Software · Open source · 2026
Vellum
A Claude Code plugin for writing novels: one command runs the chapter loop, three hard gates protect quality, and a Python engine checks continuity so the model doesn't spend tokens on it.
# Vellum
/plugin marketplace add FiredMosquito831/my-writing-companion
/plugin install vellum@my-writing-companion
- 3
- hard gates; everything else is advisory
- 16
- agents with isolated roles
Long-form fiction is where AI writing workflows fall apart: drafts drift toward the average, critique leaks into drafting, and continuity dies when the context is compacted somewhere around chapter nine. Vellum replaces good intentions with mechanisms.
What we built
- Gates that read files, not chat: an approved outline before any prose, a blind-reader verdict on pivotal chapters, and a beta-reader pass before export
- Sixteen agents with strict role isolation: the writer cannot read the critiques and the critics cannot write prose
- A standard-library Python engine for the mechanical checks, such as a dead character reappearing or knowledge arriving before its chapter
- A one-screen state card rebuilt at every session start, voice profiles measured from the author's own prose, and an optional series layer for multi-book canon and retcons
- Markdown and EPUB export, tested on Ubuntu and Windows in CI
Credit
Vellum is a fork of haowjy/creative-writing-skills (Apache-2.0), rebuilt into a complete harness that combines verified mechanisms from twenty writing systems. Every ported mechanism is credited in the repository's ATTRIBUTION file.