refactor(desktop): extract file-preview/clipboard/image IPC from main.cjs into media-ipc.cjs

Tenth main.cjs cluster peel. Seven handlers — readFileDataUrl, readFileText,
selectPaths, writeClipboard, saveImageFromUrl, saveImageBuffer, saveClipboardImage
— move verbatim into electron/media-ipc.cjs behind a registerMediaIpc({...})
registrar. The file-hardening + WSL-clipboard sibling modules are required
directly; the preview helpers (mimeTypeForPath/looksBinary/PREVIEW_LANGUAGE_BY_EXT/
TEXT_PREVIEW_MAX_BYTES) and image writers (saveImageFromUrl/writeComposerImage)
are injected. selectPaths parents its native dialog on an injected getMainWindow()
so it tracks the live window instead of a captured reference.

Channel names unchanged → preload + renderer untouched. Dead hardening/wsl
requires in main.cjs removed. Adds electron/media-ipc.test.cjs (surface +
saveImageFromUrl/saveImageBuffer delegation; clipboard/dialog/fs paths in-app only).

apps/desktop/electron/main.cjs

@@ -43,7 +43,6 @@ const { dashboardFallbackArgs, sourceDeclaresServe } = require('./backend-comman
 const { serializeJsonBody, setJsonRequestHeaders } = require('./oauth-net-request.cjs')
 const { buildDesktopBackendEnv, normalizeHermesHomeRoot } = require('./backend-env.cjs')
 const { readWindowsUserEnvVar } = require('./windows-user-env.cjs')
-const { readWslWindowsClipboardImage } = require('./wsl-clipboard-image.cjs')
 const { nativeOverlayWidth: computeNativeOverlayWidth } = require('./titlebar-overlay-width.cjs')
 const { readLiveUpdateMarker } = require('./update-marker.cjs')
 const {
@@ -64,6 +63,7 @@ const { registerProjectDirIpc } = require('./project-dir-ipc.cjs')
 const { registerVscodeThemeIpc } = require('./vscode-theme-ipc.cjs')
 const { registerUninstallIpc } = require('./uninstall-ipc.cjs')
 const { registerVersionIpc } = require('./version-ipc.cjs')
+const { registerMediaIpc } = require('./media-ipc.cjs')
 const { OFFICIAL_REPO_HTTPS_URL, isOfficialSshRemote } = require('./update-remote.cjs')
 const { resolveBehindCount, shouldCountCommits } = require('./update-count.cjs')
 const { runRebuildWithRetry } = require('./update-rebuild.cjs')
@@ -100,9 +100,7 @@ const {
   tokenPreview
 } = require('./connection-config.cjs')
 const {
-  DATA_URL_READ_MAX_BYTES,
   DEFAULT_FETCH_TIMEOUT_MS,
-  TEXT_PREVIEW_SOURCE_MAX_BYTES,
   encryptDesktopSecret: encryptDesktopSecretStrict,
   resolveReadableFileForIpc,
   resolveRequestedPathForIpc,
@@ -6507,98 +6505,18 @@ ipcMain.handle('hermes:notify', (_event, payload) => {
   return true
 })
 
