Antigravity Login Issue on MacBook & How I Finally Fixed It (After Hours of Trying)

The Problem

If you're reading this, you're probably stuck in the same nightmare I was: Antigravity shows "Authentication Required Please sign in" no matter what you do. You've reinstalled it. You've cleared the browser cache. You've restarted your MacBook. Nothing works.

Here's the complete story of what happened, every fix I tried, and what finally resolved it.

The symptoms were confusing and contradictory:

• Antigravity's Settings page showed my Google account, so it knew I was logged in

• But the main/Agent view kept showing "Sign In"

• Clicking "Sign In" would open Google auth in the browser, I'd complete it successfully, but Antigravity would loop right back to "Authentication Required"

• I couldn't even sign out, there was no sign-out option because the app was in a broken half-authenticated state

What I Already Tried (That Didn't Work)

Before finding the real fix, I tried everything the internet suggested:

• ❌ Restarted the MacBook

• ❌ Cleared browser cache and cookies

• ❌ Deleted Antigravity and reinstalled it

• ❌ Deleted ~/Library/Application Support/Antigravity/Session Storage

• ❌ Deleted ~/Library/Application Support/Antigravity/Local Storage

• ❌ Deleted auth-tokens, Cookies folders

• ❌ Deleted ~/.gemini/antigravity

• ❌ Used Ctrl+Shift+P → Antigravity: Reset Onboarding

• ❌ Applied the BigInt patch to main.js

• ❌ Switched default browser from Brave to Safari

None of it worked. Here's why, I was missing the actual root cause every single time.

The Root Cause: macOS Keychain

Here's what nobody tells you:

When Antigravity first authenticates, it stores an encrypted token in macOS Keychain under the name "Antigravity Safe Storage". This is completely separate from the app's files in ~/Library/Application Support/.

When you uninstall Antigravity, the app files are removed, but the Keychain entry stays behind. When you reinstall and try to log in again, Antigravity finds this old, expired, corrupted token in Keychain and tries to use it. It fails silently. No error message. Just "Authentication Required" forever.

This is why:

• Other macOS user profiles on the same Mac worked fine (each profile has its own Keychain)

• Reinstalling never helped (Keychain survives uninstalls)

• Clearing Library folders never helped (Keychain is stored separately)

The Fix

Step 1: Kill Antigravity completely

pkill -f Antigravity

Step 2: Delete all app data

rm -rf ~/Library/Application\ Support/Antigravity/
rm -rf ~/.gemini/antigravity
rm -rf ~/Library/Caches/Antigravity/
rm -rf ~/Library/Logs/Antigravity/

Step 3: Delete the Keychain entry (THE KEY STEP)

security delete-generic-password -l "Antigravity Safe Storage"

You should see:

password has been deleted.

Alternatively, do it via UI:

1. Open Keychain Access (Spotlight → search "Keychain Access")

2. Search for antigravity

3. Right-click "Antigravity Safe Storage" → Delete

4. Enter your Mac login password when prompted → click Always Allow

Step 4: Set Safari as default browser temporarily

• Apple menu → System Settings → Desktop & Dock → Default web browser → Safari

  Why Safari? If you use Brave, its aggressive "Auto-redirect tracking URLs" feature intercepts the OAuth callback URL and silently kills the token handoff back to the app.

Step 5: Sign in

1. Open Antigravity

2. Click Sign In

3. Complete Google auth in Safari

4. ✅ Done, switch back to Brave after

Bonus: Why Brave Browser Made It Worse

Even after fixing the Keychain issue, if you use Brave as your default browser, you may still face the auth loop. Brave's Shields intercept OAuth redirect URLs as "tracking URLs" and kill the token handoff. The fix is simple, use Safari (or any non-Brave browser) as your default browser just for the sign-in step.

Conclusion

What I tried	Why it failed
Reinstalling Antigravity	Keychain token survives uninstalls
Clearing Library folders	Keychain is stored separately
BigInt patch	Different issue entirely
Browser cache clear	OAuth token lives in Keychain, not browser
Deleting Keychain entry	✅ This was the actual fix

The corrupted Keychain entry in my case was dated November 21, 2025. A 4-month-old stale token that had been silently blocking every login attempt since then.

If you're stuck on this issue, go straight to the Keychain step. It'll save you hours.