diff --git a/src/pages/views/codeeditor/CodeEditor.module.css b/src/pages/views/codeeditor/CodeEditor.module.css
index 96ce517..934aaf5 100644
--- a/src/pages/views/codeeditor/CodeEditor.module.css
+++ b/src/pages/views/codeeditor/CodeEditor.module.css
@@ -74,6 +74,12 @@
   color: var(--text-secondary, #666);
 }
 
+.dragHint {
+  font-size: 11px;
+  color: var(--text-secondary, #999);
+  font-style: italic;
+}
+
 .fileItems {
   flex: 1;
   overflow-y: auto;
@@ -84,8 +90,8 @@
   display: flex;
   align-items: center;
   gap: 8px;
-  padding: 8px 16px;
-  cursor: pointer;
+  padding: 6px 16px;
+  cursor: grab;
   transition: background 0.1s;
 }
 
@@ -93,13 +99,32 @@
   background: var(--hover-bg, #f5f5f5);
 }
 
-.fileItemSelected {
-  background: var(--selected-bg, #e8f0fe);
+.fileItem:active {
+  cursor: grabbing;
+  opacity: 0.7;
 }
 
-.fileCheckbox {
-  color: var(--primary-color, #4a90d9);
+.dragHandle {
+  color: var(--text-secondary, #ccc);
   flex-shrink: 0;
+  font-size: 10px;
+}
+
+.fileItem:hover .dragHandle {
+  color: var(--text-secondary, #999);
+}
+
+.dateGroup {
+  margin-bottom: 4px;
+}
+
+.dateGroupHeader {
+  padding: 6px 16px 2px;
+  font-size: 11px;
+  font-weight: 600;
+  color: var(--text-secondary, #999);
+  text-transform: uppercase;
+  letter-spacing: 0.5px;
 }
 
 .fileIcon {
@@ -161,6 +186,12 @@
   background: var(--disabled-bg, #f5f5f5);
 }
 
+.inputDropTarget {
+  border-color: var(--primary-color, #4a90d9);
+  background: var(--selected-bg, #e8f0fe);
+  box-shadow: 0 0 0 2px var(--primary-color, #4a90d9) inset;
+}
+
 /* Mode Toggle */
 .modeToggle {
   display: flex;
diff --git a/src/pages/views/codeeditor/CodeEditorPage.tsx b/src/pages/views/codeeditor/CodeEditorPage.tsx
index fc8d1f0..05c2245 100644
--- a/src/pages/views/codeeditor/CodeEditorPage.tsx
+++ b/src/pages/views/codeeditor/CodeEditorPage.tsx
@@ -3,7 +3,7 @@
  * 
  * Main page for the CodeEditor feature.
  * Three-panel layout: FileList (left) | Chat (center) | DiffPreview (right)
- * Supports simple mode (Phase 1) and agent mode (Phase 2).
+ * Files are dragged from FileList into the prompt textarea as @fileName references.
  */
 
 import React, { useState, useRef, useCallback } from 'react';
@@ -22,11 +22,10 @@ export const CodeEditorPage: React.FC = () => {
   const inputRef = useRef<HTMLTextAreaElement>(null);
   const [inputValue, setInputValue] = useState('');
   const [mode, setMode] = useState<'simple' | 'agent'>('simple');
+  const [isDragOver, setIsDragOver] = useState(false);
 
   const {
     messages,
-    selectedFileIds,
-    toggleFileSelection,
     pendingEdits,
     acceptEdit,
     rejectEdit,
@@ -64,9 +63,9 @@ export const CodeEditorPage: React.FC = () => {
   const handleSubmit = useCallback(() => {
     const trimmed = inputValue.trim();
     if (!trimmed || isProcessing) return;
-    sendMessage(trimmed, selectedFileIds, mode);
+    sendMessage(trimmed, mode);
     setInputValue('');
-  }, [inputValue, isProcessing, sendMessage, selectedFileIds, mode]);
+  }, [inputValue, isProcessing, sendMessage, mode]);
 
   const handleKeyDown = useCallback((e: React.KeyboardEvent) => {
     if (e.key === 'Enter' && !e.shiftKey) {
@@ -75,6 +74,50 @@ export const CodeEditorPage: React.FC = () => {
     }
   }, [handleSubmit]);
 
