diff --git a/backend/UniVerse.Application/DTOs/Sync/SyncDtos.cs b/backend/UniVerse.Application/DTOs/Sync/SyncDtos.cs
index d1a738e..b8dd58a 100644
--- a/backend/UniVerse.Application/DTOs/Sync/SyncDtos.cs
+++ b/backend/UniVerse.Application/DTOs/Sync/SyncDtos.cs
@@ -7,7 +7,13 @@ public record SyncScheduleRequest(
     IReadOnlyList<string>? TypeId
 );
 
-public record SyncResultDto(int Created, int Updated, int Skipped, string? Error);
+public record SyncResultDto(
+    int Created,
+    int Updated,
+    int Skipped,
+    string? Error,
+    IReadOnlyList<string>? Details = null
+);
 
 public record SyncStatusDto(DateTime? LastSyncAt, string Status, SyncResultDto? LastResult);
 
diff --git a/backend/UniVerse.Infrastructure/ExternalServices/ModeusApiClient.cs b/backend/UniVerse.Infrastructure/ExternalServices/ModeusApiClient.cs
index 3a739f3..07e5031 100644
--- a/backend/UniVerse.Infrastructure/ExternalServices/ModeusApiClient.cs
+++ b/backend/UniVerse.Infrastructure/ExternalServices/ModeusApiClient.cs
@@ -23,7 +23,8 @@ public class ModeusApiClient : IModeusApiClient
     {
         var body = new { specialtyCode = request.SpecialtyCode, timeMin = request.TimeMin, timeMax = request.TimeMax, typeId = request.TypeId };
         var response = await _http.PostAsJsonAsync("/api/proxy/events/search", body);
-        response.EnsureSuccessStatusCode();
+        await EnsureSuccessAsync(response, "Modeus events search",
+            $"specialtyCode={request.SpecialtyCode ?? "<empty>"}, timeMin={request.TimeMin:O}, timeMax={request.TimeMax:O}, typeId=[{string.Join(", ", request.TypeId ?? [])}]");
         return await response.Content.ReadFromJsonAsync<ModeusEventsResponse>() ?? new(new());
     }
 
@@ -46,7 +47,8 @@ public class ModeusApiClient : IModeusApiClient
             };
 
             var response = await _http.PostAsJsonAsync("/api/proxy/rooms/search", body);
-            response.EnsureSuccessStatusCode();
+            await EnsureSuccessAsync(response, "Modeus rooms search",
+                $"name=<empty>, sort=+building.name,+name, size={pageSize}, page={page}, deleted=false");
 
             var payload = await response.Content.ReadFromJsonAsync<ModeusRoomsResponse>() ?? new ModeusRoomsResponse();
             allRooms.AddRange(payload.RoomItems);
@@ -59,6 +61,20 @@ public class ModeusApiClient : IModeusApiClient
         return new ModeusRoomsResponse { Rooms = allRooms };
     }
 
+    private static async Task EnsureSuccessAsync(HttpResponseMessage response, string operation, string requestSummary)
+    {
+        if (response.IsSuccessStatusCode) return;
+
+        var responseBody = await response.Content.ReadAsStringAsync();
+        if (responseBody.Length > 2000)
+            responseBody = string.Concat(responseBody.AsSpan(0, 2000), "...<truncated>");
+
+        throw new HttpRequestException(
+            $"{operation} failed with HTTP {(int)response.StatusCode} {response.ReasonPhrase}. Request: {requestSummary}. Response body: {responseBody}",
+            null,
+            response.StatusCode);
+    }
+
     public async Task<List<ModeusEmployee>> SearchEmployeeAsync(string fullname)
     {
         var response = await _http.GetFromJsonAsync<List<ModeusEmployee>>(
diff --git a/backend/UniVerse.Infrastructure/Services/ScheduleSyncService.cs b/backend/UniVerse.Infrastructure/Services/ScheduleSyncService.cs
index ee113e5..35c3aad 100644
--- a/backend/UniVerse.Infrastructure/Services/ScheduleSyncService.cs
+++ b/backend/UniVerse.Infrastructure/Services/ScheduleSyncService.cs
@@ -21,6 +21,7 @@ public class ScheduleSyncService : IScheduleSyncService
 
