diff --git a/lib/providers/app_state_provider.dart b/lib/providers/app_state_provider.dart
index 059dda5..70ba024 100644
--- a/lib/providers/app_state_provider.dart
+++ b/lib/providers/app_state_provider.dart
@@ -5100,6 +5100,7 @@ class AppStateProvider extends ChangeNotifier with WidgetsBindingObserver {
 
     // Extract session_id into local variable — never stored in shared state
     final offlineSessionId = effectiveAuth!['session_id'] as String?;
+    final uploadPublicKey = publicKey!;
     if (offlineSessionId == null) {
       debugError('[OFFLINE] Auth succeeded but no session_id in response');
       return OfflineUploadResult.authFailed;
@@ -5179,6 +5180,12 @@ class AppStateProvider extends ChangeNotifier with WidgetsBindingObserver {
       if (result == UploadResult.success) {
         uploadedCount += batch.length;
         debugLog('[OFFLINE] Uploaded batch $batchNum: ${batch.length} pings');
+        _forwardOfflineBatchToCustomApi(
+          batch,
+          batchNum: batchNum,
+          publicKey: uploadPublicKey,
+          auth: effectiveAuth,
+        );
         continue;
       }
 
@@ -5234,6 +5241,36 @@ class AppStateProvider extends ChangeNotifier with WidgetsBindingObserver {
     }
   }
 
+  /// Forward a successfully uploaded offline batch to the Custom API endpoint.
+  ///
+  /// The whole batch is stamped with the upload-location zone (the fresh
+  /// /auth at the current GPS position), not where the pings were recorded —
+  /// the client cannot compute per-ping zones for sessions that span regions.
+  void _forwardOfflineBatchToCustomApi(
+    List<Map<String, dynamic>> batch, {
+    required int batchNum,
+    required String publicKey,
+    required Map<String, dynamic> auth,
+  }) {
+    final contact = publicKey.length >= 8
+        ? publicKey.substring(0, 8).toUpperCase()
+        : null;
+    var iata = zoneCode ?? _preferences.iataCode;
+    final zone = auth['zone'];
+    if (zone is Map && zone['code'] != null) {
+      iata = zone['code'].toString();
+    }
+    debugLog(
+        '[OFFLINE] Custom API forward for batch $batchNum '
+        '(${batch.length} pings, contact=$contact, iata=$iata)');
+    _customApiService.forwardPings(
+      batch,
+      contactOverride: contact,
+      iataOverride: iata,
+      source: 'offline',
+    );
+  }
+
   /// Delete an offline session without uploading
   Future<void> deleteOfflineSession(String filename) async {
     await _offlineSessionService.deleteSession(filename);
diff --git a/lib/services/custom_api_service.dart b/lib/services/custom_api_service.dart
index f5ba0c7..a657c86 100644
--- a/lib/services/custom_api_service.dart
+++ b/lib/services/custom_api_service.dart
@@ -41,17 +41,44 @@ class CustomApiService {
         _client = client ?? http.Client();
 
   /// Fire-and-forget: forward pings to the custom endpoint.
-  /// Called after successful MeshMapper upload. Never throws.
-  void forwardPings(List<Map<String, dynamic>> pings) {
+  /// Called after successful MeshMapper upload (online queue or offline session).
+  /// Never throws.
+  void forwardPings(
+    List<Map<String, dynamic>> pings, {
+    String? contactOverride,
+    String? iataOverride,
+    String source = 'online',
+  }) {
+    if (pings.isEmpty) return;
+
     final prefs = _prefsGetter();
     if (!prefs.customApiEnabled) return;
-    if (prefs.customApiUrl == null || prefs.customApiUrl!.isEmpty) return;
-    if (prefs.customApiKey == null || prefs.customApiKey!.isEmpty) return;
+
+    debugLog(
+        '[CUSTOM API] Forward requested ($source): ${pings.length} item(s)');
+
+    if (prefs.customApiUrl == null || prefs.customApiUrl!.isEmpty) {
+      debugLog('[CUSTOM API] Forward skipped ($source): URL not configured');
+      return;
+    }
+    if (prefs.customApiKey == null || prefs.customApiKey!.isEmpty) {
+      debugLog('[CUSTOM API] Forward skipped ($source): API key not configured');
+      return;
+    }
 
     // Enrich with contact and iata (custom API only — never sent to MeshMapper)
-    final contact =
-        prefs.customApiIncludeContact ? contactGetter?.call() : null;
-    final iata = iataGetter?.call();
+    final contact = prefs.customApiIncludeContact
+        ? (contactOverride ?? contactGetter?.call())
+        : null;
+    final iata = iataOverride ?? iataGetter?.call();
+
+    // Log the endpoint host only — the full URL may embed auth tokens, and
+    // debug log files are uploaded verbatim with bug reports.
+    var endpointHost = Uri.tryParse(prefs.customApiUrl!)?.host ?? '';
+    if (endpointHost.isEmpty) endpointHost = 'custom endpoint';
+
+    debugLog('[CUSTOM API] Forwarding ($source) → $endpointHost '
+        '(contact=${contact ?? "off"}, iata=${iata ?? "none"})');
 
     final enriched = pings.map((ping) {
       final enrichedPing = Map<String, dynamic>.from(ping);