+  const handleDragOver = useCallback((e: React.DragEvent) => {
+    if (e.dataTransfer.types.includes('application/x-codeeditor-file')) {
+      e.preventDefault();
+      e.dataTransfer.dropEffect = 'copy';
+      setIsDragOver(true);
+    }
+  }, []);
+
+  const handleDragLeave = useCallback(() => {
+    setIsDragOver(false);
+  }, []);
+
+  const handleDrop = useCallback((e: React.DragEvent) => {
+    e.preventDefault();
+    setIsDragOver(false);
+
+    const fileDataStr = e.dataTransfer.getData('application/x-codeeditor-file');
+    if (!fileDataStr) return;
+
+    try {
+      const fileData = JSON.parse(fileDataStr);
+      const tag = `@${fileData.fileName}`;
+      const textarea = inputRef.current;
+      if (textarea) {
+        const pos = textarea.selectionStart || inputValue.length;
+        const before = inputValue.slice(0, pos);
+        const after = inputValue.slice(pos);
+        const spaceBefore = before.length > 0 && !before.endsWith(' ') && !before.endsWith('\n') ? ' ' : '';
+        const spaceAfter = after.length > 0 && !after.startsWith(' ') && !after.startsWith('\n') ? ' ' : '';
+        const newValue = `${before}${spaceBefore}${tag}${spaceAfter}${after}`;
+        setInputValue(newValue);
+        requestAnimationFrame(() => {
+          const newPos = pos + spaceBefore.length + tag.length + spaceAfter.length;
+          textarea.focus();
+          textarea.setSelectionRange(newPos, newPos);
+        });
+      } else {
+        setInputValue(prev => prev + (prev && !prev.endsWith(' ') ? ' ' : '') + tag + ' ');
+      }
+    } catch {
+      // ignore malformed drop data
+    }
+  }, [inputValue]);
+
   return (
     <div className={styles.container}>
       <div
@@ -83,11 +126,7 @@ export const CodeEditorPage: React.FC = () => {
       >
         {/* Left: File List */}
         <div className={styles.filePanel} style={{ width: `${fileListWidth}%` }}>
-          <FileListPanel
-            files={files}
-            selectedFileIds={selectedFileIds}
-            onToggle={toggleFileSelection}
-          />
+          <FileListPanel files={files} />
         </div>
 
         <div className={styles.divider} onMouseDown={fileListMouseDown} />
@@ -116,7 +155,7 @@ export const CodeEditorPage: React.FC = () => {
                   className={`${styles.modeButton} ${mode === 'simple' ? styles.modeActive : ''}`}
                   onClick={() => setMode('simple')}
                   disabled={isProcessing}
-                  title="Single AI call with selected files as context"
+                  title="Single AI call -- drag files into prompt as @references"
                 >
                   <FaEdit /> Simple
                 </button>
@@ -132,21 +171,24 @@ export const CodeEditorPage: React.FC = () => {
 
               <textarea
                 ref={inputRef}
-                className={styles.input}
+                className={`${styles.input} ${isDragOver ? styles.inputDropTarget : ''}`}
                 value={inputValue}
                 onChange={(e) => setInputValue(e.target.value)}
                 onKeyDown={handleKeyDown}
+                onDragOver={handleDragOver}
+                onDragLeave={handleDragLeave}
+                onDrop={handleDrop}
                 placeholder={mode === 'agent'
                   ? "Describe a complex task (e.g. 'Document all Python files')..."
-                  : "Describe what you want to change..."
+                  : "Drag files here and describe changes (e.g. 'In @config.yaml change the port to 8080')..."
                 }
-                rows={2}
+                rows={3}
                 disabled={isProcessing}
               />
               <div className={styles.inputActions}>
                 <span className={styles.fileCount}>
                   {mode === 'simple'
-                    ? `${selectedFileIds.length} file(s) selected`
+                    ? `Drag files from the list into your prompt`
                     : `Agent mode: AI reads files autonomously`
                   }
                 </span>
diff --git a/src/pages/views/codeeditor/FileListPanel.tsx b/src/pages/views/codeeditor/FileListPanel.tsx
index 60b6255..7f5468a 100644
--- a/src/pages/views/codeeditor/FileListPanel.tsx
+++ b/src/pages/views/codeeditor/FileListPanel.tsx
@@ -1,12 +1,12 @@
 /**
  * FileListPanel
  * 
- * Lists uploaded text files with checkbox selection.
- * Selected files are sent as context to the AI.
+ * Lists text files grouped by date, draggable into the prompt textarea.
+ * Drag a file into the chat input to insert an @fileName reference.
  */
 
