diff --git a/etc/skel/www/userMediaStackPanel.php b/etc/skel/www/userMediaStackPanel.php
index 2953deb3..d52c9a54 100644
--- a/etc/skel/www/userMediaStackPanel.php
+++ b/etc/skel/www/userMediaStackPanel.php
@@ -572,9 +572,12 @@ function pmssMediaStackPanelStartCommandBuild(string $home, string $username): s
     $scriptPath = pmssCustomerHomePath($home, 'install-media-stack.sh');
     $pidPath = pmssCustomerHomePath($home, '.install-media-stack-web.pid');
 
+    // Background only the installer: a trailing `&` over the whole && list would also
+    // background `rm` (racing away the pid file) and keep shell_exec's pipe open until
+    // the install ends, so the request dies with the installer's lighttpd restart.
     $innerCommand = 'cd '.escapeshellarg($home)
         .' && rm -f -- '.escapeshellarg($pidPath)
-        .' && nohup /bin/bash '.escapeshellarg($scriptPath).' >/dev/null 2>&1 & echo $! > '.escapeshellarg($pidPath);
+        .' && { nohup /bin/bash '.escapeshellarg($scriptPath).' </dev/null >/dev/null 2>&1 & echo $! > '.escapeshellarg($pidPath).'; }';
 
     return 'HOME='.escapeshellarg($home)
         .' USER='.escapeshellarg($username)
diff --git a/scripts/lib/tests/development/mediaStackPanelTest.php b/scripts/lib/tests/development/mediaStackPanelTest.php
index 35e34701..54520147 100644
--- a/scripts/lib/tests/development/mediaStackPanelTest.php
+++ b/scripts/lib/tests/development/mediaStackPanelTest.php
@@ -359,6 +359,23 @@ public function testStartCommandIncludesPidFileAndScriptPath(): void
         $this->assertStringContainsAllStrings(['.install-media-stack-web.pid', 'install-media-stack.sh', "USER='alice'"], $command);
     }
 
+    public function testStartCommandReturnsAtOnceAndKeepsPidFile(): void
+    {
+        $home = $this->pmssMakeTempDir('pmss-media-start-launch-');
+        $this->pmssWriteExecutableFile($home.'/install-media-stack.sh', "#!/bin/bash\nsleep 3\n");
+
+        $started = microtime(true);
+        shell_exec(\pmssMediaStackPanelStartCommandBuild($home, 'alice'));
+        $elapsed = microtime(true) - $started;
+        $pid = (int) trim((string) @file_get_contents($home.'/.install-media-stack-web.pid'));
+
+        $this->assertTrue($elapsed < 2.0, 'launch must not wait for the installer ('.round($elapsed, 2).'s)');
+        $this->assertTrue($pid > 0 && is_dir('/proc/'.$pid), 'pid file must name the running installer');
+        if ($pid > 0 && function_exists('posix_kill')) {
+            posix_kill($pid, 15);
+        }
+    }
+
     public function testRecoveryCommandUsesFixedInstallerMode(): void
     {
         $command = \pmssMediaStackPanelRecoveryCommandBuild('/home/alice', 'alice');