diff --git a/src/main/ipc/runtime-environment-mobile-relay-hosts.test.ts b/src/main/ipc/runtime-environment-mobile-relay-hosts.test.ts
new file mode 100644
index 00000000000..99ac27a765d
--- /dev/null
+++ b/src/main/ipc/runtime-environment-mobile-relay-hosts.test.ts
@@ -0,0 +1,75 @@
+import { beforeEach, describe, expect, it, vi } from 'vitest'
+
+const mocks = vi.hoisted(() => {
+  const environments: { id: string; name: string }[] = []
+  return { environments, resolveManaged: vi.fn(), call: vi.fn() }
+})
+
+vi.mock('electron', () => ({ app: { getPath: () => '/user-data' } }))
+vi.mock('../../shared/runtime-environment-store', () => ({
+  listEnvironments: () => mocks.environments
+}))
+vi.mock('../../shared/runtime-environments', () => ({
+  getPreferredPairingOffer: (environment: { endpoint: string }) => ({
+    endpoint: environment.endpoint
+  })
+}))
+vi.mock('./runtime-environment-managed-tunnel', () => ({
+  resolveManagedRuntimeEnvironment: mocks.resolveManaged
+}))
+vi.mock('./runtime-environment-transport-routing', () => ({
+  callRuntimeEnvironment: mocks.call
+}))
+
+import {
+  createRuntimeEnvironmentMobileRelayHosts,
+  retireMobileDesktopRelayEnvironment
+} from './runtime-environment-mobile-relay-hosts'
+
+describe('runtime environment mobile relay hosts', () => {
+  beforeEach(() => {
+    mocks.environments = [{ id: 'env-1', name: 'VM' }]
+    mocks.resolveManaged.mockReset().mockResolvedValue({
+      id: 'env-1',
+      endpoint: 'ws://vm:6768',
+      pairingRevision: 7,
+      createdAt: 1,
+      runtimeId: 'runtime-a'
+    })
+    mocks.call.mockReset()
+  })
+
+  it('resolves a configured server by exact id, fenced by pairing revision and runtime identity', async () => {
+    const hosts = createRuntimeEnvironmentMobileRelayHosts()
+    await expect(hosts.resolve('env-1')).resolves.toEqual({
+      environmentId: 'env-1',
+      fence: '7\0runtime-a',
+      pairing: { endpoint: 'ws://vm:6768' }
+    })
+    expect(mocks.resolveManaged).toHaveBeenCalledWith('/user-data', 'env-1')
+  })
+
+  it('answers null for a name, an unknown id or a removed server, without resolving it', async () => {
+    const hosts = createRuntimeEnvironmentMobileRelayHosts()
+    await expect(hosts.resolve('VM')).resolves.toBeNull()
+    await expect(hosts.resolve('env-2')).resolves.toBeNull()
+    mocks.environments = []
+    await expect(hosts.resolve('env-1')).resolves.toBeNull()
+    expect(mocks.resolveManaged).not.toHaveBeenCalled()
+  })
+
+  it('calls the server as the desktop and reports retirements until unsubscribed', async () => {
+    const hosts = createRuntimeEnvironmentMobileRelayHosts()
+    mocks.call.mockResolvedValue({ id: 'x', ok: true, result: {}, _meta: { runtimeId: 'r' } })
+    const host = (await hosts.resolve('env-1'))!
+    await hosts.call(host, 'status.get', undefined)
+    expect(mocks.call).toHaveBeenCalledWith('/user-data', 'env-1', 'status.get', undefined)
+
+    const retired: string[] = []
+    const stop = hosts.onEnvironmentRetired((id) => retired.push(id))
+    retireMobileDesktopRelayEnvironment('env-1')
+    stop()
+    retireMobileDesktopRelayEnvironment('env-1')
+    expect(retired).toEqual(['env-1'])
+  })
+})