Revert to version 3c8cf08

2026-04-14 03:10:27 +00:00 · 2026-04-14 03:10:27 +00:00 · 85d628fc54
commit 85d628fc54
parent 72f25886ec
32 changed files with 1683 additions and 1265 deletions
--- a/2
+++ b/2
@ -9,6 +9,8 @@ RUN yarn build


 FROM node:20.15.1-alpine
+# Install FFmpeg for video processing (reversed video generation)
+RUN apk add --no-cache ffmpeg
 WORKDIR /app
 COPY backend/package.json backend/yarn.lock ./
 RUN yarn install --pure-lockfile
--- a/Dockerfile.dev
+++ b/Dockerfile.dev
@ -11,16 +11,12 @@ WORKDIR /app/backend
 COPY backend/package.json backend/yarn.lock ./
 RUN yarn install --pure-lockfile

-FROM node:20.15.1-alpine AS app-shell-deps
-RUN apk add --no-cache git
-WORKDIR /app/app-shell
-COPY app-shell/package.json app-shell/yarn.lock ./
-RUN yarn install --pure-lockfile
-
 # Nginx setup and application build
 FROM node:20.15.1-alpine AS build
 RUN apk add --no-cache git nginx curl
 RUN apk add --no-cache lsof procps
+# Install FFmpeg for video processing (reversed video generation)
+RUN apk add --no-cache ffmpeg
 RUN yarn global add concurrently

 RUN apk add --no-cache \
@ -43,11 +39,9 @@ ENV PATH /root/.yarn/bin:/root/.config/yarn/global/node_modules/.bin:$PATH
 WORKDIR /app
 COPY --from=frontend-deps /app/frontend /app/frontend
 COPY --from=backend-deps /app/backend /app/backend
-COPY --from=app-shell-deps /app/app-shell /app/app-shell

 COPY frontend /app/frontend
 COPY backend /app/backend
-COPY app-shell /app/app-shell
 COPY docker /app/docker

 # Copy all files from root to /app
@ -68,8 +62,6 @@ EXPOSE 8080
 ENV NODE_ENV=dev_stage
 ENV FRONT_PORT=3001
 ENV BACKEND_PORT=3000
-ENV APP_SHELL_PORT=4000
-

 CMD ["sh", "-c", "\
  yarn --cwd /app/frontend dev & echo $! > /app/pids/frontend.pid && \
@ -80,6 +72,5 @@ CMD ["sh", "-c", "\
  while ! nc -z localhost ${BACKEND_PORT}; do \
    sleep 2; \
  done && \
-  echo 'Backend is up. Starting app_shell for Git check...' && \
-  yarn --cwd /app/app-shell start && \
-  wait $NGINX_PID"]
+  echo 'Backend and frontend are up.' && \
+  wait $NGINX_PID"]
--- a/backend/Dockerfile
+++ b/backend/Dockerfile
@ -1,6 +1,8 @@
 FROM node:20.15.1-alpine

-RUN apk update && apk add bash
+# Install bash and FFmpeg for video processing (reversed video generation)
+RUN apk update && apk add --no-cache bash ffmpeg
+
 # Create app directory
 WORKDIR /usr/src/app

--- a/backend/package.json
+++ b/backend/package.json
@ -27,6 +27,7 @@
    "dotenv": "^16.4.0",
    "express": "4.18.2",
    "express-validator": "^7.0.0",
+    "fluent-ffmpeg": "^2.1.3",
    "formidable": "1.2.2",
    "helmet": "^8.0.0",
    "joi": "^17.13.0",
--- a/backend/src/db/api/asset_variants.js
+++ b/backend/src/db/api/asset_variants.js
@ -72,6 +72,7 @@ class Asset_variantsDBApi extends GenericDBApi {
      id: data.id || undefined,
      variant_type: data.variant_type || null,
      cdn_url: data.cdn_url || null,
+      storage_key: data.storage_key || null,
      width_px: data.width_px || null,
      height_px: data.height_px || null,
      size_mb: data.size_mb || null,
--- a/backend/src/db/api/base.api.js
+++ b/backend/src/db/api/base.api.js
@ -213,6 +213,41 @@ class GenericDBApi {
    return record;
  }

+  /**
+   * Partial update - only updates fields explicitly passed in data.
+   * Unlike update(), this doesn't go through getFieldMapping which
+   * converts missing fields to null.
+   *
+   * Use this when you need to update specific fields without affecting others.
+   *
+   * @param {string} id - Record ID
+   * @param {Object} data - Fields to update (only these will be modified)
+   * @param {Object} options - Options with currentUser and transaction
+   */
+  static async partialUpdate(id, data, options = {}) {
+    const currentUser = options.currentUser || { id: null };
+    const transaction = options.transaction;
+
+    const record = await this.MODEL.findByPk(id, { transaction });
+
+    if (!record) {
+      throw { status: 404, message: `${this.TABLE_NAME} not found` };
+    }
+
+    const updatePayload = { updatedById: currentUser.id };
+
+    // Only include fields that are explicitly in the data object
+    for (const [key, value] of Object.entries(data)) {
+      if (value !== undefined) {
+        updatePayload[key] = value;
+      }
+    }
+
+    await record.update(updatePayload, { transaction });
+
+    return record;
+  }
+
  static async deleteByIds(ids, options = {}) {
    const currentUser = options.currentUser || { id: null };
    const transaction = options.transaction;
--- a/backend/src/db/migrations/20260413091125-add-reversed-variant-type.js
+++ b/backend/src/db/migrations/20260413091125-add-reversed-variant-type.js
@ -0,0 +1,33 @@
+'use strict';
+
+/**
+ * Migration: Add 'reversed' variant type to asset_variants
+ *
+ * This enables storing pre-reversed videos for back navigation transitions.
+ * Also adds storage_key column to track the S3/local storage path.
+ */
+
+/** @type {import('sequelize-cli').Migration} */
+module.exports = {
+  async up(queryInterface, Sequelize) {
+    // Add 'reversed' to the enum_asset_variants_variant_type enum
+    await queryInterface.sequelize.query(`
+      ALTER TYPE "enum_asset_variants_variant_type"
+      ADD VALUE IF NOT EXISTS 'reversed';
+    `);
+
+    // Add storage_key column if it doesn't exist
+    const tableInfo = await queryInterface.describeTable('asset_variants');
+    if (!tableInfo.storage_key) {
+      await queryInterface.addColumn('asset_variants', 'storage_key', {
+        type: Sequelize.TEXT,
+        allowNull: true,
+      });
+    }
+  },
+
+  async down() {
+    // PostgreSQL doesn't support removing enum values
+    // storage_key column is safe to leave (no data loss)
+  },
+};
--- a/backend/src/db/models/asset_variants.js
+++ b/backend/src/db/models/asset_variants.js
@ -23,9 +23,16 @@ module.exports = function (sequelize, DataTypes) {
          'mp4_high',

          'original',
+
+          'reversed',
        ],
      },

+      storage_key: {
+        type: DataTypes.TEXT,
+        allowNull: true,
+      },
+
      cdn_url: {
        type: DataTypes.TEXT,
        validate: {
--- a/backend/src/services/assets.js
+++ b/backend/src/services/assets.js
@ -1,6 +1,10 @@
 const AssetsDBApi = require('../db/api/assets');
+const Asset_variantsDBApi = require('../db/api/asset_variants');
 const { createEntityService } = require('../factories/service.factory');
 const ValidationError = require('./notifications/errors/validation');
+const { downloadToBuffer, uploadBuffer } = require('./file');
+const videoProcessing = require('./videoProcessing');
+const { logger } = require('../utils/logger');

 /**
 * Valid MIME type patterns for each asset type
@ -68,11 +72,11 @@ const BaseService = createEntityService(AssetsDBApi, {
 });

 /**
- * Assets Service with validation
+ * Assets Service with validation and video pre-processing
 */
 class AssetsService extends BaseService {
  /**
-   * Create asset with MIME type validation
+   * Create asset with MIME type validation and video pre-processing
   */
  static async create(data, currentUser) {
    // Validate asset_type and mime_type match
@ -85,7 +89,99 @@ class AssetsService extends BaseService {
    }

    // Call parent create
-    return super.create(data, currentUser);
+    const asset = await super.create(data, currentUser);
+
+    // Pre-generate reversed video for video assets (async, doesn't block response)
+    if (assetType === 'video' && data.storage_key) {
+      AssetsService.preGenerateReversedVideo(asset, currentUser).catch((err) => {
+        logger.error(
+          { err, assetId: asset.id },
+          'Failed to pre-generate reversed video (non-blocking)',
+        );
+      });
+    }
+
+    return asset;
+  }
+
+  /**
+   * Pre-generate reversed video variant for a video asset.
+   * Runs asynchronously after asset creation - doesn't block the upload response.
+   * This ensures reversed videos are ready for instant use in transitions.
+   *
+   * @param {Object} asset - Created asset record
+   * @param {Object} currentUser - Current user context
+   */
+  static async preGenerateReversedVideo(asset, currentUser) {
+    const log = logger.child({
+      assetId: asset.id,
+      operation: 'preGenerateReversed',
+    });
+
+    log.info('Starting pre-generation of reversed video');
+
+    try {
+      // Check if FFmpeg is available
+      const ffmpegAvailable = await videoProcessing.isFFmpegAvailable();
+      if (!ffmpegAvailable) {
+        log.warn('FFmpeg not available, skipping pre-generation');
+        return null;
+      }
+
+      // Check if reversed variant already exists (shouldn't happen on create, but safety check)
+      const existingAsset = await AssetsDBApi.findBy({ id: asset.id });
+      const variants = existingAsset?.asset_variants_asset || [];
+      const existingReversed = variants.find((v) => v.variant_type === 'reversed');
+
+      if (existingReversed) {
+        log.debug('Reversed variant already exists');
+        return existingReversed.storage_key;
+      }
+
+      // Download original video to buffer
+      const storageKey = asset.storage_key;
+      log.info({ storageKey }, 'Downloading original video');
+
+      const originalBuffer = await downloadToBuffer(storageKey);
+
+      // Generate reversed video
+      log.info('Generating reversed video with FFmpeg');
+      const reversedBuffer = await videoProcessing.reverseVideo(
+        originalBuffer,
+        asset.original_file_name || 'video.mp4',
+      );
+
+      // Upload reversed video to storage
+      const reversedKey = `assets/${asset.id}/reversed.mp4`;
+      log.info({ reversedKey }, 'Uploading reversed video');
+
+      const result = await uploadBuffer(reversedKey, reversedBuffer, {
+        contentType: 'video/mp4',
+      });
+
+      // Create variant record
+      await Asset_variantsDBApi.create(
+        {
+          assetId: asset.id,
+          variant_type: 'reversed',
+          cdn_url: result.url,
+          storage_key: reversedKey,
+          size_mb: reversedBuffer.length / (1024 * 1024),
+        },
+        { currentUser },
+      );
+
+      log.info(
+        { reversedKey, sizeMb: (reversedBuffer.length / (1024 * 1024)).toFixed(2) },
+        'Pre-generated reversed video successfully',
+      );
+
+      return reversedKey;
+    } catch (err) {
+      log.error({ err }, 'Failed to pre-generate reversed video');
+      // Don't throw - this is a background operation
+      return null;
+    }
  }

  /**
--- a/backend/src/services/file.js
+++ b/backend/src/services/file.js
@ -371,6 +371,78 @@ const deleteFile = async (privateUrl, options = {}) => {
  }
 };

+// ============================================================================
+// Download to Buffer (for processing)
+// ============================================================================
+
+/**
+ * Download a file to buffer (for processing)
+ * @param {string} privateUrl - Storage key/path
+ * @returns {Promise<Buffer>}
+ */
+const downloadToBuffer = async (privateUrl) => {
+  const provider = getFileStorageProvider();
+
+  if (provider === 's3') {
+    const s3 = getS3Provider();
+    const result = await s3.download(privateUrl);
+
+    // Convert stream to buffer
+    if (typeof result.body.transformToByteArray === 'function') {
+      const bytes = await result.body.transformToByteArray();
+      return Buffer.from(bytes);
+    }
+    // Handle readable stream
+    const chunks = [];
+    for await (const chunk of result.body) {
+      chunks.push(chunk);
+    }
+    return Buffer.concat(chunks);
+  } else if (provider === 'gcloud') {
+    const { bucket, hash } = getGCloudBucket();
+    const file = bucket.file(`${hash}/${privateUrl}`);
+    const [data] = await file.download();
+    return data;
+  } else {
+    // Local provider - read directly from filesystem
+    return fs.readFileSync(path.join(config.uploadDir, privateUrl));
+  }
+};
+
+/**
+ * Upload buffer to storage
+ * @param {string} privateUrl - Storage key/path
+ * @param {Buffer} buffer - File buffer to upload
+ * @param {Object} options - Upload options
+ * @param {string} [options.contentType] - MIME type
+ * @returns {Promise<{ url: string }>}
+ */
+const uploadBuffer = async (privateUrl, buffer, options = {}) => {
+  const provider = getFileStorageProvider();
+  const { contentType = 'application/octet-stream' } = options;
+
+  if (provider === 's3') {
+    const s3 = getS3Provider();
+    const result = await s3.upload(privateUrl, buffer, { contentType });
+    return { url: result.url };
+  } else if (provider === 'gcloud') {
+    const { bucket, hash } = getGCloudBucket();
+    const filePath = `${hash}/${privateUrl}`;
+    const blob = bucket.file(filePath);
+    await new Promise((resolve, reject) => {
+      const blobStream = blob.createWriteStream({ resumable: false });
+      blobStream.on('error', reject);
+      blobStream.on('finish', resolve);
+      blobStream.end(buffer);
+    });
+    return { url: `https://storage.googleapis.com/${bucket.name}/${blob.name}` };
+  } else {
+    const local = getLocalProvider();
+    await local.upload(privateUrl, buffer);
+    return { url: `/api/file/download?privateUrl=${encodeURIComponent(privateUrl)}` };
+  }
+};
+
 // ============================================================================
 // Chunked Upload Session Management
 // ============================================================================
@ -592,10 +664,16 @@ const generatePresignedUrls = async (urls) => {
 module.exports = {
  // Provider detection
  getFileStorageProvider,
+  getS3Provider,
+  getLocalProvider,
+  getGCloudBucket,
  // Unified interface
  uploadFile,
  downloadFile,
  deleteFile,
+  // Buffer operations
+  downloadToBuffer,
+  uploadBuffer,
  // Session-based chunked uploads
  initUploadSession,
  getUploadSession,
--- a/backend/src/services/tour_pages.js
+++ b/backend/src/services/tour_pages.js
@ -1,6 +1,542 @@
-const Tour_pagesDBApi = require('../db/api/tour_pages');
-const { createEntityService } = require('../factories/service.factory');
+/**
+ * Tour Pages Service
+ *
+ * Extends the factory service with reversed video generation for back navigation transitions.
+ *
+ * Supports two back navigation modes:
+ * 1. target_page: Back button has its own transitionVideoUrl - reversed video generated for it
+ * 2. history: Back button uses forward element from previous page - reversed video generated
+ *    for forward elements when project has any history-mode back buttons
+ */

