fix: keep desktop attachments path-only

Desktop file attachment selection was inlining every selected file as a data URL before sending the websocket message. Large multi-file sends could inflate the renderer request body by tens of megabytes before the server had a chance to materialize uploads.

Route Tauri file selection through the native dialog so desktop sends absolute paths, while preserving browser fallback data URLs for H5. Cover both active-session and draft-session composers plus a payload-size regression case.

Constraint: Browser/H5 cannot rely on local absolute file paths, so the existing FileReader fallback remains for non-Tauri runtimes.
Rejected: Raise websocket/body limits | would keep renderer memory pressure and still send file bytes unnecessarily.
Confidence: high
Scope-risk: narrow
Directive: Do not reintroduce FileReader data URLs for Tauri desktop file-picker attachments without measuring websocket payload size.
Tested: cd desktop && bun run test src/lib/composerAttachments.test.ts src/components/chat/ChatInput.test.tsx src/pages/EmptySession.test.tsx
Tested: /tmp complex-project reproduction showed 12x3MB old inline payload at 50,333,174 bytes versus path-only payload around 1-2KB
Not-tested: Full desktop lint/build due unrelated existing Sidebar.tsx type errors in the dirty worktree
Related: https://github.com/NanmiCoder/cc-haha/issues/444

desktop/src/components/chat/ChatInput.test.tsx

@@ -19,6 +19,7 @@ const mocks = vi.hoisted(() => ({
   search: vi.fn(),
   browse: vi.fn(),
   wsSend: vi.fn(),
+  dialogOpen: vi.fn(),
 }))
 
 vi.mock('../../api/sessions', () => ({
@@ -51,6 +52,10 @@ vi.mock('../../api/websocket', () => ({
   },
 }))
 
+vi.mock('@tauri-apps/plugin-dialog', () => ({
+  open: mocks.dialogOpen,
+}))
+
 vi.mock('../../hooks/useMobileViewport', () => ({
   useMobileViewport: () => viewportMocks.isMobile,
 }))
@@ -113,6 +118,7 @@ describe('ChatInput file mentions', () => {
 
   beforeEach(() => {
     vi.clearAllMocks()
+    delete (window as Window & { __TAURI_INTERNALS__?: unknown }).__TAURI_INTERNALS__
     viewportMocks.isMobile = false
     useSettingsStore.setState({ locale: 'en' })
     useChatStore.setState(initialChatState, true)
@@ -612,6 +618,53 @@ describe('ChatInput file mentions', () => {
     })
   })
 
+  it('uses native desktop file paths instead of inlining selected files', async () => {
+    Object.defineProperty(window, '__TAURI_INTERNALS__', {
+      configurable: true,
+      value: {},
+    })
+    mocks.dialogOpen.mockResolvedValueOnce([
+      '/Users/nanmi/tmp/large-a.log',
+      'C:\\Users\\Nanmi\\Desktop\\large-b.zip',
+    ])
+
+    render(<ChatInput compact />)
+
+    fireEvent.click(screen.getByLabelText('Open composer tools'))
+    fireEvent.click(screen.getByText('Add files or photos'))
+
+    expect(await screen.findByText('large-a.log')).toBeInTheDocument()
+    expect(await screen.findByText('large-b.zip')).toBeInTheDocument()
+
+    const input = screen.getByRole('textbox') as HTMLTextAreaElement
+    fireEvent.change(input, {
+      target: {
+        value: 'analyze these',
+        selectionStart: 'analyze these'.length,
+      },
+    })
+    fireEvent.keyDown(input, { key: 'Enter' })
+
+    expect(mocks.wsSend).toHaveBeenCalledWith(sessionId, {
+      type: 'user_message',
+      content: 'analyze these',
+      attachments: [
+        expect.objectContaining({
+          type: 'file',
+          name: 'large-a.log',
+          path: '/Users/nanmi/tmp/large-a.log',
+          data: undefined,
+        }),
+        expect.objectContaining({
+          type: 'file',
+          name: 'large-b.zip',
+          path: 'C:\\Users\\Nanmi\\Desktop\\large-b.zip',
+          data: undefined,
+        }),
+      ],
+    })
+  })
+
   it('uses larger icon-only mobile action buttons for browser H5 access', async () => {
     viewportMocks.isMobile = true
     mocks.search.mockResolvedValueOnce({

