diff --git a/be/apps/core/src/modules/photo/photo.service.ts b/be/apps/core/src/modules/photo/photo.service.ts
index 95f64ca3..6810cf44 100644
--- a/be/apps/core/src/modules/photo/photo.service.ts
+++ b/be/apps/core/src/modules/photo/photo.service.ts
@@ -7,7 +7,12 @@ import type {
   StorageConfig,
   StorageObject,
 } from '@afilmory/builder'
-import { AfilmoryBuilder, processPhotoWithPipeline, thumbnailStoragePlugin } from '@afilmory/builder'
+import {
+  AfilmoryBuilder,
+  processPhotoWithPipeline,
+  THUMBNAIL_PLUGIN_SYMBOL,
+  thumbnailStoragePlugin,
+} from '@afilmory/builder'
 import type { Logger as BuilderLogger } from '@afilmory/builder/logger/index.js'
 import type { PhotoProcessingLoggers } from '@afilmory/builder/photo/index.js'
 import { createPhotoProcessingLoggers, setGlobalLoggers } from '@afilmory/builder/photo/index.js'
@@ -144,13 +149,11 @@ export class PhotoBuilderService {
   private ensureThumbnailPlugin(config: BuilderConfig): BuilderConfig {
     const existingPlugins = config.plugins ?? []
     const hasPlugin = existingPlugins.some((entry) => {
-      if (typeof entry === 'string') {
-        return entry.includes('thumbnail-storage')
-      }
-      if (typeof entry === 'function') {
-        const fnName = entry.name ?? ''
-        return fnName.includes('thumbnailStorage') || entry.toString().includes('thumbnail-storage')
+      // Check for the unique Symbol identifier for reliable detection
+      if (typeof entry === 'object' && entry !== null && THUMBNAIL_PLUGIN_SYMBOL in entry) {
+        return true
       }
+      // Fallback: check by name property for backward compatibility
       return entry?.name === 'afilmory:thumbnail-storage'
     })
 
diff --git a/packages/builder/src/index.ts b/packages/builder/src/index.ts
index 5bc5a854..6811bf01 100644
--- a/packages/builder/src/index.ts
+++ b/packages/builder/src/index.ts
@@ -23,7 +23,7 @@ export { default as localStoragePlugin } from './plugins/storage/local.js'
 export type { S3StoragePluginOptions } from './plugins/storage/s3.js'
 export { default as s3StoragePlugin } from './plugins/storage/s3.js'
 export type { ThumbnailStoragePluginOptions } from './plugins/thumbnail-storage/index.js'
-export { default as thumbnailStoragePlugin } from './plugins/thumbnail-storage/index.js'
+export { THUMBNAIL_PLUGIN_SYMBOL, default as thumbnailStoragePlugin } from './plugins/thumbnail-storage/index.js'
 export type {
   BuilderPlugin,
   BuilderPluginConfigEntry,
diff --git a/packages/builder/src/plugins/thumbnail-storage/index.ts b/packages/builder/src/plugins/thumbnail-storage/index.ts
index fd782326..2f001bc4 100644
--- a/packages/builder/src/plugins/thumbnail-storage/index.ts
+++ b/packages/builder/src/plugins/thumbnail-storage/index.ts
@@ -2,7 +2,12 @@ import { StorageManager } from '../../storage/index.js'
 import type { StorageConfig } from '../../storage/interfaces.js'
 import type { BuilderPlugin } from '../types.js'
 import type { ThumbnailPluginData } from './shared.js'
-import { DEFAULT_CONTENT_TYPE, DEFAULT_DIRECTORY, THUMBNAIL_PLUGIN_DATA_KEY } from './shared.js'
+import {
+  DEFAULT_CONTENT_TYPE,
+  DEFAULT_DIRECTORY,
+  THUMBNAIL_PLUGIN_DATA_KEY,
+  THUMBNAIL_PLUGIN_SYMBOL,
+} from './shared.js'
 
 const PLUGIN_NAME = 'afilmory:thumbnail-storage'
 const RUN_STATE_KEY = 'state'
@@ -82,8 +87,9 @@ export default function thumbnailStoragePlugin(options: ThumbnailStoragePluginOp
   let resolved: ResolvedPluginConfig | null = null
   let externalStorageManager: StorageManager | null = null
 
-  return {
+  const plugin: BuilderPlugin & { [THUMBNAIL_PLUGIN_SYMBOL]: true } = {
     name: PLUGIN_NAME,
+    [THUMBNAIL_PLUGIN_SYMBOL]: true,
     hooks: {
       onInit: ({ builder, config, logger }) => {
         const storageConfig = (options.storageConfig ?? config.storage) as StorageConfig
@@ -175,6 +181,10 @@ export default function thumbnailStoragePlugin(options: ThumbnailStoragePluginOp
       },
     },
   }
+
+  return plugin
 }
 
 export type { ThumbnailStoragePluginOptions }
+
+export { THUMBNAIL_PLUGIN_SYMBOL } from './shared.js'
diff --git a/packages/builder/src/plugins/thumbnail-storage/shared.ts b/packages/builder/src/plugins/thumbnail-storage/shared.ts
index 9b4100ba..77fc0600 100644
--- a/packages/builder/src/plugins/thumbnail-storage/shared.ts
+++ b/packages/builder/src/plugins/thumbnail-storage/shared.ts
@@ -2,6 +2,12 @@ import type { Buffer } from 'node:buffer'
 
 export const THUMBNAIL_PLUGIN_DATA_KEY = 'afilmory:thumbnail-storage:data'
 
+/**
+ * Unique symbol identifier for the thumbnail storage plugin.
+ * Used for reliable plugin detection without fragile string matching.
+ */
+export const THUMBNAIL_PLUGIN_SYMBOL = Symbol.for('afilmory:thumbnail-storage')
+
 export interface ThumbnailPluginData {
   photoId: string
   fileName: string