diff --git a/backend/spec/requests/posts_spec.rb b/backend/spec/requests/posts_spec.rb
index 8f51753..752ac6a 100644
--- a/backend/spec/requests/posts_spec.rb
+++ b/backend/spec/requests/posts_spec.rb
@@ -898,6 +898,22 @@ RSpec.describe 'Posts API', type: :request do
       expect(json.fetch('video_ms')).to eq(180_500)
     end
 
+    it 'creates a video post with number input duration seconds' do
+      sign_in_as(member)
+
+      post '/posts', params: post_write_params(
+        title: 'video post seconds',
+        url: 'https://example.com/video-post-seconds',
+        tags: '動画 spec_tag',
+        duration: '180.5',
+        thumbnail: dummy_upload
+      )
+
+      expect(response).to have_http_status(:created)
+      expect(Post.find(json.fetch('id')).video_ms).to eq(180_500)
+      expect(json.fetch('video_ms')).to eq(180_500)
+    end
+
     it 'clears video_ms when the saved tags do not include 動画' do
       sign_in_as(member)
 
diff --git a/frontend/src/lib/posts.test.ts b/frontend/src/lib/posts.test.ts
index 724afe4..600df31 100644
--- a/frontend/src/lib/posts.test.ts
+++ b/frontend/src/lib/posts.test.ts
@@ -70,6 +70,7 @@ describe ('posts API functions', () => {
           id:                    5,
           title:                 'new title',
           tags:                  'tag',
+          duration:              null,
           parentPostIds:         '1 2',
           originalCreatedFrom:   null,
           originalCreatedBefore: '2026-01-02T00:00:00Z',
@@ -82,6 +83,7 @@ describe ('posts API functions', () => {
         {
           title:                   'new title',
           tags:                    'tag',
+          duration:                null,
           parent_post_ids:         '1 2',
           original_created_from:   null,
           original_created_before: '2026-01-02T00:00:00Z',
diff --git a/frontend/src/pages/theatres/TheatreDetailPage.test.tsx b/frontend/src/pages/theatres/TheatreDetailPage.test.tsx
index ccb5407..2c87aba 100644
--- a/frontend/src/pages/theatres/TheatreDetailPage.test.tsx
+++ b/frontend/src/pages/theatres/TheatreDetailPage.test.tsx
@@ -88,6 +88,10 @@ const weights = buildTheatrePostSelectionWeights ({
     tags:    [],
   }],
 })
+const watchingUsers = [
+  { id: 1, name: 'tester' },
+  { id: 2, name: 'another' },
+]
 
 const renderPage = (user = buildUser ({ id: 1, role: 'member' })) =>
   renderWithProviders (
@@ -136,11 +140,11 @@ const mockDefaultApi = () => {
         postId:        currentPost.id,
         postStartedAt: '2026-01-02T03:04:05.000Z',
         postElapsedMs: 1_000,
-        watchingUsers: [{ id: 1, name: 'tester' }],
+        watchingUsers,
         skipVote:      {
           votesCount:         0,
           requiredCount:      2,
-          watchingUsersCount: 1,
+          watchingUsersCount: watchingUsers.length,
           voted:              false,
         },
       }))
@@ -150,11 +154,11 @@ const mockDefaultApi = () => {
         postId:        currentPost.id,
         postStartedAt: '2026-01-02T03:04:05.000Z',
         postElapsedMs: 2_000,
-        watchingUsers: [{ id: 1, name: 'tester' }],
+        watchingUsers,
         skipVote:      {
           votesCount:         1,
           requiredCount:      2,
-          watchingUsersCount: 1,
+          watchingUsersCount: watchingUsers.length,
           voted:              true,
         },
       }))
diff --git a/frontend/src/types.ts b/frontend/src/types.ts
index 434a579..2b9b718 100644
--- a/frontend/src/types.ts
+++ b/frontend/src/types.ts
@@ -356,6 +356,7 @@ export type Tag = {
     hasWiki:        boolean
     materialId:     number | null
     hasDeerjikists: boolean
+    children?:      Tag[]
     matchedAlias?:  string | null }
 
 export type TagVersion = {
@@ -370,9 +371,9 @@ export type TagVersion = {
     createdAt:              string
     createdByUser:          { id: number; name: string | null } | null }
 
-export type TagWithSections = Tag & { sections: { beginMs:  number
-						  endMs:    number | null }[]
-			              children: TagWithSections[] }
+export type TagWithSections = Omit<Tag, 'children'> & { sections: { beginMs:  number
+								    endMs:    number | null }[]
+					              children: TagWithSections[] }
 
 export type Theatre = {
     id:             number