desktop/src/components/chat/ChatInput.tsx

@@ -31,23 +31,15 @@ import {
 } from './composerUtils'
 import { useMobileViewport } from '../../hooks/useMobileViewport'
 import { isTauriRuntime } from '../../lib/desktopRuntime'
+import {
+  filesToComposerAttachments,
+  selectNativeFileAttachments,
+  type ComposerAttachment,
+} from '../../lib/composerAttachments'
 
 type GitInfo = SessionGitInfo
 
-type Attachment = {
-  id: string
-  name: string
-  type: 'image' | 'file'
-  path?: string
-  mimeType?: string
-  previewUrl?: string
-  data?: string
-  isDirectory?: boolean
-  lineStart?: number
-  lineEnd?: number
-  note?: string
-  quote?: string
-}
+type Attachment = ComposerAttachment
 
 type ComposerDraft = {
   input: string
@@ -710,31 +702,43 @@ export function ChatInput({ variant = 'default', compact = false }: ChatInputPro
     if (!hasImage) return
   }
 
+  const appendFiles = useCallback((files: FileList | File[]) => {
+    void filesToComposerAttachments(files)
+      .then((nextAttachments) => {
+        if (nextAttachments.length === 0) return
+        setComposerAttachments((prev) => [...prev, ...nextAttachments])
+      })
+      .catch((error) => {
+        console.warn('[attachments] Failed to read selected files', error)
+      })
+  }, [setComposerAttachments])
+
+  const openAttachmentPicker = useCallback(() => {
+    if (!isTauriRuntime()) {
+      fileInputRef.current?.click()
+      setPlusMenuOpen(false)
+      return
+    }
+
+    void selectNativeFileAttachments()
+      .then((nativeAttachments) => {
+        if (nativeAttachments) {
+          if (nativeAttachments.length > 0) {
+            setComposerAttachments((prev) => [...prev, ...nativeAttachments])
+          }
+          return
+        }
+        fileInputRef.current?.click()
+      })
+      .finally(() => setPlusMenuOpen(false))
+  }, [setComposerAttachments])
+
   const handleFileSelect = (event: React.ChangeEvent<HTMLInputElement>) => {
     if (isMemberSession) return
     const files = event.target.files
     if (!files) return
 
-    Array.from(files).forEach((file) => {
-      const id = `att-${Date.now()}-${Math.random().toString(36).slice(2)}`
-      const isImage = file.type.startsWith('image/')
-      const reader = new FileReader()
-      reader.onload = () => {
-        setComposerAttachments((prev) => [
-          ...prev,
-          {
-            id,
-            name: file.name,
-            type: isImage ? 'image' : 'file',
-            mimeType: file.type || undefined,
-            previewUrl: isImage ? (reader.result as string) : undefined,
-            data: reader.result as string,
-          },
-        ])
-      }
-      reader.readAsDataURL(file)
-    })
-
+    appendFiles(files)
     event.target.value = ''
   }
 
@@ -743,8 +747,7 @@ export function ChatInput({ variant = 'default', compact = false }: ChatInputPro
     if (isMemberSession) return
     const files = event.dataTransfer.files
     if (files.length > 0) {
-      const fakeEvent = { target: { files } } as React.ChangeEvent<HTMLInputElement>
-      handleFileSelect(fakeEvent)
+      appendFiles(files)
     }
   }
 
@@ -983,10 +986,7 @@ export function ChatInput({ variant = 'default', compact = false }: ChatInputPro
                     {plusMenuOpen && (
                       <div className={`absolute bottom-full left-0 z-50 mb-2 rounded-xl border border-[var(--color-border)] bg-[var(--color-surface-container-lowest)] py-1 shadow-[var(--shadow-dropdown)] ${isMobileComposer ? 'w-[min(240px,calc(100vw-32px))]' : 'w-[240px]'}`}>
                         <button
-                          onClick={() => {
-                            fileInputRef.current?.click()
-                            setPlusMenuOpen(false)
-                          }}
+                          onClick={openAttachmentPicker}
                           className="flex w-full items-center gap-3 px-4 py-2.5 text-left transition-colors hover:bg-[var(--color-surface-hover)]"
                         >
                           <span className="material-symbols-outlined text-[18px] text-[var(--color-text-secondary)]">attach_file</span>