     public async Task<SyncResultDto> SyncScheduleAsync(SyncScheduleRequest request)
     {
+        const string stage = "schedule";
         int created = 0, updated = 0, skipped = 0;
         try
         {
@@ -45,7 +46,18 @@ public class ScheduleSyncService : IScheduleSyncService
         catch (Exception ex)
         {
             _logger.LogError(ex, "Schedule sync failed");
-            var result = new SyncResultDto(created, updated, skipped, ex.Message);
+            var result = new SyncResultDto(created, updated, skipped, ex.Message, BuildErrorDetails(
+                ex,
+                stage,
+                created,
+                updated,
+                skipped,
+                [
+                    $"specialtyCode={request.SpecialtyCode ?? "<empty>"}",
+                    $"timeMin={request.TimeMin:O}",
+                    $"timeMax={request.TimeMax:O}",
+                    $"typeId=[{string.Join(", ", request.TypeId ?? [])}]"
+                ]));
             _lastStatus = new SyncStatusDto(DateTime.UtcNow, "failed", result);
             return result;
         }
@@ -53,6 +65,7 @@ public class ScheduleSyncService : IScheduleSyncService
 
     public async Task<SyncResultDto> SyncRoomsAsync()
     {
+        const string stage = "rooms";
         int created = 0, updated = 0, skipped = 0;
         try
         {
@@ -96,7 +109,13 @@ public class ScheduleSyncService : IScheduleSyncService
         catch (Exception ex)
         {
             _logger.LogError(ex, "Rooms sync failed");
-            var result = new SyncResultDto(created, updated, skipped, ex.Message);
+            var result = new SyncResultDto(created, updated, skipped, ex.Message, BuildErrorDetails(
+                ex,
+                stage,
+                created,
+                updated,
+                skipped,
+                ["request=name:<empty>, sort:+building.name,+name, deleted:false, page size:100"]));
             _lastStatus = new SyncStatusDto(DateTime.UtcNow, "failed", result);
             return result;
         }
@@ -109,4 +128,30 @@ public class ScheduleSyncService : IScheduleSyncService
     }
 
     public Task<SyncStatusDto> GetLastSyncStatusAsync() => Task.FromResult(_lastStatus);
+
+    private static IReadOnlyList<string> BuildErrorDetails(
+        Exception exception,
+        string stage,
+        int created,
+        int updated,
+        int skipped,
+        IReadOnlyList<string> context)
+    {
+        var details = new List<string>
+        {
+            $"stage={stage}",
+            $"exceptionType={exception.GetType().FullName}",
+            $"message={exception.Message}",
+            $"partialResult=created:{created}, updated:{updated}, skipped:{skipped}"
+        };
+
+        if (exception is HttpRequestException httpException && httpException.StatusCode.HasValue)
+            details.Add($"httpStatus={(int)httpException.StatusCode.Value} {httpException.StatusCode.Value}");
+
+        if (exception.InnerException != null)
+            details.Add($"innerException={exception.InnerException.GetType().FullName}: {exception.InnerException.Message}");
+
+        details.AddRange(context);
+        return details;
+    }
 }
diff --git a/frontend/src/api/types.ts b/frontend/src/api/types.ts
index 16056c6..accd091 100644
--- a/frontend/src/api/types.ts
+++ b/frontend/src/api/types.ts
@@ -166,6 +166,7 @@ export interface SyncResultDto {
   updated: number
   skipped: number
   error?: string | null
+  details?: string[] | null
 }
 
 export interface UserAchievementDto {
diff --git a/frontend/src/views/admin/AdminLecturesView.vue b/frontend/src/views/admin/AdminLecturesView.vue
index e584675..1aa281f 100644
--- a/frontend/src/views/admin/AdminLecturesView.vue
+++ b/frontend/src/views/admin/AdminLecturesView.vue
@@ -1,6 +1,7 @@
 <script setup lang="ts">
 import { computed, inject, onMounted, ref } from 'vue'
 import { coursesApi, lecturesApi, locationsApi, syncApi, tagsApi } from '@/api'
+import { ApiError } from '@/api/client'
 import type {
   ApiScheduleTypeId,
   CourseDto,
@@ -30,6 +31,7 @@ const loading = ref(false)
 const syncingSchedule = ref(false)
 const syncingRooms = ref(false)
 const syncError = ref('')
+const syncErrorDetails = ref<string[]>([])
 const syncStatus = ref<SyncStatusDto | null>(null)
 const syncResult = ref<SyncResultDto | null>(null)
 const addToast = inject('addToast') as ((message: string, type?: 'success' | 'error' | 'info') => void) | undefined
@@ -66,6 +68,10 @@ const syncMeta = computed(() => {
 })
 
