMs in Copilot, and Fable 5.1 took the honours in Cowork:
https://blog.ciaops.com/2026/09/02/we-have-a-new-llm-in-copilot-winner/
GPT 6 Astra later took the trophy, and I then ran Opus 5.5 against it:
https://blog.ciaops.com/2026/09/17/astra-takes-the-trophy/
https://blog.ciaops.com/2026/09/23/i-think-we-need-a-count-back/
I have now put the latest LLM in Copilot through the same prompt in Cowork, judged again by Grok. First I compared Fable 5.2 with the September Fable 5.1 report. The results are here:
and Fable 5.2 (Cowork) is ahead, 8.7 to 8.1. It was stronger on argument, evidence and presentation. Depth was roughly even.
I then put that November Fable 5.2 report against Opus 5.5. That evaluation is here:
and the winner of that head-to-head is now:
Opus 5.5 (Cowork)
The scores are close: 8.9 against 8.6. Argument was a tie at 9.0 each. Opus 5.5 was stronger on evidence (9.2 vs 8.3) and detail (9.3 vs 8.4). Fable 5.2 was the more polished, executive-friendly read (9.0 vs 8.0). Both reports reach much the same strategic conclusions. The gap is in how tightly the evidence is handled, not in a different industry story. Opus 5.5’s research cut-off was earlier (23 September against 11 November), so Fable 5.2 had some later data and still came second.
You can see the Fable 5.2 output here:
and the Opus 5.5 output here:
along with the other outputs:
https://github.com/directorcia/general/tree/master/Copilot/Comparisons/20260816
These two evaluations don’t include credit costs, so I am not going to invent a new price list. They also don’t re-run Astra, so this is not a new overall series winner. For this latest LLM in Copilot pairing, though, Opus 5.5 edges Fable 5.2, after Fable 5.2 had already improved on Fable 5.1.
As soon as the next model turns up in Cowork, I’ll test it and update this information.
