diff --git a/apps/desktop/README.i18n.yaml b/apps/desktop/README.i18n.yaml
index 7d355c9801..d25e3c5ef8 100644
--- a/apps/desktop/README.i18n.yaml
+++ b/apps/desktop/README.i18n.yaml
@@ -2,5 +2,5 @@
 # side as of the last confirmed-consistent state. Both languages carry equal authority;
 # after editing either side, bring the other along and re-record with:
 #   pnpm run verify-translation-pairing --write apps/desktop/README.md
-README.md: 87b16ac8fd7ec269e8c02a34a32e6593b38aec0a
-README.zh.md: 895fdd972148c90bad00916a35b21cebff8842e8
+README.md: ec3f2f44d5e49db00bd595588a0594bcee0a1538
+README.zh.md: 50fba340a0edc114a75d4b6363b8e6c42be0c45f
diff --git a/apps/desktop/README.md b/apps/desktop/README.md
index 87b16ac8fd..ec3f2f44d5 100644
--- a/apps/desktop/README.md
+++ b/apps/desktop/README.md
@@ -399,7 +399,7 @@ The downloaded bytes are inert, and the installation call is recorded rather tha
 
 ## Low-level development overrides
 
-An unpackaged Electron process uses `.desktop-build/development/project` under its application directory as its development project. `DSH_DESKTOP_PNPM_ENTRY` and `DSH_DESKTOP_DSH_DIR` select explicit runtime resources. Packaged applications ignore these variables, resolve signed resources from `process.resourcesPath`, and use the managed Desktop profile.
+An unpackaged Electron process uses `.desktop-build/development/project` under its application directory as its development project. `DSH_DESKTOP_PNPM_ENTRY` and `DSH_DESKTOP_DSH_DIR` are optional overrides with application-path defaults. `DSH_DESKTOP_PRIMARY_RUNTIME_DIR` is required for every unpackaged launch: the development launchers (`dev:desktop`, `start:desktop`, and the workspace-update qualification runner) set it to the primary-runtime directory of the target they prepared, and a launch without it fails with the fatal startup dialog. The launcher must set it because the shell cannot derive that directory from `process.arch`: the build target fixes Windows to x64 while the host may be arm64. Packaged applications ignore these variables, resolve signed resources from `process.resourcesPath`, and use the managed Desktop profile.
 
 ## Known limitations
 
@@ -408,6 +408,7 @@ An unpackaged Electron process uses `.desktop-build/development/project` under i
 - Release signing, notarization, update hosting, and previous-version installed-artifact qualification require the production release environment.
 - Dependency lifecycle scripts follow pnpm’s build permissions; Desktop provides no separate approval dialog.
 - The desktop shell shares sessions, settings, credentials, workspaces, and storage under `$DSH_HOME` with CLI dsh, while executable packages, plugin activation, and lockfiles remain separate.
+- Unpackaged startup on an Electron win32-arm64 host now succeeds, but the payload remains x64: the architecture check in `packages/skill/tool-workspace-dependencies/src/index.ts` compares the recorded payload architecture against the host `process.arch`, so the `load_workspace_dependencies` tool can still reject the primary runtime.
 
 Sign in opens the configured platform page in the system browser. The Host owns PKCE and a temporary loopback callback, saves the credential before entering the workspace, and redirects the browser to the platform completion page. Opened and copied authorization links carry the effective Desktop theme as `theme=light` or `theme=dark`; `system` resolves at the time of the action. Cancel withdraws the local attempt even if the platform page later approves it. Settings offers Account sign-out; without a separate API key, sign-out returns to the welcome window. Packaged applications register dsh://open to show the window without passing credentials. On macOS, the development launcher prepares an ad-hoc-signed `Harness Dev.app` under `.desktop-build/development`, declares `dsh` in its Info.plist, and registers it with Launch Services. It loads the current workspace and records the selected development home, browser-data path, and debug settings for cold starts. Starting this bundle makes it the default `dsh://` handler; starting the packaged application registers the packaged handler again. The generated bundle does not contain account tokens and requires the workspace and prepared runtime to remain available.
 