-module.exports = createEntityService(Tour_pagesDBApi, {
+const Tour_pagesDBApi = require('../db/api/tour_pages');
+const AssetsDBApi = require('../db/api/assets');
+const Asset_variantsDBApi = require('../db/api/asset_variants');
+const { createEntityService } = require('../factories/service.factory');
+const { downloadToBuffer, uploadBuffer } = require('./file');
+const videoProcessing = require('./videoProcessing');
+const { logger } = require('../utils/logger');
+
+// Cache for project history-mode status (cleared per request cycle)
+const projectHistoryModeCache = new Map();
+
+// Create base service from factory
+const BaseService = createEntityService(Tour_pagesDBApi, {
  entityName: 'tour_pages',
 });
+
+/**
+ * Tour Pages Service with reversed video generation
+ */
+class TourPagesService extends BaseService {
+  /**
+   * Create tour page - generate reversed videos if needed
+   */
+  static async create(data, currentUser) {
+    // Process reversed videos and get updated ui_schema_json
+    const updatedData = await TourPagesService.processReversedVideosAndUpdateSchema(
+      data,
+      currentUser,
+    );
+
+    return super.create(updatedData, currentUser);
+  }
+
+  /**
+   * Update tour page - generate reversed videos if needed
+   */
+  static async update(data, id, currentUser) {
+    // Fetch existing page to get projectId (not included in update request body)
+    const existingPage = await Tour_pagesDBApi.findBy({ id });
+    const projectId = existingPage?.projectId || data.projectId || data.project_id;
+
+    // Process reversed videos and get updated ui_schema_json
+    const updatedData = await TourPagesService.processReversedVideosAndUpdateSchema(
+      { ...data, projectId, id },
+      currentUser,
+    );
+
+    return super.update(updatedData, id, currentUser);
+  }
+
+  /**
+   * Check if element is a back navigation button
+   * @private
+   */
+  static isBackElement(element) {
+    return (
+      element.type === 'navigation_prev' ||
+      (element.type?.startsWith?.('navigation') && element.navType === 'back')
+    );
+  }
+
+  /**
+   * Check if element is a forward navigation button with a target and transition
+   * @private
+   */
+  static isForwardElementWithTarget(element) {
+    const isForward =
+      element.type === 'navigation_next' ||
+      (element.type?.startsWith?.('navigation') &&
+        element.navType !== 'back' &&
+        element.type !== 'navigation_prev');
+    // Check for target (slug or legacy ID) and transition video
+    const hasTarget = element.targetPageSlug || element.targetPageId;
+    return isForward && hasTarget && element.transitionVideoUrl;
+  }
+
+  /**
+   * Check if any page in the project has a history-mode back button.
+   * Uses per-request caching to avoid repeated queries.
+   *
+   * @param {string} projectId - Project ID
+   * @returns {Promise<boolean>}
+   */
+  static async projectHasHistoryModeBackButton(projectId) {
+    if (!projectId) return false;
+
+    // Check cache first
+    if (projectHistoryModeCache.has(projectId)) {
+      return projectHistoryModeCache.get(projectId);
+    }
+
+    const { rows: pages } = await Tour_pagesDBApi.findAll(
+      { projectId },
+      { attributes: ['id', 'ui_schema_json'] },
+    );
+
+    logger.info(
+      { projectId, pageCount: pages.length },
+      'Checking project for history-mode back buttons',
+    );
+
+    for (const page of pages) {
+      const uiSchema =
+        typeof page.ui_schema_json === 'string'
+          ? JSON.parse(page.ui_schema_json || '{}')
+          : page.ui_schema_json || {};
+
+      if (!uiSchema.elements || !Array.isArray(uiSchema.elements)) continue;
+
+      for (const element of uiSchema.elements) {
+        const isBack = TourPagesService.isBackElement(element);
+
+        logger.debug(
+          {
+            pageId: page.id,
+            elementType: element.type,
+            navType: element.navType,
+            navBackMode: element.navBackMode,
+            isBack,
+          },
+          'Checking element for history mode',
+        );
+
+        if (isBack && element.navBackMode === 'history') {
+          logger.info(
+            { pageId: page.id, elementType: element.type },
+            'Found history-mode back button',
+          );
+          projectHistoryModeCache.set(projectId, true);
+          return true;
+        }
+      }
+    }
+
+    logger.info({ projectId }, 'No history-mode back buttons found in project');
+    projectHistoryModeCache.set(projectId, false);
+    return false;
+  }
+
+  /**
+   * Clear project cache (call at end of request or after project changes)
+   * @param {string} projectId - Project ID to clear, or undefined to clear all
+   */
+  static clearProjectCache(projectId) {
+    if (projectId) {
+      projectHistoryModeCache.delete(projectId);
+    } else {
+      projectHistoryModeCache.clear();
+    }
+  }
+
+  /**
+   * Process reversed videos and update ui_schema_json with reversed URLs.
+   * Returns data with updated ui_schema_json.
+   *
+   * Handles two cases:
+   * 1. Back navigation elements with transitionVideoUrl - always generate reversed
+   * 2. Forward navigation elements when project uses history-mode back navigation
+   *
+   * @param {Object} data - Page data with ui_schema_json
+   * @param {Object} currentUser - Current user for permissions
+   * @param {Object} options - Processing options
+   * @param {boolean} options._forceForwardReversed - Force processing forward elements
+   * @param {boolean} options._skipHistoryModeCheck - Skip initial history mode check
+   */
+  static async processReversedVideosAndUpdateSchema(
+    data,
+    currentUser,
+    options = {},
+  ) {
+    let uiSchema = data.ui_schema_json;
+    const wasString = typeof uiSchema === 'string';
+
+    // Parse if string
+    if (wasString) {
+      try {
+        uiSchema = JSON.parse(uiSchema);
+      } catch {
+        return data; // Return original data if parsing fails
+      }
+    }
+
+    if (!uiSchema?.elements || !Array.isArray(uiSchema.elements)) {
+      logger.debug({ hasElements: false }, 'No elements in ui_schema_json');
+      return data;
+    }
+
+    // Get project ID
+    const projectId = data.projectId || data.project_id || data.project;
+
+    // Check if this page being saved has a history-mode back button
+    // This is used to trigger regeneration of other pages' forward elements
+    let thisPageHasHistoryMode = false;
+
+    for (const element of uiSchema.elements) {
+      if (
+        TourPagesService.isBackElement(element) &&
+        element.navBackMode === 'history'
+      ) {
+        thisPageHasHistoryMode = true;
+        break;
+      }
+    }
+
+    // Check if project already has history-mode back buttons (from other pages)
+    // Skip this check if we're in regeneration mode to avoid recursion
+    let projectHasHistoryMode = options._forceForwardReversed || false;
+
+    if (!projectHasHistoryMode && projectId && !options._skipHistoryModeCheck) {
+      // Invalidate cache since we're about to save changes
+      TourPagesService.clearProjectCache(projectId);
+      projectHasHistoryMode =
+        await TourPagesService.projectHasHistoryModeBackButton(projectId);
+    }
+
+    // Combined check: process forward elements if project uses history mode OR this page enables it
+    const shouldProcessForward =
+      projectHasHistoryMode || thisPageHasHistoryMode;
+
+    logger.info(
+      {
+        thisPageHasHistoryMode,
+        projectHasHistoryMode,
+        shouldProcessForward,
+        projectId,
+      },
+      'History mode detection result',
+    );
+
+    let wasModified = false;
+
+    for (const element of uiSchema.elements) {
+      const isBack = TourPagesService.isBackElement(element);
+      const isForward = TourPagesService.isForwardElementWithTarget(element);
+
+      // Determine if this element needs reversed video
+      const needsReversed = isBack || (shouldProcessForward && isForward);
+
+      logger.debug(
+        {
+          elementType: element.type,
+          navType: element.navType,
+          isBack,
+          isForward,
+          needsReversed,
+          hasTransitionVideo: Boolean(element.transitionVideoUrl),
+          targetPageSlug: element.targetPageSlug,
+          targetPageId: element.targetPageId,
+          shouldProcessForward,
+        },
+        'Evaluating element for reversed video',
+      );
+
+      if (!needsReversed) continue;
+      if (!element.transitionVideoUrl) continue;
+
+      // Skip if already has a manually set reverseVideoUrl (separate_video mode)
+      if (
+        element.transitionReverseMode === 'separate_video' &&
+        element.reverseVideoUrl
+      ) {
+        continue;
+      }
+
+      const storageKey = element.transitionVideoUrl;
+
+      try {
+        // Get or generate reversed video URL
+        const reversedUrl = await TourPagesService.getOrGenerateReversedVariant(
+          storageKey,
+          currentUser,
+        );
+
+        if (reversedUrl && reversedUrl !== element.reverseVideoUrl) {
+          element.reverseVideoUrl = reversedUrl;
+          wasModified = true;
+          logger.info(
+            {
+              elementType: element.type,
+              isBack,
+              isForward,
+              storageKey,
+            },
+            'Added reversed video URL to element',
+          );
+        }
+      } catch (err) {
+        logger.error(
+          { err, storageKey },
+          'Failed to get/generate reversed variant',
+        );
+        // Continue without reversed video - button will be disabled in frontend
+      }
+    }
+
+    // If this page has a history-mode back button, trigger regeneration of
+    // other pages' forward elements that are missing reversed videos.
+    // This runs every save but only processes elements without reverseVideoUrl.
+    if (
+      thisPageHasHistoryMode &&
+      projectId &&
+      !options._skipHistoryModeCheck
+    ) {
+      logger.info(
+        { projectId },
+        'History mode back button detected - regenerating forward elements',
+      );
+
+      try {
+        await TourPagesService.regenerateProjectReversedVideos(
+          projectId,
+          currentUser,
+          data.id,
+        );
+      } catch (err) {
+        logger.error(
+          { err, projectId },
+          'Failed to regenerate project reversed videos',
+        );
+      }
+    }
+
+    if (wasModified) {
+      return {
+        ...data,
+        // Return same type as input: string if input was string, object otherwise
+        ui_schema_json: wasString ? JSON.stringify(uiSchema) : uiSchema,
+      };
+    }
+
+    return data;
+  }
+
+  /**
+   * Get existing reversed variant URL or generate one
+   * @param {string} storageKey - Original video storage key
+   * @param {Object} currentUser - Current user for permissions
+   * @returns {Promise<string|null>} Reversed video storage key or null
+   */
+  static async getOrGenerateReversedVariant(storageKey, currentUser) {
+    // Find the asset by storage key
+    const asset = await AssetsDBApi.findBy({ storage_key: storageKey });
+
+    if (!asset) {
+      logger.warn({ storageKey }, 'Asset not found for transition');
+      return null;
+    }
+
+    // Check if reversed variant already exists
+    const variants = asset.asset_variants_asset || [];
+    const reversedVariant = variants.find((v) => v.variant_type === 'reversed');
+
+    if (reversedVariant) {
+      logger.debug({ assetId: asset.id }, 'Using existing reversed variant');
+      return reversedVariant.storage_key;
+    }
+
+    // Generate reversed video
+    return TourPagesService.generateReversedVariant(asset, currentUser);
+  }
+
+  /**
+   * Generate reversed video variant for an asset
+   * @returns {Promise<string|null>} Reversed video storage key or null
+   */
+  static async generateReversedVariant(asset, currentUser) {
+    const log = logger.child({ assetId: asset.id });
+    log.info('Generating reversed video variant');
+
+    try {
+      // Check if FFmpeg is available
+      const ffmpegAvailable = await videoProcessing.isFFmpegAvailable();
+      if (!ffmpegAvailable) {
+        log.error('FFmpeg is not available on this server');
+        return null;
+      }
+
+      // Download original video to buffer
+      const originalBuffer = await downloadToBuffer(asset.storage_key);
+
+      // Generate reversed video
+      const reversedBuffer = await videoProcessing.reverseVideo(
+        originalBuffer,
+        asset.original_file_name || 'video.mp4',
+      );
+
+      // Upload reversed video to storage
+      const reversedKey = `assets/${asset.id}/reversed.mp4`;
+
+      const result = await uploadBuffer(reversedKey, reversedBuffer, {
+        contentType: 'video/mp4',
+      });
+
+      // Create variant record
+      await Asset_variantsDBApi.create(
+        {
+          assetId: asset.id,
+          variant_type: 'reversed',
+          cdn_url: result.url,
+          storage_key: reversedKey,
+          size_mb: reversedBuffer.length / (1024 * 1024),
+        },
+        { currentUser },
+      );
+
+      log.info(
+        { reversedKey, size: reversedBuffer.length },
+        'Reversed variant created',
+      );
+
+      return reversedKey;
+    } catch (err) {
+      log.error({ err }, 'Failed to generate reversed variant');
+      return null;
+    }
+  }
+
+  /**
+   * Regenerate reversed videos for all forward navigation elements in project.
+   * Called when history-mode back navigation is first enabled in a project.
+   *
+   * @param {string} projectId - Project ID
+   * @param {Object} currentUser - Current user for permissions
+   * @param {string} excludePageId - Optional page ID to exclude (the page being saved)
+   */
+  static async regenerateProjectReversedVideos(
+    projectId,
+    currentUser,
+    excludePageId,
+  ) {
+    const log = logger.child({ projectId, operation: 'regenerateReversed' });
+    log.info('Starting project-wide reversed video regeneration');
+
+    try {
+      // Only process dev environment pages (constructor works with dev)
+      const { rows: pages } = await Tour_pagesDBApi.findAll({
+        projectId,
+        environment: 'dev',
+      });
+
+      let pagesUpdated = 0;
+      let elementsProcessed = 0;
+
+      for (const page of pages) {
+        // Skip the page that triggered this regeneration (it's already being processed)
+        if (excludePageId && page.id === excludePageId) {
+          continue;
+        }
+
+        const uiSchema =
+          typeof page.ui_schema_json === 'string'
+            ? JSON.parse(page.ui_schema_json || '{}')
+            : page.ui_schema_json || {};
+
+        if (!uiSchema.elements || !Array.isArray(uiSchema.elements)) {
+          continue;
+        }
+
+        let pageModified = false;
+
+        for (const element of uiSchema.elements) {
+          // Process both forward elements AND back elements with their own transition
+          const isForward = TourPagesService.isForwardElementWithTarget(element);
+          const isBackWithTransition =
+            TourPagesService.isBackElement(element) &&
+            element.transitionVideoUrl;
+
+          log.debug({
+            pageId: page.id,
+            elementType: element.type,
+            navType: element.navType,
+            isForward,
+            isBackWithTransition,
+            hasTransitionVideo: Boolean(element.transitionVideoUrl),
+            hasReverseVideo: Boolean(element.reverseVideoUrl),
+            targetPageSlug: element.targetPageSlug,
+            targetPageId: element.targetPageId,
+          }, 'Checking element in regeneration');
+
+          // Skip if neither forward nor back-with-transition
+          if (!isForward && !isBackWithTransition) {
+            continue;
+          }
+
+          if (!element.transitionVideoUrl) continue;
+          if (element.reverseVideoUrl) continue; // Already has reversed
+
+          try {
+            const reversedUrl =
+              await TourPagesService.getOrGenerateReversedVariant(
+                element.transitionVideoUrl,
+                currentUser,
+              );
+
+            if (reversedUrl) {
+              element.reverseVideoUrl = reversedUrl;
+              pageModified = true;
+              elementsProcessed++;
+            }
+          } catch (err) {
+            log.error(
+              { err, pageId: page.id, elementType: element.type },
+              'Failed to generate reversed video for element',
+            );
+          }
+        }
+
+        if (pageModified) {
+          // Use partialUpdate to only update ui_schema_json field
+          // This avoids the regular update's getFieldMapping which sets other fields to null
+          await Tour_pagesDBApi.partialUpdate(
+            page.id,
+            { ui_schema_json: JSON.stringify(uiSchema) },
+            { currentUser },
+          );
+          pagesUpdated++;
+        }
+      }
+
+      log.info(
+        { pagesUpdated, elementsProcessed },
+        'Completed project-wide reversed video regeneration',
+      );
+    } catch (err) {
+      log.error({ err }, 'Failed to regenerate project reversed videos');
+      throw err;
+    }
+  }
+}
+
+module.exports = TourPagesService;
--- a/backend/src/services/videoProcessing.js
+++ b/backend/src/services/videoProcessing.js
@ -0,0 +1,89 @@
+/**
+ * Video Processing Service
+ *
+ * Provides video manipulation operations using FFmpeg.
+ * Used for generating reversed videos for back navigation transitions.
+ */
+
+const ffmpeg = require('fluent-ffmpeg');
+const fs = require('fs').promises;
+const path = require('path');
+const os = require('os');
+const { logger } = require('../utils/logger');
+
+/**
+ * Reverse a video using FFmpeg
+ * @param {Buffer} inputBuffer - Input video buffer
+ * @param {string} filename - Original filename (for extension)
+ * @returns {Promise<Buffer>} Reversed video buffer
+ */
+async function reverseVideo(inputBuffer, filename) {
+  const tempDir = await fs.mkdtemp(path.join(os.tmpdir(), 'video-reverse-'));
+  const ext = path.extname(filename) || '.mp4';
+  const inputPath = path.join(tempDir, `input${ext}`);
+  const outputPath = path.join(tempDir, `reversed${ext}`);
+
+  try {
+    // Write input buffer to temp file
+    await fs.writeFile(inputPath, inputBuffer);
+
+    logger.info({ inputPath, outputPath }, 'Starting video reversal');
+
+    // Reverse video with FFmpeg
+    await new Promise((resolve, reject) => {
+      ffmpeg(inputPath)
+        .outputOptions([
+          '-vf', 'reverse',
+          '-af', 'areverse',
+          '-c:v', 'libx264',
+          '-preset', 'fast',
+          '-crf', '23',
+          '-c:a', 'aac',
+          '-movflags', '+faststart',
+        ])
+        .output(outputPath)
+        .on('start', (cmd) => logger.debug({ cmd }, 'FFmpeg command'))
+        .on('progress', (progress) => {
+          if (progress.percent) {
+            logger.debug({ percent: progress.percent }, 'FFmpeg progress');
+          }
+        })
+        .on('end', () => {
+          logger.info({ outputPath }, 'Video reversal complete');
+          resolve();
+        })
+        .on('error', (err, stdout, stderr) => {
+          logger.error({ err, stdout, stderr }, 'FFmpeg error');
+          reject(err);
+        })
+        .run();
+    });
+
+    // Read output as buffer
+    return await fs.readFile(outputPath);
+  } finally {
+    // Cleanup temp files
+    try {
+      await fs.rm(tempDir, { recursive: true, force: true });
+    } catch (cleanupErr) {
+      logger.warn({ err: cleanupErr, tempDir }, 'Failed to cleanup temp dir');
+    }
+  }
+}
+
+/**
+ * Check if FFmpeg is available
+ * @returns {Promise<boolean>}
+ */
+async function isFFmpegAvailable() {
+  return new Promise((resolve) => {
+    ffmpeg.getAvailableFormats((err) => {
+      resolve(!err);
+    });
+  });
+}
+
+module.exports = {
+  reverseVideo,
+  isFFmpegAvailable,
+};
--- a/backend/yarn.lock
+++ b/backend/yarn.lock
@ -77,7 +77,7 @@
    "@smithy/util-utf8" "^2.0.0"
    tslib "^2.6.2"

-"@aws-crypto/sha256-js@^5.2.0", "@aws-crypto/sha256-js@5.2.0":
+"@aws-crypto/sha256-js@5.2.0", "@aws-crypto/sha256-js@^5.2.0":
  version "5.2.0"
  resolved "https://registry.npmjs.org/@aws-crypto/sha256-js/-/sha256-js-5.2.0.tgz"
  integrity sha512-FFQQyu7edu4ufvIZ+OadFpHHOt+eSTBaYaki44c+akjg7qZg9oOQeLlk77F6tSYqjDAFClrHJk9tMf0HdVyOvA==
@ -93,7 +93,7 @@
  dependencies:
    tslib "^2.6.2"

-"@aws-crypto/util@^5.2.0", "@aws-crypto/util@5.2.0":
+"@aws-crypto/util@5.2.0", "@aws-crypto/util@^5.2.0":
  version "5.2.0"
  resolved "https://registry.npmjs.org/@aws-crypto/util/-/util-5.2.0.tgz"
  integrity sha512-4RkU9EsI6ZpBve5fseQlGNUWKMa1RLPQ1dnjnQoe07ldfIzcsGb5hC5W0Dm7u423KWzawlrpbjXBrXCEv9zazQ==
@ -1542,13 +1542,10 @@ acorn-jsx@^5.3.2:
  resolved "https://registry.npmjs.org/acorn-jsx/-/acorn-jsx-5.3.2.tgz"
  integrity sha512-rq9s+JNhf0IChjtDXxllJ7g41oZk5SlXtp0LHwyA5cejwn7vKmKp4pPri6YEePv2PU65sAsegbXtIinmDFDXgQ==

-"acorn@^6.0.0 || ^7.0.0 || ^8.0.0", acorn@^8.9.0:
-  version "8.15.0"
-
-agent-base@^7.1.0, agent-base@^7.1.2:
-  version "7.1.4"
-  resolved "https://registry.npmjs.org/agent-base/-/agent-base-7.1.4.tgz"
-  integrity sha512-MnA+YT8fwfJPgBx3m60MNqakm30XOkyIoH1y6huTQvC0PwZG7ki8NacLBcrPbNoo8vEZy7Jpuk7+jMO+CUovTQ==
+acorn@^8.9.0:
+  version "8.16.0"
+  resolved "https://registry.yarnpkg.com/acorn/-/acorn-8.16.0.tgz#4ce79c89be40afe7afe8f3adb902a1f1ce9ac08a"
+  integrity sha512-UVJyE9MttOsBQIDKw1skb9nAwQuR5wuGD3+82K6JgJlm/Y+KI92oNsMNGZCYdDsVtRHSak0pcV5Dno5+4jh9sw==

 agent-base@6:
  version "6.0.2"
@ -1557,8 +1554,15 @@ agent-base@6:
  dependencies:
    debug "4"

+agent-base@^7.1.0, agent-base@^7.1.2:
+  version "7.1.4"
+  resolved "https://registry.npmjs.org/agent-base/-/agent-base-7.1.4.tgz"
+  integrity sha512-MnA+YT8fwfJPgBx3m60MNqakm30XOkyIoH1y6huTQvC0PwZG7ki8NacLBcrPbNoo8vEZy7Jpuk7+jMO+CUovTQ==
+
 ajv@^6.12.4:
-  version "6.12.6"
+  version "6.14.0"
+  resolved "https://registry.yarnpkg.com/ajv/-/ajv-6.14.0.tgz#fd067713e228210636ebb08c60bd3765d6dbe73a"
+  integrity sha512-IWrosm/yrn43eiKqkfkHis7QioDleaXQHdDVPKg0FSwwd/DuvyX79TZnFOnYpB7dcsFAMmtFztZuXPDvSePkFw==
  dependencies:
    fast-deep-equal "^3.1.1"
    fast-json-stable-stringify "^2.0.0"
@ -1722,6 +1726,11 @@ async-retry@^1.3.3:
  dependencies:
    retry "0.13.1"

+async@^0.2.9:
+  version "0.2.10"
+  resolved "https://registry.yarnpkg.com/async/-/async-0.2.10.tgz#b6bbe0b0674b9d719708ca38de8c237cb526c3d1"
+  integrity sha512-eAkdoKxU6/LkKDBzLpT+t6Ff5EtfSF4wx1WfJiPEEV7WNLnDaRXk0oVysiEPm262roaachGexwUv94WhSgN5TQ==
+
 asynckit@^0.4.0:
  version "0.4.0"
  resolved "https://registry.npmjs.org/asynckit/-/asynckit-0.4.0.tgz"
@ -1837,14 +1846,7 @@ brace-expansion@^1.1.7:
    balanced-match "^1.0.0"
    concat-map "0.0.1"

-brace-expansion@^2.0.1:
-  version "2.0.2"
-  resolved "https://registry.npmjs.org/brace-expansion/-/brace-expansion-2.0.2.tgz"
-  integrity sha512-Jt0vHyM+jmUBqojB7E1NIYadt0vI0Qxjxd2TErW94wDz+E2LAm5vKMXXwg6ZZBTHPuUlDgQHKXvjGBdfcF1ZDQ==
-  dependencies:
-    balanced-match "^1.0.0"
-
-brace-expansion@^2.0.2:
+brace-expansion@^2.0.1, brace-expansion@^2.0.2:
  version "2.0.2"
  resolved "https://registry.npmjs.org/brace-expansion/-/brace-expansion-2.0.2.tgz"
  integrity sha512-Jt0vHyM+jmUBqojB7E1NIYadt0vI0Qxjxd2TErW94wDz+E2LAm5vKMXXwg6ZZBTHPuUlDgQHKXvjGBdfcF1ZDQ==
@ -1960,22 +1962,7 @@ chalk@^4.0.0, chalk@^4.1.0:
    ansi-styles "^4.1.0"
    supports-color "^7.1.0"

-chokidar@^3.5.2:
-  version "3.6.0"
-  resolved "https://registry.npmjs.org/chokidar/-/chokidar-3.6.0.tgz"
-  integrity sha512-7VT13fmjotKpGipCW9JEQAusEPE+Ei8nl6/g4FBAmIm0GOOLMua9NDDo/DWp0ZAxCr3cPq5ZpBqmPAQgDda2Pw==
-  dependencies:
-    anymatch "~3.1.2"
-    braces "~3.0.2"
-    glob-parent "~5.1.2"
-    is-binary-path "~2.1.0"
-    is-glob "~4.0.1"
-    normalize-path "~3.0.0"
-    readdirp "~3.6.0"
-  optionalDependencies:
-    fsevents "~2.3.2"
-
-chokidar@^3.5.3:
+chokidar@^3.5.2, chokidar@^3.5.3:
  version "3.6.0"
  resolved "https://registry.npmjs.org/chokidar/-/chokidar-3.6.0.tgz"
  integrity sha512-7VT13fmjotKpGipCW9JEQAusEPE+Ei8nl6/g4FBAmIm0GOOLMua9NDDo/DWp0ZAxCr3cPq5ZpBqmPAQgDda2Pw==
@ -2030,6 +2017,11 @@ combined-stream@^1.0.8:
  dependencies:
    delayed-stream "~1.0.0"

+commander@6.2.0:
+  version "6.2.0"
+  resolved "https://registry.npmjs.org/commander/-/commander-6.2.0.tgz"
+  integrity sha512-zP4jEKbe8SHzKJYQmq8Y9gYjtO/POJLgIdKgV7B9qNmABVFVc+ctqSX6iXh4mCpJfRBOabiZ2YKPg8ciDw6C+Q==
+
 commander@^10.0.0:
  version "10.0.1"
  resolved "https://registry.npmjs.org/commander/-/commander-10.0.1.tgz"
@ -2040,11 +2032,6 @@ commander@^6.1.0:
  resolved "https://registry.npmjs.org/commander/-/commander-6.2.1.tgz"
  integrity sha512-U7VdrJFnJgo4xjrHpTzu0yrHPGImdsmD95ZlgYSEajAn2JKzDhDTPG9kBTefmObL2w/ngeZnilk+OV9CG3d7UA==

-commander@6.2.0:
-  version "6.2.0"
-  resolved "https://registry.npmjs.org/commander/-/commander-6.2.0.tgz"
-  integrity sha512-zP4jEKbe8SHzKJYQmq8Y9gYjtO/POJLgIdKgV7B9qNmABVFVc+ctqSX6iXh4mCpJfRBOabiZ2YKPg8ciDw6C+Q==
-
 concat-map@0.0.1:
  version "0.0.1"
  resolved "https://registry.npmjs.org/concat-map/-/concat-map-0.0.1.tgz"
@ -2068,7 +2055,7 @@ config-chain@^1.1.13:
    ini "^1.3.4"
    proto-list "~1.2.1"

-content-disposition@^0.5.3, content-disposition@0.5.4:
+content-disposition@0.5.4, content-disposition@^0.5.3:
  version "0.5.4"
  resolved "https://registry.npmjs.org/content-disposition/-/content-disposition-0.5.4.tgz"
  integrity sha512-FveZTNuGw04cxlAiWbzi6zTAL/lhehaWbTtgluJh4/E95DqMwTmha3KZN1aAWA8cFIhHzMZUvLevkw5Rqk+tSQ==
@ -2178,6 +2165,20 @@ dateformat@^4.6.3:
  resolved "https://registry.npmjs.org/dateformat/-/dateformat-4.6.3.tgz"
  integrity sha512-2P0p0pFGzHS5EMnhdxQi7aJN+iMheud0UhG4dlE1DLAlvL8JHjJJTX/CSm4JXwV0Ka5nGk3zC5mcb5bUQUxxMA==

