diff --git a/backend/app/controllers/post_imports_controller.rb b/backend/app/controllers/post_imports_controller.rb
deleted file mode 100644
index 9f3a6c8..0000000
--- a/backend/app/controllers/post_imports_controller.rb
+++ /dev/null
@@ -1,49 +0,0 @@
-class PostImportsController < ApplicationController
-  before_action :require_member!
-
-  def preview
-    rows = PostImportPreviewer.new.preview_rows(
-        rows: PostImportUrlListParser.parse(params[:source]))
-    render json: { rows: }
-  rescue ArgumentError => e
-    render_bad_request e.message
-  end
-
-  def validate
-    rows = normalised_import_rows allow_warning_fields: true
-    changed_row =
-        if params[:changed_row].to_s == 'all'
-          true
-        else
-          Integer(params[:changed_row], exception: false)
-        end
-    result =
-        PostImportPreviewer.new.preview_rows(rows:,
-                                             fetch_metadata: changed_row,
-                                             metadata_cache: { })
-    render json: { rows: result }
-  rescue ArgumentError => e
-    render_bad_request e.message
-  end
-
-  def create
-    result = PostImportRunner.new(actor: current_user,
-                                  rows: normalised_import_rows).run
-    render json: result, status: result[:created].positive? ? :created : :ok
-  rescue ArgumentError => e
-    render_bad_request e.message
-  end
-
-  private
-
-  def require_member!
-    return head :unauthorized unless current_user
-    return if current_user.gte_member?
-
-    head :forbidden
-  end
-
-  def normalised_import_rows allow_warning_fields: false
-    PostImportRowNormaliser.normalise!(params[:rows], allow_warning_fields:)
-  end
-end
diff --git a/backend/app/controllers/posts_controller.rb b/backend/app/controllers/posts_controller.rb
index 5bfbdb1..c4b9854 100644
--- a/backend/app/controllers/posts_controller.rb
+++ b/backend/app/controllers/posts_controller.rb
@@ -114,6 +114,37 @@ class PostsController < ApplicationController
     render json: PostRepr.base(post, current_user)
   end
 
+  def preview
+    return head :unauthorized unless current_user
+    return head :forbidden unless current_user.gte_member?
+    return render_bad_request('URL は必須です．') if params[:url].blank?
+
+    preview = PostImportPreviewer.new.preview_rows(
+        rows: [{
+            source_row: 1,
+            url: params[:url].to_s,
+            attributes: { },
+            provenance: { },
+            tag_sources: { } }],
+        fetch_metadata: true).first
+    return render_validation_error fields: preview[:validation_errors] if preview[:validation_errors].present?
+
+    render json: {
+        url: preview[:url],
+        title: preview[:attributes]['title'],
+        thumbnail_base: preview[:attributes]['thumbnail_base'],
+        tags: preview[:attributes]['tags'],
+        original_created_from: preview[:attributes]['original_created_from'],
+        original_created_before: preview[:attributes]['original_created_before'],
+        duration: preview[:attributes]['duration'],
+        video_ms: preview[:attributes]['video_ms'],
+        field_warnings: preview[:field_warnings],
+        base_warnings: preview[:base_warnings],
+        existing_post: compact_post(preview[:existing_post_id]) }
+  rescue ArgumentError => e
+    render_bad_request e.message
+  end
+
   def show
     post =
         Post
@@ -142,17 +173,21 @@ class PostsController < ApplicationController
     return head :unauthorized unless current_user
     return head :forbidden unless current_user.gte_member?
 
+    if bool?(:dry)
+      preflight = PostCreatePreflight.new(
+          attributes: post_create_attributes,
+          thumbnail: params[:thumbnail]).run
+      return render json: preflight
+    end
+
     post = PostCreator.new(actor: current_user,
-                           attributes: { title: params[:title], url: params[:url],
-                                         thumbnail: params[:thumbnail], tags: params[:tags],
-                                         original_created_from: params[:original_created_from],
-                                         original_created_before: params[:original_created_before],
-                                         parent_post_ids: parse_parent_post_ids,
-                                         video_ms: params[:video_ms],
-                                         duration: params[:duration] }).create!
+                           attributes: post_create_attributes.merge(
+                               thumbnail: params[:thumbnail])).create!
 
     post.reload
     render json: PostRepr.base(post), status: :created
+  rescue PostCreatePreflight::ValidationFailed => e
+    render_validation_error fields: e.fields, base: e.base_errors
   rescue Tag::NicoTagNormalisationError
     render_validation_error fields: { tags: 'ニコニコ・タグは直接指定できません．' }
   rescue Tag::DeprecatedTagNormalisationError
@@ -161,6 +196,8 @@ class PostsController < ApplicationController
     render_validation_error fields: { tags: ['タグ区間の記法が不正です．'] }
   rescue PostCreator::VideoMsParseError
     render_validation_error fields: { video_ms: ['動画時間の記法が不正です．'] }
+  rescue Post::RemoteThumbnailFetchFailed
+    render_validation_error fields: { thumbnail_base: ['サムネイル画像の取得に失敗しました．'] }
   rescue MiniMagick::Error
     render_validation_error fields: { thumbnail: ['サムネイル画像の変換に失敗しました．'] }
   rescue ArgumentError => e
@@ -169,6 +206,22 @@ class PostsController < ApplicationController
     render_post_form_record_invalid e.record
   end
 
+  def bulk
+    return head :unauthorized unless current_user
+    return head :forbidden unless current_user.gte_member?
+    return head :unsupported_media_type unless request.content_mime_type == Mime[:multipart_form]
+
+    result = PostBulkCreator.new(
+        actor: current_user,
+        posts: parse_bulk_posts_manifest,
+        thumbnails: parse_bulk_thumbnails).run
+    render json: result
+  rescue JSON::ParserError
+    render_bad_request 'posts manifest の JSON が不正です．'
+  rescue ArgumentError => e
+    render_validation_error base: [e.message]
+  end
+
   def viewed
     return head :unauthorized unless current_user
 
@@ -463,6 +516,63 @@ class PostsController < ApplicationController
     }.uniq
   end
 
+  def post_create_attributes
+    { title: params[:title],
+      url: params[:url],
+      thumbnail_base: params[:thumbnail_base],
+      tags: params[:tags],
+      original_created_from: params[:original_created_from],
+      original_created_before: params[:original_created_before],
+      parent_post_ids: parse_parent_post_ids,
+      video_ms: params[:video_ms],
+      duration: params[:duration] }
+  end
+
+  def parse_bulk_posts_manifest
+    manifest = params[:posts]
+    raise ArgumentError, 'posts は必須です．' if manifest.blank?
+
+    posts = JSON.parse(manifest)
+    raise ArgumentError, 'posts は配列で指定してください．' unless posts.is_a?(Array)
+    raise ArgumentError, '投稿件数は 1 件以上必要です．' if posts.empty?
+    raise ArgumentError, '投稿件数が多すぎます．' if posts.length > 100
+    raise ArgumentError, 'posts 要素の形式が不正です．' unless posts.all? { _1.is_a?(Hash) }
+
+    posts
+  end
+
+  def parse_bulk_thumbnails
+    thumbnails = { }
+    post_count = Array(JSON.parse(params[:posts].presence || '[]')).length
+
+    params.to_unsafe_h.each do |key, value|
+      match = key.match(/\Athumbnails\[(\d+)\]\z/)
+      next if match.nil?
+
+      index = Integer(match[1], 10)
+      raise ArgumentError, 'thumbnail index が範囲外です．' if index.negative? || index >= post_count
+
+      thumbnails[index] = value
+    end
+
+    thumbnails
+  end
+
+  def compact_post post_id
+    return nil if post_id.blank?
+
+    post = Post.with_attached_thumbnail.find_by(id: post_id)
+    return nil if post.nil?
+
+    { id: post.id,
+      title: post.title,
+      url: post.url,
+      thumbnail_url:
+          if post.thumbnail.attached?
+            rails_storage_proxy_url(post.thumbnail, only_path: false)
+          end }
+  end
+
   def sync_parent_posts! post, parent_post_ids
     if parent_post_ids.include?(post.id)
       post.errors.add :parent_post_ids, '自分自身を親投稿にはできません．'
diff --git a/backend/app/controllers/preview_controller.rb b/backend/app/controllers/preview_controller.rb
index 80e4f7a..4829e2b 100644
--- a/backend/app/controllers/preview_controller.rb
+++ b/backend/app/controllers/preview_controller.rb
@@ -38,27 +38,6 @@ class PreviewController < ApplicationController
     render_unprocessable_entity(e.message)
   end
 
-  def image
-    return render_bad_request('URL は必須です．') if params[:url].blank?
-
-    attachment = Post.resized_thumbnail_attachment(
-        StringIO.new(Preview::ThumbnailFetcher.fetch_image_response(params[:url]).body))
-    attachment[:io].rewind
-    send_data attachment[:io].read,
-              type: attachment[:content_type],
-              disposition: 'inline'
-  rescue Preview::UrlSafety::UnsafeUrl => e
-    render_bad_request(e.message)
-  rescue Preview::HttpFetcher::FetchTimeout => e
-    render_preview_error(e.message, :gateway_timeout)
-  rescue Preview::HttpFetcher::ResponseTooLarge => e
-    render_preview_error(e.message, :payload_too_large)
-  rescue Preview::HttpFetcher::FetchFailed => e
-    render_preview_error(e.message, :bad_gateway)
-  rescue Preview::ThumbnailFetcher::GenerationFailed, MiniMagick::Error => e
-    render_unprocessable_entity(e.message)
-  end
-
   private
 
   def require_member!
diff --git a/backend/app/models/post.rb b/backend/app/models/post.rb
index 3f58072..1190311 100644
--- a/backend/app/models/post.rb
+++ b/backend/app/models/post.rb
@@ -27,6 +27,18 @@ class Post < ApplicationRecord
     upload.rewind
   end
 
+  def self.remote_thumbnail_attachment(raw_url)
+    response = Preview::ThumbnailFetcher.fetch_image_response(raw_url)
+    resized_thumbnail_attachment(StringIO.new(response.body))
+  rescue Preview::UrlSafety::UnsafeUrl,
+         Preview::ThumbnailFetcher::GenerationFailed,
+         Preview::HttpFetcher::FetchFailed,
+         Preview::HttpFetcher::FetchTimeout,
+         Preview::HttpFetcher::ResponseTooLarge,
+         MiniMagick::Error => e
+    raise RemoteThumbnailFetchFailed, e.message
+  end
+
   belongs_to :uploaded_user, class_name: 'User', optional: true
 
   has_many :post_tags, dependent: :destroy, inverse_of: :post
@@ -157,17 +169,7 @@ class Post < ApplicationRecord
   end
 
   def attach_thumbnail_from_url! raw_url
-    response = Preview::ThumbnailFetcher.fetch_image_response(raw_url)
-    thumbnail.attach(
-        self.class.resized_thumbnail_attachment(
-            StringIO.new(response.body)))
-  rescue Preview::UrlSafety::UnsafeUrl,
-         Preview::ThumbnailFetcher::GenerationFailed,
-         Preview::HttpFetcher::FetchFailed,
-         Preview::HttpFetcher::FetchTimeout,
-         Preview::HttpFetcher::ResponseTooLarge,
-         MiniMagick::Error => e
-    raise RemoteThumbnailFetchFailed, e.message
+    thumbnail.attach(self.class.remote_thumbnail_attachment(raw_url))
   end
 