diff --git a/apps/desktop/README.zh.md b/apps/desktop/README.zh.md
index 895fdd9721..50fba340a0 100644
--- a/apps/desktop/README.zh.md
+++ b/apps/desktop/README.zh.md
@@ -399,7 +399,7 @@ node apps/desktop/node_modules/pnpm/bin/pnpm.mjs --dir apps/desktop run test:upd
 
 ## 底层开发覆盖项
 
-未打包的 Electron 进程使用应用目录下的 `.desktop-build/development/project` 作为开发项目。`DSH_DESKTOP_PNPM_ENTRY` 和 `DSH_DESKTOP_DSH_DIR` 用于选择明确的运行时资源。打包应用会忽略这些变量，从 `process.resourcesPath` 解析签名资源，并使用受管 Desktop profile。
+未打包的 Electron 进程使用应用目录下的 `.desktop-build/development/project` 作为开发项目。`DSH_DESKTOP_PNPM_ENTRY` 和 `DSH_DESKTOP_DSH_DIR` 是带应用路径默认值的可选覆盖项。每次未打包启动都必须设置 `DSH_DESKTOP_PRIMARY_RUNTIME_DIR`：开发启动器（`dev:desktop`、`start:desktop` 及工作区更新验证运行器）会把它设置为自己已准备目标的 primary-runtime 目录；缺少该变量的启动会以致命启动对话框失败。启动器必须设置它，因为壳无法从 `process.arch` 推导该目录：构建目标将 Windows 固定为 x64，而宿主可能是 arm64。打包应用会忽略这些变量，从 `process.resourcesPath` 解析签名资源，并使用受管 Desktop profile。
 
 ## 已知限制
 
@@ -408,6 +408,7 @@ node apps/desktop/node_modules/pnpm/bin/pnpm.mjs --dir apps/desktop run test:upd
 - 发布签名、公证、更新托管和跨上一版本的已安装产物验证需要生产发布环境。
 - 依赖的生命周期脚本遵循 pnpm 的构建权限；Desktop 不提供单独的审批对话框。
 - 桌面壳与 CLI dsh 共享 `$DSH_HOME` 下的会话、设置、凭据、工作区和存储，但可执行包、插件激活和锁文件彼此隔离。
+- 在 Electron win32-arm64 宿主上，未打包启动现在可以成功，但载荷仍为 x64：`packages/skill/tool-workspace-dependencies/src/index.ts` 的架构校验会把载荷记录的架构与宿主 `process.arch` 比较，因此 `load_workspace_dependencies` 工具仍可能拒绝 primary runtime。
 
 登录会在系统浏览器中打开配置的平台页面。Host 负责 PKCE 和临时本机回调，在进入工作区前保存凭证，再将浏览器跳转到平台完成页。打开和复制的授权链接通过 `theme=light` 或 `theme=dark` 携带当前生效的 Desktop 主题；`system` 在执行操作时解析。即使平台页面随后批准，取消仍会撤销本地尝试。设置中的账号页面提供退出；没有独立 API Key 时，退出后返回欢迎窗。打包应用注册 dsh://open，只显示窗口而不传递凭证。macOS 开发启动器在 `.desktop-build/development` 下准备经临时签名的 `Harness Dev.app`，在 Info.plist 中声明 `dsh` 并注册到 Launch Services。它加载当前工作区，并记录选定的开发 home、浏览器数据路径和调试设置，以供冷启动使用。启动此应用会将其设为 `dsh://` 默认处理程序；启动打包应用会重新注册打包版处理程序。生成的应用包不包含账号 token，依赖工作区和已准备的运行环境继续存在。
 
diff --git a/apps/desktop/scripts/desktop-build-paths.d.mts b/apps/desktop/scripts/desktop-build-paths.d.mts
index b26c633d9c..9a8e408ed1 100644
--- a/apps/desktop/scripts/desktop-build-paths.d.mts
+++ b/apps/desktop/scripts/desktop-build-paths.d.mts
@@ -36,6 +36,17 @@ export function resolveDesktopBuildTarget(
  */
 export function desktopTargetBuildPaths(target: DesktopAutoUpdateTarget): DesktopTargetBuildPaths
 
