Sepia

Sepia is an open-source writing Skill by Nanako Tsai (GitHub user Nanako0129). The README cites a 2026 study in which a classifier using narrative-structure features alone detected most AI-written fiction, and argues that removing the AI feel has to start with structure, beyond swapping words. It splits writing into two tracks. Fiction gets its narrative architecture repaired before word choice is touched; professional documents such as release notes, PR replies, postmortems, tickets and technical articles each get their own rules. There are four operations: write new, review, make minimal edits, and rewrite in full. What sets it apart is that it turns the related research into a three-pass revision process, with calibration notes for Chinese as well.

Who it's for:people writing English professional documents or fiction who want the template feel gone and the meaning kept; it's useful for Chinese writing too.

Before you start: install it as a plugin for Claude, Codex and other agents, or with npx skills add; the router and the operation entries need to be installed together. It's local Markdown rules with no API key and no uploads; your text is processed by the AI you use. We recommend only its general operations (write, review, edit, rewrite) and suggest choosing no extra voice when you call it. The repository includes an entry that imitates Hemingway's style (sepia-hemingway), which can also be pulled in when you ask for strong de-AI editing on fiction. We don't recommend using that entry. MIT license.

Based on the project's public documentation. Not tested by AI Inspiration World.