diff --git a/internal/backend-dev-plugin.mjs b/internal/backend-dev-plugin.mjs
index 46993c632..5a7dd82ca 100644
--- a/internal/backend-dev-plugin.mjs
+++ b/internal/backend-dev-plugin.mjs
@@ -32,10 +32,28 @@ export function devBackendProxy() {
 
 export function backendDevPlugin(root) {
   const children = []
+  const alive = new Set()   // backends whose process is running right now
   return {
     name: 'dx-backend-dev',
     apply: 'serve',
     configureServer(server) {
+      // ENGINE NOT RUNNING, QUIETLY (dx-shepherd, R500): with no backend process the proxy answered
+      // 500 ECONNREFUSED, which every page showed as console errors. While a backend is down its routes get
+      // well-formed answers instead: /events streams ONE status event saying the engine is offline (the
+      // plugin renders its own "engine not running" state from it), anything else returns an empty JSON
+      // list. Registered here, so it runs before vite's proxy.
+      for (const b of DEV_BACKENDS) {
+        server.middlewares.use(b.route, (req, res, next) => {
+          if (alive.has(b.name)) return next()
+          if ((req.url || '').startsWith('/events')) {
+            res.writeHead(200, { 'Content-Type': 'text/event-stream', 'Cache-Control': 'no-cache', Connection: 'keep-alive' })
+            res.write(`data: ${JSON.stringify({ type: 'status', status: { engine: 'offline', error: 'The desktop engine is not running.' } })}\n\n`)
+            return   // held open, so the EventSource does not reconnect in a loop
+          }
+          res.writeHead(200, { 'Content-Type': 'application/json' })
+          res.end('[]')
+        })
+      }
       for (const b of DEV_BACKENDS) {
         const bin = resolve(root, b.bin)
         if (!existsSync(bin)) {
@@ -47,8 +65,9 @@ export function backendDevPlugin(root) {
         const out = (d) => String(d).trim().split('\n').forEach((l) => l && server.config.logger.info(`${tag} ${l}`))
         child.stdout.on('data', out)
         child.stderr.on('data', out)
-        child.on('exit', (code) => server.config.logger.warn(`${tag} exited (${code})`))
+        child.on('exit', (code) => { alive.delete(b.name); server.config.logger.warn(`${tag} exited (${code})`) })
         children.push(child)
+        alive.add(b.name)
         server.config.logger.info(`${tag} started → ${b.route} on 127.0.0.1:${b.port}`)
       }
       const stop = () => children.forEach((c) => { try { c.kill('SIGTERM') } catch {} })