diff --git a/py/api.py b/py/api.py
index fe293e8..38b077a 100644
--- a/py/api.py
+++ b/py/api.py
@@ -1067,7 +1067,8 @@ class PromptManagerAPI:
                         thumbnail_abs_path = output_path / thumbnail_rel_path
 
                         if thumbnail_abs_path.exists():
-                            thumbnail_url = f'/prompt_manager/images/serve/{Path(thumbnail_rel_path).as_posix()}'
+                            from urllib.parse import quote
+                            thumbnail_url = f'/prompt_manager/images/serve/{quote(thumbnail_rel_path.as_posix(), safe="/")}'
                     
                     image_info = {
                         'id': str(hash(str(media_path))),
@@ -1950,6 +1951,7 @@ class PromptManagerAPI:
                     thumbnail_url = None
                     if thumbnails_dir.exists():
                         # For videos, look for thumbnail with .jpg extension
+                        # Use full relative path to support subdirectories
                         thumbnail_ext = '.jpg' if is_video else extension
                         # Preserve subdirectory structure in thumbnail path
                         rel_path_no_ext = rel_path.with_suffix('')
@@ -1957,7 +1959,8 @@ class PromptManagerAPI:
                         thumbnail_abs_path = output_path / thumbnail_rel_path
 
                         if thumbnail_abs_path.exists():
-                            thumbnail_url = f'/prompt_manager/images/serve/{Path(thumbnail_rel_path).as_posix()}'
+                            from urllib.parse import quote
+                            thumbnail_url = f'/prompt_manager/images/serve/{quote(thumbnail_rel_path.as_posix(), safe="/")}'
                     
                     images.append({
                         'id': str(hash(str(media_path))),  # Simple hash for ID
diff --git a/web/admin.html b/web/admin.html
index 771ac91..8e1f347 100644
--- a/web/admin.html
+++ b/web/admin.html
@@ -4713,14 +4713,28 @@ Seed: ${this.currentMetadata.seed || 'Unknown'}`;
                 // If thumbnail_url already exists, use it
                 if (image.thumbnail_url) return image.thumbnail_url;
 
-                // Try to construct thumbnail URL from filename
-                // Thumbnails are stored as: thumbnails/{stem}_thumb{ext}
+                // Try to construct thumbnail URL from filename and relative_path
+                // Thumbnails are stored as: thumbnails/{parent_dir}/{stem}_thumb{ext}
+                // to avoid collisions with same-named files in different directories
                 if (image.filename) {
                     const lastDot = image.filename.lastIndexOf('.');
                     if (lastDot > 0) {
                         const stem = image.filename.substring(0, lastDot);
                         const ext = image.filename.substring(lastDot);
-                        return `/prompt_manager/images/serve/thumbnails/${stem}_thumb${ext}`;
+                        
+                        // Get parent directory from relative_path if available
+                        let parentDir = '';
+                        if (image.relative_path) {
+                            const relPath = image.relative_path.replace(/\\/g, '/');
+                            const lastSlash = relPath.lastIndexOf('/');
+                            if (lastSlash > 0) {
+                                parentDir = relPath.substring(0, lastSlash) + '/';
+                            }
+                        }
+                        
+                        // URL encode the path components (but preserve slashes)
+                        const encodedParentDir = parentDir.split('/').map(p => encodeURIComponent(p)).join('/');
+                        return `/prompt_manager/images/serve/thumbnails/${encodedParentDir}${encodeURIComponent(stem)}_thumb${ext}`;
                     }
                 }