   private
diff --git a/backend/app/services/post_bulk_creator.rb b/backend/app/services/post_bulk_creator.rb
new file mode 100644
index 0000000..35b2454
--- /dev/null
+++ b/backend/app/services/post_bulk_creator.rb
@@ -0,0 +1,150 @@
+class PostBulkCreator
+  def initialize actor:, posts:, thumbnails:
+    @actor = actor
+    @posts = posts
+    @thumbnails = thumbnails
+  end
+
+  def run
+    results = @posts.each_with_index.map { |attributes, index|
+      create_row(attributes, index)
+    }
+
+    { results: }
+  end
+
+  private
+
+  def create_row attributes, index
+    preflight =
+        PostCreatePreflight.new(
+            attributes: attributes,
+            thumbnail: thumbnail_for(index, attributes)).run
+    if preflight[:existing_post].present?
+      return {
+          status: 'skipped',
+          existing_post: preflight[:existing_post] }
+    end
+
+    post = PostCreator.new(
+        actor: @actor,
+        attributes: normalised_attributes(attributes, preflight, index)).create!
+    result = {
+        status: 'created',
+        post: { id: post.id } }
+    result[:field_warnings] = preflight[:field_warnings] if preflight[:field_warnings].present?
+    result[:base_warnings] = preflight[:base_warnings] if preflight[:base_warnings].present?
+    result
+  rescue PostCreatePreflight::ValidationFailed => e
+    {
+        status: 'failed',
+        recoverable: true,
+        errors: e.fields,
+        base_errors: e.base_errors }
+  rescue ActiveRecord::RecordInvalid => e
+    existing_post = existing_post_for_race(attributes, e.record)
+    if existing_post.present?
+      return {
+          status: 'skipped',
+          existing_post: existing_post }
+    end
+
+    {
+        status: 'failed',
+        recoverable: true,
+        errors: e.record.errors.to_hash,
+        base_errors: e.record.errors[:base] }
+  rescue ActiveRecord::RecordNotUnique => e
+    raise unless e.message.include?('index_posts_on_url')
+
+    existing_post = existing_post_for_race(attributes)
+    raise if existing_post.nil?
+
+    {
+        status: 'skipped',
+        existing_post: existing_post }
+  rescue Tag::NicoTagNormalisationError
+    {
+        status: 'failed',
+        recoverable: true,
+        errors: { tags: ['ニコニコ・タグは直接指定できません．'] },
+        base_errors: [] }
+  rescue Tag::DeprecatedTagNormalisationError
+    {
+        status: 'failed',
+        recoverable: true,
+        errors: { tags: ['廃止済みタグは付与できません．'] },
+        base_errors: [] }
+  rescue PostCreator::VideoMsParseError
+    {
+        status: 'failed',
+        recoverable: true,
+        errors: { video_ms: ['動画時間の記法が不正です．'] },
+        base_errors: [] }
+  rescue Post::RemoteThumbnailFetchFailed
+    {
+        status: 'failed',
+        recoverable: true,
+        errors: { thumbnail_base: ['サムネイル画像の取得に失敗しました．'] },
+        base_errors: [] }
+  rescue ArgumentError => e
+    {
+        status: 'failed',
+        recoverable: true,
+        errors: { base: [e.message] },
+        base_errors: [] }
+  rescue StandardError => e
+    Rails.logger.error(
+        "post_bulk_creator_failure #{ { error: e.class.name,
+                                        message: e.message }.to_json }")
+    {
+        status: 'failed',
+        recoverable: false,
+        errors: { base: ['登録中にエラーが発生しました．'] },
+        base_errors: [] }
+  end
+
+  def normalised_attributes attributes, preflight, index
+    {
+        url: preflight[:url],
+        title: preflight[:title],
+        thumbnail_base: preflight[:thumbnail_base],
+        thumbnail: thumbnail_for(index, attributes),
+        tags: preflight[:tags],
+        parent_post_ids: preflight[:parent_post_ids],
+        original_created_from: preflight[:original_created_from],
+        original_created_before: preflight[:original_created_before],
+        duration: preflight[:duration],
+        video_ms: preflight[:video_ms] }
+  end
+
+  def thumbnail_for index, attributes
+    return nil if attributes['thumbnail_base'].present? || attributes[:thumbnail_base].present?
+
+    @thumbnails[index]
+  end
+
+  def existing_post_for_race attributes, record = nil
+    return nil if record.present? && !(record.errors.of_kind?(:url, :taken))
+
+    normal_url = PostUrlNormaliser.normalise(attributes['url'] || attributes[:url])
+    return nil if normal_url.blank?
+
+    compact_existing_post(Post.with_attached_thumbnail.find_by(url: normal_url))
+  end
+
+  def compact_existing_post post
+    return nil if post.nil?
+
+    {
+        id: post.id,
+        title: post.title,
+        url: post.url,
+        thumbnail_url:
+            if post.thumbnail.attached?
+              Rails.application.routes.url_helpers.rails_storage_proxy_url(
+                  post.thumbnail,
+                  only_path: false)
+            end }
+  end
+end
diff --git a/backend/app/services/post_create_preflight.rb b/backend/app/services/post_create_preflight.rb
new file mode 100644
index 0000000..1ea24f2
--- /dev/null
+++ b/backend/app/services/post_create_preflight.rb
@@ -0,0 +1,104 @@
+class PostCreatePreflight
+  class ValidationFailed < StandardError
+    attr_reader :fields, :base_errors
+
+    def initialize fields: { }, base_errors: []
+      super('入力内容を確認してください．')
+      @fields = fields
+      @base_errors = base_errors
+    end
+  end
+
+  def initialize attributes:, thumbnail: nil
+    @attributes = attributes.symbolize_keys
+    @thumbnail = thumbnail
+  end
+
+  def run
+    preview = PostImportPreviewer.new.preview_rows(
+        rows: [preview_row],
+        fetch_metadata: false).first
+
+    validate_thumbnail_upload!
+
+    if preview[:validation_errors].present?
+      raise ValidationFailed.new(fields: preview[:validation_errors])
+    end
+
+    {
+        url: preview[:url],
+        title: preview[:attributes]['title'],
+        thumbnail_base: preview[:attributes]['thumbnail_base'],
+        tags: preview[:attributes]['tags'],
+        parent_post_ids: preview[:attributes]['parent_post_ids'],
+        original_created_from: preview[:attributes]['original_created_from'],
+        original_created_before: preview[:attributes]['original_created_before'],
+        duration: preview[:attributes]['duration'],
+        video_ms: preview[:attributes]['video_ms'],
+        field_warnings: preview[:field_warnings],
+        base_warnings: preview[:base_warnings],
+        existing_post: existing_post_compact(preview[:existing_post_id]) }
+  end
+
+  private
+
+  def preview_row
+    {
+        source_row: 1,
+        url: @attributes[:url].to_s,
+        attributes: {
+            'title' => @attributes[:title].to_s,
+            'thumbnail_base' => @attributes[:thumbnail_base].to_s,
+            'original_created_from' => @attributes[:original_created_from].to_s,
+            'original_created_before' => @attributes[:original_created_before].to_s,
+            'duration' => @attributes[:duration].to_s,
+            'video_ms' => @attributes[:video_ms],
+            'tags' => @attributes[:tags].to_s,
+            'parent_post_ids' => parent_post_ids_text },
+        provenance: {
+            'url' => 'manual',
+            'title' => 'manual',
+            'thumbnail_base' => 'manual',
+            'original_created_from' => 'manual',
+            'original_created_before' => 'manual',
+            'duration' => 'manual',
+            'video_ms' => 'manual',
+            'tags' => 'manual',
+            'parent_post_ids' => 'manual' },
+        tag_sources: {
+            'automatic' => '',
+            'manual' => @attributes[:tags].to_s } }
+  end
+
+  def parent_post_ids_text
+    Array(@attributes[:parent_post_ids]).flat_map { _1.to_s.split }.join(' ')
+  end
+
+  def validate_thumbnail_upload!
+    return if @attributes[:thumbnail_base].present?
+    return if @thumbnail.blank?
+
+    attachment = Post.resized_thumbnail_attachment(@thumbnail)
+    attachment[:io].close if attachment[:io].respond_to?(:close)
+  rescue MiniMagick::Error
+    raise ValidationFailed.new(fields: { thumbnail: ['サムネイル画像の変換に失敗しました．'] })
+  end
+
+  def existing_post_compact post_id
+    return nil if post_id.blank?
+
+    post = Post.with_attached_thumbnail.find_by(id: post_id)
+    return nil if post.nil?
+
+    {
+        id: post.id,
+        title: post.title,
+        url: post.url,
+        thumbnail_url:
+            if post.thumbnail.attached?
+              Rails.application.routes.url_helpers.rails_storage_proxy_url(
+                  post.thumbnail,
+                  only_path: false)
+            end }
+  end
+end
diff --git a/backend/app/services/post_creator.rb b/backend/app/services/post_creator.rb
index 6d96be8..5da1a07 100644
--- a/backend/app/services/post_creator.rb
+++ b/backend/app/services/post_creator.rb
@@ -10,16 +10,17 @@ class PostCreator
   end
 
   def create!
+    thumbnail_attachment = prepare_thumbnail_attachment
     post = Post.new(title: @attributes[:title].presence,
                     url: @attributes[:url],
                     thumbnail_base: @attributes[:thumbnail_base].presence,
                     uploaded_user: @actor,
                     original_created_from: @attributes[:original_created_from].presence,
                     original_created_before: @attributes[:original_created_before].presence)
-    attach_thumbnail!(post)
 
     ApplicationRecord.transaction do
       post.save!
+      post.thumbnail.attach(thumbnail_attachment) if thumbnail_attachment.present?
       Tag.normalise_tags!(tag_names, deny_deprecated: true, with_sections: true) =>
           { tags:, sections: }
       TagVersioning.record_tag_snapshots!(tags, created_by_user: @actor)
@@ -36,19 +37,10 @@ class PostCreator
 
   private
 
-  def attach_thumbnail! post
-    thumbnail = @attributes[:thumbnail]
-    if thumbnail.present?
-      post.thumbnail.attach(Post.resized_thumbnail_attachment(thumbnail))
-      return
-    end
-
-    thumbnail_base = post.thumbnail_base
-    return if thumbnail_base.blank?
-
-    post.attach_thumbnail_from_url!(thumbnail_base)
-  rescue Post::RemoteThumbnailFetchFailed => e
-    @field_warnings[:thumbnail_base] = [e.message]
+  def prepare_thumbnail_attachment
+    PostThumbnailAttachmentBuilder.build(
+        thumbnail: @attributes[:thumbnail],
+        thumbnail_base: @attributes[:thumbnail_base].presence)
   end
 
   def tag_names = @attributes[:tags].to_s.split
diff --git a/backend/app/services/post_import_previewer.rb b/backend/app/services/post_import_previewer.rb
index 7837896..f0ccc20 100644
--- a/backend/app/services/post_import_previewer.rb
+++ b/backend/app/services/post_import_previewer.rb
@@ -7,6 +7,7 @@ class PostImportPreviewer
     'thumbnail_base',
     'original_created_from',
     'original_created_before',
+    'video_ms',
     'duration',
     'tags',
     'parent_post_ids'].freeze
@@ -162,6 +163,8 @@ class PostImportPreviewer
       normalised =
           if field == 'duration'
             normalise_duration_attribute(value)
+          elsif field == 'video_ms'
+            value.nil? ? '' : value.to_s
           else
             value.to_s
           end
@@ -194,7 +197,7 @@ class PostImportPreviewer
 
   def clear_automatic_values! attributes, provenance, tag_sources
     ['title', 'thumbnail_base', 'original_created_from',
-     'original_created_before', 'duration'].each do |field|
+     'original_created_before', 'video_ms', 'duration'].each do |field|
       attributes[field] = '' if provenance[field] == 'automatic'
     end
     tag_sources['automatic'] = ''
@@ -466,7 +469,7 @@ class PostImportPreviewer
                     thumbnail_base: attributes['thumbnail_base'].presence,
                     original_created_from: attributes['original_created_from'].presence,
                     original_created_before: attributes['original_created_before'].presence,
-                    video_ms: parse_duration(attributes['duration'], errors))
+                    video_ms: parse_video_ms(attributes, errors))
     post.valid?
     post.errors.each do |error|
       next if error.attribute == :url && error.type == :taken
@@ -475,7 +478,19 @@ class PostImportPreviewer
     end
   end
 
-  def parse_duration value, errors
+  def parse_video_ms attributes, errors
+    video_ms = attributes['video_ms']
+    if video_ms.present?
+      value = Integer(video_ms, exception: false)
+      if value&.positive?
+        return value
+      end
+
+      errors[:video_ms] = ['動画時間の記法が不正です．']
+      return nil
+    end
+
+    value = attributes['duration']
     return nil if value.blank?
 
