miniapp-cli dev: background edits never respawn the JSContext on Windows (path separators)

[skthegawd]

Summary

On Windows, miniapp-cli dev never respawns the background JSContext. Every edit under
src/background/ broadcasts reload (WebView only) instead of respawn-bg, so the phone keeps
running the previously installed bundle while the terminal reports activity and dist/ is correctly
rebuilt.

The failure is silent and looks like a working dev loop. It cost us about an hour of debugging a
stale bundle before we noticed the terminal line was reload src\background rather than
respawn-bg src/background/index.ts.

Cause

src/dev-server.ts decides which layer changed with forward-slash string tests:

const touchedBackground =
  filename.startsWith("src/background/") || filename.includes("/src/background/")

Windows fs.watch reports src\background\index.ts, so touchedBackground is always false and
nextType is always "reload".

The same assumption breaks the watcher's skip list:

const isUnder = (filename: string, name: string): boolean =>
  filename === name || filename.startsWith(`${name}/`) || filename.includes(`/${name}/`)

so isUnder(filename, "dist") never matches either, and build output is not filtered out of the
watcher on Windows.

Reproduction

1. On Windows, bunx @mentra/miniapp-cli dev in a two-layer project.
2. Install on a phone by scanning the QR.
3. Edit anything under src/background/, e.g. add a console.log at the top of the handler.
4. Observe the terminal prints reload src\background (note the backslash).
5. The new log line never appears in the forwarded [MentraJS] output — the phone is still running
   the old bundle, even though dist/background/index.js has a fresh mtime and contains the change.

Suggested fix

Normalise the separator once at the watcher boundary, before any path test:

const norm = (p: string): string => p.replace(/\\/g, "/")

const isUnder = (filename: string, name: string): boolean => {
  const f = norm(filename)
  return f === name || f.startsWith(`${name}/`) || f.includes(`/${name}/`)
}

const watcher = watch(options.watchDir, {recursive: true}, (_event, rawFilename) => {
  const filename = rawFilename === null ? null : norm(rawFilename)
  if (!filename) return
  // ...unchanged
})

Verified against a local copy of @mentra/miniapp-cli@0.1.0-dev.0: after this change a background
edit prints respawn-bg src/background/index.ts and the phone picks up the new bundle without a
reinstall.

Environment

• @mentra/miniapp-cli 0.1.0-dev.0, @mentra/miniapp 3.1.0-dev.27
• Host: Windows 11, Bun 1.x
• Device: Mentra Live, MentraOS app staging.20260808.*

Note

The project README we inherited advised "delete the entry in Miniapp Developer Settings and rescan to
pick up background changes". That workaround is a correct observation of this bug, and it may be
worth checking whether the docs recommend it anywhere — on macOS/Linux respawn-bg works and the
advice is unnecessary.