diff --git a/scripts/check-memory-fd-repro.mjs b/scripts/check-memory-fd-repro.mjs
index 1ded62ebfbf..63f28534010 100644
--- a/scripts/check-memory-fd-repro.mjs
+++ b/scripts/check-memory-fd-repro.mjs
@@ -342,7 +342,11 @@ function sampleFds({ label, pid, workspaceRealPath }) {
   return sample;
 }
 
-async function waitForGatewayReady({ child, port, logPath, timeoutMs }) {
+export function hasChildExited(child) {
+  return child.exitCode !== null || child.signalCode !== null;
+}
+
+export async function waitForGatewayReady({ child, port, logPath, timeoutMs }) {
   const startedAt = Date.now();
   let outputState = { tail: "", readySeen: false };
   const append = (chunk) => {
@@ -357,7 +361,7 @@ async function waitForGatewayReady({ child, port, logPath, timeoutMs }) {
     if (outputState.readySeen && findGatewayPid(port)) {
       return;
     }
-    if (child.exitCode !== null) {
+    if (hasChildExited(child)) {
       throw new Error(`gateway exited before ready; see ${logPath}`);
     }
     await sleep(100);
@@ -365,26 +369,41 @@ async function waitForGatewayReady({ child, port, logPath, timeoutMs }) {
   throw new Error(`gateway did not become ready within ${timeoutMs}ms; see ${logPath}`);
 }
 
-async function stopGateway({ child, port }) {
-  if (child.exitCode === null) {
+export async function stopGateway({ child, port }) {
+  return stopGatewayWithRuntime({
+    child,
+    port,
+    findGatewayPidFn: findGatewayPid,
+    killProcess: process.kill,
+  });
+}
+
+export async function stopGatewayWithRuntime({
+  child,
+  port,
+  findGatewayPidFn,
+  killProcess,
+  listenerSettleDelayMs = 500,
+}) {
+  if (!hasChildExited(child)) {
     child.kill("SIGINT");
     for (let i = 0; i < 50; i += 1) {
-      if (child.exitCode !== null) {
+      if (hasChildExited(child)) {
         break;
       }
       await sleep(100);
     }
   }
-  const listenerPid = findGatewayPid(port);
+  const listenerPid = findGatewayPidFn(port);
   if (listenerPid) {
     try {
-      process.kill(listenerPid, "SIGTERM");
+      killProcess(listenerPid, "SIGTERM");
     } catch {}
-    await sleep(500);
-    const stillListening = findGatewayPid(port);
+    await sleep(listenerSettleDelayMs);
+    const stillListening = findGatewayPidFn(port);
     if (stillListening) {
       try {
-        process.kill(stillListening, "SIGKILL");
+        killProcess(stillListening, "SIGKILL");
       } catch {}
     }
   }
diff --git a/test/scripts/check-memory-fd-repro.test.ts b/test/scripts/check-memory-fd-repro.test.ts
index 94125c6576b..42da1c104f7 100644
--- a/test/scripts/check-memory-fd-repro.test.ts
+++ b/test/scripts/check-memory-fd-repro.test.ts
@@ -1,10 +1,50 @@
-import { describe, expect, it } from "vitest";
+import { EventEmitter } from "node:events";
+import { describe, expect, it, vi } from "vitest";
 import {
   GATEWAY_READY_OUTPUT_MAX_CHARS,
+  hasChildExited,
+  stopGatewayWithRuntime,
   updateGatewayReadyOutputState,
+  waitForGatewayReady,
 } from "../../scripts/check-memory-fd-repro.mjs";
 
 describe("check-memory-fd-repro", () => {
+  it("treats signaled gateway children as exited", () => {
+    expect(hasChildExited({ exitCode: null, signalCode: "SIGTERM" })).toBe(true);
+    expect(hasChildExited({ exitCode: 0, signalCode: null })).toBe(true);
+    expect(hasChildExited({ exitCode: null, signalCode: null })).toBe(false);
+  });
+
+  it("fails gateway readiness immediately after signal exits", async () => {
+    const child = {
+      exitCode: null,
+      signalCode: "SIGTERM",
+      stderr: new EventEmitter(),
+      stdout: new EventEmitter(),
+    };
+
+    await expect(
+      waitForGatewayReady({ child, port: 9, logPath: "gateway.log", timeoutMs: 10_000 }),
+    ).rejects.toThrow("gateway exited before ready");
+  });
+
+  it("does not signal already exited children during gateway cleanup", async () => {
+    const child = {
+      exitCode: null,
+      kill: vi.fn(),
+      signalCode: "SIGTERM",
+    };
+    const findGatewayPidFn = vi.fn(() => null);
+    const killProcess = vi.fn();
+
+    await expect(
+      stopGatewayWithRuntime({ child, findGatewayPidFn, killProcess, port: 9 }),
+    ).resolves.toBeUndefined();
+    expect(child.kill).not.toHaveBeenCalled();
+    expect(findGatewayPidFn).toHaveBeenCalledWith(9);
+    expect(killProcess).not.toHaveBeenCalled();
+  });
+
   it("bounds gateway readiness output while keeping newest logs", () => {
     const first = updateGatewayReadyOutputState({ tail: "abc", readySeen: false }, "def", 8);
     expect(first).toEqual({ tail: "abcdef", readySeen: false });
@@ -39,11 +79,7 @@ describe("check-memory-fd-repro", () => {
   });
 
   it("preserves previous readiness once seen", () => {
-    const state = updateGatewayReadyOutputState(
-      { tail: "old", readySeen: true },
-      "new output",
-      8,
-    );
+    const state = updateGatewayReadyOutputState({ tail: "old", readySeen: true }, "new output", 8);
 
     expect(state.readySeen).toBe(true);
     expect(state.tail).toBe("w output");