     Tag.time_to_ms!(value.to_s, tag_name: '動画時間')
diff --git a/backend/app/services/post_import_row_normaliser.rb b/backend/app/services/post_import_row_normaliser.rb
deleted file mode 100644
index 7362d3b..0000000
--- a/backend/app/services/post_import_row_normaliser.rb
+++ /dev/null
@@ -1,190 +0,0 @@
-class PostImportRowNormaliser
-  ORIGINS = ['automatic', 'manual'].freeze
-  STRING_FIELDS = [
-    'title',
-    'thumbnail_base',
-    'original_created_from',
-    'original_created_before',
-    'duration',
-    'tags',
-    'parent_post_ids'].freeze
-  FLEXIBLE_FIELDS = ['video_ms'].freeze
-  ATTRIBUTE_FIELDS = (STRING_FIELDS + FLEXIBLE_FIELDS).freeze
-
-  def self.normalise! rows, allow_warning_fields: false
-    raise ArgumentError, '取込行の形式が不正です．' unless rows.is_a?(Array)
-    raise ArgumentError, '取込件数が多すぎます．' if rows.length > PostImportUrlListParser::MAX_ROWS
-
-    normalised_rows = rows.map { normalise_row!(_1, allow_warning_fields:) }
-    source_rows = normalised_rows.map { _1['source_row'] }
-    raise ArgumentError, '元行番号が重複しています．' if source_rows.uniq.length != source_rows.length
-    if normalised_rows.sum { row_bytesize(_1) } > PostImportUrlListParser::MAX_BYTES
-      raise ArgumentError, '取込データが大きすぎます．'
-    end
-
-    normalised_rows
-  end
-
-  def self.normalise_row! row, allow_warning_fields:
-    unless row.is_a?(Hash) || row.is_a?(ActionController::Parameters)
-      raise ArgumentError, '取込行の形式が不正です．'
-    end
-
-    parameters =
-        row.is_a?(ActionController::Parameters) ? row : ActionController::Parameters.new(row)
-    permitted = parameters.permit(*permitted_keys(allow_warning_fields))
-    normalised = permitted.to_h.deep_transform_keys { _1.to_s.underscore }
-
-    normalised['source_row'] = normalise_source_row!(normalised['source_row'])
-    normalise_url!(normalised['url'])
-    normalise_metadata_url!(normalised['metadata_url'])
-    normalise_attributes!(normalised.fetch('attributes', { }))
-    normalise_provenance!(normalised.fetch('provenance', { }))
-    normalise_tag_sources!(normalised['tag_sources'])
-    normalise_warning_values!(normalised, allow_warning_fields:)
-    if row_bytesize(normalised) > PostImportUrlListParser::MAX_BYTES
-      raise ArgumentError, '取込行が大きすぎます．'
-    end
-
-    normalised
-  end
-
-  def self.permitted_keys allow_warning_fields
-    keys = [
-      :source_row,
-      :sourceRow,
-      :url,
-      :metadata_url,
-      :metadataUrl,
-      { attributes: {} },
-      { provenance: {} },
-      { tag_sources: {} },
-      { tagSources: {} }]
-    return keys unless allow_warning_fields
-
-    keys + [
-      { field_warnings: {} },
-      { fieldWarnings: {} },
-      { base_warnings: [] },
-      { baseWarnings: [] }]
-  end
-  private_class_method :permitted_keys
-
-  def self.normalise_source_row! value
-    source_row = Integer(value, exception: false)
-    raise ArgumentError, '元行番号が不正です．' if source_row.nil? || source_row <= 0
-
-    source_row
-  end
-  private_class_method :normalise_source_row!
-
-  def self.normalise_url! value
-    unless value.is_a?(String)
-      raise ArgumentError, 'URL の形式が不正です．'
-    end
-    if value.bytesize > PostImportUrlListParser::MAX_URL_BYTES
-      raise ArgumentError, 'URL が長すぎます．'
-    end
-  end
-  private_class_method :normalise_url!
-
-  def self.normalise_metadata_url! value
-    raise ArgumentError, 'metadata_url の形式が不正です．' unless value.nil? || value.is_a?(String)
-    if value.to_s.bytesize > PostImportUrlListParser::MAX_URL_BYTES
-      raise ArgumentError, 'metadata_url が長すぎます．'
-    end
-  end
-  private_class_method :normalise_metadata_url!
-
-  def self.normalise_attributes! attributes
-    raise ArgumentError, 'attributes の形式が不正です．' unless attributes.is_a?(Hash)
-    raise ArgumentError, '取込項目が不正です．' unless (attributes.keys - ATTRIBUTE_FIELDS).empty?
-
-    attributes.each do |key, value|
-      case key
-      when *STRING_FIELDS
-        raise ArgumentError, '取込項目の型が不正です．' unless value.nil? || value.is_a?(String)
-      when *FLEXIBLE_FIELDS
-        unless value.nil? || value.is_a?(String) || value.is_a?(Numeric)
-          raise ArgumentError, '取込項目の型が不正です．'
-        end
-      end
-      if value.to_s.bytesize > PostImportUrlListParser::MAX_URL_BYTES
-        raise ArgumentError, '取込項目が大きすぎます．'
-      end
-    end
-  end
-  private_class_method :normalise_attributes!
-
-  def self.normalise_provenance! provenance
-    unless provenance.is_a?(Hash)
-      raise ArgumentError, 'provenance の形式が不正です．'
-    end
-
-    allowed = ATTRIBUTE_FIELDS + ['url']
-    unless (provenance.keys - allowed).empty?
-      raise ArgumentError, '値の由来が不正です．'
-    end
-    unless provenance.values.all? { ORIGINS.include?(_1) }
-      raise ArgumentError, '値の由来が不正です．'
-    end
-  end
-  private_class_method :normalise_provenance!
-
-  def self.normalise_tag_sources! tag_sources
-    return if tag_sources.nil?
-
-    unless tag_sources.is_a?(Hash)
-      raise ArgumentError, 'タグ由来の形式が不正です．'
-    end
-    unless (tag_sources.keys - ORIGINS).empty?
-      raise ArgumentError, 'タグ由来の形式が不正です．'
-    end
-    unless tag_sources.values.all? { _1.is_a?(String) }
-      raise ArgumentError, 'タグ由来の形式が不正です．'
-    end
-    if tag_sources.values.any? { _1.bytesize > PostImportUrlListParser::MAX_URL_BYTES }
-      raise ArgumentError, 'タグ由来が大きすぎます．'
-    end
-    if tag_sources.values.sum(&:bytesize) > PostImportUrlListParser::MAX_URL_BYTES
-      raise ArgumentError, 'タグ由来が大きすぎます．'
-    end
-  end
-  private_class_method :normalise_tag_sources!
-
-  def self.normalise_warning_values! normalised, allow_warning_fields:
-    return unless allow_warning_fields
-
-    field_warnings = normalised['field_warnings']
-    unless field_warnings.nil? || field_warnings.is_a?(Hash)
-      raise ArgumentError, '警告の形式が不正です．'
-    end
-    field_warnings&.each do |key, values|
-      unless ATTRIBUTE_FIELDS.include?(key) || key == 'url'
-        raise ArgumentError, '警告の形式が不正です．'
-      end
-      unless values.is_a?(Array) && values.all? { _1.is_a?(String) }
-        raise ArgumentError, '警告の形式が不正です．'
-      end
-      if values.any? { _1.bytesize > PostImportUrlListParser::MAX_URL_BYTES }
-        raise ArgumentError, '警告が大きすぎます．'
-      end
-    end
-
-    base_warnings = normalised['base_warnings']
-    return if base_warnings.nil?
-
-    unless base_warnings.is_a?(Array) && base_warnings.all? { _1.is_a?(String) }
-      raise ArgumentError, '警告の形式が不正です．'
-    end
-    if base_warnings.any? { _1.bytesize > PostImportUrlListParser::MAX_URL_BYTES }
-      raise ArgumentError, '警告が大きすぎます．'
-    end
-  end
-  private_class_method :normalise_warning_values!
-
-  def self.row_bytesize row
-    row.to_json.bytesize
-  end
-  private_class_method :row_bytesize
-end
diff --git a/backend/app/services/post_import_runner.rb b/backend/app/services/post_import_runner.rb
deleted file mode 100644
index 1f53c54..0000000
--- a/backend/app/services/post_import_runner.rb
+++ /dev/null
@@ -1,109 +0,0 @@
-class PostImportRunner
-  def initialize actor:, rows:
-    @actor = actor
-    @rows = rows
-  end
-
-  def run
-    normalised_rows = PostImportRowNormaliser.normalise!(@rows)
-    previews = PostImportPreviewer.new.preview_rows(rows: normalised_rows,
-                                                    fetch_metadata: false)
-    preview_map = previews.index_by { _1[:source_row] }
-
-    results = normalised_rows.map do |row|
-      run_row(row, preview_map.fetch(row['source_row']))
-    end
-
-    { created: results.count { _1[:status] == 'created' },
-      skipped: results.count { _1[:status] == 'skipped' },
-      failed: results.count { _1[:status] == 'failed' },
-      rows: results }
-  end
-
-  private
-
-  def run_row row, preview
-    attributes = row.fetch('attributes', { }).transform_keys { _1.to_s.underscore }
-    return { source_row: row['source_row'],
-             status: 'failed',
-             errors: preview[:validation_errors],
-             recoverable: true } if preview[:validation_errors].present?
-    if preview[:skip_reason] == 'existing'
-      return { source_row: row['source_row'],
-               status: 'skipped',
-               existing_post_id: preview[:existing_post_id] }
-    end
-
-    attributes['tags'] = preview[:attributes]['tags']
-    attributes['url'] = row['url']
-    creator = PostCreator.new(actor: @actor, attributes:)
-    post = creator.create!
-    result = { source_row: row['source_row'], status: 'created', post: PostRepr.base(post) }
-    if creator.field_warnings.present?
-      result[:field_warnings] = creator.field_warnings
-    end
-    result
-  rescue ActiveRecord::RecordInvalid => e
-    existing_post = existing_post_for_race(row, e.record)
-    if existing_post
-      return { source_row: row['source_row'],
-               status: 'skipped',
-               existing_post_id: existing_post.id }
-    end
-
-    { source_row: row['source_row'],
-      status: 'failed',
-      errors: e.record.errors.to_hash,
-      recoverable: true }
-  rescue ActiveRecord::RecordNotUnique => e
-    raise unless url_record_not_unique?(e)
-
-    existing_post = existing_post_for_race(row)
-    raise unless existing_post
-
-    { source_row: row['source_row'],
-      status: 'skipped',
-      existing_post_id: existing_post.id }
-  rescue Tag::NicoTagNormalisationError
-    { source_row: row['source_row'],
-      status: 'failed',
-      errors: { tags: ['ニコニコ・タグは直接指定できません．'] },
-      recoverable: true }
-  rescue Tag::DeprecatedTagNormalisationError
-    { source_row: row['source_row'],
-      status: 'failed',
-      errors: { tags: ['廃止済みタグは付与できません．'] },
-      recoverable: true }
-  rescue PostCreator::VideoMsParseError
-    { source_row: row['source_row'],
-      status: 'failed',
-      errors: { duration: ['動画時間の記法が不正です．'] },
-      recoverable: true }
-  rescue ArgumentError
-    { source_row: row['source_row'],
-      status: 'failed',
-      errors: { base: ['入力値が不正です．'] },
-      recoverable: true }
-  rescue StandardError => e
-    Rails.logger.error("post_import_runner_failure #{ { error: e.class.name,
-                                                        message: e.message }.to_json }")
-    { source_row: row['source_row'],
-      status: 'failed',
-      errors: { base: ['登録中にエラーが発生しました．'] } }
-  end
-
-  def existing_post_for_race row, record = nil
-    if record && !(record.errors.of_kind?(:url, :taken))
-      return nil
-    end
-
-    normal_url = PostUrlNormaliser.normalise(row['url'])
-    return nil if normal_url.blank?
-
-    Post.find_by(url: normal_url)
-  end
-
-  def url_record_not_unique? error
-    error.message.include?('index_posts_on_url')
-  end
-end
diff --git a/backend/app/services/post_thumbnail_attachment_builder.rb b/backend/app/services/post_thumbnail_attachment_builder.rb
new file mode 100644
index 0000000..ad71c91
--- /dev/null
+++ b/backend/app/services/post_thumbnail_attachment_builder.rb
@@ -0,0 +1,11 @@
+class PostThumbnailAttachmentBuilder
+  def self.build thumbnail:, thumbnail_base:
+    if thumbnail_base.present?
+      return Post.remote_thumbnail_attachment(thumbnail_base)
+    end
+
+    return nil if thumbnail.blank?
+
+    Post.resized_thumbnail_attachment(thumbnail)
+  end
+end
diff --git a/backend/config/routes.rb b/backend/config/routes.rb
index cd87bec..d347ecb 100644
--- a/backend/config/routes.rb
+++ b/backend/config/routes.rb
@@ -31,13 +31,6 @@ Rails.application.routes.draw do
   scope :preview, controller: :preview do
     get :title
     get :thumbnail
-    get :image
-  end
-
-  scope 'posts/import', controller: :post_imports do
-    post :preview
-    post :validate
-    post '', action: :create
   end
 
   resources :wiki_pages, path: 'wiki', only: [:index, :show, :create, :update] do
@@ -59,6 +52,8 @@ Rails.application.routes.draw do
 
   resources :posts, only: [:index, :show, :create, :update] do
     collection do
+      get :preview
+      post :bulk
       get :random
       get :changes
       get :versions, to: 'post_versions#index'
diff --git a/frontend/src/components/PostOriginalCreatedTimeField.tsx b/frontend/src/components/PostOriginalCreatedTimeField.tsx
index d0cac09..51e9f61 100644
--- a/frontend/src/components/PostOriginalCreatedTimeField.tsx
+++ b/frontend/src/components/PostOriginalCreatedTimeField.tsx
@@ -24,10 +24,10 @@ const PostOriginalCreatedTimeField: FC<Props> = (
       <FormField label="オリジナルの作成日時" messages={errors}>
 	  {({ describedBy, invalid }) => (
 	      <>
-		<div className="my-1 flex flex-col gap-2 sm:flex-row sm:items-start">
-		  <div className="min-w-0 flex-1">
+		<div className="my-1 flex">
+		  <div className="w-80">
 		    <DateTimeField
-			className="w-full"
+			className="mr-2"
 			disabled={disabled ?? false}
 			aria-describedby={describedBy}
 			aria-invalid={invalid}
@@ -61,10 +61,10 @@ const PostOriginalCreatedTimeField: FC<Props> = (
 		  </div>
 		</div>
 
-		<div className="my-1 flex flex-col gap-2 sm:flex-row sm:items-start">
-		  <div className="min-w-0 flex-1">
+		<div className="my-1 flex">
+		  <div className="w-80">
 		    <DateTimeField
-			className="w-full"
+			className="mr-2"
 			disabled={disabled}
 			aria-describedby={describedBy}
 			aria-invalid={invalid}
diff --git a/frontend/src/components/posts/PostThumbnailPreview.tsx b/frontend/src/components/posts/PostThumbnailPreview.tsx
index 6b2a990..66e64dd 100644
--- a/frontend/src/components/posts/PostThumbnailPreview.tsx
+++ b/frontend/src/components/posts/PostThumbnailPreview.tsx
@@ -7,11 +7,15 @@ import type { FC } from 'react'
 type Props = {
   url:        string
   alt?:       string
-  className?: string }
+  className?: string
+  referrerPolicy?: 'no-referrer' }
 
 
 const PostThumbnailPreview: FC<Props> = (
-    { url, alt = 'サムネール', className = 'h-16 w-16' },
+    { url,
+      alt = 'サムネール',
+      className = 'h-16 w-16',
+      referrerPolicy },
 ) => {
   const [failed, setFailed] = useState (false)
 
@@ -32,6 +36,7 @@ const PostThumbnailPreview: FC<Props> = (
       <img
           src={url}
           alt={alt}
+          referrerPolicy={referrerPolicy}
           className={cn (className, 'rounded border border-border object-cover')}
           onError={() => setFailed (true)}/>)
 }
diff --git a/frontend/src/components/posts/import/PostImportThumbnailPreview.tsx b/frontend/src/components/posts/import/PostImportThumbnailPreview.tsx
index 04caff7..3077db6 100644
--- a/frontend/src/components/posts/import/PostImportThumbnailPreview.tsx
+++ b/frontend/src/components/posts/import/PostImportThumbnailPreview.tsx
@@ -1,7 +1,4 @@
-import { useEffect, useRef, useState } from 'react'
-
 import PostThumbnailPreview from '@/components/posts/PostThumbnailPreview'
-import { apiGet } from '@/lib/api'
 
 import type { FC } from 'react'
 