-import React from 'react';
-import { FaFile, FaCheckSquare, FaRegSquare } from 'react-icons/fa';
+import React, { useMemo } from 'react';
+import { FaFile, FaGripVertical } from 'react-icons/fa';
 import styles from './CodeEditor.module.css';
 
 export interface FileInfo {
@@ -14,48 +14,95 @@ export interface FileInfo {
   fileName: string;
   mimeType: string;
   sizeBytes: number;
+  modifiedAt?: number;
 }
 
 interface FileListPanelProps {
   files: FileInfo[];
-  selectedFileIds: string[];
-  onToggle: (fileId: string) => void;
 }
 
-export const FileListPanel: React.FC<FileListPanelProps> = ({ files, selectedFileIds, onToggle }) => {
+interface DateGroup {
+  label: string;
+  files: FileInfo[];
+}
+
+export const FileListPanel: React.FC<FileListPanelProps> = ({ files }) => {
+  const groups = useMemo(() => _groupByDate(files), [files]);
+
+  const handleDragStart = (e: React.DragEvent, file: FileInfo) => {
+    e.dataTransfer.setData('application/x-codeeditor-file', JSON.stringify({
+      fileId: file.fileId,
+      fileName: file.fileName,
+    }));
+    e.dataTransfer.setData('text/plain', `@${file.fileName}`);
+    e.dataTransfer.effectAllowed = 'copy';
+  };
+
   return (
     <div className={styles.fileList}>
       <div className={styles.panelHeader}>
         <h3>Files ({files.length})</h3>
-        <span className={styles.selectedCount}>{selectedFileIds.length} selected</span>
+        <span className={styles.dragHint}>drag into prompt</span>
       </div>
       <div className={styles.fileItems}>
         {files.length === 0 ? (
           <div className={styles.emptyState}>No text files uploaded yet</div>
         ) : (
-          files.map((file) => {
-            const isSelected = selectedFileIds.includes(file.fileId);
-            return (
-              <div
-                key={file.fileId}
-                className={`${styles.fileItem} ${isSelected ? styles.fileItemSelected : ''}`}
-                onClick={() => onToggle(file.fileId)}
-              >
-                <span className={styles.fileCheckbox}>
-                  {isSelected ? <FaCheckSquare /> : <FaRegSquare />}
-                </span>
-                <FaFile className={styles.fileIcon} />
-                <span className={styles.fileName}>{file.fileName}</span>
-                <span className={styles.fileSize}>{_formatSize(file.sizeBytes)}</span>
-              </div>
-            );
-          })
+          groups.map((group) => (
+            <div key={group.label} className={styles.dateGroup}>
+              <div className={styles.dateGroupHeader}>{group.label}</div>
+              {group.files.map((file) => (
+                <div
+                  key={file.fileId}
+                  className={styles.fileItem}
+                  draggable
+                  onDragStart={(e) => handleDragStart(e, file)}
+                >
+                  <FaGripVertical className={styles.dragHandle} />
+                  <FaFile className={styles.fileIcon} />
+                  <span className={styles.fileName}>{file.fileName}</span>
+                  <span className={styles.fileSize}>{_formatSize(file.sizeBytes)}</span>
+                </div>
+              ))}
+            </div>
+          ))
         )}
       </div>
     </div>
   );
 };
 
+function _groupByDate(files: FileInfo[]): DateGroup[] {
+  const now = new Date();
+  const todayStart = new Date(now.getFullYear(), now.getMonth(), now.getDate()).getTime() / 1000;
+  const yesterdayStart = todayStart - 86400;
+
+  const today: FileInfo[] = [];
+  const yesterday: FileInfo[] = [];
+  const older: FileInfo[] = [];
+
+  const sorted = [...files].sort((a, b) => (b.modifiedAt || 0) - (a.modifiedAt || 0));
+
+  for (const file of sorted) {
+    const ts = file.modifiedAt || 0;
+    if (ts >= todayStart) {
+      today.push(file);
+    } else if (ts >= yesterdayStart) {
+      yesterday.push(file);
+    } else {
+      older.push(file);
+    }
+  }
+
+  const groups: DateGroup[] = [];
+  if (today.length > 0) groups.push({ label: 'Today', files: today });
+  if (yesterday.length > 0) groups.push({ label: 'Yesterday', files: yesterday });
+  if (older.length > 0) groups.push({ label: 'Older', files: older });
+  if (groups.length === 0 && files.length > 0) groups.push({ label: 'All files', files: sorted });
+
+  return groups;
+}
+
 function _formatSize(bytes: number): string {
   if (bytes < 1024) return `${bytes} B`;
   if (bytes < 1024 * 1024) return `${(bytes / 1024).toFixed(1)} KB`;
diff --git a/src/pages/views/codeeditor/useCodeEditor.ts b/src/pages/views/codeeditor/useCodeEditor.ts
index 2101563..e4513cd 100644
--- a/src/pages/views/codeeditor/useCodeEditor.ts
+++ b/src/pages/views/codeeditor/useCodeEditor.ts
@@ -1,8 +1,8 @@
 /**
  * useCodeEditor Hook
  * 
- * Manages SSE connection, file selection, message state, edit proposals,
- * and agent mode progress for the CodeEditor feature.
+ * Manages SSE connection, message state, edit proposals, and agent progress.
+ * File references are extracted from @fileName tags in the prompt text.
  */
 