+/**
+ * Return the platform and architecture of the payload one release target prepares.
+ * Windows is prepared as x64 only, so this differs from the build host on an arm64 Windows machine.
+ * @param target - Supported Desktop target name.
+ * @returns Platform and architecture of the prepared payload.
+ */
+export function desktopTargetPlatform(target: DesktopAutoUpdateTarget): {
+  readonly platform: 'darwin' | 'win32'
+  readonly arch: 'arm64' | 'x64'
+}
+
 /**
  * Resolve the paths owned by the target selected in a packaging environment.
  * @param env - Packaging environment.
@@ -48,3 +59,16 @@ export function resolveDesktopTargetBuildPaths(
   hostPlatform?: NodeJS.Platform,
   hostArch?: string,
 ): DesktopTargetBuildPaths
+
+/**
+ * Resolve the primary-runtime directory an unpackaged development launch uses.
+ * @param env - Packaging environment.
+ * @param hostPlatform - Build-host platform used when no target override exists.
+ * @param hostArch - Build-host architecture used when no target override exists.
+ * @returns Primary-runtime directory prepared for the selected target.
+ */
+export function developmentRuntimeDirectory(
+  env?: NodeJS.ProcessEnv,
+  hostPlatform?: NodeJS.Platform,
+  hostArch?: string,
+): string
diff --git a/apps/desktop/scripts/desktop-build-paths.mjs b/apps/desktop/scripts/desktop-build-paths.mjs
index 841da2c4ba..4f33e804c3 100644
--- a/apps/desktop/scripts/desktop-build-paths.mjs
+++ b/apps/desktop/scripts/desktop-build-paths.mjs
@@ -29,15 +29,19 @@ export function resolveDesktopBuildTarget(
   return /** @type {'mac-arm64' | 'mac-x64' | 'win-x64'} */ (target)
 }
 
+function assertSupportedTarget(target) {
+  if (!SUPPORTED_TARGETS.has(target)) {
+    throw new Error(`desktop build paths: unsupported target ${String(target)}`)
+  }
+}
+
 /**
  * Return the mutable preparation and artifact directories owned by one release target.
  * @param {'mac-arm64' | 'mac-x64' | 'win-x64'} target - Supported Desktop target name.
  * @returns {{ root: string, artifacts: string, unsignedArtifacts: string, runtime: string, packageSet: string, dsh: string, dshPnpm: string, electron: string, packedDsh: string, packedVendor: string, packedLandlock: string, downloads: string }} Target paths plus the shared immutable download cache.
  */
 export function desktopTargetBuildPaths(target) {
-  if (!SUPPORTED_TARGETS.has(target)) {
-    throw new Error(`desktop build paths: unsupported target ${String(target)}`)
-  }
+  assertSupportedTarget(target)
   const root = join(BUILD_ROOT, 'targets', target)
   const packed = join(root, 'packed')
   return {
@@ -56,6 +60,20 @@ export function desktopTargetBuildPaths(target) {
   }
 }
 
