Anthropic says one AI agent beats many subagents now that models can handle complexity alone

Anthropic reports that a single agent loading context on demand often outperforms multi-agent setups in quality, cost, and latency, with one comparison running about twice as fast. It recommends teams evaluate consolidating sub-agents, since newer models like Opus 4.5, Opus 5.5, and Fable 5.1 can manage complex plans in a single loop, and it published a GitHub migration kit. Sub-agents still make sense when context windows degrade measurably, tasks need parallel separate contexts, or tool selection struggles.