run-elm

name	run-elm
description	Run, build, screenshot, or regenerate protos for the local Elm SPA frontend (frontends/elm-spa). Use when the user wants to start the Elm dev server, check an Elm change standalone, or drive/screenshot a page in a headless browser.

Jonline's Elm frontend lives in frontends/elm-spa and is driven through its own Makefile. Paths below are relative to the repo root unless noted.

Running the dev server

cd frontends/elm-spa && make run

• This runs npx elm-spa server.
• Serves on port 1234 locally.
• The user often has this running themselves already — it's fine to kill and restart it.

Other targets

• make build — npx elm-spa build, a production build. Also the fastest way to get real compiler errors for a change — Gen.*/Request/Route (elm-spa's generated routing glue) only exist after this or make run has generated them at least once, so a bare elm make beforehand will show spurious "module not found" errors for those.
• make protos — regenerates Elm proto bindings into ./src from ../../protos/*.proto via protoc-gen-elm. Run make setup_proto_build once beforehand if protoc-gen-elm isn't installed (yarn global add protoc-gen-elm).

When to use this vs. the backend

Use this skill for fast standalone iteration on Elm code/UI. If you need to confirm a change works as served by the Rust backend (e.g. routing, embedded assets), use the run-backend skill's rebuild_elm_and_run target instead.

Screenshotting / driving a page (agent path)

chromium-cli isn't available in this container, so this skill carries its own tiny driver at .claude/skills/run-elm/driver.mjs (Playwright, chromium-cli-style line commands). It needs the dev server (above) already running on port 1234.

One-time setup:

cd .claude/skills/run-elm && npm install && npx playwright install chromium

Usage: pipe a line-per-command script to it (paths in screenshot are relative to your cwd when you invoke node, so cd back to the repo root first, or use absolute paths):

cd /path/to/jonline
node .claude/skills/run-elm/driver.mjs <<'EOF'
nav http://localhost:1234/server/http:localhost
wait-for text=About
screenshot /tmp/about.png
click button:has-text("Theme")
wait-for text=Primary Color
screenshot /tmp/theme.png
console-errors
EOF

Commands: nav <url>, wait-for text=<text> (or a CSS/Playwright selector), click <selector>, fill <selector> <value>, press <key>, sleep <ms>, screenshot <path>, console-errors (prints any console.errors seen so far). See the comment header in driver.mjs for the full list. Read the resulting PNG with the Read tool to actually look at it — a screenshot you didn't view proves nothing.

Gotchas

• Navigating to a /server/:id (or similar server-probing) route logs net::ERR_CONNECTION_REFUSED/ERR_SSL_PROTOCOL_ERROR to the console while it tries candidate ports — that's Shared.AccountsPanel's own connection negotiation working as designed, not a real error. Only worry about console-errors output that isn't explained by a page you know is probing a host.
• npx playwright install chromium can print a large "you're running this without installing your project's dependencies" warning banner and appear to do nothing — that's normal here (this driver's package.json lives in the skill dir, not the repo root); it still downloads the browser. If browsers were already cached from a previous run (~/.cache/ms-playwright), the command produces no output at all and returns immediately — that's success, not a hang.
• node_modules/package-lock.json under .claude/skills/run-elm/ are for this driver only, gitignored via the skill's own .gitignore — don't confuse them with the Elm app's own dependencies (there are none; Elm has no node_modules).