Windows - Google OAuth login completes in browser but app never responds

Google Antigravity
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1

Environment

  • OS: Windows 11 64-bit

  • App install path: C:\Program Files\Google Antigravity

  • App version: latest (downloaded 2026-03-23)

  • Default browser: Chrome

Symptoms

  • Antigravity launches normally

  • Click “Sign in with Google” → Chrome opens → Google OAuth completes → browser shows “You have successfully authenticated”

  • App remains on Setup screen with zero response

  • No error message shown in app

Steps to reproduce

  1. Install Antigravity to C:\Program Files\Google Antigravity

  2. Launch app

  3. Click “Sign in with Google”

  4. Complete Google login in Chrome

  5. App stays on Setup screen, never proceeds

Investigation findings

Registry — protocol correctly registered:

HKEY_CLASSES_ROOT\antigravity\shell\open\command
"C:\Program Files\Google Antigravity\Antigravity.exe" --open-url "--" "%1"

auth.log — only one line, nothing after OAuth:

2026-03-23 11:21:06.005 [info] [Auth] AntigravityAuthMainService initialized

main.log — localhost server starts but never receives callback:

2026-03-23 11:21:05.959 [info] [BrowserOnboardingClientMainService] Starting browser onboarding server
2026-03-23 11:21:05.959 [info] [BrowserOnboardingClientServer] Browser onboarding server started on http://localhost:58338

Browser DevTools Console:

Launched external handler for 'antigravity://oauth-success'

UAC prompt on every OAuth callback shows:

File: Antigravity.exe
"C:\Program Files\Google Antigravity\Antigravity.exe" --open-url "--" "antigravity://oauth-success/"
File source: deleted or moved from this computer

Root cause hypothesis

Two related issues:

  1. The Antigravity.exe binary appears to be unsigned on Windows — UAC shows “file source: deleted or moved” on every OAuth callback, indicating missing code signature

  2. The UAC confirmation dialog interrupts the single-instance IPC timing — by the time the user confirms, the token handshake window has expired and the main instance never receives the OAuth token

The auth.log receiving zero entries after initialization confirms the main process never gets the callback.

Additional observations

  • When app is closed, Start-Process "antigravity://oauth-success" correctly launches the app into Setup screen — protocol routing works

  • When app is running, same command produces no response — single-instance IPC is broken

  • Running app as administrator produces “Another instance is already running as administrator” conflict dialog — confirms IPC failure between instances of different elevation levels

Request

Please either code-sign the Windows binary to prevent UAC interruption, or fix the single-instance IPC to handle delayed OAuth callbacks. This appears to affect all Windows users.