Claude Fable 5 vs Fable 5.1: the point release is free and the cache got deeper
There's no cost reason to stay on Fable 5. Both charge $10/$50 per million and a live call costs $1.50 on either, but Fable 5.1's 97.5% cache discount cuts cached input to $0.25/M versus Fable 5's $1.00/M. Upgrade.
Same generation, same sticker price - 5.1 simply wins on cache discount.
Claude Fable 5.1 is a point release on the Fable 5 line, and Anthropic kept pricing completely flat: $10 per million input and $50 per million output on both. The only change that shows up on the bill is a deeper prompt-caching discount, which jumps from 90% on Fable 5 to 97.5% on Fable 5.1.
By TechCompare · Updated
Cost Comparison
Based on 100,000 input tokens (50% cached), 5,000 output tokens, and 100 requests.Prices are fetched live from OpenRouter and may include temporary promotional discounts not accounted for in our article and comparison figures.
Side-by-side specs
| Spec | Claude Fable 5 | Claude Fable 5.1 |
|---|---|---|
| Input Cost (per M) | $10.00 | $10.00 |
| Output Cost (per M) | $50.00 | $50.00 |
| Cached Input (per M) | $1.00 | $0.25 (better on this spec) |
| Batch Discount | 50% | 50% |
| Context Window | 1M | 1M |
How they differ
Claude Fable 5 is priced at $10.00 per million input tokens and $50.00 per million output tokens, with a 90% caching discount ($1.00 per million cached) and a 50% batch discount ($5/$25). Claude Fable 5.1 costs exactly the same - $10.00/$50.00 - but its caching discount deepens to 97.5%, dropping cached input to $0.25 per million. Both share a 1M context window. For a live 100K input + 10K output request both cost $1.50, so there's no penalty for upgrading. On cached workloads, Fable 5.1's input is four times cheaper.
Verdict
Four of five rows tie - $10.00/M input, $50.00/M output, 50% batch, and the same 1M context - so a live 100K+10K call costs $1.50 on both. The cached input row is the only difference and it isn't close: Fable 5.1 lands at $0.25/M against Fable 5's $1.00/M, a 4x gap that compounds across repeated agentic calls. Since the point release costs nothing extra and improves the one discount Anthropic's hardest-tier customers actually use, staying on Fable 5 leaves money on the table.
Which should you pick?
Choose Claude Fable 5
Basically never on cost grounds. Keep Fable 5 only if you've frozen a production pipeline and want to avoid re-validating the new point release, since the sticker price is identical anyway.
Choose Claude Fable 5.1
Everything else. Fable 5.1 is the same price with a deeper cache discount - the free upgrade. New projects should start here, and existing Fable 5 users on cache-heavy loops save real money by switching.