+/**
+ * Return the platform and architecture of the payload one release target prepares.
+ * Windows is prepared as x64 only, so this differs from the build host on an arm64 Windows machine.
+ * @param {'mac-arm64' | 'mac-x64' | 'win-x64'} target - Supported Desktop target name.
+ * @returns {{ platform: 'darwin' | 'win32', arch: 'arm64' | 'x64' }} Platform and architecture of the prepared payload.
+ */
+export function desktopTargetPlatform(target) {
+  assertSupportedTarget(target)
+  return {
+    platform: /** @type {'darwin' | 'win32'} */ (target === 'win-x64' ? 'win32' : 'darwin'),
+    arch: /** @type {'arm64' | 'x64'} */ (target === 'mac-arm64' ? 'arm64' : 'x64'),
+  }
+}
+
 /**
  * Resolve the paths owned by the target selected in a packaging environment.
  * @param {NodeJS.ProcessEnv} env - Packaging environment.
@@ -70,3 +88,20 @@ export function resolveDesktopTargetBuildPaths(
 ) {
   return desktopTargetBuildPaths(resolveDesktopBuildTarget(env, hostPlatform, hostArch))
 }
+
+/**
+ * Resolve the primary-runtime directory an unpackaged development launch uses.
+ * The build target fixes Windows to x64, so the shell cannot derive this directory from
+ * the architecture of the process that launched it.
+ * @param {NodeJS.ProcessEnv} env - Packaging environment.
+ * @param {NodeJS.Platform} hostPlatform - Build-host platform used when no target override exists.
+ * @param {string} hostArch - Build-host architecture used when no target override exists.
+ * @returns {string} Primary-runtime directory prepared for the selected target.
+ */
+export function developmentRuntimeDirectory(
+  env = process.env,
+  hostPlatform = process.platform,
+  hostArch = process.arch,
+) {
+  return join(resolveDesktopTargetBuildPaths(env, hostPlatform, hostArch).runtime, 'primary-runtime')
+}
diff --git a/apps/desktop/scripts/dev.ts b/apps/desktop/scripts/dev.ts
index 74840eae03..fdd724e579 100644
--- a/apps/desktop/scripts/dev.ts
+++ b/apps/desktop/scripts/dev.ts
@@ -7,6 +7,7 @@ import { join, resolve } from 'node:path'
 import { parseArgs } from 'node:util'
 import { DESKTOP_HOST_PROTOCOL_VERSION } from '../src/host-protocol.ts'
 import type { DesktopRelease } from '../src/release.ts'
+import { developmentRuntimeDirectory, resolveDesktopBuildTarget } from './desktop-build-paths.mjs'
 import { prepareDevelopmentProject } from './development-project.ts'
 import { prepareDevelopmentApp } from './development-app.ts'
 import { preparePrimaryRuntime } from './prepare-primary-runtime.ts'
@@ -67,6 +68,7 @@ async function launchElectron(): Promise<void> {
   const environment: NodeJS.ProcessEnv = {
     ...process.env,
     DSH_HOME: home,
+    DSH_DESKTOP_PRIMARY_RUNTIME_DIR: process.env.DSH_DESKTOP_PRIMARY_RUNTIME_DIR ?? developmentRuntimeDirectory(),
     DSH_DESKTOP_HOST_INSPECT_PORT: String(hostPort),
     DSH_DESKTOP_OPEN_DEVTOOLS: process.env.DSH_DESKTOP_OPEN_DEVTOOLS ?? '1',
     ELECTRON_ENABLE_LOGGING: process.env.ELECTRON_ENABLE_LOGGING ?? '1',
@@ -115,6 +117,7 @@ async function main(): Promise<void> {
     hostDir: join(REPOSITORY_ROOT, 'apps', 'desktop-host'),
     dependencyDir: join(REPOSITORY_ROOT, 'node_modules', '.pnpm', 'node_modules'),
     release,
+    target: resolveDesktopBuildTarget(),
   })
   await preparePrimaryRuntime()
   await launchElectron()
diff --git a/apps/desktop/scripts/development-project.ts b/apps/desktop/scripts/development-project.ts
index 36c70baff0..d544ce6d36 100644
--- a/apps/desktop/scripts/development-project.ts
+++ b/apps/desktop/scripts/development-project.ts
@@ -16,6 +16,8 @@ import { dirname, join } from 'node:path'
 import { createDevelopmentProjectMetadata } from '../src/project-manager.ts'
 import type { DesktopRelease } from '../src/release.ts'
 import { DESKTOP_RUNTIME_FILE, type DesktopRuntimeDescriptor } from '../src/runtime-tree.ts'
+import type { DesktopAutoUpdateTarget } from './desktop-auto-update-environment.mjs'
+import { desktopTargetPlatform } from './desktop-build-paths.mjs'
 
 interface PackageManifest {
   readonly name?: string
@@ -35,6 +37,8 @@ export interface DevelopmentProjectOptions {
   readonly dependencyDir: string
   /** Release identity written into the disposable project metadata. */
   readonly release: DesktopRelease
+  /** Build target whose prepared payload the disposable project runs against. */
+  readonly target: DesktopAutoUpdateTarget
 }
 
 function readManifest(path: string): PackageManifest {
@@ -115,7 +119,7 @@ function mirrorWorkspaceDependencies(roots: readonly string[], destinationRoot:
 
