Claude Opus 5.5 vs Claude Fable 5.1
API pricing, benchmark indices and specs — updated 19 October 2026.
anthropic · A · API-only
Input / 1M
$4.00
Output / 1M
$20.00
AA index
57.6
proprietary · 1M context
anthropic · B · API-only
Input / 1M
$10.00
Output / 1M
$50.00
AA index
53.4
proprietary · 1M context
Specification comparison
Differences are highlighted; identical values are muted.
| Specification | Claude Opus 5.5 | Claude Fable 5.1 |
|---|---|---|
| Deployment | API-only (closed weights) | API-only (closed weights) |
| Parameters | n/a — API-only | n/a — API-only |
| Architecture | n/a — API-only | n/a — API-only |
| Context length | 1,000,000 | 1,000,000 |
| Licence | Proprietary | Proprietary |
| Commercial use | Per API terms | Per API terms |
| Languages | n/a — API-only | n/a — API-only |
| Downloads 30d | n/a — API-only | n/a — API-only |
| Downloads all time | n/a — API-only | n/a — API-only |
| Quantizations on the Hub | n/a — API-only | n/a — API-only |
| Gated | n/a — API-only | n/a — API-only |
| First seen on the Hub | n/a — API-only | n/a — API-only |
| API input price / 1M tokens | $4.00 | $10.00 |
| API output price / 1M tokens | $20.00 | $50.00 |
| Est. cost per 1M input + 1M output tokens | $24.00 | $60.00 |
| Cached input / 1M tokens | $0.20 | $0.25 |
| AA Intelligence Index | 57.6 | 53.4 |
| AA Coding Index | — | 81.6 |
| AA Agentic Index | — | 57.9 |
| Max output tokens | 128,000 | 128,000 |
| API providers | 5 | 4 |
| Tool calling | Yes | Yes |
| Reasoning mode | Yes | Yes |
API cost
Estimated cost of 1M input + 1M output tokens via OpenRouter
Claude Opus 5.5
$24.00
Claude Fable 5.1
$60.00
Claude Opus 5.5 is 2.5× cheaper at list price.