diff --git a/src/__tests__/unit/claude-session-parser.test.ts b/src/__tests__/unit/claude-session-parser.test.ts
index b3d94b00..51a5a296 100644
--- a/src/__tests__/unit/claude-session-parser.test.ts
+++ b/src/__tests__/unit/claude-session-parser.test.ts
@@ -10,12 +10,19 @@ import assert from 'node:assert/strict';
 import fs from 'fs';
 import path from 'path';
 import os from 'os';
+import { pathToFileURL } from 'node:url';
 
 // We test the parser functions by creating temporary JSONL files
 // that mimic Claude Code's session storage format.
 
 const TEST_DIR = path.join(os.tmpdir(), `codepilot-test-sessions-${Date.now()}`);
 const PROJECTS_DIR = path.join(TEST_DIR, '.claude', 'projects');
+const originalEnv = {
+  HOME: process.env.HOME,
+  USERPROFILE: process.env.USERPROFILE,
+  HOMEDRIVE: process.env.HOMEDRIVE,
+  HOMEPATH: process.env.HOMEPATH,
+};
 
 // Helper to create a JSONL session file
 function createSessionFile(
@@ -121,18 +128,25 @@ describe('claude-session-parser', () => {
   let parser: typeof import('../../lib/claude-session-parser');
 
   before(async () => {
-    // Set HOME to our test directory so the parser looks for sessions there
+    // Point all common home env vars to test dir so os.homedir() is deterministic on Windows/macOS/Linux.
+    const parsed = path.parse(TEST_DIR);
     process.env.HOME = TEST_DIR;
+    process.env.USERPROFILE = TEST_DIR;
+    process.env.HOMEDRIVE = parsed.root.replace(/[\\\/]$/, '');
+    process.env.HOMEPATH = TEST_DIR.slice(parsed.root.length - 1);
 
     // Dynamic import - tsx handles the TypeScript + path alias resolution
-    parser = await import(parserPath);
+    parser = await import(pathToFileURL(parserPath).href);
   });
 
   after(() => {
     // Clean up test directory
     fs.rmSync(TEST_DIR, { recursive: true, force: true });
-    // Restore HOME
-    process.env.HOME = os.homedir();
+    // Restore env
+    process.env.HOME = originalEnv.HOME;
+    process.env.USERPROFILE = originalEnv.USERPROFILE;
+    process.env.HOMEDRIVE = originalEnv.HOMEDRIVE;
+    process.env.HOMEPATH = originalEnv.HOMEPATH;
   });
 
   describe('decodeProjectPath', () => {
diff --git a/src/components/ai-elements/file-tree.tsx b/src/components/ai-elements/file-tree.tsx
index b2b7015b..9d56ebc0 100644
--- a/src/components/ai-elements/file-tree.tsx
+++ b/src/components/ai-elements/file-tree.tsx
@@ -24,6 +24,10 @@ import {
   useState,
 } from "react";
 
+const FILE_TREE_DRAG_MIME = "application/x-codepilot-path";
+// Keep a text/* fallback because some drag-and-drop consumers strip unknown custom MIME types.
+const FILE_TREE_DRAG_FALLBACK_MIME = "text/x-codepilot-path";
+
 interface FileTreeContextType {
   expandedPaths: Set<string>;
   togglePath: (path: string) => void;
@@ -132,6 +136,17 @@ export const FileTreeFolder = ({
     togglePath(path);
   }, [togglePath, path]);
 
+  const handleDragStart = useCallback(
+    (e: React.DragEvent) => {
+      const payload = JSON.stringify({ path, name, type: "directory" });
+      e.dataTransfer.setData(FILE_TREE_DRAG_MIME, payload);
+      e.dataTransfer.setData(FILE_TREE_DRAG_FALLBACK_MIME, payload);
+      e.dataTransfer.setData("text/plain", path);
+      e.dataTransfer.effectAllowed = "copy";
+    },
+    [name, path]
+  );
+
   const folderContextValue = useMemo(
     () => ({ isExpanded, name, path }),
     [isExpanded, name, path]
@@ -148,6 +163,8 @@ export const FileTreeFolder = ({
         >
           <div
             className="flex w-full items-center gap-1 rounded px-2 py-1 text-left transition-colors hover:bg-muted/50"
+            draggable
+            onDragStart={handleDragStart}
           >
             <CollapsibleTrigger asChild>
               <button
@@ -232,6 +249,17 @@ export const FileTreeFile = ({
 
   const fileContextValue = useMemo(() => ({ name, path }), [name, path]);
 
