diff --git a/scripts/check-cli-startup-memory.mjs b/scripts/check-cli-startup-memory.mjs
index 3520bd0dff7..97267f6ae2c 100644
--- a/scripts/check-cli-startup-memory.mjs
+++ b/scripts/check-cli-startup-memory.mjs
@@ -20,7 +20,7 @@ let rssHookPath = null;
 
 function readPositiveIntEnv(name, fallback, env = process.env) {
   const value = readPositiveNumberEnv(name, fallback, env);
-  if (!Number.isInteger(value)) {
+  if (!Number.isSafeInteger(value)) {
     throw new Error(`${name} must be a positive integer`);
   }
   return value;
diff --git a/test/scripts/check-cli-startup-memory.test.ts b/test/scripts/check-cli-startup-memory.test.ts
index 8ea07c4e07c..81e0e7972f8 100644
--- a/test/scripts/check-cli-startup-memory.test.ts
+++ b/test/scripts/check-cli-startup-memory.test.ts
@@ -86,6 +86,11 @@ describe("check-cli-startup-memory", () => {
         OPENCLAW_STARTUP_MEMORY_TIMEOUT_MS: "1000.5",
       }),
     ).toThrow("OPENCLAW_STARTUP_MEMORY_TIMEOUT_MS must be a positive integer");
+    expect(() =>
+      testing.readPositiveIntEnv("OPENCLAW_STARTUP_MEMORY_TIMEOUT_MS", 60_000, {
+        OPENCLAW_STARTUP_MEMORY_TIMEOUT_MS: String(Number.MAX_SAFE_INTEGER + 1),
+      }),
+    ).toThrow("OPENCLAW_STARTUP_MEMORY_TIMEOUT_MS must be a positive integer");
     expect(
       testing.readPositiveIntEnv("OPENCLAW_STARTUP_MEMORY_TIMEOUT_MS", 60_000, {
         OPENCLAW_STARTUP_MEMORY_TIMEOUT_MS: "1000",