+debug@2.6.9:
+  version "2.6.9"
+  resolved "https://registry.npmjs.org/debug/-/debug-2.6.9.tgz"
+  integrity sha512-bC7ElrdJaJnPbAP+1EotYvqZsb3ecl5wi6Bfi6BJTUcNowp6cvspg0jXznRTKDjm/E7AdgFBVeAPVMNcKGsHMA==
+  dependencies:
+    ms "2.0.0"
+
+debug@4, debug@^4, debug@^4.3.4, debug@^4.3.5:
+  version "4.3.5"
+  resolved "https://registry.npmjs.org/debug/-/debug-4.3.5.tgz"
+  integrity sha512-pt0bNEmneDIvdL1Xsd9oDQ/wrQRkXDT4AUWlNZNPKvW5x/jyO9VFXkJUP07vQ2upmw5PlaITaPKc31jK13V+jg==
+  dependencies:
+    ms "2.1.2"
+
 debug@^3.2.7:
  version "3.2.7"
  resolved "https://registry.npmjs.org/debug/-/debug-3.2.7.tgz"
@ -2185,34 +2186,13 @@ debug@^3.2.7:
  dependencies:
    ms "^2.1.1"

-debug@^4, debug@^4.3.4, debug@^4.3.5, debug@4:
-  version "4.3.5"
-  resolved "https://registry.npmjs.org/debug/-/debug-4.3.5.tgz"
-  integrity sha512-pt0bNEmneDIvdL1Xsd9oDQ/wrQRkXDT4AUWlNZNPKvW5x/jyO9VFXkJUP07vQ2upmw5PlaITaPKc31jK13V+jg==
-  dependencies:
-    ms "2.1.2"
-
-debug@^4.3.1:
+debug@^4.3.1, debug@^4.3.2:
  version "4.4.3"
  resolved "https://registry.npmjs.org/debug/-/debug-4.4.3.tgz"
  integrity sha512-RGwwWnwQvkVfavKVt22FGLw+xYSdzARwm0ru6DhTVA3umU5hZc28V3kO4stgYryrTlLpuvgI9GiijltAjNbcqA==
  dependencies:
    ms "^2.1.3"

-debug@^4.3.2:
-  version "4.4.3"
-  resolved "https://registry.npmjs.org/debug/-/debug-4.4.3.tgz"
-  integrity sha512-RGwwWnwQvkVfavKVt22FGLw+xYSdzARwm0ru6DhTVA3umU5hZc28V3kO4stgYryrTlLpuvgI9GiijltAjNbcqA==
-  dependencies:
-    ms "^2.1.3"
-
-debug@2.6.9:
-  version "2.6.9"
-  resolved "https://registry.npmjs.org/debug/-/debug-2.6.9.tgz"
-  integrity sha512-bC7ElrdJaJnPbAP+1EotYvqZsb3ecl5wi6Bfi6BJTUcNowp6cvspg0jXznRTKDjm/E7AdgFBVeAPVMNcKGsHMA==
-  dependencies:
-    ms "2.0.0"
-
 decamelize@^4.0.0:
  version "4.0.0"
  resolved "https://registry.npmjs.org/decamelize/-/decamelize-4.0.0.tgz"
@ -2256,16 +2236,16 @@ denque@^1.4.1:
  resolved "https://registry.npmjs.org/denque/-/denque-1.5.1.tgz"
  integrity sha512-XwE+iZ4D6ZUB7mfYRMb5wByE8L74HCn30FBN7sWnXksWc1LO1bPDl67pBR9o/kC4z/xSNAwkMYcGgqDV3BE3Hw==

-depd@^1.1.0:
-  version "1.1.2"
-  resolved "https://registry.npmjs.org/depd/-/depd-1.1.2.tgz"
-  integrity sha512-7emPTl6Dpo6JRXOXjLRxck+FlLRX5847cLKEn00PLAgc3g2hTZZgr+e4c2v6QpSmLeFP3n5yUo7ft6avBK/5jQ==
-
 depd@2.0.0:
  version "2.0.0"
  resolved "https://registry.npmjs.org/depd/-/depd-2.0.0.tgz"
  integrity sha512-g7nH6P6dyDioJogAAGprGpCtVImJhpPk/roCzdb3fIh61/s/nPsfR6onyMwkCAR/OlC3yBC0lESvUoQEAssIrw==

+depd@^1.1.0:
+  version "1.1.2"
+  resolved "https://registry.npmjs.org/depd/-/depd-1.1.2.tgz"
+  integrity sha512-7emPTl6Dpo6JRXOXjLRxck+FlLRX5847cLKEn00PLAgc3g2hTZZgr+e4c2v6QpSmLeFP3n5yUo7ft6avBK/5jQ==
+
 destroy@1.2.0:
  version "1.2.0"
  resolved "https://registry.npmjs.org/destroy/-/destroy-1.2.0.tgz"
@ -2276,6 +2256,13 @@ diff@^5.2.0:
  resolved "https://registry.npmjs.org/diff/-/diff-5.2.2.tgz"
  integrity sha512-vtcDfH3TOjP8UekytvnHH1o1P4FcUdt4eQ1Y+Abap1tk/OB2MWQvcwS2ClCd1zuIhc3JKOx6p3kod8Vfys3E+A==

+doctrine@3.0.0, doctrine@^3.0.0:
+  version "3.0.0"
+  resolved "https://registry.npmjs.org/doctrine/-/doctrine-3.0.0.tgz"
+  integrity sha512-yS+Q5i3hBf7GBkd4KG8a7eBNNWNGLTaEwwYWUijIYM7zrlYDM0BFXHjjPWlWZ1Rg7UaddZeIDmi9jF3HmqiQ2w==
+  dependencies:
+    esutils "^2.0.2"
+
 doctrine@^2.1.0:
  version "2.1.0"
  resolved "https://registry.npmjs.org/doctrine/-/doctrine-2.1.0.tgz"
@ -2283,13 +2270,6 @@ doctrine@^2.1.0:
  dependencies:
    esutils "^2.0.2"

-doctrine@^3.0.0, doctrine@3.0.0:
-  version "3.0.0"
-  resolved "https://registry.npmjs.org/doctrine/-/doctrine-3.0.0.tgz"
-  integrity sha512-yS+Q5i3hBf7GBkd4KG8a7eBNNWNGLTaEwwYWUijIYM7zrlYDM0BFXHjjPWlWZ1Rg7UaddZeIDmi9jF3HmqiQ2w==
-  dependencies:
-    esutils "^2.0.2"
-
 dotenv@^16.4.0:
  version "16.6.1"
  resolved "https://registry.npmjs.org/dotenv/-/dotenv-16.6.1.tgz"
@ -2324,7 +2304,7 @@ eastasianwidth@^0.2.0:
  resolved "https://registry.npmjs.org/eastasianwidth/-/eastasianwidth-0.2.0.tgz"
  integrity sha512-I88TYZWc9XiYHRQ4/3c5rjjfgkjhLyW2luGIheGERbNQ6OY7yTybanSpDXZa8y7VUP9YmDcYa+eyq4ca7iLqWA==

-ecdsa-sig-formatter@^1.0.11, ecdsa-sig-formatter@1.0.11:
+ecdsa-sig-formatter@1.0.11, ecdsa-sig-formatter@^1.0.11:
  version "1.0.11"
  resolved "https://registry.npmjs.org/ecdsa-sig-formatter/-/ecdsa-sig-formatter-1.0.11.tgz"
  integrity sha512-nagl3RYrbNv6kQkeJIpt6NJZy8twLB/2vtz6yN9Z4vRKHN4/QZJIEbqohALSgwKdnksuY3k5Addp5lg8sVoVcQ==
@ -2615,7 +2595,7 @@ eslint-visitor-keys@^3.4.1, eslint-visitor-keys@^3.4.3:
  resolved "https://registry.npmjs.org/eslint-visitor-keys/-/eslint-visitor-keys-3.4.3.tgz"
  integrity sha512-wpc+LXeiyiisxPlEkUzU6svyS1frIO3Mgxj1fdy7Pm8Ygzguax2N3Fa/D/ag1WqbOprdI+uY6wMUl8/a2G+iag==

-"eslint@^2 || ^3 || ^4 || ^5 || ^6 || ^7.2.0 || ^8 || ^9", "eslint@^6.0.0 || ^7.0.0 || >=8.0.0", eslint@^8.57.0:
+eslint@^8.57.0:
  version "8.57.1"
  resolved "https://registry.npmjs.org/eslint/-/eslint-8.57.1.tgz"
  integrity sha512-ypowyDxpVSYpkXr9WPv2PAZCtNip1Mv5KTW0SCurXv/9iOpcrH9PaqUElksqEB6pChqHGDRCFTyrZlGhnLNGiA==
@ -2715,7 +2695,7 @@ express-validator@^7.0.0:
    lodash "^4.17.21"
    validator "~13.15.23"

-"express@>=4.0.0 || >=5.0.0-beta", express@4.18.2:
+express@4.18.2:
  version "4.18.2"
  resolved "https://registry.npmjs.org/express/-/express-4.18.2.tgz"
  integrity sha512-5/PsL6iGPdfQ/lKM1UuielYgv3BUoJfz1aUwU9vHZ+J7gyvwdQXFEBIEIaxeGf0GIcreATNyBExtalisDbuMqQ==
@ -2789,7 +2769,7 @@ fast-xml-builder@^1.1.4:
  dependencies:
    path-expression-matcher "^1.1.3"

-fast-xml-parser@^5.3.4, fast-xml-parser@5.5.8:
+fast-xml-parser@5.5.8, fast-xml-parser@^5.3.4:
  version "5.5.8"
  resolved "https://registry.npmjs.org/fast-xml-parser/-/fast-xml-parser-5.5.8.tgz"
  integrity sha512-Z7Fh2nVQSb2d+poDViM063ix2ZGt9jmY1nWhPfHBOK2Hgnb/OW3P4Et3P/81SEej0J7QbWtJqxO05h8QYfK7LQ==
@ -2855,7 +2835,17 @@ flat@^5.0.2:
  integrity sha512-b6suED+5/3rTpUBdG1gupIl8MPFCAMA0QXwmljLhvCUKcUvdE4gWky9zpuGCcXHOsz4J9wPGNWq6OKpmIzz3hQ==

 flatted@^3.2.9:
-  version "3.3.3"
+  version "3.4.2"
+  resolved "https://registry.yarnpkg.com/flatted/-/flatted-3.4.2.tgz#f5c23c107f0f37de8dbdf24f13722b3b98d52726"
+  integrity sha512-PjDse7RzhcPkIJwy5t7KPWQSZ9cAbzQXcafsetQoD7sOJRQlGikNbx7yZp2OotDnJyrDcbyRq3Ttb18iYOqkxA==
+
+fluent-ffmpeg@^2.1.3:
+  version "2.1.3"
+  resolved "https://registry.yarnpkg.com/fluent-ffmpeg/-/fluent-ffmpeg-2.1.3.tgz#d6846be257777844249a4adeb320f25326d239f3"
+  integrity sha512-Be3narBNt2s6bsaqP6Jzq91heDgOEaDCJAXcE3qcma/EJBSy5FB4cvO31XBInuAuKBx8Kptf8dkhjK0IOru39Q==
+  dependencies:
+    async "^0.2.9"
+    which "^1.1.1"

 follow-redirects@^1.15.11:
  version "1.15.11"
@ -2917,7 +2907,7 @@ forwarded@0.2.0:
  resolved "https://registry.npmjs.org/forwarded/-/forwarded-0.2.0.tgz"
  integrity sha512-buRG0fpBtRHSTCOASe6hD258tEubFoRLb4ZNA6NxMVHNw2gOcwHo9wyablzMzOA5z9xA9L1KNjk/Nt6MT9aYow==

-fresh@^0.5.2, fresh@0.5.2:
+fresh@0.5.2, fresh@^0.5.2:
  version "0.5.2"
  resolved "https://registry.npmjs.org/fresh/-/fresh-0.5.2.tgz"
  integrity sha512-zJ2mQYM18rEFOudeV4GShTGIQ7RbzA7ozbU9I/XBpm7kqgMywgmylMwXHxZJmkVoYkna9d2pVXVXPdYTP9ej8Q==
@ -2937,6 +2927,11 @@ fs.realpath@^1.0.0:
  resolved "https://registry.npmjs.org/fs.realpath/-/fs.realpath-1.0.0.tgz"
  integrity sha512-OO0pH2lK6a0hZnAdau5ItzHPI6pUlvI7jMVnxUQRtw4owF2wk8lOSabtGDCTP4Ggrg2MbGnWO9X8K1t4+fGMDw==

+fsevents@~2.3.2:
+  version "2.3.3"
+  resolved "https://registry.yarnpkg.com/fsevents/-/fsevents-2.3.3.tgz#cac6407785d03675a2a5e1a5305c697b347d90d6"
+  integrity sha512-5xoDfX+fL7faATnagmWPpbFtwh/R77WmMMqqHGS65C3vvB0YHrgF+B1YmZ3441tMj5n63k0212XNoJwzlhffQw==
+
 function-bind@^1.1.2:
  version "1.1.2"
  resolved "https://registry.npmjs.org/function-bind/-/function-bind-1.1.2.tgz"
@ -3006,29 +3001,7 @@ get-caller-file@^2.0.5:
  resolved "https://registry.npmjs.org/get-caller-file/-/get-caller-file-2.0.5.tgz"
  integrity sha512-DyFP3BM/3YHTQOCUL/w0OZHR0lpKeGrxotcHWcqNEdnltqFwXVfhEBQ94eIo34AfQpo0rGki4cyIiftY06h2Fg==

-get-intrinsic@^1.1.3, get-intrinsic@^1.2.4:
-  version "1.2.4"
-  resolved "https://registry.npmjs.org/get-intrinsic/-/get-intrinsic-1.2.4.tgz"
-  integrity sha512-5uYhsJH8VJBTv7oslg4BznJYhDoRI6waYCxMmCdnTrcCrHA/fCFKoTFz2JKKE0HdDFUF7/oQuhzumXJK7paBRQ==
-  dependencies:
-    es-errors "^1.3.0"
-    function-bind "^1.1.2"
-    has-proto "^1.0.1"
-    has-symbols "^1.0.3"
-    hasown "^2.0.0"
-
-get-intrinsic@^1.2.1, get-intrinsic@^1.2.4:
-  version "1.2.4"
-  resolved "https://registry.npmjs.org/get-intrinsic/-/get-intrinsic-1.2.4.tgz"
-  integrity sha512-5uYhsJH8VJBTv7oslg4BznJYhDoRI6waYCxMmCdnTrcCrHA/fCFKoTFz2JKKE0HdDFUF7/oQuhzumXJK7paBRQ==
-  dependencies:
-    es-errors "^1.3.0"
-    function-bind "^1.1.2"
-    has-proto "^1.0.1"
-    has-symbols "^1.0.3"
-    hasown "^2.0.0"
-
-get-intrinsic@^1.2.3:
+get-intrinsic@^1.1.3, get-intrinsic@^1.2.1, get-intrinsic@^1.2.3, get-intrinsic@^1.2.4:
  version "1.2.4"
  resolved "https://registry.npmjs.org/get-intrinsic/-/get-intrinsic-1.2.4.tgz"
  integrity sha512-5uYhsJH8VJBTv7oslg4BznJYhDoRI6waYCxMmCdnTrcCrHA/fCFKoTFz2JKKE0HdDFUF7/oQuhzumXJK7paBRQ==
@ -3095,6 +3068,18 @@ glob-parent@~5.1.2:
  dependencies:
    is-glob "^4.0.1"

+glob@7.1.6:
+  version "7.1.6"
+  resolved "https://registry.npmjs.org/glob/-/glob-7.1.6.tgz"
+  integrity sha512-LwaxwyZ72Lk7vZINtNNrywX0ZuLyStrdDtabefZKAY5ZGJhVtgdznluResxNmPitE0SAO+O26sWTHeKSI2wMBA==
+  dependencies:
+    fs.realpath "^1.0.0"
+    inflight "^1.0.4"
+    inherits "2"
+    minimatch "^3.0.4"
+    once "^1.3.0"
+    path-is-absolute "^1.0.0"
+
 glob@^10.4.2:
  version "10.5.0"
  resolved "https://registry.npmjs.org/glob/-/glob-10.5.0.tgz"
@ -3130,18 +3115,6 @@ glob@^8.1.0:
    minimatch "^5.0.1"
    once "^1.3.0"

-glob@7.1.6:
-  version "7.1.6"
-  resolved "https://registry.npmjs.org/glob/-/glob-7.1.6.tgz"
-  integrity sha512-LwaxwyZ72Lk7vZINtNNrywX0ZuLyStrdDtabefZKAY5ZGJhVtgdznluResxNmPitE0SAO+O26sWTHeKSI2wMBA==
-  dependencies:
-    fs.realpath "^1.0.0"
-    inflight "^1.0.4"
-    inherits "2"
-    minimatch "^3.0.4"
-    once "^1.3.0"
-    path-is-absolute "^1.0.0"
-
 globals@^13.19.0:
  version "13.24.0"
  resolved "https://registry.npmjs.org/globals/-/globals-13.24.0.tgz"
@ -3326,20 +3299,6 @@ https-proxy-agent@^7.0.0, https-proxy-agent@^7.0.1:
    agent-base "^7.1.2"
    debug "4"

-iconv-lite@^0.6.2:
-  version "0.6.3"
-  resolved "https://registry.npmjs.org/iconv-lite/-/iconv-lite-0.6.3.tgz"
-  integrity sha512-4fCk79wshMdzMp2rH06qWrJE4iolqLhCUH+OiuIgU++RB0+94NlDL81atO7GX55uUKueo0txHNtvEyI6D7WdMw==
-  dependencies:
-    safer-buffer ">= 2.1.2 < 3.0.0"
-
-iconv-lite@^0.6.3:
-  version "0.6.3"
-  resolved "https://registry.npmjs.org/iconv-lite/-/iconv-lite-0.6.3.tgz"
-  integrity sha512-4fCk79wshMdzMp2rH06qWrJE4iolqLhCUH+OiuIgU++RB0+94NlDL81atO7GX55uUKueo0txHNtvEyI6D7WdMw==
-  dependencies:
-    safer-buffer ">= 2.1.2 < 3.0.0"
-
 iconv-lite@0.4.24:
  version "0.4.24"
  resolved "https://registry.npmjs.org/iconv-lite/-/iconv-lite-0.4.24.tgz"
@ -3347,6 +3306,13 @@ iconv-lite@0.4.24:
  dependencies:
    safer-buffer ">= 2.1.2 < 3"

+iconv-lite@^0.6.2, iconv-lite@^0.6.3:
+  version "0.6.3"
+  resolved "https://registry.npmjs.org/iconv-lite/-/iconv-lite-0.6.3.tgz"
+  integrity sha512-4fCk79wshMdzMp2rH06qWrJE4iolqLhCUH+OiuIgU++RB0+94NlDL81atO7GX55uUKueo0txHNtvEyI6D7WdMw==
+  dependencies:
+    safer-buffer ">= 2.1.2 < 3.0.0"
+
 ieee754@^1.2.1:
  version "1.2.1"
  resolved "https://registry.npmjs.org/ieee754/-/ieee754-1.2.1.tgz"
@ -3388,7 +3354,7 @@ inflight@^1.0.4:
    once "^1.3.0"
    wrappy "1"

-inherits@^2.0.3, inherits@^2.0.4, inherits@2, inherits@2.0.4:
+inherits@2, inherits@2.0.4, inherits@^2.0.3, inherits@^2.0.4:
  version "2.0.4"
  resolved "https://registry.npmjs.org/inherits/-/inherits-2.0.4.tgz"
  integrity sha512-k/vGaX4/Yla3WzyMCvTQOXYeIHvqOKtnqBduzTHpzpQZzAskKMhZ2K+EnBiSM9zGSoIFeMpXKxa4dYeZIQqewQ==
@ -3685,16 +3651,7 @@ is-symbol@^1.0.2, is-symbol@^1.0.3:
  dependencies:
    has-symbols "^1.0.2"

-is-symbol@^1.0.4:
-  version "1.1.1"
-  resolved "https://registry.npmjs.org/is-symbol/-/is-symbol-1.1.1.tgz"
-  integrity sha512-9gGx6GTtCQM73BgmHQXfDmLtfjjTUDSyoxTCbp5WtoixAhfgsDirWIcVQ/IHpvI5Vgd5i/J5F7B9cN/WlVbC/w==
-  dependencies:
-    call-bound "^1.0.2"
-    has-symbols "^1.1.0"
-    safe-regex-test "^1.1.0"
-
-is-symbol@^1.1.1:
+is-symbol@^1.0.4, is-symbol@^1.1.1:
  version "1.1.1"
  resolved "https://registry.npmjs.org/is-symbol/-/is-symbol-1.1.1.tgz"
  integrity sha512-9gGx6GTtCQM73BgmHQXfDmLtfjjTUDSyoxTCbp5WtoixAhfgsDirWIcVQ/IHpvI5Vgd5i/J5F7B9cN/WlVbC/w==
@ -4026,16 +3983,16 @@ media-typer@0.3.0:
  resolved "https://registry.npmjs.org/media-typer/-/media-typer-0.3.0.tgz"
  integrity sha512-dq+qelQ9akHpcOl/gUVRTxVIOkAJ1wR3QAvb4RsVjS8oVoFjDGTc679wJYmUmknUF5HwMLOgb5O+a3KxfWapPQ==

-merge-descriptors@^1.0.1:
-  version "1.0.3"
-  resolved "https://registry.npmjs.org/merge-descriptors/-/merge-descriptors-1.0.3.tgz"
-  integrity sha512-gaNvAS7TZ897/rVaZ0nMtAyxNyi/pdbjbAwUpFQpN70GqnVfOiXpeUUMKRBmzXaSQ8DdTX4/0ms62r2K+hE6mQ==
-
 merge-descriptors@1.0.1:
  version "1.0.1"
  resolved "https://registry.npmjs.org/merge-descriptors/-/merge-descriptors-1.0.1.tgz"
  integrity sha512-cCi6g3/Zr1iqQi6ySbseM1Xvooa98N0w31jzUYrXPX2xqObmFGHJ0tQ5u74H3mVh7wLouTseZyYIq39g8cNp1w==

