feat: add @ file mention support in chat input and unify directory attachment

Support typing "@" in the chat input to trigger a file list popup with
filtering, keyboard navigation, and file/directory attachment. Directories
from the sidebar file tree now attach as resource links instead of injecting
text into the input.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/components/chat/file-mention-menu.tsx

@@ -0,0 +1,62 @@
+"use client"
+
+import { useEffect, useRef } from "react"
+import { File, Folder } from "lucide-react"
+import { cn } from "@/lib/utils"
+import type { FlatFileEntry } from "@/hooks/use-file-tree"
+
+interface FileMentionMenuProps {
+  files: FlatFileEntry[]
+  selectedIndex: number
+  onSelect: (entry: FlatFileEntry) => void
+}
+
+export function FileMentionMenu({
+  files,
+  selectedIndex,
+  onSelect,
+}: FileMentionMenuProps) {
+  const listRef = useRef<HTMLDivElement>(null)
+
+  useEffect(() => {
+    const el = listRef.current?.children[selectedIndex] as
+      | HTMLElement
+      | undefined
+    el?.scrollIntoView({ block: "nearest" })
+  }, [selectedIndex])
+
+  if (files.length === 0) return null
+
+  return (
+    <div
+      ref={listRef}
+      className="absolute bottom-full left-0 right-0 z-50 mb-1 max-h-48 overflow-y-auto rounded-xl border border-border bg-popover p-1 shadow-lg"
+    >
+      {files.map((entry, i) => (
+        <button
+          key={entry.relativePath}
+          type="button"
+          className={cn(
+            "flex w-full items-center gap-2 rounded-lg px-3 py-1.5 text-left text-sm",
+            i === selectedIndex
+              ? "bg-accent text-accent-foreground"
+              : "hover:bg-muted"
+          )}
+          onMouseDown={(e) => {
+            e.preventDefault()
+            onSelect(entry)
+          }}
+        >
+          {entry.kind === "dir" ? (
+            <Folder className="h-3.5 w-3.5 shrink-0 text-muted-foreground" />
+          ) : (
+            <File className="h-3.5 w-3.5 shrink-0 text-muted-foreground" />
+          )}
+          <span className="truncate font-mono text-xs">
+            {entry.relativePath}
+          </span>
+        </button>
+      ))}
+    </div>
+  )
+}

src/components/chat/message-input.tsx

@@ -53,6 +53,9 @@ import {
 import { ModeSelector } from "@/components/chat/mode-selector"
 import { SessionConfigSelector } from "@/components/chat/session-config-selector"
 import { SlashCommandMenu } from "@/components/chat/slash-command-menu"
+import { FileMentionMenu } from "@/components/chat/file-mention-menu"
+import { useFileTree } from "@/hooks/use-file-tree"
+import { joinFsPath } from "@/lib/path-utils"
 import {
   clearMessageInputDraft,
   loadMessageInputDraft,
@@ -433,6 +436,37 @@ export function MessageInput({
     )
   }, [slashMenuOpen, slashCommands, text])
 
+  // ── @ file mention autocomplete ──
+  const [atMenuOpen, setAtMenuOpen] = useState(false)
+  const [atSelectedIndex, setAtSelectedIndex] = useState(0)
+  const [atTriggerPos, setAtTriggerPos] = useState<number | null>(null)
+  const [atFileTreeEnabled, setAtFileTreeEnabled] = useState(false)
+
+  const { allFiles: atAllFiles } = useFileTree({
+    folderPath: defaultPath,
+    enabled: atFileTreeEnabled,
+  })
+
+  const filteredAtFiles = useMemo(() => {
+    if (!atMenuOpen || atTriggerPos == null) return []
+    // Extract the query after "@" up to the next space or end of text
+    const afterAt = text.slice(atTriggerPos + 1)
+    const spaceIdx = afterAt.indexOf(" ")
+    const filter =
+      spaceIdx === -1
+        ? afterAt.toLowerCase()
+        : afterAt.slice(0, spaceIdx).toLowerCase()
+    if (!filter) return atAllFiles.slice(0, 50)
+    const matched: typeof atAllFiles = []
+    for (const f of atAllFiles) {
+      if (f.lowerName.includes(filter) || f.lowerPath.includes(filter)) {
+        matched.push(f)
+        if (matched.length >= 50) break
+      }
+    }
+    return matched
+  }, [atMenuOpen, atTriggerPos, text, atAllFiles])
+
   const appendResourceLinks = useCallback(
     (
       links: Array<{
@@ -744,18 +778,69 @@ export function MessageInput({
     setSlashMenuOpen(false)
   }, [])
 
