Closest alternatives
On price, GPT-5.6 Sol is 2.5x cheaper per input token and ties GPT-6: Astra on the independent Intelligence Index at 61. On capability at the same price, Claude Fable 5.1 currently leads both independent Artificial Analysis composites. Claude Opus 5 is half the price but has no directly comparable published benchmark against Astra.
| Model | Input $/1M | Output $/1M | Context | AA Intelligence Index |
|---|---|---|---|---|
| GPT-5.6 Sol | $4.00 | $20.00 | not published at this size | 61 |
| Claude Fable 5.1 | $10.00 | $50.00 | 1,000,000 | 66 |
| Claude Opus 5 | $5.00 | $25.00 | 1,000,000 | not published |
When not to switch
If your workload needs GPT-6: Astra's 1,050,000-token context ceiling, its specific strengths (FrontierMath, ExploitBench, BenchCAD), or its improved hallucination rate at maximum reasoning effort relative to GPT-5.6 Sol, the alternatives above do not match those specific numbers.
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When to switch
If your workload is cost-sensitive and does not depend on Astra's specific frontier strengths, GPT-5.6 Sol delivers a tied Intelligence Index score at 2.5x less per token. If independent coding and intelligence composites are the deciding factor and price parity is acceptable, Claude Fable 5.1 currently scores higher on both.