Merge commit '28cbea46ab44105fde928653507add5d9d4873f4' into fix/pr168-save-safety

runtime/CMakeLists.txt

@@ -277,6 +277,13 @@ target_link_libraries(mkw_platform_paths_tests PRIVATE mkw_platform)
 target_compile_features(mkw_platform_paths_tests PRIVATE cxx_std_17)
 add_test(NAME mkw_platform_paths_tests COMMAND mkw_platform_paths_tests)
 
+add_executable(mkw_nand_settings_tests "${CMAKE_CURRENT_LIST_DIR}/tests/nand_settings_tests.cpp")
+find_package(Threads REQUIRED)
+target_link_libraries(mkw_nand_settings_tests PRIVATE Threads::Threads)
+target_include_directories(mkw_nand_settings_tests PRIVATE "${CMAKE_CURRENT_LIST_DIR}/include")
+target_compile_features(mkw_nand_settings_tests PRIVATE cxx_std_17)
+add_test(NAME mkw_nand_settings_tests COMMAND mkw_nand_settings_tests)
+
 # The input expression engine is self-contained, so it can be exercised without
 # linking the runtime or SDL.
 add_executable(mkw_input_expr_tests

runtime/include/console_identity.h

@@ -1,38 +1,28 @@
 #pragma once
 
-#include "runtime_config.h"
+#include "nand_path.h"
+#include "nand_settings.h"
 
-#include <algorithm>
 #include <array>
-#include <cctype>
 #include <cstddef>
 #include <cstdint>
-#include <filesystem>
-#include <fstream>
 #include <iomanip>
-#include <optional>
-#include <random>
 #include <sstream>
 #include <string>
-#include <string_view>
 #include <utility>
 
 namespace RuntimeConsoleIdentity {
 
 struct Identity {
     std::string serial;
+    std::string productCode;
+    std::string area;
+    std::string gameRegion;
     std::array<uint8_t, 6> mac;
 };
 
-inline bool IsValidSerial(const std::string& serial) {
-    return serial.size() == 9 &&
-           serial != "000000000" &&
-           std::all_of(serial.begin(), serial.end(),
-                       [](unsigned char value) { return std::isdigit(value) != 0; });
-}
-
 inline Identity FromSerial(std::string serial) {
-    // Keep Nintendo's Wii OUI. The suffix is derived from the persisted serial
+    // Keep Nintendo's Wii OUI. The suffix is derived from the NAND serial
     // so every API exposes one coherent, stable virtual-console identity.
     uint32_t hash = 2166136261u;
     for (const unsigned char value : serial) {
@@ -46,6 +36,7 @@ inline Identity FromSerial(std::string serial) {
 
     return {
         std::move(serial),
+        {}, {}, {},
         {
             0x00,
             0x09,
@@ -57,83 +48,23 @@ inline Identity FromSerial(std::string serial) {
     };
 }
 
