环境：
macOS（桌面）
Surge Mac（系统代理模式可用，增强模式可切换）
Antigravity Desktop（Google 登录）
同一网络环境下，Clash Verge / ClashMac 登录正常
复现步骤：
打开 Surge，启用系统代理（System Proxy ON）。
打开 Antigravity，点击 Sign in with Google。
浏览器中完成 Google 身份验证与授权。
返回 Antigravity，观察登录状态。
实际结果：
浏览器授权流程可完整走通。
Antigravity 未进入已登录状态，仍停留在 Sign into Google 页面。
期望结果：
浏览器授权成功后，Antigravity 应自动完成回调并进入已登录状态。
已做排查（A/B）：
Rewrite ON + Enhanced ON：失败
Rewrite OFF + Enhanced ON：失败
Rewrite OFF + Enhanced OFF + System Proxy ON：失败
Rewrite OFF + Enhanced ON + System Proxy ON：失败
补充观察：
Surge 侧 google 相关规则命中明显，说明外网代理链路是通的。
Antigravity 流量有增长，说明请求确实发出。
仅“登录态回写到 App”失败。
同机同网同账号，改用 Clash 可成功，说明不是账号或基础网络故障。
怀疑方向：
OAuth 回调落地（loopback/custom scheme）与 Surge 接管链路兼容性问题。
授权完成后的 token/code 回传阶段被拦截、未正确交付或未被 App 消费。
English Version
Title: Antigravity Google sign-in cannot complete under Surge (browser auth succeeds, app remains on sign-in page)
Environment:
macOS desktop
Surge Mac (System Proxy enabled; Enhanced Mode toggled for testing)
Antigravity Desktop with Google sign-in
Same machine/network/account works with Clash Verge / ClashMac
Steps to reproduce:
Enable Surge System Proxy (System Proxy ON).
Open Antigravity and click Sign in with Google.
Complete Google authentication/consent in browser.
Return to Antigravity and check login status.
Actual result:
Browser auth flow completes successfully.
Antigravity stays on Sign into Google page and does not become logged in.
Expected result:
After successful browser auth, Antigravity should receive callback and complete sign-in.
A/B tests performed:
Rewrite ON + Enhanced ON: failed
Rewrite OFF + Enhanced ON: failed
Rewrite OFF + Enhanced OFF + System Proxy ON: failed
Rewrite OFF + Enhanced ON + System Proxy ON: failed
Additional observations:
Surge shows high google rule hits, indicating outbound proxy path is functional.
Antigravity traffic increases during attempts, so requests are being made.
Failure appears specifically at callback/session handoff into app.
Same machine/network/account succeeds with Clash, so this is unlikely to be account/basic network issue.
Suspected cause:
Compatibility issue in OAuth callback handoff (loopback/custom scheme) under Surge interception path.
Token/code return stage after browser auth may be intercepted or not correctly delivered/consumed by app.
