diff --git a/src/agents/sandbox/config.test.ts b/src/agents/sandbox/config.test.ts
new file mode 100644
index 00000000000..0810808dd8f
--- /dev/null
+++ b/src/agents/sandbox/config.test.ts
@@ -0,0 +1,24 @@
+import { describe, expect, it } from "vitest";
+import type { OpenClawConfig } from "../../config/config.js";
+import { MAX_TIMER_TIMEOUT_MS } from "../../shared/number-coercion.js";
+import { resolveSandboxConfigForAgent } from "./config.js";
+
+describe("sandbox config", () => {
+  it("caps browser autostart timeout to a timer-safe delay", () => {
+    const cfg: OpenClawConfig = {
+      agents: {
+        defaults: {
+          sandbox: {
+            browser: {
+              autoStartTimeoutMs: Number.MAX_SAFE_INTEGER,
+            },
+          },
+        },
+      },
+    };
+
+    expect(resolveSandboxConfigForAgent(cfg, "main").browser.autoStartTimeoutMs).toBe(
+      MAX_TIMER_TIMEOUT_MS,
+    );
+  });
+});
diff --git a/src/agents/sandbox/config.ts b/src/agents/sandbox/config.ts
index d8688a801ff..7556afea7a0 100644
--- a/src/agents/sandbox/config.ts
+++ b/src/agents/sandbox/config.ts
@@ -1,6 +1,7 @@
 import type { OpenClawConfig } from "../../config/types.openclaw.js";
 import type { SandboxSshSettings } from "../../config/types.sandbox.js";
 import { normalizeSecretInputString } from "../../config/types.secrets.js";
+import { resolveTimerTimeoutMs } from "../../shared/number-coercion.js";
 import { normalizeOptionalString } from "../../shared/string-coerce.js";
 import { resolveAgentConfig } from "../agent-scope.js";
 import {
@@ -40,6 +41,10 @@ const DEFAULT_SANDBOX_SSH_WORKSPACE_ROOT = "/tmp/openclaw-sandboxes";
 type DangerousSandboxDockerBooleanKey = (typeof DANGEROUS_SANDBOX_DOCKER_BOOLEAN_KEYS)[number];
 type DangerousSandboxDockerBooleans = Pick<SandboxDockerConfig, DangerousSandboxDockerBooleanKey>;
 
+function resolveSandboxBrowserAutoStartTimeoutMs(value: number | undefined): number {
+  return resolveTimerTimeoutMs(value, DEFAULT_SANDBOX_BROWSER_AUTOSTART_TIMEOUT_MS);
+}
+
 function resolveDangerousSandboxDockerBooleans(
   agentDocker?: Partial<SandboxDockerConfig>,
   globalDocker?: Partial<SandboxDockerConfig>,
@@ -154,10 +159,9 @@ export function resolveSandboxBrowserConfig(params: {
     enableNoVnc: agentBrowser?.enableNoVnc ?? globalBrowser?.enableNoVnc ?? true,
     allowHostControl: agentBrowser?.allowHostControl ?? globalBrowser?.allowHostControl ?? false,
     autoStart: agentBrowser?.autoStart ?? globalBrowser?.autoStart ?? true,
-    autoStartTimeoutMs:
-      agentBrowser?.autoStartTimeoutMs ??
-      globalBrowser?.autoStartTimeoutMs ??
-      DEFAULT_SANDBOX_BROWSER_AUTOSTART_TIMEOUT_MS,
+    autoStartTimeoutMs: resolveSandboxBrowserAutoStartTimeoutMs(
+      agentBrowser?.autoStartTimeoutMs ?? globalBrowser?.autoStartTimeoutMs,
+    ),
     binds: bindsConfigured ? binds : undefined,
   };
 }