-inline std::optional<std::string> ReadSerial(const std::filesystem::path& path) {
-    std::ifstream input(path);
-    std::string line;
-    if (!input || !std::getline(input, line)) {
-        return std::nullopt;
+inline Identity LoadFromNand() {
+    const auto root = RuntimeNandPath::DiscoverNandRootPath();
+    const auto settings = RuntimeNandSettings::Read(root);
+    if (!settings || !RuntimeNandSettings::HasIdentity(*settings)) {
+        RuntimeNandPath::FailNandRoot(
+            "NAND setting.txt is missing or has invalid console identity fields (SERNO, CODE, AREA, GAME)",
+            root / "title/00000001/00000002/data/setting.txt");
     }
-    constexpr std::string_view prefix = "serial=";
-    if (line.rfind(prefix, 0) != 0) {
-        return std::nullopt;
-    }
-    std::string serial = line.substr(prefix.size());
-    if (!IsValidSerial(serial)) {
-        return std::nullopt;
-    }
-    return serial;
-}
-
-inline bool WriteSerial(const std::filesystem::path& path, const std::string& serial) {
-    std::error_code ec;
-    std::filesystem::create_directories(path.parent_path(), ec);
-    if (ec) {
-        return false;
-    }
-
-    std::filesystem::path temporary = path;
-    temporary += ".tmp";
-    {
-        std::ofstream output(temporary, std::ios::trunc);
-        if (!output) {
-            return false;
-        }
-        output << "serial=" << serial << '\n';
-        output.close();
-        if (!output) {
-            return false;
-        }
-    }
-
-    std::filesystem::rename(temporary, path, ec);
-    if (!ec) {
-        return true;
-    }
-    std::filesystem::remove(temporary, ec);
-    return false;
-}
-
-inline std::string GenerateSerial() {
-    std::random_device entropy;
-    std::seed_seq seed{
-        entropy(),
-        entropy(),
-        entropy(),
-        entropy(),
-    };
-    std::mt19937 generator(seed);
-    std::uniform_int_distribution<uint32_t> distribution(100000000u, 999999999u);
-    return std::to_string(distribution(generator));
-}
-
-inline Identity LoadOrCreate(const std::filesystem::path& path) {
-    if (const auto serial = ReadSerial(path)) {
-        return FromSerial(*serial);
-    }
-
-    const std::string generated = GenerateSerial();
-    if (WriteSerial(path, generated)) {
-        return FromSerial(generated);
-    }
-
-    // Remain operational in a read-only environment. This fallback matches
-    // Dolphin's deterministic serial while keeping the same valid identity shape.
-    return FromSerial("123456789");
+    Identity identity = FromSerial(settings->at("SERNO"));
+    identity.productCode = settings->at("CODE");
+    identity.area = settings->at("AREA");
+    identity.gameRegion = settings->at("GAME");
+    return identity;
 }
 
 inline const Identity& Current() {
-    static const Identity identity =
-        LoadOrCreate(RuntimeConfigFile::ApplicationDataDirectory() / "ConsoleIdentity.txt");
+    static const Identity identity = LoadFromNand();
     return identity;
 }
 

runtime/include/nand_path.h

@@ -1,6 +1,7 @@
 #pragma once
 
 #include "runtime_config.h"
+#include "nand_settings.h"
 #include "runtime_log.h"
 #include "system_bridge.h"
 
@@ -163,7 +164,7 @@ inline std::filesystem::path CreateManagedNandRoot() {
     return root;
 }
 
-inline std::filesystem::path DiscoverNandRootPath() {
+inline std::filesystem::path ResolveNandRootPath() {
     const std::string configPath = RuntimeConfigFile::NandRoot();
     if (!configPath.empty()) {
         const auto path = ResolveConfiguredPath(configPath);
@@ -179,4 +180,16 @@ inline std::filesystem::path DiscoverNandRootPath() {
     return CreateManagedNandRoot();
 }
 
+inline std::filesystem::path DiscoverNandRootPath() {
+    static const auto root = [] {
+        const auto resolved = ResolveNandRootPath();
+        std::string error;
+        if (!RuntimeNandSettings::Ensure(resolved, error)) {
+            FailNandRoot(error.c_str(), RuntimeNandSettings::FilePath(resolved));
+        }
+        return resolved;
+    }();
+    return root;
+}
+
 } // namespace RuntimeNandPath