@@ -15,61 +12,11 @@ const PostImportThumbnailPreview: FC<Props> = (
     { url,
       alt = 'サムネール',
       className = 'h-16 w-16' },
-) => {
-  const [previewUrl, setPreviewUrl] = useState ('')
-  const previewUrlRef = useRef ('')
-
-  useEffect (() => {
-    if (previewUrlRef.current)
-      {
-        URL.revokeObjectURL (previewUrlRef.current)
-        previewUrlRef.current = ''
-      }
-    setPreviewUrl ('')
-
-    if (!(url))
-      return
-
-    const controller = new AbortController ()
-
-    const loadPreview = async () => {
-      try
-      {
-        const blob = await apiGet<Blob> ('/preview/image', {
-            params: { url },
-            signal: controller.signal,
-            responseType: 'blob' })
-        if (controller.signal.aborted)
-          return
-
-        const nextPreviewUrl = URL.createObjectURL (blob)
-        previewUrlRef.current = nextPreviewUrl
-        setPreviewUrl (nextPreviewUrl)
-      }
-      catch
-      {
-        if (!(controller.signal.aborted))
-          setPreviewUrl ('')
-      }
-    }
-
-    void loadPreview ()
-
-    return () => {
-      controller.abort ()
-      if (previewUrlRef.current)
-        {
-          URL.revokeObjectURL (previewUrlRef.current)
-          previewUrlRef.current = ''
-        }
-    }
-  }, [url])
-
-  return (
-      <PostThumbnailPreview
-          url={previewUrl}
-          alt={alt}
-          className={className}/>)
-}
+) => (
+    <PostThumbnailPreview
+        url={url}
+        alt={alt}
+        className={className}
+        referrerPolicy="no-referrer"/>)
 
 export default PostImportThumbnailPreview
diff --git a/frontend/src/lib/postImportStorage.ts b/frontend/src/lib/postImportStorage.ts
index 00e3c89..9e9ae17 100644
--- a/frontend/src/lib/postImportStorage.ts
+++ b/frontend/src/lib/postImportStorage.ts
@@ -6,11 +6,12 @@ import type { PostImportOrigin,
 	      PostImportSkipReason,
 	      StorageErrorHandler } from '@/lib/postImportTypes'
 
-const SESSION_VERSION = 2
+const SESSION_VERSION = 3
 const SESSION_PREFIX = 'post-import-session:'
-const CURRENT_SESSION_KEY = `${ SESSION_PREFIX }current`
 const SOURCE_DRAFT_KEY = 'post-import-source-draft'
 const SESSION_MAX_AGE_MS = 24 * 60 * 60 * 1000
+const SESSION_ID_PATTERN =
+    /^[0-9a-f]{8}-[0-9a-f]{4}-[1-5][0-9a-f]{3}-[89ab][0-9a-f]{3}-[0-9a-f]{12}$/i
 const ATTRIBUTE_KEYS = [
     'title',
     'thumbnailBase',
@@ -29,7 +30,21 @@ const isPlainObject = (value: unknown): value is Record<string, unknown> =>
     typeof value === 'object' && value != null && !(Array.isArray (value))
 
 
-const sessionKey = (): string => CURRENT_SESSION_KEY
+export const validatePostImportSessionId = (value: unknown): string | null => {
+    if (typeof value !== 'string')
+      return null
+    if (value.length > 36 || !(SESSION_ID_PATTERN.test (value)))
+      return null
+
+    return value.toLowerCase ()
+}
+
+
+export const generatePostImportSessionId = (): string =>
+    crypto.randomUUID ()
+
+
+const sessionKey = (sessionId: string): string => `${ SESSION_PREFIX }${ sessionId }`
 
 
 const readStorage = (
@@ -283,9 +298,9 @@ const sanitiseRow = (value: unknown): PostImportRow | null => {
 }
 
 
-const isExpiredSession = (savedAt: string): boolean => {
-    const value = Date.parse (savedAt)
-    return Number.isNaN (value) || Date.now () - value > SESSION_MAX_AGE_MS
+const isExpiredSession = (expiresAt: string): boolean => {
+    const value = Date.parse (expiresAt)
+    return Number.isNaN (value) || value <= Date.now ()
 }
 
 
@@ -303,20 +318,25 @@ export const cleanupExpiredPostImportSessions = (
           if (key == null || !(key.startsWith (SESSION_PREFIX)))
             continue
 
-          const raw = sessionStorage.getItem (key)
-          if (raw == null)
-            continue
-
-          if (key !== CURRENT_SESSION_KEY)
+          const sessionId = validatePostImportSessionId (key.slice (SESSION_PREFIX.length))
+          if (sessionId == null)
             {
               sessionStorage.removeItem (key)
               --i
               continue
             }
+
+          const raw = sessionStorage.getItem (key)
+          if (raw == null)
+            continue
+
           try
           {
-            const value = JSON.parse (raw) as { savedAt?: string }
-            if (typeof value.savedAt !== 'string' || isExpiredSession (value.savedAt))
+            const value = JSON.parse (raw) as { expiresAt?: string
+						rows?: unknown[] }
+            if (typeof value.expiresAt !== 'string'
+                || isExpiredSession (value.expiresAt)
+                || !(Array.isArray (value.rows)))
               {
                 sessionStorage.removeItem (key)
                 --i
@@ -370,38 +390,33 @@ export const clearPostImportSourceDraft = (
 
 
 export const savePostImportSession = (
-    sessionOrLegacyId: string | Omit<PostImportSession, 'version' | 'savedAt'>,
-    sessionOrOnError?: Omit<PostImportSession, 'version' | 'savedAt'> | StorageErrorHandler,
+    sessionId: string,
+    session: Omit<PostImportSession, 'version' | 'expiresAt'>,
     onError?:  StorageErrorHandler,
 ): boolean => {
-    const session =
-        typeof sessionOrLegacyId === 'string'
-        ? sessionOrOnError as Omit<PostImportSession, 'version' | 'savedAt'>
-        : sessionOrLegacyId
-    const errorHandler =
-        typeof sessionOrLegacyId === 'string'
-        ? onError
-        : sessionOrOnError as StorageErrorHandler | undefined
+    const validatedId = validatePostImportSessionId (sessionId)
+    if (validatedId == null)
+      return false
 
     return writeStorage (
-        sessionKey (),
+        sessionKey (validatedId),
         JSON.stringify ({
             ...session,
             version: SESSION_VERSION,
-            savedAt: new Date ().toISOString () }),
-        errorHandler)
+            expiresAt: new Date (Date.now () + SESSION_MAX_AGE_MS).toISOString () }),
+        onError)
 }
 
 
 export const loadPostImportSession = (
-    legacyIdOrOnError?: string | StorageErrorHandler,
+    sessionId: string,
     onError?: StorageErrorHandler,
 ): PostImportSession | null => {
-    const errorHandler =
-        typeof legacyIdOrOnError === 'string'
-        ? onError
-        : legacyIdOrOnError
-    const raw = readStorage (sessionKey (), errorHandler)
+    const validatedId = validatePostImportSessionId (sessionId)
+    if (validatedId == null)
+      return null
+
+    const raw = readStorage (sessionKey (validatedId), onError)
     if (raw == null)
       return null
 
@@ -410,9 +425,9 @@ export const loadPostImportSession = (
       const value = JSON.parse (raw) as Partial<PostImportSession>
       if (value.version !== SESSION_VERSION || !(Array.isArray (value.rows)))
         return null
-      if (typeof value.savedAt !== 'string' || isExpiredSession (value.savedAt))
+      if (typeof value.expiresAt !== 'string' || isExpiredSession (value.expiresAt))
         {
-          removeStorage (sessionKey (), errorHandler)
+          removeStorage (sessionKey (validatedId), onError)
           return null
         }
 
@@ -422,7 +437,7 @@ export const loadPostImportSession = (
 
       return {
           version: SESSION_VERSION,
-          savedAt: value.savedAt,
+          expiresAt: value.expiresAt,
           source: typeof value.source === 'string' ? value.source : '',
           rows: rows as PostImportRow[],
           repairMode: value.repairMode === 'failed' ? 'failed' : 'all' }
@@ -435,7 +450,12 @@ export const loadPostImportSession = (
 
 
 export const clearPostImportSession = (
+    sessionId: string,
     onError?: StorageErrorHandler,
 ) => {
-    removeStorage (sessionKey (), onError)
+    const validatedId = validatePostImportSessionId (sessionId)
+    if (validatedId == null)
+      return
+
+    removeStorage (sessionKey (validatedId), onError)
 }
diff --git a/frontend/src/lib/postImportTypes.ts b/frontend/src/lib/postImportTypes.ts
index 632a945..e707085 100644
--- a/frontend/src/lib/postImportTypes.ts
+++ b/frontend/src/lib/postImportTypes.ts
@@ -35,7 +35,9 @@ export type PostImportRow = {
     resetSnapshot:     PostImportResetSnapshot
     createdPostId?:    number
     importStatus?:     PostImportStatus
-    recoverable?:      boolean }
+    recoverable?:      boolean
+    thumbnailFile?:    File
+    thumbnailObjectUrl?: string }
 
 export type PostImportResultRow =
     | {
@@ -61,11 +63,11 @@ export type PostImportResultRow =
 	recoverable?: boolean }
 
 export type PostImportSession = {
-    version:    number
-    savedAt:    string
-    source:     string
-    rows:       PostImportRow[]
-    repairMode: PostImportRepairMode }
+    version:     number
+    expiresAt:   string
+    source:      string
+    rows:        PostImportRow[]
+    repairMode:  PostImportRepairMode }
 
 export type PostImportSourceIssue = {
     sourceRow: number
diff --git a/frontend/src/lib/postNewQueryState.ts b/frontend/src/lib/postNewQueryState.ts
index c07a3cb..413fd16 100644
--- a/frontend/src/lib/postNewQueryState.ts
+++ b/frontend/src/lib/postNewQueryState.ts
@@ -1,4 +1,5 @@
 import { resultRepairMode } from '@/lib/postImportRows'
+import { validatePostImportSessionId } from '@/lib/postImportStorage'
 
 import type {
     PostImportOrigin,
@@ -12,6 +13,7 @@ type QueryRowState = {
   thumbnail_base:          string
   original_created_from:   string
   original_created_before: string
+  video_ms:                string
   duration:                string
   tags:                    string
   parent_post_ids:         string
@@ -37,6 +39,7 @@ type EncodedRowState = {
   h?: string
   f?: string
   b?: string
+  x?: string
   d?: string
   g?: string
   p?: string
@@ -58,8 +61,8 @@ export type ParsedPostNewState = {
   shortcut:   boolean }
 
 export type SerialisedPostNewState = {
-  path: string
-  rows: PostImportRow[] }
+  path:     string
+  complete: boolean }
 
 const BASIC_KEYS = [
     'url',
@@ -67,6 +70,7 @@ const BASIC_KEYS = [
     'thumbnail_base',
     'original_created_from',
     'original_created_before',
+    'video_ms',
     'duration',
     'tags',
     'parent_post_ids'] as const
@@ -77,7 +81,7 @@ const STATE_KEYS = [
     'import_status',
     'created_post_id',
     'recoverable'] as const
-const SINGLE_ROW_KEYS = [...BASIC_KEYS, ...STATE_KEYS] as const
+const SINGLE_ROW_KEYS = [...BASIC_KEYS, ...STATE_KEYS, 'session_id'] as const
 const MAX_REGULAR_URL_LENGTH = 768
 const MAX_COMPRESSED_STATE_LENGTH = 767
 const COMPRESSED_STATE_PREFIX = 'z1.'
@@ -241,6 +245,7 @@ const baseRowState = (row: PostImportRow): QueryRowState => ({
     thumbnail_base: String (row.attributes.thumbnailBase ?? ''),
     original_created_from: String (row.attributes.originalCreatedFrom ?? ''),
     original_created_before: String (row.attributes.originalCreatedBefore ?? ''),
+    video_ms: String (row.attributes.videoMs ?? ''),
     duration: String (row.attributes.duration ?? ''),
     tags: String (row.attributes.tags ?? ''),
     parent_post_ids: String (row.attributes.parentPostIds ?? ''),
@@ -263,6 +268,7 @@ const buildRow = (
       thumbnailBase: manual.has ('thumbnailBase') ? 'manual' : 'automatic',
       originalCreatedFrom: manual.has ('originalCreatedFrom') ? 'manual' : 'automatic',
       originalCreatedBefore: manual.has ('originalCreatedBefore') ? 'manual' : 'automatic',
+      videoMs: 'automatic',
       duration: 'automatic',
       tags: manual.has ('tags') ? 'manual' : 'automatic',
       parentPostIds: manual.has ('parentPostIds') ? 'manual' : 'automatic' }
@@ -274,6 +280,7 @@ const buildRow = (
       thumbnailBase: state.thumbnail_base,
       originalCreatedFrom: state.original_created_from,
       originalCreatedBefore: state.original_created_before,
+      videoMs: state.video_ms,
       duration: state.duration,
       tags: state.tags,
       parentPostIds: state.parent_post_ids }
@@ -356,6 +363,7 @@ const parseEncodedRow = (
       ['h', 'thumbnail_base'],
       ['f', 'original_created_from'],
       ['b', 'original_created_before'],
+      ['x', 'video_ms'],
       ['d', 'duration'],
       ['g', 'tags'],
       ['p', 'parent_post_ids']] as const
@@ -382,6 +390,7 @@ const parseEncodedRow = (
       thumbnail_base: parsedStrings.thumbnail_base,
       original_created_from: parsedStrings.original_created_from,
       original_created_before: parsedStrings.original_created_before,
+      video_ms: parsedStrings.video_ms,
       duration: parsedStrings.duration,
       tags: parsedStrings.tags,
       parent_post_ids: parsedStrings.parent_post_ids,
@@ -399,7 +408,8 @@ const parseSingleRow = (params: URLSearchParams): ParsedPostNewState | null => {
   if (url == null || url === '')
     return null
 