 /**
  * Replace one disposable project with links to the current built workspace.
- * @param options - Project destination, CLI package, and release identity.
+ * @param options - Project destination, CLI package, release identity, and build target.
  * @returns the absolute project directory supplied by the caller.
  */
 export function prepareDevelopmentProject(options: DevelopmentProjectOptions): string {
@@ -159,7 +163,7 @@ export function prepareDevelopmentProject(options: DevelopmentProjectOptions): s
     return typeof manifest.version === 'string' ? [{ name, version: manifest.version, path: `node_modules/${name}` }] : []
   })
   const runtime: DesktopRuntimeDescriptor = { schemaVersion: 1, release: options.release,
-    platform: process.platform, arch: process.arch, sharedPackages, files: [] }
+    ...desktopTargetPlatform(options.target), sharedPackages, files: [] }
   writeFileSync(join(options.projectDir, DESKTOP_RUNTIME_FILE), `${JSON.stringify(runtime, undefined, 2)}\n`)
   return options.projectDir
 }
diff --git a/apps/desktop/scripts/test-workspace-updates.ts b/apps/desktop/scripts/test-workspace-updates.ts
index 669d572b9d..41f40caa09 100644
--- a/apps/desktop/scripts/test-workspace-updates.ts
+++ b/apps/desktop/scripts/test-workspace-updates.ts
@@ -8,6 +8,7 @@ import { fileURLToPath } from 'node:url'
 import { createDevelopmentProjectMetadata, createPluginProfile } from '../src/project-manager.ts'
 import { removeOwnedDirectory } from '../src/owned-directory.ts'
 import { DESKTOP_HOST_PROTOCOL_VERSION } from '../src/host-protocol.ts'
+import { desktopTargetPlatform, developmentRuntimeDirectory, resolveDesktopBuildTarget } from './desktop-build-paths.mjs'
 
 const repo = resolve(import.meta.dirname, '../../..')
 const interactive = process.argv.includes('--interactive')
@@ -27,10 +28,11 @@ try {
     nodeVersion: execFileSync(electron, ['-p', 'process.versions.node'],
       { encoding: 'utf8', env: { ...process.env, ELECTRON_RUN_AS_NODE: '1' }, windowsHide: true }).trim(),
     pnpmVersion: pnpm.version, hostProtocolVersion: DESKTOP_HOST_PROTOCOL_VERSION }
+  const target = resolveDesktopBuildTarget()
   createDevelopmentProjectMetadata(project, release)
   createPluginProfile(profile)
   await writeFile(join(project, 'desktop-runtime.json'), JSON.stringify({
-    schemaVersion: 1, release, platform: process.platform, arch: process.arch, files: [],
+    schemaVersion: 1, release, ...desktopTargetPlatform(target), files: [],
     sharedPackages: ['@deepseek-ai/dsh', '@deepseek-ai/dsh-desktop-host']
       .map(name => ({ name, version: manifest.version, path: `node_modules/${name}` })),
   }))
@@ -43,7 +45,6 @@ try {
   for (const owner of [application, project]) {
     await symlink(join(repo, 'node_modules/.pnpm/node_modules'), join(owner, 'node_modules'), process.platform === 'win32' ? 'junction' : 'dir')
   }
-  const target = `${process.platform === 'darwin' ? 'mac' : 'win'}-${process.arch}`
   const targetRoot = join(application, '.desktop-build/targets', target)
   await mkdir(targetRoot, { recursive: true })
   await symlink(join(repo, 'apps/desktop/.desktop-build/targets', target, 'runtime'), join(targetRoot, 'runtime'),
@@ -61,7 +62,7 @@ try {
     ...(interactive ? ['--interactive'] : [])], {
     cwd: root, env: { ...environment, DSH_HOME: join(root, 'home'), USERPROFILE: root, HOME: root,
       TEMP: root, TMP: root, TMPDIR: root, DSH_WORKSPACE_UPDATE_ROOT: root, DSH_WORKSPACE_UPDATE_TOKEN: randomUUID(),
-      DSH_DESKTOP_OPEN_DEVTOOLS: '0' },
+      DSH_DESKTOP_PRIMARY_RUNTIME_DIR: developmentRuntimeDirectory(), DSH_DESKTOP_OPEN_DEVTOOLS: '0' },
     // Hiding the GUI process suppresses its first window and can suspend renderer frame callbacks.
     stdio: 'inherit', windowsHide: false,
   })
diff --git a/apps/desktop/src/main.ts b/apps/desktop/src/main.ts
index 9f8ad5c22f..6690a3c69c 100644
--- a/apps/desktop/src/main.ts
+++ b/apps/desktop/src/main.ts
@@ -139,6 +139,14 @@ function runtimeResources(): RuntimeResources {
   return { node, nodeBin, pnpm, dsh }
 }
 