runtime/include/nand_settings.h

@@ -0,0 +1,199 @@
+#pragma once
+
+#include <array>
+#include <atomic>
+#include <chrono>
+#include <ctime>
+#include <cstdint>
+#include <filesystem>
+#include <fstream>
+#include <map>
+#include <optional>
+#include <string>
+#include <utility>
+
+#ifdef _WIN32
+#include <windows.h>
+#else
+#include <unistd.h>
+#endif
+
+namespace RuntimeNandSettings {
+
+using Settings = std::map<std::string, std::string>;
+
+inline std::filesystem::path FilePath(const std::filesystem::path& root) {
+    return root / "title/00000001/00000002/data/setting.txt";
+}
+
+// Wii setting.txt is a 256-byte buffer encrypted with a rotating XOR key.
+inline std::optional<Settings> Read(const std::filesystem::path& nandRoot) {
+    std::ifstream input(FilePath(nandRoot), std::ios::binary);
+    std::array<uint8_t, 256> bytes{};
+    if (!input.read(reinterpret_cast<char*>(bytes.data()), bytes.size())) {
+        return std::nullopt;
+    }
+    uint32_t key = 0x73B5DBFAu;
+    std::string decoded;
+    for (const uint8_t byte : bytes) {
+        const char value = static_cast<char>(byte ^ static_cast<uint8_t>(key));
+        key = (key << 1) | (key >> 31);
+        if (value == '\0') {
+            break;
+        }
+        if (value != '\r') {
+            decoded += value;
+        }
+    }
+    Settings settings;
+    for (size_t start = 0; start < decoded.size();) {
+        const size_t end = decoded.find('\n', start);
+        const std::string line = decoded.substr(start, end - start);
+        const size_t equals = line.find('=');
+        if (equals != std::string::npos && equals != 0) {
+            settings.emplace(line.substr(0, equals), line.substr(equals + 1));
+        }
+        if (end == std::string::npos) {
+            break;
+        }
+        start = end + 1;
+    }
+    return settings;
+}
+
+inline bool HasIdentity(const Settings& settings) {
+    const auto serial = settings.find("SERNO");
+    if (serial == settings.end() || serial->second.empty() || serial->second.size() > 9 ||
+        serial->second.find_first_not_of("0123456789") != std::string::npos ||
+        serial->second.find_first_not_of('0') == std::string::npos) {
+        return false;
+    }
+    for (const auto& field : {std::pair{"CODE", 5u}, {"AREA", 3u}, {"GAME", 2u}}) {
+        const auto value = settings.find(field.first);
+        if (value == settings.end() || value->second.empty() ||
+            value->second.size() > field.second) {
+            return false;
+        }
+    }
+    return true;
+}
+
+// Dolphin's normal (non-deterministic) first-boot algorithm. It is independent
+// of the ES device ID. Matching another NAND requires that NAND's saved serial.
+inline std::string GenerateSerial(std::time_t now) {
+    if (now < 0) {
+        return {};
+    }
+    const auto digits = std::to_string(now % 1000000000);
+    return std::string(9 - digits.size(), '0') + digits;
+}
+
+// This recompilation targets the European disc. These are Dolphin's PAL boot
+// defaults; an existing setting.txt always takes precedence, in every region.
+inline std::optional<std::array<uint8_t, 256>> EncodeNew(const std::string& serial) {
+    const Settings identity{{"SERNO", serial}, {"CODE", "LEH"}, {"AREA", "EUR"}, {"GAME", "EU"}};
+    if (!HasIdentity(identity)) {
+        return std::nullopt;
+    }
+    std::array<uint8_t, 256> bytes{};
+    size_t position = 0;
+    uint32_t key = 0x73B5DBFAu;
+    const auto writeByte = [&](char value) {
+        bytes[position++] = static_cast<uint8_t>(value) ^ static_cast<uint8_t>(key);
+        key = (key << 1) | (key >> 31);
+    };
+    for (const std::string& line : {std::string("AREA=EUR\r\n"), std::string("MODEL=RVL-001(EUR)\r\n"),
+             std::string("DVD=0\r\n"), std::string("MPCH=0x7FFE\r\n"), std::string("CODE=LEH\r\n"),
