diff --git a/app/src/main/java/nodomain/freeyourgadget/gadgetbridge/activities/debug/HealthConnectDebugFragment.kt b/app/src/main/java/nodomain/freeyourgadget/gadgetbridge/activities/debug/HealthConnectDebugFragment.kt
index 2a5cf9b2ca..df8695b437 100644
--- a/app/src/main/java/nodomain/freeyourgadget/gadgetbridge/activities/debug/HealthConnectDebugFragment.kt
+++ b/app/src/main/java/nodomain/freeyourgadget/gadgetbridge/activities/debug/HealthConnectDebugFragment.kt
@@ -15,12 +15,15 @@ import nodomain.freeyourgadget.gadgetbridge.database.DBHelper
 import nodomain.freeyourgadget.gadgetbridge.entities.HealthConnectSyncStateDao
 import nodomain.freeyourgadget.gadgetbridge.util.DateTimeUtils
 import nodomain.freeyourgadget.gadgetbridge.util.GB
+import nodomain.freeyourgadget.gadgetbridge.util.healthconnect.GadgetbridgeDataExporter
 import nodomain.freeyourgadget.gadgetbridge.util.healthconnect.HealthConnectSyncWorker
 import org.slf4j.Logger
 import org.slf4j.LoggerFactory
 import java.time.Instant
+import java.time.LocalDate
 import java.time.ZoneId
 import java.time.format.DateTimeFormatter
+import java.util.Calendar
 
 class HealthConnectDebugFragment : AbstractDebugFragment() {
     override fun onCreatePreferences(savedInstanceState: Bundle?, rootKey: String?) {
@@ -61,6 +64,30 @@ class HealthConnectDebugFragment : AbstractDebugFragment() {
                 .show()
         }
 
+        onClick(PREF_DEBUG_EXPORT_GB_DATA) {
+            runOnDebugDevices("Export data for device", forceDialog = true) { gbDevice ->
+                val cal = Calendar.getInstance()
+                cal.add(Calendar.DAY_OF_YEAR, -7)
+                DatePickerDialog(
+                    requireActivity(),
+                    { _: DatePicker?, year: Int, month: Int, day: Int ->
+                        val startDate = LocalDate.of(year, month + 1, day)
+                        val startInstant = startDate.atStartOfDay(ZoneId.systemDefault()).toInstant()
+                        val endInstant = Instant.now()
+                        try {
+                            val file = GadgetbridgeDataExporter.export(requireContext(), gbDevice, startInstant, endInstant)
+                            GB.toast("Exported to ${file.name}", Toast.LENGTH_LONG, GB.INFO)
+                        } catch (e: Exception) {
+                            GB.toast("Export failed: ${e.message}", Toast.LENGTH_LONG, GB.ERROR, e)
+                        }
+                    },
+                    cal.get(Calendar.YEAR),
+                    cal.get(Calendar.MONTH),
+                    cal.get(Calendar.DAY_OF_MONTH)
+                ).show()
+            }
+        }
+
         reloadSyncStates()
     }
 
@@ -126,5 +153,6 @@ class HealthConnectDebugFragment : AbstractDebugFragment() {
         private val LOG: Logger = LoggerFactory.getLogger(HealthConnectDebugFragment::class.java)
         private const val PREF_DEBUG_MANUAL_SYNC_TRIGGER = "pref_debug_manual_sync_trigger"
         private const val PREF_DEBUG_RESET_HC_SYNC_STATE = "pref_debug_reset_hc_sync_state"
+        private const val PREF_DEBUG_EXPORT_GB_DATA = "pref_debug_export_gb_data"
     }
 }
diff --git a/app/src/main/java/nodomain/freeyourgadget/gadgetbridge/util/healthconnect/GadgetbridgeDataExporter.kt b/app/src/main/java/nodomain/freeyourgadget/gadgetbridge/util/healthconnect/GadgetbridgeDataExporter.kt
new file mode 100644
index 0000000000..4ee6bd1682
--- /dev/null
+++ b/app/src/main/java/nodomain/freeyourgadget/gadgetbridge/util/healthconnect/GadgetbridgeDataExporter.kt
@@ -0,0 +1,220 @@
+package nodomain.freeyourgadget.gadgetbridge.util.healthconnect
+
+import android.content.Context
+import nodomain.freeyourgadget.gadgetbridge.GBApplication
+import nodomain.freeyourgadget.gadgetbridge.database.DBHandler
+import nodomain.freeyourgadget.gadgetbridge.database.DBHelper
+import nodomain.freeyourgadget.gadgetbridge.devices.TimeSampleProvider
+import nodomain.freeyourgadget.gadgetbridge.entities.BaseActivitySummaryDao
+import nodomain.freeyourgadget.gadgetbridge.impl.GBDevice
+import nodomain.freeyourgadget.gadgetbridge.model.*
+import nodomain.freeyourgadget.gadgetbridge.util.FileUtils
+import org.json.JSONArray
+import org.json.JSONObject
+import org.slf4j.LoggerFactory
+import java.io.File
+import java.time.Instant
+import java.time.ZoneId
+import java.time.ZonedDateTime
+import java.time.format.DateTimeFormatter
+
+object GadgetbridgeDataExporter {
+    private val LOG = LoggerFactory.getLogger(GadgetbridgeDataExporter::class.java)
+    private const val TAG = "[HC_SYNC]"
+
+    fun export(context: Context, gbDevice: GBDevice, startInstant: Instant, endInstant: Instant): File {
