Tapak is a composable web framework for OCaml 5, built on EIO (effect-based I/O) and inspired by Twitter’s Finagle architecture.

With OCaml 5’s effect handlers and EIO (effect-based I/O), we now have a foundation for writing concurrent code that is both ergonomic (direct style, no monads) and performant (no heap allocations for context switching).

Tapak explores what a modern, practical web framework looks like when built on this foundation:

1. Embraces modern OCaml: OCaml 5 effects + EIO for direct-style concurrent code
2. Type-safe from the ground up: GADT-based routing with compile-time parameter checking
3. Composable architecture: Finagle’s proven Service/Filter pattern for modularity
4. Focused core: Not batteries-included, compose what you need

Unlike Dream or Opium (Lwt-based with monadic code), Tapak uses EIO for direct-style concurrency. Unlike Eliom (full-stack with client/server shared code), Tapak focuses on server-side HTTP services with maximum composability.

This is an experiment in pushing the boundaries of typed functional web development while keeping pragmatism and real-world usage in mind.