-ipcMain.handle('hermes:readFileDataUrl', async (_event, filePath) => {
-  const { resolvedPath } = await resolveReadableFileForIpc(filePath, {
-    maxBytes: DATA_URL_READ_MAX_BYTES,
-    purpose: 'File preview'
-  })
-  const data = await fs.promises.readFile(resolvedPath)
-  return `data:${mimeTypeForPath(resolvedPath)};base64,${data.toString('base64')}`
-})
-
-ipcMain.handle('hermes:readFileText', async (_event, filePath) => {
-  const { resolvedPath, stat } = await resolveReadableFileForIpc(filePath, {
-    maxBytes: TEXT_PREVIEW_SOURCE_MAX_BYTES,
-    purpose: 'Text preview'
-  })
-  const ext = path.extname(resolvedPath).toLowerCase()
-  const handle = await fs.promises.open(resolvedPath, 'r')
-  const bytesToRead = Math.min(stat.size, TEXT_PREVIEW_MAX_BYTES)
-
-  try {
-    const buffer = Buffer.alloc(bytesToRead)
-    const { bytesRead } = await handle.read(buffer, 0, bytesToRead, 0)
-
-    return {
-      binary: looksBinary(buffer.subarray(0, Math.min(bytesRead, 4096))),
-      byteSize: stat.size,
-      language: PREVIEW_LANGUAGE_BY_EXT[ext] || 'text',
-      mimeType: mimeTypeForPath(resolvedPath),
-      path: resolvedPath,
-      text: buffer.subarray(0, bytesRead).toString('utf8'),
-      truncated: stat.size > TEXT_PREVIEW_MAX_BYTES
-    }
-  } finally {
-    await handle.close()
-  }
-})
-
-ipcMain.handle('hermes:selectPaths', async (_event, options = {}) => {
-  const properties = options?.directories ? ['openDirectory'] : ['openFile']
-  if (options?.multiple !== false) properties.push('multiSelections')
-
-  let resolvedDefaultPath
-  if (options?.defaultPath) {
-    try {
-      resolvedDefaultPath = path.resolve(String(options.defaultPath))
-    } catch {
-      resolvedDefaultPath = undefined
-    }
-  }
-
-  const result = await dialog.showOpenDialog(mainWindow, {
-    title: options?.title || 'Add context',
-    defaultPath: resolvedDefaultPath,
-    properties,
-    filters: Array.isArray(options?.filters) ? options.filters : undefined
-  })
-
-  if (result.canceled) return []
-  return result.filePaths
-})
-
-ipcMain.handle('hermes:writeClipboard', (_event, text) => {
-  clipboard.writeText(String(text || ''))
-  return true
-})
-
-ipcMain.handle('hermes:saveImageFromUrl', (_event, url) => saveImageFromUrl(String(url || '')))
-
-ipcMain.handle('hermes:saveImageBuffer', async (_event, payload) => {
-  const data = payload?.data
-  if (!data) throw new Error('saveImageBuffer: missing data')
-
-  const buffer = Buffer.isBuffer(data) ? data : Buffer.from(data)
-  return writeComposerImage(buffer, payload?.ext || '.png')
-})
-
-ipcMain.handle('hermes:saveClipboardImage', async () => {
-  const image = clipboard.readImage()
-  if (image && !image.isEmpty()) {
-    return writeComposerImage(image.toPNG(), '.png')
-  }
-
-  // WSL2/WSLg doesn't bridge clipboard *images* from the Windows host to the
-  // Linux clipboard Electron reads, so a host screenshot looks empty above.
-  // Pull it straight off the Windows clipboard via PowerShell as a fallback.
-  if (IS_WSL) {
-    const png = readWslWindowsClipboardImage()
-    if (png) {
-      return writeComposerImage(png, '.png')
-    }
-  }
-
-  return ''
+// File-preview/clipboard/image IPC lives in media-ipc.cjs; preview helpers,
+// image writers, and a live-main-window getter are injected.
+registerMediaIpc({
+  getMainWindow: () => mainWindow,
+  ipcMain,
+  IS_WSL,
+  looksBinary,
+  mimeTypeForPath,
+  PREVIEW_LANGUAGE_BY_EXT,
+  saveImageFromUrl,
+  TEXT_PREVIEW_MAX_BYTES,
+  writeComposerImage
 })
 
