Product notes
Product updates, new challenges, and improvements, newest first.
Add append-only persistence to Redis
Implement the AOF persistence extension to record writes and rebuild state from an append-only log.
Build Git in OCaml
The Git challenge now supports OCaml.
Optimistic Locking for Redis
Implement optimistic locking in your Redis server.
Build BitTorrent in Scala
The BitTorrent challenge now supports Scala.
Run background jobs in your shell
Add job tracking and manage processes that run without blocking the next command prompt.
Build Git in PHP
The Git challenge now supports PHP.
Build an Interpreter in Ruby
The Interpreter challenge now supports Ruby.
Filename Completion for Shell
Complete file and directory names when the user presses Tab.
More languages for Claude Code
Build your own Claude Code in C, C++, C# or Java.
Help for every stage
Every stage now points to available hints and solutions, or to code examples when those aren't available.
Build a Shell in OCaml
The Shell challenge now supports OCaml.
More focused concise code examples
Concise examples are ranked by relevant highlighted lines and filtered to avoid unfinished starter-code markers.
Reading is good.
Doing is better.
Build your own Claude Code, Shell, or SQLite. Understand what’s underneath.