by Nanako0129
De-AI writing skill 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).
# Add to your Claude Code skills
git clone https://github.com/Nanako0129/sepiasepia is an open-source ai agents skill for AI coding assistants such as Claude Code, Codex CLI, and ChatGPT, built by Nanako0129. De-AI writing skill 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). It has 234 GitHub stars.
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Clone the repository with "git clone https://github.com/Nanako0129/sepia" and add it to your Claude Code skills directory (see the Installation section above).
sepia is primarily written in Shell. It is open-source under Nanako0129 on GitHub, so you can review or fork the full source.
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De-AI writing at the layer that actually gives AI away. Fiction gets its narrative architecture repaired before anyone touches word choice; professional documents (release notes, PR replies, postmortems, tickets, technical articles) each get rules matched to their venue.
A portable Agent Skill for Claude Code, Codex, Grok Build, and Antigravity. One canonical SKILL.md, no per-platform forks. Four operations: write, review (diagnose only), refactor (minimal edits), recreate (full rewrite).
Every popular humanizer edits word choice and syntax. StoryScope (Russell et al., 2026: 61,608 stories, human + 5 frontier LLMs) showed that a classifier using narrative-structure features alone detects AI fiction at 93.2% macro-F1, and that editing the surface style away barely moves it (95.5% → 93.9%). The tells that survive are architectural: themes explained by the narrator, single-track causally-tidy plots, emotions rendered only as bodily sensation, no real-world references, no reader, linear time, endings resolved by protagonist growth and acceptance.
sepia turns those measured gaps, together with the eleven related studies digested in research/, into a three-pass writing and revision protocol for fiction:
| Pass | Layer | Examples |
|---|---|---|
| 1 | Narrative architecture (fiction) | stop explaining the theme, loosen the causal chain, back-load revelations, mix emotion modes, sparse character networks, name real things |
| 2 | Discourse flow | de-template the paragraph-question sequence, fix the mid-story sag, vary rhythm and positions |
| 3 | Surface style | the classic layer: clichés, syntax templates, vocabulary, register |
Plus a 30-feature diagnosis rubric and per-model fingerprint corrections (Claude, GPT, Gemini, DeepSeek, Kimi).
Professional prose fails differently. The studies point at filler that carries no information, hedging where a judgment was needed, chatbot leftovers, register that ignores the venue, and formatting that looks stamped out. Each document type gets a thin rule file on top of one shared checklist:
| Domain | The gist |
|---|---|
| Release notes / announcements | user impact first, artifacts per claim, no marketing inflation |
| PR / issue replies | answer first, cite file:line, no reflex praise, length ∝ stakes |
| Postmortems | blameless toward people, merciless toward mechanisms; timestamps, dead ends, owned action items |
| Tickets / work orders | title = outcome, testable acceptance criteria, link don't repeat |
| Technical articles | open at the problem, one real dead end, one committed opinion, numbers with conditions |
The governing principle throughout: calibrate to the human distribution, don't invert the AI one. Humans sit at moderate values; a story with every rule applied is a new fingerprint. The skill selects 3–5 moves per story and leaves slack.
Every platform has its own native install, each paired with its update commands. Default everywhere is user scope — install once, use it in every project.
# install
claude plugin marketplace add Nanako0129/sepia
claude plugin install sepia@sepia --scope user
# update
claude plugin marketplace update sepia
claude plugin update sepia
The in-session /plugin install dialog asks you to pick a scope — choose User there.
# install
codex plugin marketplace add Nanako0129/sepia
codex plugin add sepia@sepia
# update — refresh the marketplace snapshot, then re-add to pick up the new version
codex plugin marketplace upgrade sepia
codex plugin add sepia@sepia
# install
grok plugin install Nanako0129/sepia --trust
# update
grok plugin update
Grok also auto-discovers a Claude Code install of sepia if you have one; either route works.
No marketplace here — the native install is placing the skill folder, plus the /sepia slash workflow:
# install
git clone https://github.com/Nanako0129/sepia.git ~/.sepia
mkdir -p ~/.gemini/config/skills ~/.gemini/antigravity/global_workflows
cp -R ~/.sepia/skills/sepia ~/.gemini/config/skills/sepia
cp ~/.sepia/.agents/workflows/sepia.md ~/.gemini/antigravity/global_workflows/sepia.md
# update
git -C ~/.sepia pull
rm -rf ~/.gemini/config/skills/sepia && cp -R ~/.sepia/skills/sepia ~/.gemini/config/skills/sepia
cp ~/.sepia/.agents/workflows/sepia.md ~/.gemini/antigravity/global_workflows/sepia.md
curl -fsSL https://raw.githubusercontent.com/Nanako0129/sepia/main/install.sh | bash
Clones the repo to ~/.sepia (override with SEPIA_HOME) and installs at user scope for all four platforms; re-running the same line is also the update. Prefer to inspect first? Clone it yourself and run ./install.sh from the checkout. Either way it installs:
| Platform | Where | Mechanism |
|---|---|---|
| Claude Code | ~/.claude/skills/sepia |
symlink |
| Codex | ~/.agents/skills/sepia |
symlink |
| Grok Build | ~/.grok/skills/sepia |
symlink |
| Antigravity | ~/.gemini/config/skills/sepia + /sepia global workflow |
copy |
npx skills add Nanako0129/sepia -g # -g = user scope; the default is project
npx skills update -g # update
When one repo should pin its own copy, commit skills/sepia/ into that repo as .agents/skills/sepia (Codex + Antigravity) or .claude/skills/sepia (Claude Code).
sepia/
├── skills/sepia/ # canonical skill (Agent Skills standard)
│ ├── SKILL.md # routing, operations, calibration rules, guardrails
│ └── references/
│ ├── narrative-pass.md # fiction pass 1: architecture (the differentiator)
│ ├── discourse-pass.md # pass 2: paragraph-level flow
│ ├── style-pass.md # pass 3: surface style
│ ├── rubric.md # fiction 30-feature diagnosis
│ ├── model-fingerprints.md # per-model corrections
│ ├── professional-pass.md # shared non-fiction layer (slop checklist, venue matching)
│ └── domains/ # release-notes, dev-replies, postmortems, tickets, tech-articles
├── .claude-plugin/ # Claude Code packaging (plugin.json, marketplace.json)
├── .codex-plugin/ # Codex packaging
├── .agents/ # Codex/Antigravity workspace-mode discovery + Antigravity workflow
├── install.sh
└── research/ # digested evidence base with sources
Full digests with links in research/. Primary: StoryScope (arXiv:2604.03136); LAMP (CHI 2025); Measuring AI Slop (arXiv:2509.19163); Reinhart et al. (PNAS 2025); Russell et al. (ACL 2025); NarraBench (arXiv:2510.09869); Echoes in AI (PNAS 2025); QUDsim (COLM 2025); Beguš (2024); Beyond Checkmate (EMNLP 2025); Nonaka & Perry (2025); Chakrabarty et al. (2026).
MIT