fix(editor): keep file basename in @-reference links

The explorer @ button appended plain text (@folder/file.ts), which DSH's
composer only decorates as a folder ref (@folder/) — the file name stayed
outside the link. Insert FILE references through DSH's own structured
insert-reference event instead, minting one chip for the whole reference
(displayed as @basename, serialized as the full @path). Directories keep the
plain @dir/ mention so folder completion still works.

src/client/EditorHost.tsx

@@ -100,7 +100,7 @@ export function EditorHost(props: {
   expanded: string[]
   revealed: string[]
   onToggleDir: (path: string) => void
-  onReferenceFile: (path: string) => void
+  onReferenceFile: (path: string, isDir: boolean) => void
 }) {
   const { ctx, store, scope, tab, expanded, revealed, onToggleDir, onReferenceFile } = props
   const path = tab.path ?? ''

src/client/FileTree.tsx

@@ -131,8 +131,8 @@ export function FileTree(props: {
   onOpenWith?: (targetId: string, path: string) => void
   /** Toggle one target's pinned state (the submenu row's pushpin). */
   onToggleOpenWithPin?: (targetId: string) => void
-  /** Insert `@<relative path>` into the composer draft. */
-  onReferenceFile: (path: string) => void
+  /** Insert `@<relative path>` into the composer draft (file vs directory). */
+  onReferenceFile: (path: string, isDir: boolean) => void
   /** Bump to wipe the level cache and reload the visible set. */
   refreshTick: number
   /** Upload into `dir` (absolute, inside the workspace); runs in the caller. */
@@ -332,7 +332,7 @@ export function FileTree(props: {
         title={t('referenceFile')}
         onClick={(event) => {
           event.stopPropagation()
-          onReferenceFile(entry.path)
+          onReferenceFile(entry.path, entry.isDir)
         }}
       >
         {t('referenceFile')}
@@ -570,7 +570,7 @@ export function FileTree(props: {
                   title={t('referenceFile')}
                   onClick={(event) => {
                     event.stopPropagation()
-                    onReferenceFile(root)
+                    onReferenceFile(root, true)
                   }}
                 >
                   {t('referenceFile')}

src/client/Sidebar.tsx

@@ -33,7 +33,7 @@ import { useSyncExternalStore } from 'react'
 import clsx from 'clsx'
 import { IconCloseFill14, Tooltip } from '@deepseek-ai/dsh-client-ui-primitives'
 import type { Context, SidebarSessionList } from '../context-types.ts'
-import { appendToDraft } from './conversation-draft.ts'
+import { appendToDraft, insertFileReference } from './conversation-draft.ts'
 import {
   BOTTOM_MIN, PANEL_MIN, activateTab, agentUuidOf, allLeaves, closeFloatByTab, closeTab, dockFloat, firstLeaf, floatTab,
   floatWithTab, isAgentTabId, leafWithTab, migrateBottomTabs,
@@ -128,7 +128,7 @@ function injectUserCss(attr: string, id: string, cssText: string): HTMLStyleElem
  *  pane; sessionId/cwd cover onReferenceFile). */
 interface TabContentProps extends TabContentMemoKey {
   onToggleDir: (path: string) => void
-  onReferenceFile: (path: string) => void
+  onReferenceFile: (path: string, isDir: boolean) => void
   ctx: Context
   store: SidebarStore
   /** Fired before a topology node jumps to its child session (see Sidebar). */
@@ -1376,17 +1376,26 @@ export function Sidebar(props: { ctx: Context; store: SidebarStore }) {
   }, [actions, pinnedVirtualTabs, activePinnedTabId, store])
 
