A developer has introduced 6cy, an experimental streaming archive format designed to explore block-level codec polymorphism and streaming-first architecture. The project, built in Rust, aims to test whether archives can use different compression algorithms per block rather than applying a single codec globally. The format emphasizes crash recovery and plugin-based extensibility.

Unlike traditional formats like zip or 7z, 6cy eliminates global seeking requirements and incorporates self-describing blocks with periodic checkpoints for data recoverability. The architecture supports third-party codecs through a well-defined plugin interface, allowing proprietary algorithms to integrate without modifying the core format. Currently at v0.x, the specification remains subject to change with no compatibility guarantees yet.

The reference implementation includes standard codecs like Zstd and LZ4, with a CLI tool available for testing. The project positions itself for benchmarking, research, and ecosystem prototyping rather than production use. The developer explicitly seeks feedback on format design rather than performance comparisons, suggesting this is a research-focused initiative exploring whether per-block codec polymorphism offers meaningful advantages over existing archive formats.