diff --git a/CHANGELOG.md b/CHANGELOG.md
index b97b251..9271677 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -3,6 +3,14 @@
 记录 OpenStats 应用的功能新增、样式调整和问题修复，按版本与日期倒序排列。
 官网、构建与发布脚本等不影响应用本身的改动不在此记录。
 
+## 未发布
+
+### 2026-09-21
+
+#### 修复
+
+- 账号登录后应用直接退出：在登录窗口里选完 GitHub、Google 或 Apple 账号，应用立即闪退，重新打开也没有登录状态。原因是系统在后台队列回调登录结果，而回调闭包带着主线程隔离，被运行时当场中止，令牌还没来得及换取和保存。现在回调改为不带隔离、收到后再回到主线程处理，并补了回归测试。
+
 ## 0.6.1 · 2026-09-18
 
 ### 2026-09-18
diff --git a/Packages/OpenStatsKit/Package.swift b/Packages/OpenStatsKit/Package.swift
index d9df347..2520883 100644
--- a/Packages/OpenStatsKit/Package.swift
+++ b/Packages/OpenStatsKit/Package.swift
@@ -30,7 +30,7 @@ let package = Package(
         .testTarget(name: "HelperSharedTests", dependencies: ["HelperShared"]),
         .testTarget(name: "UpdatesTests", dependencies: ["Updates"]),
         .testTarget(name: "AccountSyncTests", dependencies: ["AccountSync"]),
-        .testTarget(name: "OpenStatsUITests", dependencies: ["OpenStatsUI", "Metrics"]),
+        .testTarget(name: "OpenStatsUITests", dependencies: ["OpenStatsUI", "Metrics", "AccountSync"]),
         .testTarget(name: "LocalizationTests", dependencies: ["Localization"]),
     ],
     swiftLanguageModes: [.v6]
diff --git a/Packages/OpenStatsKit/Sources/OpenStatsUI/State/SyncController.swift b/Packages/OpenStatsKit/Sources/OpenStatsUI/State/SyncController.swift
index be1cec4..391f033 100644
--- a/Packages/OpenStatsKit/Sources/OpenStatsUI/State/SyncController.swift
+++ b/Packages/OpenStatsKit/Sources/OpenStatsUI/State/SyncController.swift
@@ -116,9 +116,8 @@ public final class SyncController {
         let verifier = PKCE.verifier()
         let url = client.loginURL(provider: provider, challenge: PKCE.challenge(for: verifier))
         let anchor = AnchorProvider(anchor: presentationAnchor)
-        let session = ASWebAuthenticationSession(url: url, callbackURLScheme: SyncClient.callbackScheme) { [weak self] callback, error in
-            Task { @MainActor in self?.finishSignIn(callback: callback, error: error, verifier: verifier) }
-        }
+        let session = ASWebAuthenticationSession(url: url, callbackURLScheme: SyncClient.callbackScheme,
+                                                 completionHandler: Self.completionHandler(for: self, verifier: verifier))
         session.presentationContextProvider = anchor
         // 保留浏览器里已登录的第三方账号，用户不必再输一次密码
         session.prefersEphemeralWebBrowserSession = false
@@ -132,6 +131,15 @@ public final class SyncController {
         }
     }
 
+    /// 登录结束时系统在它自己的 XPC 队列上回调，不在主线程。这个闭包必须在非隔离的上下文里创建：
+    /// 直接写在 signIn 里会继承 @MainActor 隔离，Swift 6 在闭包入口检查执行器，发现不在主线程就中止进程
+    /// （选完账号应用直接退出，令牌还没换到，重开也没有登录状态）
+    nonisolated static func completionHandler(for controller: SyncController, verifier: String) -> @Sendable (URL?, Error?) -> Void {
+        { [weak controller] callback, error in
+            Task { @MainActor in controller?.finishSignIn(callback: callback, error: error, verifier: verifier) }
+        }
+    }
+
     public func cancelSignIn() {
         authSession?.cancel()
         authSession = nil
diff --git a/Packages/OpenStatsKit/Tests/OpenStatsUITests/OpenStatsUITests.swift b/Packages/OpenStatsKit/Tests/OpenStatsUITests/OpenStatsUITests.swift
index 1f191c2..0732a9f 100644
--- a/Packages/OpenStatsKit/Tests/OpenStatsUITests/OpenStatsUITests.swift
+++ b/Packages/OpenStatsKit/Tests/OpenStatsUITests/OpenStatsUITests.swift
@@ -1,3 +1,4 @@
+import AccountSync
 import Foundation
 @testable import Metrics
 import Testing
@@ -387,3 +388,28 @@ private func isolatedDefaults() -> UserDefaults {
         #expect(ranking.ranked(limit: 2).map(\.id) == ["z", "x"])
     }
 }
+
+@MainActor
+@Suite struct SyncSignInTests {
+    /// 系统在后台的 XPC 队列上回调登录结果。回调闭包如果带着主线程隔离，Swift 6 会在入口处中止进程，
+    /// 表现为选完账号应用直接退出；这里在后台队列调用一次，能跑完并回到主线程处理就算通过
+    @Test func completionHandlerMayRunOffMainThread() async {
+        let controller = SyncController(settings: AppSettings(defaults: isolatedDefaults()), defaults: isolatedDefaults(),
+                                        tokens: MemoryTokenStore())
+        let handler = SyncController.completionHandler(for: controller, verifier: "verifier")
+        await withCheckedContinuation { (continuation: CheckedContinuation<Void, Never>) in
+            DispatchQueue.global().async {
+                handler(nil, nil)
+                continuation.resume()
+            }
+        }
+        // 没有回调地址按失败处理；处理发生在主线程的下一个任务里，稍等一下
+        for _ in 0..<100 where controller.phase == .idle {
+            try? await Task.sleep(for: .milliseconds(10))
+        }
+        guard case .failed = controller.phase else {
+            Issue.record("回调之后 phase 应为 failed，实际是 \(controller.phase)")
+            return
+        }
+    }
+}
diff --git a/server/sync/sync b/server/sync/sync
deleted file mode 100755
index 863ce25..0000000
Binary files a/server/sync/sync and /dev/null differ