 ipcMain.handle('hermes:normalizePreviewTarget', (_event, target, baseDir) =>

apps/desktop/electron/media-ipc.cjs

@@ -0,0 +1,121 @@
+'use strict'
+
+const { clipboard, dialog } = require('electron')
+const fs = require('fs')
+const path = require('path')
+
+const { DATA_URL_READ_MAX_BYTES, resolveReadableFileForIpc, TEXT_PREVIEW_SOURCE_MAX_BYTES } = require('./hardening.cjs')
+const { readWslWindowsClipboardImage } = require('./wsl-clipboard-image.cjs')
+
+// File-preview + clipboard + image-save IPC: read a file as a data URL / text
+// preview, native file picker, write clipboard text, and persist composer images
+// (from URL, raw buffer, or the system clipboard, with a WSL host-clipboard
+// fallback). The preview helpers, image writers, and the live main window are
+// injected; selectPaths parents its dialog on getMainWindow().
+function registerMediaIpc({
+  getMainWindow,
+  ipcMain,
+  IS_WSL,
+  looksBinary,
+  mimeTypeForPath,
+  PREVIEW_LANGUAGE_BY_EXT,
+  saveImageFromUrl,
+  TEXT_PREVIEW_MAX_BYTES,
+  writeComposerImage
+}) {
+  ipcMain.handle('hermes:readFileDataUrl', async (_event, filePath) => {
+    const { resolvedPath } = await resolveReadableFileForIpc(filePath, {
+      maxBytes: DATA_URL_READ_MAX_BYTES,
+      purpose: 'File preview'
+    })
+    const data = await fs.promises.readFile(resolvedPath)
+    return `data:${mimeTypeForPath(resolvedPath)};base64,${data.toString('base64')}`
+  })
+
+  ipcMain.handle('hermes:readFileText', async (_event, filePath) => {
+    const { resolvedPath, stat } = await resolveReadableFileForIpc(filePath, {
+      maxBytes: TEXT_PREVIEW_SOURCE_MAX_BYTES,
+      purpose: 'Text preview'
+    })
+    const ext = path.extname(resolvedPath).toLowerCase()
+    const handle = await fs.promises.open(resolvedPath, 'r')
+    const bytesToRead = Math.min(stat.size, TEXT_PREVIEW_MAX_BYTES)
+
+    try {
+      const buffer = Buffer.alloc(bytesToRead)
+      const { bytesRead } = await handle.read(buffer, 0, bytesToRead, 0)
+
+      return {
+        binary: looksBinary(buffer.subarray(0, Math.min(bytesRead, 4096))),
+        byteSize: stat.size,
+        language: PREVIEW_LANGUAGE_BY_EXT[ext] || 'text',
+        mimeType: mimeTypeForPath(resolvedPath),
+        path: resolvedPath,
+        text: buffer.subarray(0, bytesRead).toString('utf8'),
+        truncated: stat.size > TEXT_PREVIEW_MAX_BYTES
+      }
+    } finally {
+      await handle.close()
+    }
+  })
+
+  ipcMain.handle('hermes:selectPaths', async (_event, options = {}) => {
+    const properties = options?.directories ? ['openDirectory'] : ['openFile']
+    if (options?.multiple !== false) properties.push('multiSelections')
+
+    let resolvedDefaultPath
+    if (options?.defaultPath) {
+      try {
+        resolvedDefaultPath = path.resolve(String(options.defaultPath))
+      } catch {
+        resolvedDefaultPath = undefined
+      }
+    }
+
+    const result = await dialog.showOpenDialog(getMainWindow(), {
+      title: options?.title || 'Add context',
+      defaultPath: resolvedDefaultPath,
+      properties,
+      filters: Array.isArray(options?.filters) ? options.filters : undefined
+    })
+
+    if (result.canceled) return []
+    return result.filePaths
+  })
+
+  ipcMain.handle('hermes:writeClipboard', (_event, text) => {
+    clipboard.writeText(String(text || ''))
+    return true
+  })
+
+  ipcMain.handle('hermes:saveImageFromUrl', (_event, url) => saveImageFromUrl(String(url || '')))
+
+  ipcMain.handle('hermes:saveImageBuffer', async (_event, payload) => {
+    const data = payload?.data
+    if (!data) throw new Error('saveImageBuffer: missing data')
+
+    const buffer = Buffer.isBuffer(data) ? data : Buffer.from(data)
+    return writeComposerImage(buffer, payload?.ext || '.png')
+  })
+
+  ipcMain.handle('hermes:saveClipboardImage', async () => {
+    const image = clipboard.readImage()
+    if (image && !image.isEmpty()) {
+      return writeComposerImage(image.toPNG(), '.png')
+    }
+
+    // WSL2/WSLg doesn't bridge clipboard *images* from the Windows host to the
+    // Linux clipboard Electron reads, so a host screenshot looks empty above.
+    // Pull it straight off the Windows clipboard via PowerShell as a fallback.
+    if (IS_WSL) {
+      const png = readWslWindowsClipboardImage()
+      if (png) {
+        return writeComposerImage(png, '.png')
+      }
+    }
+
+    return ''
+  })
+}
+
+module.exports = { registerMediaIpc }

