diff --git a/backend/migrations/core/086_migrate_non_grid_standard_to_banner.js b/backend/migrations/core/086_migrate_non_grid_standard_to_banner.js
index dcc9f29f..2d3340b6 100644
--- a/backend/migrations/core/086_migrate_non_grid_standard_to_banner.js
+++ b/backend/migrations/core/086_migrate_non_grid_standard_to_banner.js
@@ -8,8 +8,17 @@
  * a new 'banner' option has been added that adds the colored banner above
  * the standard header.
  *
+ * In the same release, GalleryView.tsx stopped deriving controlsStyle from
+ * the layout — non-grid events used to default to the sidebar drawer via
+ * `theme.galleryLayout !== 'grid' || isHeroHeader`, and now require an
+ * explicit `theme.controlsStyle === 'sidebar'`. To keep affected events
+ * pixel-identical post-upgrade, this migration also sets controlsStyle to
+ * 'sidebar' when it was previously unset on every event we flip to banner.
+ *
  * To keep current galleries looking the same, every event whose effective
- * config was non-grid + standard gets migrated to non-grid + banner.
+ * config was non-grid + standard gets migrated to non-grid + banner, and
+ * its controlsStyle is pinned to whatever the runtime would have used
+ * before the decoupling.
  */
 const NON_GRID_LAYOUTS = ['masonry', 'carousel', 'timeline', 'mosaic'];
 
@@ -22,6 +31,7 @@ exports.up = async function(knex) {
     .select('id', 'color_theme');
 
   let migratedCount = 0;
+  let controlsPinnedCount = 0;
 
   for (const event of events) {
     try {
@@ -37,6 +47,15 @@ exports.up = async function(knex) {
 
       const updatedTheme = { ...theme, headerStyle: 'banner' };
 
+      // Preserve previous filter placement: before this release, non-grid
+      // layouts implicitly rendered the sidebar drawer when controlsStyle
+      // was unset. Pin it to 'sidebar' so the visual stays identical. Don't
+      // overwrite explicit values the user may have set deliberately.
+      if (!theme.controlsStyle) {
+        updatedTheme.controlsStyle = 'sidebar';
+        controlsPinnedCount++;
+      }
+
       await knex('events')
         .where('id', event.id)
         .update({
@@ -51,6 +70,7 @@ exports.up = async function(knex) {
   }
 
   console.log(`[Migration 086] Migrated ${migratedCount} events from standard to banner`);
+  console.log(`[Migration 086] Pinned controlsStyle='sidebar' on ${controlsPinnedCount} events`);
 };
 
 exports.down = async function(knex) {
@@ -79,6 +99,15 @@ exports.down = async function(knex) {
 
       const revertedTheme = { ...theme, headerStyle: 'standard' };
 
+      // Symmetric with up: if controlsStyle is currently 'sidebar', drop it
+      // so the runtime falls back to whatever the older code would compute.
+      // Cannot perfectly distinguish "we set this" from "user agreed", but
+      // the scope is narrow (non-grid + banner) and rolling back is
+      // intentionally restoring pre-migration state.
+      if (revertedTheme.controlsStyle === 'sidebar') {
+        delete revertedTheme.controlsStyle;
+      }
+
       await knex('events')
         .where('id', event.id)
         .update({