Anthropic launches Claude Opus 5.5: matches Fable 5.1 on most tasks at 40% lower cost
jyangballin · x · 2026-09-23
Anthropic officially introduced Claude Opus 5.5, the first model in its new Claude 5.5 family.
- The company says it performs at the level of Claude Fable 5.1 for most tasks while costing 40% less to run than Opus 5.
- The model card includes striking multi-agent results: a swarm of 100 agents coordinating to solve ProgramBench.
- Researcher jyangballin noted the work was featured in the release and raised a forward-looking question: as multi-agent systems scale, we may need new "agentic system concurrency primitives."
Related event: Anthropic launches Claude Opus 5.5: smarter, faster, 40% cheaper(66 posts)→
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