diff --git a/src/gateway/server-methods/config.ts b/src/gateway/server-methods/config.ts
index 1623a148509..b4ac8c32d32 100644
--- a/src/gateway/server-methods/config.ts
+++ b/src/gateway/server-methods/config.ts
@@ -1,4 +1,5 @@
 import { resolveAgentWorkspaceDir, resolveDefaultAgentId } from "../../agents/agent-scope.js";
+import { isLoopbackHost } from "../net.js";
 import { listChannelPlugins } from "../../channels/plugins/index.js";
 import {
   CONFIG_PATH,
@@ -249,7 +250,7 @@ function loadSchemaWithPlugins(): ConfigSchemaResponse {
  * which defaults to "loopback"). Rejecting at config-write time prevents the
  * gateway from entering an unrecoverable crash loop on next restart.
  */
-function validateTailscaleBindCompat(config: OpenClawConfig): string | null {
+export function validateTailscaleBindCompat(config: OpenClawConfig): string | null {
   const tailscaleMode = config.gateway?.tailscale?.mode;
   if (tailscaleMode !== "serve" && tailscaleMode !== "funnel") {
     return null;
@@ -258,6 +259,15 @@ function validateTailscaleBindCompat(config: OpenClawConfig): string | null {
   if (bind === "loopback") {
     return null;
   }
+  // A custom bind with a loopback IP is equivalent to bind=loopback at runtime
+  // (server-runtime-config.ts uses isLoopbackHost on the resolved IP). Allow it
+  // at write-time too so we don't reject a valid config.
+  if (bind === "custom") {
+    const customBindHost = config.gateway?.customBindHost?.trim();
+    if (customBindHost && isLoopbackHost(customBindHost)) {
+      return null;
+    }
+  }
   return `gateway.tailscale.mode="${tailscaleMode}" requires gateway.bind="loopback", but gateway.bind="${bind}". Change gateway.bind to "loopback" or set gateway.tailscale.mode to "off".`;
 }