Claude Fable 5.1 is cheaper, substantially stronger on several agentic benchmarks, more concise, and apparently far less trigger-happy (says Anthropic).

the tl;dr

How much cheaper?
-Input/output pricing remains $10/$50 per million -tokens.
-Cache reads fall 75% to $0.25.
-Anthropic estimates ~25% lower costs for typical workloads and up to ~45% for highly agentic, context-heavy work.

BUT: not 45% cheaper for Claude subscriptions. ("...wherever usage is billed by token")

How much better than Fable 5?
-Scientific agent benchmark: 52.6% vs. 24.7% - more than 2×
-AutomationBench: 31.4% vs. 17.1% — an 84% relative gain
-GDPval-AA: 1,853 vs. 1,723
-CursorBench: 73.4% vs. 70.5%

So: dramatic gains on some long-running tasks, modest improvements elsewhere, not a uniform intelligence jump.

Verbosity also seems improved, although there is no standardized score. Rogo reports equal accuracy with 20% fewer tokens. Red Hat found its updates more concise and easier to follow. Every says it used half as many tokens as Opus 5 while running about twice as fast.

And fewer unnecessary red flags:
-~60% fewer cyber-safeguard interventions per Claude Code session
-Biology safeguards reportedly trigger 85% less often on benign elementary biology and medical questions
-Vulnerability discovery is now allowed, while exploit generation, penetration testing and binary scanning remain restricted or redirected

So far, sounds like a promising release. Although it clearly shows they care much more about business and enterprise users than us subscription pesants. Anyway: Testing time!