diff --git a/apps/stage-tamagotchi/src/main/services/electron/auto-updater.test.ts b/apps/stage-tamagotchi/src/main/services/electron/auto-updater.test.ts
index 91b7e8bf68..37c52ee887 100644
--- a/apps/stage-tamagotchi/src/main/services/electron/auto-updater.test.ts
+++ b/apps/stage-tamagotchi/src/main/services/electron/auto-updater.test.ts
@@ -293,6 +293,21 @@ describe('setupAutoUpdater', () => {
     expect(service.state.status).toBe('not-available')
   })
 
+  // An install with its own user data directory, for example a test build, must not write into the log of another install.
+  it('writes the updater log in the user data directory and reports that path', async () => {
+    const { appendFile } = await import('node:fs/promises')
+    const { join } = await import('node:path')
+    const fake = createFakeUpdater()
+    const { setupAutoUpdater } = await import('./auto-updater')
+    const service = setupAutoUpdater({ updater: fake.updater })
+    const logFile = join('/tmp/userData', 'logs', 'updater-log.txt')
+
+    fake.setStatus({ status: 'error', error: { code: 'network-error', message: 'Offline.' } })
+
+    await vi.waitFor(() => expect(appendFile).toHaveBeenCalledWith(logFile, expect.stringContaining('network-error')))
+    expect(service.state.diagnostics?.logFilePath).toBe(logFile)
+  })
+
   it('does not touch the updater when the launcher turned it off', async () => {
     const fake = createFakeUpdater({ status: 'disabled', reason: 'store-build' })
     const { setupAutoUpdater } = await import('./auto-updater')
diff --git a/apps/stage-tamagotchi/src/main/services/electron/auto-updater.ts b/apps/stage-tamagotchi/src/main/services/electron/auto-updater.ts
index 85407b0358..b8690208ea 100644
--- a/apps/stage-tamagotchi/src/main/services/electron/auto-updater.ts
+++ b/apps/stage-tamagotchi/src/main/services/electron/auto-updater.ts
@@ -28,14 +28,12 @@ import { channelOfVersion, updateChannels } from '../../../shared/update-channel
 
 const UPDATE_CHANNEL_ENV_KEY = 'AIRI_UPDATE_CHANNEL'
 
-function getCacheRoot() {
-  // NOTICE: Electron resolves the cache directory per platform/app, but the
-  // shipped type definitions here do not expose `cache`, so we cast the key.
-  return app.getPath('cache' as Parameters<typeof app.getPath>[0])
-}
-
+/**
+ * The updater log is next to the session logs of `app/file-logger.ts`, in the user data directory. So an install with
+ * its own user data directory, for example a test build, writes its own log.
+ */
 function updaterLogFile() {
-  return join(getCacheRoot(), 'stage-tamagotchi-updater', 'updater-log.txt')
+  return join(app.getPath('userData'), 'logs', 'updater-log.txt')
 }
 
 async function logToFile(level: 'INFO' | 'WARN' | 'ERROR', message: string) {