Run Demo

Run Demo

Boots the LocoMotion demo Rails app, serving it on http://127.0.0.1:3000. This is a prerequisite for the screenshot-demo skill.

Two execution paths exist depending on environment:

• Local development (default) — use Docker via the justfile. Docker is installed locally; this matches the canonical dev workflow.
• Cloud sessions — Docker is installed but not started by default. You have two options: run bin/setup-docker once to bootstrap the full Docker-based just workflow (then Path A works exactly as it does locally), or use the lighter no-Docker rbenv + Node fallback below (Path B) to just serve the demo; that fallback's setup is handled by the SessionStart hook.

Detect which environment you are in via CLAUDE_CODE_REMOTE: if set to true, you are in a cloud session; otherwise you are local.

Path A — Local (Docker, preferred)

All commands run from the repo root. Always use just, never raw docker compose.

Boot the demo container

just demo          # build + run the demo container (foreground)
just demo-quick    # run without rebuilding

The first run builds the image (slow); subsequent runs reuse it. The demo is served at http://127.0.0.1:3000 once Rails reports Listening on.

Restart after library changes

Only required when files inside lib/loco_motion/ change. Component or demo edits are picked up automatically.

just demo-restart

Stop the demo

just down          # stop all containers

Other useful targets

just demo-shell      # open a bash shell inside the demo container
just demo-console    # open a Rails console
just demo-test       # run the demo RSpec suite

If just demo fails, check Docker is running (docker ps) and that no other process is holding port 3000 (lsof -i :3000).

Path B — Cloud Sessions (no Docker)

This path runs the demo directly against the host's Ruby and Node — no Docker — which is the quickest way to just serve the demo in a cloud session. (To instead use the full Docker-based just workflow there, run bin/setup-docker once and follow Path A; see CLAUDE.md.) The SessionStart hook (.claude/hooks/setup-demo.sh) handles all heavy setup automatically on every session start: rbenv install, vendor symlink, bundle install, db:prepare, and JS dependency installation.

Environment Notes (cloud only)

• Ruby: required version from docs/demo/Gemfile (currently 3.4.4), installed via rbenv.
• Node: the demo's package.json engines requires Node ~20. Use /opt/node20/bin — not Node 21 or 22 which are also present.
• yarn: use /opt/node22/bin/yarn with PATH="/opt/node20/bin:$PATH" so esbuild and Tailwind pick up the correct Node runtime.

Step 1: Verify the setup hook ran

Check the session startup log for:

==> [setup-demo] Setup complete. Start the demo server with the run-demo skill.

If the hook did not run (or failed), trigger it manually:

bash .claude/hooks/setup-demo.sh

Step 2: Build JavaScript

cd docs/demo && PATH="/opt/node20/bin:$PATH" /opt/node22/bin/yarn build

Expected: two .js bundles written to docs/demo/app/assets/builds/.

Step 3: Build CSS

The Tailwind config calls bundle show loco_motion-rails, so Ruby must be in scope:

cd docs/demo && \
  RBENV_VERSION=3.4.4 rbenv exec bundle exec \
  node node_modules/.bin/tailwindcss \
  -i ./app/assets/stylesheets/application.tailwind.css \
  -o ./app/assets/builds/application.css

Expected: output ends with Done in Xms.

Step 4: Start the Rails server

Remove any stale PID file, then launch in the background:

rm -f docs/demo/tmp/pids/server.pid

cd docs/demo && RBENV_VERSION=3.4.4 rbenv exec bundle exec rails server \
  -p 3000 -b 127.0.0.1 > /tmp/rails-demo.log 2>&1 &

echo $! > /tmp/rails-demo.pid

Wait for the server to accept connections:

for i in $(seq 1 10); do
  curl -s -o /dev/null -w "%{http_code}" http://127.0.0.1:3000/ \
    | grep -q "200" && echo "Server ready" && break
  sleep 1
done

If it never returns 200, check /tmp/rails-demo.log for errors.

Step 5: Stop the server (when done)

kill $(cat /tmp/rails-demo.pid) 2>/dev/null
rm -f /tmp/rails-demo.pid docs/demo/tmp/pids/server.pid

Troubleshooting

Local: just demo exits immediately — Run docker compose logs demo. Common causes: image build failed, port 3000 held by another process (lsof -i :3000), or stale containers (just down then retry).

Cloud: Server exits immediately — Check /tmp/rails-demo.log. Common causes: stale PID from a previous run (rm -f docs/demo/tmp/pids/server.pid), or port 3000 already in use (lsof -i :3000).

Cloud: CSS is unstyled — Re-run Step 3. tailwind.config.js calls bundle show loco_motion-rails; if Ruby is not in scope that call fails silently and outputs an empty stylesheet.

Cloud: JS build fails with "No matching export" — The local loco_motion JS source was not picked up. Re-run the hook (bash .claude/hooks/setup-demo.sh) and confirm the sed substitution on package.json succeeded before yarn install ran.

Cloud: yarn.lock shows as modified — You ran yarn install without --no-lockfile. Revert with git checkout -- docs/demo/yarn.lock.

Source: profoundry-us/loco_motion — distributed by TomeVault.