fix: prefer loopback for auto bind fallback

apps/macos/Sources/Clawdbot/GatewayConnection.swift

@@ -148,6 +148,27 @@ actor GatewayConnection {
                     }
                 }
 
+                let nsError = lastError as NSError
+                if nsError.domain == URLError.errorDomain,
+                   let fallback = await GatewayEndpointStore.shared.maybeFallbackToTailnet(from: cfg.url)
+                {
+                    await self.configure(url: fallback.url, token: fallback.token, password: fallback.password)
+                    for delayMs in [150, 400, 900] {
+                        try await Task.sleep(nanoseconds: UInt64(delayMs) * 1_000_000)
+                        do {
+                            guard let client = self.client else {
+                                throw NSError(
+                                    domain: "Gateway",
+                                    code: 0,
+                                    userInfo: [NSLocalizedDescriptionKey: "gateway not configured"])
+                            }
+                            return try await client.request(method: method, params: params, timeoutMs: timeoutMs)
+                        } catch {
+                            lastError = error
+                        }
+                    }
+                }
+
                 throw lastError
             case .remote:
                 let nsError = error as NSError

apps/macos/Sources/Clawdbot/GatewayEndpointStore.swift

@@ -469,6 +469,35 @@ actor GatewayEndpointStore {
         }
     }
 
+    func maybeFallbackToTailnet(from currentURL: URL) async -> GatewayConnection.Config? {
+        let mode = await self.deps.mode()
+        guard mode == .local else { return nil }
+
+        let root = ClawdbotConfigFile.loadDict()
+        let bind = GatewayEndpointStore.resolveGatewayBindMode(
+            root: root,
+            env: ProcessInfo.processInfo.environment)
+        guard bind == "auto" else { return nil }
+
+        let currentHost = currentURL.host?.lowercased() ?? ""
+        guard currentHost == "127.0.0.1" || currentHost == "localhost" else { return nil }
+
+        let tailscaleIP = await MainActor.run { TailscaleService.shared.tailscaleIP }
+        guard let tailscaleIP, !tailscaleIP.isEmpty else { return nil }
+
+        let scheme = GatewayEndpointStore.resolveGatewayScheme(
+            root: root,
+            env: ProcessInfo.processInfo.environment)
+        let port = self.deps.localPort()
+        let token = self.deps.token()
+        let password = self.deps.password()
+        let url = URL(string: "\(scheme)://\(tailscaleIP):\(port)")!
+
+        self.logger.info("auto bind fallback to tailnet host=\(tailscaleIP, privacy: .public)")
+        self.setState(.ready(mode: .local, url: url, token: token, password: password))
+        return (url, token, password)
+    }
+
     private static func resolveGatewayBindMode(
         root: [String: Any],
         env: [String: String]) -> String?
@@ -524,8 +553,10 @@ actor GatewayEndpointStore {
         tailscaleIP: String?) -> String
     {
         switch bindMode {
-        case "tailnet", "auto":
+        case "tailnet":
             tailscaleIP ?? "127.0.0.1"
+        case "auto":
+            "127.0.0.1"
         case "custom":
             customBindHost ?? "127.0.0.1"
         default: