diff --git a/src/nvhttp.cpp b/src/nvhttp.cpp
index 76bf6b71569..1cdb6dfbc97 100644
--- a/src/nvhttp.cpp
+++ b/src/nvhttp.cpp
@@ -312,9 +312,15 @@ namespace nvhttp {
   save_state() {
     pt::ptree root;
 
-    if (fs::exists(config::nvhttp.file_state)) {
+    fs::path state_path(config::nvhttp.file_state);
+    if (fs::exists(state_path)) {
       try {
-        pt::read_json(config::nvhttp.file_state, root);
+        std::ifstream ifs(state_path);
+        if (!ifs.is_open()) {
+          BOOST_LOG(error) << "Couldn't open "sv << config::nvhttp.file_state << " for reading";
+          return;
+        }
+        pt::read_json(ifs, root);
       }
       catch (std::exception &e) {
         BOOST_LOG(error) << "Couldn't read "sv << config::nvhttp.file_state << ": "sv << e.what();
@@ -339,7 +345,12 @@ namespace nvhttp {
     root.add_child("root.named_devices"s, named_cert_nodes);
 
     try {
-      pt::write_json(config::nvhttp.file_state, root);
+      std::ofstream ofs(state_path);
+      if (!ofs.is_open()) {
+        BOOST_LOG(error) << "Couldn't open "sv << config::nvhttp.file_state << " for writing";
+        return;
+      }
+      pt::write_json(ofs, root);
     }
     catch (std::exception &e) {
       BOOST_LOG(error) << "Couldn't write "sv << config::nvhttp.file_state << ": "sv << e.what();
@@ -349,7 +360,8 @@ namespace nvhttp {
 
   void
   load_state() {
-    if (!fs::exists(config::nvhttp.file_state)) {
+    fs::path state_path(config::nvhttp.file_state);
+    if (!fs::exists(state_path)) {
       BOOST_LOG(debug) << "File "sv << config::nvhttp.file_state << " doesn't exist"sv;
       http::unique_id = uuid_util::uuid_t::generate().string();
       return;
@@ -357,7 +369,13 @@ namespace nvhttp {
 
     pt::ptree tree;
     try {
-      pt::read_json(config::nvhttp.file_state, tree);
+      std::ifstream ifs(state_path);
+      if (!ifs.is_open()) {
+        BOOST_LOG(error) << "Couldn't open "sv << config::nvhttp.file_state << " for reading";
+        http::unique_id = uuid_util::uuid_t::generate().string();
+        return;
+      }
+      pt::read_json(ifs, tree);
     }
     catch (std::exception &e) {
       BOOST_LOG(error) << "Couldn't read "sv << config::nvhttp.file_state << ": "sv << e.what();
diff --git a/src/platform/windows/input.cpp b/src/platform/windows/input.cpp
index 9f2908225ae..9401109f5d1 100644
--- a/src/platform/windows/input.cpp
+++ b/src/platform/windows/input.cpp
@@ -1287,6 +1287,9 @@ namespace platf {
 
     int chars = MultiByteToWideChar(CP_UTF8, MB_ERR_INVALID_CHARS, utf8, size, wide, size);
     if (chars <= 0) {
+      auto winerr = GetLastError();
+      BOOST_LOG(warning) << "unicode(): MultiByteToWideChar failed, error=" << winerr
+                         << ", size=" << size;
       return;
     }
 
diff --git a/src/platform/windows/misc.cpp b/src/platform/windows/misc.cpp
index f97fb7564a7..0c7ee209488 100644
--- a/src/platform/windows/misc.cpp
+++ b/src/platform/windows/misc.cpp
@@ -1036,7 +1036,7 @@ namespace platf {
    */
   bp::child
   run_command(bool elevated, bool interactive, const std::string &cmd, boost::filesystem::path &working_dir, const bp::environment &env, FILE *file, std::error_code &ec, bp::group *group) {
-    std::wstring start_dir = from_utf8(working_dir.string());
+    std::wstring start_dir = working_dir.wstring();
     HANDLE job = group ? group->native_handle() : nullptr;
     STARTUPINFOEXW startup_info = create_startup_info(file, job ? &job : nullptr, ec);
     PROCESS_INFORMATION process_info;
@@ -2012,12 +2012,38 @@ namespace platf {
       return {};
     }
 
-    // Get the output size required to store the string
+    // Get the output size required to store the string (strict UTF-8 validation)
     auto output_size = MultiByteToWideChar(CP_UTF8, MB_ERR_INVALID_CHARS, string.data(), string.size(), nullptr, 0);
     if (output_size == 0) {
       auto winerr = GetLastError();
-      BOOST_LOG(error) << "Failed to get UTF-16 buffer size: "sv << winerr;
-      return {};
+
+      // Log hex dump of the first bytes to help diagnose the invalid string
+      std::ostringstream hex_dump;
+      auto dump_len = std::min<size_t>(string.size(), 64);
+      for (size_t i = 0; i < dump_len; i++) {
+        hex_dump << std::hex << std::setfill('0') << std::setw(2)
+                 << (static_cast<unsigned>(string[i]) & 0xFF);
+        if (i + 1 < dump_len) hex_dump << ' ';
+      }
+      BOOST_LOG(error) << "Failed to get UTF-16 buffer size: "sv << winerr
+                       << " (len=" << string.size()
+                       << ", hex=[" << hex_dump.str() << "]"
+                       << ", str=\"" << string.substr(0, 64) << "\")";
+
+      // Fallback: try converting from the system's default ANSI code page (e.g. GBK on Chinese Windows)
+      output_size = MultiByteToWideChar(CP_ACP, 0, string.data(), string.size(), nullptr, 0);
+      if (output_size == 0) {
+        BOOST_LOG(error) << "Fallback ANSI conversion also failed: "sv << GetLastError();
+        return {};
+      }
+      BOOST_LOG(warning) << "from_utf8: falling back to ANSI code page conversion for non-UTF-8 string";
+
+      std::wstring output(output_size, L'\0');
+      output_size = MultiByteToWideChar(CP_ACP, 0, string.data(), string.size(), output.data(), output.size());
+      if (output_size == 0) {
+        return {};
+      }
+      return output;
     }
 
     // Perform the conversion