+merge-descriptors@^1.0.1:
+  version "1.0.3"
+  resolved "https://registry.npmjs.org/merge-descriptors/-/merge-descriptors-1.0.3.tgz"
+  integrity sha512-gaNvAS7TZ897/rVaZ0nMtAyxNyi/pdbjbAwUpFQpN70GqnVfOiXpeUUMKRBmzXaSQ8DdTX4/0ms62r2K+hE6mQ==
+
 methods@^1.1.2, methods@~1.1.2:
  version "1.1.2"
  resolved "https://registry.npmjs.org/methods/-/methods-1.1.2.tgz"
@ -4053,7 +4010,7 @@ mime-types@^2.1.12, mime-types@^2.1.35, mime-types@~2.1.24, mime-types@~2.1.34:
  dependencies:
    mime-db "1.52.0"

-mime@^1.3.4, mime@1.6.0:
+mime@1.6.0, mime@^1.3.4:
  version "1.6.0"
  resolved "https://registry.npmjs.org/mime/-/mime-1.6.0.tgz"
  integrity sha512-x0Vn8spI+wuJ1O6S7gnbaQg8Pxh4NNHb7KSINmEWKiPE4RKOplvijn+NkmYmmRgP68mc70j2EbeTFRsrswaQeg==
@ -4084,14 +4041,7 @@ minimatch@^5.0.1, minimatch@^5.1.6:
  dependencies:
    brace-expansion "^2.0.1"

-minimatch@^9.0.1:
-  version "9.0.9"
-  resolved "https://registry.npmjs.org/minimatch/-/minimatch-9.0.9.tgz"
-  integrity sha512-OBwBN9AL4dqmETlpS2zasx+vTeWclWzkblfZk7KTA5j3jeOONz/tRCnZomUyvNg83wL5Zv9Ss6HMJXAgL8R2Yg==
-  dependencies:
-    brace-expansion "^2.0.2"
-
-minimatch@^9.0.4:
+minimatch@^9.0.1, minimatch@^9.0.4:
  version "9.0.9"
  resolved "https://registry.npmjs.org/minimatch/-/minimatch-9.0.9.tgz"
  integrity sha512-OBwBN9AL4dqmETlpS2zasx+vTeWclWzkblfZk7KTA5j3jeOONz/tRCnZomUyvNg83wL5Zv9Ss6HMJXAgL8R2Yg==
@ -4141,16 +4091,11 @@ moment-timezone@^0.5.43:
  dependencies:
    moment "^2.29.4"

-moment@^2.29.4, moment@2.30.1:
+moment@2.30.1, moment@^2.29.4:
  version "2.30.1"
  resolved "https://registry.npmjs.org/moment/-/moment-2.30.1.tgz"
  integrity sha512-uEmtNhbDOrWPFS+hdjFCBfy9f2YoyzRpwcl+DqpC6taX21FzsTLQVbMV/W7PzNSX6x/bhC1zA3c2UQ5NzH6how==

-ms@^2.1.1, ms@^2.1.3, ms@2.1.3:
-  version "2.1.3"
-  resolved "https://registry.npmjs.org/ms/-/ms-2.1.3.tgz"
-  integrity sha512-6FlzubTLZG3J2a/NVCAleEhjzq5oxgHyaCU9yYXvcLsvoVaHJq/s5xXI6/XXP6tz7R9xAOtHnSO/tXtF3WRTlA==
-
 ms@2.0.0:
  version "2.0.0"
  resolved "https://registry.npmjs.org/ms/-/ms-2.0.0.tgz"
@ -4161,6 +4106,11 @@ ms@2.1.2:
  resolved "https://registry.npmjs.org/ms/-/ms-2.1.2.tgz"
  integrity sha512-sGkPx+VjMtmA6MX27oA4FBFELFCZZ4S4XqeGOXCv68tT+jb3vk/RyaKWP0PTKyWtmLSM0b+adUTEvbs1PEaH2w==

+ms@2.1.3, ms@^2.1.1, ms@^2.1.3:
+  version "2.1.3"
+  resolved "https://registry.npmjs.org/ms/-/ms-2.1.3.tgz"
+  integrity sha512-6FlzubTLZG3J2a/NVCAleEhjzq5oxgHyaCU9yYXvcLsvoVaHJq/s5xXI6/XXP6tz7R9xAOtHnSO/tXtF3WRTlA==
+
 multer@^2.0.0:
  version "2.1.1"
  resolved "https://registry.npmjs.org/multer/-/multer-2.1.1.tgz"
@ -4377,11 +4327,6 @@ open@^8.0.0:
    is-docker "^2.1.1"
    is-wsl "^2.2.0"

-openapi-types@>=7:
-  version "12.1.3"
-  resolved "https://registry.npmjs.org/openapi-types/-/openapi-types-12.1.3.tgz"
-  integrity sha512-N4YtSYJqghVu4iek2ZUvcN/0aqH1kRDuNqzcycDxhOUpg7GdvLa2F3DgS6yBNhInhv2r/6I0Flkn7CqL8+nIcw==
-
 optionator@^0.9.3:
  version "0.9.4"
  resolved "https://registry.npmjs.org/optionator/-/optionator-0.9.4.tgz"
@ -4456,7 +4401,7 @@ passport-microsoft@^2.0.0:
  dependencies:
    passport-oauth2 "1.8.0"

-passport-oauth2@^1.1.2, passport-oauth2@1.8.0:
+passport-oauth2@1.8.0, passport-oauth2@^1.1.2:
  version "1.8.0"
  resolved "https://registry.npmjs.org/passport-oauth2/-/passport-oauth2-1.8.0.tgz"
  integrity sha512-cjsQbOrXIDE4P8nNb3FQRCCmJJ/utnFKEz2NX209f7KOHPoX18gF7gBzBbLLsj2/je4KrgiwLLGjf0lm9rtTBA==
@ -4467,7 +4412,7 @@ passport-oauth2@^1.1.2, passport-oauth2@1.8.0:
    uid2 "0.0.x"
    utils-merge "1.x.x"

-passport-strategy@^1.0.0, passport-strategy@1.x.x:
+passport-strategy@1.x.x, passport-strategy@^1.0.0:
  version "1.0.0"
  resolved "https://registry.npmjs.org/passport-strategy/-/passport-strategy-1.0.0.tgz"
  integrity sha512-CB97UUvDKJde2V0KDWWB3lyf6PC3FaZP7YxZ2G8OAtn9p4HI9j9JLP9qjOGZFvyl8uwNT8qM+hGnz/n16NI7oA==
@ -4567,7 +4512,7 @@ pg-types@2.2.0:
    postgres-date "~1.0.4"
    postgres-interval "^1.1.0"

-pg@^8.20.0, pg@>=8.0:
+pg@^8.20.0:
  version "8.20.0"
  resolved "https://registry.npmjs.org/pg/-/pg-8.20.0.tgz"
  integrity sha512-ldhMxz2r8fl/6QkXnBD3CR9/xg694oT6DZQ2s6c/RI28OjtSOpxnPrUCGOBJ46RCUxcWdx3p6kw/xnDHjKvaRA==
@ -4934,7 +4879,7 @@ safe-array-concat@^1.1.3:
    has-symbols "^1.1.0"
    isarray "^2.0.5"

-safe-buffer@^5.0.1, safe-buffer@^5.1.0, safe-buffer@^5.2.1, safe-buffer@~5.2.0, safe-buffer@5.2.1:
+safe-buffer@5.2.1, safe-buffer@^5.0.1, safe-buffer@^5.1.0, safe-buffer@^5.2.1, safe-buffer@~5.2.0:
  version "5.2.1"
  resolved "https://registry.npmjs.org/safe-buffer/-/safe-buffer-5.2.1.tgz"
  integrity sha512-rp3So07KcdmmKbGvgaNxQSJr7bGVSVk5S9Eq1F+ppbRo70+YeaDxkw5Dd8NPN+GD6bjnYm2VuPuCXmpuYvmCXQ==
@ -4990,12 +4935,7 @@ semver@^6.3.1:
  resolved "https://registry.npmjs.org/semver/-/semver-6.3.1.tgz"
  integrity sha512-BR7VvDCVHO+q2xBEWskxS6DJE1qRnb7DxzUrogb71CWoSficBxYsiAGd+Kl0mmq/MprG9yArRkyrQxTO6XjMzA==

-semver@^7.5.3:
-  version "7.7.4"
-  resolved "https://registry.npmjs.org/semver/-/semver-7.7.4.tgz"
-  integrity sha512-vFKC2IEtQnVhpT78h1Yp8wzwrf8CM+MzKMHGJZfBtzhZNycRFnXsHk6E5TxIkkMsgNS7mdX3AGB7x2QM2di4lA==
-
-semver@^7.5.4:
+semver@^7.5.3, semver@^7.5.4:
  version "7.7.4"
  resolved "https://registry.npmjs.org/semver/-/semver-7.7.4.tgz"
  integrity sha512-vFKC2IEtQnVhpT78h1Yp8wzwrf8CM+MzKMHGJZfBtzhZNycRFnXsHk6E5TxIkkMsgNS7mdX3AGB7x2QM2di4lA==
@ -5047,7 +4987,7 @@ sequelize-pool@^7.1.0:
  resolved "https://registry.npmjs.org/sequelize-pool/-/sequelize-pool-7.1.0.tgz"
  integrity sha512-G9c0qlIWQSK29pR/5U2JF5dDQeqqHRragoyahj/Nx4KOOQ3CPPfzxnfqFPCSB7x5UgjOgnZ61nSxz+fjDpRlJg==

-sequelize@^6.37.0, "sequelize@>= 4":
+sequelize@^6.37.0:
  version "6.37.8"
  resolved "https://registry.npmjs.org/sequelize/-/sequelize-6.37.8.tgz"
  integrity sha512-HJ0IQFqcTsTiqbEgiuioYFMSD00TP6Cz7zoTti+zVVBwVe9fEhev9cH6WnM3XU31+ABS356durAb99ZuOthnKw==
@ -5258,13 +5198,6 @@ streamsearch@^1.1.0:
  resolved "https://registry.npmjs.org/streamsearch/-/streamsearch-1.1.0.tgz"
  integrity sha512-Mcc5wHehp9aXz1ax6bZUyY5afg9u2rv5cqQI3mRrYkGC8rW2hM02jWuwjtL++LS5qinSyhj2QfLyNsuc+VsExg==

-string_decoder@^1.1.1, string_decoder@^1.3.0:
-  version "1.3.0"
-  resolved "https://registry.npmjs.org/string_decoder/-/string_decoder-1.3.0.tgz"
-  integrity sha512-hkRX8U1WjJFd8LsDJ2yQ/wWWxaopEsABU1XfkM8A+j0+85JAGppt16cr1Whg6KIbb4okU6Mql6BOj+uup/wKeA==
-  dependencies:
-    safe-buffer "~5.2.0"
-
 "string-width-cjs@npm:string-width@^4.2.0":
  version "4.2.3"
  resolved "https://registry.npmjs.org/string-width/-/string-width-4.2.3.tgz"
@ -5343,6 +5276,13 @@ string.prototype.trimstart@^1.0.8:
    define-properties "^1.2.1"
    es-object-atoms "^1.0.0"

+string_decoder@^1.1.1, string_decoder@^1.3.0:
+  version "1.3.0"
+  resolved "https://registry.npmjs.org/string_decoder/-/string_decoder-1.3.0.tgz"
+  integrity sha512-hkRX8U1WjJFd8LsDJ2yQ/wWWxaopEsABU1XfkM8A+j0+85JAGppt16cr1Whg6KIbb4okU6Mql6BOj+uup/wKeA==
+  dependencies:
+    safe-buffer "~5.2.0"
+
 "strip-ansi-cjs@npm:strip-ansi@^6.0.1":
  version "6.0.1"
  resolved "https://registry.npmjs.org/strip-ansi/-/strip-ansi-6.0.1.tgz"
@ -5688,7 +5628,7 @@ universalify@^2.0.0:
  resolved "https://registry.npmjs.org/universalify/-/universalify-2.0.1.tgz"
  integrity sha512-gptHNQghINnc/vTGIk0SOFGFNXw7JVrlRUtConJRlvaw6DuX0wO5Jeko9sWrMBhh+PsYAZ7oXAiOnf/UKogyiw==

-unpipe@~1.0.0, unpipe@1.0.0:
+unpipe@1.0.0, unpipe@~1.0.0:
  version "1.0.0"
  resolved "https://registry.npmjs.org/unpipe/-/unpipe-1.0.0.tgz"
  integrity sha512-pjy2bYhSsufwWlKwPc+l3cN7+wuJlK6uz0YdJEOlQDbl6jo/YlPi4mb8agUkVC8BF7V8NuzeyPNqRksA3hztKQ==
@ -5705,7 +5645,7 @@ util-deprecate@^1.0.1:
  resolved "https://registry.npmjs.org/util-deprecate/-/util-deprecate-1.0.2.tgz"
  integrity sha512-EPD5q1uXyFxJpCrLnCc1nHnq3gOa6DZBocAIiI2TaSCA7VCJ1UJDMagCzIkXNsUYfD1daK//LTEQ8xiIbrHtcw==

-utils-merge@^1.0.1, utils-merge@1.0.1, utils-merge@1.x.x:
+utils-merge@1.0.1, utils-merge@1.x.x, utils-merge@^1.0.1:
  version "1.0.1"
  resolved "https://registry.npmjs.org/utils-merge/-/utils-merge-1.0.1.tgz"
  integrity sha512-pMZTvIkT1d+TFGvDOqodOclx0QWkkgi6Tdoa8gC8ffGAAqz9pzPTZWAybbsHHoED/ztMtkv/VoYTYyShUn81hA==
@ -5715,12 +5655,7 @@ uuid@^8.0.0, uuid@^8.3.0, uuid@^8.3.2:
  resolved "https://registry.npmjs.org/uuid/-/uuid-8.3.2.tgz"
  integrity sha512-+NYs2QeMWy+GWFOEm9xnn6HCDp0l7QBD7ml8zLUmJ+93Q5NF0NocErnwkTkXVFNiX3/fpC6afS8Dhb/gz7R7eg==

-uuid@^9.0.0:
-  version "9.0.1"
-  resolved "https://registry.npmjs.org/uuid/-/uuid-9.0.1.tgz"
-  integrity sha512-b+1eJOlsR9K8HJpow9Ok3fiWOWSIcIzXodvv0rQjVoOVNpWMpxf1wZNpt4y9h10odCNrqnYp1OBzRktckBe3sA==
-
-uuid@^9.0.1:
+uuid@^9.0.0, uuid@^9.0.1:
  version "9.0.1"
  resolved "https://registry.npmjs.org/uuid/-/uuid-9.0.1.tgz"
  integrity sha512-b+1eJOlsR9K8HJpow9Ok3fiWOWSIcIzXodvv0rQjVoOVNpWMpxf1wZNpt4y9h10odCNrqnYp1OBzRktckBe3sA==
@ -5799,18 +5734,7 @@ which-collection@^1.0.2:
    is-weakmap "^2.0.2"
    is-weakset "^2.0.3"

-which-typed-array@^1.1.14:
-  version "1.1.15"
-  resolved "https://registry.npmjs.org/which-typed-array/-/which-typed-array-1.1.15.tgz"
-  integrity sha512-oV0jmFtUky6CXfkqehVvBP/LSWJ2sy4vWMioiENyJLePrBO/yKyV9OyJySfAKosh+RYkIl5zJCNZ8/4JncrpdA==
-  dependencies:
-    available-typed-arrays "^1.0.7"
-    call-bind "^1.0.7"
-    for-each "^0.3.3"
-    gopd "^1.0.1"
-    has-tostringtag "^1.0.2"
-
-which-typed-array@^1.1.15:
+which-typed-array@^1.1.14, which-typed-array@^1.1.15:
  version "1.1.15"
  resolved "https://registry.npmjs.org/which-typed-array/-/which-typed-array-1.1.15.tgz"
  integrity sha512-oV0jmFtUky6CXfkqehVvBP/LSWJ2sy4vWMioiENyJLePrBO/yKyV9OyJySfAKosh+RYkIl5zJCNZ8/4JncrpdA==
@ -5834,6 +5758,13 @@ which-typed-array@^1.1.16, which-typed-array@^1.1.19:
    gopd "^1.2.0"
    has-tostringtag "^1.0.2"

+which@^1.1.1:
+  version "1.3.1"
+  resolved "https://registry.yarnpkg.com/which/-/which-1.3.1.tgz#a45043d54f5805316da8d62f9f50918d3da70b0a"
+  integrity sha512-HxJdYWq1MTIQbJ3nw0cqssHoTNU267KlrDuGZ1WYlxDStUtKUhOaJmh112/TZmHxxUfuJqPXSOm7tDyas0OSIQ==
+  dependencies:
+    isexe "^2.0.0"
+
 which@^2.0.1:
  version "2.0.2"
  resolved "https://registry.npmjs.org/which/-/which-2.0.2.tgz"
--- a/docker/docker-compose.yml
+++ b/docker/docker-compose.yml
@ -1,5 +1,3 @@
-
-
 version: "3.9"
 services:
  web:
@ -14,12 +12,8 @@ services:
      options:
        max-size: "10m"
        max-file: "3"
+
  db:
-    logging:
-      driver: json-file
-      options:
-        max-size: "10m"
-        max-file: "3"
    image: postgres
    volumes:
      - ./data/db:/var/lib/postgresql/data
@ -36,23 +30,19 @@ services:

  backend:
    image: backend
-    volumes:
-    - ./wait-for-it.sh:/usr/src/app/wait-for-it.sh
-    - ./start-backend.sh:/usr/src/app/start-backend.sh
    build: ../backend
+    volumes:
+      - ./wait-for-it.sh:/usr/src/app/wait-for-it.sh
+      - ./start-backend.sh:/usr/src/app/start-backend.sh
    environment:
-     - DB_HOST=db
+      - DB_HOST=db
    ports:
-     - "8080:8080"
-     logging:
-       driver: json-file
-       options:
-         max-size: "10m"
-         max-file: "3"
+      - "8080:8080"
+    logging:
+      driver: json-file
+      options:
+        max-size: "10m"
+        max-file: "3"
    depends_on:
-     - "db"
-    
-
-    
+      - "db"
    command: ["bash", "./wait-for-it.sh", "db:5432", "--timeout=0", "--strict", "--", "bash", "./start-backend.sh"]
-    
--- a/frontend/next-env.d.ts
+++ b/frontend/next-env.d.ts
@ -1,6 +1,6 @@
 /// <reference types="next" />
 /// <reference types="next/image-types/global" />
-/// <reference path="./.next/types/routes.d.ts" />
+/// <reference path="./build/types/routes.d.ts" />

 // NOTE: This file should not be edited
 // see https://nextjs.org/docs/pages/api-reference/config/typescript for more information.
--- a/frontend/src/components/Constructor/CanvasBackground.tsx
+++ b/frontend/src/components/Constructor/CanvasBackground.tsx
@ -15,8 +15,10 @@ interface CanvasBackgroundProps {
  backgroundVideoUrl?: string;
  backgroundAudioUrl?: string;
  previousBgImageUrl?: string;
+  previousBgVideoUrl?: string;
  isSwitching?: boolean;
  isNewBgReady?: boolean;
+  isFadingIn?: boolean;
  onBackgroundReady?: () => void;
  // Video playback settings
  videoAutoplay?: boolean;
@ -31,8 +33,10 @@ const CanvasBackground: React.FC<CanvasBackgroundProps> = ({
  backgroundVideoUrl,
  backgroundAudioUrl,
  previousBgImageUrl,
+  previousBgVideoUrl,
  isSwitching = false,
  isNewBgReady = false,
+  isFadingIn = false,
  onBackgroundReady,
  videoAutoplay = true,
  videoLoop = true,
@ -94,10 +98,12 @@ const CanvasBackground: React.FC<CanvasBackgroundProps> = ({
        </div>
      )}

-      {/* Previous background overlay - shows during page switch until new bg is ready */}
-      {previousBgImageUrl && isSwitching && !isNewBgReady && (
+      {/* Previous background overlays - show during loading AND crossfade.
+          Uses CSS animation for fade-out effect during crossfade.
+          z-0 keeps them BELOW new backgrounds (z-1). */}
+      {previousBgImageUrl && (isFadingIn || (isSwitching && !isNewBgReady)) && (
        <div
-          className='pointer-events-none absolute inset-0 z-10'
+          className={`pointer-events-none absolute inset-0 z-0 ${isFadingIn ? 'animate-crossfade-out' : ''}`}
          style={{
            backgroundImage: `url("${previousBgImageUrl}")`,
            backgroundSize: 'contain',
@ -106,6 +112,16 @@ const CanvasBackground: React.FC<CanvasBackgroundProps> = ({
          }}
        />
      )}
+      {previousBgVideoUrl && (isFadingIn || (isSwitching && !isNewBgReady)) && (
+        <video
+          className={`absolute inset-0 z-0 h-full w-full object-contain pointer-events-none ${isFadingIn ? 'animate-crossfade-out' : ''}`}
+          src={previousBgVideoUrl}
+          autoPlay
+          loop
+          muted
+          playsInline
+        />
+      )}

      {/* Background video - z-1 keeps it below backdrop blur layer (z-5) */}
      {backgroundVideoUrl && (
--- a/frontend/src/components/Constructor/TransitionPreviewOverlay.tsx
+++ b/frontend/src/components/Constructor/TransitionPreviewOverlay.tsx
@ -4,6 +4,9 @@
 * Full-screen overlay for transition video preview.
 * Designed to work with useTransitionPlayback hook which manages
 * video src and playback externally via the videoRef.
+ *
+ * Supports letterbox mode to constrain transitions within canvas bounds,
+ * matching the behavior of background images and UI elements.
 */

 import React from 'react';
@ -15,26 +18,53 @@ interface TransitionPreviewOverlayProps {
  isActive: boolean;
  /** Whether the video is currently buffering (used to hide video during load) */
  isBuffering?: boolean;
+  /** Letterbox styles from useCanvasScale - positions overlay within canvas bounds */
+  letterboxStyles?: React.CSSProperties;
+  /** Video object-fit mode (default: 'contain' to match backgrounds) */
+  videoFit?: 'contain' | 'cover';
+  /** Additional opacity value for fade-out effects (0-1) */
+  opacity?: number;
 }

 const TransitionPreviewOverlay: React.FC<TransitionPreviewOverlayProps> = ({
  videoRef,
  isActive,
  isBuffering = false,
+  letterboxStyles,
+  videoFit = 'contain',
+  opacity,
 }) => {
  if (!isActive) return null;