desktop/src/lib/composerAttachments.test.ts

@@ -0,0 +1,34 @@
+import { describe, expect, it } from 'vitest'
+import { pathToComposerAttachment } from './composerAttachments'
+
+describe('composer attachment payloads', () => {
+  it('keeps many selected desktop project files as paths instead of request-body data', () => {
+    const projectRoot = '/tmp/cc-haha-issue-444-regression'
+    const files = Array.from({ length: 12 }, (_, index) => (
+      `${projectRoot}/assets/large-${index + 1}.bin`
+    ))
+
+    const oldInlineAttachments = files.map((filePath) => ({
+      type: 'file',
+      name: filePath.split('/').pop(),
+      data: `data:application/octet-stream;base64,${'A'.repeat(256 * 1024)}`,
+      mimeType: 'application/octet-stream',
+    }))
+    const oldInlinePayload = JSON.stringify({
+      type: 'user_message',
+      content: 'analyze these files',
+      attachments: oldInlineAttachments,
+    })
+
+    const pathOnlyAttachments = files.map(pathToComposerAttachment)
+    const pathOnlyPayload = JSON.stringify({
+      type: 'user_message',
+      content: 'analyze these files',
+      attachments: pathOnlyAttachments,
+    })
+
+    expect(oldInlinePayload.length).toBeGreaterThan(3 * 1024 * 1024)
+    expect(pathOnlyPayload.length).toBeLessThan(3 * 1024)
+    expect(pathOnlyAttachments.every((attachment) => attachment.path && !attachment.data)).toBe(true)
+  })
+})

desktop/src/lib/composerAttachments.ts

@@ -0,0 +1,95 @@
+import { isTauriRuntime } from './desktopRuntime'
+
+export type ComposerAttachment = {
+  id: string
+  name: string
+  type: 'image' | 'file'
+  path?: string
+  mimeType?: string
+  previewUrl?: string
+  data?: string
+  isDirectory?: boolean
+  lineStart?: number
+  lineEnd?: number
+  note?: string
+  quote?: string
+}
+
+function nextAttachmentId() {
+  return `att-${Date.now()}-${Math.random().toString(36).slice(2)}`
+}
+
+export function getFileNameFromPath(filePath: string): string {
+  const normalized = filePath.replace(/[\\/]+$/g, '')
+  return normalized.split(/[\\/]/).filter(Boolean).pop() || filePath
+}
+
+export function pathToComposerAttachment(filePath: string): ComposerAttachment {
+  return {
+    id: nextAttachmentId(),
+    name: getFileNameFromPath(filePath),
+    type: 'file',
+    path: filePath,
+  }
+}
+
+export async function selectNativeFileAttachments(): Promise<ComposerAttachment[] | null> {
+  if (!isTauriRuntime()) return null
+
+  try {
+    const { open } = await import('@tauri-apps/plugin-dialog')
+    const selected = await open({
+      multiple: true,
+      directory: false,
+    })
+    const paths = normalizeDialogSelection(selected)
+    return paths.map(pathToComposerAttachment)
+  } catch (error) {
+    console.warn('[attachments] Native file picker failed; falling back to browser file input', error)
+    return null
+  }
+}
+
+export async function filesToComposerAttachments(files: FileList | File[]): Promise<ComposerAttachment[]> {
+  const entries = Array.from(files)
+  const attachments = await Promise.all(entries.map(fileToComposerAttachment))
+  return attachments.filter((attachment): attachment is ComposerAttachment => !!attachment)
+}
+
+function normalizeDialogSelection(selected: string | string[] | null): string[] {
+  if (!selected) return []
+  const paths = Array.isArray(selected) ? selected : [selected]
+  return paths.filter((filePath) => typeof filePath === 'string' && filePath.length > 0)
+}
+
+function getNativeFilePath(file: File): string | undefined {
+  const path = (file as File & { path?: unknown }).path
+  return typeof path === 'string' && path.length > 0 ? path : undefined
+}
+
+async function fileToComposerAttachment(file: File): Promise<ComposerAttachment | null> {
+  const nativePath = isTauriRuntime() ? getNativeFilePath(file) : undefined
+  if (nativePath) {
+    return pathToComposerAttachment(nativePath)
+  }
+
+  const isImage = file.type.startsWith('image/')
+  const data = await readFileAsDataUrl(file)
+  return {
+    id: nextAttachmentId(),
+    name: file.name,
+    type: isImage ? 'image' : 'file',
+    mimeType: file.type || undefined,
+    previewUrl: isImage ? data : undefined,
+    data,
+  }
+}
+
+function readFileAsDataUrl(file: File): Promise<string> {
+  return new Promise((resolve, reject) => {
+    const reader = new FileReader()
+    reader.onload = () => resolve(reader.result as string)
+    reader.onerror = () => reject(reader.error ?? new Error(`Failed to read ${file.name}`))
+    reader.readAsDataURL(file)
+  })
+}

