diff --git a/src/App.jsx b/src/App.jsx
index fb11c5d..15da67c 100644
--- a/src/App.jsx
+++ b/src/App.jsx
@@ -226,39 +226,173 @@ function AssistantMessageContent({ content, streamOutput, sources }) {
   );
 }
 
-function ImageAttachmentStrip({ attachments, className = '', removable = false, onRemove }) {
+const CHAT_IMAGE_EXTENSION_LIST = ['.png', '.jpg', '.jpeg', '.gif', '.bmp', '.webp', '.tif', '.tiff', '.heic', '.avif']
+const CHAT_FILE_EXTENSION_LIST = [
+  '.pdf', '.html', '.htm', '.txt', '.md', '.rst', '.epub',
+  '.mp3', '.wav', '.m4a', '.flac', '.ogg', '.opus', '.aac',
+  '.mp4', '.mkv', '.mov', '.webm', '.avi', '.ts',
+]
+const CHAT_IMAGE_EXTENSION_SET = new Set(CHAT_IMAGE_EXTENSION_LIST)
+const CHAT_FILE_EXTENSION_SET = new Set(CHAT_FILE_EXTENSION_LIST)
+const CHAT_AUDIO_EXTENSION_SET = new Set(['.mp3', '.wav', '.m4a', '.flac', '.ogg', '.opus', '.aac'])
+const CHAT_VIDEO_EXTENSION_SET = new Set(['.mp4', '.mkv', '.mov', '.webm', '.avi', '.ts'])
+const CHAT_TEXT_EXTENSION_SET = new Set(['.txt', '.md', '.rst'])
+const CHAT_FILE_PICKER_FILTERS = [
+  { name: 'Documents and Media', extensions: CHAT_FILE_EXTENSION_LIST.map(extension => extension.slice(1)) },
+]
+
+function getFileExtension(value) {
+  const text = String(value || '').trim()
+  const match = /(?:\.([A-Za-z0-9]+))$/.exec(text)
+  return match ? `.${match[1].toLowerCase()}` : ''
+}
+
+function getFileName(value, fallback = 'attachment') {
+  const text = String(value || '').trim()
+  if (!text) return fallback
+  const parts = text.split(/[\\/]/)
+  return parts[parts.length - 1] || fallback
+}
+
+function guessMimeTypeFromName(value) {
+  const extension = getFileExtension(value)
+  switch (extension) {
+    case '.pdf': return 'application/pdf'
+    case '.html':
+    case '.htm': return 'text/html'
+    case '.txt': return 'text/plain'
+    case '.md': return 'text/markdown'
+    case '.rst': return 'text/x-rst'
+    case '.epub': return 'application/epub+zip'
+    case '.mp3': return 'audio/mpeg'
+    case '.wav': return 'audio/wav'
+    case '.m4a': return 'audio/mp4'
+    case '.flac': return 'audio/flac'
+    case '.ogg': return 'audio/ogg'
+    case '.opus': return 'audio/opus'
+    case '.aac': return 'audio/aac'
+    case '.mp4': return 'video/mp4'
+    case '.mkv': return 'video/x-matroska'
+    case '.mov': return 'video/quicktime'
+    case '.webm': return 'video/webm'
+    case '.avi': return 'video/x-msvideo'
+    case '.ts': return 'video/mp2t'
+    default: return ''
+  }
+}
+
+function attachmentIsImage(attachment) {
+  return Boolean(attachment?.data_url) || String(attachment?.kind || '').toLowerCase() === 'image'
+}
+
+function attachmentIsFile(attachment) {
+  return Boolean(attachment) && !attachmentIsImage(attachment)
+}
+
+function isSupportedChatFilePath(value) {
+  return CHAT_FILE_EXTENSION_SET.has(getFileExtension(value))
+}
+
+function isSupportedChatImagePath(value) {
+  return CHAT_IMAGE_EXTENSION_SET.has(getFileExtension(value))
+}
+
+function isSupportedChatFile(file) {
+  if (!file || isImageFile(file)) return false
+  return isSupportedChatFilePath(file.name || '')
+}
+
+function getAttachmentDisplayName(attachment, fallback = 'attachment') {
+  return String(attachment?.name || '').trim() || getFileName(attachment?.source_path, fallback)
+}
+
+function getFileAttachmentBadge(attachment) {
+  const mimeType = String(attachment?.mime_type || '').toLowerCase()
+  const extension = getFileExtension(attachment?.name || attachment?.source_path || '')
+  if (mimeType.startsWith('audio/') || CHAT_AUDIO_EXTENSION_SET.has(extension)) return 'AUDIO'
+  if (mimeType.startsWith('video/') || CHAT_VIDEO_EXTENSION_SET.has(extension)) return 'VIDEO'
+  if (CHAT_TEXT_EXTENSION_SET.has(extension)) return 'TEXT'
+  return 'DOC'
+}
+
+function buildComposerAttachmentId(prefix = 'attachment') {
+  return `${prefix}-${Date.now()}-${Math.random().toString(36).slice(2)}`
+}
+
+function buildComposerFileAttachment({ sourcePath, name, mimeType, size }) {
+  const displayName = String(name || '').trim() || getFileName(sourcePath, 'file')
+  return {
+    id: buildComposerAttachmentId('file'),
+    kind: 'file',
+    name: displayName,
+    mime_type: String(mimeType || '').trim() || guessMimeTypeFromName(displayName || sourcePath),
+    source_path: sourcePath,
+    size: Number.isFinite(Number(size)) ? Number(size) : undefined,
+  }
+}
+
+function AttachmentStrip({ attachments, className = '', removable = false, onRemove }) {
   if (!Array.isArray(attachments) || attachments.length === 0) {
     return null;
   }
 