+  // Video opacity: 0 while buffering, 1 otherwise
+  const videoOpacity = isBuffering ? 0 : 1;
+  // Container opacity: controlled by parent for fade-out effects
+  const containerOpacity = opacity ?? 1;
+
  return (
-    <div className='fixed inset-0 z-50 overflow-hidden pointer-events-none'>
-      <video
-        ref={videoRef}
-        className='absolute inset-0 h-full w-full object-cover transition-opacity duration-300 ease-linear'
-        style={{ opacity: isBuffering ? 0 : 1 }}
-        muted
-        playsInline
-        preload='auto'
-        disablePictureInPicture
-      />
+    // Outer: full viewport with black background (letterbox bars)
+    // No fade transition - transition video itself is the effect
+    <div
+      className='fixed inset-0 z-50 overflow-hidden pointer-events-none bg-black'
+      style={{ opacity: containerOpacity }}
+    >
+      {/* Inner: respects letterbox dimensions when provided */}
+      <div
+        className='overflow-hidden'
+        style={letterboxStyles || { position: 'absolute', inset: 0 }}
+      >
+        <video
+          ref={videoRef}
+          className={`absolute inset-0 h-full w-full transition-opacity duration-300 ease-linear ${
+            videoFit === 'cover' ? 'object-cover' : 'object-contain'
+          }`}
+          style={{ opacity: videoOpacity }}
+          muted
+          playsInline
+          preload='auto'
+          disablePictureInPicture
+        />
+      </div>
    </div>
  );
 };
--- a/frontend/src/components/RuntimePresentation.tsx
+++ b/frontend/src/components/RuntimePresentation.tsx
@ -22,6 +22,7 @@ import BaseButton from './BaseButton';
 import CardBox from './CardBox';
 import { OfflineToggle } from './Offline/OfflineToggle';
 import RuntimeElement from './RuntimeElement';
+import TransitionPreviewOverlay from './Constructor/TransitionPreviewOverlay';
 import GalleryCarouselOverlay from './UiElements/GalleryCarouselOverlay';
 import { BackdropPortalProvider } from './BackdropPortal';
 import { RotatePrompt } from './RotatePrompt';
@ -100,7 +101,8 @@ export default function RuntimePresentation({
    targetPageId: string;
    videoUrl: string;
    storageKey: string;
-    isReverse: boolean;
+    isBack: boolean;
+    reverseVideoUrl?: string;
  } | null>(null);
  const [isFullscreen, setIsFullscreen] = useState(false);
  const [isBackgroundReady, setIsBackgroundReady] = useState(true);
@ -185,10 +187,11 @@ export default function RuntimePresentation({
      ? {
          videoUrl: transitionPreview.videoUrl,
          storageKey: transitionPreview.storageKey,
-          reverseMode: transitionPreview.isReverse ? 'reverse' : 'none',
+          reverseMode: transitionPreview.reverseVideoUrl ? 'separate' : 'none',
+          reverseVideoUrl: transitionPreview.reverseVideoUrl,
          targetPageId: transitionPreview.targetPageId,
          displayName: 'Transition',
-          isBack: transitionPreview.isReverse, // Pass through for history management
+          isBack: transitionPreview.isBack,
        }
      : null,
    onComplete: async (targetPageId, isBack) => {
@ -226,12 +229,12 @@ export default function RuntimePresentation({
    },
  });

-  // Use shared background transition hook for fade-out and fade-in effects
+  // Use shared background transition hook for crossfade effects
  const {
    isOverlayFadingOut,
    resetFadeOut,
    isFadingIn,
-    elementsOpacity,
+    onFadeInAnimationEnd,
    resetFadeIn,
  } = useBackgroundTransition({
    pageSwitch,
@ -331,6 +334,7 @@ export default function RuntimePresentation({
      targetPageId: string,
      transitionVideoUrl?: string,
      isBack = false,
+      reverseVideoUrl?: string,
    ) => {
      const targetPage = pages.find((p) => p.id === targetPageId);
      if (!targetPage) return;
@ -346,13 +350,16 @@ export default function RuntimePresentation({
          targetPageId,
          videoUrl: resolveAssetPlaybackUrl(transitionVideoUrl),
          storageKey: transitionVideoUrl, // Raw storage path for cache lookup
-          isReverse: isBack,
+          isBack,
+          reverseVideoUrl: reverseVideoUrl
+            ? resolveAssetPlaybackUrl(reverseVideoUrl)
+            : undefined,
        });
      } else {
-        // Direct navigation - use shared hook for smooth transition
-        // Reset fade-in state to start fresh
-        resetFadeIn();
-        // Previous background stays visible until new one is ready
+        // Direct navigation with crossfade effect:
+        // useBackgroundTransition detects switching and applies animation classes
+        // - New page gets animate-crossfade-in (0 → 1)
+        // - Previous background gets animate-crossfade-out (1 → 0)
        setIsBackgroundReady(false);
        // Mark this page as initialized to prevent redundant effect calls
        lastInitializedPageIdRef.current = targetPageId;
@ -398,6 +405,7 @@ export default function RuntimePresentation({
          navTarget.pageId,
          navTarget.transitionVideoUrl,
          navTarget.isBack,
+          navTarget.reverseVideoUrl,
        );
      }
    },
@ -534,65 +542,17 @@ export default function RuntimePresentation({
          style={{
            ...cssVars,
            ...letterboxStyles,
-            backgroundImage: backgroundImageUrl
-              ? `url("${backgroundImageUrl}")`
-              : undefined,
-            backgroundSize: 'contain',
-            backgroundPosition: 'center',
-            backgroundRepeat: 'no-repeat',
          }}
        >
          <BackdropPortalProvider>
-            {/* Background image element - z-1 keeps it below backdrop blur (z-5).
-            CSS backgroundImage provides instant display.
-            Use native img for blob URLs to prevent repeated fetch requests from Next.js Image. */}
-            {backgroundImageUrl && !backgroundVideoUrl && (
-              <div className='absolute inset-0 z-1 pointer-events-none'>
-                {backgroundImageUrl.startsWith('blob:') ? (
-                  // eslint-disable-next-line @next/next/no-img-element
-                  <img
-                    key={backgroundImageUrl}
-                    src={backgroundImageUrl}
-                    alt=''
-                    className='absolute inset-0 w-full h-full object-contain'
-                    onLoad={() => {
-                      setIsBackgroundReady(true);
-                      pageSwitch.markBackgroundReady();
-                    }}
-                    onError={() => {
-                      setIsBackgroundReady(true);
-                      pageSwitch.markBackgroundReady();
-                    }}
-                  />
-                ) : (
-                  <Image
-                    key={backgroundImageUrl}
-                    src={backgroundImageUrl}
-                    alt=''
-                    fill
-                    sizes='100vw'
-                    className='object-contain'
-                    priority
-                    unoptimized
-                    onLoad={() => {
-                      setIsBackgroundReady(true);
-                      pageSwitch.markBackgroundReady();
-                    }}
-                    onError={() => {
-                      setIsBackgroundReady(true);
-                      pageSwitch.markBackgroundReady();
-                    }}
-                  />
-                )}
-              </div>
-            )}
-
-            {/* Previous background overlay - shows during direct navigation until new bg is ready */}
+            {/* Previous background overlays - show during loading AND crossfade.
+                Uses CSS animation for fade-out effect.
+                Cleared by useBackgroundTransition after fade completes. */}
            {pageSwitch.previousBgImageUrl &&
-              pageSwitch.isSwitching &&
-              !pageSwitch.isNewBgReady && (
+              (isFadingIn ||
+                (pageSwitch.isSwitching && !pageSwitch.isNewBgReady)) && (
                <div
-                  className='absolute inset-0 pointer-events-none z-10'
+                  className={`absolute inset-0 pointer-events-none z-0 ${isFadingIn ? 'animate-crossfade-out' : ''}`}
                  style={{
                    backgroundImage: `url("${pageSwitch.previousBgImageUrl}")`,
                    backgroundSize: 'contain',
@ -601,43 +561,101 @@ export default function RuntimePresentation({
                  }}
                />
              )}
-
-            {/* Background video - z-1 keeps it below backdrop blur (z-5) */}
-            {backgroundVideoUrl && (
-              <video
-                ref={bgVideoRef}
-                key={backgroundVideoUrl}
-                className='absolute inset-0 z-1 h-full w-full object-contain'
-                src={backgroundVideoUrl}
-                autoPlay={videoAutoplay}
-                loop={useNativeLoop}
-                muted={videoMuted}
-                playsInline
-              />
-            )}
-
-            {/* Page elements - z-40 ensures they appear above carousel background (z-10) and carousel controls (z-30) */}
-            <div
-              className='absolute inset-0 z-40'
-              style={{
-                opacity: elementsOpacity,
-                transition: isFadingIn
-                  ? `opacity ${CANVAS_CONFIG.pageTransition.fadeInDurationMs}ms ${CANVAS_CONFIG.pageTransition.easing}`
-                  : 'none',
-              }}
-            >
-              {pageElements.map((element: CanvasElement) => (
-                <RuntimeElement
-                  key={element.id}
-                  element={element}
-                  onClick={() => handleElementClick(element)}
-                  resolveUrl={resolveUrlWithBlob}
-                  onGalleryCardClick={(cardIndex) =>
-                    handleGalleryCardClick(element, cardIndex)
-                  }
+            {pageSwitch.previousBgVideoUrl &&
+              (isFadingIn ||
+                (pageSwitch.isSwitching && !pageSwitch.isNewBgReady)) && (
+                <video
+                  className={`absolute inset-0 h-full w-full object-contain pointer-events-none z-0 ${isFadingIn ? 'animate-crossfade-out' : ''}`}
+                  src={pageSwitch.previousBgVideoUrl}
+                  autoPlay
+                  loop
+                  muted
+                  playsInline
                />
-              ))}
+              )}
+
+            {/* New page content wrapper - fades in for non-transition navigation.
+                z-1 ensures it's above previous backgrounds (z-0) during fade.
+                onAnimationEnd resets isFadingIn when CSS animation completes. */}
+            <div
+              data-testid='page-content-wrapper'
+              className={`absolute inset-0 z-1 ${isFadingIn ? 'animate-crossfade-in' : ''}`}
+              onAnimationEnd={onFadeInAnimationEnd}
+            >
+              {/* Background image element - z-1 keeps it below backdrop blur (z-5).
+              CSS backgroundImage provides instant display.
+              Use native img for blob URLs to prevent repeated fetch requests from Next.js Image. */}
+              {backgroundImageUrl && !backgroundVideoUrl && (
+                <div className='absolute inset-0 z-1 pointer-events-none'>
+                  {backgroundImageUrl.startsWith('blob:') ? (
+                    // eslint-disable-next-line @next/next/no-img-element
+                    <img
+                      key={backgroundImageUrl}
+                      src={backgroundImageUrl}
+                      alt=''
+                      className='absolute inset-0 w-full h-full object-contain'
+                      onLoad={() => {
+                        setIsBackgroundReady(true);
+                        pageSwitch.markBackgroundReady();
+                      }}
+                      onError={() => {
+                        setIsBackgroundReady(true);
+                        pageSwitch.markBackgroundReady();
+                      }}
+                    />
+                  ) : (
+                    <Image
+                      key={backgroundImageUrl}
+                      src={backgroundImageUrl}
+                      alt=''
+                      fill
+                      sizes='100vw'
+                      className='object-contain'
+                      priority
+                      unoptimized
+                      onLoad={() => {
+                        setIsBackgroundReady(true);
+                        pageSwitch.markBackgroundReady();
+                      }}
+                      onError={() => {
+                        setIsBackgroundReady(true);
+                        pageSwitch.markBackgroundReady();
+                      }}
+                    />
+                  )}
+                </div>
+              )}
+
+              {/* Background video - z-1 keeps it below backdrop blur (z-5) */}
+              {backgroundVideoUrl && (
+                <video
+                  ref={bgVideoRef}
+                  key={backgroundVideoUrl}
+                  className='absolute inset-0 z-1 h-full w-full object-contain'
+                  src={backgroundVideoUrl}
+                  autoPlay={videoAutoplay}
+                  loop={useNativeLoop}
+                  muted={videoMuted}
+                  playsInline
+                />
+              )}
+
+              {/* Page elements - z-40 ensures they appear above carousel background (z-10) and carousel controls (z-30) */}
+              <div className='absolute inset-0 z-40'>
+                {pageElements.map((element: CanvasElement) => (
+                  <RuntimeElement
+                    key={element.id}
+                    element={element}
+                    onClick={() => handleElementClick(element)}
+                    resolveUrl={resolveUrlWithBlob}
+                    onGalleryCardClick={(cardIndex) =>
+                      handleGalleryCardClick(element, cardIndex)
+                    }
+                  />
+                ))}
+              </div>
            </div>
+            {/* End new page content wrapper */}

            {/* Controls: Offline toggle and Fullscreen button */}
            <div className='absolute top-4 right-4 z-50 flex items-center gap-2'>
@ -661,24 +679,13 @@ export default function RuntimePresentation({
            {/* Opacity is 0 during 'preparing' phase to show old page while video loads */}
            {/* Also fades to 0 when isOverlayFadingOut to reveal the new page underneath */}
            {transitionPreview && (
-              <div className='fixed inset-0 z-50 overflow-hidden pointer-events-none'>
-                <video
-                  ref={transitionVideoRef}
-                  className='absolute inset-0 h-full w-full object-cover transition-opacity duration-300 ease-linear'
-                  style={{
-                    opacity:
-                      transitionPhase === 'preparing' ||
-                      isBuffering ||
-                      isOverlayFadingOut
-                        ? 0
-                        : 1,
-                  }}
-                  muted
-                  playsInline
-                  preload='auto'
-                  disablePictureInPicture
-                />
-              </div>
+              <TransitionPreviewOverlay
+                videoRef={transitionVideoRef}
+                isActive={true}
+                isBuffering={transitionPhase === 'preparing' || isBuffering}
+                letterboxStyles={letterboxStyles}
+                opacity={isOverlayFadingOut ? 0 : 1}
+              />
            )}

            {/* Gallery Carousel Overlay */}
--- a/frontend/src/config/canvas.config.ts
+++ b/frontend/src/config/canvas.config.ts
@ -43,16 +43,16 @@ export const CANVAS_CONFIG = {

  // Page transition effects
  pageTransition: {
-    /**
-     * Fade-in duration for non-transition navigation (ms).
-     * Applied when switching pages without a transition video.
-     */
-    fadeInDurationMs: 500,
    /**
     * Fade-out duration for transition video overlay (ms).
     * Applied after transition video finishes playing.
     */
    fadeOutDurationMs: 300,
+    /**
+     * Crossfade animation duration for page backgrounds (ms).
+     * Used for smooth transitions between pages.
+     */
+    crossfadeDurationMs: 300,
    /**
     * CSS easing function for fade animations.
     */
--- a/frontend/src/config/preload.config.ts
+++ b/frontend/src/config/preload.config.ts
@ -56,15 +56,6 @@ export const PRELOAD_CONFIG = {
    constructorMaxDepth: 1, // Same as maxDepth for constructor preview
  },

-  // Reverse playback settings
-  reversePlayback: {
-    defaultFps: 25, // FPS for non-preloaded videos
-    preloadedFps: 45, // FPS for preloaded videos (blob URLs)
-    minFps: 15, // Minimum adaptive FPS
-    maxConsecutiveSlowFrames: 3, // Frames before reducing FPS
-    slowFrameThreshold: 1.3, // Multiplier of target frame time
-  },
-
  // Partial preload settings (online mode only)
  // Download only first N bytes of videos/audio for faster Phase 1 completion
  // Playback uses presigned URL directly (browser handles remaining buffering)
--- a/frontend/src/css/main.css
+++ b/frontend/src/css/main.css
@ -34,68 +34,214 @@
  @apply bg-transparent border border-blue-600 text-blue-600 !important;
 }

-/* Element appear animation keyframes */
-@keyframes element-fade-in {
+/* Page crossfade animation keyframes - Safari optimized */
+@-webkit-keyframes page-crossfade-in {
  from {
    opacity: 0;
+    -webkit-transform: translate3d(0, 0, 0);
+    transform: translate3d(0, 0, 0);
  }
  to {
    opacity: 1;
+    -webkit-transform: translate3d(0, 0, 0);
+    transform: translate3d(0, 0, 0);
+  }
+}
+
+@keyframes page-crossfade-in {
+  from {
+    opacity: 0;
+    transform: translate3d(0, 0, 0);
+  }
+  to {
+    opacity: 1;
+    transform: translate3d(0, 0, 0);
+  }
+}
+
+@-webkit-keyframes page-crossfade-out {
+  from {
+    opacity: 1;
+    -webkit-transform: translate3d(0, 0, 0);
+    transform: translate3d(0, 0, 0);
+  }
+  to {
+    opacity: 0;
+    -webkit-transform: translate3d(0, 0, 0);
+    transform: translate3d(0, 0, 0);
+  }
+}
+
+@keyframes page-crossfade-out {
+  from {
+    opacity: 1;
+    transform: translate3d(0, 0, 0);
+  }
+  to {
+    opacity: 0;
+    transform: translate3d(0, 0, 0);
+  }
+}
+
+/* Crossfade animation classes - GPU accelerated for Safari */
+.animate-crossfade-in {
+  -webkit-animation: page-crossfade-in 300ms ease-out forwards;
+  animation: page-crossfade-in 300ms ease-out forwards;
+  -webkit-backface-visibility: hidden;
+  backface-visibility: hidden;
+  will-change: opacity, transform;
+}
+
+.animate-crossfade-out {
+  -webkit-animation: page-crossfade-out 300ms ease-out forwards;
+  animation: page-crossfade-out 300ms ease-out forwards;
+  -webkit-backface-visibility: hidden;
+  backface-visibility: hidden;
+  will-change: opacity, transform;
+}
+
+/* Element appear animation keyframes - Safari optimized */
+@-webkit-keyframes element-fade-in {
+  from {
+    opacity: 0;
+    -webkit-transform: translate3d(0, 0, 0);
+    transform: translate3d(0, 0, 0);
+  }
+  to {
+    opacity: 1;
+    -webkit-transform: translate3d(0, 0, 0);
+    transform: translate3d(0, 0, 0);
+  }
+}
+
+@keyframes element-fade-in {
+  from {
+    opacity: 0;
+    transform: translate3d(0, 0, 0);
+  }
+  to {
+    opacity: 1;
+    transform: translate3d(0, 0, 0);
+  }
+}
+
+@-webkit-keyframes element-slide-up {
+  from {
+    opacity: 0;
+    -webkit-transform: translate3d(0, 20px, 0);
+    transform: translate3d(0, 20px, 0);
+  }
+  to {
+    opacity: 1;
+    -webkit-transform: translate3d(0, 0, 0);
+    transform: translate3d(0, 0, 0);
  }
 }

@keyframes element-slide-up {
  from {
    opacity: 0;
-    transform: translateY(20px);
+    transform: translate3d(0, 20px, 0);
  }
  to {
    opacity: 1;
-    transform: translateY(0);
+    transform: translate3d(0, 0, 0);
+  }
+}
+
+@-webkit-keyframes element-slide-down {
+  from {
+    opacity: 0;
+    -webkit-transform: translate3d(0, -20px, 0);
+    transform: translate3d(0, -20px, 0);
+  }
+  to {
+    opacity: 1;
+    -webkit-transform: translate3d(0, 0, 0);
+    transform: translate3d(0, 0, 0);
  }
 }

@keyframes element-slide-down {
  from {
    opacity: 0;
-    transform: translateY(-20px);
+    transform: translate3d(0, -20px, 0);
  }
  to {
    opacity: 1;
-    transform: translateY(0);
+    transform: translate3d(0, 0, 0);
+  }
+}
+
+@-webkit-keyframes element-slide-left {
+  from {
+    opacity: 0;
+    -webkit-transform: translate3d(20px, 0, 0);
+    transform: translate3d(20px, 0, 0);
+  }
+  to {
+    opacity: 1;
+    -webkit-transform: translate3d(0, 0, 0);
+    transform: translate3d(0, 0, 0);
  }
 }

@keyframes element-slide-left {
  from {
    opacity: 0;
-    transform: translateX(20px);
+    transform: translate3d(20px, 0, 0);
  }
  to {
    opacity: 1;
-    transform: translateX(0);
+    transform: translate3d(0, 0, 0);
+  }
+}
+
+@-webkit-keyframes element-slide-right {
+  from {
+    opacity: 0;
+    -webkit-transform: translate3d(-20px, 0, 0);
+    transform: translate3d(-20px, 0, 0);
+  }
+  to {
+    opacity: 1;
+    -webkit-transform: translate3d(0, 0, 0);
+    transform: translate3d(0, 0, 0);
  }
 }

@keyframes element-slide-right {
  from {
    opacity: 0;
-    transform: translateX(-20px);
+    transform: translate3d(-20px, 0, 0);
  }
  to {
    opacity: 1;
-    transform: translateX(0);
+    transform: translate3d(0, 0, 0);
+  }
+}
+
+@-webkit-keyframes element-scale-in {
+  from {
+    opacity: 0;
+    -webkit-transform: scale3d(0.8, 0.8, 1);
+    transform: scale3d(0.8, 0.8, 1);
+  }
+  to {
+    opacity: 1;
+    -webkit-transform: scale3d(1, 1, 1);
+    transform: scale3d(1, 1, 1);
  }
 }

