diff --git a/backend/app/controllers/wiki_assets_controller.rb b/backend/app/controllers/wiki_assets_controller.rb
index eca800e..c3861c2 100644
--- a/backend/app/controllers/wiki_assets_controller.rb
+++ b/backend/app/controllers/wiki_assets_controller.rb
@@ -21,6 +21,7 @@ class WikiAssetsController < ApplicationController
     file = params[:file]
     return head :bad_request if file.blank?
 
+    asset = nil
     page.with_lock do
       no = page.next_asset_no
       alt_text = params[:alt_text].presence
@@ -33,6 +34,6 @@ class WikiAssetsController < ApplicationController
       page.update!(next_asset_no: no + 1)
     end
 
-    render json: asset.as_json(methods: [:url])
+    render json: asset.as_json(only: [:wiki_page_id, :no], methods: [:url])
   end
 end
diff --git a/backend/app/models/wiki_asset.rb b/backend/app/models/wiki_asset.rb
index 52321cf..c772679 100644
--- a/backend/app/models/wiki_asset.rb
+++ b/backend/app/models/wiki_asset.rb
@@ -1,6 +1,4 @@
 class WikiAsset < ApplicationRecord
-  self.primary_key = :wiki_page_id, :no
-
   belongs_to :wiki_page
   belongs_to :created_by_user, class_name: 'User'
 
diff --git a/backend/db/migrate/20260323192300_create_wiki_assets.rb b/backend/db/migrate/20260323192300_create_wiki_assets.rb
index 1a4e875..97e0c43 100644
--- a/backend/db/migrate/20260323192300_create_wiki_assets.rb
+++ b/backend/db/migrate/20260323192300_create_wiki_assets.rb
@@ -1,6 +1,6 @@
 class CreateWikiAssets < ActiveRecord::Migration[8.0]
   def change
-    create_table :wiki_assets, primary_key: [:wiki_page_id, :no] do |t|
+    create_table :wiki_assets do |t|
       t.references :wiki_page, null: false, foreign_key: true, index: false
       t.integer :no, null: false
       t.string :alt_text
@@ -10,6 +10,7 @@ class CreateWikiAssets < ActiveRecord::Migration[8.0]
     end
 
     add_index :wiki_assets, [:wiki_page_id, :sha256], unique: true
+    add_index :wiki_assets, [:wiki_page_id, :no], unique: true
 
     add_column :wiki_pages, :next_asset_no, :integer, null: false, default: 1
   end
diff --git a/backend/db/schema.rb b/backend/db/schema.rb
index 7dbc388..82e8fe2 100644
--- a/backend/db/schema.rb
+++ b/backend/db/schema.rb
@@ -239,7 +239,7 @@ ActiveRecord::Schema[8.0].define(version: 2026_03_23_192300) do
     t.datetime "updated_at", null: false
   end
 
-  create_table "wiki_assets", primary_key: ["wiki_page_id", "no"], charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
+  create_table "wiki_assets", charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
     t.bigint "wiki_page_id", null: false
     t.integer "no", null: false
     t.string "alt_text"
@@ -248,6 +248,7 @@ ActiveRecord::Schema[8.0].define(version: 2026_03_23_192300) do
     t.datetime "created_at", null: false
     t.datetime "updated_at", null: false
     t.index ["created_by_user_id"], name: "index_wiki_assets_on_created_by_user_id"
+    t.index ["wiki_page_id", "no"], name: "index_wiki_assets_on_wiki_page_id_and_no", unique: true
     t.index ["wiki_page_id", "sha256"], name: "index_wiki_assets_on_wiki_page_id_and_sha256", unique: true
   end
 
diff --git a/frontend/src/components/WikiEditForm.tsx b/frontend/src/components/WikiEditForm.tsx
index 41556ee..c989622 100644
--- a/frontend/src/components/WikiEditForm.tsx
+++ b/frontend/src/components/WikiEditForm.tsx
@@ -39,7 +39,7 @@ export default (({ title: initTitle, body: initBody, onSubmit, id }: Props) => {
 	formData,
 	{ headers: { 'Content-Type': 'multipart/form-data' } })
 
-    return `{{img:${ asset.no }}}`
+    return asset.url
   }
 
   return (
diff --git a/frontend/src/components/WikiMarkdown.tsx b/frontend/src/components/WikiMarkdown.tsx
index edb23e2..dc19c01 100644
--- a/frontend/src/components/WikiMarkdown.tsx
+++ b/frontend/src/components/WikiMarkdown.tsx
@@ -43,7 +43,7 @@ const makeComponents = (preview = false) => (
       img: (({ src, alt }) => (
 	  <img src={src ?? ''}
 	       alt={alt ?? ''}
-	       className="max-w-full h-auto rounded"/>)),
+	       className="max-w-[240px] max-h-[320px]"/>)),
     } as const satisfies Components)