   /**
-   * The explorer's @-reference button: append `@<relative path>` to the
-   * session's composer draft (space-separated). The conversation service is
-   * resolved lazily through `ctx.get` (the inject-free read — the app's own
-   * plugins read 'conversation' the same way); a missing service or scope
-   * degrades to a logged no-op, never a crash. Defined above the no-session
-   * early return — a hook must never sit behind a conditional return
-   * (React counts hooks per render).
+   * The explorer's @-reference button. Directories append the folder mention
+   * (`@dir/`) as plain text so DSH's folder decoration and completion keep
+   * working; files insert a structured chip like the native `@` picker, so
+   * the whole reference stays one link instead of decorating only the
+   * leading folder. Resolves the session-scope ctx and the conversation
+   * input service at click time; a missing service or scope degrades to a
+   * logged no-op, never a crash. Defined above the no-session early return
+   * — a hook must never sit behind a conditional return (React counts hooks
+   * per render).
    */
-  const referenceInChat = useCallback((path: string): void => {
+  const referenceInChat = useCallback((path: string, isDir: boolean): void => {
     if (sessionId === undefined) return
-    appendToDraft(ctx, sessionId, `@${relativeTo(cwd ?? '', path)}`)
+    const rel = relativeTo(cwd ?? '', path)
+    if (isDir) {
+      appendToDraft(ctx, sessionId, `@${rel === '.' ? './' : `${rel}/`}`)
+      return
+    }
+    if (!insertFileReference(ctx, sessionId, rel)) {
+      appendToDraft(ctx, sessionId, `@${rel}`)
+    }
   }, [ctx, sessionId, cwd])
 
   if (state === undefined || sessionId === undefined) {

src/client/TreePanel.tsx

@@ -62,7 +62,7 @@ export function TreePanel(props: {
   openWithSsh?: boolean
   onOpenWith?: (targetId: string, path: string) => void
   onToggleOpenWithPin?: (targetId: string) => void
-  onReferenceFile: (path: string) => void
+  onReferenceFile: (path: string, isDir: boolean) => void
   /** Full-window presentation: the panel fills its host instead of docking
    *  at a fixed width. */
   full?: boolean

src/client/conversation-draft.ts

@@ -5,6 +5,14 @@
  * through `ctx.get` (the inject-free read the app's own plugins use); a
  * missing service or scope degrades to a logged no-op, never a crash.
  *
+ * File references additionally use DSH's own structured insert event
+ * (`slash/input-insert-reference`, see `insertFileReference`) instead of
+ * plain draft text: the native `@file` picker emits this event, and the
+ * conversation input machine mints one occurrence whose chip covers the
+ * whole reference. Plain text `@folder/file.ts` only ever gets DSH's
+ * folder-ref decoration (`@folder/`) — the file name stays undecorated — so
+ * plain append is the fallback, not the primary path, for files.
+ *
  * Insert position (fixes upstream issue #425): the draft store only exposes
  * the whole string (`getSnapshot().draft` + `setDraft(text)`) — there is no
  * caret API on the conversation service. The composer's `<textarea>` keeps
@@ -185,3 +193,63 @@ export function appendToDraft(ctx: Context, sessionId: string, text: string): bo
     return false
   }
 }
+
+/**
+ * The DSH `@file` spelling for one relative path, mirroring the host grammar
+ * (`formatFileMention` in `@deepseek-ai/dsh-file-reference`): plain when
+ * there is no whitespace, quoted when there is, and `undefined` when the
+ * path contains a control character or an embedded quote the editor grammar
+ * cannot represent.
+ */
+export function fileMention(relativePath: string): { mention: string; label: string } | undefined {
+  const path = relativePath.replace(/[\\/]+$/, '')
+  if (/[\u0000-\u001f\u007f-\u009f"]/u.test(path)) return undefined
+  const mention = /\s/u.test(path) ? `@"${path}"` : `@${path}`
+  const at = Math.max(path.lastIndexOf('/'), path.lastIndexOf('\\'))
+  const label = at === -1 ? path : path.slice(at + 1)
+  return { mention, label }
+}
+
+/**
+ * Insert one FILE reference as a structured chip (like DSH's own `@` picker).
+ * The chip displays `@<basename>` but serializes to `@<relative path>` on
+ * send, so the reference stays a single link from trigger to basename.
+ *
+ * Directories are NOT handled here: DSH's folder grammar wants the trailing
+ * slash as plain text (`@dir/`) so completion can descend, which
+ * `appendToDraft` already covers.
+ */
+export function insertFileReference(ctx: Context, sessionId: string, relativePath: string): boolean {
+  const reference = fileMention(relativePath)
+  if (reference === undefined) return false
+  try {
+    const actx = ctx.sessions.scope(sessionId)
+    if (actx === undefined) return false
+    const conversation = ctx.get('conversation') as SidebarConversation | undefined
+    if (conversation === undefined) return false
+    const input = conversation.input.for(actx)
+    const before = input.state.getSnapshot()
+    if (before.draftRev === undefined) return false
+    // The session-scope Context's typed `emit` is keyed to DSH's closed event
+    // map; this internal composer event is deliberately string-loose at runtime.
+    ;(actx as unknown as { emit(name: string, payload: unknown): void }).emit('slash/input-insert-reference', {
+      reference: {
+        source: 'reference',
+        ref: reference.mention,
+        label: reference.label,
+        appearance: 'file',
+        clipboardText: reference.mention,
+      },
+      span: {
+        draftRev: before.draftRev,
+        start: before.draft.length,
+        end: before.draft.length,
+      },
+    })
+    const after = input.state.getSnapshot()
+    return after.draftRev !== before.draftRev
+  } catch (error) {
+    console.warn('[dsh-better-sidebar] file-reference insert failed:', error)
+    return false
+  }
+}