+  const handleDragStart = useCallback(
+    (e: React.DragEvent) => {
+      const payload = JSON.stringify({ path, name, type: "file" });
+      e.dataTransfer.setData(FILE_TREE_DRAG_MIME, payload);
+      e.dataTransfer.setData(FILE_TREE_DRAG_FALLBACK_MIME, payload);
+      e.dataTransfer.setData("text/plain", path);
+      e.dataTransfer.effectAllowed = "copy";
+    },
+    [name, path]
+  );
+
   return (
     <FileTreeFileContext.Provider value={fileContextValue}>
       <div
@@ -242,6 +270,8 @@ export const FileTreeFile = ({
         )}
         onClick={handleClick}
         onKeyDown={handleKeyDown}
+        draggable
+        onDragStart={handleDragStart}
         role="treeitem"
         tabIndex={0}
         {...props}
diff --git a/src/components/chat/MessageInput.tsx b/src/components/chat/MessageInput.tsx
index b3039232..8588b6ce 100644
--- a/src/components/chat/MessageInput.tsx
+++ b/src/components/chat/MessageInput.tsx
@@ -19,6 +19,8 @@ import {
   BrainIcon,
   GlobalIcon,
   StopIcon,
+  Folder01Icon,
+  File01Icon,
 } from "@hugeicons/core-free-icons";
 import { cn } from '@/lib/utils';
 import { useTranslation } from '@/hooks/useTranslation';
@@ -81,6 +83,36 @@ const IMAGE_AGENT_SYSTEM_PROMPT = `你是一个图像生成助手。当用户请
 - 如果用户要求修改上一张生成的图片，必须加 "useLastGenerated": true
 - 在输出结构化块之前，可以先简要说明你的理解和计划`;
 
+const FILE_TREE_DRAG_MIME = 'application/x-codepilot-path';
+// Keep a text/* fallback because some drag-and-drop bridges drop unknown custom MIME types.
+const FILE_TREE_DRAG_FALLBACK_MIME = 'text/x-codepilot-path';
+
+function hasDragType(dataTransfer: DataTransfer | null | undefined, type: string): boolean {
+  if (!dataTransfer) return false;
+  return Array.from(dataTransfer.types).includes(type);
+}
+
+function readFileTreeDropData(dataTransfer: DataTransfer | null | undefined) {
+  if (!dataTransfer) return null;
+
+  const raw = dataTransfer.getData(FILE_TREE_DRAG_MIME)
+    || dataTransfer.getData(FILE_TREE_DRAG_FALLBACK_MIME);
+
+  if (!raw) return null;
+
+  try {
+    const parsed = JSON.parse(raw) as Partial<{ path: string; name: string; type: string }>;
+    if (!parsed.path || typeof parsed.path !== 'string') return null;
+    return {
+      name: typeof parsed.name === 'string' ? parsed.name : '',
+      path: parsed.path,
+      type: parsed.type === 'directory' ? 'directory' : 'file',
+    };
+  } catch {
+    return null;
+  }
+}
+
 
 interface MessageInputProps {
   onSend: (content: string, files?: FileAttachment[], systemPromptAppend?: string, displayOverride?: string) => void;
@@ -119,6 +151,13 @@ interface CommandBadge {
   installedSource?: "agents" | "claude";
 }
 
+interface ContextMention {
+  id: string;
+  path: string;
+  name: string;
+  type: 'file' | 'directory';
+}
+
 type PopoverMode = 'file' | 'skill' | null;
 
