diff --git a/DIVERGENCES.md b/DIVERGENCES.md
index 8e43663adf..0a85cedfb2 100644
--- a/DIVERGENCES.md
+++ b/DIVERGENCES.md
@@ -240,7 +240,7 @@ from the squash message first, or use a plain merge.
 | `script/publish.ts` | The `if (Script.release)` block calling `packages/desktop/scripts/finalize-latest-{json,yml}.ts` removed, replaced by a comment. | Both finalizers existed to assemble update metadata into a GitHub release, which the fork no longer publishes to. electron-builder already writes a correct per-platform `latest*.yml` next to each installer, and the fork builds one arch per platform (macOS is universal — see the universal-builds row), so there is nothing left to merge. | Keep removed. If upstream adds further desktop release steps here, drop them unless they target the bucket. |
 | `packages/desktop/scripts/finalize-latest-json.ts`, `packages/desktop/scripts/finalize-latest-yml.ts` | Deleted. | Both `gh release upload` into a GitHub release the fork does not use. `finalize-latest-yml.ts` merged per-arch `latest*.yml` from an upstream build matrix the fork does not run; `finalize-latest-json.ts` additionally built a Tauri-style `latest.json` signed with `@tauri-apps/cli signer` that nothing in the Electron updater path ever reads, and had gone stale besides — it hardcoded `opencode-desktop-mac-{x64,arm64}.app.tar.gz`, an artifact name and format this fork never produces. Leaving them in place is a trap: they look like the release path and upload to the wrong place. | Keep deleted (`git rm` the upstream side of modify/delete conflicts). If a future build matrix produces two `latest.yml` files for one platform (Windows x64 + arm64), write a bucket-targeted merge step rather than restoring these. |
 | `packages/desktop/scripts/prebuild.ts` | On macOS, after the node-sidecar build, runs `bun script/build-vzhelper.ts --universal` in `packages/codev-sandbox` so `dist/codev-vmm` exists (universal) before electron-builder copies it via `mac.extraResources`. | The sandbox vz backend spawns the helper from `process.resourcesPath/codev-vmm` in packaged builds; universal keeps one already-fat Mach-O valid for `--arm64`, `--x64`, and `--universal` packaging (an identical thin binary in both halves would trip `@electron/universal`'s identical-file check). | Keep the darwin-gated build line; take upstream's other steps. It must stay after nothing in particular but before packaging — prebuild is the hook `package:*` runs. |
-| `packages/desktop/scripts/predev.ts` | Runs `bun run install-electron` before the existing icon copy and node-sidecar build. | `bun dev:desktop` was dead on a fresh clone: Electron 42 removed the `postinstall` hook that downloaded the platform binary and exposes it as an `install-electron` bin the consumer must call (electron 41's manifest still had `"postinstall": "node install.js"`; 42.3.3's has no `scripts` field at all), so `bun install` leaves `node_modules/electron` with no `dist/` and `electron-vite dev` aborts with `Error: Electron uninstall` from `getElectronPath`. `predev` is the right hook rather than the root `postinstall`: only someone actually launching the desktop app pays the ~100 MB download, and `install.js` short-circuits once `dist/version` and `path.txt` match, so repeat runs cost nothing. Not added to `prebuild`/`package` — `electron-vite build` never spawns Electron, and `electron-builder` fetches its own copy through `@electron/get`. | Keep our installer line at the top; take upstream's other steps. Drop the line if upstream adds its own binary-install step or pins Electron back below 42. |
+| `packages/desktop/scripts/predev.ts` | Runs `bun run install-electron` before the existing icon copy and node-sidecar build; after them, on macOS only, runs `bun script/build-vzhelper.ts` in `packages/codev-sandbox` (host arch, non-fatal with a warning when no Swift toolchain is present). | `bun dev:desktop` was dead on a fresh clone: Electron 42 removed the `postinstall` hook that downloaded the platform binary and exposes it as an `install-electron` bin the consumer must call (electron 41's manifest still had `"postinstall": "node install.js"`; 42.3.3's has no `scripts` field at all), so `bun install` leaves `node_modules/electron` with no `dist/` and `electron-vite dev` aborts with `Error: Electron uninstall` from `getElectronPath`. `predev` is the right hook rather than the root `postinstall`: only someone actually launching the desktop app pays the ~100 MB download, and `install.js` short-circuits once `dist/version` and `path.txt` match, so repeat