src/client/service.ts

@@ -151,7 +151,7 @@ export interface TabComponentProps {
   /** The explorer's reveal-highlight set (ExplorerView; "Show in folder" targets). */
   revealed?: string[]
   onToggleDir?: (path: string) => void
-  onReferenceFile?: (path: string) => void
+  onReferenceFile?: (path: string, isDir: boolean) => void
   onOpenFile?: (path: string) => void
   onOpenDiff?: (tab: SidebarTab) => void
   onSubagentJump?: (childSessionId: string) => void

src/context-types.ts

@@ -391,9 +391,10 @@ export interface SidebarLocaleService {
 
 /** The composer draft face the sidebar reaches through `ctx.conversation.input`. */
 export interface SidebarSessionInput {
-  /** The live input store (draft read for append). */
+  /** The live input store (draft read for append). `draftRev` is the machine's
+   *  span-CAS revision — required to mint a structured file-reference chip. */
   state: {
-    getSnapshot(): { draft: string }
+    getSnapshot(): { draft: string; draftRev?: number }
   }
   /** Replace the draft text (the input machine's single public write path). */
   setDraft(text: string): void

tests/reference-mention.spec.ts

@@ -0,0 +1,30 @@
+import { describe, expect, it } from 'vitest'
+import { fileMention } from '../src/client/conversation-draft.ts'
+
+describe('fileMention', () => {
+  it('formats a plain relative file path as an @file mention', () => {
+    expect(fileMention('src/client/paths.ts')).toEqual({
+      mention: '@src/client/paths.ts',
+      label: 'paths.ts',
+    })
+  })
+
+  it('quotes a path containing whitespace and keeps the full basename', () => {
+    expect(fileMention('docs/plan files/design notes.md')).toEqual({
+      mention: '@"docs/plan files/design notes.md"',
+      label: 'design notes.md',
+    })
+  })
+
+  it('trims a trailing separator before deriving the basename', () => {
+    expect(fileMention('src/client/')).toEqual({
+      mention: '@src/client',
+      label: 'client',
+    })
+  })
+
+  it('rejects embedded quotes and control characters', () => {
+    expect(fileMention('src/a"b.ts')).toBeUndefined()
+    expect(fileMention('src/a\u0000b.ts')).toBeUndefined()
+  })
+})