diff --git a/scripts/openclaw-cross-os-release-checks.ts b/scripts/openclaw-cross-os-release-checks.ts
index b5352a459ec..1ead13c0bcc 100644
--- a/scripts/openclaw-cross-os-release-checks.ts
+++ b/scripts/openclaw-cross-os-release-checks.ts
@@ -1759,8 +1759,7 @@ async function runInstalledAgentTurn(params) {
     logPath: params.logPath,
     timeoutMs: 10 * 60 * 1000,
   });
-  const payloadTexts = parseAgentPayloadTexts(result.stdout);
-  if (!payloadTexts.some((text) => text.trim() === "OK")) {
+  if (!agentOutputHasExpectedOkMarker(result.stdout, { logPath: params.logPath })) {
     throw new Error("Agent output did not contain the expected OK marker.");
   }
   return result;
@@ -2405,13 +2404,28 @@ async function runAgentTurn(params) {
     logPath: params.logPath,
     timeoutMs: 10 * 60 * 1000,
   });
-  const payloadTexts = parseAgentPayloadTexts(result.stdout);
-  if (!payloadTexts.some((text) => text.trim() === "OK")) {
+  if (!agentOutputHasExpectedOkMarker(result.stdout, { logPath: params.logPath })) {
     throw new Error("Agent output did not contain the expected OK marker.");
   }
   return result;
 }
 
+export function agentOutputHasExpectedOkMarker(stdout, options = {}) {
+  const payloadTexts = parseAgentPayloadTexts(stdout);
+  if (payloadTexts.some((text) => text.trim() === "OK")) {
+    return true;
+  }
+  if (typeof options.logPath !== "string") {
+    return false;
+  }
+  try {
+    const logTexts = parseAgentPayloadTexts(readFileSync(options.logPath, "utf8"));
+    return logTexts.some((text) => text.trim() === "OK");
+  } catch {
+    return false;
+  }
+}
+
 function parseAgentPayloadTexts(stdout) {
   try {
     const payload = JSON.parse(stdout);
diff --git a/test/scripts/openclaw-cross-os-release-checks.test.ts b/test/scripts/openclaw-cross-os-release-checks.test.ts
index bdeea169169..2fb0c6c5c68 100644
--- a/test/scripts/openclaw-cross-os-release-checks.test.ts
+++ b/test/scripts/openclaw-cross-os-release-checks.test.ts
@@ -5,6 +5,7 @@ import { join } from "node:path";
 import { setTimeout as delay } from "node:timers/promises";
 import { describe, expect, it } from "vitest";
 import {
+  agentOutputHasExpectedOkMarker,
   buildWindowsDevUpdateToolchainCheckScript,
   buildWindowsFreshShellVersionCheckScript,
   buildWindowsPathBootstrapScript,
@@ -37,6 +38,27 @@ import {
 } from "../../scripts/openclaw-cross-os-release-checks.ts";
 
 describe("scripts/openclaw-cross-os-release-checks", () => {
+  it("accepts OK agent output from the captured log when stdout is empty", () => {
+    const dir = mkdtempSync(join(tmpdir(), "openclaw-cross-os-agent-output-"));
+    try {
+      const logPath = join(dir, "agent.log");
+      writeFileSync(
+        logPath,
+        [
+          "2026-04-24T15:00:00.000Z command stdout",
+          JSON.stringify({
+            finalAssistantVisibleText: "OK",
+            payloads: [{ type: "text", text: "OK" }],
+          }),
+        ].join("\n"),
+      );
+
+      expect(agentOutputHasExpectedOkMarker("", { logPath })).toBe(true);
+    } finally {
+      rmSync(dir, { recursive: true, force: true });
+    }
+  });
+
   it("treats explicit empty-string args as values instead of boolean flags", () => {
     expect(parseArgs(["--ubuntu-runner", "", "--mode", "both"])).toEqual({
       "ubuntu-runner": "",