-  const hasOnlyUrl = Array.from (params.keys ()).every (key => key === 'url')
+  const hasOnlyUrl = Array.from (params.keys ()).every (
+      key => key === 'url' || key === 'session_id')
   if (hasOnlyUrl)
     {
       const row = buildRow (1, {
@@ -408,6 +418,7 @@ const parseSingleRow = (params: URLSearchParams): ParsedPostNewState | null => {
 	  thumbnail_base: '',
 	  original_created_from: '',
 	  original_created_before: '',
+	  video_ms: '',
 	  duration: '',
 	  tags: '',
 	  parent_post_ids: '',
@@ -444,6 +455,7 @@ const parseSingleRow = (params: URLSearchParams): ParsedPostNewState | null => {
       thumbnail_base: params.get ('thumbnail_base') ?? '',
       original_created_from: params.get ('original_created_from') ?? '',
       original_created_before: params.get ('original_created_before') ?? '',
+      video_ms: params.get ('video_ms') ?? '',
       duration: params.get ('duration') ?? '',
       tags: params.get ('tags') ?? '',
       parent_post_ids: params.get ('parent_post_ids') ?? '',
@@ -546,6 +558,7 @@ const regularQuery = (rows: PostImportRow[]): URLSearchParams => {
       params.set ('thumbnail_base', String (row?.attributes.thumbnailBase ?? ''))
       params.set ('original_created_from', String (row?.attributes.originalCreatedFrom ?? ''))
       params.set ('original_created_before', String (row?.attributes.originalCreatedBefore ?? ''))
+      params.set ('video_ms', String (row?.attributes.videoMs ?? ''))
       params.set ('duration', String (row?.attributes.duration ?? ''))
       params.set ('tags', String (row?.attributes.tags ?? ''))
       params.set ('parent_post_ids', String (row?.attributes.parentPostIds ?? ''))
@@ -589,6 +602,8 @@ const encodeRowState = (
     encoded.f = base.original_created_from
   if (base.original_created_before !== '')
     encoded.b = base.original_created_before
+  if (base.video_ms !== '')
+    encoded.x = base.video_ms
   if (base.duration !== '')
     encoded.d = base.duration
   if (base.tags !== '')
@@ -626,6 +641,24 @@ export const hasPostNewReviewState = (search: string): boolean => {
 }
 
 
+export const parsePostNewSessionId = (search: string): string | null =>
+    validatePostImportSessionId (
+        new URLSearchParams (search).get ('session_id'))
+
+
+export const appendPostNewSessionId = (
+    path:       string,
+    sessionId:  string,
+): string => {
+  const validatedId = validatePostImportSessionId (sessionId)
+  if (validatedId == null)
+    return path
+
+  const separator = path.includes ('?') ? '&' : '?'
+  return `${ path }${ separator }session_id=${ validatedId }`
+}
+
+
 export const parsePostNewState = async (
     search: string,
 ): Promise<ParsedPostNewState | null> => {
@@ -661,7 +694,7 @@ const serialiseCompressedRows = async (
 	  if (payload.length <= MAX_COMPRESSED_STATE_LENGTH)
 	    return {
 		path: `/posts/new?state=${ state }`,
-		rows: nextRows }
+		complete: count === rows.length }
 	}
     }
   catch
@@ -680,7 +713,7 @@ export const serialisePostNewState = async (
   if (regularPath.length < MAX_REGULAR_URL_LENGTH)
     return {
 	path: regularPath,
-	rows }
+	complete: true }
 