 import { useState, useCallback, useRef, useEffect } from 'react';
@@ -21,13 +21,11 @@ export interface AgentProgress {
 
 interface UseCodeEditorReturn {
   messages: Message[];
-  selectedFileIds: string[];
-  toggleFileSelection: (fileId: string) => void;
   pendingEdits: FileEditProposal[];
   acceptEdit: (editId: string) => void;
   rejectEdit: (editId: string) => void;
   isProcessing: boolean;
-  sendMessage: (prompt: string, fileIds: string[], mode?: 'simple' | 'agent') => void;
+  sendMessage: (prompt: string, mode?: 'simple' | 'agent') => void;
   stopProcessing: () => void;
   files: FileInfo[];
   agentProgress: AgentProgress | null;
@@ -35,7 +33,6 @@ interface UseCodeEditorReturn {
 
 export function useCodeEditor(instanceId: string): UseCodeEditorReturn {
   const [messages, setMessages] = useState<Message[]>([]);
-  const [selectedFileIds, setSelectedFileIds] = useState<string[]>([]);
   const [pendingEdits, setPendingEdits] = useState<FileEditProposal[]>([]);
   const [isProcessing, setIsProcessing] = useState(false);
   const [files, setFiles] = useState<FileInfo[]>([]);
@@ -48,15 +45,11 @@ export function useCodeEditor(instanceId: string): UseCodeEditorReturn {
     _loadFiles(instanceId, setFiles);
   }, [instanceId]);
 
-  const toggleFileSelection = useCallback((fileId: string) => {
-    setSelectedFileIds(prev =>
-      prev.includes(fileId) ? prev.filter(id => id !== fileId) : [...prev, fileId]
-    );
-  }, []);
-
-  const sendMessage = useCallback((prompt: string, fileIds: string[], mode: 'simple' | 'agent' = 'simple') => {
+  const sendMessage = useCallback((prompt: string, mode: 'simple' | 'agent' = 'simple') => {
     if (!instanceId || isProcessing) return;
 
+    const referencedFileIds = _extractFileRefs(prompt, files);
+
     setIsProcessing(true);
     setAgentProgress(null);
     setMessages(prev => [...prev, {
@@ -96,7 +89,7 @@ export function useCodeEditor(instanceId: string): UseCodeEditorReturn {
       headers,
       body: JSON.stringify({
         prompt: prompt,
-        listFileId: fileIds,
+        listFileId: referencedFileIds,
       }),
       credentials: 'include',
       signal: abortRef.current.signal,
@@ -150,7 +143,7 @@ export function useCodeEditor(instanceId: string): UseCodeEditorReturn {
       }]);
       setIsProcessing(false);
     });
-  }, [instanceId, isProcessing, workflowId]);
+  }, [instanceId, isProcessing, workflowId, files]);
 
   const stopProcessing = useCallback(() => {
     if (abortRef.current) {
@@ -185,8 +178,6 @@ export function useCodeEditor(instanceId: string): UseCodeEditorReturn {
 
   return {
     messages,
-    selectedFileIds,
-    toggleFileSelection,
     pendingEdits,
     acceptEdit,
     rejectEdit,
@@ -204,6 +195,22 @@ function _loadFiles(instanceId: string, setFiles: React.Dispatch<React.SetStateA
     .catch(err => console.error('Failed to load files:', err));
 }
 
+function _extractFileRefs(prompt: string, files: FileInfo[]): string[] {
+  const atPattern = /@([\w.\-]+)/g;
+  const matchedIds: string[] = [];
+  let match;
+
+  while ((match = atPattern.exec(prompt)) !== null) {
+    const refName = match[1];
+    const file = files.find(f => f.fileName === refName || f.fileName.toLowerCase() === refName.toLowerCase());
+    if (file && !matchedIds.includes(file.fileId)) {
+      matchedIds.push(file.fileId);
+    }
+  }
+
+  return matchedIds;
+}
+
 function _handleSseEvent(
   event: any,
   setMessages: React.Dispatch<React.SetStateAction<Message[]>>,