Revert to version 3c8cf08

Dockerfile

@@ -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

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...' && \
+  echo 'Backend and frontend are up.' && \
-  yarn --cwd /app/app-shell start && \
   wait $NGINX_PID"]

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
 

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",

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,

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;

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)
+  },
+};

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: {

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;
+    }
   }
 
   /**

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,

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;

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,
+};

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:
+acorn@^8.9.0:
-  version "8.15.0"
+  version "8.16.0"
-
+  resolved "https://registry.yarnpkg.com/acorn/-/acorn-8.16.0.tgz#4ce79c89be40afe7afe8f3adb902a1f1ce9ac08a"
-agent-base@^7.1.0, agent-base@^7.1.2:
+  integrity sha512-UVJyE9MttOsBQIDKw1skb9nAwQuR5wuGD3+82K6JgJlm/Y+KI92oNsMNGZCYdDsVtRHSak0pcV5Dno5+4jh9sw==
-  version "7.1.4"
-  resolved "https://registry.npmjs.org/agent-base/-/agent-base-7.1.4.tgz"
-  integrity sha512-MnA+YT8fwfJPgBx3m60MNqakm30XOkyIoH1y6huTQvC0PwZG7ki8NacLBcrPbNoo8vEZy7Jpuk7+jMO+CUovTQ==
 
 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:
+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==
-  dependencies:
-    balanced-match "^1.0.0"
-
-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:
+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==
-  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:
   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:
+debug@^4.3.1, debug@^4.3.2:
-  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:
   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:
+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==
-  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:
   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:
+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==
-  dependencies:
-    call-bound "^1.0.2"
-    has-symbols "^1.1.0"
-    safe-regex-test "^1.1.0"
-
-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:
+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==
-  dependencies:
-    brace-expansion "^2.0.2"
-
-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:
+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==
-
-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:
+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==
-
-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:
+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==
-  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:
   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"

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
@@ -36,10 +30,10 @@ services:
 
   backend:
     image: backend
+    build: ../backend
     volumes:
       - ./wait-for-it.sh:/usr/src/app/wait-for-it.sh
       - ./start-backend.sh:/usr/src/app/start-backend.sh
-    build: ../backend
     environment:
       - DB_HOST=db
     ports:
@@ -51,8 +45,4 @@ services:
         max-file: "3"
     depends_on:
       - "db"
-    
-
-    
     command: ["bash", "./wait-for-it.sh", "db:5432", "--timeout=0", "--strict", "--", "bash", "./start-backend.sh"]
-    

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.

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 */}
+      {/* Previous background overlays - show during loading AND crossfade.
-      {previousBgImageUrl && isSwitching && !isNewBgReady && (
+          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 && (

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';
@@ -15,27 +18,54 @@ 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'>
+    // 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 object-cover transition-opacity duration-300 ease-linear'
+          className={`absolute inset-0 h-full w-full transition-opacity duration-300 ease-linear ${
-        style={{ opacity: isBuffering ? 0 : 1 }}
+            videoFit === 'cover' ? 'object-cover' : 'object-contain'
+          }`}
+          style={{ opacity: videoOpacity }}
           muted
           playsInline
           preload='auto'
           disablePictureInPicture
         />
       </div>
+    </div>
   );
 };
 

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
+        // Direct navigation with crossfade effect:
-        // Reset fade-in state to start fresh
+        // useBackgroundTransition detects switching and applies animation classes
-        resetFadeIn();
+        // - New page gets animate-crossfade-in (0 → 1)
-        // Previous background stays visible until new one is ready
+        // - 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,
         );
       }
     },
@@ -534,15 +542,46 @@ export default function RuntimePresentation({
           style={{
             ...cssVars,
             ...letterboxStyles,
-            backgroundImage: backgroundImageUrl
+          }}
-              ? `url("${backgroundImageUrl}")`
+        >
-              : undefined,
+          <BackdropPortalProvider>
+            {/* Previous background overlays - show during loading AND crossfade.
+                Uses CSS animation for fade-out effect.
+                Cleared by useBackgroundTransition after fade completes. */}
+            {pageSwitch.previousBgImageUrl &&
+              (isFadingIn ||
+                (pageSwitch.isSwitching && !pageSwitch.isNewBgReady)) && (
+                <div
+                  className={`absolute inset-0 pointer-events-none z-0 ${isFadingIn ? 'animate-crossfade-out' : ''}`}
+                  style={{
+                    backgroundImage: `url("${pageSwitch.previousBgImageUrl}")`,
                     backgroundSize: 'contain',
                     backgroundPosition: 'center',
                     backgroundRepeat: 'no-repeat',
                   }}
+                />
+              )}
+            {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}
             >
-          <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. */}
@@ -587,21 +626,6 @@ export default function RuntimePresentation({
                 </div>
               )}
 
