diff --git a/scripts/e2e/lib/gateway-network/client.mjs b/scripts/e2e/lib/gateway-network/client.mjs
index ecfb48516434..0ff784dd063b 100644
--- a/scripts/e2e/lib/gateway-network/client.mjs
+++ b/scripts/e2e/lib/gateway-network/client.mjs
@@ -2,6 +2,7 @@ import { WebSocket } from "ws";
 import { PROTOCOL_VERSION } from "../../../../dist/gateway/protocol/index.js";
 import { waitForWebSocketOpen } from "../websocket-open.mjs";
 import { readGatewayNetworkClientConnectTimeoutMs } from "./limits.mjs";
+import { onceFrame } from "./ws-frames.mjs";
 
 const url = process.env.GW_URL;
 const token = process.env.GW_TOKEN;
@@ -23,25 +24,6 @@ async function openSocket(timeoutMs = 10_000) {
   return ws;
 }
 
-function onceFrame(ws, filter, timeoutMs = 10_000) {
-  return new Promise((resolve, reject) => {
-    const timer = setTimeout(() => {
-      ws.off("message", handler);
-      reject(new Error("timeout"));
-    }, timeoutMs);
-    const handler = (data) => {
-      const obj = JSON.parse(String(data));
-      if (!filter(obj)) {
-        return;
-      }
-      clearTimeout(timer);
-      ws.off("message", handler);
-      resolve(obj);
-    };
-    ws.on("message", handler);
-  });
-}
-
 function responseError(method, response) {
   const message = response.error?.message ?? "unknown";
   return new Error(`${method} failed: ${message}`);
@@ -50,6 +32,7 @@ function responseError(method, response) {
 function isRetryableStartupError(message) {
   return (
     message.includes("gateway starting") ||
+    message.includes("closed before frame") ||
     message.includes("closed before open") ||
     message.includes("ws open timeout") ||
     message.includes("ECONNREFUSED") ||
diff --git a/scripts/e2e/lib/gateway-network/ws-frames.mjs b/scripts/e2e/lib/gateway-network/ws-frames.mjs
new file mode 100644
index 000000000000..95c6b579f85f
--- /dev/null
+++ b/scripts/e2e/lib/gateway-network/ws-frames.mjs
@@ -0,0 +1,66 @@
+function formatCloseValue(value) {
+  if (value === undefined || value === null) {
+    return "";
+  }
+  if (typeof value === "string") {
+    return value;
+  }
+  if (typeof value === "number" || typeof value === "boolean" || typeof value === "bigint") {
+    return value.toString();
+  }
+  if (value instanceof Uint8Array) {
+    return Buffer.from(value).toString();
+  }
+  return JSON.stringify(value) ?? "";
+}
+
+export function onceFrame(ws, filter, timeoutMs = 10_000) {
+  return new Promise((resolve, reject) => {
+    let settled = false;
+
+    const cleanup = () => {
+      clearTimeout(timer);
+      ws.off?.("message", onMessage);
+      ws.off?.("error", onError);
+      ws.off?.("close", onClose);
+    };
+    const settle = (fn, value) => {
+      if (settled) {
+        return;
+      }
+      settled = true;
+      cleanup();
+      fn(value);
+    };
+    const onMessage = (data) => {
+      let obj;
+      try {
+        obj = JSON.parse(String(data));
+        if (!filter(obj)) {
+          return;
+        }
+      } catch (error) {
+        settle(reject, error instanceof Error ? error : new Error(String(error)));
+        return;
+      }
+      settle(resolve, obj);
+    };
+    const onError = (error) =>
+      settle(reject, error instanceof Error ? error : new Error(String(error)));
+    const onClose = (code, reason) => {
+      const closeDetails = [formatCloseValue(code), formatCloseValue(reason)]
+        .filter(Boolean)
+        .join(" ");
+      const suffix = closeDetails ? `: ${closeDetails}` : "";
+      settle(reject, new Error(`closed before frame${suffix}`));
+    };
+    const timer = setTimeout(() => {
+      settle(reject, new Error("timeout"));
+    }, timeoutMs);
+    timer.unref?.();
+
+    ws.on("message", onMessage);
+    ws.once("error", onError);
+    ws.once("close", onClose);
+  });
+}
diff --git a/test/scripts/gateway-network-client.test.ts b/test/scripts/gateway-network-client.test.ts
index 3810ceb30bb8..81e414a0d8ce 100644
--- a/test/scripts/gateway-network-client.test.ts
+++ b/test/scripts/gateway-network-client.test.ts
@@ -1,6 +1,8 @@
+import { EventEmitter } from "node:events";
 import { readFileSync } from "node:fs";
 import { describe, expect, it } from "vitest";
 import { readGatewayNetworkClientConnectTimeoutMs } from "../../scripts/e2e/lib/gateway-network/limits.mjs";
+import { onceFrame } from "../../scripts/e2e/lib/gateway-network/ws-frames.mjs";
 
 describe("gateway network WebSocket open guard", () => {
   it("rejects loose client timeout env values instead of parsing prefixes", () => {
@@ -35,6 +37,54 @@ describe("gateway network WebSocket open guard", () => {
     ).toBe(3000);
   });
 
+  it("resolves matching frames and ignores unrelated frames", async () => {
+    const ws = new EventEmitter();
+    const frame = onceFrame(ws, (message) => message?.id === "target", 1000);
+
+    ws.emit("message", JSON.stringify({ id: "noise" }));
+    ws.emit("message", JSON.stringify({ id: "target", ok: true }));
+
+    await expect(frame).resolves.toEqual({ id: "target", ok: true });
+  });
+
+  it("times out when no matching frame arrives", async () => {
+    const ws = new EventEmitter();
+    const frame = onceFrame(ws, () => false, 10);
+
+    ws.emit("message", JSON.stringify({ id: "noise" }));
+
+    await expect(frame).rejects.toThrow("timeout");
+  });
+
+  it("rejects frame waits immediately when the socket closes", async () => {
+    const ws = new EventEmitter();
+    const startedAt = Date.now();
+    const frame = onceFrame(ws, () => false, 1000);
+
+    ws.emit("close", 1006, Buffer.from("bye"));
+
+    await expect(frame).rejects.toThrow("closed before frame: 1006 bye");
+    expect(Date.now() - startedAt).toBeLessThan(250);
+  });
+
+  it("rejects frame waits immediately on socket errors", async () => {
+    const ws = new EventEmitter();
+    const frame = onceFrame(ws, () => false, 1000);
+
+    ws.emit("error", new Error("socket exploded"));
+
+    await expect(frame).rejects.toThrow("socket exploded");
+  });
+
+  it("rejects invalid JSON frames instead of crashing the process", async () => {
+    const ws = new EventEmitter();
+    const frame = onceFrame(ws, () => false, 1000);
+
+    ws.emit("message", "{nope");
+
+    await expect(frame).rejects.toThrow();
+  });
+
   it("proves health after the authenticated connect handshake", () => {
     const client = readFileSync("scripts/e2e/lib/gateway-network/client.mjs", "utf8");
     const connectIndex = client.indexOf('method: "connect"');
@@ -44,5 +94,6 @@ describe("gateway network WebSocket open guard", () => {
     expect(healthIndex).toBeGreaterThan(connectIndex);
     expect(client).toContain('responseError("health", healthRes)');
     expect(client).toContain('message.includes("closed before open")');
+    expect(client).toContain('message.includes("closed before frame")');
   });
 });