Anthropic shipped Fable 5.1 today with a lot of coverage going to benchmarks. To me, the jumps look real. Terminal-Bench 4.0 increased from 42.0% with Fable 5 to 55.8% on Fable 5.1, and the "agentic science" benchmark more than doubled, going from 24.7% to 52.6%.
If you already have Claude in prod, hopefully you will now be exited about your cache bill (because it should be lower). Cache reads now cost $0.25 per million tokens, which is a 75% cut. Anthropic estimates that will be roughly 25% lower cost on typical deployments and closer to 45% on heavily agentic ones.
Your savings depend entirely on one ratio
Input is still $10 per million tokens and Output is still $50 per million tokens. Neither have changed with this update. The only price that has changed is the cache read itself, which is what you pay every time the model re-reads context it has already processed.
That makes the arithmetic is simple. Your savings work out to about 75% of whatever share cache reads represent of your current bill.
If cache consumption is a third of your spend, then you save around 25%. If they are 60% of your spend, you save ~45%. If you are barely caching at all, this release saves you close to nothing, but congrats, because you now know you can cache and it will save you a few bucks moving forward.
Most teams I talk to have no idea which bucket they are in. That is the actual problem I get excited about solving.
An example
Take an agent running code against a large repo. The system prompt, the repo context/map, and all instructions come to roughly 150,000 tokens of cached prefix, and a working session hits the model 40 times. That is 6 million cache read tokens in a single session.
At the old rate of $1.00 per million, those reads cost $6.00. At $0.25 per million, they cost $1.50.
