diff --git a/backend/migrations/core/072_add_max_upload_batch_size.js b/backend/migrations/core/072_add_max_upload_batch_size.js
new file mode 100644
index 00000000..abd381d9
--- /dev/null
+++ b/backend/migrations/core/072_add_max_upload_batch_size.js
@@ -0,0 +1,38 @@
+/**
+ * Migration: re-add the configurable upload batch size setting (#509).
+ *
+ * Originally shipped via PR #214 (#208 fix) — users behind Cloudflare
+ * Tunnel and other reverse proxies with per-request size caps need to
+ * bound the chunked-upload size so they don't lose every batch >100MB.
+ * That migration + frontend wiring was lost during a `Merge main into
+ * beta for release/beta-to-main` resolution that picked main's older
+ * tree over beta's, silently deleting the file and reinstating the
+ * hardcoded 500MB chunk in PhotoUpload.tsx.
+ *
+ * Re-introducing the exact same migration here. Idempotent: skips the
+ * insert if the row already exists (e.g. installs that did go through
+ * the original 072 between #214 merge and the main-into-beta merge,
+ * where the migrations-table row was preserved even after the file
+ * was deleted).
+ */
+
+exports.up = async function(knex) {
+  const exists = await knex('app_settings')
+    .where({ setting_key: 'general_max_upload_batch_size_mb' })
+    .first();
+
+  if (!exists) {
+    await knex('app_settings').insert({
+      setting_key: 'general_max_upload_batch_size_mb',
+      setting_value: JSON.stringify(95),
+      setting_type: 'general',
+      updated_at: new Date()
+    });
+  }
+};
+
+exports.down = async function(knex) {
+  await knex('app_settings')
+    .where({ setting_key: 'general_max_upload_batch_size_mb' })
+    .del();
+};
diff --git a/frontend/src/components/admin/PhotoUpload.tsx b/frontend/src/components/admin/PhotoUpload.tsx
index f193c6a2..2cae80c8 100644
--- a/frontend/src/components/admin/PhotoUpload.tsx
+++ b/frontend/src/components/admin/PhotoUpload.tsx
@@ -163,9 +163,14 @@ export const PhotoUpload: React.FC<PhotoUploadProps> = ({ eventId, onUploadCompl
     setUploadProgress(0);
     setUploadIds([]);
 
-    // For large uploads, chunk the files by both count AND size to prevent memory/network issues
+    // For large uploads, chunk the files by both count AND size to prevent memory/network issues.
+    // #509: the per-chunk byte cap MUST be tunable so users behind Cloudflare Tunnel and other
+    // reverse proxies with request-size limits can drop it below their proxy's cap. Falls back
+    // to 95MB (Cloudflare-safe headroom under 100MB) when the setting is unset — that matches
+    // the value the migration seeds and is what worked in #208's resolution.
     const MAX_FILES_PER_CHUNK = Math.max(1, Math.min(50, maxFilesPerUpload)); // Max 50 files per chunk
-    const MAX_BYTES_PER_CHUNK = 500 * 1024 * 1024; // Max 500MB per chunk (nginx limit is 1GB)
+    const maxBatchSizeMb = Number(settings?.general_max_upload_batch_size_mb) || 95;
+    const MAX_BYTES_PER_CHUNK = maxBatchSizeMb * 1024 * 1024;
     const chunks: File[][] = [];
 
