diff --git a/package.json b/package.json
index 2efe64d370..c4c192713e 100644
--- a/package.json
+++ b/package.json
@@ -46,7 +46,7 @@
     "test:e2e:copy-tex": "node scripts/e2e-copy-tex.mjs",
     "test:e2e:transcript-disclosure": "node scripts/e2e-transcript-disclosure-anchor.mjs",
     "test:e2e:images": "node scripts/e2e-image-generation.mjs && node scripts/e2e-image-generation-ui.mjs && node scripts/e2e-image-chat.mjs",
-    "test:e2e:provider-client-certificate": "node scripts/e2e-provider-client-certificate.mjs",
+    "test:e2e:provider-client-certificate": "node --test scripts/e2e/wait-for-child-exit.test.mjs && node scripts/e2e-provider-client-certificate.mjs",
     "test:e2e:provider-order": "node scripts/e2e-provider-order.mjs",
     "test:e2e:project-edit": "node scripts/e2e-project-edit.mjs",
     "test:e2e:provider-api-style": "node scripts/e2e-provider-api-style.mjs",
diff --git a/scripts/e2e-provider-client-certificate.mjs b/scripts/e2e-provider-client-certificate.mjs
index 2876c74792..a0aac14957 100644
--- a/scripts/e2e-provider-client-certificate.mjs
+++ b/scripts/e2e-provider-client-certificate.mjs
@@ -8,6 +8,7 @@ import { tmpdir } from "node:os";
 import { join } from "node:path";
 import { fileURLToPath } from "node:url";
 import { resolveElectronBinary } from "./e2e/boot.mjs";
+import { waitForChildExitWithEscalation } from "./e2e/wait-for-child-exit.mjs";
 
 const root = fileURLToPath(new URL("..", import.meta.url));
 const { build } = createRequire(join(root, "packages/agent-runtime/package.json"))("esbuild");
@@ -29,13 +30,17 @@ try {
     output += chunk;
     process.stdout.write(chunk);
   });
-  const timer = setTimeout(() => child.kill(), 60_000);
-  try {
-    const code = await new Promise((resolve, reject) => {
-      child.once("error", reject);
-      child.once("close", resolve);
-    });
-    assert.equal(code, 0, output);
-    assert.match(output, /provider client certificate E2E passed/);
-  } finally { clearTimeout(timer); }
+  // A probe that cannot start must fail this step, not hold the job open.
+  // SIGTERM alone is not enough: Electron can ignore it while a renderer is
+  // mid-init, and the `close` event then never arrives, so the step waits out
+  // the job's 30-minute budget and is cancelled with no failing step to read
+  // (#1751 hit exactly this). Escalate to SIGKILL after a short grace period.
+  const { code, killedBy } = await waitForChildExitWithEscalation(child);
+  assert.equal(
+    killedBy,
+    null,
+    `provider client certificate E2E hung and was killed by ${killedBy} after ${killedBy === "SIGKILL" ? 65 : 60}s: ${output}`,
+  );
+  assert.equal(code, 0, output);
+  assert.match(output, /provider client certificate E2E passed/);
 } finally { await rm(temp, { recursive: true, force: true }); }
diff --git a/scripts/e2e/wait-for-child-exit.mjs b/scripts/e2e/wait-for-child-exit.mjs
new file mode 100644
index 0000000000..9bb26d6fc5
--- /dev/null
+++ b/scripts/e2e/wait-for-child-exit.mjs
@@ -0,0 +1,29 @@
+export async function waitForChildExitWithEscalation(
+  child,
+  {
+    termAfterMs = 60_000,
+    killAfterMs = 65_000,
+    setTimer = setTimeout,
+    clearTimer = clearTimeout,
+  } = {},
+) {
+  let killedBy = null;
+  const termTimer = setTimer(() => {
+    killedBy = "SIGTERM";
+    child.kill("SIGTERM");
+  }, termAfterMs);
+  const killTimer = setTimer(() => {
+    killedBy = "SIGKILL";
+    child.kill("SIGKILL");
+  }, killAfterMs);
+  try {
+    const code = await new Promise((resolve, reject) => {
+      child.once("error", reject);
+      child.once("close", resolve);
+    });
+    return { code, killedBy };
+  } finally {
+    clearTimer(termTimer);
+    clearTimer(killTimer);
+  }
+}
diff --git a/scripts/e2e/wait-for-child-exit.test.mjs b/scripts/e2e/wait-for-child-exit.test.mjs
new file mode 100644
index 0000000000..78ca767607
--- /dev/null
+++ b/scripts/e2e/wait-for-child-exit.test.mjs
@@ -0,0 +1,87 @@
+import assert from "node:assert/strict";
+import { EventEmitter } from "node:events";
+import test from "node:test";
+import { waitForChildExitWithEscalation } from "./wait-for-child-exit.mjs";
+
+function controlledTimers() {
+  let nextId = 0;
+  const pending = new Map();
+  return {
+    setTimer(callback, delay) {
+      const id = ++nextId;
+      pending.set(id, { callback, delay });
+      return id;
+    },
+    clearTimer(id) {
+      pending.delete(id);
+    },
+    fireAfter(delay) {
+      for (const [id, timer] of pending) {
+        if (timer.delay === delay) {
+          pending.delete(id);
+          timer.callback();
+        }
+      }
+    },
+    pending,
+  };
+}
+
+test("a normally closing child exits without signals and clears both timers", async () => {
+  const child = new EventEmitter();
+  child.kill = () => assert.fail("a normally closing child must not be killed");
+  const timers = controlledTimers();
+
+  const result = waitForChildExitWithEscalation(child, {
+    setTimer: timers.setTimer,
+    clearTimer: timers.clearTimer,
+  });
+  child.emit("close", 0);
+
+  assert.deepEqual(await result, { code: 0, killedBy: null });
+  assert.equal(timers.pending.size, 0);
+});
+
+test("a child that ignores SIGTERM receives SIGKILL after the grace period", async () => {
+  const child = new EventEmitter();
+  const signals = [];
+  child.kill = (signal) => signals.push(signal);
+  const timers = controlledTimers();
+
+  const result = waitForChildExitWithEscalation(child, {
+    termAfterMs: 60,
+    killAfterMs: 65,
+    setTimer: timers.setTimer,
+    clearTimer: timers.clearTimer,
+  });
+
+  timers.fireAfter(60);
+  assert.deepEqual(signals, ["SIGTERM"]);
+  timers.fireAfter(65);
+  assert.deepEqual(signals, ["SIGTERM", "SIGKILL"]);
+  child.emit("close", null);
+
+  assert.deepEqual(await result, { code: null, killedBy: "SIGKILL" });
+  assert.equal(timers.pending.size, 0);
+});
+
+test("a child that exits after SIGTERM is not escalated", async () => {
+  const child = new EventEmitter();
+  const signals = [];
+  child.kill = (signal) => signals.push(signal);
+  const timers = controlledTimers();
+
+  const result = waitForChildExitWithEscalation(child, {
+    termAfterMs: 60,
+    killAfterMs: 65,
+    setTimer: timers.setTimer,
+    clearTimer: timers.clearTimer,
+  });
+
+  timers.fireAfter(60);
+  child.emit("close", 0);
+
+  assert.deepEqual(await result, { code: 0, killedBy: "SIGTERM" });
+  assert.deepEqual(signals, ["SIGTERM"]);
+  assert.equal(timers.pending.size, 0);
+});