Effect 4.0

Effect 4.0 has been released with a complete rebuild that delivers 5× smaller bundle sizes, 6.4× higher concurrent task throughput, and 86% less memory usage compared to Effect 3. The new version consolidates previously separate packages into a single ecosystem with zero runtime dependencies and introduces long-term support through September 2029, providing enterprises and production users with stability guarantees. Effect has grown from a programming model for functions to a full-stack platform supporting distributed systems, now serving major companies with 43.9M weekly npm downloads.