@keyframes element-scale-in {
  from {
    opacity: 0;
-    transform: scale(0.8);
+    transform: scale3d(0.8, 0.8, 1);
  }
  to {
    opacity: 1;
-    transform: scale(1);
+    transform: scale3d(1, 1, 1);
  }
 }

--- a/frontend/src/hooks/useBackgroundTransition.ts
+++ b/frontend/src/hooks/useBackgroundTransition.ts
@ -14,19 +14,20 @@
 * 2. Simple mode (constructor): Direct navigation clearing + optional fade-in
 */

-import { useEffect, useState, useCallback, useRef } from 'react';
+import {
+  useEffect,
+  useLayoutEffect,
+  useState,
+  useCallback,
+  useRef,
+} from 'react';
 import { CANVAS_CONFIG } from '../config/canvas.config';

 /**
- * Fade-out duration from config
+ * Fade-out duration from config (for transition video overlay)
 */
 const FADE_OUT_DURATION_MS = CANVAS_CONFIG.pageTransition.fadeOutDurationMs;

-/**
- * Fade-in duration from config
- */
-const FADE_IN_DURATION_MS = CANVAS_CONFIG.pageTransition.fadeInDurationMs;
-
 /**
 * Fade-out configuration (optional - for RuntimePresentation)
 */
@ -47,8 +48,6 @@ export interface FadeOutConfig {
 export interface FadeInConfig {
  /** Whether a transition video is currently active (disables fade-in) */
  hasActiveTransition: boolean;
-  /** Optional duration override (uses config default if not provided) */
-  durationMs?: number;
 }

 export interface UseBackgroundTransitionOptions {
@ -58,6 +57,7 @@ export interface UseBackgroundTransitionOptions {
    isSwitching: boolean;
    isNewBgReady: boolean;
    previousBgImageUrl: string;
+    previousBgVideoUrl: string;
  };
  /** Optional fade-out configuration (for RuntimePresentation) */
  fadeOut?: FadeOutConfig;
@ -70,11 +70,11 @@ export interface UseBackgroundTransitionResult {
  isOverlayFadingOut: boolean;
  /** Reset the fade-out state (call before starting a new transition) */
  resetFadeOut: () => void;
-  /** Whether page content is currently fading in */
+  /** Whether page content is currently fading (crossfade in progress) */
  isFadingIn: boolean;
-  /** Opacity value for elements container (0 during fade, 1 when complete) */
-  elementsOpacity: number;
-  /** Reset fade-in state before starting new navigation */
+  /** Handler to call when fade-in animation ends (pass to onAnimationEnd) */
+  onFadeInAnimationEnd: () => void;
+  /** Reset fade-in state (for cleanup or cancellation) */
  resetFadeIn: () => void;
 }

@ -83,7 +83,7 @@ export interface UseBackgroundTransitionResult {
 *
 * @example
 * // Full mode with fade-out and fade-in (RuntimePresentation)
- * const { isOverlayFadingOut, resetFadeOut, isFadingIn, elementsOpacity, resetFadeIn } = useBackgroundTransition({
+ * const { isOverlayFadingOut, resetFadeOut, isFadingIn, onFadeInAnimationEnd } = useBackgroundTransition({
 *   pageSwitch,
 *   fadeOut: {
 *     pendingTransitionComplete,
@ -99,6 +99,12 @@ export interface UseBackgroundTransitionResult {
 *   },
 * });
 *
+ * // In JSX:
+ * <div
+ *   className={isFadingIn ? 'animate-crossfade-in' : ''}
+ *   onAnimationEnd={onFadeInAnimationEnd}
+ * >
+ *
 * @example
 * // Simple mode - direct navigation only (constructor)
 * useBackgroundTransition({ pageSwitch });
@ -109,15 +115,10 @@ export function useBackgroundTransition({
  fadeIn,
 }: UseBackgroundTransitionOptions): UseBackgroundTransitionResult {
  const [isOverlayFadingOut, setIsOverlayFadingOut] = useState(false);
-
-  // Fade-in state
  const [isFadingIn, setIsFadingIn] = useState(false);
-  const [elementsOpacity, setElementsOpacity] = useState(1);

  // Track previous isSwitching state to detect transition start
  const wasSwitchingRef = useRef(false);
-  // Track timer for cleanup
-  const fadeInTimerRef = useRef<ReturnType<typeof setTimeout> | null>(null);

  /**
   * Reset fade-out state before starting a new transition.
@ -128,16 +129,18 @@ export function useBackgroundTransition({
  }, []);

  /**
-   * Reset fade-in state before starting new navigation.
-   * Clears any in-progress fade animation.
+   * Reset fade-in state (for cleanup or cancellation).
   */
  const resetFadeIn = useCallback(() => {
-    if (fadeInTimerRef.current) {
-      clearTimeout(fadeInTimerRef.current);
-      fadeInTimerRef.current = null;
-    }
    setIsFadingIn(false);
-    setElementsOpacity(1);
+  }, []);
+
+  /**
+   * Handler for onAnimationEnd event.
+   * Called when CSS animation completes - CSS is the source of truth for duration.
+   */
+  const onFadeInAnimationEnd = useCallback(() => {
+    setIsFadingIn(false);
  }, []);

  /**
@ -187,92 +190,55 @@ export function useBackgroundTransition({
  }, [fadeOut, isOverlayFadingOut, pageSwitch]);

  /**
-   * Effect: Clear previous background overlay when new background is ready (direct navigation).
+   * Effect: Clear previous background overlay after fade completes (direct navigation).
   *
-   * This handles the case when navigating without a transition video.
-   * The previous background stays visible until the new one is ready to paint.
+   * The previous background stays visible during the entire fade animation,
+   * providing a smooth crossfade effect. Only cleared after fade ends.
   */
  useEffect(() => {
-    if (
-      pageSwitch.isSwitching &&
-      pageSwitch.isNewBgReady &&
-      pageSwitch.previousBgImageUrl
-    ) {
-      // New background is ready - clear the previous background overlay
+    if (pageSwitch.isSwitching && pageSwitch.isNewBgReady && !isFadingIn) {
+      // Fade is complete - clear the previous background overlay
+      // This also resets isSwitching state so next navigation triggers fade-in
      pageSwitch.clearPreviousBackground();
    }
  }, [
    pageSwitch.isSwitching,
    pageSwitch.isNewBgReady,
-    pageSwitch.previousBgImageUrl,
    pageSwitch.clearPreviousBackground,
+    isFadingIn,
  ]);

  /**
-   * Effect: Fade-in page content on non-transition navigation.
+   * Layout effect: Set up crossfade BEFORE browser paints when switching starts.
+   * useLayoutEffect runs synchronously after DOM mutations but before paint,
+   * preventing any flash of new content at full opacity.
   *
-   * Trigger: pageSwitch.isSwitching becomes true AND no active transition
-   *
-   * Sequence:
-   * 1. Navigation starts (isSwitching: false → true)
-   * 2. No transition video active
-   * 3. Set elementsOpacity = 0
-   * 4. Use double RAF to ensure paint before animation
-   * 5. Set elementsOpacity = 1 (CSS animates)
-   * 6. After duration, set isFadingIn = false
+   * IMPORTANT: Skip this for transitions - transition video IS the effect.
   */
-  useEffect(() => {
+  useLayoutEffect(() => {
    if (!fadeIn) {
      wasSwitchingRef.current = pageSwitch.isSwitching;
      return;
    }

-    const { hasActiveTransition, durationMs = FADE_IN_DURATION_MS } = fadeIn;
+    const { hasActiveTransition } = fadeIn;
    const justStartedSwitching =
      pageSwitch.isSwitching && !wasSwitchingRef.current;
+
    wasSwitchingRef.current = pageSwitch.isSwitching;

-    // Start fade-in when:
-    // - Just started switching (transition from false to true)
-    // - No active transition video
+    // Only start crossfade for NON-transition navigation
+    // Transitions use video overlay - no fade needed
    if (justStartedSwitching && !hasActiveTransition) {
      setIsFadingIn(true);
-      setElementsOpacity(0);
-
-      // Double RAF ensures opacity:0 is painted before transition starts
-      // (Same pattern as usePageSwitch.ts:396-397)
-      requestAnimationFrame(() => {
-        requestAnimationFrame(() => {
-          setElementsOpacity(1);
-        });
-      });
-
-      // Clear any existing timer
-      if (fadeInTimerRef.current) {
-        clearTimeout(fadeInTimerRef.current);
-      }
-
-      // Mark fade as complete after duration
-      fadeInTimerRef.current = setTimeout(() => {
-        setIsFadingIn(false);
-        fadeInTimerRef.current = null;
-      }, durationMs);
    }
-
-    // Cleanup on unmount
-    return () => {
-      if (fadeInTimerRef.current) {
-        clearTimeout(fadeInTimerRef.current);
-        fadeInTimerRef.current = null;
-      }
-    };
  }, [pageSwitch.isSwitching, fadeIn]);

  return {
    isOverlayFadingOut,
    resetFadeOut,
    isFadingIn,
-    elementsOpacity,
+    onFadeInAnimationEnd,
    resetFadeIn,
  };
 }
--- a/frontend/src/hooks/usePageSwitch.ts
+++ b/frontend/src/hooks/usePageSwitch.ts
@ -21,6 +21,7 @@ import {
  buildProxyUrl,
 } from '../lib/assetUrl';
 import { logger } from '../lib/logger';
+import { scheduleAfterPaint } from '../lib/browserUtils';

 /**
 * Minimal page interface for page switching
@ -63,6 +64,8 @@ export interface UsePageSwitchResult {
  currentBgAudioUrl: string;
  /** Previous background image URL (for overlay) */
  previousBgImageUrl: string;
+  /** Previous background video URL (for overlay during fade) */
+  previousBgVideoUrl: string;
  /** Whether we're in the middle of a page switch */
  isSwitching: boolean;
  /** Whether the new background is ready to display */
@ -198,9 +201,14 @@ export function usePageSwitch(
  const previousBgImageUrlRef = useRef('');
  previousBgImageUrlRef.current = previousBgImageUrl;

+  const [previousBgVideoUrl, setPreviousBgVideoUrl] = useState('');
+  const previousBgVideoUrlRef = useRef('');
+  previousBgVideoUrlRef.current = previousBgVideoUrl;
+
  // Transition state
  const [isSwitching, setIsSwitching] = useState(false);
-  const [isNewBgReady, setIsNewBgReady] = useState(true);
+  // Initialize as false to trigger fade-in animation on initial page load
+  const [isNewBgReady, setIsNewBgReady] = useState(false);

  // Track blob URLs we created so we can revoke them
  const createdBlobUrlsRef = useRef<Set<string>>(new Set());
@ -362,16 +370,20 @@ export function usePageSwitch(
        setCurrentBgVideoUrl('');
        setCurrentBgAudioUrl('');
        setPreviousBgImageUrl('');
+        setPreviousBgVideoUrl('');
        setIsSwitching(false);
        setIsNewBgReady(true);
        onSwitched?.();
        return;
      }

-      // Save current image as previous for overlay (use ref to avoid dependency)
+      // Save current backgrounds as previous for overlay (use refs to avoid dependencies)
      if (currentBgImageUrlRef.current) {
        setPreviousBgImageUrl(currentBgImageUrlRef.current);
      }
+      if (currentBgVideoUrlRef.current) {
+        setPreviousBgVideoUrl(currentBgVideoUrlRef.current);
+      }

      setIsSwitching(true);
      setIsNewBgReady(false);
@ -391,12 +403,10 @@ export function usePageSwitch(
      // Notify caller that backgrounds are set
      onSwitched?.();

-      // For blob URLs, mark ready immediately (local data)
+      // For blob URLs, mark ready after paint (Safari-compatible)
      if (imageUrl.startsWith('blob:') || !imageUrl) {
-        requestAnimationFrame(() => {
-          requestAnimationFrame(() => {
-            setIsNewBgReady(true);
-          });
+        scheduleAfterPaint(() => {
+          setIsNewBgReady(true);
        });
      }
      // For remote images, wait for Image onLoad (caller should use markBackgroundReady)
@ -405,7 +415,8 @@ export function usePageSwitch(
  );

  /**
-   * Directly set backgrounds without transition overlay
+   * Directly set backgrounds without transition overlay.
+   * Used for initial page load with fade-in animation.
   */
  const setBackgroundsDirectly = useCallback(
    (imageUrl: string, videoUrl: string, audioUrl: string) => {
@ -420,7 +431,13 @@ export function usePageSwitch(
      setCurrentBgAudioUrl(audioUrl);
      setPreviousBgImageUrl('');
      setIsSwitching(false);
-      setIsNewBgReady(true);
+
+      // Trigger fade-in animation: set not-ready then ready after paint
+      // This ensures the CSS animation triggers on initial page load
+      setIsNewBgReady(false);
+      scheduleAfterPaint(() => {
+        setIsNewBgReady(true);
+      });
    },
    [revokeBlobUrl],
  );
@ -433,16 +450,21 @@ export function usePageSwitch(
  }, []);

  /**
-   * Clear the previous background overlay
+   * Clear the previous background overlay (both image and video)
   */
  const clearPreviousBackground = useCallback(() => {
-    const prevUrl = previousBgImageUrlRef.current;
+    const prevImageUrl = previousBgImageUrlRef.current;
+    const prevVideoUrl = previousBgVideoUrlRef.current;
    setPreviousBgImageUrl('');
+    setPreviousBgVideoUrl('');
    setIsSwitching(false);

-    // Revoke the previous blob URL after clearing
-    if (prevUrl) {
-      revokeBlobUrl(prevUrl);
+    // Revoke the previous blob URLs after clearing
+    if (prevImageUrl) {
+      revokeBlobUrl(prevImageUrl);
+    }
+    if (prevVideoUrl) {
+      revokeBlobUrl(prevVideoUrl);
    }
  }, [revokeBlobUrl]);