+function developmentPrimaryRuntime(): string {
+  const directory = process.env.DSH_DESKTOP_PRIMARY_RUNTIME_DIR
+  if (directory === undefined || directory === '') {
+    throw new Error('dsh desktop: DSH_DESKTOP_PRIMARY_RUNTIME_DIR is required for an unpackaged launch')
+  }
+  return directory
+}
+
 function developmentHostInspectPort(enabled: boolean): number | undefined {
   const configured = process.env.DSH_DESKTOP_HOST_INSPECT_PORT
   if (!enabled || configured === undefined || configured === '') return undefined
@@ -289,6 +297,9 @@ async function main(): Promise<void> {
   const resources = runtimeResources()
   const paths = resolveDesktopPaths()
   const development = !app.isPackaged
+  const primaryRuntime = development
+    ? developmentPrimaryRuntime()
+    : join(process.resourcesPath, 'runtime', 'primary-runtime')
   const activeProject = paths.profile
   const manager = new DesktopProjectManager(paths, resources)
   let quitting = false
@@ -370,8 +381,7 @@ async function main(): Promise<void> {
     const hostInspectPort = developmentHostInspectPort(development)
     const host = new DesktopHostProcess(resources.node, resources.dsh, activeProject,
       hostInspectPort, process.env, onFailure,
-      development ? join(app.getAppPath(), '.desktop-build', 'targets', `${process.platform === 'darwin' ? 'mac' : 'win'}-${process.arch}`, 'runtime', 'primary-runtime')
-        : join(process.resourcesPath, 'runtime', 'primary-runtime'),
+      primaryRuntime,
       resources, (next) => { platformView.setSession(next) })
     return {
       start: async () => {
diff --git a/apps/desktop/tests/desktop-build-paths.spec.ts b/apps/desktop/tests/desktop-build-paths.spec.ts
index a163885f6d..a5e9faf296 100644
--- a/apps/desktop/tests/desktop-build-paths.spec.ts
+++ b/apps/desktop/tests/desktop-build-paths.spec.ts
@@ -2,6 +2,8 @@ import { join, sep } from 'node:path'
 import { describe, expect, it } from 'vitest'
 import {
   desktopTargetBuildPaths,
+  desktopTargetPlatform,
+  developmentRuntimeDirectory,
   resolveDesktopBuildTarget,
 } from '../scripts/desktop-build-paths.mjs'
 
@@ -39,6 +41,22 @@ describe('desktop build paths', () => {
     expect(arm64.downloads).not.toContain(`${sep}targets${sep}`)
   })
 
