How is Opus 5.5 cheaper AND better than Fable 5.1? Genuinely trying to understand the "how"

Anthropic recently released Opus 5.5, which is reportedly 40% cheaper to run and 30%+ faster than Opus 5. Benchmarks suggest Opus 5.5 performs at a similar level to Fable 5.1, and even surpasses GPT-6 Astra in some areas. The community is seeking insights from ML experts on how these improvements were achieved, given that Anthropic does not disclose architectural details, to differentiate between realistic advancements and marketing claims.

This report uniquely highlights community skepticism and the call for expert insight into how Opus 5.5 achieves its claimed cost and performance improvements over Opus 5 and Fable 5.1, unlike typical product announcements.