feat: add silent NTP time sync on boot via saved WiFi credentials

New "Auto Sync on Boot" toggle in Clock Settings. When enabled, a
background FreeRTOS task scans for saved WiFi networks at boot,
connects, syncs time via NTP, then tears down WiFi — all without
blocking boot or requiring user interaction. If no saved network is
found after two scan attempts (with a 3-second retry gap), it bails
silently.

Conflict guards (BootNtpSync::cancel()) added to all WiFi-using
activities so the background task cleans up before any user-initiated
WiFi flow. Also fixes clock not appearing in the header until a button
press by detecting the invalid→valid time transition after NTP sync.

Made-with: Cursor

lib/I18n/I18nKeys.h

@@ -400,6 +400,7 @@ enum class StrId : uint16_t {
   STR_INDEXING_STATUS_ICON,
   STR_SYNC_CLOCK,
   STR_TIME_SYNCED,
+  STR_AUTO_NTP_SYNC,
   STR_MANAGE_BOOK,
   STR_ARCHIVE_BOOK,
   STR_UNARCHIVE_BOOK,

lib/I18n/translations/czech.yaml

@@ -343,3 +343,4 @@ STR_INDEXING_STATUS_TEXT: "Text stavového řádku"
 STR_INDEXING_STATUS_ICON: "Ikona stavového řádku"
 STR_SYNC_CLOCK: "Sync Clock"
 STR_TIME_SYNCED: "Time synced!"
+STR_AUTO_NTP_SYNC: "Auto Sync on Boot"

lib/I18n/translations/english.yaml

@@ -364,6 +364,7 @@ STR_INDEXING_STATUS_TEXT: "Status Bar Text"
 STR_INDEXING_STATUS_ICON: "Status Bar Icon"
 STR_SYNC_CLOCK: "Sync Clock"
 STR_TIME_SYNCED: "Time synced!"
+STR_AUTO_NTP_SYNC: "Auto Sync on Boot"
 STR_MANAGE_BOOK: "Manage Book"
 STR_ARCHIVE_BOOK: "Archive Book"
 STR_UNARCHIVE_BOOK: "Unarchive Book"

lib/I18n/translations/french.yaml

@@ -343,3 +343,4 @@ STR_INDEXING_STATUS_TEXT: "Texte barre d'état"
 STR_INDEXING_STATUS_ICON: "Icône barre d'état"
 STR_SYNC_CLOCK: "Sync Clock"
 STR_TIME_SYNCED: "Time synced!"
+STR_AUTO_NTP_SYNC: "Auto Sync on Boot"

lib/I18n/translations/german.yaml

@@ -343,3 +343,4 @@ STR_INDEXING_STATUS_TEXT: "Statusleistentext"
 STR_INDEXING_STATUS_ICON: "Statusleistensymbol"
 STR_SYNC_CLOCK: "Sync Clock"
 STR_TIME_SYNCED: "Time synced!"
+STR_AUTO_NTP_SYNC: "Auto Sync on Boot"

lib/I18n/translations/portuguese.yaml

@@ -343,3 +343,4 @@ STR_INDEXING_STATUS_TEXT: "Texto da barra"
 STR_INDEXING_STATUS_ICON: "Ícone da barra"
 STR_SYNC_CLOCK: "Sync Clock"
 STR_TIME_SYNCED: "Time synced!"
+STR_AUTO_NTP_SYNC: "Auto Sync on Boot"

lib/I18n/translations/romanian.yaml

@@ -318,3 +318,4 @@ STR_EMBEDDED_STYLE: "Stil încorporat"
 STR_OPDS_SERVER_URL: "URL server OPDS"
 STR_SYNC_CLOCK: "Sync Clock"
 STR_TIME_SYNCED: "Time synced!"
+STR_AUTO_NTP_SYNC: "Auto Sync on Boot"

