diff --git a/backend/system/userdata.go b/backend/system/userdata.go
index 39dde59..9f232fe 100644
--- a/backend/system/userdata.go
+++ b/backend/system/userdata.go
@@ -29,6 +29,29 @@ const (
 // without touching the current user's real config.toml or yj.db.
 const envHomeOverride = "YJ_HOME"
 
+// UseHomeOverride points every config and data path at base, by setting
+// the same override a development sandbox uses.
+//
+// It exists for mobile, where the switch in buildUserDirPath has no
+// answer: there is no home directory and no XDG, only a per-app private
+// directory the OS hands out at runtime. The caller is main(), which is
+// the only place that can ask the platform for it — deliberately, so
+// this package stays free of the Wails application package that knows
+// (see backend/events' indexbuild split for why that matters).
+//
+// Two rules. An empty base is a no-op, because that is exactly what
+// application.Mobile.StoragePath() returns on desktop. And an override
+// that is already set wins, so YJ_HOME on the command line still
+// relocates a sandbox on a platform that would otherwise decide for
+// itself.
+func UseHomeOverride(base string) {
+	if base == "" || os.Getenv(envHomeOverride) != "" {
+		return
+	}
+
+	_ = os.Setenv(envHomeOverride, base)
+}
+
 // getUserDirPath returns and creates the path for a user directory.
 func getUserDirPath(dt dirType) (string, error) {
 	path, err := resolveUserDirPath(dt)
diff --git a/backend/system/userdata_test.go b/backend/system/userdata_test.go
index b24abc0..3829360 100644
--- a/backend/system/userdata_test.go
+++ b/backend/system/userdata_test.go
@@ -1,6 +1,7 @@
 package system
 
 import (
+	"os"
 	"path/filepath"
 	"strings"
 	"testing"
@@ -50,3 +51,39 @@ func TestResolveUserDirPath_NoOverrideUsesOSPath(t *testing.T) {
 		)
 	}
 }
+
+// UseHomeOverride carries two rules that a mobile launch depends on and
+// that nothing else would notice breaking: an empty base must do
+// nothing, because that is precisely what StoragePath() returns on
+// desktop, and an override already set must win, or YJ_HOME would stop
+// relocating a sandbox on the platform that decides for itself.
+func TestUseHomeOverride(t *testing.T) {
+	const (
+		storage = "/data/user/0/app.yellowjacket/files"
+		sandbox = "/tmp/sandbox"
+	)
+
+	tests := []struct {
+		name    string
+		already string
+		base    string
+		want    string
+	}{
+		{name: "empty base is a no-op", already: "", base: "", want: ""},
+		{name: "sets the override when unset", already: "", base: storage, want: storage},
+		{name: "an existing override wins", already: sandbox, base: storage, want: sandbox},
+		{name: "empty base keeps an existing override", already: sandbox, base: "", want: sandbox},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			t.Setenv(envHomeOverride, tt.already)
+
+			UseHomeOverride(tt.base)
+
+			if got := os.Getenv(envHomeOverride); got != tt.want {
+				t.Errorf("%s = %q, want %q", envHomeOverride, got, tt.want)
+			}
+		})
+	}
+}
diff --git a/main.go b/main.go
index 22553f9..5c593d4 100644
--- a/main.go
+++ b/main.go
@@ -15,6 +15,7 @@ import (
 	"yellowjacket/backend/assets"
 	"yellowjacket/backend/config"
 	"yellowjacket/backend/profiling"
+	"yellowjacket/backend/system"
 	"yellowjacket/internal/dev"
 )
 
@@ -28,6 +29,20 @@ var (
 var frontendDistAssets embed.FS
 
 func main() {
+	// **Mobile has no home directory, and this must run before anything
+	// asks for a path.** backend/system resolves config and data from
+	// $HOME or the OS equivalent, and on Android there is neither: its
+	// switch on runtime.GOOS took the default branch and returned
+	// errUnsupportedOS, so NewYellowJacketApp failed and main() exited
+	// six milliseconds after the JNI bridge came up -- with no panic and
+	// no tombstone, because os.Exit is not a crash.
+	//
+	// StoragePath() is the platform's own answer (getFilesDir() on
+	// Android, Application Support on iOS) and returns "" on desktop,
+	// where UseHomeOverride is then a no-op -- so this needs no build
+	// tag and changes nothing off mobile.
+	system.UseHomeOverride(application.Mobile.StoragePath())
+
 	// WebKitGTK's DMABuf renderer crashes on NVIDIA GPUs under Wayland.
 	// Only disable it for that specific combo so AMD/Intel and X11 users
 	// keep full hardware-accelerated buffer sharing.  Users can also