diff --git a/src/lib/onboard.ts b/src/lib/onboard.ts
index 18522211bf..8cf0295750 100644
--- a/src/lib/onboard.ts
+++ b/src/lib/onboard.ts
@@ -596,6 +596,7 @@ import { createPolicySelectionPromptHelpers } from "./onboard/policy-selection-p
 import {
   printLowMemoryWarning,
   printMessagingProviderMissing,
+  printPortUnavailableError,
   printSwapCreationFailed,
 } from "./onboard/preflight-messages";
 import { shouldSkipPreRecreateBackup } from "./onboard/sandbox-backup-on-recreate";
@@ -1649,7 +1650,7 @@ async function preflight(
         else if (outcome.kind !== "not-openshell") continue;
       }
       console.error("");
-      console.error(`  !! Port ${port} is not available.`);
+      printPortUnavailableError(port);
       console.error(`     ${label} needs this port.`);
       console.error("");
       if (portCheck.process && portCheck.process !== "unknown") {
diff --git a/src/lib/onboard/gateway-reuse.test.ts b/src/lib/onboard/gateway-reuse.test.ts
new file mode 100644
index 0000000000..aae0b86912
--- /dev/null
+++ b/src/lib/onboard/gateway-reuse.test.ts
@@ -0,0 +1,25 @@
+// SPDX-FileCopyrightText: Copyright (c) 2026 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+// SPDX-License-Identifier: Apache-2.0
+
+import { describe, expect, it, vi } from "vitest";
+
+import { createGatewayReuseHelpers } from "./gateway-reuse";
+
+describe("gateway reuse inspection", () => {
+  it("bounds every OpenShell metadata probe so a foreign listener cannot stall preflight (#6752)", () => {
+    const runCaptureOpenshell = vi.fn((_args: string[], _options?: Record<string, unknown>) => "");
+    const helpers = createGatewayReuseHelpers({
+      gatewayName: "nemoclaw",
+      runCaptureOpenshell,
+      runOpenshell: vi.fn(() => ({ status: 0 })),
+      cliDisplayName: () => "NemoClaw",
+    });
+
+    helpers.getGatewayReuseSnapshot();
+
+    expect(runCaptureOpenshell).toHaveBeenCalledTimes(3);
+    for (const [, options] of runCaptureOpenshell.mock.calls) {
+      expect(options).toMatchObject({ ignoreError: true, timeout: 5_000 });
+    }
+  });
+});
diff --git a/src/lib/onboard/gateway-reuse.ts b/src/lib/onboard/gateway-reuse.ts
index 8dd41c8522..3c73115ad6 100644
--- a/src/lib/onboard/gateway-reuse.ts
+++ b/src/lib/onboard/gateway-reuse.ts
@@ -3,6 +3,8 @@
 
 import { getGatewayReuseState, shouldSelectNamedGatewayForReuse } from "../state/gateway";
 
+const GATEWAY_INSPECTION_TIMEOUT_MS = 5_000;
+
 export type GatewayReuseSnapshot = {
   gatewayStatus: string;
   gwInfo: string;
@@ -28,11 +30,18 @@ export function createGatewayReuseHelpers(deps: GatewayReuseDeps): GatewayReuseH
 
   function getGatewayReuseSnapshot(): GatewayReuseSnapshot {
     const gatewayName = currentGatewayName();
-    const gatewayStatus = deps.runCaptureOpenshell(["status"], { ignoreError: true });
+    const gatewayStatus = deps.runCaptureOpenshell(["status"], {
+      ignoreError: true,
+      timeout: GATEWAY_INSPECTION_TIMEOUT_MS,
+    });
     const gwInfo = deps.runCaptureOpenshell(["gateway", "info", "-g", gatewayName], {
       ignoreError: true,
+      timeout: GATEWAY_INSPECTION_TIMEOUT_MS,
+    });
+    const activeGatewayInfo = deps.runCaptureOpenshell(["gateway", "info"], {
+      ignoreError: true,
+      timeout: GATEWAY_INSPECTION_TIMEOUT_MS,
     });
-    const activeGatewayInfo = deps.runCaptureOpenshell(["gateway", "info"], { ignoreError: true });
     return {
       gatewayStatus,
       gwInfo,
diff --git a/src/lib/onboard/preflight-messages.test.ts b/src/lib/onboard/preflight-messages.test.ts
index f416401cee..f9d50e0a81 100644
--- a/src/lib/onboard/preflight-messages.test.ts
+++ b/src/lib/onboard/preflight-messages.test.ts
@@ -7,6 +7,7 @@ import {
   printDockerNotReachableError,
   printLowMemoryWarning,
   printMessagingProviderMissing,
+  printPortUnavailableError,
   printSwapCreationFailed,
   printUnderProvisionedRuntimeWarning,
   printUnsupportedRuntimeError,
@@ -65,6 +66,14 @@ describe("onboard preflight severity messages (#6004)", () => {
     });
   });
 
+  it("renders port conflicts as failures without ANSI on plain stderr (#6752)", () => {
+    withStderrColorDepth(1, () => {
+      const err = vi.spyOn(console, "error").mockImplementation(() => undefined);
+      printPortUnavailableError(8080);
+      expect(lines(err)).toEqual(["  ✗ Port 8080 is not available."]);
+    });
+  });
+
   it("prints the unsupported-runtime failure to stderr with a ✗ marker", () => {
     const err = vi.spyOn(console, "error").mockImplementation(() => undefined);
     printUnsupportedRuntimeError();
diff --git a/src/lib/onboard/preflight-messages.ts b/src/lib/onboard/preflight-messages.ts
index a8dff7330b..16a052070b 100644
--- a/src/lib/onboard/preflight-messages.ts
+++ b/src/lib/onboard/preflight-messages.ts
@@ -20,6 +20,11 @@ export function printDockerNotReachableError(): void {
   console.error(failLine("Docker is not reachable. Please fix Docker and try again."));
 }
 
+/** A required onboarding port is already occupied. */
+export function printPortUnavailableError(port: number): void {
+  console.error(failLine(`Port ${port} is not available.`));
+}
+
 /** Podman under the Linux Docker-driver path is unsupported. */
 export function printUnsupportedRuntimeError(): void {
   console.error(failLine(`${cliDisplayName()} onboarding now uses OpenShell's Docker driver.`));