diff --git a/app/src/main/java/com/droiddeck/launcher/runtime/GuestCommand.kt b/app/src/main/java/com/droiddeck/launcher/runtime/GuestCommand.kt
index 1f8a7233d..3dd7ec189 100644
--- a/app/src/main/java/com/droiddeck/launcher/runtime/GuestCommand.kt
+++ b/app/src/main/java/com/droiddeck/launcher/runtime/GuestCommand.kt
@@ -47,7 +47,7 @@ object GuestCommand {
             .forEach { cmd.add("-b"); cmd.add(it) }
         cmd += listOf(
             "/usr/bin/env", "-i", "HOME=/root", "USER=root", "LANG=C.UTF-8",
-            "PATH=/usr/local/bin:/usr/bin:/bin", "XDG_RUNTIME_DIR=${runtimeDir.path}",
+            "PATH=/usr/local/bin:/usr/bin:/bin", "XDG_RUNTIME_DIR=${LinuxRuntime.GUEST_RUNTIME_DIR}",
             "XDG_DATA_HOME=/root/.local/share", "FLATPAK_BWRAP=${FlatpakManager.BWRAP}",
             "XDG_DATA_DIRS=/root/.local/share/flatpak/exports/share:/usr/local/share:/usr/share",
         )
diff --git a/app/src/main/java/com/droiddeck/launcher/runtime/LinuxRuntime.java b/app/src/main/java/com/droiddeck/launcher/runtime/LinuxRuntime.java
index 22feae5ce..43d068701 100644
--- a/app/src/main/java/com/droiddeck/launcher/runtime/LinuxRuntime.java
+++ b/app/src/main/java/com/droiddeck/launcher/runtime/LinuxRuntime.java
@@ -34,6 +34,14 @@ public final class LinuxRuntime {
     /** Shortcut extra naming which of the modes above a Linux entry launches. */
     public static final String EXTRA_LINUX_MODE = "linux_mode";
     private static final String KGSL_DEVICE = "/dev/kgsl-3d0";
+    /**
+     * Where the guest sees a command's XDG_RUNTIME_DIR. A Unix socket's path must fit in 108 bytes,
+     * and libwayland checks the guest's path before proot ever sees it: with the app on an SD card
+     * adopted as internal storage the files directory is /mnt/expand/<uuid>/user/0/<package>/files,
+     * and gamescope-0 under it is one byte over, so gamescope could not open its socket and the
+     * session ended at once. A long host path behind it is proot's to shorten.
+     */
+    public static final String GUEST_RUNTIME_DIR = "/run/droiddeck";
     /** Where every Linux session's debug log lands: public, so a user can just hand the folder over. */
     public static final String DEBUG_LOG_DIR = "DroidDeck";
 
@@ -185,7 +193,10 @@ public final class LinuxRuntime {
         bind(cmd, new File(root, "etc/bannerlator/empty").getPath() + ":/sys/fs/selinux");
         bind(cmd, context.getFilesDir().getPath());
         bind(cmd, context.getCacheDir().getPath());
-        if (runtimeDir != null) bind(cmd, runtimeDir.getPath());
+        if (runtimeDir != null) {
+            bind(cmd, runtimeDir.getPath());
+            bind(cmd, runtimeDir.getPath() + ":" + GUEST_RUNTIME_DIR);
+        }
         if (sessionRoot != null) bind(cmd, sessionRoot.getPath());
         if (externalStorage != null && externalStorage.isDirectory()) {
             bind(cmd, externalStorage.getPath());
diff --git a/app/src/main/java/com/droiddeck/launcher/session/SessionService.kt b/app/src/main/java/com/droiddeck/launcher/session/SessionService.kt
index fd51da14b..17eb197dd 100644
--- a/app/src/main/java/com/droiddeck/launcher/session/SessionService.kt
+++ b/app/src/main/java/com/droiddeck/launcher/session/SessionService.kt
@@ -277,7 +277,7 @@ class SessionService : Service() {
         // The desktop's Steam launchers start the client there (bannerlator-steam-launch), through the
         // same set-up as a Steam session: it gets what the client and its games are started with.
         val steamHere = SessionState.mode == MODE_STEAM || SessionState.mode == MODE_DESKTOP
-        addClientEnvironment(guest, runtimeDir, steamHere)
+        addClientEnvironment(guest, steamHere)
 
         val pulse = startAudio(guest, sessionDir)
 
@@ -483,7 +483,7 @@ class SessionService : Service() {
     }
 
     /** The guest's base environment: paths, the display, the GL/Vulkan stack and the client's switches. */
-    private fun addClientEnvironment(guest: MutableList<String>, runtimeDir: File, steamHere: Boolean) {
+    private fun addClientEnvironment(guest: MutableList<String>, steamHere: Boolean) {
         guest.add("/usr/bin/env")
         guest.add("-i")
         guest.add("HOME=/root")
@@ -494,7 +494,7 @@ class SessionService : Service() {
         // Without this the session is UTC: the client's clock, its logs and every timestamp in a
         // session bundle sit hours off the device's. Bannerlator carries the same line.
         guest.add("TZ=" + java.util.TimeZone.getDefault().id)
-        guest.add("XDG_RUNTIME_DIR=" + runtimeDir.path)
+        guest.add("XDG_RUNTIME_DIR=" + LinuxRuntime.GUEST_RUNTIME_DIR)
         guest.add("XDG_SESSION_TYPE=wayland")
         guest.add("WAYLAND_DISPLAY=wayland-0")
         guest.add("GAMESCOPE_FORCE_GENERAL_QUEUE=1")