+  const atTriggerPosRef = useRef(atTriggerPos)
+  useEffect(() => {
+    atTriggerPosRef.current = atTriggerPos
+  }, [atTriggerPos])
+
+  const handleAtSelect = useCallback(
+    (entry: { relativePath: string }) => {
+      const pos = atTriggerPosRef.current
+      if (!defaultPath || pos == null) return
+
+      // Remove the @... token from text
+      const current = textRef.current
+      const beforeAt = current.slice(0, pos)
+      const afterAt = current.slice(pos)
+      const spaceIdx = afterAt.indexOf(" ", 1)
+      const afterToken = spaceIdx === -1 ? "" : afterAt.slice(spaceIdx)
+      setText(beforeAt + afterToken)
+
+      // Attach the file
+      const absPath = joinFsPath(defaultPath, entry.relativePath)
+      appendResourceAttachments([absPath])
+
+      setAtMenuOpen(false)
+      setAtTriggerPos(null)
+
+      requestAnimationFrame(() => textareaRef.current?.focus())
+    },
+    [defaultPath, appendResourceAttachments]
+  )
+
   const handleTextChange = useCallback(
     (e: React.ChangeEvent<HTMLTextAreaElement>) => {
       const value = e.target.value
       setText(value)
+
+      // Slash command detection (only at start of input)
       if (slashCommands.length > 0 && /^\/(\S*)$/.test(value)) {
         setSlashSelectedIndex(0)
         setSlashMenuOpen(true)
+        setAtMenuOpen(false)
+        return
       } else {
         setSlashMenuOpen(false)
       }
+
+      // @ file mention detection (at any cursor position)
+      const cursorPos = e.target.selectionStart
+      if (cursorPos != null && defaultPath) {
+        const beforeCursor = value.slice(0, cursorPos)
+        const atMatch = beforeCursor.match(/(^|[\s])@([^\s]*)$/)
+        if (atMatch) {
+          const atPos =
+            beforeCursor.length - atMatch[0].length + atMatch[1].length
+          setAtTriggerPos(atPos)
+          setAtSelectedIndex(0)
+          setAtMenuOpen(true)
+          setAtFileTreeEnabled(true)
+          return
+        }
+      }
+      setAtMenuOpen(false)
     },
-    [slashCommands.length]
+    [slashCommands.length, defaultPath]
   )
 
   const handlePickFiles = useCallback(async () => {
@@ -1064,6 +1149,33 @@ export function MessageInput({
         }
       }
 
+      if (atMenuOpen && filteredAtFiles.length > 0) {
+        if (e.key === "ArrowDown") {
+          e.preventDefault()
+          setAtSelectedIndex((i) =>
+            i < filteredAtFiles.length - 1 ? i + 1 : 0
+          )
+          return
+        }
+        if (e.key === "ArrowUp") {
+          e.preventDefault()
+          setAtSelectedIndex((i) =>
+            i > 0 ? i - 1 : filteredAtFiles.length - 1
+          )
+          return
+        }
+        if (e.key === "Enter" || e.key === "Tab") {
+          e.preventDefault()
+          handleAtSelect(filteredAtFiles[atSelectedIndex])
+          return
+        }
+        if (e.key === "Escape") {
+          e.preventDefault()
+          setAtMenuOpen(false)
+          return
+        }
+      }
+
       if (isEditingQueueItem && e.key === "Escape") {
         e.preventDefault()
         onCancelQueueEdit?.()
@@ -1097,6 +1209,10 @@ export function MessageInput({
       filteredSlashCommands,
       slashSelectedIndex,
       handleSlashSelect,
+      atMenuOpen,
+      filteredAtFiles,
+      atSelectedIndex,
+      handleAtSelect,
     ]
   )
 
