blader/schematic — reverse-engineered prompt

Build me a reusable coding agent skill that can look at the current git branch and reverse engineer a full spec from the implementation. I want something I can use in Claude Code or Codex by saying things like “analyze this branch” or “write a spec from the code,” and it should inspect the branch diff, read all the changed files, and then generate a clear markdown document that explains what the work does.

The output should feel like a real product and technical spec, not just a summary. Include the problem being solved, the user facing requirements, architecture and technical design, which files changed and why, testing approach, rollout plan, and risks. Make sure it checks that every changed file was accounted for so the spec is complete.

If it helps, have it explore groups of files in parallel and then do a final completeness pass. Keep the result structured and easy to hand to a teammate or drop into a PR. Look up current Claude Code and Codex skill docs if you need to.