+  it('resolves the development primary runtime from the build target rather than the host architecture', () => {
+    expect(developmentRuntimeDirectory({}, 'darwin', 'arm64'))
+      .toContain(join('targets', 'mac-arm64', 'runtime', 'primary-runtime'))
+    expect(developmentRuntimeDirectory({}, 'darwin', 'x64'))
+      .toContain(join('targets', 'mac-x64', 'runtime', 'primary-runtime'))
+    expect(developmentRuntimeDirectory({}, 'win32', 'arm64'))
+      .toContain(join('targets', 'win-x64', 'runtime', 'primary-runtime'))
+  })
+
+  it('maps every target to the platform and architecture of the payload it prepares', () => {
+    expect(desktopTargetPlatform('mac-arm64')).toEqual({ platform: 'darwin', arch: 'arm64' })
+    expect(desktopTargetPlatform('mac-x64')).toEqual({ platform: 'darwin', arch: 'x64' })
+    expect(desktopTargetPlatform('win-x64')).toEqual({ platform: 'win32', arch: 'x64' })
+    expect(() => desktopTargetPlatform('linux-x64' as 'mac-x64')).toThrow(/unsupported target/u)
+  })
+
   it('resolves environment overrides and rejects unsupported targets', () => {
     expect(resolveDesktopBuildTarget({
       DSH_DESKTOP_TARGET_PLATFORM: 'darwin',
diff --git a/apps/desktop/tests/development-project.spec.ts b/apps/desktop/tests/development-project.spec.ts
index 07e0a0a5ca..d08b82d3ac 100644
--- a/apps/desktop/tests/development-project.spec.ts
+++ b/apps/desktop/tests/development-project.spec.ts
@@ -46,9 +46,10 @@ describe('desktop development project', () => {
     writeFileSync(join(host, 'lib/index.js'), '')
     writeFileSync(join(dependency, 'package.json'), JSON.stringify({ name: 'unhoisted', version: '1.2.3' }))
     symlinkSync(dependency, join(cli, 'node_modules/unhoisted'), process.platform === 'win32' ? 'junction' : 'dir')
-    const project = prepareDevelopmentProject({ projectDir: join(root, 'runtime'), cliDir: cli, hostDir: host, dependencyDir: hoisted, release: release() })
+    const project = prepareDevelopmentProject({ projectDir: join(root, 'runtime'), cliDir: cli, hostDir: host, dependencyDir: hoisted, release: release(), target: 'mac-arm64' })
     expect(realpathSync(join(project, 'node_modules/unhoisted'))).toBe(realpathSync(dependency))
-    const descriptor = JSON.parse(readFileSync(join(project, 'desktop-runtime.json'), 'utf8')) as { sharedPackages: unknown[] }
+    const descriptor = JSON.parse(readFileSync(join(project, 'desktop-runtime.json'), 'utf8')) as { platform: string; arch: string; sharedPackages: unknown[] }
+    expect(descriptor).toMatchObject({ platform: 'darwin', arch: 'arm64' })
     expect(descriptor.sharedPackages).toContainEqual({ name: 'unhoisted', version: '1.2.3', path: 'node_modules/unhoisted' })
   })
 
@@ -76,6 +77,7 @@ describe('desktop development project', () => {
       hostDir: host,
       dependencyDir: dependencies,
       release: release(),
+      target: 'win-x64',
     })
     expect(realpathSync(join(project, 'node_modules', '@deepseek-ai', 'dsh'))).toBe(realpathSync(cli))
     expect(realpathSync(join(project, 'node_modules', '@deepseek-ai', 'dsh-desktop-host'))).toBe(realpathSync(host))
@@ -88,6 +90,8 @@ describe('desktop development project', () => {
     }
     expect(manifest.dependencies['@deepseek-ai/dsh']).toBe('1.2.3')
     expect(manifest.dependencies['@deepseek-ai/dsh-desktop-host']).toBe('1.2.3')
+    const descriptor = JSON.parse(readFileSync(join(project, 'desktop-runtime.json'), 'utf8')) as { platform: string; arch: string }
+    expect(descriptor).toMatchObject({ platform: 'win32', arch: 'x64' })
     const manager = new DesktopProjectManager(resolveDesktopPaths(join(root, 'home')), {
       dsh: project,
     })
@@ -115,6 +119,7 @@ describe('desktop development project', () => {
       hostDir: host,
       dependencyDir: dependencies,
       release: release(),
+      target: 'mac-x64',
     })).toThrow(/must be @deepseek-ai\/dsh@1\.2\.3/u)
   })
 })
diff --git a/apps/desktop/tests/main-startup.spec.ts b/apps/desktop/tests/main-startup.spec.ts
index 0242d214a3..9cd00f74c4 100644
--- a/apps/desktop/tests/main-startup.spec.ts
+++ b/apps/desktop/tests/main-startup.spec.ts
@@ -333,6 +333,7 @@ beforeEach(() => {
   vi.spyOn(console, 'info').mockImplementation(() => {})
   vi.stubEnv('DSH_DESKTOP_PNPM_ENTRY', 'test-pnpm')
   vi.stubEnv('DSH_DESKTOP_DSH_DIR', 'test-runtime')
+  vi.stubEnv('DSH_DESKTOP_PRIMARY_RUNTIME_DIR', 'test-primary-runtime')
   vi.stubGlobal('process', { ...process, platform: 'win32', arch: 'x64', resourcesPath: 'desktop-test-resources' })
   vi.stubEnv('DSH_DESKTOP_HOST_INSPECT_PORT', undefined)
   vi.stubEnv('DSH_DESKTOP_DEV_PROJECT_DIR', undefined)
@@ -1621,13 +1622,24 @@ describe('desktop main startup', () => {
     harness.prepared.resolve()
     await harness.hostStarted.promise
     const project = join(harness.app.getAppPath(), '.desktop-build', 'development', 'project')
-    expect(harness.hosts[0]).toMatchObject({ node: process.execPath, runtime: project, profile: 'desktop-test-profile' })
+    expect(harness.hosts[0]).toMatchObject({ node: process.execPath, runtime: project,
+      primaryRuntime: 'test-primary-runtime', profile: 'desktop-test-profile' })
     expect(harness.applyRelease).toHaveBeenCalledOnce()
     harness.hosts[0]!.ready.resolve()
     await harness.navigated.promise
     expect(harness.dialog.showErrorBox).not.toHaveBeenCalled()
   })
 
