diff --git a/src/gateway/probe.test.ts b/src/gateway/probe.test.ts
index 4a2374e17cb..01c69be5199 100644
--- a/src/gateway/probe.test.ts
+++ b/src/gateway/probe.test.ts
@@ -40,9 +40,15 @@ vi.mock("./client.js", () => ({
   GatewayClient: MockGatewayClient,
 }));
 
-const { probeGateway } = await import("./probe.js");
+const { clampProbeTimeoutMs, probeGateway } = await import("./probe.js");
 
 describe("probeGateway", () => {
+  it("clamps probe timeout to timer-safe bounds", () => {
+    expect(clampProbeTimeoutMs(1)).toBe(250);
+    expect(clampProbeTimeoutMs(2_000)).toBe(2_000);
+    expect(clampProbeTimeoutMs(3_000_000_000)).toBe(2_147_483_647);
+  });
+
   it("connects with operator.read scope", async () => {
     const result = await probeGateway({
       url: "ws://127.0.0.1:18789",
diff --git a/src/gateway/probe.ts b/src/gateway/probe.ts
index bbd36639b78..b285c395c3d 100644
--- a/src/gateway/probe.ts
+++ b/src/gateway/probe.ts
@@ -29,6 +29,13 @@ export type GatewayProbeResult = {
   configSnapshot: unknown;
 };
 
+export const MIN_PROBE_TIMEOUT_MS = 250;
+export const MAX_TIMER_DELAY_MS = 2_147_483_647;
+
+export function clampProbeTimeoutMs(timeoutMs: number): number {
+  return Math.min(MAX_TIMER_DELAY_MS, Math.max(MIN_PROBE_TIMEOUT_MS, timeoutMs));
+}
+
 export async function probeGateway(opts: {
   url: string;
   auth?: GatewayProbeAuth;
@@ -144,21 +151,18 @@ export async function probeGateway(opts: {
       },
     });
 
-    const timer = setTimeout(
-      () => {
-        settle({
-          ok: false,
-          connectLatencyMs,
-          error: connectError ? `connect failed: ${connectError}` : "timeout",
-          close,
-          health: null,
-          status: null,
-          presence: null,
-          configSnapshot: null,
-        });
-      },
-      Math.max(250, opts.timeoutMs),
-    );
+    const timer = setTimeout(() => {
+      settle({
+        ok: false,
+        connectLatencyMs,
+        error: connectError ? `connect failed: ${connectError}` : "timeout",
+        close,
+        health: null,
+        status: null,
+        presence: null,
+        configSnapshot: null,
+      });
+    }, clampProbeTimeoutMs(opts.timeoutMs));
 
     client.start();
   });