   return await serialiseCompressedRows (rows)
 }
diff --git a/frontend/src/pages/posts/PostImportResultPage.tsx b/frontend/src/pages/posts/PostImportResultPage.tsx
deleted file mode 100644
index 7521565..0000000
--- a/frontend/src/pages/posts/PostImportResultPage.tsx
+++ /dev/null
@@ -1,544 +0,0 @@
-import { useEffect, useMemo, useRef, useState } from 'react'
-import { Helmet } from 'react-helmet-async'
-import { useNavigate, useParams } from 'react-router-dom'
-
-import FieldError from '@/components/common/FieldError'
-import FieldWarning from '@/components/common/FieldWarning'
-import PageTitle from '@/components/common/PageTitle'
-import PrefetchLink from '@/components/PrefetchLink'
-import MainArea from '@/components/layout/MainArea'
-import PostImportRowForm from '@/components/posts/import/PostImportRowForm'
-import PostImportStatusBadge from '@/components/posts/import/PostImportStatusBadge'
-import { displayPostImportStatus } from '@/components/posts/import/postImportRowStatus'
-import { Button } from '@/components/ui/button'
-import { toast } from '@/components/ui/use-toast'
-import { SITE_TITLE } from '@/config'
-import { apiPost } from '@/lib/api'
-import useDialogue from '@/lib/dialogues/useDialogue'
-import { canEditContent } from '@/lib/users'
-import { clearPostImportSourceDraft,
-	 buildNextEditedRow,
-	 canEditResultRow,
-	 canRetryResultRow,
-	 hasExactSourceRows,
-	 initialisePreviewRows,
-	 loadPostImportSession,
-	 mergeImportResults,
-	 mergeValidatedImportRow,
-	 replaceImportRow,
-	 resultRepairMode,
-	 resultRowMessages,
-	 resultRowWarnings,
-	 resultSummaryCounts,
-	 retryImportRow,
-	 savePostImportSession } from '@/lib/postImportSession'
-import { originalCreatedAtString } from '@/lib/utils'
-import Forbidden from '@/pages/Forbidden'
-
-import type { FC } from 'react'
-
-import type { PostImportRowDraft } from '@/components/posts/import/PostImportRowForm'
-import type { PostImportResultRow, PostImportRow } from '@/lib/postImportSession'
-import type { PostImportSession } from '@/lib/postImportSession'
-import type { User } from '@/types'
-
-type Props = { user: User | null }
-
-
-const PostImportResultPage: FC<Props> = ({ user }) => {
-  const editable = canEditContent (user)
-  const dialogue = useDialogue ()
-  const navigate = useNavigate ()
-  const { sessionId } = useParams ()
-
-  const [session, setSession] = useState<PostImportSession | null> (null)
-  const [missing, setMissing] = useState (false)
-  const [loadingRow, setLoadingRow] = useState<number | null> (null)
-  const [, setEditingRow] = useState<PostImportRow | null> (null)
-  const sessionRef = useRef<PostImportSession | null> (null)
-
-  useEffect (() => {
-    if (sessionId == null)
-      return
-
-    const loaded = loadPostImportSession (sessionId, message =>
-	toast ({ title: '取込状態を復元できませんでした', description: message }))
-    setSession (loaded)
-    setMissing (loaded == null)
-  }, [sessionId])
-
-  useEffect (() => {
-    if (sessionId == null || session == null)
-      return
-
-    savePostImportSession (sessionId, session, message =>
-	toast ({ title: '取込状態を保存できませんでした', description: message }))
-  }, [session, sessionId])
-
-  useEffect (() => {
-    sessionRef.current = session
-  }, [session])
-
-  const counts = useMemo (
-      () => resultSummaryCounts (session?.rows ?? []),
-      [session])
-  const busy = loadingRow != null
-
-  const persistSession = (nextSession: PostImportSession) => {
-    if (sessionId == null)
-      return
-
-    savePostImportSession (sessionId, nextSession, message =>
-        toast ({ title: '取込状態を保存できませんでした', description: message }))
-  }
-
-  const saveDraft = async (
-      row: PostImportRow,
-      { draft, resetRequested }: {
-	  draft:            PostImportRowDraft
-	  resetRequested:   boolean },
-  ): Promise<{ saved: boolean
-	       row:   PostImportRow | null }> => {
-    const currentSession = sessionRef.current
-    if (currentSession == null)
-      return { saved: false, row: null }
-    if (!(canEditResultRow (row)))
-      return { saved: false, row: null }
-
-    const baseRow =
-	resetRequested
-	? { ...row,
-	    url: row.resetSnapshot.url,
-	    attributes: { ...row.resetSnapshot.attributes },
-	    provenance: { ...row.resetSnapshot.provenance },
-	    tagSources: { ...row.resetSnapshot.tagSources },
-	    fieldWarnings: Object.fromEntries (
-		Object.entries (row.resetSnapshot.fieldWarnings)
-		    .map (([key, values]) => [key, [...values]])),
-	    baseWarnings: [...row.resetSnapshot.baseWarnings],
-	    metadataUrl: row.resetSnapshot.metadataUrl }
-	: row
-    const urlChanged = draft.url !== baseRow.url
-    const nextRow = buildNextEditedRow (baseRow, draft, urlChanged)
-
-    const nextRows = currentSession.rows.map (row =>
-		row.sourceRow === baseRow.sourceRow
-		? nextRow
-		: row)
-    try
-    {
-      const validated = await apiPost<{ rows: PostImportRow[] }> ('/posts/import/validate', {
-	  rows:
-	      nextRows
-	      .filter (row => row.importStatus !== 'created')
-	      .map (row => ({ sourceRow: row.sourceRow,
-			      url: row.url,
-			      attributes: row.attributes,
-			      provenance: row.provenance,
-			      tagSources: row.tagSources,
-			      metadataUrl: row.metadataUrl })),
-	  changed_row: urlChanged ? baseRow.sourceRow : -1 })
-      const validatedRows = initialisePreviewRows (validated.rows)
-      const target = validatedRows.find (
-          validatedRow => validatedRow.sourceRow === baseRow.sourceRow)
-      const latestSession = sessionRef.current
-      if (latestSession == null)
-        return { saved: false, row: null }
-      if (target == null)
-        {
-          const restoredRows = replaceImportRow (latestSession.rows, row)
-          const restoredSession = {
-              ...latestSession,
-              rows: restoredRows,
-              repairMode: resultRepairMode (restoredRows) }
-          sessionRef.current = restoredSession
-          setSession (restoredSession)
-          toast ({ title: '行の再検証結果が不完全でした' })
-          return { saved: false, row: null }
-        }
-      const editedRows = replaceImportRow (latestSession.rows, nextRow)
-      const rows = mergeValidatedImportRow (editedRows, target)
-      const nextSession = {
-          ...latestSession,
-          rows,
-          repairMode: resultRepairMode (rows) }
-      sessionRef.current = nextSession
-      setSession (nextSession)
-      persistSession (nextSession)
-      const mergedTarget =
-          rows.find (mergedRow => mergedRow.sourceRow === baseRow.sourceRow)
-          ?? target
-      if (Object.keys (mergedTarget.validationErrors).length > 0)
-        return { saved: false, row: mergedTarget }
-      return { saved: true, row: null }
-    }
-    catch
-    {
-      toast ({ title: '行の再検証に失敗しました' })
-      return { saved: false, row: null }
-    }
-  }
-
-  const openEditingDialogue = async (row: PostImportRow) => {
-    const saveRowDraft = (
-	{ draft, resetRequested }: {
-	    draft:          PostImportRowDraft
-	    resetRequested: boolean },
-    ) =>
-	saveDraft (row, { draft, resetRequested })
-
-    await dialogue.form ({
-	title: '投稿を編輯',
-	description: `投稿 ${ row.sourceRow } の内容を確認し、必要な項目を編輯してください．`,
-	cancelText: '取消',
-	size: 'large',
-	body: controls => (
-	    <PostImportRowForm
-		row={row}
-		controls={controls}
-		onSave={saveRowDraft}/>) })
-  }
-
-  const editRow = async (row: PostImportRow) => {
-    setEditingRow (row)
-    try
-    {
-      await openEditingDialogue (row)
-    }
-    finally
-    {
-      setEditingRow (current =>
-          current?.sourceRow === row.sourceRow
-          ? null
-          : current)
-    }
-  }
-
-  const retry = async (sourceRow: number) => {
-    if (session == null || sessionId == null || loadingRow != null)
-      return
-
-    const initialSession = sessionRef.current
-    if (initialSession == null)
-      return
-
-    setLoadingRow (sourceRow)
-    const originalRow = initialSession.rows.find (row => row.sourceRow === sourceRow)
-    if (originalRow == null)
-      {
-        setLoadingRow (null)
-        return
-      }
-    try
-    {
-      const pendingRows = retryImportRow (initialSession.rows, sourceRow)
-      const pendingSession = { ...initialSession, rows: pendingRows }
-      sessionRef.current = pendingSession
-      setSession (pendingSession)
-      persistSession (pendingSession)
-      const requestedRows = pendingRows.filter (row => row.importStatus !== 'created')
-      const validated = await apiPost<{ rows: PostImportRow[] }> ('/posts/import/validate', {
-          rows: requestedRows.map (row => ({
-                  sourceRow: row.sourceRow,
-                  url: row.url,
-                  attributes: row.attributes,
-                  provenance: row.provenance,
-                  tagSources: row.tagSources,
-                  metadataUrl: row.metadataUrl })),
-          changed_row: -1 })
-      const validatedRows = initialisePreviewRows (validated.rows)
-      if (!(hasExactSourceRows (requestedRows.map (row => row.sourceRow), validatedRows)))
-        {
-          const latest = sessionRef.current ?? pendingSession
-          const restoredRows = replaceImportRow (latest.rows, originalRow)
-          const restoredSession = {
-              ...latest,
-              rows: restoredRows,
-              repairMode: resultRepairMode (restoredRows) }
-          sessionRef.current = restoredSession
-          setSession (restoredSession)
-          persistSession (restoredSession)
-          toast ({ title: '再検証結果が不完全でした' })
-          return
-        }
-      const validatedTarget = validatedRows.find (
-          row => row.sourceRow === sourceRow)
-      if (validatedTarget == null)
-        {
-          const latest = sessionRef.current ?? pendingSession
-          const restoredRows = replaceImportRow (latest.rows, originalRow)
-          const restoredSession = {
-              ...latest,
-              rows: restoredRows,
-              repairMode: resultRepairMode (restoredRows) }
-          sessionRef.current = restoredSession
-          setSession (restoredSession)
-          persistSession (restoredSession)
-          toast ({ title: '再検証結果が不完全でした' })
-          return
-        }
-      const latestAfterValidate = sessionRef.current ?? pendingSession
-      const mergedValidatedRows = mergeValidatedImportRow (
-          latestAfterValidate.rows,
-          validatedTarget)
-      const nextSession = {
-          ...latestAfterValidate,
-          rows: mergedValidatedRows,
-          repairMode: resultRepairMode (mergedValidatedRows) }
-      sessionRef.current = nextSession
-      setSession (nextSession)
-      persistSession (nextSession)
-      const target = mergedValidatedRows.find (row => row.sourceRow === sourceRow)
-      if (target == null)
-        {
-          const restoredRows = replaceImportRow (latestAfterValidate.rows, originalRow)
-          const restoredSession = {
-              ...latestAfterValidate,
-              rows: restoredRows,
-              repairMode: resultRepairMode (restoredRows) }
-          sessionRef.current = restoredSession
-          setSession (restoredSession)
-          persistSession (restoredSession)
-          toast ({ title: '再検証結果が不完全でした' })
-          return
-        }
-      if (Object.keys (target.validationErrors ?? { }).length > 0)
-        {
-          const saved = savePostImportSession (sessionId, nextSession, message =>
-              toast ({ title: '取込状態を保存できませんでした', description: message }))
-          if (saved)
-            void editRow (target)
-          return
-        }
-
-      const result = await apiPost<{
-          created: number
-          skipped: number
-          failed:  number
-          rows:    PostImportResultRow[] }> ('/posts/import', {
-              rows: [{
-                  sourceRow: target.sourceRow,
-                  url: target.url,
-                  attributes: target.attributes,
-                  provenance: target.provenance,
-                  tagSources: target.tagSources,
-                  metadataUrl: target.metadataUrl }] })
-      if (!(hasExactSourceRows ([sourceRow], result.rows)))
-        {
-          const latest = sessionRef.current ?? nextSession
-          const restoredRows = replaceImportRow (latest.rows, originalRow)
-          const restoredSession = {
-              ...latest,
-              rows: restoredRows,
-              repairMode: resultRepairMode (restoredRows) }
-          sessionRef.current = restoredSession
-          setSession (restoredSession)
-          persistSession (restoredSession)
-          toast ({ title: '登録結果が不完全でした' })
-          return
-        }
-      const latestAfterImport = sessionRef.current ?? nextSession
-      const mergedRows = mergeImportResults (latestAfterImport.rows, result.rows)
-      const recoverableRows = result.rows.filter (row =>
-          row.status === 'failed'
-          && row.recoverable
-          && Object.keys (row.errors ?? { }).length > 0)
-      const nextRows = mergedRows.map ((row): PostImportRow => {
-        const recoverable = recoverableRows.find (
-            recoverableRow => recoverableRow.sourceRow === row.sourceRow)
-        if (recoverable == null)
-          return row
-        return {
-            ...row,
-            importStatus: 'pending',
-            recoverable: true,
-            validationErrors: recoverable.errors ?? { },
-            importErrors: undefined }
-      })
-      const recoverableTarget = nextRows.find (row => row.sourceRow === sourceRow)
-      const resultSession = {
-          ...nextSession,
-          rows: nextRows,
-          repairMode: resultRepairMode (nextRows) }
-      sessionRef.current = resultSession
-      setSession (resultSession)
-      persistSession (resultSession)
-      if (recoverableTarget != null
-          && Object.keys (recoverableTarget.validationErrors).length > 0)
-        {
-          const saved = savePostImportSession (sessionId, resultSession, message =>
-              toast ({ title: '取込状態を保存できませんでした', description: message }))
-          if (saved)
-            void editRow (recoverableTarget)
-          return
-        }
-    }
-    catch
-    {
-      const latest = sessionRef.current
-      if (latest != null)
-        {
-          const restoredRows = replaceImportRow (latest.rows, originalRow)
-          const restoredSession = {
-              ...latest,
-              rows: restoredRows,
-              repairMode: resultRepairMode (restoredRows) }
-          sessionRef.current = restoredSession
-          setSession (restoredSession)
-          persistSession (restoredSession)
-        }
-      toast ({ title: '再試行に失敗しました' })
-    }
-    finally
-    {
-      setLoadingRow (null)
-    }
-  }
-
-  const openRepair = (sourceRow: number) => {
-    const currentSession = sessionRef.current
-    if (currentSession == null || sessionId == null || loadingRow != null)
-      return
-
-    const nextSession = { ...currentSession, repairMode: 'failed' as const }
-    sessionRef.current = nextSession
-    setSession (nextSession)
-    const saved = savePostImportSession (sessionId, nextSession, message =>
-	toast ({ title: '取込状態を保存できませんでした', description: message }))
-    if (!(saved))
-      return
-    const row = nextSession.rows.find (rowValue => rowValue.sourceRow === sourceRow)
-    if (row != null)
-      void editRow (row)
-  }
-
-  if (!(editable))
-    return <Forbidden/>
-
-  if (missing || sessionId == null || session == null)
-    {
-      return (
-	  <MainArea>
-	    <div className="mx-auto max-w-4xl space-y-4 p-4">
-	      <PageTitle>投稿インポート結果</PageTitle>
-	      <FieldError messages={['取込状態が見つかりません．']}/>
-	      <Button type="button" onClick={() => navigate ('/posts/import')}>
-		URL リスト入力へ戻る
-	      </Button>
-	    </div>
-	  </MainArea>)
-    }
-
-  return (
-      <MainArea>
-	<Helmet>
-	  <title>{`投稿インポート結果 | ${ SITE_TITLE }`}</title>
-	</Helmet>
-
-	<div className="mx-auto max-w-5xl space-y-4 p-4">
-	  <PageTitle>登録結果</PageTitle>
-
-	  <div className="text-sm text-neutral-700 dark:text-neutral-200">
-	    登録成功 {counts.created}件　スキップ {counts.skipped}件　失敗 {counts.failed}件
-	  </div>
-
-	  <div className="space-y-3">
-	    {session.rows.map (row => {
-	      const displayStatus = displayPostImportStatus (row)
-	      const canEdit = canEditResultRow (row)
-	      const canRetry = canRetryResultRow (row)
-	      return (
-		  <div
-		      key={row.sourceRow}
-		      className="rounded-lg border p-4 transition-shadow hover:shadow-sm">
-		    <div className="flex flex-col gap-3 md:flex-row md:items-start
-				    md:justify-between">
-		      <div className="space-y-2">
-			<div className="flex flex-wrap items-center gap-2">
-			  <span className="text-sm font-medium">行 {row.sourceRow}</span>
-			  {displayStatus != null && <PostImportStatusBadge value={displayStatus}/>}
-			</div>
-			<div className="text-sm text-neutral-700 dark:text-neutral-200">
-			  {String (row.attributes.title ?? '') || row.url}
-			</div>
-			<div className="text-xs text-neutral-500 dark:text-neutral-400">
-			  {row.url}
-			</div>
-			<div className="text-xs text-neutral-500 dark:text-neutral-400">
-			  {String (row.attributes.tags ?? '') || 'タグなし'}
-			</div>
-			<div className="text-xs text-neutral-500 dark:text-neutral-400">
-			  {originalCreatedAtString (
-			      row.attributes.originalCreatedFrom?.toString () ?? null,
-			      row.attributes.originalCreatedBefore?.toString () ?? null)}
-			  {row.attributes.duration ? ` / ${ row.attributes.duration }` : ''}
-			</div>
-			<FieldWarning messages={resultRowWarnings (row)}/>
-			<FieldError messages={resultRowMessages (row)}/>
-		      </div>
-
-		      <div className="flex flex-col gap-2 sm:flex-row">
-			{(row.createdPostId != null || row.existingPostId != null) && (
-			    <Button type="button" variant="outline" asChild>
-			      <PrefetchLink
-				  to={`/posts/${ row.createdPostId ?? row.existingPostId }`}>
-				投稿を開く
-			      </PrefetchLink>
-			    </Button>)}
-			{canEdit && (
-			    <Button
-				type="button"
-				variant="outline"
-				onClick={() => openRepair (row.sourceRow)}
-				disabled={busy}>
-			      編輯
-			    </Button>)}
-			{canRetry && (
-			    <Button
-				type="button"
-				onClick={() => retry (row.sourceRow)}
-				disabled={busy}>
-			      再試行
-			    </Button>)}
-		      </div>
-		    </div>
-		  </div>)})}
-	    </div>
-
-	    <div className="flex flex-col gap-2 sm:flex-row">
-	      <Button
-		  type="button"
-		  variant="outline"
-		  disabled={busy}
-		  onClick={() => {
-		      const currentSession = sessionRef.current
-		      if (currentSession == null)
-			return
-		      const nextSession = { ...currentSession, repairMode: 'all' as const }
-		      sessionRef.current = nextSession
-		      setSession (nextSession)
-		      const saved = savePostImportSession (sessionId, nextSession, message =>
-			  toast ({ title: '取込状態を保存できませんでした', description: message }))
-		      if (!(saved))
-			return
-		      navigate (`/posts/import/${ sessionId }/review`)
-		  }}>
-		確認画面へ戻る
-	      </Button>
-	      <Button
-		  type="button"
-		  variant="outline"
-		  disabled={busy}
-		  onClick={() => {
-		      clearPostImportSourceDraft (message =>
-			  toast ({ title: '入力内容を削除できませんでした', description: message }))
-		      navigate ('/posts/import')
-		  }}>
-		新しい URL リストを入力
-	      </Button>
-	    </div>
-	  </div>
-	</MainArea>)
-}
-
-export default PostImportResultPage
diff --git a/frontend/src/pages/posts/PostImportReviewPage.tsx b/frontend/src/pages/posts/PostImportReviewPage.tsx
index ef24c8a..b2616ad 100644
--- a/frontend/src/pages/posts/PostImportReviewPage.tsx
+++ b/frontend/src/pages/posts/PostImportReviewPage.tsx
@@ -13,33 +13,35 @@ import PostImportRowSummary from '@/components/posts/import/PostImportRowSummary
 import { Button } from '@/components/ui/button'
 import { toast } from '@/components/ui/use-toast'
 import { SITE_TITLE } from '@/config'
-import { apiPost } from '@/lib/api'
+import { apiGet, apiPost, isApiError } from '@/lib/api'
 import useDialogue from '@/lib/dialogues/useDialogue'
 import { fetchPost } from '@/lib/posts'
 import {
+    appendPostNewSessionId,
     parsePostNewState,
+    parsePostNewSessionId,
     serialisePostNewState,
 } from '@/lib/postNewQueryState'
 import {
     buildNextEditedRow,
     canEditReviewRow,
     canRetryResultRow,
+    clearPostImportSession,
     clearPostImportSourceDraft,
-    hasExactSourceRows,
+    generatePostImportSessionId,
     initialisePreviewRows,
     isCompletedReviewRow,
     isExistingSkipRow,
     isNonRecoverableFailedRow,
     mergeImportResults,
-    mergeValidatedImportRow,
-    mergeValidatedImportRows,
     processableImportRows,
     replaceImportRow,
     resultRepairMode,
     resultRowMessages,
     reviewSummaryCounts,
     retryImportRow,
-    validatableImportRows,
+    savePostImportSession,
+    loadPostImportSession,
 } from '@/lib/postImportSession'
 import { postsKeys } from '@/lib/queryKeys'
 import { useClientBehaviourSettings } from '@/lib/useClientBehaviourSettings'
@@ -58,6 +60,29 @@ import type { Post, User } from '@/types'
 
 type Props = { user: User | null }
 
+type PreviewResponse = {
+  url:                   string
+  title?:                string
+  thumbnailBase?:        string
+  originalCreatedFrom?:  string
+  originalCreatedBefore?: string
+  duration?:             string
+  videoMs?:              number
+  tags?:                 string
+  fieldWarnings?:        Record<string, string[]>
+  baseWarnings?:         string[]
+  existingPost?:         { id: number } | null }
+
+type BulkApiRow = {
+  status:        'created' | 'skipped' | 'failed'
+  post?:         { id: number }
+  existingPost?: { id: number } | null
+  fieldWarnings?: Record<string, string[]>
+  baseWarnings?: string[]
+  errors?:       Record<string, string[]>
+  baseErrors?:   string[]
+  recoverable?:  boolean }
+
 type ExistingSkippedRowsProps = {
   open:  boolean
   rows:   PostImportRow[] }
@@ -70,13 +95,122 @@ const isRepairRow = (row: PostImportRow): boolean =>
 
 
 const buildSession = (rows: PostImportRow[]): PostImportSession => ({
-    version: 2,
-    savedAt: new Date ().toISOString (),
+    version: 3,
+    expiresAt: '',
     source: rows.map (row => row.url).join ('\n'),
     rows,
     repairMode: resultRepairMode (rows) })
 