     let currentChunk: File[] = [];
diff --git a/frontend/src/features/settings/hooks/useSettingsState.ts b/frontend/src/features/settings/hooks/useSettingsState.ts
index a1ad55c7..420098f6 100644
--- a/frontend/src/features/settings/hooks/useSettingsState.ts
+++ b/frontend/src/features/settings/hooks/useSettingsState.ts
@@ -16,6 +16,8 @@ export interface GeneralSettings {
   max_file_size_mb: number;
   max_files_per_upload: number;
   allowed_file_types: string;
+  // #509 — re-added after the main-into-beta merge dropped it.
+  max_upload_batch_size_mb: number;
   enable_analytics: boolean;
   enable_registration: boolean;
   maintenance_mode: boolean;
@@ -91,6 +93,7 @@ export function useSettingsState() {
     max_file_size_mb: 50,
     max_files_per_upload: 500,
     allowed_file_types: 'jpg,jpeg,png,gif,webp',
+    max_upload_batch_size_mb: 95,
     enable_analytics: true,
     enable_registration: false,
     maintenance_mode: false,
@@ -177,6 +180,7 @@ export function useSettingsState() {
           Math.max(1, toNumber(settings.general_max_files_per_upload, 500))
         ),
         allowed_file_types: settings.general_allowed_file_types || 'jpg,jpeg,png,gif,webp',
+        max_upload_batch_size_mb: toNumber(settings.general_max_upload_batch_size_mb, 95),
         enable_analytics: toBoolean(settings.general_enable_analytics, true),
         enable_registration: toBoolean(settings.general_enable_registration, false),
         maintenance_mode: toBoolean(settings.general_maintenance_mode, false),
diff --git a/frontend/src/features/settings/tabs/GeneralTab.tsx b/frontend/src/features/settings/tabs/GeneralTab.tsx
index 8c7bd491..ba27bc3e 100644
--- a/frontend/src/features/settings/tabs/GeneralTab.tsx
+++ b/frontend/src/features/settings/tabs/GeneralTab.tsx
@@ -162,6 +162,28 @@ export const GeneralTab: React.FC<GeneralTabProps> = ({
                 {t('settings.general.maxFilesPerUploadHelp', { max: MAX_FILES_PER_UPLOAD_LIMIT })}
               </p>
             </div>
+            <div>
+              <label className="block text-sm font-medium text-neutral-700 dark:text-neutral-300 mb-1">
+                {t('settings.general.maxUploadBatchSize')}
+              </label>
+              <Input
+                type="number"
+                value={generalSettings.max_upload_batch_size_mb}
+                onChange={(e) => {
+                  const parsed = parseInt(e.target.value, 10);
+                  setGeneralSettings(prev => ({
+                    ...prev,
+                    max_upload_batch_size_mb: Number.isFinite(parsed)
+                      ? Math.max(1, parsed)
+                      : prev.max_upload_batch_size_mb
+                  }));
+                }}
+                min="1"
+              />
+              <p className="text-xs text-neutral-500 dark:text-neutral-400 mt-1">
+                {t('settings.general.maxUploadBatchSizeHelp')}
+              </p>
+            </div>
           </div>
 
           <div>
diff --git a/frontend/src/i18n/locales/de.json b/frontend/src/i18n/locales/de.json
index 63925399..6524a6aa 100644
--- a/frontend/src/i18n/locales/de.json
+++ b/frontend/src/i18n/locales/de.json
@@ -1031,6 +1031,8 @@
       "maxFileSize": "Max. Dateigröße (MB)",
       "maxFilesPerUpload": "Max. Dateien pro Upload",
       "maxFilesPerUploadHelp": "Maximale Anzahl an Fotos pro Upload-Vorgang (1-{{max}}).",
+      "maxUploadBatchSize": "Max. Upload-Paketgröße (MB)",
+      "maxUploadBatchSizeHelp": "Maximale Größe pro Upload-Anfrage. Reduzieren Sie diesen Wert bei Nutzung eines Reverse-Proxys mit Größenbeschränkung (z.B. Cloudflare: 100MB).",
       "allowedFileTypes": "Erlaubte Dateitypen",
       "allowedFileTypesHelp": "Kommagetrennte Liste von Dateierweiterungen",
       "featureToggles": "Funktionsschalter",
diff --git a/frontend/src/i18n/locales/en.json b/frontend/src/i18n/locales/en.json
index e5948b34..4a686dd8 100644
--- a/frontend/src/i18n/locales/en.json
+++ b/frontend/src/i18n/locales/en.json
@@ -670,6 +670,8 @@
       "maxFileSize": "Max File Size (MB)",
       "maxFilesPerUpload": "Max Files per Upload",
       "maxFilesPerUploadHelp": "Maximum number of photos allowed in a single upload batch (1-{{max}}).",
+      "maxUploadBatchSize": "Max Upload Batch Size (MB)",
+      "maxUploadBatchSizeHelp": "Maximum size per upload request. Lower this if behind a reverse proxy with request size limits (e.g. Cloudflare: 100MB).",
       "allowedFileTypes": "Allowed File Types",
       "allowedFileTypesHelp": "Comma-separated list of file extensions",
       "featureToggles": "Feature Toggles",