+        LOG.info("$TAG Export starting for device '{}', range {} to {}", gbDevice.aliasOrName, startInstant, endInstant)
+
+        val result = JSONObject()
+        result.put("export_time", Instant.now().toString())
+        result.put("source", "gadgetbridge")
+        result.put("device", JSONObject().apply {
+            put("name", gbDevice.aliasOrName)
+            put("address", gbDevice.address)
+            put("model", gbDevice.model ?: "")
+        })
+        result.put("time_range", JSONObject().apply {
+            put("start", startInstant.toString())
+            put("end", endInstant.toString())
+        })
+
+        val data = JSONObject()
+
+        val coordinator = gbDevice.deviceCoordinator
+
+        GBApplication.acquireDbReadOnly().use { db ->
+            val tsFrom = startInstant.epochSecond.toInt()
+            val tsTo = endInstant.epochSecond.toInt()
+            val msFrom = startInstant.toEpochMilli()
+            val msTo = endInstant.toEpochMilli()
+
+            val activitySamples = try {
+                val provider = coordinator.getSampleProvider(gbDevice, db.daoSession)
+                provider?.getAllActivitySamples(tsFrom, tsTo) ?: emptyList()
+            } catch (e: Exception) {
+                LOG.error("$TAG Failed to get activity samples", e)
+                emptyList()
+            }
+
+            data.put("steps", exportSteps(activitySamples))
+            data.put("heart_rate", exportHeartRate(activitySamples))
+            data.put("sleep", exportSleep(activitySamples))
+            data.put("spo2", exportTimeSamples(coordinator.getSpo2SampleProvider(gbDevice, db.daoSession), msFrom, msTo) { sample ->
+                val spo2 = (sample as? Spo2Sample)?.spo2 ?: return@exportTimeSamples null
+                if (spo2 <= 0 || spo2 > 100) return@exportTimeSamples null
+                JSONObject().apply {
+                    put("time", Instant.ofEpochMilli(sample.timestamp).toString())
+                    put("percentage", spo2.toDouble())
+                }
+            })
+            data.put("hrv", exportTimeSamples(coordinator.getHrvValueSampleProvider(gbDevice, db.daoSession), msFrom, msTo) { sample ->
+                val hrv = (sample as? HrvValueSample)?.value ?: return@exportTimeSamples null
+                if (hrv <= 0) return@exportTimeSamples null
+                JSONObject().apply {
+                    put("time", Instant.ofEpochMilli(sample.timestamp).toString())
+                    put("rmssd_ms", hrv.toDouble())
+                }
+            })
+            data.put("respiratory_rate", exportTimeSamples(coordinator.getRespiratoryRateSampleProvider(gbDevice, db.daoSession), msFrom, msTo) { sample ->
+                val rate = (sample as? RespiratoryRateSample)?.respiratoryRate ?: return@exportTimeSamples null
+                if (rate <= 0) return@exportTimeSamples null
+                JSONObject().apply {
+                    put("time", Instant.ofEpochMilli(sample.timestamp).toString())
+                    put("rate", rate.toDouble())
+                }
+            })
+            data.put("resting_heart_rate", exportTimeSamples(coordinator.getHeartRateRestingSampleProvider(gbDevice, db.daoSession), msFrom, msTo) { sample ->
+                val bpm = (sample as? HeartRateSample)?.heartRate ?: return@exportTimeSamples null
+                if (bpm <= 0) return@exportTimeSamples null
+                JSONObject().apply {
+                    put("time", Instant.ofEpochMilli(sample.timestamp).toString())
+                    put("bpm", bpm)
+                }
+            })
+            data.put("temperature", exportTimeSamples(coordinator.getTemperatureSampleProvider(gbDevice, db.daoSession), msFrom, msTo) { sample ->
+                val temp = (sample as? TemperatureSample) ?: return@exportTimeSamples null
+                JSONObject().apply {
+                    put("time", Instant.ofEpochMilli(sample.timestamp).toString())
+                    put("celsius", temp.temperature.toDouble())
+                    put("type", temp.temperatureType)
+                }
+            })
+            data.put("exercise_sessions", exportWorkouts(db, gbDevice, msFrom, msTo))
+        }
+
+        result.put("data", data)
+
+        val dateFormatter = DateTimeFormatter.ofPattern("yyyyMMdd_HHmmss")
+        val timestamp = ZonedDateTime.now().format(dateFormatter)
+        val fileName = "gb_export_${gbDevice.aliasOrName.replace(" ", "_")}_$timestamp.json"
+        val dir = FileUtils.getExternalFilesDir()
+        val outFile = File(dir, fileName)
+        outFile.writeText(result.toString(2))
+