+  it('fails an unpackaged launch that receives no primary runtime directory', async () => {
+    harness.app.isPackaged = false
+    vi.stubEnv('DSH_DESKTOP_PRIMARY_RUNTIME_DIR', undefined)
+    await import('../src/main.ts')
+    await harness.dialogShown.promise
+    const options = harness.dialog.showMessageBox.mock.calls[0]![0] as MessageBoxOptions
+    expect(options.detail).toContain('DSH_DESKTOP_PRIMARY_RUNTIME_DIR is required for an unpackaged launch')
+    expect(harness.hosts).toHaveLength(0)
+  })
+
   it('keeps startup errors in the existing window without a retry handler', async () => {
     await import('../src/main.ts')
     await harness.preparing.promise
diff --git a/apps/desktop/tests/welcome-flow.e2e.ts b/apps/desktop/tests/welcome-flow.e2e.ts
index 7522430879..9b3dd0f2ed 100644
--- a/apps/desktop/tests/welcome-flow.e2e.ts
+++ b/apps/desktop/tests/welcome-flow.e2e.ts
@@ -98,6 +98,9 @@ describe.skipIf(!existsSync(builtHost))('built Desktop welcome flow', () => {
           nodeVersion: process.versions.node,
           hostProtocolVersion: DESKTOP_HOST_PROTOCOL_VERSION,
         },
+        // This suite assembles a synthetic project on hosts that prepare no Desktop target, and
+        // nothing it exercises compares the descriptor's platform/arch outside packaging.
+        target: 'mac-x64',
       })
       cpSync(join(repository, 'packages/skill/skill-office/assets'), join(root, 'runtime/office-skills'), { recursive: true })
       const nodeBin = join(root, 'runtime/primary-runtime/dependencies/node/bin')
diff --git a/apps/desktop/tests/welcome-startup.spec.ts b/apps/desktop/tests/welcome-startup.spec.ts
index 4a823afdf9..146b2297eb 100644
--- a/apps/desktop/tests/welcome-startup.spec.ts
+++ b/apps/desktop/tests/welcome-startup.spec.ts
@@ -148,6 +148,7 @@ it('starts the Host for welcome onboarding and opens the workspace on skip witho
   vi.stubEnv('DSH_DESKTOP_NODE_BINARY', '/runtime/node')
   vi.stubEnv('DSH_DESKTOP_PNPM_ENTRY', '/runtime/pnpm')
   vi.stubEnv('DSH_DESKTOP_DSH_DIR', '/runtime/dsh')
+  vi.stubEnv('DSH_DESKTOP_PRIMARY_RUNTIME_DIR', '/runtime/primary-runtime')
   vi.stubEnv('DSH_DESKTOP_HOST_INSPECT_PORT', undefined)
   vi.stubEnv('DSH_DESKTOP_OPEN_DEVTOOLS', '0')
   vi.stubEnv('DSH_DESKTOP_MANDATORY_UPDATE_CONFIG', undefined)