Anthropic Releases Claude Opus 5.5: Fable 5.1-Level Performance at 40% Lower Running Cost Than Opus 5
Anthropic ships Claude Opus 5.5: Fable 5.1-level performance at 40% lower cost. The efficiency play is reshaping frontier model economics.
Why it matters
A major frontier lab releases a new model tier that matches prior-generation capability at significantly reduced inference cost—a shift in how labs compete on capability-per-dollar, not just raw performance. Practitioners budgeting Claude workloads will recalculate; enthusiasts tracking the lab race see a new efficiency-first competitive move.
The key facts
5 to knowClaude Opus 5.5 released as first model in Claude 5.5 family
Performance matches Claude Fable 5.1 on most workloads
40% lower running cost than Opus 5 at default settings
Leads on agentic coding benchmarks (per Anthropic's internal evals)
Published Sep 22, 2026
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MarkTechPostmarktechpost.com
Publisher excerpt: Anthropic has released Claude Opus 5.5, the first model in its new Claude 5.5 family. The team states it performs at the level of Claude Fable 5.1 on most work. It also costs 40% less to run than Opus 5 on typical workloads at default settings. On Anthropic’s own benchmarks, it leads in agentic…