@@ -1270,6 +1386,13 @@ export function MessageInput({
           onSelect={handleSlashSelect}
         />
       )}
+      {atMenuOpen && filteredAtFiles.length > 0 && (
+        <FileMentionMenu
+          files={filteredAtFiles}
+          selectedIndex={atSelectedIndex}
+          onSelect={handleAtSelect}
+        />
+      )}
       <div
         className={cn(
           "flex flex-col rounded-xl border border-input bg-transparent transition-colors focus-within:border-ring focus-within:ring-[3px] focus-within:ring-ring/50",

src/components/conversations/search-command-dialog.tsx

@@ -4,23 +4,18 @@ import { useState, useEffect, useRef, useCallback, useMemo } from "react"
 import { formatDistanceToNow } from "date-fns"
 import { enUS, zhCN, zhTW } from "date-fns/locale"
 import { File, Folder } from "lucide-react"
-import ig from "ignore"
 import { useLocale, useTranslations } from "next-intl"
 import { useAuxPanelContext } from "@/contexts/aux-panel-context"
 import { useFolderContext } from "@/contexts/folder-context"
 import { useTabContext } from "@/contexts/tab-context"
 import { useWorkspaceContext } from "@/contexts/workspace-context"
-import {
+import { listFolderConversations } from "@/lib/api"
-  getFileTree,
-  listFolderConversations,
-  readFilePreview,
-} from "@/lib/api"
 import type {
   AgentType,
   ConversationStatus,
   DbConversationSummary,
-  FileTreeNode,
 } from "@/lib/types"
+import { useFileTree, type FlatFileEntry } from "@/hooks/use-file-tree"
 import { AGENT_LABELS, STATUS_COLORS, compareAgentType } from "@/lib/types"
 import { AgentIcon } from "@/components/agent-icon"
 import {
@@ -35,49 +30,6 @@ import { cn } from "@/lib/utils"
 
 type SearchTab = "conversations" | "files"
 
-interface FlatFileEntry {
-  name: string
-  /** Relative path from folder root (same as FileTreeNode.path) */
-  relativePath: string
-  kind: "file" | "dir"
-  /** Pre-computed lowercase relativePath for filtering */
-  lowerPath: string
-  /** Pre-computed lowercase name for filtering */
-  lowerName: string
-}
-
-function flattenTree(nodes: FileTreeNode[]): FlatFileEntry[] {
-  const entries: FlatFileEntry[] = []
-  function walk(node: FileTreeNode) {
-    entries.push({
-      name: node.name,
-      relativePath: node.path,
-      kind: node.kind,
-      lowerPath: node.path.toLowerCase(),
-      lowerName: node.name.toLowerCase(),
-    })
-    if (node.kind === "dir" && node.children) {
-      for (const child of node.children) {
-        walk(child)
-      }
-    }
-  }
-  for (const node of nodes) {
-    walk(node)
-  }
-  return entries
-}
-
-/** Check whether any ancestor directory of `path` is in `ignoredDirs`. */
-function hasIgnoredAncestor(path: string, ignoredDirs: Set<string>): boolean {
-  let idx = path.indexOf("/")
-  while (idx !== -1) {
-    if (ignoredDirs.has(path.slice(0, idx))) return true
-    idx = path.indexOf("/", idx + 1)
-  }
-  return false
-}
-
 interface SearchCommandDialogProps {
   open: boolean
   onOpenChange: (open: boolean) => void
@@ -103,98 +55,23 @@ export function SearchCommandDialog({
   const [searching, setSearching] = useState(false)
   const debounceRef = useRef<ReturnType<typeof setTimeout>>(undefined)
 
