diff --git a/scripts/lib/cross-os-release-checks/installed.ts b/scripts/lib/cross-os-release-checks/installed.ts
index 2a698e3b95ea..0aad70888c55 100644
--- a/scripts/lib/cross-os-release-checks/installed.ts
+++ b/scripts/lib/cross-os-release-checks/installed.ts
@@ -420,8 +420,9 @@ export async function runOnboardWithInstalledCli(params: {
   providerConfig: ProviderConfig;
   installDaemon: boolean;
   logPath: string;
+  allocateGatewayPort?: boolean;
 }) {
-  await withAllocatedGatewayPort(params.lane, async () => {
+  const runOnboard = async () => {
     const args = buildReleaseOnboardArgs({
       authChoice: params.providerConfig.authChoice,
       gatewayPort: params.lane.gatewayPort,
@@ -436,7 +437,15 @@ export async function runOnboardWithInstalledCli(params: {
       logPath: params.logPath,
       timeoutMs: 10 * 60 * 1000,
     });
-  });
+  };
+  if (params.allocateGatewayPort === false) {
+    if (params.lane.gatewayPort <= 0) {
+      throw new Error("Installed onboarding requires a reserved gateway port.");
+    }
+    await runOnboard();
+    return;
+  }
+  await withAllocatedGatewayPort(params.lane, runOnboard);
 }
 
 export function buildReleaseOnboardArgs(params: {
diff --git a/scripts/lib/cross-os-release-checks/lanes.ts b/scripts/lib/cross-os-release-checks/lanes.ts
index a9b600fc7550..95d76cb9a24f 100644
--- a/scripts/lib/cross-os-release-checks/lanes.ts
+++ b/scripts/lib/cross-os-release-checks/lanes.ts
@@ -59,7 +59,12 @@ import {
   waitForInstalledGatewayToStop,
 } from "./installed.ts";
 import { maybeRunDiscordRoundtrip } from "./network-smokes.ts";
-import { runCleanup, startStaticFileServer, stopGateway } from "./process.ts";
+import {
+  reserveGatewayPortForLane,
+  runCleanup,
+  startStaticFileServer,
+  stopGateway,
+} from "./process.ts";
 import { logLanePhase, runTimedLanePhase } from "./reporting.ts";
 import {
   exerciseManagedGatewayLifecycle,
@@ -432,6 +437,15 @@ export async function runInstallerFreshSuite(
       });
     }
 
+    // Hold the configured port through onboarding and model setup so another runner process
+    // cannot claim it before the manual gateway starts. Release immediately before spawn.
+    const gatewayPortReservation = usesManagedGateway
+      ? null
+      : await reserveGatewayPortForLane(lane);
+    if (gatewayPortReservation) {
+      cleanup.push(() => gatewayPortReservation.release());
+    }
+
     logLanePhase(lane, "onboard");
     await runOnboardWithInstalledCli({
       lane,
@@ -440,6 +454,7 @@ export async function runInstallerFreshSuite(
       providerConfig: params.providerConfig,
       installDaemon: usesManagedGateway,
       logPath: join(params.logsDir, "installer-fresh-onboard.log"),
+      allocateGatewayPort: gatewayPortReservation === null,
     });
 
     if (shouldExerciseManagedGatewayLifecycleAfterInstall()) {
@@ -483,6 +498,7 @@ export async function runInstallerFreshSuite(
           logPath: join(params.logsDir, "installer-fresh-gateway-stop-managed-status.log"),
         });
       }
+      await gatewayPortReservation?.release();
       logLanePhase(lane, "gateway-start");
       const gateway = await startManualGatewayFromInstalledCli({
         lane,
diff --git a/scripts/lib/cross-os-release-checks/process.ts b/scripts/lib/cross-os-release-checks/process.ts
index f2b39dad104b..4f4b7465c0fb 100644
--- a/scripts/lib/cross-os-release-checks/process.ts
+++ b/scripts/lib/cross-os-release-checks/process.ts
@@ -593,6 +593,22 @@ export async function withAllocatedGatewayPort<T>(lane: LaneState, callback: ()
   );
 }
 
+export async function reserveGatewayPortForLane(lane: LaneState) {
+  const reservation = await reservePort();
+  lane.gatewayPort = reservation.port;
+  let released = false;
+  return {
+    port: reservation.port,
+    release: async () => {
+      if (released) {
+        return;
+      }
+      released = true;
+      await reservation.release();
+    },
+  };
+}
+
 function reservePort(): Promise<{ port: number; release: () => Promise<void> }> {
   return new Promise((resolvePromise, rejectPromise) => {
     const server = createNetServer();
diff --git a/test/scripts/openclaw-cross-os-release-checks.test.ts b/test/scripts/openclaw-cross-os-release-checks.test.ts
index ae875e1dba14..e8c9af988a53 100644
--- a/test/scripts/openclaw-cross-os-release-checks.test.ts
+++ b/test/scripts/openclaw-cross-os-release-checks.test.ts
@@ -69,6 +69,7 @@ import {
   readInstalledVersion,
   readBoundedCrossOsResponseText,
   readRunnerOverrideEnv,
+  reserveGatewayPortForLane,
   resolveDashboardAssetUrls,
   resolveCrossOsAgentTurnOptional,
   runCommand,
@@ -1794,6 +1795,19 @@ describe("scripts/openclaw-cross-os-release-checks", () => {
     expect(await canConnectToLoopbackPort(port, 100)).toBe(false);
   });
 
+  it("keeps a release gateway port reserved until the lane is ready to start", async () => {
+    const lane = { gatewayPort: 0 } as Parameters<typeof reserveGatewayPortForLane>[0];
+    const reservation = await reserveGatewayPortForLane(lane);
+    try {
+      expect(lane.gatewayPort).toBe(reservation.port);
+      expect(await canConnectToLoopbackPort(reservation.port)).toBe(true);
+    } finally {
+      await reservation.release();
+    }
+    await reservation.release();
+    expect(await canConnectToLoopbackPort(reservation.port, 100)).toBe(false);
+  });
+
   it("writes Discord smoke config using the strict guild channel schema", () => {
     expect(buildDiscordSmokeGuildsConfig("guild-123", "channel-456")).toEqual({
       "guild-123": {