+             "SERNO=" + serial + "\r\n", std::string("VIDEO=PAL\r\n"), std::string("GAME=EU\r\n")}) {
+        for (;;) {
+            if (position + line.size() > bytes.size()) {
+                return std::nullopt;
+            }
+            const auto start = position;
+            const auto savedKey = key;
+            bool hasNull = false;
+            for (const char value : line) {
+                writeByte(value);
+                hasNull |= bytes[position - 1] == 0;
+            }
+            if (!hasNull) {
+                break;
+            }
+            // Nintendo stops at an encoded NUL. Dolphin inserts an extra LF
+            // before this line and retries with the shifted encryption key.
+            position = start;
+            key = savedKey;
+            writeByte('\n');
+        }
+    }
+    return bytes; // The unused tail stays raw zero, as in Dolphin.
+}
+
+// Never replace an existing file, including an unreadable or damaged one.
+// Publish a complete file atomically so simultaneous launches use one identity.
+inline bool Ensure(const std::filesystem::path& root, std::string& error,
+                   std::time_t now = std::time(nullptr)) {
+    const auto path = FilePath(root);
+    std::error_code ec;
+    const auto status = std::filesystem::symlink_status(path, ec);
+    if (ec && ec != std::errc::no_such_file_or_directory) {
+        error = "Cannot inspect NAND setting.txt: " + ec.message();
+        return false;
+    }
+    if (std::filesystem::exists(status)) {
+        const auto existing = Read(root);
+        if (existing && HasIdentity(*existing)) {
+            return true;
+        }
+        error = "Existing NAND setting.txt is unreadable or invalid; restore it from this console's backup";
+        return false;
+    }
+
+    const auto bytes = EncodeNew(GenerateSerial(now));
+    if (!bytes) {
+        error = "Cannot initialize NAND settings: invalid system clock";
+        return false;
+    }
+    ec.clear();
+    std::filesystem::create_directories(path.parent_path(), ec);
+    if (ec) {
+        error = "Cannot create NAND settings directory: " + ec.message();
+        return false;
+    }
+    static std::atomic<unsigned> sequence{0};
+    const auto scratch = path.parent_path() / (".setting-init-" + std::to_string(
+        std::chrono::steady_clock::now().time_since_epoch().count()) + "-" + std::to_string(sequence++));
+    if (!std::filesystem::create_directory(scratch, ec)) {
+        error = "Cannot create temporary NAND settings directory: " + ec.message();
+        return false;
+    }
+    const auto temporary = scratch / "setting.txt";
+    bool written = false;
+    {
+        std::ofstream output(temporary, std::ios::binary);
+        output.write(reinterpret_cast<const char*>(bytes->data()), bytes->size());
+        output.close();
+        written = static_cast<bool>(output);
+    }
+    bool published = false;
+    if (written) {
+#ifdef _WIN32
+        published = MoveFileExW(temporary.c_str(), path.c_str(), MOVEFILE_WRITE_THROUGH) != 0;
+#else
+        published = ::link(temporary.c_str(), path.c_str()) == 0;
+#endif
+    }
+    std::filesystem::remove(temporary, ec);
+    std::filesystem::remove(scratch, ec);
+    // A competing launcher may have published its settings first. Always read
+    // the winner from NAND rather than using our unpersisted candidate serial.
+    const auto persisted = Read(root);
+    if (persisted && HasIdentity(*persisted)) {
+        return true;
+    }
+    error = published ? "Cannot read newly initialized NAND setting.txt" :
+                        "Cannot persist NAND setting.txt; check NAND directory permissions";
+    return false;
+}
+
+} // namespace RuntimeNandSettings