 
+const buildDryRunFormData = (row: PostImportRow): FormData => {
+  const formData = new FormData ()
+  formData.append ('url', row.url)
+  formData.append ('title', String (row.attributes.title ?? ''))
+  formData.append ('thumbnail_base', String (row.attributes.thumbnailBase ?? ''))
+  formData.append ('tags', String (row.attributes.tags ?? ''))
+  formData.append ('parent_post_ids', String (row.attributes.parentPostIds ?? ''))
+  formData.append (
+      'original_created_from',
+      String (row.attributes.originalCreatedFrom ?? ''))
+  formData.append (
+      'original_created_before',
+      String (row.attributes.originalCreatedBefore ?? ''))
+  formData.append ('video_ms', String (row.attributes.videoMs ?? ''))
+  formData.append ('duration', String (row.attributes.duration ?? ''))
+  return formData
+}
+
+
+const mergeDryRunRow = (
+    currentRow: PostImportRow,
+    result:     PreviewResponse,
+): PostImportRow =>
+    initialisePreviewRows ([{
+        ...currentRow,
+        url: result.url,
+        attributes: {
+            ...currentRow.attributes,
+            title: result.title ?? '',
+            thumbnailBase: result.thumbnailBase ?? '',
+            originalCreatedFrom: result.originalCreatedFrom ?? '',
+            originalCreatedBefore: result.originalCreatedBefore ?? '',
+            duration: result.duration ?? '',
+            videoMs: result.videoMs ?? '',
+            tags: result.tags ?? '',
+            parentPostIds: String (currentRow.attributes.parentPostIds ?? '') },
+        fieldWarnings: result.fieldWarnings ?? { },
+        baseWarnings: result.baseWarnings ?? [],
+        validationErrors: { },
+        importErrors: undefined,
+        status:
+            Object.keys (result.fieldWarnings ?? { }).length > 0
+            || (result.baseWarnings?.length ?? 0) > 0
+            ? 'warning'
+            : 'ready',
+        skipReason: result.existingPost?.id != null ? 'existing' : undefined,
+        existingPostId: result.existingPost?.id,
+        importStatus:
+            currentRow.importStatus === 'created'
+            ? 'created'
+            : 'pending',
+        recoverable: undefined }])[0]
+
+
+const indexedBulkResults = (
+    rows:     PostImportRow[],
+    results:  BulkApiRow[],
+): PostImportResultRow[] =>
+    rows.map ((row, index) => {
+      const result = results[index]
+      if (result?.status === 'created' && result.post != null)
+        {
+          return {
+              sourceRow: row.sourceRow,
+              status: 'created',
+              post: result.post,
+              fieldWarnings: result.fieldWarnings,
+              baseWarnings: result.baseWarnings,
+              errors: result.errors }
+        }
+      if (result?.status === 'skipped' && result.existingPost != null)
+        {
+          return {
+              sourceRow: row.sourceRow,
+              status: 'skipped',
+              existingPostId: result.existingPost.id,
+              fieldWarnings: result.fieldWarnings,
+              baseWarnings: result.baseWarnings,
+              errors: result.errors }
+        }
+      return {
+          sourceRow: row.sourceRow,
+          status: 'failed',
+          fieldWarnings: result?.fieldWarnings,
+          baseWarnings: result?.baseWarnings,
+          errors: result?.errors,
+          recoverable: result?.recoverable }
+    })
+
+
+const buildBulkFormData = (rows: PostImportRow[]): FormData => {
+  const formData = new FormData ()
+  formData.append (
+      'posts',
+      JSON.stringify (
+          rows.map (row => ({
+	      url: row.url,
+	      title: row.attributes.title ?? '',
+	      thumbnail_base: row.attributes.thumbnailBase ?? '',
+	      tags: row.attributes.tags ?? '',
+	      parent_post_ids: row.attributes.parentPostIds ?? '',
+	      original_created_from: row.attributes.originalCreatedFrom ?? '',
+	      original_created_before: row.attributes.originalCreatedBefore ?? '',
+	      video_ms: row.attributes.videoMs ?? '',
+	      duration: row.attributes.duration ?? '' }))))
+  return formData
+}
+
+
 const ExistingSkippedRows: FC<ExistingSkippedRowsProps> = ({ open, rows }) => {
   const existingPostIds = useMemo (
       () =>
@@ -157,12 +291,16 @@ const PostImportReviewPage: FC<Props> = ({ user }) => {
   const [editingRow, setEditingRow] = useState<PostImportRow | null> (null)
   const [showExistingRows, setShowExistingRows] = useState (false)
   const sessionRef = useRef<PostImportSession | null> (null)
+  const sessionIdRef = useRef<string | null> (null)
   const persistedSearchRef = useRef<string | null> (null)
   const persistSequenceRef = useRef (0)
 
   const persistSession = async (
       nextSession: PostImportSession,
   ): Promise<PostImportSession | null> => {
+    const sessionId =
+	sessionIdRef.current ?? generatePostImportSessionId ()
+    sessionIdRef.current = sessionId
     const sequence = ++persistSequenceRef.current
     const serialised = await serialisePostNewState (nextSession.rows)
     if (serialised == null)
@@ -170,16 +308,25 @@ const PostImportReviewPage: FC<Props> = ({ user }) => {
     if (persistSequenceRef.current !== sequence)
       return sessionRef.current
 
-    const persistedSession = buildSession (serialised.rows)
-    persistedSearchRef.current =
-	(new URL (serialised.path, window.location.origin)).search
+    savePostImportSession (sessionId, nextSession)
+    const loadedSession = loadPostImportSession (sessionId)
+    if (!(serialised.complete)
+        && loadedSession?.rows.length !== nextSession.rows.length)
+      return null
+
+    const persistedSession = buildSession (nextSession.rows)
+    const path = appendPostNewSessionId (serialised.path, sessionId)
+    persistedSearchRef.current = (new URL (path, window.location.origin)).search
     sessionRef.current = persistedSession
     setSession (persistedSession)
-    navigate (serialised.path, { replace: true })
+    navigate (path, { replace: true })
     return persistedSession
   }
 
   const finishImport = () => {
+    const sessionId = sessionIdRef.current
+    if (sessionId != null)
+      clearPostImportSession (sessionId)
     clearPostImportSourceDraft (message =>
 	toast ({ title: '入力内容を削除できませんでした', description: message }))
     navigate ('/posts')
@@ -202,7 +349,10 @@ const PostImportReviewPage: FC<Props> = ({ user }) => {
 	  return
 	}
 
-      const loaded = buildSession (parsed.rows)
+      const parsedSessionId = parsePostNewSessionId (location.search)
+      const sessionId = parsedSessionId ?? generatePostImportSessionId ()
+      sessionIdRef.current = sessionId
+      const loaded = loadPostImportSession (sessionId) ?? buildSession (parsed.rows)
       persistedSearchRef.current = location.search
       sessionRef.current = loaded
       setSession (loaded)
@@ -211,11 +361,71 @@ const PostImportReviewPage: FC<Props> = ({ user }) => {
 	{
 	  try
 	  {
-	    const preview = await apiPost<{ rows: PostImportRow[] }> ('/posts/import/preview', {
-		source: parsed.source })
+	    const preview = await apiGet<PreviewResponse> ('/posts/preview', {
+		params: { url: parsed.source } })
 	    if (!(active))
 	      return
-	    const rows = initialisePreviewRows (preview.rows)
+	    const rows = initialisePreviewRows ([{
+		sourceRow: 1,
+		url: preview.url,
+		attributes: {
+		    title: preview.title ?? '',
+		    thumbnailBase: preview.thumbnailBase ?? '',
+		    originalCreatedFrom: preview.originalCreatedFrom ?? '',
+		    originalCreatedBefore: preview.originalCreatedBefore ?? '',
+		    duration: preview.duration ?? '',
+		    videoMs: preview.videoMs ?? '',
+		    tags: preview.tags ?? '',
+		    parentPostIds: '' },
+		fieldWarnings: preview.fieldWarnings ?? { },
+		baseWarnings: preview.baseWarnings ?? [],
+		validationErrors: { },
+		provenance: {
+		    url: 'manual',
+		    title: 'automatic',
+		    thumbnailBase: 'automatic',
+		    originalCreatedFrom: 'automatic',
+		    originalCreatedBefore: 'automatic',
+		    duration: 'automatic',
+		    videoMs: 'automatic',
+		    tags: 'automatic',
+		    parentPostIds: 'automatic' },
+		tagSources: {
+		    automatic: preview.tags ?? '',
+		    manual: '' },
+		status:
+		    Object.keys (preview.fieldWarnings ?? { }).length > 0
+		    || (preview.baseWarnings?.length ?? 0) > 0
+		    ? 'warning'
+		    : 'ready',
+		skipReason: preview.existingPost?.id != null ? 'existing' : undefined,
+		existingPostId: preview.existingPost?.id,
+		resetSnapshot: {
+		    url: preview.url,
+		    attributes: {
+			title: preview.title ?? '',
+			thumbnailBase: preview.thumbnailBase ?? '',
+			originalCreatedFrom: preview.originalCreatedFrom ?? '',
+			originalCreatedBefore: preview.originalCreatedBefore ?? '',
+			duration: preview.duration ?? '',
+			videoMs: preview.videoMs ?? '',
+			tags: preview.tags ?? '',
+			parentPostIds: '' },
+		    provenance: {
+			url: 'manual',
+			title: 'automatic',
+			thumbnailBase: 'automatic',
+			originalCreatedFrom: 'automatic',
+			originalCreatedBefore: 'automatic',
+			duration: 'automatic',
+			videoMs: 'automatic',
+			tags: 'automatic',
+			parentPostIds: 'automatic' },
+		    tagSources: {
+			automatic: preview.tags ?? '',
+			manual: '' },
+		    fieldWarnings: preview.fieldWarnings ?? { },
+		    baseWarnings: preview.baseWarnings ?? [] } }])
 	    const persisted = await persistSession (buildSession (rows))
 	    if (persisted == null)
 	      return
@@ -228,37 +438,10 @@ const PostImportReviewPage: FC<Props> = ({ user }) => {
 	  return
 	}
 
-      const requestedRows = validatableImportRows (parsed.rows)
-      if (requestedRows.length === 0)
-	return
-
-      try
-      {
-	const validated = await apiPost<{ rows: PostImportRow[] }> ('/posts/import/validate', {
-	    rows: requestedRows.map (row => ({
-		    sourceRow: row.sourceRow,
-		    url: row.url,
-		    attributes: row.attributes,
-		    provenance: row.provenance,
-		    tagSources: row.tagSources,
-		    metadataUrl: row.metadataUrl })),
-	    changed_row: 'all' })
-	if (!(active))
-	  return
-
-	const validatedRows = initialisePreviewRows (validated.rows)
-	if (!(hasExactSourceRows (requestedRows.map (row => row.sourceRow), validatedRows)))
-	  return
-
-	const latest = sessionRef.current ?? loaded
-	const rows = mergeValidatedImportRows (latest.rows, validatedRows)
-	const persisted = await persistSession (buildSession (rows))
-	if (persisted == null)
-	  return
-      }
-      catch
-      {
-      }
+      if (parsedSessionId == null)
+	{
+	  await persistSession (loaded)
+	}
     }
 
     void hydrate ()
@@ -354,51 +537,46 @@ const PostImportReviewPage: FC<Props> = ({ user }) => {
 	: row
     const urlChanged = draft.url !== baseRow.url
     const nextRow = buildNextEditedRow (baseRow, draft, urlChanged)
-    const nextRows = currentSession.rows.map (currentRow =>
-		currentRow.sourceRow === baseRow.sourceRow
-		? nextRow
-		: currentRow)
     try
     {
-      const validated = await apiPost<{ rows: PostImportRow[] }> ('/posts/import/validate', {
-	  rows:
-	      validatableImportRows (nextRows)
-	      .map (currentRow => ({
-		      sourceRow: currentRow.sourceRow,
-		      url: currentRow.url,
-		      attributes: currentRow.attributes,
-		      provenance: currentRow.provenance,
-		      tagSources: currentRow.tagSources,
-		      metadataUrl: currentRow.metadataUrl })),
-	  changed_row: urlChanged ? baseRow.sourceRow : -1 })
-      const validatedRows = initialisePreviewRows (validated.rows)
-      const target = validatedRows.find (
-	  validatedRow => validatedRow.sourceRow === baseRow.sourceRow)
+      const dryRun = await apiPost<PreviewResponse> (
+	  '/posts?dry=1',
+	  buildDryRunFormData (nextRow))
       const latestSession = sessionRef.current
       if (latestSession == null)
 	return { saved: false, row: null }
-      if (target == null)
-	{
-	  const restoredRows = replaceImportRow (latestSession.rows, row)
-	  await persistSession (buildSession (restoredRows))
-	  toast ({ title: '行の再検証結果が不完全でした' })
-	  return { saved: false, row: null }
-	}
 
-      const editedRows = replaceImportRow (latestSession.rows, nextRow)
-      const mergedRows = mergeValidatedImportRow (editedRows, target)
+      const mergedRow = mergeDryRunRow (nextRow, dryRun)
+      const mergedRows = replaceImportRow (latestSession.rows, mergedRow)
       const nextSession = await persistSession (buildSession (mergedRows))
       if (nextSession == null)
 	return { saved: false, row: null }
-      const mergedTarget =
-	  nextSession.rows.find (mergedRow => mergedRow.sourceRow === baseRow.sourceRow)
-	  ?? target
+      const mergedTarget = nextSession.rows.find (
+	  currentRow => currentRow.sourceRow === baseRow.sourceRow)
+      if (mergedTarget == null)
+	return { saved: false, row: null }
       if (Object.keys (mergedTarget.validationErrors).length > 0)
 	return { saved: false, row: mergedTarget }
       return { saved: true, row: null }
     }
-    catch
+    catch (requestError)
     {
+      if (isApiError<{
+	      errors?:      Record<string, string[]>
+	      baseErrors?:  string[]
+	  }> (requestError)
+	  && requestError.response?.status === 422)
+	{
+	  const errorRow = {
+	      ...nextRow,
+	      validationErrors: requestError.response.data.errors ?? { },
+	      baseWarnings: [],
+	      fieldWarnings: { },
+	      status: 'error' as const }
+	  setMessageRow (errorRow)
+	  return { saved: false, row: errorRow }
+	}
+
       toast ({ title: '行の再検証に失敗しました' })
       return { saved: false, row: null }
     }
@@ -461,81 +639,26 @@ const PostImportReviewPage: FC<Props> = ({ user }) => {
       if (pendingSession == null)
 	return
 