@ -451,6 +473,7 @@ export function usePageSwitch(
    currentBgVideoUrl,
    currentBgAudioUrl,
    previousBgImageUrl,
+    previousBgVideoUrl,
    isSwitching,
    isNewBgReady,
    switchToPage,
--- a/frontend/src/hooks/useReversePlayback.ts
+++ b/frontend/src/hooks/useReversePlayback.ts
@ -1,516 +0,0 @@
-import {
-  useCallback,
-  useEffect,
-  useMemo,
-  useRef,
-  useState,
-  type RefObject,
-} from 'react';
-import { logger } from '../lib/logger';
-import { PRELOAD_CONFIG } from '../config/preload.config';
-
-interface UseReversePlaybackOptions {
-  videoRef: RefObject<HTMLVideoElement | null>;
-  onComplete: () => void;
-  preloadedUrls?: Set<string>;
-  videoUrl?: string;
-  storageKey?: string; // Raw storage path for preload detection
-  getCachedBlobUrl?: (url: string) => Promise<string | null>;
-  getReadyBlobUrl?: (url: string) => string | null; // O(1) instant lookup
-}
-
-// Note: requestVideoFrameCallback exists but only works during playback.
-// For reverse frame-stepping (paused video), we use requestAnimationFrame + seeked events.
-
-interface UseReversePlaybackResult {
-  startReverse: () => Promise<void>;
-  stopReverse: () => void;
-  isReversing: boolean;
-  isBuffering: boolean;
-  canUseNativeReverse: boolean;
-}
-
-function checkNativeReverseSupport(): boolean {
-  if (typeof window === 'undefined') return false;
-  try {
-    const video = document.createElement('video');
-    video.playbackRate = -1;
-    return video.playbackRate === -1;
-  } catch {
-    return false;
-  }
-}
-
-async function startNativeReverse(
-  video: HTMLVideoElement,
-  duration: number,
-  onComplete: () => void,
-  didFinishRef: { current: boolean },
-): Promise<boolean> {
-  return new Promise((resolve) => {
-    video.currentTime = duration;
-    video.playbackRate = -1;
-
-    const cleanup = () => {
-      video.removeEventListener('timeupdate', onTimeUpdate);
-      video.playbackRate = 1;
-    };
-
-    const onTimeUpdate = () => {
-      if (didFinishRef.current) {
-        cleanup();
-        resolve(true);
-        return;
-      }
-      if (video.currentTime <= 0.05) {
-        cleanup();
-        video.pause();
-        video.currentTime = 0;
-        onComplete();
-        resolve(true);
-      }
-    };
-
-    video.addEventListener('timeupdate', onTimeUpdate);
-
-    video.play().catch((err) => {
-      logger.error('Native reverse play failed:', err);
-      cleanup();
-      resolve(false);
-    });
-  });
-}
-
-function getBufferedEnd(video: HTMLVideoElement): number {
-  return video.buffered.length > 0
-    ? video.buffered.end(video.buffered.length - 1)
-    : 0;
-}
-
-export function useReversePlayback(
-  options: UseReversePlaybackOptions,
-): UseReversePlaybackResult {
-  const [isReversing, setIsReversing] = useState(false);
-  const [isBuffering, setIsBuffering] = useState(false);
-  const animationFrameRef = useRef<number | null>(null);
-  const didFinishRef = useRef(false);
-  const cleanupFnsRef = useRef<Array<() => void>>([]);
-  const metricsRef = useRef<{
-    consecutiveSlowFrames: number;
-    currentFps: number;
-    lastSeekDuration: number;
-  }>({
-    consecutiveSlowFrames: 0,
-    currentFps: PRELOAD_CONFIG.reversePlayback.defaultFps,
-    lastSeekDuration: 0,
-  });
-
-  const canUseNativeReverse = useMemo(() => checkNativeReverseSupport(), []);
-
-  const cleanup = useCallback(() => {
-    didFinishRef.current = true;
-    if (animationFrameRef.current !== null) {
-      cancelAnimationFrame(animationFrameRef.current);
-      animationFrameRef.current = null;
-    }
-    cleanupFnsRef.current.forEach((fn) => fn());
-    cleanupFnsRef.current = [];
-    const video = options.videoRef.current;
-    if (video && video.playbackRate !== 1) {
-      video.playbackRate = 1;
-    }
-  }, [options.videoRef]);
-
-  const stopReverse = useCallback(() => {
-    cleanup();
-    setIsReversing(false);
-    setIsBuffering(false);
-  }, [cleanup]);
-
-  const startReverse = useCallback(async () => {
-    const video = options.videoRef.current;
-    if (!video) return;
-
-    stopReverse();
-    didFinishRef.current = false;
-    setIsReversing(true);
-
-    const {
-      onComplete,
-      preloadedUrls,
-      videoUrl,
-      storageKey,
-      getCachedBlobUrl,
-      getReadyBlobUrl,
-    } = options;
-
-    const actualDuration = video.duration;
-    if (!Number.isFinite(actualDuration) || actualDuration <= 0) {
-      logger.error('Invalid video duration for reverse playback', {
-        videoDuration: video.duration,
-        readyState: video.readyState,
-        videoUrl,
-      });
-      setIsReversing(false);
-      onComplete();
-      return;
-    }
-
-    const finishReverse = (reason: string) => {
-      if (didFinishRef.current) return;
-      didFinishRef.current = true;
-      cleanup();
-      setIsReversing(false);
-      setIsBuffering(false);
-      logger.info('Reverse playback finished', { reason });
-      onComplete();
-    };
-
-    // Strategy 1: Native playbackRate = -1
-    if (canUseNativeReverse) {
-      logger.info('Using native playbackRate = -1');
-      const success = await startNativeReverse(
-        video,
-        actualDuration,
-        () => finishReverse('native-complete'),
-        didFinishRef,
-      );
-      if (success) return;
-      logger.info('Native reverse failed, falling back to frame-stepping');
-    }
-
-    // Check if video is preloaded (use storageKey for accurate detection)
-    const isPreloaded = storageKey
-      ? preloadedUrls?.has(storageKey)
-      : videoUrl && preloadedUrls?.has(videoUrl);
-
-    // Reset adaptive FPS metrics
-    const config = PRELOAD_CONFIG.reversePlayback;
-    metricsRef.current = {
-      consecutiveSlowFrames: 0,
-      currentFps: isPreloaded ? config.preloadedFps : config.defaultFps,
-      lastSeekDuration: 0,
-    };
-
-    // Try O(1) instant lookup first (uses downloadManager.readyBlobUrls)
-    if (getReadyBlobUrl && videoUrl && !video.src.startsWith('blob:')) {
-      const readyBlobUrl = getReadyBlobUrl(videoUrl);
-      if (readyBlobUrl && !didFinishRef.current) {
-        logger.info('Using ready blob URL for reverse (O(1) lookup)', {
-          videoUrl: videoUrl.slice(-50),
-        });
-        video.src = readyBlobUrl;
-        video.load();
-        await new Promise<void>((resolve) => {
-          const onLoaded = () => {
-            video.removeEventListener('loadeddata', onLoaded);
-            // Immediately seek to end to avoid showing first frame
-            if (video.duration && Number.isFinite(video.duration)) {
-              video.currentTime = video.duration - 0.01;
-            }
-            resolve();
-          };
-          video.addEventListener('loadeddata', onLoaded);
-          setTimeout(resolve, 1000); // Shorter timeout for ready URLs
-        });
-      }
-    }
-
-    // Fall back to async cache lookup
-    if (getCachedBlobUrl && videoUrl && !video.src.startsWith('blob:')) {
-      try {
-        const blobUrl = await getCachedBlobUrl(videoUrl);
-        if (blobUrl && !didFinishRef.current) {
-          logger.info('Using cached blob URL for reverse');
-          video.src = blobUrl;
-          video.load();
-          await new Promise<void>((resolve) => {
-            const onLoaded = () => {
-              video.removeEventListener('loadeddata', onLoaded);
-              // Immediately seek to end to avoid showing first frame
-              if (video.duration && Number.isFinite(video.duration)) {
-                video.currentTime = video.duration - 0.01;
-              }
-              resolve();
-            };
-            video.addEventListener('loadeddata', onLoaded);
-            setTimeout(resolve, 2000);
-          });
-        }
-      } catch (err) {
-        logger.warn('Failed to get cached blob URL', { err });
-      }
-    }
-
-    const startFrameStepping = (targetTime: number) => {
-      const maxBuffered = getBufferedEnd(video);
-      const safeTarget = Math.min(targetTime, maxBuffered);
-
-      logger.info('Preparing reverse seek', {
-        requestedTarget: targetTime,
-        maxBuffered,
-        safeTarget,
-        readyState: video.readyState,
-      });
-
-      if (safeTarget < 0.1) {
-        logger.info('No buffered range available');
-        finishReverse('no-buffered');
-        return;
-      }
-
-      const beginFrameStepping = () => {
-        video.pause();
-        let isWaitingForSeek = false;
-        let lastStepTime = performance.now();
-        let stepCount = 0;
-
-        const onSeekedFrame = () => {
-          if (didFinishRef.current) return;
-
-          // Measure seek performance for adaptive FPS
-          const now = performance.now();
-          const seekDuration = now - lastStepTime;
-          const targetFrameMs = 1000 / metricsRef.current.currentFps;
-
-          if (seekDuration > targetFrameMs * config.slowFrameThreshold) {
-            metricsRef.current.consecutiveSlowFrames++;
-            if (
-              metricsRef.current.consecutiveSlowFrames >=
-              config.maxConsecutiveSlowFrames
-            ) {
-              metricsRef.current.currentFps = Math.max(
-                config.minFps,
-                metricsRef.current.currentFps - 5,
-              );
-              metricsRef.current.consecutiveSlowFrames = 0;
-              logger.info('Adaptive FPS reduced', {
-                newFps: metricsRef.current.currentFps,
-                seekDuration,
-              });
-            }
-          } else {
-            metricsRef.current.consecutiveSlowFrames = 0;
-          }
-
-          isWaitingForSeek = false;
-          scheduleNextStep();
-        };
-
-        const scheduleNextStep = () => {
-          if (didFinishRef.current) return;
-          animationFrameRef.current = requestAnimationFrame(step);
-        };
-
-        // Throttled step - only executes when enough time has passed
-        const step = () => {
-          if (didFinishRef.current || isWaitingForSeek) return;
-
-          // Check if enough time has passed for next frame
-          const now = performance.now();
-          const elapsed = now - lastStepTime;
-          const targetFrameMs = 1000 / metricsRef.current.currentFps;
-
-          if (elapsed < targetFrameMs) {
-            // Not enough time passed, wait for next animation frame
-            animationFrameRef.current = requestAnimationFrame(step);
-            return;
-          }
-
-          stepCount++;
-          const currentStepSize = 1 / metricsRef.current.currentFps;
-          const newTime = video.currentTime - currentStepSize;
-
-          if (stepCount % 30 === 0) {
-            logger.info('Frame-stepping progress', {
-              stepCount,
-              currentTime: video.currentTime,
-              fps: metricsRef.current.currentFps,
-            });
-          }
-
-          if (newTime <= 0) {
-            video.removeEventListener('seeked', onSeekedFrame);
-            video.currentTime = 0;
-            finishReverse('reverse-complete');
-            return;
-          }
-
-          isWaitingForSeek = true;
-          lastStepTime = now;
-          video.currentTime = newTime;
-        };
-
-        video.addEventListener('seeked', onSeekedFrame);
-        cleanupFnsRef.current.push(() =>
-          video.removeEventListener('seeked', onSeekedFrame),
-        );
-
-        // Start stepping
-        step();
-      };
-
-      const onSeeked = () => {
-        video.removeEventListener('seeked', onSeeked);
-        if (didFinishRef.current) return;
-
-        if (video.currentTime < 0.1) {
-          logger.info('Seek failed, retrying');
-          const onRetry = () => {
-            video.removeEventListener('seeked', onRetry);
-            if (didFinishRef.current) return;
-            if (video.currentTime >= 0.1) {
-              beginFrameStepping();
-            } else {
-              finishReverse('seek-failed');
-            }
-          };
-          video.addEventListener('seeked', onRetry);
-          cleanupFnsRef.current.push(() =>
-            video.removeEventListener('seeked', onRetry),
-          );
-          video.currentTime = safeTarget;
-          return;
-        }
-
-        beginFrameStepping();
-      };
-
-      video.addEventListener('seeked', onSeeked);
-      cleanupFnsRef.current.push(() =>
-        video.removeEventListener('seeked', onSeeked),
-      );
-
-      if (!video.paused) {
-        const onPause = () => {
-          video.removeEventListener('pause', onPause);
-          if (didFinishRef.current) return;
-          requestAnimationFrame(() => {
-            if (!didFinishRef.current) {
-              video.currentTime = safeTarget;
-            }
-          });
-        };
-        video.addEventListener('pause', onPause);
-        cleanupFnsRef.current.push(() =>
-          video.removeEventListener('pause', onPause),
-        );
-        video.pause();
-      } else {
-        // Skip initial seek if already near target position (within 0.2s)
-        // This prevents the forward-then-backward movement flash
-        if (Math.abs(video.currentTime - safeTarget) < 0.2) {
-          logger.info('Already near target, skipping initial seek', {
-            currentTime: video.currentTime,
-            safeTarget,
-          });
-          video.removeEventListener('seeked', onSeeked);
-          beginFrameStepping();
-        } else {
-          video.currentTime = safeTarget;
-        }
-      }
-    };
-
-    const bufferedEnd = getBufferedEnd(video);
-
-    logger.info('Starting reverse playback', {
-      duration: actualDuration,
-      bufferedEnd,
-      isPreloaded,
-      readyState: video.readyState,
-    });
-
-    // If already fully buffered, start immediately
-    if (bufferedEnd >= actualDuration - 0.1) {
-      logger.info('Video fully buffered, starting immediately');
-      startFrameStepping(actualDuration);
-      return;
-    }
-
-    // Need to buffer more
-    setIsBuffering(true);
-    let progressCheckCount = 0;
-    const maxProgressChecks = 160; // ~8 seconds at 20 checks/sec
-
-    const onProgress = () => {
-      if (didFinishRef.current) return;
-      progressCheckCount++;
-      const currentBuffered = getBufferedEnd(video);
-
-      if (currentBuffered >= actualDuration - 0.1) {
-        setIsBuffering(false);
-        startFrameStepping(actualDuration);
-        return;
-      }
-
-      if (progressCheckCount >= maxProgressChecks) {
-        setIsBuffering(false);
-        if (currentBuffered >= 0.5) {
-          startFrameStepping(currentBuffered);
-        } else {
-          finishReverse('buffer-timeout');
-        }
-      }
-    };
-
-    const onCanPlayThrough = () => {
-      if (didFinishRef.current) return;
-      const currentBuffered = getBufferedEnd(video);
-      if (currentBuffered >= 0.5) {
-        setIsBuffering(false);
-        const targetTime = Math.min(currentBuffered, actualDuration);
-        startFrameStepping(targetTime);
-      }
-    };
-
-    const onEnded = () => {
-      if (didFinishRef.current) return;
-      setIsBuffering(false);
-      const currentBuffered = getBufferedEnd(video);
-      if (currentBuffered >= 0.5) {
-        startFrameStepping(currentBuffered);
-      } else {
-        startFrameStepping(actualDuration);
-      }
-    };
-
-    video.addEventListener('progress', onProgress);
-    video.addEventListener('canplaythrough', onCanPlayThrough);
-    video.addEventListener('ended', onEnded);
-    cleanupFnsRef.current.push(
-      () => video.removeEventListener('progress', onProgress),
-      () => video.removeEventListener('canplaythrough', onCanPlayThrough),
-      () => video.removeEventListener('ended', onEnded),
-    );
-
-    // Start playback to trigger buffering, but from near the end
-    // to avoid showing frame 0 (which would flash the target page)
-    video.muted = true;
-    video.currentTime = actualDuration - 0.1;
-    video.play().catch(() => undefined);
-
-    // Fallback timeout
-    const timeoutId = setTimeout(() => {
-      if (didFinishRef.current) return;
-      setIsBuffering(false);
-      const currentBuffered = getBufferedEnd(video);
-      if (currentBuffered >= 0.5) {
-        startFrameStepping(currentBuffered);
-      } else {
-        finishReverse('buffer-timeout');
-      }
-    }, 8000);
-    cleanupFnsRef.current.push(() => clearTimeout(timeoutId));
-  }, [canUseNativeReverse, options, stopReverse, cleanup]);
-
-  useEffect(() => () => stopReverse(), [stopReverse]);
-
-  return {
-    startReverse,
-    stopReverse,
-    isReversing,
-    isBuffering,
-    canUseNativeReverse,
-  };
-}
--- a/frontend/src/hooks/useTransitionPlayback.ts
+++ b/frontend/src/hooks/useTransitionPlayback.ts
@ -1,3 +1,11 @@
+/**
+ * useTransitionPlayback Hook
+ *
+ * Handles video transition playback between pages.
+ * For back navigation, uses pre-reversed video generated by the backend.
+ * No frame-stepping - all transitions play forward.
+ */
+
 import {
  useCallback,
  useEffect,
@ -17,9 +25,8 @@ import {
  extractStoragePath,
 } from '../lib/assetUrl';
 import { downloadManager } from '../lib/offline/DownloadManager';
-import { useReversePlayback } from './useReversePlayback';

-export type ReverseMode = 'none' | 'reverse' | 'separate';
+export type ReverseMode = 'none' | 'separate';

 export interface TransitionConfig {
  videoUrl: string;
@ -61,7 +68,6 @@ export type PlaybackPhase =
  | 'idle'
  | 'preparing'
  | 'playing'
-  | 'reversing'
  | 'finishing'
  | 'completed';

@ -79,19 +85,8 @@ const DEFAULT_TIMEOUTS = {
  hardTimeoutMs: 45000,
 };

-function getBufferedEnd(video: HTMLVideoElement): number {
-  return video.buffered.length > 0
-    ? video.buffered.end(video.buffered.length - 1)
-    : 0;
-}
-
-function shouldLoadViaBlob(
-  url: string,
-  reverseMode: ReverseMode,
-  useBlobUrlOption?: boolean,
-): boolean {
+function shouldLoadViaBlob(url: string, useBlobUrlOption?: boolean): boolean {
  if (useBlobUrlOption === false) return false;
-  if (reverseMode === 'reverse') return true;
  if (useBlobUrlOption === true) return true;

  try {
@ -107,13 +102,6 @@ function shouldLoadViaBlob(
  }
 }

-function buildBlobRequestUrl(url: string): string {
-  if (url.startsWith('/api/')) {
-    return url.replace(/^\/api(?=\/)/, '');
-  }
-  return url;
-}
-
 async function waitForImages(urls: string[], timeoutMs = 2000): Promise<void> {
  if (urls.length === 0) return;

@ -155,13 +143,10 @@ export function useTransitionPlayback(

  const playbackStartMs =
    customTimeouts?.playbackStartMs ?? DEFAULT_TIMEOUTS.playbackStartMs;
-  const durationBufferMs =
-    customTimeouts?.durationBufferMs ?? DEFAULT_TIMEOUTS.durationBufferMs;
  const hardTimeoutMs =
    customTimeouts?.hardTimeoutMs ?? DEFAULT_TIMEOUTS.hardTimeoutMs;

  const [phase, setPhase] = useState<PlaybackPhase>('idle');
-  const [isReverseBufferingLocal, setIsReverseBufferingLocal] = useState(false);

  const didFinishRef = useRef(false);
  const didStartPlaybackRef = useRef(false);
@ -169,6 +154,7 @@ export function useTransitionPlayback(
  const lastLoadedBlobUrlRef = useRef<string | null>(null);
  const lastLoadedSourceUrlRef = useRef<string | null>(null);
  const didTryFallbackRef = useRef(false);
+  const didTryDecodeRetryRef = useRef(false);
  const currentPlayableUrlRef = useRef<string | null>(null);
  const startWatchdogTimerRef = useRef<ReturnType<typeof setTimeout> | null>(
    null,
@ -183,14 +169,26 @@ export function useTransitionPlayback(
  const transitionRef = useRef(transition);
  const featuresRef = useRef(features);
  const preloadRef = useRef(preload);
-  const startReverseRef = useRef<(() => Promise<void>) | null>(null);
-  const stopReverseRef = useRef<(() => void) | null>(null);

+  // Determine which video URL to use:
+  // For back navigation with a reversed video, use reverseVideoUrl
+  // Otherwise, use the original videoUrl
  const sourceUrl = useMemo(() => {
    if (!transition) return '';
-    return transition.reverseMode === 'separate' && transition.reverseVideoUrl
-      ? transition.reverseVideoUrl
-      : transition.videoUrl;
+    // Use reversed video if this is back navigation with a separate reversed video
+    if (transition.isBack && transition.reverseVideoUrl) {
+      return transition.reverseVideoUrl;
+    }
+    return transition.videoUrl;
+  }, [transition]);
+
+  // Storage key for cache lookup - use reversed video key for back navigation
+  const storageKey = useMemo(() => {
+    if (!transition) return undefined;
+    if (transition.isBack && transition.reverseVideoUrl) {
+      return transition.reverseVideoUrl;
+    }
+    return transition.storageKey;
  }, [transition]);

  const clearTimers = useCallback(() => {
@ -225,7 +223,6 @@ export function useTransitionPlayback(
      if (video) {
        video.pause();
        // Seek back slightly to ensure last frame is visible
-        // Some browsers show black after 'ended' event when currentTime === duration
        if (
          video.duration &&
          Number.isFinite(video.duration) &&
@ -278,43 +275,17 @@ export function useTransitionPlayback(
    [finishPlayback],
  );

-  const handleReverseComplete = useCallback(() => {
-    finishPlayback('reverse-complete');
-  }, [finishPlayback]);
-
-  const {
-    startReverse,
-    stopReverse,
-    isReversing,
-    isBuffering: isReverseBuffering,
-  } = useReversePlayback({
-    videoRef,
-    onComplete: handleReverseComplete,
-    preloadedUrls: preload?.preloadedUrls,
-    videoUrl: sourceUrl,
-    storageKey: transition?.storageKey, // Raw storage path for preload detection
-    getCachedBlobUrl: preload?.getCachedBlobUrl,
-    getReadyBlobUrl: preload?.getReadyBlobUrl, // O(1) instant lookup
-  });
-
  useEffect(() => {
    onCompleteRef.current = onComplete;
    onErrorRef.current = onError;
    transitionRef.current = transition;
    featuresRef.current = features;
    preloadRef.current = preload;
-    startReverseRef.current = startReverse;
-    stopReverseRef.current = stopReverse;
  });

-  useEffect(() => {
-    setIsReverseBufferingLocal(isReverseBuffering);
-  }, [isReverseBuffering]);
-
  const cancel = useCallback(() => {
    if (phase === 'idle') return;
    clearTimers();
-    stopReverseRef.current?.();
    didFinishRef.current = true;
    setPhase('idle');
    const video = videoRef.current;
@ -337,12 +308,12 @@ export function useTransitionPlayback(
      return;
    }

-    // Include reverseMode in the key so same video can play forward then reverse
-    const sourceKey = `${sourceUrl}|${currentTransition.reverseMode}`;
+    // Include isBack in the key so same video can play forward or as reversed
+    const sourceKey = `${sourceUrl}|${currentTransition.isBack ? 'back' : 'forward'}`;
    if (activeSourceUrlRef.current === sourceKey) {
      logger.info('Skipping duplicate effect for same source', {
        sourceUrl,
-        reverseMode: currentTransition.reverseMode,
+        isBack: currentTransition.isBack,
      });
      return;
    }
@ -351,10 +322,10 @@ export function useTransitionPlayback(
    didFinishRef.current = false;
    didStartPlaybackRef.current = false;
    didTryFallbackRef.current = false;
+    didTryDecodeRetryRef.current = false;
    currentPlayableUrlRef.current = null;
    setPhase('preparing');

-    const isReverseMode = currentTransition.reverseMode === 'reverse';
    const configuredDurationSec = Number(currentTransition.durationSec);

    const getMediaErrorDetails = () => {
@ -374,7 +345,7 @@ export function useTransitionPlayback(
        networkState: video.networkState,
        duration: video.duration,
        configuredDurationSec,
-        reverseMode: currentTransition.reverseMode,
+        isBack: currentTransition.isBack,
        mediaError: getMediaErrorDetails(),
        error: error instanceof Error ? error : { error },
      });
@ -388,9 +359,7 @@ export function useTransitionPlayback(
      ) {
        return;
      }
-      // Finish slightly BEFORE the video ends to ensure last frame is visible
-      // and prevent browser-specific 'ended' event quirks (black frame)
-      const finishBeforeEndMs = 50; // 50ms before video naturally ends
+      const finishBeforeEndMs = 50;
      const finishMs = Math.max(100, durationSec * 1000 - finishBeforeEndMs);
      finishTimerRef.current = setTimeout(
        () => finishPlayback('duration-timer'),
@ -400,34 +369,33 @@ export function useTransitionPlayback(

    const attemptPlay = () => {
      video.play().catch((playError) => {
-        if (!isReverseMode) {
-          logIssue('play-failed', playError);
-        }
+        logIssue('play-failed', playError);
      });
    };

    const resolvePlayableSource = async (): Promise<string> => {
-      // 1. Try storage key lookup first (most reliable for cache hits)
      const getReadyBlobUrl = preloadRef.current?.getReadyBlobUrl;
-      const storageKey = currentTransition.storageKey;
-      if (getReadyBlobUrl && storageKey) {
-        const readyUrl = getReadyBlobUrl(storageKey);
+      const currentStorageKey = storageKey;
+
+      // 1. Try storage key lookup first (most reliable for cache hits)
+      if (getReadyBlobUrl && currentStorageKey) {
+        const readyUrl = getReadyBlobUrl(currentStorageKey);
        if (readyUrl) {
          logger.info('Using ready blob URL from storage key', {
-            storageKey: storageKey.slice(-50),
+            storageKey: currentStorageKey.slice(-50),
          });
          return readyUrl;
        }
      }

-      // 2. Try cached blob URL by storage key (post-refresh scenario)
+      // 2. Try cached blob URL by storage key
      const getCachedBlobUrl = preloadRef.current?.getCachedBlobUrl;
-      if (getCachedBlobUrl && storageKey) {
+      if (getCachedBlobUrl && currentStorageKey) {
        try {
-          const cachedBlobUrl = await getCachedBlobUrl(storageKey);
+          const cachedBlobUrl = await getCachedBlobUrl(currentStorageKey);
          if (cachedBlobUrl) {
            logger.info('Using cached blob URL from storage key', {
-              storageKey: storageKey.slice(-50),
+              storageKey: currentStorageKey.slice(-50),
            });
            lastLoadedBlobUrlRef.current = cachedBlobUrl;
            lastLoadedSourceUrlRef.current = sourceUrl;
@ -438,7 +406,7 @@ export function useTransitionPlayback(
        }
      }

-      // 3. Reuse cached blob URL if same source (existing logic)
+      // 3. Reuse cached blob URL if same source
      if (
        lastLoadedBlobUrlRef.current &&
        lastLoadedSourceUrlRef.current === sourceUrl
@ -456,7 +424,6 @@ export function useTransitionPlayback(

      const needsBlobUrl = shouldLoadViaBlob(
        sourceUrl,
-        currentTransition.reverseMode,
        featuresRef.current?.useBlobUrl,
      );

@ -481,7 +448,7 @@ export function useTransitionPlayback(
          const cachedBlobUrl = await getCachedBlobUrl(sourceUrl);
          if (cachedBlobUrl) {
            logger.info('Using preloaded blob URL from cache', {
-              reverseMode: currentTransition.reverseMode,
+              isBack: currentTransition.isBack,
            });
            lastLoadedBlobUrlRef.current = cachedBlobUrl;
            lastLoadedSourceUrlRef.current = sourceUrl;
@ -494,17 +461,13 @@ export function useTransitionPlayback(
        }
      }

-      // 6. Fetch video as blob with presigned URL support
-      // Follows usePageSwitch.loadImageWithFallback pattern:
-      // Try presigned URL first (SW can intercept for caching), fallback to proxy if it fails
-      logger.info('Fetching video as blob for seeking support', {
-        reverseMode: currentTransition.reverseMode,
+      // 6. Fetch video as blob
+      logger.info('Fetching video as blob', {
+        isBack: currentTransition.isBack,
      });

-      // Re-resolve URL to get presigned URL if now available
-      // (may have been cached since transition started)
-      const freshUrl = storageKey
-        ? resolveAssetPlaybackUrl(storageKey)
+      const freshUrl = currentStorageKey
+        ? resolveAssetPlaybackUrl(currentStorageKey)
        : sourceUrl;

      const token =
@ -512,7 +475,6 @@ export function useTransitionPlayback(
          ? localStorage.getItem('token') || ''
          : '';

-      // Helper: Fetch video and return blob URL, caching for next time
      const fetchVideoAsBlob = async (url: string): Promise<string> => {
        logger.info('Fetching video from URL', {
          url: url.slice(0, 80),
@ -522,14 +484,13 @@ export function useTransitionPlayback(
        const response = await axios.get(url, {
          responseType: 'blob',
          headers: token ? { Authorization: `Bearer ${token}` } : undefined,
-          baseURL: '', // Prevent double /api/ prefix when using buildProxyUrl
+          baseURL: '',
        });

        const blob = response.data as Blob;

-        // Cache for next time using existing DownloadManager pattern
-        if (storageKey) {
-          const normalizedKey = extractStoragePath(storageKey);
+        if (currentStorageKey) {
+          const normalizedKey = extractStoragePath(currentStorageKey);
          const blobUrl = await downloadManager.cacheBlob(normalizedKey, blob, {
            assetType: 'transition',
          });
@ -538,7 +499,6 @@ export function useTransitionPlayback(
          return blobUrl;
        }

