This repository is a Rust library providing structured concurrency primitives for async programming. It offers operations such as `join`, `race`, `try_join`, `race_ok` for futures, and `merge`, `chain`, `zip` for streams, supporting tuples up to 12 elements, arrays, and `Vec` (with alloc feature). It also includes `FutureGroup` and `StreamGroup` for dynamic collections, and a `ConcurrentStream` trait for processing streams concurrently with backpressure and bounded concurrency. The library is runtime-agnostic (works with tokio, async-std, smol, etc.) and supports `no_std` environments. The code extensively uses pin projection, `ManuallyDrop`, and custom waker arrays with bit-set readiness tracking to achieve efficient polling and cancellation. It provides benchmark comparisons against `futures-rs` demonstrating competitive performance. There are no data pipelines, notebooks, or research elements; this is a pure library for async concurrency.