Installing Bullet Train Themes on Jumpstart Pro Projects

Bullet Train themes can be installed on Jumpstart Pro projects, giving you native erb partials and Hotwire-powered UI components.

Like Jumpstart Pro, Bullet Train themes are built using tailwindcss and use esbuild and postcss for JavaScript and style sheets.

To get a quick sense of the UI components, we encourage you to spin up a Bullet Train project and navigate through the screens to create a "Creative Concept" and "Tangible Thing" resources.

In addition to providing a nice set of UI components, you'll get access to nice_partials, Bullet Train's own lightweight answer for creating erb partials with ad-hoc named content areas, which we think is just the right amount of magic for making erb-based components.

Note: we also have instructions for installing themes on other Rails projects.


  1. Installation Instructions
  2. Optional Configurations for switching colors, theme gems
  3. Using Locales for fields on new models
  4. Partials that require special instructions, exclusions
  5. Modifying ejected partials

1. Installation Instructions

Add the theme gem

These instructions assume you're installing the Light theme bundled with Bullet Train.

bundle add bullet_train-themes-light

Or add the following to your Gemfile:

gem "bullet_train-themes-light"

And then run:

bundle install

Add npm packages

The Light theme requires the following npm packages to be installed

yarn add @bullet-train/bullet-train @bullet-train/fields autoprefixer @rails/actiontext postcss-extend-rule

Update your app/javascript/controllers/index.js with the following lines:

import { controllerDefinitions as bulletTrainControllers } from "@bullet-train/bullet-train"
import { controllerDefinitions as bulletTrainFieldControllers } from "@bullet-train/fields"


Add bin/theme and bin/link bin stubs

curl -L "" -o bin/theme
curl -L "" -o bin/link
chmod +x bin/theme bin/link

Update esbuild.config.mjs

Replace it with these contents.

#!/usr/bin/env node

// Esbuild is configured with 3 modes:
// `yarn build` - Build JavaScript and exit
// `yarn build --watch` - Rebuild JavaScript on change
// `yarn build --reload` - Reloads page when views, JavaScript, or stylesheets change. Requires a PORT to listen on. Defaults to 3200 but can be specified with PORT env var
// Minify is enabled when "RAILS_ENV=production"
// Sourcemaps are enabled in non-production environments

import * as esbuild from "esbuild"
import path from "path"
import { execSync } from "child_process"
import rails from "esbuild-rails"
import chokidar from "chokidar"
import http from "http"
import { setTimeout } from "timers/promises"

let themeFile = ""
if (process.env.THEME) {
  themeFile = execSync(`bundle exec bin/theme javascript ${process.env.THEME}`).toString().trim()

const themeEntrypoints = {}
if (process.env.THEME) {
  themeEntrypoints[`application.${process.env.THEME}`] = themeFile

const clients = []
const entryPoints = {
  "application": path.join(process.cwd(), "app/javascript/application.js"),
  "administrate": path.join(process.cwd(), "app/javascript/administrate.js"),
const watchDirectories = [
  "./app/assets/builds/**/*.css", // Wait for cssbundling changes
const config = {
  absWorkingDir: path.join(process.cwd(), "app/javascript"),
  bundle: true,
  entryPoints: entryPoints,
  minify: process.env.RAILS_ENV == "production",
  outdir: path.join(process.cwd(), "app/assets/builds"),
  plugins: [rails()],
  sourcemap: process.env.RAILS_ENV != "production",
  define: {
    global: "window"
  loader: {
    ".png": "file",
    ".jpg": "file",
    ".svg": "file",
    ".woff": "file",
    ".woff2": "file",
    ".ttf": "file",
    ".eot": "file",

async function buildAndReload() {
  // Foreman & Overmind assign a separate PORT for each process
  const port = parseInt(process.env.PORT || 3200)
  console.log(`Esbuild is listening on port ${port}`)
  const context = await esbuild.context({
    banner: {
      js: ` (() => new EventSource("http://localhost:${port}").onmessage = () => location.reload())();`,

