Prospero is a Claude Code plugin inspired by Superpowers - it focuses a great deal on interrogating your argument and helping you build a spine that's staged into an outline, which is then refined and drafted into a final form using your voice. Prospero also includes research and critique phases: a critic runs in a subagent, does independent research, and tries to find the holes in what you've written. The critic is pedantic to a fault but useful. Give it a poke.