apps/desktop/electron/media-ipc.test.cjs

@@ -0,0 +1,94 @@
+'use strict'
+
+const assert = require('node:assert/strict')
+const test = require('node:test')
+
+const { registerMediaIpc } = require('./media-ipc.cjs')
+
+function fakeIpcMain() {
+  const handlers = new Map()
+
+  return {
+    handlers,
+    handle(channel, handler) {
+      assert.ok(!handlers.has(channel), `duplicate registration for ${channel}`)
+      handlers.set(channel, handler)
+    }
+  }
+}
+
+function deps(overrides = {}) {
+  return {
+    getMainWindow: () => null,
+    IS_WSL: false,
+    looksBinary: () => false,
+    mimeTypeForPath: () => 'text/plain',
+    PREVIEW_LANGUAGE_BY_EXT: {},
+    saveImageFromUrl: async () => '/img/from-url.png',
+    TEXT_PREVIEW_MAX_BYTES: 1024,
+    writeComposerImage: async () => '/img/written.png',
+    ...overrides
+  }
+}
+
+test('registerMediaIpc wires the file-preview / clipboard / image-save channels', () => {
+  const ipcMain = fakeIpcMain()
+
+  registerMediaIpc({ ipcMain, ...deps() })
+
+  assert.deepEqual([...ipcMain.handlers.keys()].sort(), [
+    'hermes:readFileDataUrl',
+    'hermes:readFileText',
+    'hermes:saveClipboardImage',
+    'hermes:saveImageBuffer',
+    'hermes:saveImageFromUrl',
+    'hermes:selectPaths',
+    'hermes:writeClipboard'
+  ])
+
+  for (const handler of ipcMain.handlers.values()) {
+    assert.equal(typeof handler, 'function')
+  }
+})
+
+test('saveImageFromUrl delegates to the injected writer', async () => {
+  const ipcMain = fakeIpcMain()
+  const seen = []
+
+  registerMediaIpc({
+    ipcMain,
+    ...deps({
+      saveImageFromUrl: async url => {
+        seen.push(url)
+
+        return '/p.png'
+      }
+    })
+  })
+
+  assert.equal(await ipcMain.handlers.get('hermes:saveImageFromUrl')({}, 'https://x/y.png'), '/p.png')
+  assert.deepEqual(seen, ['https://x/y.png'])
+})
+
+test('saveImageBuffer rejects missing data and otherwise writes via the injected writer', async () => {
+  const ipcMain = fakeIpcMain()
+  const writes = []
+
+  registerMediaIpc({
+    ipcMain,
+    ...deps({
+      writeComposerImage: async (buf, ext) => {
+        writes.push([buf.toString('utf8'), ext])
+
+        return '/written.gif'
+      }
+    })
+  })
+
+  await assert.rejects(() => ipcMain.handlers.get('hermes:saveImageBuffer')({}, {}), /missing data/)
+
+  const out = await ipcMain.handlers.get('hermes:saveImageBuffer')({}, { data: Buffer.from('hi'), ext: '.gif' })
+
+  assert.equal(out, '/written.gif')
+  assert.deepEqual(writes, [['hi', '.gif']])
+})