-            {/* Previous background overlay - shows during direct navigation until new bg is ready */}
-            {pageSwitch.previousBgImageUrl &&
-              pageSwitch.isSwitching &&
-              !pageSwitch.isNewBgReady && (
-                <div
-                  className='absolute inset-0 pointer-events-none z-10'
-                  style={{
-                    backgroundImage: `url("${pageSwitch.previousBgImageUrl}")`,
-                    backgroundSize: 'contain',
-                    backgroundPosition: 'center',
-                    backgroundRepeat: 'no-repeat',
-                  }}
-                />
-              )}
-
               {/* Background video - z-1 keeps it below backdrop blur (z-5) */}
               {backgroundVideoUrl && (
                 <video
@@ -617,15 +641,7 @@ export default function RuntimePresentation({
               )}
 
               {/* Page elements - z-40 ensures they appear above carousel background (z-10) and carousel controls (z-30) */}
-            <div
+              <div className='absolute inset-0 z-40'>
-              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}
@@ -638,6 +654,8 @@ export default function RuntimePresentation({
                   />
                 ))}
               </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'>
+              <TransitionPreviewOverlay
-                <video
+                videoRef={transitionVideoRef}
-                  ref={transitionVideoRef}
+                isActive={true}
-                  className='absolute inset-0 h-full w-full object-cover transition-opacity duration-300 ease-linear'
+                isBuffering={transitionPhase === 'preparing' || isBuffering}
-                  style={{
+                letterboxStyles={letterboxStyles}
-                    opacity:
+                opacity={isOverlayFadingOut ? 0 : 1}
-                      transitionPhase === 'preparing' ||
-                      isBuffering ||
-                      isOverlayFadingOut
-                        ? 0
-                        : 1,
-                  }}
-                  muted
-                  playsInline
-                  preload='auto'
-                  disablePictureInPicture
               />
-              </div>
             )}
 
             {/* Gallery Carousel Overlay */}

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.
      */

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)

frontend/src/css/main.css

@@ -34,68 +34,214 @@
   @apply bg-transparent border border-blue-600 text-blue-600 !important;
 }
 
-/* Element appear animation keyframes */
+/* Page crossfade animation keyframes - Safari optimized */
-@keyframes element-fade-in {
+@-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);
   }
 }
 

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) */
+  /** Handler to call when fade-in animation ends (pass to onAnimationEnd) */
-  elementsOpacity: number;
+  onFadeInAnimationEnd: () => void;
-  /** Reset fade-in state before starting new navigation */
+  /** 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.
+   * Reset fade-in state (for cleanup or cancellation).
-   * Clears any in-progress fade animation.
    */
   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 during the entire fade animation,
-   * The previous background stays visible until the new one is ready to paint.
+   * providing a smooth crossfade effect. Only cleared after fade ends.
    */
   useEffect(() => {
-    if (
+    if (pageSwitch.isSwitching && pageSwitch.isNewBgReady && !isFadingIn) {
-      pageSwitch.isSwitching &&
+      // Fade is complete - clear the previous background overlay
-      pageSwitch.isNewBgReady &&
+      // This also resets isSwitching state so next navigation triggers fade-in
-      pageSwitch.previousBgImageUrl
-    ) {
-      // New background is ready - clear the previous background overlay
       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
+   * IMPORTANT: Skip this for transitions - transition video IS the effect.
-   *
-   * 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
    */
-  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:
+    // Only start crossfade for NON-transition navigation
-    // - Just started switching (transition from false to true)
+    // Transitions use video overlay - no fade needed
-    // - No active transition video
     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,
   };
 }

