diff --git a/extensions/codex/src/app-server/native-hook-relay.test.ts b/extensions/codex/src/app-server/native-hook-relay.test.ts
index d3985ae2352..a4f2b953425 100644
--- a/extensions/codex/src/app-server/native-hook-relay.test.ts
+++ b/extensions/codex/src/app-server/native-hook-relay.test.ts
@@ -1,8 +1,10 @@
 import type { NativeHookRelayRegistrationHandle } from "openclaw/plugin-sdk/agent-harness-runtime";
+import { MAX_TIMER_TIMEOUT_MS } from "openclaw/plugin-sdk/number-runtime";
 import { describe, expect, it } from "vitest";
 import {
   buildCodexNativeHookRelayConfig,
   buildCodexNativeHookRelayDisabledConfig,
+  resolveCodexNativeHookRelayUnregisterGraceMs,
 } from "./native-hook-relay.js";
 
 describe("Codex native hook relay config", () => {
@@ -251,6 +253,12 @@ describe("Codex native hook relay config", () => {
       "hooks.Stop": [],
     });
   });
+
+  it("caps oversized native hook cleanup grace before scheduling", () => {
+    expect(resolveCodexNativeHookRelayUnregisterGraceMs(Number.MAX_SAFE_INTEGER)).toBe(
+      MAX_TIMER_TIMEOUT_MS,
+    );
+  });
 });
 
 function createRelay(options?: {
diff --git a/extensions/codex/src/app-server/native-hook-relay.ts b/extensions/codex/src/app-server/native-hook-relay.ts
index a0d3b939c1b..1f10d095659 100644
--- a/extensions/codex/src/app-server/native-hook-relay.ts
+++ b/extensions/codex/src/app-server/native-hook-relay.ts
@@ -5,6 +5,10 @@ import {
   type NativeHookRelayEvent,
   type NativeHookRelayRegistrationHandle,
 } from "openclaw/plugin-sdk/agent-harness-runtime";
+import {
+  addTimerTimeoutGraceMs,
+  finiteSecondsToTimerSafeMilliseconds,
+} from "openclaw/plugin-sdk/number-runtime";
 import type { CodexAppServerRuntimeOptions } from "./config.js";
 import type { JsonObject, JsonValue } from "./protocol.js";
 
@@ -61,11 +65,11 @@ export function resolveCodexNativeHookRelayUnregisterGraceMs(
 ): number {
   const hookTimeoutMs =
     typeof hookTimeoutSec === "number" && Number.isFinite(hookTimeoutSec) && hookTimeoutSec > 0
-      ? Math.ceil(hookTimeoutSec) * 1000
+      ? (finiteSecondsToTimerSafeMilliseconds(Math.ceil(hookTimeoutSec)) ?? 0)
       : 0;
   return Math.max(
     CODEX_NATIVE_HOOK_RELAY_UNREGISTER_GRACE_MS,
-    hookTimeoutMs + CODEX_NATIVE_HOOK_RELAY_UNREGISTER_EXTRA_GRACE_MS,
+    addTimerTimeoutGraceMs(hookTimeoutMs, CODEX_NATIVE_HOOK_RELAY_UNREGISTER_EXTRA_GRACE_MS) ?? 0,
   );
 }