-      const requestedRows = validatableImportRows (pendingSession.rows)
-      const validated = await apiPost<{ rows: PostImportRow[] }> ('/posts/import/validate', {
-	  rows: requestedRows.map (row => ({
-		  sourceRow: row.sourceRow,
-		  url: row.url,
-		  attributes: row.attributes,
-		  provenance: row.provenance,
-		  tagSources: row.tagSources,
-		  metadataUrl: row.metadataUrl })),
-	  changed_row: -1 })
-      const validatedRows = initialisePreviewRows (validated.rows)
-      if (!(hasExactSourceRows (requestedRows.map (row => row.sourceRow), validatedRows)))
-	{
-	  const latest = sessionRef.current ?? pendingSession
-	  const restoredRows = replaceImportRow (latest.rows, originalRow)
-	  await persistSession (buildSession (restoredRows))
-	  toast ({ title: '再検証結果が不完全でした' })
-	  return
-	}
-
-      const validatedTarget = validatedRows.find (row => row.sourceRow === sourceRow)
-      if (validatedTarget == null)
-	{
-	  const latest = sessionRef.current ?? pendingSession
-	  const restoredRows = replaceImportRow (latest.rows, originalRow)
-	  await persistSession (buildSession (restoredRows))
-	  toast ({ title: '再検証結果が不完全でした' })
-	  return
-	}
-
-      const latestAfterValidate = sessionRef.current ?? pendingSession
-      const mergedValidatedRows = mergeValidatedImportRow (
-	  latestAfterValidate.rows,
-	  validatedTarget)
-      const nextSession = await persistSession (buildSession (mergedValidatedRows))
-      if (nextSession == null)
-	return
-      const target = nextSession.rows.find (row => row.sourceRow === sourceRow)
+      const target = pendingSession.rows.find (row => row.sourceRow === sourceRow)
       if (target == null)
-	{
-	  const restoredRows = replaceImportRow (latestAfterValidate.rows, originalRow)
-	  await persistSession (buildSession (restoredRows))
-	  toast ({ title: '再検証結果が不完全でした' })
-	  return
-	}
-      if (Object.keys (target.validationErrors ?? { }).length > 0)
-	{
-	  editRow (target)
-	  return
-	}
+	return
 
-      const result = await apiPost<{
-	  created: number
-	  skipped: number
-	  failed:  number
-	  rows:    PostImportResultRow[] }> ('/posts/import', {
-	      rows: [{
-		  sourceRow: target.sourceRow,
-		  url: target.url,
-		  attributes: target.attributes,
-		  provenance: target.provenance,
-		  tagSources: target.tagSources,
-		  metadataUrl: target.metadataUrl }] })
-      if (!(hasExactSourceRows ([sourceRow], result.rows)))
+      const result = await apiPost<{ results: BulkApiRow[] }>(
+	  '/posts/bulk',
+	  buildBulkFormData ([target]))
+      if (result.results.length !== 1)
 	{
-	  const latest = sessionRef.current ?? nextSession
+	  const latest = sessionRef.current ?? pendingSession
 	  const restoredRows = replaceImportRow (latest.rows, originalRow)
 	  await persistSession (buildSession (restoredRows))
 	  toast ({ title: '登録結果が不完全でした' })
 	  return
 	}
 
-      const latestAfterImport = sessionRef.current ?? nextSession
-      const mergedRows = mergeImportResults (latestAfterImport.rows, result.rows)
-      const recoverableRows = result.rows.filter (row =>
+      const indexedResults = indexedBulkResults ([target], result.results)
+      const latestAfterImport = sessionRef.current ?? pendingSession
+      const mergedRows = mergeImportResults (latestAfterImport.rows, indexedResults)
+      const recoverableRows = indexedResults.filter (row =>
 	  row.status === 'failed'
 	  && row.recoverable
 	  && Object.keys (row.errors ?? { }).length > 0)
@@ -579,66 +702,26 @@ const PostImportReviewPage: FC<Props> = ({ user }) => {
     setLoading (true)
     try
     {
-      const validatableRows = validatableImportRows (currentSession.rows)
-      if (validatableRows.length === 0)
+      const processingRows = processableImportRows (currentSession.rows)
+      if (processingRows.length === 0)
 	{
 	  finishImport ()
 	  return
 	}
-      const validated = await apiPost<{ rows: PostImportRow[] }> ('/posts/import/validate', {
-	  rows:
-	      validatableRows.map (row => ({
-		      sourceRow: row.sourceRow,
-		      url: row.url,
-		      attributes: row.attributes,
-		      provenance: row.provenance,
-		      tagSources: row.tagSources,
-		      metadataUrl: row.metadataUrl })),
-	  changed_row: -1 })
-      const validatedRows = initialisePreviewRows (validated.rows)
-      const expectedSourceRows = validatableRows.map (row => row.sourceRow)
-      if (!(hasExactSourceRows (expectedSourceRows, validatedRows)))
-	{
-	  toast ({ title: '再検証結果が不完全でした' })
-	  return
-	}
 
-      const latestAfterValidate = sessionRef.current ?? currentSession
-      const mergedRows = mergeValidatedImportRows (latestAfterValidate.rows, validatedRows)
-      const persistedValidated = await persistSession (buildSession (mergedRows))
-      if (persistedValidated == null)
-	return
-      const currentRows = persistedValidated.rows
-      const firstInvalid = currentRows.find (
-	  row => Object.keys (row.validationErrors).length > 0)
-      if (firstInvalid != null)
-	{
-	  editRow (firstInvalid)
-	  return
-	}
-
-      const result = await apiPost<{
-	  created: number
-	  skipped: number
-	  failed:  number
-	  rows:    PostImportResultRow[] }> ('/posts/import', {
-	      rows: processableImportRows (currentRows).map (row => ({
-		  sourceRow: row.sourceRow,
-		  url: row.url,
-		  attributes: row.attributes,
-		  provenance: row.provenance,
-		  tagSources: row.tagSources,
-		  metadataUrl: row.metadataUrl })) })
-      const expectedImportRows = processableImportRows (currentRows).map (row => row.sourceRow)
-      if (!(hasExactSourceRows (expectedImportRows, result.rows)))
+      const result = await apiPost<{ results: BulkApiRow[] }>(
+	  '/posts/bulk',
+	  buildBulkFormData (processingRows))
+      if (result.results.length !== processingRows.length)
 	{
 	  toast ({ title: '登録結果が不完全でした' })
 	  return
 	}
 
-      const latestAfterImport = sessionRef.current ?? buildSession (currentRows)
-      const mergedResults = mergeImportResults (latestAfterImport.rows, result.rows)
-      const recoverableRows = result.rows.filter (row =>
+      const indexedResults = indexedBulkResults (processingRows, result.results)
+      const latestAfterImport = sessionRef.current ?? buildSession (currentSession.rows)
+      const mergedResults = mergeImportResults (latestAfterImport.rows, indexedResults)
+      const recoverableRows = indexedResults.filter (row =>
 	  row.status === 'failed'
 	  && row.recoverable
 	  && Object.keys (row.errors ?? { }).length > 0)
diff --git a/frontend/src/pages/posts/PostImportSourcePage.tsx b/frontend/src/pages/posts/PostImportSourcePage.tsx
index 45afab1..eb0a72d 100644
--- a/frontend/src/pages/posts/PostImportSourcePage.tsx
+++ b/frontend/src/pages/posts/PostImportSourcePage.tsx
@@ -11,13 +11,20 @@ import MainArea from '@/components/layout/MainArea'
 import { Button } from '@/components/ui/button'
 import { toast } from '@/components/ui/use-toast'
 import { SITE_TITLE } from '@/config'
-import { apiPost, isApiError } from '@/lib/api'
-import { serialisePostNewState } from '@/lib/postNewQueryState'
+import { apiGet, isApiError } from '@/lib/api'
+import {
+    appendPostNewSessionId,
+    serialisePostNewState,
+} from '@/lib/postNewQueryState'
 import { canEditContent } from '@/lib/users'
 import { countImportSourceLines,
+	 generatePostImportSessionId,
 	 cleanupExpiredPostImportSessions,
 	 initialisePreviewRows,
+	 loadPostImportSession,
 	 loadPostImportSourceDraft,
+	 resultRepairMode,
+	 savePostImportSession,
 	 savePostImportSourceDraft,
 	 validateImportSource } from '@/lib/postImportSession'
 import Forbidden from '@/pages/Forbidden'
@@ -29,6 +36,19 @@ import type { User } from '@/types'
 
 type Props = { user: User | null }
 
+type PreviewResponse = {
+  url:                   string
+  title?:                string
+  thumbnailBase?:        string
+  originalCreatedFrom?:  string
+  originalCreatedBefore?: string
+  duration?:             string
+  videoMs?:              number
+  tags?:                 string
+  fieldWarnings?:        Record<string, string[]>
+  baseWarnings?:         string[]
+  existingPost?:         { id: number } | null }
+
 const MAX_ROWS = 100
 const SOURCE_ERROR_ID = 'post-import-source-error'
 const SOURCE_ISSUES_ID = 'post-import-source-issues'
@@ -44,6 +64,96 @@ const urlIssuesFromRows = (rows: PostImportRow[], source: string) => {
 }
 
 
+const previewRowFromResult = (
+    sourceRow: number,
+    result:    PreviewResponse,
+): PostImportRow => {
+  const fieldWarnings = result.fieldWarnings ?? { }
+  const baseWarnings = result.baseWarnings ?? []
+  const row: PostImportRow = {
+      sourceRow,
+      url: result.url,
+      attributes: {
+	  title: result.title ?? '',
+	  thumbnailBase: result.thumbnailBase ?? '',
+	  originalCreatedFrom: result.originalCreatedFrom ?? '',
+	  originalCreatedBefore: result.originalCreatedBefore ?? '',
+	  duration: result.duration ?? '',
+	  videoMs: result.videoMs ?? '',
+	  tags: result.tags ?? '',
+	  parentPostIds: '' },
+      fieldWarnings,
+      baseWarnings,
+      validationErrors: { },
+      provenance: {
+	  url: 'manual',
+	  title: 'automatic',
+	  thumbnailBase: 'automatic',
+	  originalCreatedFrom: 'automatic',
+	  originalCreatedBefore: 'automatic',
+	  duration: 'automatic',
+	  videoMs: 'automatic',
+	  tags: 'automatic',
+	  parentPostIds: 'automatic' },
+      tagSources: {
+	  automatic: result.tags ?? '',
+	  manual: '' },
+      status:
+	  Object.keys (fieldWarnings).length > 0 || baseWarnings.length > 0
+	  ? 'warning'
+	  : 'ready',
+      skipReason: result.existingPost?.id != null ? 'existing' : undefined,
+      existingPostId: result.existingPost?.id,
+      resetSnapshot: {
+	  url: result.url,
+	  attributes: {
+	      title: result.title ?? '',
+	      thumbnailBase: result.thumbnailBase ?? '',
+	      originalCreatedFrom: result.originalCreatedFrom ?? '',
+	      originalCreatedBefore: result.originalCreatedBefore ?? '',
+	      duration: result.duration ?? '',
+	      videoMs: result.videoMs ?? '',
+	      tags: result.tags ?? '',
+	      parentPostIds: '' },
+	  provenance: {
+	      url: 'manual',
+	      title: 'automatic',
+	      thumbnailBase: 'automatic',
+	      originalCreatedFrom: 'automatic',
+	      originalCreatedBefore: 'automatic',
+	      duration: 'automatic',
+	      videoMs: 'automatic',
+	      tags: 'automatic',
+	      parentPostIds: 'automatic' },
+	  tagSources: {
+	      automatic: result.tags ?? '',
+	      manual: '' },
+	  fieldWarnings,
+	  baseWarnings } }
+  return row
+}
+
+
+const fetchPreviewRows = async (urls: string[]): Promise<PostImportRow[]> => {
+  const results: PostImportRow[] = new Array (urls.length)
+  let nextIndex = 0
+  const worker = async () => {
+    while (nextIndex < urls.length)
+    {
+      const index = nextIndex
+      ++nextIndex
+      const result = await apiGet<PreviewResponse> ('/posts/preview', {
+	  params: { url: urls[index] } })
+      results[index] = previewRowFromResult (index + 1, result)
+    }
+  }
+
+  await Promise.all (
+      Array.from ({ length: Math.min (4, urls.length) }, () => worker ()))
+  return results
+}
+
+
 const PostImportSourcePage: FC<Props> = ({ user }) => {
   const editable = canEditContent (user)
   const navigate = useNavigate ()
@@ -114,17 +224,30 @@ const PostImportSourcePage: FC<Props> = ({ user }) => {
     setSourceError (null)
     try
     {
-      const data = await apiPost<{ rows: PostImportRow[] }> ('/posts/import/preview', { source })
-      const urlIssues = urlIssuesFromRows (data.rows, source)
+      const urls = source.split (/\r\n|\n|\r/).map (line => line.trim ()).filter (line => line !== '')
+      const rows = await fetchPreviewRows (urls)
+      const urlIssues = urlIssuesFromRows (rows, source)
       if (urlIssues.length > 0)
 	{
 	  setSourceIssues (urlIssues)
 	  return
 	}
-      const nextRows = initialisePreviewRows (data.rows)
+      const nextRows = initialisePreviewRows (rows)
       const serialised = await serialisePostNewState (nextRows)
-      if (serialised != null)
-	navigate (serialised.path)
+      if (serialised == null)
+	return
+
+      const sessionId = generatePostImportSessionId ()
+      const session = {
+	  source,
+	  rows: nextRows,
+	  repairMode: resultRepairMode (nextRows) }
+      savePostImportSession (sessionId, session)
+      const sessionLoaded = loadPostImportSession (sessionId)
+      if (!(serialised.complete) && sessionLoaded?.rows.length !== nextRows.length)
+	return
+
+      navigate (appendPostNewSessionId (serialised.path, sessionId))
     }
     catch (requestError)
     {