Lean CMS sloth mascot — a sloth reclining on a beanbag chair with sunglasses and a Ruby-stickered laptop

Lean CMS

A lightweight Rails CMS with in-context editing for marketing sites.
leancms.dev

Lean CMS is a Rails Engine that adds in-context content editing, page content management, blog & portfolio, settings, role-based authentication, and notifications to any Rails 8 application. It's designed for marketing sites: server-rendered, no separate CMS service to host, and one rake task to seed your whole site structure from YAML.

Why Lean CMS

  • In-context editing — content editors hover over any page section to reveal an Edit overlay; no separate "admin" interface for day-to-day edits.
  • You own your design — the gem never touches your layouts or styles; helpers pull content into your own ERB templates.
  • YAML-defined structure — every page, section, and field is declared in config/lean_cms_structure.yml and seeded with one rake task.
  • Built-in auth — login, password reset, and magic-link invitations all shipped by the gem and namespaced under /lean-cms.
  • 9 content types — text, rich_text, image, boolean, url, color, dropdown, cards, bullets.
  • Version history — every content edit tracked via PaperTrail; one-click undo.

Installation

# Gemfile
gem "lean_cms"

bundle install
rails generate lean_cms:install
rails db:migrate

Then in app/controllers/application_controller.rb:

include LeanCms::Authentication

And in app/helpers/application_helper.rb:

include LeanCms::PageContentHelper

See the Getting Started guide for the full setup including User-model requirements and YAML structure.

Heads up — authentication. Lean CMS ships its own auth (login at /lean-cms/login, sessions, magic-link invites). It coexists cleanly with Rails 8's built-in bin/rails generate authentication (the install generator detects + warns). If you're already using Devise or another auth gem, the gem currently still adds a second login screen — first-class host-auth integration is the v0.3 milestone. See issue tracker for status.

A taste of the helper API

<%# A whole section, hover-editable for admins %>
<%= cms_editable_section(page: "home", section: "hero", display_title: "Hero") do %>
  <section class="hero">
    <h1><%= editable_content("hero", "heading") %></h1>
    <p><%= editable_content("hero", "subheading") %></p>

    <% bg = page_content_image_url(@page, "hero", "background") %>
    <% if bg %><%= image_tag bg, class: "absolute inset-0" %><% end %>
  </section>
<% end %>

<%# Responsive optimized <picture> for static layout images %>
<%= lean_cms_picture_tag "wire-panel",
      alt: "Wiring",
      widths: [640, 1280],
      sizes: "(min-width: 768px) 448px, 100vw",
      class: "rounded-2xl shadow-lg" %>

Requirements

  • Ruby ≥ 3.2
  • Rails ≥ 8.0
  • SQLite, PostgreSQL, or MySQL (SQLite is the happy path; see Database support for the compatibility matrix)

Roadmap

Lean CMS is 0.2.x — pre-1.0, API may shift between minors. Public roadmap:

  • v0.2.x (current): feature-complete CMS surface, in-context editing, hourly-resettable demo. Ships its own auth.
  • v0.3: host-auth adapter pattern — first-class integration with Devise / Rodauth / custom-auth hosts. Sibling lean-cms-devise-example repo as the proving ground + public reference.
  • v0.4 (idea stage): AI-powered lean_cms-scraper companion gem — bin/rails generate lean_cms:scrape URL=... writes a starter lean_cms_structure.yml from an existing live website.

Demo

Live at demo.leancms.dev — sign in with demo@leancms.dev / demo123 and edit anything. Content resets every hour at :00 UTC. Source: Ovrland-Services/lean-cms-demo.

License

MIT. See LICENSE.