lib/I18n/translations/russian.yaml

@@ -343,3 +343,4 @@ STR_INDEXING_STATUS_TEXT: "Текст в строке"
 STR_INDEXING_STATUS_ICON: "Иконка в строке"
 STR_SYNC_CLOCK: "Sync Clock"
 STR_TIME_SYNCED: "Time synced!"
+STR_AUTO_NTP_SYNC: "Auto Sync on Boot"

lib/I18n/translations/spanish.yaml

@@ -343,3 +343,4 @@ STR_INDEXING_STATUS_TEXT: "Texto barra estado"
 STR_INDEXING_STATUS_ICON: "Icono barra estado"
 STR_SYNC_CLOCK: "Sync Clock"
 STR_TIME_SYNCED: "Time synced!"
+STR_AUTO_NTP_SYNC: "Auto Sync on Boot"

lib/I18n/translations/swedish.yaml

@@ -343,3 +343,4 @@ STR_INDEXING_STATUS_TEXT: "Statusfältstext"
 STR_INDEXING_STATUS_ICON: "Statusfältsikon"
 STR_SYNC_CLOCK: "Sync Clock"
 STR_TIME_SYNCED: "Time synced!"
+STR_AUTO_NTP_SYNC: "Auto Sync on Boot"

src/CrossPointSettings.cpp

@@ -144,6 +144,7 @@ uint8_t CrossPointSettings::writeSettings(FsFile& file, bool count_only) const {
   writer.writeItem(file, timezone);
   writer.writeItem(file, timezoneOffsetHours);
   writer.writeItem(file, indexingDisplay);
+  writer.writeItem(file, autoNtpSync);
 
   return writer.item_count;
 }
@@ -288,6 +289,8 @@ bool CrossPointSettings::loadFromFile() {
     if (++settingsRead >= fileSettingsCount) break;
     readAndValidate(inputFile, indexingDisplay, INDEXING_DISPLAY_COUNT);
     if (++settingsRead >= fileSettingsCount) break;
+    serialization::readPod(inputFile, autoNtpSync);
+    if (++settingsRead >= fileSettingsCount) break;
   } while (false);
 
   if (frontButtonMappingRead) {

src/CrossPointSettings.h

@@ -227,6 +227,9 @@ class CrossPointSettings {
   // Custom timezone offset in hours from UTC (-12 to +14)
   int8_t timezoneOffsetHours = 0;
 
+  // Automatically sync time via NTP on boot using saved WiFi credentials
+  uint8_t autoNtpSync = 0;
+
   ~CrossPointSettings() = default;
 
   // Get singleton instance

src/SettingsList.h

@@ -91,6 +91,8 @@ inline std::vector<SettingInfo> getSettingsList() {
                         {StrId::STR_TZ_UTC, StrId::STR_TZ_EASTERN, StrId::STR_TZ_CENTRAL, StrId::STR_TZ_MOUNTAIN,
                          StrId::STR_TZ_PACIFIC, StrId::STR_TZ_ALASKA, StrId::STR_TZ_HAWAII, StrId::STR_TZ_CUSTOM},
                         "timezone", StrId::STR_CAT_CLOCK),
+      SettingInfo::Toggle(StrId::STR_AUTO_NTP_SYNC, &CrossPointSettings::autoNtpSync, "autoNtpSync",
+                          StrId::STR_CAT_CLOCK),
 
       // --- Reader ---
       SettingInfo::DynamicEnum(

src/activities/network/CrossPointWebServerActivity.cpp

@@ -13,6 +13,7 @@
 #include "MappedInputManager.h"
 #include "NetworkModeSelectionActivity.h"
 #include "WifiSelectionActivity.h"
+#include "util/BootNtpSync.h"
 #include "activities/network/CalibreConnectActivity.h"
 #include "components/UITheme.h"
 #include "fontIds.h"
@@ -35,6 +36,8 @@ constexpr uint16_t DNS_PORT = 53;
 void CrossPointWebServerActivity::onEnter() {
   ActivityWithSubactivity::onEnter();
 