runtime/src/hle/sc.cpp

@@ -12,7 +12,25 @@
 
 namespace {
 
-constexpr uint32_t kPalProductRegion = 2;
+// Use the SDK's own value tables, including its unknown-region result.
+uint32_t LookupProductRegion(uint32_t table, uint32_t stride, uint32_t count,
+                             const std::string& value) {
+    for (uint32_t index = 0; index < count; ++index) {
+        const uint32_t entry = table + index * stride;
+        if (!Memory::Contains(entry, stride)) {
+            break;
+        }
+        const auto* bytes = static_cast<const uint8_t*>(Memory::GetPointer(entry, stride));
+        if (bytes[0] == 0xFF) {
+            break;
+        }
+        if (value.size() < stride - 1 &&
+            std::memcmp(bytes + 1, value.c_str(), value.size() + 1) == 0) {
+            return bytes[0];
+        }
+    }
+    return 0xFFFFFFFFu;
+}
 
 } // namespace
 
@@ -50,16 +68,12 @@ extern "C" uint32_t SCGetEuRgb60Mode_HLE()
 
 PPC_NATIVE_OVERRIDE(801B1CAC, SCGetEuRgb60Mode_HLE, uint32_t, (), ());
 
-// The managed NAND intentionally starts without a console-owned setting.txt.
-// DWC nevertheless requires the Wii product code and serial number so it can
-// include csnum in NAS authentication. Expose one stable virtual-console
-// identity without requiring or mutating a user's real NAND.
+// Expose the selected emulated NAND identity through the SDK SC APIs.
 
 extern "C" uint32_t SCGetProductArea_HLE()
 {
-    // The PAL setting.txt AREA value is "EUR". The SDK's lookup table at
-    // 0x8029CEB0 maps JPN=0, USA=1, EUR=2.
-    return kPalProductRegion;
+    return LookupProductRegion(0x8029CEB0u, 5, 13,
+                               RuntimeConsoleIdentity::Current().area);
 }
 
 PPC_NATIVE_OVERRIDE(801B23A0, SCGetProductArea_HLE, uint32_t, (), ());
@@ -68,12 +82,13 @@ extern "C" uint32_t SCGetProductCode_HLE()
 {
     // Original PAL SC storage for the six-byte CODE value.
     constexpr uint32_t kProductCodeAddress = 0x803869E0u;
-    static constexpr char kProductCode[] = "LEH";
-    if (!Memory::Contains(kProductCodeAddress, sizeof(kProductCode))) {
+    const std::string& productCode = RuntimeConsoleIdentity::Current().productCode;
+    const size_t size = productCode.size() + 1;
+    if (!Memory::Contains(kProductCodeAddress, size)) {
         return 0;
     }
-    std::memcpy(Memory::GetPointer(kProductCodeAddress, sizeof(kProductCode)),
-                kProductCode, sizeof(kProductCode));
+    std::memcpy(Memory::GetPointer(kProductCodeAddress, size),
+                productCode.c_str(), size);
     return kProductCodeAddress;
 }
 
@@ -94,9 +109,8 @@ PPC_NATIVE_OVERRIDE(801B2460, SCGetProductSN_HLE, uint32_t, (uint32_t serialAddr
 
 extern "C" uint32_t SCGetProductGameRegion_HLE()
 {
-    // The PAL setting.txt GAME value is "EU". The SDK's own lookup table at
-    // 0x8029CEF8 maps JP=0, US=1, EU=2.
-    return kPalProductRegion;
+    return LookupProductRegion(0x8029CEF8u, 4, 4,
+                               RuntimeConsoleIdentity::Current().gameRegion);
 }
 
 PPC_NATIVE_OVERRIDE(801B24C8, SCGetProductGameRegion_HLE, uint32_t, (), ());

runtime/src/settings_overlay.cpp

@@ -483,11 +483,6 @@ void DrawRumbleSettings() {
                 PAD_MOTOR_STOP_HARD, PAD_MOTOR_STOP_HARD, PAD_MOTOR_STOP_HARD, PAD_MOTOR_STOP_HARD,
             };
             PADControlAllMotors(stopAll.data());
-#if defined(_WIN32)
-            for (uint32_t port = 0; port < PAD_MAX_CONTROLLERS; ++port) {
-                Wup028Adapter::SetRumble(port, false);
-            }
-#endif
         }
     }
     if (ImGui::IsItemHovered()) {

