Cursor 3 Multi-Agent Architecture: How Planner/Worker Hierarchy Reduces Coding Costs by 15 Times

Cursor 3's upgraded Agent Swarm stratifies frontier model Planner with low-cost Workers: in a closed-book test of rewriting a database from scratch in Rust using only the SQLite manual, all four official configurations achieved 100% pass rate on sqllogictest. The total cost of Opus 4.8 + Composer 2.5 is approximately $1,339, which is about 7.9 times lower than the single-model GPT-5.5 cost of around $10,565 in controlled comparisons; the Worker layer cost can be reduced from $9,373 to $411. This article outlines the context separation principle, the self-developed VCS coordination mechanism, differences in cost calibers, and practical caveats.