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);
@@ -391,13 +403,11 @@ 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(() => {
+        scheduleAfterPaint(() => {
-          requestAnimationFrame(() => {
           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);
+
+      // 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
+    // Revoke the previous blob URLs after clearing
-    if (prevUrl) {
+    if (prevImageUrl) {
-      revokeBlobUrl(prevUrl);
+      revokeBlobUrl(prevImageUrl);
+    }
+    if (prevVideoUrl) {
+      revokeBlobUrl(prevVideoUrl);
     }
   }, [revokeBlobUrl]);
 
@@ -451,6 +473,7 @@ export function usePageSwitch(
     currentBgVideoUrl,
     currentBgAudioUrl,
     previousBgImageUrl,
+    previousBgVideoUrl,
     isSwitching,
     isNewBgReady,
     switchToPage,

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,
-  };
-}

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 {
+function shouldLoadViaBlob(url: string, useBlobUrlOption?: boolean): boolean {
-  return video.buffered.length > 0
-    ? video.buffered.end(video.buffered.length - 1)
-    : 0;
-}
-
-function shouldLoadViaBlob(
-  url: string,
-  reverseMode: ReverseMode,
-  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
+    // Use reversed video if this is back navigation with a separate reversed video
-      ? transition.reverseVideoUrl
+    if (transition.isBack && transition.reverseVideoUrl) {
-      : transition.videoUrl;
+      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
+    // Include isBack in the key so same video can play forward or as reversed
-    const sourceKey = `${sourceUrl}|${currentTransition.reverseMode}`;
+    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
+      const finishBeforeEndMs = 50;
-      // and prevent browser-specific 'ended' event quirks (black frame)
-      const finishBeforeEndMs = 50; // 50ms before video naturally ends
       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);
-        }
       });
     };
 
     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;
+      const currentStorageKey = storageKey;
-      if (getReadyBlobUrl && storageKey) {
+
-        const readyUrl = getReadyBlobUrl(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
+      // 6. Fetch video as blob
-      // Follows usePageSwitch.loadImageWithFallback pattern:
+      logger.info('Fetching video as blob', {
-      // Try presigned URL first (SW can intercept for caching), fallback to proxy if it fails
+        isBack: currentTransition.isBack,
-      logger.info('Fetching video as blob for seeking support', {
-        reverseMode: currentTransition.reverseMode,
       });
 
-      // Re-resolve URL to get presigned URL if now available
+      const freshUrl = currentStorageKey
-      // (may have been cached since transition started)
+        ? resolveAssetPlaybackUrl(currentStorageKey)
-      const freshUrl = storageKey
-        ? resolveAssetPlaybackUrl(storageKey)
         : 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 (currentStorageKey) {
-        if (storageKey) {
+          const normalizedKey = extractStoragePath(currentStorageKey);
-          const normalizedKey = extractStoragePath(storageKey);
           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 (currentStorageKey && isPresignedUrl(freshUrl)) {
-        if (storageKey && isPresignedUrl(freshUrl)) {
           logger.info('Presigned URL failed, retrying with proxy', {
-            storageKey: storageKey.slice(-40),
+            storageKey: currentStorageKey.slice(-40),
           });
-          markPresignedUrlFailed(storageKey);
+          markPresignedUrlFailed(currentStorageKey);
-          const proxyUrl = buildProxyUrl(storageKey);
+          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)
+        video.currentTime = 0;
-        // This prevents showing frame 0 while loading
-        video.currentTime = isReverseMode ? 999999 : 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();
-        }
 
         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();
-          }
         }, 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?.();
-      }
     };
 
     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');
 
@@ -696,7 +587,6 @@ export function useTransitionPlayback(
         startWatchdogTimerRef.current = null;
       }
 