 // Expansion prompts for CLI-only commands (not natively supported by SDK).
@@ -190,12 +229,14 @@ function FileAwareSubmitButton({
   disabled,
   inputValue,
   hasBadge,
+  hasContextMentions,
 }: {
   status: ChatStatus;
   onStop?: () => void;
   disabled?: boolean;
   inputValue: string;
   hasBadge: boolean;
+  hasContextMentions: boolean;
 }) {
   const attachments = usePromptInputAttachments();
   const hasFiles = attachments.files.length > 0;
@@ -205,7 +246,7 @@ function FileAwareSubmitButton({
     <PromptInputSubmit
       status={status}
       onStop={onStop}
-      disabled={disabled || (!isStreaming && !inputValue.trim() && !hasBadge && !hasFiles)}
+      disabled={disabled || (!isStreaming && !inputValue.trim() && !hasBadge && !hasFiles && !hasContextMentions)}
       className="rounded-full"
     >
       {isStreaming ? (
@@ -276,7 +317,7 @@ function mimeFromFilename(name: string): string {
  * Bridge component that listens for 'attach-file-to-chat' custom events
  * from the file tree and adds files as attachments. Must be rendered inside PromptInput.
  */
-function FileTreeAttachmentBridge() {
+function FileTreeAttachmentBridge({ onAttachFailed }: { onAttachFailed?: (filePath: string) => void }) {
   const attachments = usePromptInputAttachments();
   const attachmentsRef = useRef(attachments);
 
@@ -294,6 +335,7 @@ function FileTreeAttachmentBridge() {
         const res = await fetch(`/api/files/raw?path=${encodeURIComponent(filePath)}`);
         if (!res.ok) {
           console.warn(`[FileTreeAttachment] Failed to fetch file: ${res.status} ${res.statusText}`, filePath);
+          onAttachFailed?.(filePath);
           return;
         }
         const blob = await res.blob();
@@ -306,12 +348,13 @@ function FileTreeAttachmentBridge() {
         attachmentsRef.current.add([file]);
       } catch (err) {
         console.warn('[FileTreeAttachment] Error attaching file:', filePath, err);
+        onAttachFailed?.(filePath);
       }
     };
 
     window.addEventListener('attach-file-to-chat', handler);
     return () => window.removeEventListener('attach-file-to-chat', handler);
-  }, []);
+  }, [onAttachFailed]);
 
   return null;
 }
@@ -358,6 +401,58 @@ function FileAttachmentsCapsules() {
   );
 }
 
+function getMentionColorClasses(mention: ContextMention): { chip: string; hover: string } {
+  if (mention.type === 'directory') {
+    return {
+      chip: "bg-amber-500/10 text-amber-600 dark:text-amber-400 border-amber-500/20",
+      hover: "hover:bg-amber-500/20",
+    };
+  }
+  return {
+    chip: "bg-blue-500/10 text-blue-600 dark:text-blue-400 border-blue-500/20",
+    hover: "hover:bg-blue-500/20",
+  };
+}
+
+function ContextMentionChips({
+  mentions,
+  onRemove,
+}: {
+  mentions: ContextMention[];
+  onRemove: (id: string) => void;
+}) {
+  const { t } = useTranslation();
+  if (mentions.length === 0) return null;
+  return (
+    <div className="flex w-full flex-wrap items-center gap-1.5 px-3 pt-2 pb-0 order-first">
+      {mentions.map((m) => {
+        const colors = getMentionColorClasses(m);
+        return (
+          <span
+            key={m.id}
+            className={cn(
+              "inline-flex items-center gap-1 rounded-full pl-2 pr-1 py-0.5 text-xs font-medium border min-w-0",
+              colors.chip
+            )}
+          >
+            <HugeiconsIcon icon={m.type === 'directory' ? Folder01Icon : File01Icon} className="h-3 w-3 shrink-0" />
+            <span className="truncate text-[11px] font-mono">{m.name}</span>
+            <button
+              type="button"
+              onClick={() => onRemove(m.id)}
+              aria-label={t('messageInput.removeContextMention', { name: m.name })}
+              title={t('messageInput.removeContextMention', { name: m.name })}
+              className={cn("ml-auto shrink-0 rounded-full p-0.5 transition-colors", colors.hover)}
+            >
+              <HugeiconsIcon icon={Cancel01Icon} className="h-3 w-3" />
+            </button>
+          </span>
+        );
+      })}
+    </div>
+  );
+}
+
 export function MessageInput({
   onSend,
   onImageGenerate,
@@ -380,6 +475,7 @@ export function MessageInput({
   const popoverRef = useRef<HTMLDivElement>(null);
   const searchInputRef = useRef<HTMLInputElement>(null);
   const modelMenuRef = useRef<HTMLDivElement>(null);
+  const dropZoneRef = useRef<HTMLDivElement>(null);
 
