diff --git a/app/src/main/java/nodomain/freeyourgadget/gadgetbridge/util/healthconnect/syncers/AbstractTimeSampleSyncer.kt b/app/src/main/java/nodomain/freeyourgadget/gadgetbridge/util/healthconnect/syncers/AbstractTimeSampleSyncer.kt
index 493825ca30..cef7e0c3b9 100644
--- a/app/src/main/java/nodomain/freeyourgadget/gadgetbridge/util/healthconnect/syncers/AbstractTimeSampleSyncer.kt
+++ b/app/src/main/java/nodomain/freeyourgadget/gadgetbridge/util/healthconnect/syncers/AbstractTimeSampleSyncer.kt
@@ -102,7 +102,8 @@ internal abstract class AbstractTimeSampleSyncer<TSample : TimeSample, TRecord :
 
         val recordsToInsert = samples.filter {
             val timestamp = Instant.ofEpochMilli(it.timestamp)
-            if (timestamp.isBefore(sliceStartBoundary) || !timestamp.isBefore(sliceEndBoundary)) {
+            // Use inclusive boundaries [sliceStart, sliceEnd] to ensure last sample is included
+            if (timestamp.isBefore(sliceStartBoundary) || timestamp.isAfter(sliceEndBoundary)) {
                 logger.debug(
                     "Skipping sample for at {} as it's outside the slice {} - {}.",
                     timestamp,
diff --git a/app/src/main/java/nodomain/freeyourgadget/gadgetbridge/util/healthconnect/syncers/HeartRateSync.kt b/app/src/main/java/nodomain/freeyourgadget/gadgetbridge/util/healthconnect/syncers/HeartRateSync.kt
index ac79c54d3f..3450a068ed 100644
--- a/app/src/main/java/nodomain/freeyourgadget/gadgetbridge/util/healthconnect/syncers/HeartRateSync.kt
+++ b/app/src/main/java/nodomain/freeyourgadget/gadgetbridge/util/healthconnect/syncers/HeartRateSync.kt
@@ -77,8 +77,8 @@ internal object HeartRateSyncer : ActivitySampleSyncer {
         for (gbSample in validHRSamples) {
             val currentSampleTimestamp = Instant.ofEpochSecond(gbSample.timestamp.toLong())
 
-            // Ensure sample is strictly within the slice [sliceStartBoundary, sliceEndBoundary)
-            if (currentSampleTimestamp.isBefore(sliceStartBoundary) || !currentSampleTimestamp.isBefore(sliceEndBoundary)) {
+            // Use inclusive boundaries [sliceStart, sliceEnd] for the slice
+            if (currentSampleTimestamp.isBefore(sliceStartBoundary) || currentSampleTimestamp.isAfter(sliceEndBoundary)) {
                 skippedCount++
                 continue
             }
diff --git a/app/src/main/java/nodomain/freeyourgadget/gadgetbridge/util/healthconnect/syncers/SleepSyncer.kt b/app/src/main/java/nodomain/freeyourgadget/gadgetbridge/util/healthconnect/syncers/SleepSyncer.kt
index f62c07dedf..83e1c1d6ba 100644
--- a/app/src/main/java/nodomain/freeyourgadget/gadgetbridge/util/healthconnect/syncers/SleepSyncer.kt
+++ b/app/src/main/java/nodomain/freeyourgadget/gadgetbridge/util/healthconnect/syncers/SleepSyncer.kt
@@ -122,8 +122,9 @@ internal object SleepSyncer : ContextualActivitySampleSyncer {
         val sessionBoundaryStart = analysisSession.sleepStart.toInstant()
         val sessionBoundaryEndInclusive = analysisSession.sleepEnd.toInstant()
 
-        // Check if session overlaps with the current slice
-        if (!sessionBoundaryStart.isBefore(sliceEndBoundary) || !sessionBoundaryEndInclusive.isAfter(sliceStartBoundary)) {
+        // Check if session overlaps with the current slice (inclusive boundaries [sliceStart, sliceEnd])
+        // Skip if: sessionStart > sliceEnd OR sessionEnd < sliceStart
+        if (sessionBoundaryStart.isAfter(sliceEndBoundary) || sessionBoundaryEndInclusive.isBefore(sliceStartBoundary)) {
             LOG.debug(
                 "Skipping sleep session (identified by SleepAnalysis) for device '{}' (Timeframe: {} to {}) as it does not overlap with current slice ({} to {}).",
                 deviceName,
diff --git a/app/src/main/java/nodomain/freeyourgadget/gadgetbridge/util/healthconnect/syncers/StepsSync.kt b/app/src/main/java/nodomain/freeyourgadget/gadgetbridge/util/healthconnect/syncers/StepsSync.kt
index 44ce1c12a3..7970b6ee09 100644
--- a/app/src/main/java/nodomain/freeyourgadget/gadgetbridge/util/healthconnect/syncers/StepsSync.kt
+++ b/app/src/main/java/nodomain/freeyourgadget/gadgetbridge/util/healthconnect/syncers/StepsSync.kt
@@ -69,8 +69,9 @@ internal object StepsSyncer : ActivitySampleSyncer {
                 val endTs = Instant.ofEpochSecond(currentSample.timestamp.toLong())
                 val startTs = endTs.minus(1, ChronoUnit.MINUTES)
 
-                // Ensure the record's interval [startTs, endTs) overlaps with the slice [sliceStartBoundary, sliceEndBoundary)
-                if (endTs.isAfter(sliceStartBoundary) && startTs.isBefore(sliceEndBoundary)) {
+                // Use inclusive boundaries [sliceStart, sliceEnd] for the slice
+                // Overlap check: interval overlaps if endTs > sliceStart AND startTs <= sliceEnd
+                if (endTs.isAfter(sliceStartBoundary) && !startTs.isAfter(sliceEndBoundary)) {
                     stepsRecordList.add(StepsRecord(startTs, offset, endTs, offset, stepsInMinute, metadata))
                 } else {
                     skippedCount++