  // Reload uses an HTTP server as an even stream to reload the browser
    .createServer((req, res) => {
      return clients.push(
        res.writeHead(200, {
          "Content-Type": "text/event-stream",
          "Cache-Control": "no-cache",
          "Access-Control-Allow-Origin": "*",
          Connection: "keep-alive",

  await context.rebuild()
  console.log("[reload] initial build succeeded")

  let ready = false
    .on("ready", () => {
      console.log("[reload] ready")
      ready = true
    .on("all", async (event, path) => {
      if (ready === false)  return

      if (path.includes("javascript")) {
        try {
          await setTimeout(20)
          await context.rebuild()
          console.log("[reload] build succeeded")
        } catch (error) {
          console.error("[reload] build failed", error)
      clients.forEach((res) => res.write("data: update\n\n"))
      clients.length = 0

if (process.argv.includes("--reload")) {
} else if (process.argv.includes("--watch")) {
  let context = await esbuild.context({...config, logLevel: 'info'})
} else {

Update tailwind.config.js

Replace with these contents, which merge the Bullet Train-specific tailwind configs with those of Jumpstart Pro.

Note: After this step, you might get an error on build about a missing process.env.THEME. Follow with the next step to fix this error.

const path = require('path');
const { execSync } = require("child_process");
const glob  = require('glob').sync

if (!process.env.THEME) {
  throw "tailwind.config.js: missing process.env.THEME"
const themeConfigFile = execSync(`bundle exec bin/theme tailwind-config ${process.env.THEME}`).toString().trim()
let themeConfig = require(themeConfigFile)

const colors = require('tailwindcss/colors')
const defaultTheme = require('tailwindcss/defaultTheme')

themeConfig.darkMode = 'class'


themeConfig.content = [ Set([

themeConfig.theme.extend.colors = {
  secondary: colors.emerald,
  tertiary: colors.gray,
  gray: colors.neutral,
  "code-400": "#fefcf9",
  "code-600": "#3c455b",

themeConfig.theme.extend.fontFamily = {
  sans: ['Inter', ...defaultTheme.fontFamily.sans],

module.exports = themeConfig

Update build:css in package.json

In package.json, replace the build and build:css entries under scripts with:

"build": "THEME=\"light\" node esbuild.config.mjs",
"build:css": "bin/link; THEME=\"light\" tailwindcss --postcss --minify -c ./tailwind.config.js -i ./app/assets/stylesheets/application.tailwind.css -o ./app/assets/builds/application.tailwind.css",

Define current_theme helper

In your app/helpers/application_helper.rb, define:

def current_theme

Add stylesheet_link_tag to <head>

Make sure you have the following three lines in your <head>, which should be defined in app/views/layouts/application.html.erb:

<%= stylesheet_link_tag "application", media: "all", "data-turbo-track": "reload" %>
<%= stylesheet_link_tag "application.tailwind", media: "all", "data-turbo-track": "reload" %>
<%= javascript_include_tag 'application.light', 'data-turbo-track': 'reload' %>

Update postcss.config.js

Replace with these contents:

const { execSync } = require("child_process");

const postcssImportConfigFile = execSync(`bundle exec bin/theme postcss-import-config ${process.env.THEME}`).toString().trim()
const postcssImportConfig = require(postcssImportConfigFile)

module.exports = {
  plugins: [

Import the Theme Style Sheet

To your application.tailwind.css file, add the following line:

@import "$ThemeStylesheetsDir/application.css";

Add Themify Icons, jQuery (for now) and trix editor support

Note: jQuery is needed for some of our components, but defining window.$ won't be required soon. See PR

yarn add @icon/themify-icons jquery

To your application.js, add the following line:

import jquery from "jquery"
window.jQuery = jquery
window.$ = jquery


import { trixEditor } from "@bullet-train/fields"