+        LOG.info("$TAG Export complete: {}", outFile.absolutePath)
+        return outFile
+    }
+
+    private fun exportSteps(samples: List<ActivitySample>): JSONArray {
+        val arr = JSONArray()
+        for (s in samples) {
+            if (s.steps <= 0) continue
+            arr.put(JSONObject().apply {
+                put("time", Instant.ofEpochSecond(s.timestamp.toLong()).toString())
+                put("steps", s.steps)
+            })
+        }
+        return arr
+    }
+
+    private fun exportHeartRate(samples: List<ActivitySample>): JSONArray {
+        val arr = JSONArray()
+        for (s in samples) {
+            val hr = s.heartRate
+            if (hr <= 0 || hr >= 255) continue
+            arr.put(JSONObject().apply {
+                put("time", Instant.ofEpochSecond(s.timestamp.toLong()).toString())
+                put("bpm", hr)
+            })
+        }
+        return arr
+    }
+
+    private fun exportSleep(samples: List<ActivitySample>): JSONArray {
+        val sleepSamples = samples.filter { isSleep(it) }
+        val arr = JSONArray()
+        for (s in sleepSamples) {
+            arr.put(JSONObject().apply {
+                put("time", Instant.ofEpochSecond(s.timestamp.toLong()).toString())
+                put("stage", mapSleepStage(s.kind))
+            })
+        }
+        return arr
+    }
+
+    private fun isSleep(sample: ActivitySample): Boolean {
+        return sample.kind == ActivityKind.DEEP_SLEEP ||
+                sample.kind == ActivityKind.LIGHT_SLEEP ||
+                sample.kind == ActivityKind.REM_SLEEP ||
+                sample.kind == ActivityKind.AWAKE_SLEEP
+    }
+
+    private fun mapSleepStage(kind: ActivityKind): String {
+        return when (kind) {
+            ActivityKind.LIGHT_SLEEP -> "light"
+            ActivityKind.DEEP_SLEEP -> "deep"
+            ActivityKind.REM_SLEEP -> "rem"
+            ActivityKind.AWAKE_SLEEP -> "awake"
+            else -> "unknown"
+        }
+    }
+
+    private fun <T : TimeSample> exportTimeSamples(
+        provider: TimeSampleProvider<out T>?,
+        msFrom: Long,
+        msTo: Long,
+        converter: (T) -> JSONObject?
+    ): JSONArray {
+        val arr = JSONArray()
+        if (provider == null) return arr
+        try {
+            @Suppress("UNCHECKED_CAST")
+            val samples = provider.getAllSamples(msFrom, msTo) as List<T>
+            for (s in samples) {
+                val json = converter(s)
+                if (json != null) arr.put(json)
+            }
+        } catch (e: Exception) {
+            LOG.error("$TAG Failed to export time samples", e)
+        }
+        return arr
+    }
+
+    private fun exportWorkouts(db: DBHandler, gbDevice: GBDevice, msFrom: Long, msTo: Long): JSONArray {
+        val arr = JSONArray()
+        try {
+            val deviceEntity = DBHelper.getDevice(gbDevice, db.daoSession) ?: return arr
+            val summaries = db.daoSession.baseActivitySummaryDao.queryBuilder()
+                .where(
+                    BaseActivitySummaryDao.Properties.DeviceId.eq(deviceEntity.id),
+                    BaseActivitySummaryDao.Properties.StartTime.ge(java.util.Date(msFrom)),
+                    BaseActivitySummaryDao.Properties.StartTime.lt(java.util.Date(msTo))
+                )
+                .orderAsc(BaseActivitySummaryDao.Properties.StartTime)
+                .list()
+
+            for (s in summaries) {
+                arr.put(JSONObject().apply {
+                    put("start", s.startTime.toInstant().toString())
+                    put("end", s.endTime.toInstant().toString())
+                    put("activity_kind", s.activityKind)
+                    put("name", s.name ?: "")
+                })
+            }
+        } catch (e: Exception) {
+            LOG.error("$TAG Failed to export workouts", e)
+        }
+        return arr
+    }
+}
+
diff --git a/app/src/main/res/xml/debug_preferences_health_connect.xml b/app/src/main/res/xml/debug_preferences_health_connect.xml
index 803a645b2f..ba7918beb1 100644
--- a/app/src/main/res/xml/debug_preferences_health_connect.xml
+++ b/app/src/main/res/xml/debug_preferences_health_connect.xml
@@ -16,4 +16,11 @@
         android:summary="Reset Health Connect sync state and allow re-syncing all data"
         android:title="Reset HC sync state" />
 
+    <Preference
+        android:icon="@drawable/ic_save"
+        android:key="pref_debug_export_gb_data"
+        android:persistent="false"
+        android:summary="Export device data as JSON (for HC sync verification)"
+        android:title="Export GB data as JSON" />
+
 </androidx.preference.PreferenceScreen>