-  // File search state
-  const [allFiles, setAllFiles] = useState<FlatFileEntry[]>([])
-  const [filesLoading, setFilesLoading] = useState(false)
-  const filesLoadedRef = useRef(false)
-
   const folderPath = folder?.path ?? ""
 
+  // File search via shared hook (lazy-loaded when files tab is active)
+  const {
+    allFiles,
+    loading: filesLoading,
+    reset: resetFileTree,
+  } = useFileTree({
+    folderPath: folderPath || undefined,
+    enabled: activeTab === "files",
+  })
+
   // Compute which agent types exist in current folder
   const availableAgents = Array.from(
     new Set(conversations.map((c) => c.agent_type))
   ).sort(compareAgentType)
 
-  // Load file tree when switching to files tab, filtering by .gitignore
-  useEffect(() => {
-    if (activeTab !== "files" || !folderPath || filesLoadedRef.current) return
-    let canceled = false
-    setFilesLoading(true)
-
-    async function load() {
-      try {
-        const tree = await getFileTree(folderPath, 10)
-        const flat = flattenTree(tree)
-
-        // Collect all .gitignore files from the tree
-        const gitignoreEntries = flat.filter(
-          (f) => f.kind === "file" && f.name === ".gitignore"
-        )
-
-        // Build matchers keyed by directory prefix
-        const matchers: { prefix: string; matcher: ReturnType<typeof ig> }[] =
-          []
-        await Promise.all(
-          gitignoreEntries.map(async (entry) => {
-            try {
-              const result = await readFilePreview(
-                folderPath,
-                entry.relativePath
-              )
-              const lastSlash = entry.relativePath.lastIndexOf("/")
-              const dir =
-                lastSlash === -1 ? "" : entry.relativePath.slice(0, lastSlash)
-              matchers.push({
-                prefix: dir ? dir + "/" : "",
-                matcher: ig().add(result.content),
-              })
-            } catch {
-              // skip unreadable .gitignore
-            }
-          })
-        )
-
-        // Sort matchers by prefix length (shortest/root first) so that
-        // parent rules are evaluated before child rules.
-        matchers.sort((a, b) => a.prefix.length - b.prefix.length)
-
-        // Filter: check each entry against all applicable .gitignore matchers
-        const ignoredDirs = new Set<string>()
-        const filtered = flat.filter((f) => {
-          // Skip .gitignore files themselves from results
-          if (f.name === ".gitignore") return false
-          // If an ancestor directory is already ignored, skip — O(depth) lookup
-          if (hasIgnoredAncestor(f.relativePath, ignoredDirs)) return false
-          for (const { prefix, matcher } of matchers) {
-            if (!f.relativePath.startsWith(prefix)) continue
-            const relPath = f.relativePath.slice(prefix.length)
-            if (!relPath) continue
-            const testPath = f.kind === "dir" ? `${relPath}/` : relPath
-            if (matcher.ignores(testPath)) {
-              if (f.kind === "dir") ignoredDirs.add(f.relativePath)
-              return false
-            }
-          }
-          return true
-        })
-
-        if (!canceled) {
-          setAllFiles(filtered)
-          filesLoadedRef.current = true
-        }
-      } catch {
-        if (!canceled) setAllFiles([])
-      } finally {
-        if (!canceled) setFilesLoading(false)
-      }
-    }
-
-    void load()
-    return () => {
-      canceled = true
-    }
-  }, [activeTab, folderPath])
-
   // Filter files by query using pre-computed lowercase fields
   const filteredFiles = useMemo(() => {
     const trimmed = query.trim()
@@ -253,10 +130,9 @@ export function SearchCommandDialog({
       setAgentFilter(null)
       setResults([])
       setActiveTab("conversations")
-      filesLoadedRef.current = false
+      resetFileTree()
-      setAllFiles([])
     }
-  }, [open])
+  }, [open, resetFileTree])
 