+  BootNtpSync::cancel();
+
   LOG_DBG("WEBACT", "Free heap at onEnter: %d bytes", ESP.getFreeHeap());
 
   // Reset state

src/activities/network/WifiSelectionActivity.cpp

@@ -12,11 +12,14 @@
 #include "activities/util/KeyboardEntryActivity.h"
 #include "components/UITheme.h"
 #include "fontIds.h"
+#include "util/BootNtpSync.h"
 #include "util/TimeSync.h"
 
 void WifiSelectionActivity::onEnter() {
   Activity::onEnter();
 
+  BootNtpSync::cancel();
+
   // Load saved WiFi credentials - SD card operations need lock as we use SPI
   // for both
   {

src/activities/reader/KOReaderSyncActivity.cpp

@@ -11,6 +11,7 @@
 #include "activities/network/WifiSelectionActivity.h"
 #include "components/UITheme.h"
 #include "fontIds.h"
+#include "util/BootNtpSync.h"
 #include "util/TimeSync.h"
 
 void KOReaderSyncActivity::onWifiSelectionComplete(const bool success) {
@@ -155,6 +156,8 @@ void KOReaderSyncActivity::performUpload() {
 void KOReaderSyncActivity::onEnter() {
   ActivityWithSubactivity::onEnter();
 
+  BootNtpSync::cancel();
+
   // Check for credentials first
   if (!KOREADER_STORE.hasCredentials()) {
     state = NO_CREDENTIALS;

src/activities/settings/KOReaderAuthActivity.cpp

@@ -8,6 +8,7 @@
 #include "KOReaderSyncClient.h"
 #include "MappedInputManager.h"
 #include "activities/network/WifiSelectionActivity.h"
+#include "util/BootNtpSync.h"
 #include "components/UITheme.h"
 #include "fontIds.h"
 
@@ -53,6 +54,8 @@ void KOReaderAuthActivity::performAuthentication() {
 void KOReaderAuthActivity::onEnter() {
   ActivityWithSubactivity::onEnter();
 
+  BootNtpSync::cancel();
+
   // Turn on WiFi
   WiFi.mode(WIFI_STA);
 

src/activities/settings/NtpSyncActivity.cpp

@@ -10,6 +10,7 @@
 #include "activities/network/WifiSelectionActivity.h"
 #include "components/UITheme.h"
 #include "fontIds.h"
+#include "util/BootNtpSync.h"
 #include "util/TimeSync.h"
 
 static constexpr unsigned long AUTO_DISMISS_MS = 5000;
@@ -52,6 +53,7 @@ void NtpSyncActivity::onWifiSelectionComplete(const bool success) {
 void NtpSyncActivity::onEnter() {
   ActivityWithSubactivity::onEnter();
 
+  BootNtpSync::cancel();
   LOG_DBG("NTP", "Turning on WiFi...");
   WiFi.mode(WIFI_STA);
 

src/activities/settings/OtaUpdateActivity.cpp

@@ -9,6 +9,7 @@
 #include "components/UITheme.h"
 #include "fontIds.h"
 #include "network/OtaUpdater.h"
+#include "util/BootNtpSync.h"
 
 void OtaUpdateActivity::onWifiSelectionComplete(const bool success) {
   exitActivity();
@@ -58,6 +59,8 @@ void OtaUpdateActivity::onWifiSelectionComplete(const bool success) {
 void OtaUpdateActivity::onEnter() {
   ActivityWithSubactivity::onEnter();
 
+  BootNtpSync::cancel();
+
   // Turn on WiFi immediately
   LOG_DBG("OTA", "Turning on WiFi...");
   WiFi.mode(WIFI_STA);

src/main.cpp

@@ -32,6 +32,7 @@
 #include "activities/util/FullScreenMessageActivity.h"
 #include "components/UITheme.h"
 #include "fontIds.h"
+#include "util/BootNtpSync.h"
 #include "util/ButtonNavigator.h"
 