Add Locale Strings

Add these to your config/locales/en.yml under en:

      date_field: "%m/%d/%Y"
      date_and_time_field: "%m/%d/%Y %l:%M %p"
      date_controller: "MM/DD/YYYY"
    am: AM
    pm: PM
      date_field: "%m/%d/%Y"
      date_and_time_field: "%m/%d/%Y %l:%M %p"
      date_controller: "MM/DD/YYYY h:mm A"
    firstDay: 1
    separator: " - "
    applyLabel: "Apply"
    cancelLabel: "Cancel"
    fromLabel: "From"
    toLabel: "To"
    customRangeLabel: "Custom"
    weekLabel: "W"
    - "Su"
    - "Mo"
    - "Tu"
    - "We"
    - "Th"
    - "Fr"
    - "Sa"
    - "January"
    - "February"
    - "March"
    - "April"
    - "May"
    - "June"
    - "July"
    - "August"
    - "September"
    - "October"
    - "November"
    - "December"
    today: Today
    yesterday: yesterday
    last7Days: Last 7 Days
    last30Days: Last 30 Days
    thisMonth: This Month
    lastMonth: Last Month
      other: Other
      cancel: Cancel
      all: All

Disable display: block on label elements

In app/assets/stylesheets/components/forms.css, find the line under label {:

@apply block text-sm font-medium leading-5 text-gray-700 mb-1;

And remove the block token:

@apply text-sm font-medium leading-5 text-gray-700 mb-1;

2. Optional Configurations for switching colors, theme gems

For Setting the Active Color

curl -L "" -o initializers/theme.rb

Add the following classes to your html tag for your layout:

<html class="theme-<%= BulletTrain::Themes::Light.color %> <%= "theme-secondary-#{BulletTrain::Themes::Light.secondary_color}" if BulletTrain::Themes::Light.secondary_color %>"

For Switching Between Installed Themes

If you'd like to create your own theme but would still like to build on top of :light, you'll need to have both gems installed and you'll be able to switch the current theme this way.

Change the current_theme value in app/helpers/application_helper.rb

def current_theme

To change to use a different theme:

  1. Change the value returned by current_theme to the new theme name
  2. Change the name of the THEME env var defined in build and build:css in package.json
  3. Change the name of the theme in the javascript_include_tag in the <head>.

3. Using Locales for fields on new models

The theme's field partials work best with locale strings that are defined for the model you're creating.

Example: you've created a Project model. Here we'll create a projects.en.yml

  1. Run curl -L "" -o config/locales/projects.en.yml
  2. Search and replace projects.en.yml for scaffolding/completely_concrete/tangible_things, Tangible Things, Tangible Thing, tangible_things and tangible_thing. Replace with projects, Projects, Project, projects and project respectively.
  3. Remove strings you won't be using. In particular, look for comments with "skip" or "scaffolding".

Some fields use locale strings to drive their options. In the tangible_things.en.yml template file, look for super_select_value, multiple_option_values and others.

You'll notice & and * symbols prefixing some special keys in the yml file. Those are anchors and aliases and they help you reduce repetition in your locale strings.

To learn more about how these locales are generated in Bullet Train, see the documentation on Bullet Train's Super Scaffolding

4. Partials that require special instructions, exclusions

For using boolean-type fields (options, buttons)

In ApplicationController, add this:

include Fields::ControllerSupport

For the file_field partial

# in the model
has_one_attached :file_field_value
after_validation :remove_file_field_value, if: :file_field_value_removal?
attr_accessor :file_field_value_removal
def file_field_value_removal?
def remove_file_field_value
# in the controller's strong_params

For image, active_storage_image

See account/users_helper in BT core repo for implementing photo_url_for_active_storage_attachment

5. Modifying ejected partials

For ejecting a theme partial and modifying it

We recommend firing up a Bullet Train project and using its bin/resolve (see docs on Indirection) to get a copy of the partial field locally to modify.