runs cost nothing. Not added to `prebuild`/`package` — `electron-vite build` never spawns Electron, and `electron-builder` fetches its own copy through `@electron/get`. The vzhelper build fixes the same fresh-clone class of failure for the Work side: the vz provider's dev `helperPath` points at `codev-sandbox/native/vzhelper/dist/codev-vmm`, which only `prebuild` (packaging) built, so every dev run answered the sandbox dialogs with "sandbox VM helper is not installed". Incremental (~1.5s when up to date). | Keep our installer line at the top and the vzhelper block at the bottom; take upstream's other steps. Drop the installer line if upstream adds its own binary-install step or pins Electron back below 42; the vzhelper block is tied to the fork-only sandbox feature and stays as long as it does. |
 | `packages/ui/src/assets/favicon/` (favicon-v3.svg, favicon-v3.ico, site.webmanifest, favicon-96x96-v3.png, apple-touch-icon-v3.png, web-app-manifest-192/512.png) | New codev mark: the blocky "C" in brand red `#ee0033` on a white tile, generated from the same geometry as the app icon by `packages/desktop/scripts/generate-icons.ts` (4x5 grid, one-unit stroke, unit = 120/1024, corner radius 229/1024); `favicon-v3.svg` is the hand-written 512-unit source of that geometry. The tab and `.ico` icons keep the rounded tile so they read as an app icon; `apple-touch-icon-v3.png` and the two maskable `web-app-manifest-*` icons are square and full-bleed, because iOS and PWA launchers apply their own mask and a pre-rounded icon leaves transparent corners that render black. Manifest name "CoDev Code"/"codev"; its `theme_color`/`background_color` stay `#080808` — those describe the PWA's chrome and splash, not the icon. **Was `#00cdcd` on a dark tile** until this row was rewritten: PR #10 pinned the favicon to the then-cyan TUI banner accent, that banner later moved to the navy/red wordmark, and the favicon was left behind as the only cyan in the tree — visibly so on desktop, where the dock icon was red while the window and notification icons were cyan. | Every surface that draws the mark should draw the same mark: the dock icon, the tab, notifications, the `codev --mini` badge and the landing page icon are now one geometry in one red. Cyan on `#131010` was the higher-contrast tile at 16px (~9.4:1 versus red's ~4.2:1) — a real cost, accepted so the brand reads consistently. | Keep our assets (binary: take ours wholesale). Regenerate with the script rather than hand-editing, and edit `icons/icon.svg` + `favicon-v3.svg` together if the geometry ever changes. |
 | `AGENTS.md` | Default-branch note: `dev` → `main` (single merged line; upstream has two lines saying local `main` may not exist); added fork bullets requiring every upstream-file change to get a `DIVERGENCES.md` row (and matching en + es doc updates) in the same PR, and pointing agents at this file's Divergence policy (prefer config/plugins, then `packages/codev-*`, upstream edits last) and Syncing with upstream sections | The fork's default branch is `main` (see the workflow-triggers row); agents kept basing diffs on a nonexistent `dev`. Agents edit upstream files without recording the divergence — and don't apply the placement policy or sync runbook — unless the instructions file says to. | Keep our lines; take upstream's other guidance. |
 | `README.md` | Replaced with fork README | Fork identity, sync + divergence policy. | Keep ours entirely. |
diff --git a/packages/desktop/scripts/predev.ts b/packages/desktop/scripts/predev.ts
index 90b22de5bc..d75c61687f 100644
--- a/packages/desktop/scripts/predev.ts
+++ b/packages/desktop/scripts/predev.ts
@@ -9,3 +9,17 @@ await $`bun run install-electron`
 await $`bun ./scripts/copy-icons.ts ${process.env.CODEV_CHANNEL ?? "dev"}`
 
 await $`cd ../opencode && bun script/build-node.ts`
+
+// The sandbox vz backend needs the codev-vmm helper; without it a dev run's
+// Work side answers every sandbox dialog with "sandbox VM helper is not
+// installed". Packaging builds it in prebuild, but nothing built it for `bun
+// dev`, so fresh clones sat in that state. Host arch only (packaging does
+// --universal), incremental (~1.5s when up to date), and non-fatal: a machine
+// without a Swift toolchain still gets a working app, minus sandboxes.
+if (process.platform === "darwin") {
+  await $`cd ../codev-sandbox && bun script/build-vzhelper.ts`.catch(() => {
+    console.warn(
+      "could not build the sandbox VM helper (is a Swift toolchain installed?); Work sandboxes will be unavailable",
+    )
+  })
+}