   return (
-    <div className={`image-attachment-strip ${className}`.trim()}>
+    <div className={`attachment-strip ${className}`.trim()}>
       {attachments.map((attachment, index) => {
-        const src = attachment?.data_url;
-        if (!src) return null;
+        const isImage = attachmentIsImage(attachment)
+        const keySeed = isImage
+          ? attachment?.data_url?.length || attachment?.name || index
+          : attachment?.source_path || attachment?.name || index
+        const key = attachment.id || `${getAttachmentDisplayName(attachment, 'attachment')}-${index}-${keySeed}`
 
-        const key = attachment.id || `${attachment.name || 'image'}-${index}-${src.length}`;
+        if (isImage) {
+          const src = attachment?.data_url
+          if (!src) return null
+          return (
+            <div key={key} className="image-attachment-card">
+              {removable && (
+                <button
+                  type="button"
+                  className="attachment-remove"
+                  onClick={() => onRemove?.(attachment.id)}
+                  aria-label={`Remove ${getAttachmentDisplayName(attachment, 'image')}`}
+                  title="Remove attachment"
+                >
+                  ×
+                </button>
+              )}
+              <img
+                className="image-attachment-thumb"
+                src={src}
+                alt={getAttachmentDisplayName(attachment, `Attachment ${index + 1}`)}
+                loading="lazy"
+              />
+            </div>
+          )
+        }
+
+        const label = getAttachmentDisplayName(attachment, `Attachment ${index + 1}`)
         return (
-          <div key={key} className="image-attachment-card">
+          <div
+            key={key}
+            className="file-attachment-card"
+            title={attachment?.source_path || label}
+          >
             {removable && (
               <button
                 type="button"
-                className="image-attachment-remove"
+                className="attachment-remove attachment-remove--file"
                 onClick={() => onRemove?.(attachment.id)}
-                aria-label={`Remove ${attachment.name || 'image'}`}
-                title="Remove image"
+                aria-label={`Remove ${label}`}
+                title="Remove attachment"
               >
                 ×
               </button>
             )}
-            <img
-              className="image-attachment-thumb"
-              src={src}
-              alt={attachment.name || `Attachment ${index + 1}`}
-              loading="lazy"
-            />
+            <span className="file-attachment-badge">{getFileAttachmentBadge(attachment)}</span>
+            <span className="file-attachment-name">{label}</span>
           </div>
-        );
+        )
       })}
     </div>
   );