   const [popoverMode, setPopoverMode] = useState<PopoverMode>(null);
   const [popoverItems, setPopoverItems] = useState<PopoverItem[]>([]);
@@ -395,6 +491,76 @@ export function MessageInput({
   const [aiSearchLoading, setAiSearchLoading] = useState(false);
   const aiSearchAbortRef = useRef<AbortController | null>(null);
   const aiSearchTimerRef = useRef<ReturnType<typeof setTimeout> | null>(null);
+  const [isDragOver, setIsDragOver] = useState(false);
+  const [contextMentions, setContextMentions] = useState<ContextMention[]>([]);
+
+  const removeContextMention = useCallback((id: string) => {
+    setContextMentions((prev) => prev.filter((m) => m.id !== id));
+  }, []);
+
+  const addContextMention = useCallback((path: string, name: string, type: 'file' | 'directory') => {
+    setContextMentions((prev) => {
+      if (prev.some((m) => m.path === path)) return prev;
+      return [...prev, { id: nanoid(), path, name, type }];
+    });
+    setTimeout(() => textareaRef.current?.focus(), 0);
+  }, []);
+
+  const appendPathMention = useCallback((path: string) => {
+    setInputValue((prev) => {
+      const suffix = `@${path} `;
+      return prev ? `${prev}${suffix}` : suffix;
+    });
+    setTimeout(() => textareaRef.current?.focus(), 0);
+  }, []);
+
+  useEffect(() => {
+    const el = dropZoneRef.current;
+    if (!el) return;
+
+    const onDragOver = (e: DragEvent) => {
+      const isTreeDrag = hasDragType(e.dataTransfer, FILE_TREE_DRAG_MIME)
+        || hasDragType(e.dataTransfer, FILE_TREE_DRAG_FALLBACK_MIME);
+
+      if (isTreeDrag) {
+        e.preventDefault();
+        e.stopPropagation();
+        if (e.dataTransfer) e.dataTransfer.dropEffect = 'copy';
+        setIsDragOver(true);
+      }
+    };
+
+    const onDragLeave = (e: DragEvent) => {
+      if (el.contains(e.relatedTarget as Node)) return;
+      setIsDragOver(false);
+    };
+
+    const onDrop = (e: DragEvent) => {
+      setIsDragOver(false);
+      const data = readFileTreeDropData(e.dataTransfer);
+      if (!data) return;
+      e.preventDefault();
+      e.stopPropagation();
+      if (data.type === 'file') {
+        window.dispatchEvent(
+          new CustomEvent('attach-file-to-chat', { detail: { path: data.path } })
+        );
+        const mentionName = data.name || data.path.split(/[/\\]/).pop() || data.path;
+        addContextMention(data.path, mentionName, 'file');
+      } else {
+        addContextMention(data.path, data.name || data.path, 'directory');
+      }
+    };
+
+    el.addEventListener('dragover', onDragOver);
+    el.addEventListener('dragleave', onDragLeave);
+    el.addEventListener('drop', onDrop);
+    return () => {
+      el.removeEventListener('dragover', onDragOver);
+      el.removeEventListener('dragleave', onDragLeave);
+      el.removeEventListener('drop', onDrop);
+    };
+  }, [addContextMention]);
 
   // Fetch provider groups from API
   const fetchProviderModels = useCallback(() => {
@@ -602,7 +768,14 @@ export function MessageInput({
 
   const handleSubmit = useCallback(async (msg: { text: string; files: Array<{ type: string; url: string; filename?: string; mediaType?: string }> }, e: FormEvent<HTMLFormElement>) => {
     e.preventDefault();
-    const content = inputValue.trim();
+    const rawContent = inputValue.trim();
+    const mentionPrefix = contextMentions.length > 0
+      ? contextMentions
+        .filter((m) => !rawContent.includes(`@${m.path}`))
+        .map((m) => `@${m.path}`)
+        .join(' ')
+      : '';
+    const content = [mentionPrefix, rawContent].filter(Boolean).join(' ');
 
     closePopover();
 
@@ -640,6 +813,7 @@ export function MessageInput({
         deleteRefImages(PENDING_KEY);
       }
 
