Claude Fable 5.1 vs GPT-6 Astra: Same Price, One Point Apart?
Claude Fable 5.1 takes the edge on the September 2026 Artificial Analysis Intelligence Index, scoring 66 to GPT-6 Astra's 61. Both cost the same: $10 per million input tokens and $50 per million output. So this matchup comes down to what you value most, not what you pay.
Intelligence Index: the scoreboard
The index is the cleanest head-to-head number we have for these two. Claude Fable 5.1's 66 is the top score in the supplied snapshot, and it beats GPT-6 Astra by five points. That's a meaningful gap, not a rounding error. If your work is heavy on reasoning or general knowledge, Fable 5.1 looks like the smarter bet at the same price.
Coding: Astra's strong suit
GPT-6 Astra doesn't have a Fable 5.1 comparison in the DeepSWE benchmark from this snapshot, but it posts a strong 74.1% there, just ahead of Gemini 3.8 Flash's 73.8%. We can't say Fable 5.1 would score lower, because it wasn't included in that test. Still, if software engineering is your main workload, Astra has a proven, current coding result, and that's worth more than an index lead in a different category.
Price: a tie that favors the winner
No cost angle separates these two: both are $10 in, $50 out. So the cheaper option isn't a factor. That makes the benchmark scores even more important. Same dollar, different results, with Claude Fable 5.1 ahead on the index and GPT-6 Astra holding a visible coding credential.
Verdict: which one should you pick?
Pick Claude Fable 5.1 if you want the higher overall intelligence score at the same price, especially for general reasoning and complex tasks. Pick GPT-6 Astra if coding is your priority, because its 74.1% DeepSWE result gives you a concrete, recent signal where Fable 5.1 hasn't been tested in this snapshot.