fix: convert dragged file paths to @mentions for attachment

When non-image files are dragged into the terminal, the file path was
inserted as plain text and never attached. Now detected absolute paths
are converted to @mentions so they get picked up by the attachment system.

src/components/PromptInput/PromptInput.tsx

@@ -67,6 +67,7 @@ import { isBilledAsExtraUsage } from '../../utils/extraUsage.js';
 import { getFastModeUnavailableReason, isFastModeAvailable, isFastModeCooldown, isFastModeEnabled, isFastModeSupportedByModel } from '../../utils/fastMode.js';
 import { isFullscreenEnvEnabled } from '../../utils/fullscreen.js';
 import type { PromptInputHelpers } from '../../utils/handlePromptSubmit.js';
+import { extractDraggedFilePaths } from '../../utils/dragDropPaths.js';
 import { getImageFromClipboard, PASTE_THRESHOLD } from '../../utils/imagePaste.js';
 import type { ImageDimensions } from '../../utils/imageResizer.js';
 import { cacheImagePath, storeImage } from '../../utils/imageStore.js';
@@ -1204,6 +1205,22 @@ function PromptInput({
     // Clean up pasted text - strip ANSI escape codes and normalize line endings and tabs
     let text = stripAnsi(rawText).replace(/\r/g, '\n').replaceAll('\t', '    ');
 
+    // Detect file paths from drag-and-drop and convert to @mentions.
+    // When files are dragged into the terminal, the terminal sends their
+    // absolute paths via bracketed paste. Image files are handled by the
+    // image paste handler upstream; here we handle non-image files by
+    // converting them to @mentions so they get attached on submit.
+    const draggedPaths = extractDraggedFilePaths(text);
+    if (draggedPaths.length > 0) {
+      const mentions = draggedPaths
+        .map(p => (p.includes(' ') ? `@"${p}"` : `@${p}`))
+        .join(' ');
+      // Ensure spacing around the mention(s) relative to existing input
+      const charBefore = input[cursorOffset - 1];
+      const prefix = charBefore && !/\s/.test(charBefore) ? ' ' : '';
+      text = prefix + mentions + ' ';
+    }
+
     // Match typed/auto-suggest: `!cmd` pasted into empty input enters bash mode.
     if (input.length === 0) {
       const pastedMode = getModeFromInput(text);

src/utils/dragDropPaths.ts

@@ -0,0 +1,47 @@
+import { isAbsolute } from 'path'
+import { getFsImplementation } from './fsOperations.js'
+import { isImageFilePath } from './imagePaste.js'
+
+/**
+ * Detect absolute file paths in pasted text (typically from drag-and-drop).
+ * Returns the cleaned paths if ALL segments are existing non-image files,
+ * or an empty array otherwise.
+ *
+ * Splitting logic mirrors usePasteHandler: space preceding `/` or a Windows
+ * drive letter, plus newline separators.
+ */
+export function extractDraggedFilePaths(text: string): string[] {
+  const segments = text
+    .split(/ (?=\/|[A-Za-z]:\\)/)
+    .flatMap(part => part.split('\n'))
+    .map(s => s.trim())
+    .filter(Boolean)
+
+  if (segments.length === 0) return []
+
+  const fs = getFsImplementation()
+  const cleaned: string[] = []
+
+  for (const raw of segments) {
+    // Strip outer quotes and shell-escape backslashes
+    let p = raw
+    if (
+      (p.startsWith('"') && p.endsWith('"')) ||
+      (p.startsWith("'") && p.endsWith("'"))
+    ) {
+      p = p.slice(1, -1)
+    }
+    if (process.platform !== 'win32') {
+      p = p.replace(/\\(.)/g, '$1')
+    }
+
+    if (!isAbsolute(p)) return []
+    // Image files are handled by the upstream image paste handler
+    if (isImageFilePath(raw)) return []
+    // Verify the path actually exists on disk
+    if (!fs.existsSync(p)) return []
+    cleaned.push(p)
+  }
+
+  return cleaned
+}