fix(shellui): apply system language after dropping ptrace

source/shellui/include/toolbox_i18n.hpp

@@ -44,8 +44,10 @@ void apply_ui_lang(int ui_lang);
 /**
  * Apply the stored UI language setting.
  * 0=system, 1=zh-Hans, 2=en, 3=ar, 4=zh-Hant, 5=ja, 6=fr, 7=de, 8=ko,
- * 9=es, 10=pt-BR, 11=it, 12=ru, 13=pl, 14=th. This is a configuration
- * boundary: system is queried here once, then XML and notifications
+ * 9=es, 10=pt-BR, 11=it, 12=ru, 13=pl, 14=th.
+ * 0 queries SCE_SYSTEM_SERVICE_PARAM_ID_LANG. Call this only when
+ * SystemService can answer (not under PTRACE_AUTHID). A failed query
+ * leaves the current language unchanged; XML and notifications then
  * reuse the resolved language.
  */
 void apply_system_or_ui_lang(int ui_lang);

source/shellui/src/prx.cpp

@@ -25,6 +25,7 @@ along with this program; see the file COPYING. If not, see
 #include "plugin_ui_bridge_client.hpp"
 #include "proc.h"
 #include "ps5/kernel.h"
+#include "toolbox_i18n.hpp"
 #include "ucred.h"
 #include "webserver.hpp"
 
@@ -791,6 +792,9 @@ int main(int argc, char const* argv[]) {
   LOG_DEBUG("Performed Magic");
   setup_proc_hooks();
 
+  /* SystemService cannot be queried under PTRACE_AUTHID. */
+  toolbox_i18n::apply_system_or_ui_lang(g_settings.ui_lang);
+
   shellui_hooks_publish_ready();
   /*
    * Home already cached pre-inject state. Display-TID spoof and the top-nav

source/shellui/src/toolbox_i18n.cpp

@@ -1,9 +1,12 @@
 /* Copyright (C) 2025 OnionHEN / LightningMods */
 
 #include "toolbox_i18n.hpp"
+#include <onion/log.h>
 #include <onion/notify_i18n.h>
 
-#ifndef ONION_HOST_TEST
+#ifdef ONION_HOST_TEST
+extern "C" int sceSystemServiceParamGetInt(int param_id, int *value);
+#else
 #include "external_symbols.hpp"
 #endif
 
@@ -170,6 +173,24 @@ int locale_index_for_lang(Lang lang) {
   return kI18nLocaleFallback;
 }
 
+/* SCE_SYSTEM_SERVICE_PARAM_ID_LANG */
+constexpr int kSystemServiceParamIdLang = 1;
+
+bool read_system_language(int *out) {
+#ifndef ONION_HOST_TEST
+  if (!sceSystemServiceParamGetInt)
+    return false;
+#endif
+  int language = 0;
+  const int result =
+      sceSystemServiceParamGetInt(kSystemServiceParamIdLang, &language);
+  if (result < 0 || language < 0)
+    return false;
+  if (out)
+    *out = language;
+  return true;
+}
+
 } // namespace
 
 Lang active_lang() { return lang_from_notify(onion_notify_get_language()); }
@@ -225,11 +246,12 @@ void apply_system_or_ui_lang(int ui_lang) {
     return;
   }
 
-  int system_language = 1;
-#ifndef ONION_HOST_TEST
-  if (sceSystemServiceParamGetInt)
-    (void)sceSystemServiceParamGetInt(1, &system_language);
-#endif
+  int system_language = 0;
+  if (!read_system_language(&system_language)) {
+    LOG_WARN("system language query failed; keeping %d",
+             static_cast<int>(active_lang()));
+    return;
+  }
   set_lang(lang_from_notify(onion_notify_resolve_language(0, system_language)));
 }
 

source/util/tests/test_toolbox_i18n.cpp

@@ -7,6 +7,8 @@
 #include <cstring>
 #include <string>
 
+extern "C" void onion_test_system_language_configure(int result, int value);
+
 using namespace toolbox_i18n;
 
 static int test_default_zh(void) {
@@ -308,11 +310,37 @@ static int test_apply_ui_lang(void) {
   return 0;
 }
 
-static int test_system_lang_host_fallback(void) {
-  apply_system_or_ui_lang(2);
-  TEST_ASSERT_TRUE(active_lang() == Lang::En);
+static int test_system_lang_follows_query(void) {
+  onion_test_system_language_configure(0, 11);
+  apply_system_or_ui_lang(0);
+  TEST_ASSERT_TRUE(active_lang() == Lang::ZhHans);
+
+  onion_test_system_language_configure(0, 1);
   apply_system_or_ui_lang(0);
   TEST_ASSERT_TRUE(active_lang() == Lang::En);
+
+  apply_system_or_ui_lang(2);
+  TEST_ASSERT_TRUE(active_lang() == Lang::En);
+  onion_test_system_language_configure(0, 11);
+  apply_system_or_ui_lang(2);
+  TEST_ASSERT_TRUE(active_lang() == Lang::En);
+
+  onion_test_system_language_configure(0, 1);
+  return 0;
+}
+
+static int test_system_lang_query_failure_keeps_current(void) {
+  set_lang(Lang::ZhHans);
+  onion_test_system_language_configure(-1, 1);
+  apply_system_or_ui_lang(0);
+  TEST_ASSERT_TRUE(active_lang() == Lang::ZhHans);
+
+  set_lang(Lang::En);
+  onion_test_system_language_configure(-1, 11);
+  apply_system_or_ui_lang(0);
+  TEST_ASSERT_TRUE(active_lang() == Lang::En);
+
+  onion_test_system_language_configure(0, 1);
   return 0;
 }
 
@@ -386,8 +414,10 @@ extern "C" int test_toolbox_i18n_suite(void) {
   fails += onion_test_run("i18n.pl", test_pl);
   fails += onion_test_run("i18n.th", test_th);
   fails += onion_test_run("i18n.apply_ui_lang", test_apply_ui_lang);
-  fails += onion_test_run("i18n.system_lang_host_fallback",
-                          test_system_lang_host_fallback);
+  fails += onion_test_run("i18n.system_lang_follows_query",
+                          test_system_lang_follows_query);
+  fails += onion_test_run("i18n.system_lang_query_failure_keeps_current",
+                          test_system_lang_query_failure_keeps_current);
   fails += onion_test_run("i18n.missing_key", test_missing_key);
   fails += onion_test_run("i18n.format", test_format);
   return fails;