-      if (!isReverseMode) {
       const mediaDurationSec = Number(video.duration);
       const durationSec =
         Number.isFinite(configuredDurationSec) && configuredDurationSec > 0
@@ -707,12 +597,9 @@ export function useTransitionPlayback(
       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,
+    isBuffering: false, // No longer have buffering from frame-stepping
-    isReversing,
+    isReversing: false, // No longer support frame-stepping reverse
     cancel,
     forceComplete,
   };

frontend/src/hooks/useTransitionPreview.ts

@@ -103,27 +103,24 @@ export function useTransitionPreview({
         return;
       }
 
-      // Check for separate reverse video if needed
+      // For back navigation, check if reversed video is available
-      if (
+      // (either manually uploaded or backend-generated)
-        direction === 'back' &&
+      if (direction === 'back' && !element.reverseVideoUrl) {
-        element.transitionReverseMode === 'separate_video' &&
-        !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:
+        reverseMode,
-          direction === 'forward'
-            ? 'none'
-            : element.transitionReverseMode === 'separate_video'
-              ? 'separate'
-              : 'reverse',
         reverseVideoUrl: element.reverseVideoUrl,
         reverseStorageKey: element.reverseVideoUrl,
         durationSec: element.transitionDurationSec,

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;
+  };
+};

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,
+ * A transition is playable if:
- * either supports reverse or has a separate reverse video.
+ * - 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
+  // For back navigation, require pre-reversed video (generated by backend)
-  if (
+  if (direction === 'back' && !element.reverseVideoUrl) {
-    direction === 'back' &&
-    element.transitionReverseMode === 'separate_video' &&
-    !element.reverseVideoUrl
-  ) {
     return false;
   }
 

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
+  // Use shared background transition hook for direct navigation clearing and crossfade
-  // (No fade-out needed in constructor - transitions complete immediately)
+  // Crossfade starts automatically when new background is ready
-  // NOTE: Must be defined before switchToPage callback which uses resetFadeIn
+  const { isFadingIn } = useBackgroundTransition({
-  const { isFadingIn, elementsOpacity, resetFadeIn } = 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],
-      pageSwitchToPage,
-      updateBackgroundFromPage,
-      applyPageSelection,
-      resetFadeIn,
-    ],
   );
 
   const { isBuffering: isReverseBuffering } = useTransitionPlayback({
@@ -1213,11 +1205,8 @@ const ConstructorPage = ({ mode = 'constructor' }: ConstructorPageProps) => {
             ? 'Create transition'
             : selectedElement?.label || 'Element editor';
 
-  if (backgroundImageSrc) {
+  // Background image is rendered by CanvasBackground component (same as runtime)
-    canvasBackgroundStyle.backgroundImage = `url("${backgroundImageSrc}")`;
+  // No CSS background-image needed on canvas div
-    canvasBackgroundStyle.backgroundSize = 'cover';
-    canvasBackgroundStyle.backgroundPosition = 'center';
-  }
 
   // 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'
+              className={`absolute inset-0 z-10 ${isFadingIn ? 'animate-crossfade-in' : ''}`}
-              style={{
-                opacity: elementsOpacity,
-                transition: isFadingIn
-                  ? `opacity ${CANVAS_CONFIG.pageTransition.fadeInDurationMs}ms ${CANVAS_CONFIG.pageTransition.easing}`
-                  : 'none',
-              }}
             >
               {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 */}

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;

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) */
+  /** Playback mode: none (forward), separate (use reverseVideoUrl for back navigation) */
-  reverseMode: 'none' | 'reverse' | 'separate';
+  reverseMode: 'none' | 'separate';
-  /** Resolved URL for separate reverse video */
+  /** 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';
 
 /**

frontend/tailwind.config.js

@@ -42,8 +42,8 @@ module.exports = {
         }
       },
       animation: {
-        'fade-out': 'fade-out 250ms ease-in-out',
+        'fade-out': 'fade-out 300ms ease-out',
-        'fade-in': 'fade-in 250ms ease-in-out'
+        'fade-in': 'fade-in 300ms ease-out'
       },
       colors: {
         dark: {