desktop/src/pages/EmptySession.test.tsx

@@ -16,6 +16,7 @@ const mocks = vi.hoisted(() => ({
   wsOnMessage: vi.fn(),
   wsSend: vi.fn(),
   wsDisconnect: vi.fn(),
+  dialogOpen: vi.fn(),
   isMobile: false,
   isTauriRuntime: false,
 }))
@@ -61,6 +62,10 @@ vi.mock('../lib/desktopRuntime', () => ({
   isTauriRuntime: () => mocks.isTauriRuntime,
 }))
 
+vi.mock('@tauri-apps/plugin-dialog', () => ({
+  open: mocks.dialogOpen,
+}))
+
 vi.mock('../components/shared/DirectoryPicker', () => ({
   DirectoryPicker: ({ value, onChange }: { value: string; onChange: (path: string) => void }) => (
     <button type="button" aria-label="Pick project" data-value={value} onClick={() => onChange('/workspace/project')}>
@@ -301,6 +306,49 @@ describe('EmptySession', () => {
     ])
   })
 
+  it('uses native desktop file paths for draft attachments', async () => {
+    mocks.isTauriRuntime = true
+    mocks.dialogOpen.mockResolvedValueOnce([
+      'C:\\Users\\Nanmi\\Desktop\\huge-a.log',
+      '/Users/nanmi/tmp/huge-b.zip',
+    ])
+
+    render(<EmptySession />)
+
+    fireEvent.click(screen.getByLabelText('Open composer tools'))
+    fireEvent.click(screen.getByText('Add files or photos'))
+
+    expect(await screen.findByText('huge-a.log')).toBeInTheDocument()
+    expect(await screen.findByText('huge-b.zip')).toBeInTheDocument()
+
+    fireEvent.change(screen.getByRole('textbox'), {
+      target: { value: 'check these files', selectionStart: 'check these files'.length },
+    })
+    fireEvent.click(screen.getByRole('button', { name: /Run/i }))
+
+    await waitFor(() => {
+      expect(mocks.createSession).toHaveBeenCalledWith({})
+    })
+    expect(mocks.wsSend).toHaveBeenCalledWith('draft-session', {
+      type: 'user_message',
+      content: 'check these files',
+      attachments: [
+        expect.objectContaining({
+          type: 'file',
+          name: 'huge-a.log',
+          path: 'C:\\Users\\Nanmi\\Desktop\\huge-a.log',
+          data: undefined,
+        }),
+        expect.objectContaining({
+          type: 'file',
+          name: 'huge-b.zip',
+          path: '/Users/nanmi/tmp/huge-b.zip',
+          data: undefined,
+        }),
+      ],
+    })
+  })
+
   it('starts in a selected non-Git project without showing a repository warning', async () => {
     mocks.getRepositoryContext.mockResolvedValueOnce(notGitRepositoryContext())
 

