feat: add overlap grace period for refresh tokens to handle concurrent requests

src/config/limits.ts

@@ -6,6 +6,9 @@
     // Refresh token lifetime in milliseconds.
     // 刷新令牌有效期（毫秒）。
     refreshTokenTtlMs: 30 * 24 * 60 * 60 * 1000,
+    // Grace window for previous refresh token after rotation (ms).
+    // 刷新令牌轮换后的旧令牌宽限窗口（毫秒）。
+    refreshTokenOverlapGraceMs: 60 * 1000,
     // Refresh token random byte length.
     // 刷新令牌随机字节长度。
     refreshTokenRandomBytes: 32,

src/handlers/identity.ts

@@ -244,8 +244,12 @@ export async function handleToken(request: Request, env: Env): Promise<Response>
       return identityErrorResponse('Invalid refresh token', 'invalid_grant', 400);
     }
 
-    // Revoke old refresh token (prevent reuse)
-    await storage.deleteRefreshToken(refreshToken);
+    // Keep a short overlap window for old refresh token to absorb
+    // concurrent refresh requests from multiple client contexts.
+    await storage.constrainRefreshTokenExpiry(
+      refreshToken,
+      Date.now() + LIMITS.auth.refreshTokenOverlapGraceMs
+    );
 
     const { accessToken, user } = result;
     const newRefreshToken = await auth.generateRefreshToken(user.id);

src/services/storage.ts

@@ -643,6 +643,26 @@ export class StorageService {
     await this.db.prepare('DELETE FROM refresh_tokens WHERE token = ?').bind(tokenKey).run();
   }
 
+  // Keep a short overlap window for rotated refresh token to reduce
+  // multi-context refresh races (e.g. browser extension popup/background).
+  // Expiry is only tightened, never extended.
+  async constrainRefreshTokenExpiry(token: string, maxExpiresAtMs: number): Promise<void> {
+    const tokenKey = await this.refreshTokenKey(token);
+
+    await this.db.prepare(
+      'UPDATE refresh_tokens ' +
+      'SET expires_at = CASE WHEN expires_at > ? THEN ? ELSE expires_at END ' +
+      'WHERE token = ?'
+    ).bind(maxExpiresAtMs, maxExpiresAtMs, tokenKey).run();
+
+    // Best-effort legacy plaintext support for older rows.
+    await this.db.prepare(
+      'UPDATE refresh_tokens ' +
+      'SET expires_at = CASE WHEN expires_at > ? THEN ? ELSE expires_at END ' +
+      'WHERE token = ?'
+    ).bind(maxExpiresAtMs, maxExpiresAtMs, token).run();
+  }
+
   private async trustedTwoFactorTokenKey(token: string): Promise<string> {
     const digest = await this.sha256Hex(token);
     return `sha256:${digest}`;