 const visibleSyncResult = computed(() => syncResult.value ?? syncStatus.value?.lastResult ?? null)
+const visibleSyncDetails = computed(() => {
+  if (syncErrorDetails.value.length) return syncErrorDetails.value
+  return visibleSyncResult.value?.details ?? []
+})
 
 const tabConfig: Record<TabKey, TabConfig> = {
   lectures: {
@@ -182,6 +188,7 @@ async function refreshSyncStatus() {
 async function runScheduleSync() {
   syncingSchedule.value = true
   syncError.value = ''
+  syncErrorDetails.value = []
   syncResult.value = null
   try {
     syncResult.value = await syncApi.schedule({
@@ -193,6 +200,7 @@ async function runScheduleSync() {
 
     if (syncResult.value.error) {
       syncError.value = syncResult.value.error
+      syncErrorDetails.value = syncResult.value.details ?? []
       addToast?.('Синхронизация завершилась с ошибкой.', 'error')
     } else {
       addToast?.('Расписание синхронизировано.', 'success')
@@ -201,6 +209,7 @@ async function runScheduleSync() {
     await loadData()
   } catch (err) {
     syncError.value = err instanceof Error ? err.message : 'Не удалось синхронизировать расписание.'
+    syncErrorDetails.value = extractApiErrorDetails(err)
     addToast?.(syncError.value, 'error')
     await refreshSyncStatus()
   } finally {
@@ -211,19 +220,41 @@ async function runScheduleSync() {
 async function runRoomsSync() {
   syncingRooms.value = true
   syncError.value = ''
+  syncErrorDetails.value = []
   syncResult.value = null
   try {
     syncResult.value = await syncApi.rooms()
-    addToast?.('Аудитории синхронизированы.', 'success')
+    if (syncResult.value.error) {
+      syncError.value = syncResult.value.error
+      syncErrorDetails.value = syncResult.value.details ?? []
+      addToast?.('Синхронизация аудиторий завершилась с ошибкой.', 'error')
+    } else {
+      addToast?.('Аудитории синхронизированы.', 'success')
+    }
     await loadData()
   } catch (err) {
     syncError.value = err instanceof Error ? err.message : 'Не удалось синхронизировать аудитории.'
+    syncErrorDetails.value = extractApiErrorDetails(err)
     addToast?.(syncError.value, 'error')
   } finally {
     syncingRooms.value = false
   }
 }
 
+function extractApiErrorDetails(err: unknown) {
+  if (!(err instanceof ApiError)) return []
+  const details = err.details
+  if (!details || typeof details !== 'object') return []
+
+  const problem = details as { title?: unknown; detail?: unknown; traceId?: unknown; status?: unknown }
+  return [
+    typeof problem.title === 'string' ? `title=${problem.title}` : '',
+    typeof problem.status === 'number' ? `status=${problem.status}` : '',
+    typeof problem.detail === 'string' ? `detail=${problem.detail}` : '',
+    typeof problem.traceId === 'string' ? `traceId=${problem.traceId}` : '',
+  ].filter(Boolean)
+}
+
 onMounted(() => {
   void loadData()
 })
@@ -282,6 +313,12 @@ onMounted(() => {
           <div v-if="syncError || visibleSyncResult?.error" class="sync-error">
             {{ syncError || visibleSyncResult?.error }}
           </div>
+          <details v-if="visibleSyncDetails.length" class="sync-details">
+            <summary>Подробности ошибки</summary>
+            <ul>
+              <li v-for="detail in visibleSyncDetails" :key="detail">{{ detail }}</li>
+            </ul>
+          </details>
 
           <div class="form-actions">
             <button class="btn-primary" type="submit" :disabled="syncingSchedule">
@@ -326,6 +363,17 @@ onMounted(() => {
 .sync-meta { font-size: 12px; color: var(--color-text-secondary); margin-top: 4px; }
 .sync-result { font-size: 13px; color: var(--color-text-secondary); }
 .sync-error { font-size: 13px; color: var(--color-error); }
+.sync-details {
+  border: 1px solid rgba(239,68,68,0.24);
+  border-radius: var(--radius-sm);
+  padding: 8px 10px;
+  background: rgba(254,242,242,0.68);
+  color: var(--color-text-secondary);
+  font-size: 12px;
+}
+.sync-details summary { cursor: pointer; color: var(--color-error); font-weight: 600; }
+.sync-details ul { margin: 8px 0 0; padding-left: 18px; overflow-wrap: anywhere; }
+.sync-details li + li { margin-top: 4px; }
 .sync-status {
   flex: 0 0 auto;
   border: 1px solid var(--color-border-glass);