   const handleSelectConversation = useCallback(
     (conv: DbConversationSummary) => {

src/components/layout/aux-panel-file-tree-tab.tsx

@@ -36,10 +36,7 @@ import {
   startFileTreeWatch,
   stopFileTreeWatch,
 } from "@/lib/api"
-import {
+import { emitAttachFileToSession } from "@/lib/session-attachment-events"
-  emitAttachFileToSession,
-  emitAppendTextToSession,
-} from "@/lib/session-attachment-events"
 import type {
   FileTreeChangedEvent,
   FileTreeNode,
@@ -86,16 +83,7 @@ import {
   CollapsibleTrigger,
 } from "@/components/ui/collapsible"
 import { Skeleton } from "@/components/ui/skeleton"
-
+import { joinFsPath } from "@/lib/path-utils"
-function joinFsPath(basePath: string, relPath: string): string {
-  if (!relPath) return basePath
-  const separator = basePath.includes("\\") ? "\\" : "/"
-  const normalizedRel = relPath.replace(/[\\/]/g, separator)
-  if (basePath.endsWith("/") || basePath.endsWith("\\")) {
-    return `${basePath}${normalizedRel}`
-  }
-  return `${basePath}${separator}${normalizedRel}`
-}
 
 function parentDir(filePath: string): string {
   const slashIndex = filePath.lastIndexOf("/")
@@ -618,12 +606,9 @@ function RenderNode({
 
   const handleAttachDirToSession = () => {
     if (!activeSessionTabId) return
-    const relativePath = node.path.endsWith("/")
+    emitAttachFileToSession({
-      ? `@${node.path} `
-      : `@${node.path}/ `
-    emitAppendTextToSession({
       tabId: activeSessionTabId,
-      text: relativePath,
+      path: absolutePath,
     })
   }
 