runtime/tests/nand_settings_tests.cpp

@@ -0,0 +1,151 @@
+#include "nand_settings.h"
+
+#include <chrono>
+#include <iostream>
+#include <stdexcept>
+#include <thread>
+#include <vector>
+
+static void Require(bool condition, const char* message = "NAND settings check failed") {
+    if (!condition) {
+        throw std::runtime_error(message);
+    }
+}
+
+static std::string ReadBytes(const std::filesystem::path& path) {
+    std::ifstream input(path, std::ios::binary);
+    return {std::istreambuf_iterator<char>(input), std::istreambuf_iterator<char>()};
+}
+
+int main() {
+    const auto root = std::filesystem::temp_directory_path() /
+        ("wiicomp-nand-settings-" + std::to_string(
+            std::chrono::steady_clock::now().time_since_epoch().count()));
+    const auto path = root / "title/00000001/00000002/data/setting.txt";
+    try {
+        using namespace RuntimeNandSettings;
+        Require(GenerateSerial(1800000123) == "800000123", "Dolphin timestamp modulo");
+        Require(GenerateSerial(1000000001) == "000000001", "Dolphin leading zero padding");
+        Require(GenerateSerial(-1).empty(), "Invalid clock must not supply an identity");
+        // Golden bytes generated by Dolphin's unmodified SettingsHandler.cpp
+        // (upstream 2026-09-06), PAL boot fields and synthetic serial 000000001.
+        // Everything after this prefix is raw zero padding to 256 bytes.
+        const std::string goldenHex =
+            "bba6ac929a0bc96b7eed83d27f33a1e7e73d9b836d8b47c59ee23df6b275baab"
+            "bec9d9dead03cc7a3bdafee50c30ab9fb86194e119fe4ba19eff62d5ec3aacb3"
+            "b5c9d9e3977eac0943d7ff903120a49ef024eafe1cf77be79cf6229a823aabf0f0";
+        std::array<uint8_t, 256> golden{};
+        for (size_t i = 0; i < goldenHex.size() / 2; ++i) {
+            golden[i] = static_cast<uint8_t>(std::stoul(goldenHex.substr(i * 2, 2), nullptr, 16));
+        }
+        Require(EncodeNew("000000001") == golden, "Exact Dolphin writer golden fixture");
+        std::string error;
+        Require(!RuntimeNandSettings::Read(root));
+        Require(!std::filesystem::exists(root));
+        std::filesystem::create_directories(path.parent_path());
+        const std::string plain = "AREA=USA\r\n\nCODE=LU\r\nSERNO=987654321\r\nGAME=US\r\n";
+        std::array<uint8_t, 256> fixture{};
+        for (size_t i = 0; i < fixture.size(); ++i) {
+            const unsigned shift = i % 32;
+            const uint32_t key = shift == 0 ? 0x73B5DBFAu :
+                (0x73B5DBFAu << shift) | (0x73B5DBFAu >> (32 - shift));
+            fixture[i] = static_cast<uint8_t>(key) ^ (i < plain.size() ? plain[i] : 0);
+        }
+        {
+            std::ofstream output(path, std::ios::binary);
+            output.write(reinterpret_cast<const char*>(fixture.data()), fixture.size());
+        }
+        auto settings = RuntimeNandSettings::Read(root);
+        Require(settings && RuntimeNandSettings::HasIdentity(*settings));
+        Require(settings->at("SERNO") == "987654321" && settings->at("CODE") == "LU");
+        Require(settings->at("AREA") == "USA" && settings->at("GAME") == "US");
+        Require(Ensure(root, error, 1800000123), "Existing imported NAND must work");
+        std::array<uint8_t, 256> after{};
+        {
+            std::ifstream input(path, std::ios::binary);
+            input.read(reinterpret_cast<char*>(after.data()), after.size());
+        }
+        Require(after == fixture);
+        for (const auto serial : {"", "000000000", "1234567890", "123ABC789"}) {
+            (*settings)["SERNO"] = serial;
+            Require(!RuntimeNandSettings::HasIdentity(*settings));
+        }
+        (*settings)["SERNO"] = "012345678";
+        Require(RuntimeNandSettings::HasIdentity(*settings));
+        (*settings)["CODE"] = "TOOLONG";
+        Require(!RuntimeNandSettings::HasIdentity(*settings));
+        (*settings)["CODE"] = "LEH";
+        settings->erase("GAME");
+        Require(!RuntimeNandSettings::HasIdentity(*settings));
+        std::filesystem::resize_file(path, 128);
+        Require(!RuntimeNandSettings::Read(root));