-        // Fallback: create blob URL without caching
        const blobUrl = URL.createObjectURL(blob);
        lastLoadedBlobUrlRef.current = blobUrl;
        lastLoadedSourceUrlRef.current = sourceUrl;
@ -549,16 +509,14 @@ export function useTransitionPlayback(
      };

      try {
-        // Try fetching with potentially presigned URL (SW can intercept if S3)
        return await fetchVideoAsBlob(freshUrl);
      } catch (error) {
-        // If presigned URL failed and we have storage key, retry with proxy
-        if (storageKey && isPresignedUrl(freshUrl)) {
+        if (currentStorageKey && isPresignedUrl(freshUrl)) {
          logger.info('Presigned URL failed, retrying with proxy', {
-            storageKey: storageKey.slice(-40),
+            storageKey: currentStorageKey.slice(-40),
          });
-          markPresignedUrlFailed(storageKey);
-          const proxyUrl = buildProxyUrl(storageKey);
+          markPresignedUrlFailed(currentStorageKey);
+          const proxyUrl = buildProxyUrl(currentStorageKey);
          return await fetchVideoAsBlob(proxyUrl);
        }
        throw error;
@ -567,7 +525,7 @@ export function useTransitionPlayback(

    const loadAndPlay = async () => {
      logger.info('loadAndPlay called', {
-        reverseMode: currentTransition.reverseMode,
+        isBack: currentTransition.isBack,
        sourceUrl,
      });

@ -582,47 +540,18 @@ export function useTransitionPlayback(
        if (didFinishRef.current) return;

        video.pause();
-        stopReverseRef.current?.();
-
-        const isSameSource =
-          lastLoadedSourceUrlRef.current === playableSourceUrl;
-
-        if (isReverseMode && isSameSource && video.readyState >= 2) {
-          logger.info('Reusing buffered video for reverse', {
-            readyState: video.readyState,
-            duration: video.duration,
-            bufferedEnd: getBufferedEnd(video),
-          });
-          didStartPlaybackRef.current = true; // Prevent canplaythrough from double-starting
-          setPhase('reversing');
-          void startReverseRef.current?.();
-          return;
-        }
-
        video.src = playableSourceUrl;
-        // For reverse mode, seek to a large value (browser clamps to duration)
-        // This prevents showing frame 0 while loading
-        video.currentTime = isReverseMode ? 999999 : 0;
+        video.currentTime = 0;
        video.load();
        lastLoadedSourceUrlRef.current = playableSourceUrl;
        currentPlayableUrlRef.current = playableSourceUrl;

-        // Only attempt play for forward playback
-        // For reverse mode, wait for canplaythrough to trigger startReverse()
-        if (!isReverseMode) {
-          attemptPlay();
-        }
+        attemptPlay();

        startWatchdogTimerRef.current = setTimeout(() => {
          if (didStartPlaybackRef.current || didFinishRef.current) return;
          logIssue('playback-start-slow');
-          if (isReverseMode) {
-            didStartPlaybackRef.current = true;
-            setPhase('reversing');
-            void startReverseRef.current?.();
-          } else {
-            attemptPlay();
-          }
+          attemptPlay();
        }, playbackStartMs);
      } catch (error) {
        logIssue('source-prepare-failed', error);
@ -632,62 +561,24 @@ export function useTransitionPlayback(

    const onLoadedMetadata = () => {
      if (didFinishRef.current) return;
-      if (!isReverseMode) {
-        video.currentTime = 0;
-        attemptPlay();
-      }
-    };
-
-    const onCanPlayThrough = () => {
-      if (didFinishRef.current) return;
-      // Skip if reverse playback already started (avoid interference from seek events)
-      if (isReverseMode && didStartPlaybackRef.current) return;
-
-      logger.info('canplaythrough fired', {
-        reverseMode: currentTransition.reverseMode,
-        didStartPlayback: didStartPlaybackRef.current,
-      });
-
-      if (isReverseMode && !didStartPlaybackRef.current) {
-        didStartPlaybackRef.current = true;
-        if (startWatchdogTimerRef.current) {
-          clearTimeout(startWatchdogTimerRef.current);
-          startWatchdogTimerRef.current = null;
-        }
-        video.pause();
-        setPhase('reversing');
-        void startReverseRef.current?.();
-      }
+      video.currentTime = 0;
+      attemptPlay();
    };

    const onCanPlay = () => {
      if (didFinishRef.current) return;
-      if (isReverseMode) return; // Don't play for reverse mode
      attemptPlay();
    };

    const onPlaying = () => {
      logger.info('onPlaying fired', {
-        reverseMode: currentTransition.reverseMode,
+        isBack: currentTransition.isBack,
        didStartPlayback: didStartPlaybackRef.current,
        didFinish: didFinishRef.current,
      });

      if (didFinishRef.current) return;

-      if (isReverseMode && !didStartPlaybackRef.current) {
-        logger.info('Triggering reverse from onPlaying');
-        didStartPlaybackRef.current = true;
-        if (startWatchdogTimerRef.current) {
-          clearTimeout(startWatchdogTimerRef.current);
-          startWatchdogTimerRef.current = null;
-        }
-        video.pause();
-        setPhase('reversing');
-        void startReverseRef.current?.();
-        return;
-      }
-
      didStartPlaybackRef.current = true;
      setPhase('playing');

@ -696,23 +587,19 @@ export function useTransitionPlayback(
        startWatchdogTimerRef.current = null;
      }

-      if (!isReverseMode) {
-        const mediaDurationSec = Number(video.duration);
-        const durationSec =
-          Number.isFinite(configuredDurationSec) && configuredDurationSec > 0
-            ? configuredDurationSec
-            : Number.isFinite(mediaDurationSec) && mediaDurationSec > 0
-              ? mediaDurationSec
-              : NaN;
-        if (Number.isFinite(durationSec) && durationSec > 0) {
-          scheduleFinishByDuration(durationSec);
-        }
+      const mediaDurationSec = Number(video.duration);
+      const durationSec =
+        Number.isFinite(configuredDurationSec) && configuredDurationSec > 0
+          ? configuredDurationSec
+          : Number.isFinite(mediaDurationSec) && mediaDurationSec > 0
+            ? mediaDurationSec
+            : NaN;
+      if (Number.isFinite(durationSec) && durationSec > 0) {
+        scheduleFinishByDuration(durationSec);
      }
    };

    const onEnded = () => {
-      // For reverse mode, ignore 'ended' event - wait for reverse playback to complete
-      if (isReverseMode) return;
      finishPlayback('ended');
    };

@ -720,7 +607,15 @@ export function useTransitionPlayback(
      if (didFinishRef.current) return;
      logIssue('video-error');

-      // Check if this is a presigned URL failure (likely CORS)
+      const errorCode = video.error?.code;
+      if (errorCode === 3 && !didTryDecodeRetryRef.current) {
+        logger.info('Safari video decode error, attempting reload');
+        didTryDecodeRetryRef.current = true;
+        video.load();
+        attemptPlay();
+        return;
+      }
+
      const currentUrl = currentPlayableUrlRef.current;
      if (
        currentUrl &&
@ -731,14 +626,11 @@ export function useTransitionPlayback(
          url: currentUrl.slice(0, 80),
        });

-        // Mark presigned URL as failed so future resolves use proxy
-        // Extract storage key from the original transition videoUrl
        const originalVideoUrl = currentTransition.videoUrl;
        if (originalVideoUrl && isRelativeStoragePath(originalVideoUrl)) {
          markPresignedUrlFailed(originalVideoUrl);
        }

-        // Get proxy fallback URL using storage key
        const videoStorageKey = currentTransition.videoUrl;
        if (videoStorageKey && isRelativeStoragePath(videoStorageKey)) {
          const fallbackUrl = buildProxyUrl(videoStorageKey);
@ -768,7 +660,6 @@ export function useTransitionPlayback(
    };

    video.addEventListener('loadedmetadata', onLoadedMetadata);
-    video.addEventListener('canplaythrough', onCanPlayThrough);
    video.addEventListener('canplay', onCanPlay);
    video.addEventListener('playing', onPlaying);
    video.addEventListener('ended', onEnded);
@ -786,7 +677,6 @@ export function useTransitionPlayback(

    return () => {
      video.removeEventListener('loadedmetadata', onLoadedMetadata);
-      video.removeEventListener('canplaythrough', onCanPlayThrough);
      video.removeEventListener('canplay', onCanPlay);
      video.removeEventListener('playing', onPlaying);
      video.removeEventListener('ended', onEnded);
@ -794,11 +684,11 @@ export function useTransitionPlayback(
      video.removeEventListener('abort', onAbort);
      video.removeEventListener('stalled', onStalled);
      clearTimers();
-      stopReverseRef.current?.();
    };
  }, [
    sourceUrl,
-    transition?.reverseMode, // Re-run effect when reverseMode changes (same video, different direction)
+    storageKey,
+    transition?.isBack,
    videoRef,
    playbackStartMs,
    hardTimeoutMs,
@ -819,8 +709,8 @@ export function useTransitionPlayback(

  return {
    phase,
-    isBuffering: isReverseBufferingLocal,
-    isReversing,
+    isBuffering: false, // No longer have buffering from frame-stepping
+    isReversing: false, // No longer support frame-stepping reverse
    cancel,
    forceComplete,
  };
--- a/frontend/src/hooks/useTransitionPreview.ts
+++ b/frontend/src/hooks/useTransitionPreview.ts
@ -103,27 +103,24 @@ export function useTransitionPreview({
        return;
      }

-      // Check for separate reverse video if needed
-      if (
-        direction === 'back' &&
-        element.transitionReverseMode === 'separate_video' &&
-        !element.reverseVideoUrl
-      ) {
+      // For back navigation, check if reversed video is available
+      // (either manually uploaded or backend-generated)
+      if (direction === 'back' && !element.reverseVideoUrl) {
        onError?.(
-          'Select back-transition asset or switch reverse mode to Auto Reverse.',
+          'Reversed video not available. Save the page to generate it.',
        );
        return;
      }

+      // Determine reverse mode:
+      // - 'none' for forward navigation
+      // - 'separate' for back navigation (uses pre-reversed video)
+      const reverseMode = direction === 'back' ? 'separate' : 'none';
+
      const previewState: TransitionPreviewState = {
        videoUrl: element.transitionVideoUrl,
        storageKey: element.transitionVideoUrl, // Raw storage path for cache lookup
-        reverseMode:
-          direction === 'forward'
-            ? 'none'
-            : element.transitionReverseMode === 'separate_video'
-              ? 'separate'
-              : 'reverse',
+        reverseMode,
        reverseVideoUrl: element.reverseVideoUrl,
        reverseStorageKey: element.reverseVideoUrl,
        durationSec: element.transitionDurationSec,
--- a/frontend/src/lib/browserUtils.ts
+++ b/frontend/src/lib/browserUtils.ts
@ -0,0 +1,89 @@
+/**
+ * Browser Utilities
+ *
+ * Centralized browser detection and cross-browser timing utilities.
+ * Follows patterns from useNetworkAware.ts for vendor-prefixed API detection.
+ */
+
+/**
+ * Detect Safari browser (macOS and iOS).
+ * Uses feature detection pattern from useNetworkAware.ts.
+ */
+export const isSafari = (): boolean => {
+  if (typeof navigator === 'undefined') return false;
+  const ua = navigator.userAgent;
+  // Safari but not Chrome/Chromium-based
+  return /^((?!chrome|android).)*safari/i.test(ua);
+};
+
+/**
+ * Detect iOS Safari specifically.
+ */
+export const isIOSSafari = (): boolean => {
+  if (typeof navigator === 'undefined') return false;
+  const ua = navigator.userAgent;
+  return /iPad|iPhone|iPod/.test(ua) && !('MSStream' in window);
+};
+
+/**
+ * Schedule a callback to run after the next browser paint.
+ * Safari-compatible timing that ensures state updates occur on the correct paint cycle.
+ *
+ * Safari's RAF scheduler can fire multiple nested RAFs in the same frame,
+ * defeating the double-RAF pattern commonly used in React.
+ * This uses setTimeout to create a macrotask boundary, ensuring the callback
+ * runs after the current paint cycle completes.
+ *
+ * @param callback - Function to run after paint
+ */
+export const scheduleAfterPaint = (callback: () => void): void => {
+  if (typeof window === 'undefined') {
+    callback();
+    return;
+  }
+
+  // setTimeout(0) creates a macrotask boundary
+  // RAF ensures we're synced with the next paint cycle
+  // This pattern works reliably across all browsers including Safari
+  setTimeout(() => {
+    requestAnimationFrame(callback);
+  }, 0);
+};
+
+/**
+ * Schedule a callback with explicit frame delay.
+ * Useful when you need to ensure a specific number of frames have passed.
+ *
+ * @param callback - Function to run after delay
+ * @param frames - Number of frames to wait (default: 1)
+ * @returns Cleanup function to cancel the scheduled callback
+ */
+export const scheduleAfterFrames = (
+  callback: () => void,
+  frames = 1,
+): (() => void) => {
+  if (typeof window === 'undefined') {
+    callback();
+    // eslint-disable-next-line @typescript-eslint/no-empty-function
+    return () => {};
+  }
+
+  let cancelled = false;
+  let frameCount = 0;
+
+  const tick = () => {
+    if (cancelled) return;
+    frameCount++;
+    if (frameCount >= frames) {
+      callback();
+    } else {
+      requestAnimationFrame(tick);
+    }
+  };
+
+  requestAnimationFrame(tick);
+
+  return () => {
+    cancelled = true;
+  };
+};
--- a/frontend/src/lib/navigationHelpers.ts
+++ b/frontend/src/lib/navigationHelpers.ts
@ -175,7 +175,7 @@ export const getNavigationDirection = (

 /**
 * Check if transition is actively blocking navigation.
- * Navigation should be blocked during preparing, playing, or reversing phases.
+ * Navigation should be blocked during preparing or playing phases.
 *
 * @param transitionPhase - Current transition phase
 * @param isBuffering - Whether video is buffering
@ -185,14 +185,16 @@ export const isTransitionBlocking = (
  transitionPhase: TransitionPhase,
  isBuffering: boolean,
 ): boolean => {
-  const activePhases: TransitionPhase[] = ['preparing', 'playing', 'reversing'];
+  const activePhases: TransitionPhase[] = ['preparing', 'playing'];
  return activePhases.includes(transitionPhase) || isBuffering;
 };

 /**
 * Check if element has a playable transition.
- * A transition is playable if it has a video URL, and for back navigation,
- * either supports reverse or has a separate reverse video.
+ * A transition is playable if:
+ * - Forward navigation: has a video URL
+ * - Back navigation: has a video URL AND a reversed video URL
+ *   (reversed video is pre-generated by backend)
 *
 * @param element - Element with transition properties
 * @param direction - Navigation direction
@ -201,7 +203,6 @@ export const isTransitionBlocking = (
 export const hasPlayableTransition = (
  element: {
    transitionVideoUrl?: string;
-    transitionReverseMode?: string;
    reverseVideoUrl?: string;
  },
  direction: 'back' | 'forward' = 'forward',
@ -210,12 +211,8 @@ export const hasPlayableTransition = (
    return false;
  }

-  // For back navigation with separate_video mode, need reverse video
-  if (
-    direction === 'back' &&
-    element.transitionReverseMode === 'separate_video' &&
-    !element.reverseVideoUrl
-  ) {
+  // For back navigation, require pre-reversed video (generated by backend)
+  if (direction === 'back' && !element.reverseVideoUrl) {
    return false;
  }

--- a/frontend/src/pages/constructor.tsx
+++ b/frontend/src/pages/constructor.tsx
@ -358,10 +358,9 @@ const ConstructorPage = ({ mode = 'constructor' }: ConstructorPageProps) => {
  // Destructure stable callback reference to avoid infinite loops in useEffect deps
  const pageSwitchToPage = pageSwitch.switchToPage;

-  // Use shared background transition hook for direct navigation clearing and fade-in
-  // (No fade-out needed in constructor - transitions complete immediately)
-  // NOTE: Must be defined before switchToPage callback which uses resetFadeIn
-  const { isFadingIn, elementsOpacity, resetFadeIn } = useBackgroundTransition({
+  // Use shared background transition hook for direct navigation clearing and crossfade
+  // Crossfade starts automatically when new background is ready
+  const { isFadingIn } = useBackgroundTransition({
    pageSwitch,
    fadeIn: {
      hasActiveTransition: Boolean(transitionPreview),
@ -374,9 +373,6 @@ const ConstructorPage = ({ mode = 'constructor' }: ConstructorPageProps) => {
  // isBack parameter indicates this is a back navigation (pops history instead of pushing)
  const switchToPage = useCallback(
    async (page: TourPage | null, isBack = false) => {
-      // Reset fade-in state to start fresh
-      resetFadeIn();
-
      // Mark this page as initialized to prevent redundant effect calls
      if (page) {
        lastInitializedPageIdRef.current = page.id;
@ -386,6 +382,7 @@ const ConstructorPage = ({ mode = 'constructor' }: ConstructorPageProps) => {
      updateBackgroundFromPage(page);

      // Use hook to resolve and set blob URLs for display
+      // Fade starts automatically when new background is ready (crossfade effect)
      await pageSwitchToPage(
        page
          ? {
@ -403,12 +400,7 @@ const ConstructorPage = ({ mode = 'constructor' }: ConstructorPageProps) => {
        },
      );
    },
-    [
-      pageSwitchToPage,
-      updateBackgroundFromPage,
-      applyPageSelection,
-      resetFadeIn,
-    ],
+    [pageSwitchToPage, updateBackgroundFromPage, applyPageSelection],
  );

  const { isBuffering: isReverseBuffering } = useTransitionPlayback({
@ -1213,11 +1205,8 @@ const ConstructorPage = ({ mode = 'constructor' }: ConstructorPageProps) => {
            ? 'Create transition'
            : selectedElement?.label || 'Element editor';

-  if (backgroundImageSrc) {
-    canvasBackgroundStyle.backgroundImage = `url("${backgroundImageSrc}")`;
-    canvasBackgroundStyle.backgroundSize = 'cover';
-    canvasBackgroundStyle.backgroundPosition = 'center';
-  }
+  // Background image is rendered by CanvasBackground component (same as runtime)
+  // No CSS background-image needed on canvas div

  // Duration notes for UI display
  const durationNotes = useMemo(
@ -1466,8 +1455,10 @@ const ConstructorPage = ({ mode = 'constructor' }: ConstructorPageProps) => {
              backgroundVideoUrl={backgroundVideoSrc}
              backgroundAudioUrl={backgroundAudioSrc}
              previousBgImageUrl={pageSwitch.previousBgImageUrl}
+              previousBgVideoUrl={pageSwitch.previousBgVideoUrl}
              isSwitching={pageSwitch.isSwitching}
              isNewBgReady={pageSwitch.isNewBgReady}
+              isFadingIn={isFadingIn}
              onBackgroundReady={() => pageSwitch.markBackgroundReady()}
              videoAutoplay={backgroundVideoAutoplay}
              videoLoop={backgroundVideoLoop}
@ -1478,13 +1469,7 @@ const ConstructorPage = ({ mode = 'constructor' }: ConstructorPageProps) => {

            {/* Elements container - z-10 ensures they appear above backdrop layer */}
            <div
-              className='absolute inset-0 z-10'
-              style={{
-                opacity: elementsOpacity,
-                transition: isFadingIn
-                  ? `opacity ${CANVAS_CONFIG.pageTransition.fadeInDurationMs}ms ${CANVAS_CONFIG.pageTransition.easing}`
-                  : 'none',
-              }}
+              className={`absolute inset-0 z-10 ${isFadingIn ? 'animate-crossfade-in' : ''}`}
            >
              {isLoading ? (
                <div className='absolute inset-0 flex items-center justify-center'>
@ -1590,6 +1575,7 @@ const ConstructorPage = ({ mode = 'constructor' }: ConstructorPageProps) => {
        videoRef={transitionVideoRef}
        isActive={Boolean(transitionPreview)}
        isBuffering={isReverseBuffering}
+        letterboxStyles={letterboxStyles}
      />

      {/* Gallery Carousel Overlay */}
--- a/frontend/src/types/constructor.ts
+++ b/frontend/src/types/constructor.ts
@ -224,8 +224,12 @@ export interface CanvasElement extends BaseCanvasElement {
  /** Target page slug for navigation - slugs are consistent across environments */
  targetPageSlug?: string;
  transitionVideoUrl?: string;
+  /** Storage key for the transition video (for cache lookup) */
+  transitionStorageKey?: string;
  transitionReverseMode?: 'auto_reverse' | 'separate_video';
  reverseVideoUrl?: string;
+  /** Storage key for the reversed transition video (pre-generated by backend) */
+  transitionReversedStorageKey?: string;
  /** Back navigation mode: 'target_page' navigates to fixed slug, 'history' uses page history */
  navBackMode?: 'target_page' | 'history';
  transitionDurationSec?: number;
--- a/frontend/src/types/presentation.ts
+++ b/frontend/src/types/presentation.ts
@ -15,9 +15,9 @@ export interface TransitionPreviewState {
  videoUrl: string;
  /** Raw storage path for cache lookup */
  storageKey: string;
-  /** Playback mode: none (forward), reverse (auto-reverse), separate (use reverseVideoUrl) */
-  reverseMode: 'none' | 'reverse' | 'separate';
-  /** Resolved URL for separate reverse video */
+  /** Playback mode: none (forward), separate (use reverseVideoUrl for back navigation) */
+  reverseMode: 'none' | 'separate';
+  /** Resolved URL for separate reverse video (pre-generated by backend) */
  reverseVideoUrl?: string;
  /** Raw storage path for reverse video cache lookup */
  reverseStorageKey?: string;
@ -95,7 +95,7 @@ export type TransitionPhase =
  | 'idle'
  | 'preparing'
  | 'playing'
-  | 'reversing'
+  | 'finishing'
  | 'completed';

 /**
--- a/frontend/tailwind.config.js
+++ b/frontend/tailwind.config.js
@ -42,8 +42,8 @@ module.exports = {
        }
      },
      animation: {
-        'fade-out': 'fade-out 250ms ease-in-out',
-        'fade-in': 'fade-in 250ms ease-in-out'
+        'fade-out': 'fade-out 300ms ease-out',
+        'fade-in': 'fade-in 300ms ease-out'
      },
      colors: {
        dark: {