src/hooks/use-file-tree.ts

@@ -0,0 +1,166 @@
+"use client"
+
+import { useState, useEffect, useRef, useCallback } from "react"
+import ig from "ignore"
+import { getFileTree, readFilePreview } from "@/lib/api"
+import type { FileTreeNode } from "@/lib/types"
+
+export interface FlatFileEntry {
+  name: string
+  /** Relative path from folder root (same as FileTreeNode.path) */
+  relativePath: string
+  kind: "file" | "dir"
+  /** Pre-computed lowercase relativePath for filtering */
+  lowerPath: string
+  /** Pre-computed lowercase name for filtering */
+  lowerName: string
+}
+
+export function flattenTree(nodes: FileTreeNode[]): FlatFileEntry[] {
+  const entries: FlatFileEntry[] = []
+  function walk(node: FileTreeNode) {
+    entries.push({
+      name: node.name,
+      relativePath: node.path,
+      kind: node.kind,
+      lowerPath: node.path.toLowerCase(),
+      lowerName: node.name.toLowerCase(),
+    })
+    if (node.kind === "dir" && node.children) {
+      for (const child of node.children) {
+        walk(child)
+      }
+    }
+  }
+  for (const node of nodes) {
+    walk(node)
+  }
+  return entries
+}
+
+/** Check whether any ancestor directory of `path` is in `ignoredDirs`. */
+export function hasIgnoredAncestor(
+  path: string,
+  ignoredDirs: Set<string>
+): boolean {
+  let idx = path.indexOf("/")
+  while (idx !== -1) {
+    if (ignoredDirs.has(path.slice(0, idx))) return true
+    idx = path.indexOf("/", idx + 1)
+  }
+  return false
+}
+
+interface UseFileTreeOptions {
+  folderPath: string | undefined
+  enabled: boolean
+}
+
+interface UseFileTreeResult {
+  allFiles: FlatFileEntry[]
+  loading: boolean
+  loaded: boolean
+  /** Clear cached data so the next `enabled=true` triggers a fresh load. */
+  reset: () => void
+}
+
+export function useFileTree({
+  folderPath,
+  enabled,
+}: UseFileTreeOptions): UseFileTreeResult {
+  const [allFiles, setAllFiles] = useState<FlatFileEntry[]>([])
+  const [loading, setLoading] = useState(false)
+  const loadedForPathRef = useRef<string | null>(null)
+
+  useEffect(() => {
+    if (!enabled || !folderPath) return
+    if (loadedForPathRef.current === folderPath) return
+
+    let canceled = false
+    setLoading(true)
+
+    async function load() {
+      try {
+        const tree = await getFileTree(folderPath!, 10)
+        const flat = flattenTree(tree)
+
+        // Collect all .gitignore files from the tree
+        const gitignoreEntries = flat.filter(
+          (f) => f.kind === "file" && f.name === ".gitignore"
+        )
+
+        // Build matchers keyed by directory prefix
+        const matchers: {
+          prefix: string
+          matcher: ReturnType<typeof ig>
+        }[] = []
+        await Promise.all(
+          gitignoreEntries.map(async (entry) => {
+            try {
+              const result = await readFilePreview(
+                folderPath!,
+                entry.relativePath
+              )
+              const lastSlash = entry.relativePath.lastIndexOf("/")
+              const dir =
+                lastSlash === -1 ? "" : entry.relativePath.slice(0, lastSlash)
+              matchers.push({
+                prefix: dir ? dir + "/" : "",
+                matcher: ig().add(result.content),
+              })
+            } catch {
+              // skip unreadable .gitignore
+            }
+          })
+        )
+
+        // Sort matchers by prefix length (shortest/root first)
+        matchers.sort((a, b) => a.prefix.length - b.prefix.length)
+
+        // Filter: check each entry against all applicable .gitignore matchers
+        const ignoredDirs = new Set<string>()
+        const filtered = flat.filter((f) => {
+          if (f.name === ".gitignore") return false
+          if (hasIgnoredAncestor(f.relativePath, ignoredDirs)) return false
+          for (const { prefix, matcher } of matchers) {
+            if (!f.relativePath.startsWith(prefix)) continue
+            const relPath = f.relativePath.slice(prefix.length)
+            if (!relPath) continue
+            const testPath = f.kind === "dir" ? `${relPath}/` : relPath
+            if (matcher.ignores(testPath)) {
+              if (f.kind === "dir") ignoredDirs.add(f.relativePath)
+              return false
+            }
+          }
+          return true
+        })
+
+        if (!canceled) {
+          setAllFiles(filtered)
+          loadedForPathRef.current = folderPath!
+        }
+      } catch {
+        if (!canceled) setAllFiles([])
+      } finally {
+        if (!canceled) setLoading(false)
+      }
+    }
+
+    void load()
+    return () => {
+      canceled = true
+    }
+  }, [enabled, folderPath])
+
+  const reset = useCallback(() => {
+    loadedForPathRef.current = null
+    setAllFiles([])
+  }, [])
+
+  return {
+    allFiles,
+    loading,
+    loaded: loadedForPathRef.current === folderPath,
+    reset,
+  }
+}

src/lib/path-utils.ts

@@ -0,0 +1,9 @@
+export function joinFsPath(basePath: string, relPath: string): string {
+  if (!relPath) return basePath
+  const separator = basePath.includes("\\") ? "\\" : "/"
+  const normalizedRel = relPath.replace(/[\\/]/g, separator)
+  if (basePath.endsWith("/") || basePath.endsWith("\\")) {
+    return `${basePath}${normalizedRel}`
+  }
+  return `${basePath}${separator}${normalizedRel}`
+}