sepia
De-AI writing skill for any Agent Skills-compatible agent (77+ via the Skills CLI), with native plugins for Claude Code, Codex, Grok Build, and Antigravity. Narrative-architecture repair for fiction, venue-matched rules for professional prose. Based on StoryScope (arXiv:2604.03136).
Sepia is a de-AI writing skill that repairs narrative architecture in fiction and applies venue-matched rules to professional prose, compatible with 77+ AI agents through the Agent Skills standard. Based on research from StoryScope (arXiv:2604.03136), it targets structural tells rather than surface-level word choice, addressing narrative architecture issues like theme over-explanation, linear causality, and template-driven discourse. The skill provides four operations—write, review, refactor, and recreate—for fiction and professional documents including release notes, PR replies, postmortems, and technical articles. It ships as a canonical SKILL.md with native plugin packaging verified for Claude Code, Codex, Grok Build, and Antigravity.
Key Features
Use Cases
- 01Refactoring AI-generated fiction to remove structural tells like over-explained themes and single-track plots
- 02Writing release notes with user impact prioritized and artifact citations instead of marketing language
- 03Creating blameless postmortems with timestamped timelines, documented dead ends, and owned action items
- 04Reviewing AI-drafted technical articles to diagnose narrative and discourse issues before publication
- 05Generating PR and issue replies with direct answers, file:line citations, and length calibrated to stakes
- 06Composing fiction with minimalist voice profiles applied selectively while preserving architectural integrity
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sepia — FAQ
What is sepia and how is it different from other AI humanizers?+
Sepia is an agent skill that repairs narrative architecture and applies domain-specific rules rather than editing surface-level word choice. Based on StoryScope research showing that narrative structure features alone detect AI fiction at 93.2% accuracy, it targets structural tells like theme over-explanation, linear plots, and template discourse that survive surface editing.
How do I install sepia for Claude Code?+
Use the claude plugin marketplace add Nanako0129/sepia command followed by claude plugin install sepia@sepia --scope user. The in-session /plugin install dialog will prompt you to choose User scope for installation across all projects.
Which AI clients and agents work with sepia?+
Sepia works with 77+ agents via the Skills CLI including Cursor, Cline, Windsurf, Copilot, OpenCode, and goose. It has native plugin installers verified for Claude Code, Codex, Grok Build, and Antigravity.
Does sepia require any API keys or external services?+
No, sepia is a self-contained skill that runs within your AI agent without requiring external API keys or services. It operates as markdown-based instructions and reference files following the Agent Skills standard.
Is sepia free to use?+
Yes, sepia is released under the MIT license and is free to use, modify, and distribute.
Can I use sepia for both fiction and professional writing?+
Yes, sepia handles both domains with different approaches: fiction receives three-pass narrative architecture repair while professional prose gets venue-matched rules for release notes, PR replies, postmortems, tickets, and technical articles.
How do I install sepia?+
Open the source repository on GitHub and follow its README. sepia is a skill — MCP Agents Market links you directly to the official repo.
Is sepia free?+
sepia is an open-source project hosted on GitHub. Check the repository for its license and any usage requirements.