desktop/src/pages/EmptySession.tsx

@@ -1,4 +1,4 @@
-import { useEffect, useMemo, useRef, useState } from 'react'
+import { useCallback, useEffect, useMemo, useRef, useState } from 'react'
 import { ApiError } from '../api/client'
 import { skillsApi } from '../api/skills'
 import { useTranslation } from '../i18n'
@@ -17,6 +17,11 @@ import { FileSearchMenu, type FileSearchMenuHandle } from '../components/chat/Fi
 import { LocalSlashCommandPanel, type LocalSlashCommandName } from '../components/chat/LocalSlashCommandPanel'
 import { useMobileViewport } from '../hooks/useMobileViewport'
 import { isTauriRuntime } from '../lib/desktopRuntime'
+import {
+  filesToComposerAttachments,
+  selectNativeFileAttachments,
+  type ComposerAttachment,
+} from '../lib/composerAttachments'
 import {
   FALLBACK_SLASH_COMMANDS,
   findSlashToken,
@@ -28,15 +33,7 @@ import {
 import type { AttachmentRef } from '../types/chat'
 import type { SlashCommandOption } from '../components/chat/composerUtils'
 
-type Attachment = {
-  id: string
-  name: string
-  type: 'image' | 'file'
-  path?: string
-  mimeType?: string
-  previewUrl?: string
-  data?: string
-}
+type Attachment = ComposerAttachment
 
 type Translate = ReturnType<typeof useTranslation>
 
@@ -441,30 +438,42 @@ export function EmptySession() {
     if (!hasImage) return
   }
 
+  const appendFiles = useCallback((files: FileList | File[]) => {
+    void filesToComposerAttachments(files)
+      .then((nextAttachments) => {
+        if (nextAttachments.length === 0) return
+        setAttachments((prev) => [...prev, ...nextAttachments])
+      })
+      .catch((error) => {
+        console.warn('[attachments] Failed to read selected files', error)
+      })
+  }, [])
+
+  const openAttachmentPicker = useCallback(() => {
+    if (!isTauriRuntime()) {
+      fileInputRef.current?.click()
+      setPlusMenuOpen(false)
+      return
+    }
+
+    void selectNativeFileAttachments()
+      .then((nativeAttachments) => {
+        if (nativeAttachments) {
+          if (nativeAttachments.length > 0) {
+            setAttachments((prev) => [...prev, ...nativeAttachments])
+          }
+          return
+        }
+        fileInputRef.current?.click()
+      })
+      .finally(() => setPlusMenuOpen(false))
+  }, [])
+
   const handleFileSelect = (event: React.ChangeEvent<HTMLInputElement>) => {
     const files = event.target.files
     if (!files) return
 
-    Array.from(files).forEach((file) => {
-      const id = `att-${Date.now()}-${Math.random().toString(36).slice(2)}`
-      const isImage = file.type.startsWith('image/')
-      const reader = new FileReader()
-      reader.onload = () => {
-        setAttachments((prev) => [
-          ...prev,
-          {
-            id,
-            name: file.name,
-            type: isImage ? 'image' : 'file',
-            mimeType: file.type || undefined,
-            previewUrl: isImage ? (reader.result as string) : undefined,
-            data: reader.result as string,
-          },
-        ])
-      }
-      reader.readAsDataURL(file)
-    })
-
+    appendFiles(files)
     event.target.value = ''
   }
 
@@ -472,8 +481,7 @@ export function EmptySession() {
     event.preventDefault()
     const files = event.dataTransfer.files
     if (files.length > 0) {
-      const fakeEvent = { target: { files } } as React.ChangeEvent<HTMLInputElement>
-      handleFileSelect(fakeEvent)
+      appendFiles(files)
     }
   }
 
@@ -683,10 +691,7 @@ export function EmptySession() {
                         isMobileComposer ? 'w-[min(240px,calc(100vw-32px))]' : 'w-[240px]'
                       }`}>
                         <button
-                          onClick={() => {
-                            fileInputRef.current?.click()
-                            setPlusMenuOpen(false)
-                          }}
+                          onClick={openAttachmentPicker}
                           className="flex w-full items-center gap-3 px-4 py-2.5 text-left text-sm text-[var(--color-text-primary)] transition-colors hover:bg-[var(--color-surface-hover)]"
                         >
                           <span className="material-symbols-outlined text-[18px] text-[var(--color-text-secondary)]">attach_file</span>