 HalDisplay display;
@@ -342,6 +343,7 @@ void setup() {
 
   I18N.loadSettings();
   KOREADER_STORE.loadFromFile();
+  BootNtpSync::start();
   UITheme::getInstance().reload();
   ButtonNavigator::setMappedInputManager(mappedInputManager);
 
@@ -459,15 +461,24 @@ void loop() {
   // Refresh screen when the displayed minute changes (clock in header)
   if (SETTINGS.clockFormat != CrossPointSettings::CLOCK_OFF && currentActivity) {
     static int lastRenderedMinute = -1;
+    static bool sawInvalidTime = false;
     time_t now = time(nullptr);
     struct tm* t = localtime(&now);
     if (t != nullptr && t->tm_year > 100) {
       const int currentMinute = t->tm_hour * 60 + t->tm_min;
-      if (lastRenderedMinute >= 0 && currentMinute != lastRenderedMinute) {
+      if (lastRenderedMinute < 0) {
+        lastRenderedMinute = currentMinute;
+        if (sawInvalidTime) {
+          // Time just became valid (e.g. background NTP sync completed)
           currentActivity->requestUpdate();
         }
+      } else if (currentMinute != lastRenderedMinute) {
+        currentActivity->requestUpdate();
         lastRenderedMinute = currentMinute;
       }
+    } else {
+      sawInvalidTime = true;
+    }
   }
 
   const unsigned long activityStartTime = millis();