+      setContextMentions([]);
       setInputValue('');
       if (onSend) {
         onSend(content, files.length > 0 ? files : undefined, IMAGE_AGENT_SYSTEM_PROMPT);
@@ -679,6 +853,7 @@ export function MessageInput({
 
       const files = await convertFiles();
       setBadge(null);
+      setContextMentions([]);
       setInputValue('');
       onSend(finalPrompt, files.length > 0 ? files : undefined);
       return;
@@ -724,8 +899,9 @@ export function MessageInput({
     }
 
     onSend(content || 'Please review the attached file(s).', hasFiles ? files : undefined);
+    setContextMentions([]);
     setInputValue('');
-  }, [inputValue, onSend, onImageGenerate, onCommand, disabled, isStreaming, closePopover, badge, imageGen]);
+  }, [inputValue, onSend, onImageGenerate, onCommand, disabled, isStreaming, closePopover, badge, imageGen, contextMentions]);
 
   const filteredItems = popoverItems.filter((item) => {
     const q = popoverFilter.toLowerCase();
@@ -908,7 +1084,10 @@ export function MessageInput({
   return (
     <div className="bg-background/80 backdrop-blur-lg px-4 py-3">
       <div className="mx-auto">
-        <div className="relative">
+        <div
+          ref={dropZoneRef}
+          className={cn("relative", isDragOver && "ring-2 ring-primary/50 ring-offset-1 ring-offset-background rounded-xl")}
+        >
           {/* Popover */}
           {popoverMode && (allDisplayedItems.length > 0 || aiSearchLoading) && (() => {
             const builtInItems = filteredItems.filter(item => item.builtIn);
@@ -1068,8 +1247,7 @@ export function MessageInput({
             accept=""
             multiple
           >
-            {/* Bridge: listens for file tree "+" button events */}
-            <FileTreeAttachmentBridge />
+            <FileTreeAttachmentBridge onAttachFailed={appendPathMention} />
             {/* Command badge */}
             {badge && (
               <div className="flex w-full items-center gap-1.5 px-3 pt-2.5 pb-0 order-first">
@@ -1092,6 +1270,7 @@ export function MessageInput({
             )}
             {/* File attachment capsules */}
             <FileAttachmentsCapsules />
+            <ContextMentionChips mentions={contextMentions} onRemove={removeContextMention} />
             <PromptInputTextarea
               ref={textareaRef}
               placeholder={badge ? "Add details (optional), then press Enter..." : "Message Claude..."}
@@ -1182,15 +1361,16 @@ export function MessageInput({
                 <ImageGenToggle />
               </PromptInputTools>
 
-              <FileAwareSubmitButton
-                status={chatStatus}
-                onStop={onStop}
-                disabled={disabled}
-                inputValue={inputValue}
-                hasBadge={!!badge}
-              />
-            </PromptInputFooter>
-          </PromptInput>
+                <FileAwareSubmitButton
+                  status={chatStatus}
+                  onStop={onStop}
+                  disabled={disabled}
+                  inputValue={inputValue}
+                  hasBadge={!!badge}
+                  hasContextMentions={contextMentions.length > 0}
+                />
+              </PromptInputFooter>
+            </PromptInput>
         </div>
       </div>
 
diff --git a/src/i18n/en.ts b/src/i18n/en.ts
index 79e59448..733d30d1 100644
--- a/src/i18n/en.ts
+++ b/src/i18n/en.ts
@@ -47,6 +47,7 @@ const en = {
   'messageInput.modeCode': 'Code',
   'messageInput.modePlan': 'Plan',
   'messageInput.aiSuggested': 'AI Suggested',
+  'messageInput.removeContextMention': 'Remove context mention: {name}',
 
   // ── Streaming message ───────────────────────────────────────
   'streaming.thinking': 'Thinking...',
diff --git a/src/i18n/zh.ts b/src/i18n/zh.ts
index 4ad12106..b2c356b0 100644
--- a/src/i18n/zh.ts
+++ b/src/i18n/zh.ts
@@ -44,6 +44,7 @@ const zh: Record<TranslationKey, string> = {
   'messageInput.modeCode': '代码',
   'messageInput.modePlan': '计划',
   'messageInput.aiSuggested': 'AI 推荐',
+  'messageInput.removeContextMention': '移除上下文引用：{name}',
 
   // ── Streaming message ───────────────────────────────────────
   'streaming.thinking': '思考中...',