+        const auto damaged = ReadBytes(path);
+        Require(!Ensure(root, error, 1800000123), "Do not replace a truncated identity");
+        Require(ReadBytes(path) == damaged, "Damaged file must remain untouched");
+
+        const auto fresh = root / "fresh";
+        Require(Ensure(fresh, error, 1800000123), "Missing setting.txt must initialize");
+        const auto generated = Read(fresh);
+        Require(generated && HasIdentity(*generated), "Generated file must be readable");
+        Require(generated->at("SERNO") == "800000123", "Persist Dolphin-generated serial");
+        Require(generated->at("CODE") == "LEH" && generated->at("AREA") == "EUR" &&
+                generated->at("GAME") == "EU", "PAL first-boot fields");
+        Require(generated->at("MODEL") == "RVL-001(EUR)" && generated->at("VIDEO") == "PAL" &&
+                generated->at("DVD") == "0" && generated->at("MPCH") == "0x7FFE",
+                "Complete Dolphin boot settings");
+        const auto firstBoot = ReadBytes(FilePath(fresh));
+        Require(firstBoot.size() == 256 && firstBoot.back() == 0, "Dolphin buffer size and raw zero padding");
+        Require(Ensure(fresh, error, 1900000999), "Second boot");
+        Require(ReadBytes(FilePath(fresh)) == firstBoot, "Second boot must not change any bytes");
+
+        const auto blocked = root / "blocked";
+        { std::ofstream output(blocked); output << "file obstructing NAND directory"; }
+        Require(!Ensure(blocked, error, 1800000123), "Write failure must not return an ephemeral identity");
+        Require(!Ensure(root / "bad-clock", error, -1), "Clock failure must not initialize");
+
+        const auto concurrent = root / "concurrent";
+        std::array<bool, 16> results{};
+        std::vector<std::thread> workers;
+        for (size_t i = 0; i < results.size(); ++i) {
+            workers.emplace_back([&, i] {
+                std::string detail;
+                results[i] = Ensure(concurrent, detail, 1800000001 + i);
+            });
+        }
+        for (auto& worker : workers) worker.join();
+        for (const bool result : results) Require(result, "Concurrent boot must read the persisted winner");
+        const auto winner = ReadBytes(FilePath(concurrent));
+        Require(Read(concurrent) && HasIdentity(*Read(concurrent)), "Concurrent boot must persist valid settings");
+        Require(Ensure(concurrent, error, 1900000999), "Boot after concurrent initialization");
+        Require(ReadBytes(FilePath(concurrent)) == winner, "Concurrent winner must remain stable");
+
+        // Independently decode as Nintendo does: stop at the first encoded NUL.
+        // Exercise serials that force Dolphin's extra-LF escaping, not only
+        // values that happen to work with a plain rotating-XOR encoder.
+        bool sawExtraLf = false;
+        for (int serial = 1; serial <= 10000; ++serial) {
+            const auto number = GenerateSerial(1000000000 + serial);
+            const auto encoded = EncodeNew(number);
+            Require(encoded.has_value(), "Serial encoding must fit");
+            std::string decoded;
+            for (size_t i = 0; i < encoded->size() && (*encoded)[i] != 0; ++i) {
+                const unsigned shift = i % 32;
+                const uint32_t key = shift == 0 ? 0x73B5DBFAu :
+                    (0x73B5DBFAu << shift) | (0x73B5DBFAu >> (32 - shift));
+                decoded += static_cast<char>((*encoded)[i] ^ static_cast<uint8_t>(key));
+            }
+            Require(decoded.find("SERNO=" + number + "\r\n") != std::string::npos &&
+                    decoded.find("GAME=EU\r\n") != std::string::npos,
+                    "Encoded NUL must not truncate settings");
+            sawExtraLf |= decoded.find("\r\n\n") != std::string::npos;
+        }
+        Require(sawExtraLf, "Exercise Dolphin LF escape path");
+        std::filesystem::remove_all(root);
+        std::cout << "NAND settings checks passed\n";
+        return 0;
+    } catch (const std::exception& error) {
+        std::filesystem::remove_all(root);
+        std::cerr << error.what() << '\n';
+        return 1;
+    }
+}