src/util/BootNtpSync.cpp

@@ -0,0 +1,163 @@
+#include "BootNtpSync.h"
+
+#include <Logging.h>
+#include <WiFi.h>
+#include <freertos/FreeRTOS.h>
+#include <freertos/task.h>
+
+#include <string>
+#include <vector>
+
+#include "CrossPointSettings.h"
+#include "WifiCredentialStore.h"
+#include "util/TimeSync.h"
+
+namespace BootNtpSync {
+
+static volatile bool running = false;
+static TaskHandle_t taskHandle = nullptr;
+
+struct TaskParams {
+  std::vector<WifiCredential> credentials;
+  std::string lastConnectedSsid;
+};
+
+static bool tryConnectToSavedNetwork(const TaskParams& params) {
+  WiFi.mode(WIFI_STA);
+  WiFi.disconnect();
+  vTaskDelay(100 / portTICK_PERIOD_MS);
+
+  LOG_DBG("BNTP", "Scanning WiFi networks...");
+  int16_t count = WiFi.scanNetworks();
+  if (count <= 0) {
+    LOG_DBG("BNTP", "Scan returned %d networks", count);
+    WiFi.scanDelete();
+    return false;
+  }
+
+  LOG_DBG("BNTP", "Found %d networks, matching against %zu saved credentials", count, params.credentials.size());
+
+  // Find best match: prefer lastConnectedSsid, otherwise first saved match
+  const WifiCredential* bestMatch = nullptr;
+  for (int i = 0; i < count; i++) {
+    std::string ssid = WiFi.SSID(i).c_str();
+    for (const auto& cred : params.credentials) {
+      if (cred.ssid == ssid) {
+        if (!bestMatch || cred.ssid == params.lastConnectedSsid) {
+          bestMatch = &cred;
+        }
+        if (cred.ssid == params.lastConnectedSsid) {
+          break;  // Can't do better than lastConnected
+        }
+      }
+    }
+    if (bestMatch && bestMatch->ssid == params.lastConnectedSsid) {
+      break;
+    }
+  }
+
+  WiFi.scanDelete();
+
+  if (!bestMatch) {
+    LOG_DBG("BNTP", "No saved network found in scan results");
+    return false;
+  }
+
+  LOG_DBG("BNTP", "Connecting to %s", bestMatch->ssid.c_str());
+  if (!bestMatch->password.empty()) {
+    WiFi.begin(bestMatch->ssid.c_str(), bestMatch->password.c_str());
+  } else {
+    WiFi.begin(bestMatch->ssid.c_str());
+  }
+
+  const unsigned long start = millis();
+  constexpr unsigned long CONNECT_TIMEOUT_MS = 10000;
+  while (WiFi.status() != WL_CONNECTED && millis() - start < CONNECT_TIMEOUT_MS) {
+    if (!running) return false;
+    vTaskDelay(100 / portTICK_PERIOD_MS);
+
+    wl_status_t status = WiFi.status();
+    if (status == WL_CONNECT_FAILED || status == WL_NO_SSID_AVAIL) {
+      LOG_DBG("BNTP", "Connection failed (status=%d)", status);
+      return false;
+    }
+  }
+
+  if (WiFi.status() == WL_CONNECTED) {
+    LOG_DBG("BNTP", "Connected to %s", bestMatch->ssid.c_str());
+    return true;
+  }
+
+  LOG_DBG("BNTP", "Connection timed out");
+  return false;
+}
+
+static void taskFunc(void* param) {
+  auto* params = static_cast<TaskParams*>(param);
+
+  bool connected = tryConnectToSavedNetwork(*params);
+
+  if (!connected && running) {
+    LOG_DBG("BNTP", "First scan failed, retrying in 3s...");
+    vTaskDelay(3000 / portTICK_PERIOD_MS);
+    if (running) {
+      connected = tryConnectToSavedNetwork(*params);
+    }
+  }
+
+  if (connected && running) {
+    LOG_DBG("BNTP", "Starting NTP sync...");
+    bool synced = TimeSync::waitForNtpSync(5000);
+    TimeSync::stopNtpSync();
+    if (synced) {
+      LOG_DBG("BNTP", "NTP sync successful");
+    } else {
+      LOG_DBG("BNTP", "NTP sync timed out, continuing without time");
+    }
+  }
+
+  WiFi.disconnect(false);
+  vTaskDelay(100 / portTICK_PERIOD_MS);
+  WiFi.mode(WIFI_OFF);
+  vTaskDelay(100 / portTICK_PERIOD_MS);
+
+  delete params;
+  running = false;
+  taskHandle = nullptr;
+  LOG_DBG("BNTP", "Boot NTP task complete");
+  vTaskDelete(nullptr);
+}
+
+void start() {
+  if (!SETTINGS.autoNtpSync) {
+    return;
+  }
+
+  WIFI_STORE.loadFromFile();
+  const auto& creds = WIFI_STORE.getCredentials();
+  if (creds.empty()) {
+    LOG_DBG("BNTP", "No saved WiFi credentials, skipping boot NTP sync");
+    return;
+  }
+
+  auto* params = new TaskParams{creds, WIFI_STORE.getLastConnectedSsid()};
+
+  running = true;
+  xTaskCreate(taskFunc, "BootNTP", 4096, params, 1, &taskHandle);
+  LOG_DBG("BNTP", "Boot NTP sync task started");
+}
+
+void cancel() {
+  if (!running) return;
+  LOG_DBG("BNTP", "Cancelling boot NTP sync...");
+  running = false;
+  // Wait for the task to notice and clean up (up to 2s)
+  for (int i = 0; i < 20 && taskHandle != nullptr; i++) {
+    delay(100);
+  }
+  LOG_DBG("BNTP", "Boot NTP sync cancelled");
+}
+
+bool isRunning() { return running; }
+
+}  // namespace BootNtpSync

src/util/BootNtpSync.h

@@ -0,0 +1,16 @@
+#pragma once
+
+namespace BootNtpSync {
+
+// Spawn a background FreeRTOS task that scans for saved WiFi networks,
+// connects, syncs NTP, then tears down WiFi. Non-blocking; does nothing
+// if autoNtpSync is disabled or no credentials are stored.
+void start();
+
+// Signal the background task to abort and wait for it to finish.
+// Call before starting any other WiFi operation.
+void cancel();
+
+bool isRunning();
+
+}  // namespace BootNtpSync