diff --git a/.changeset/serve-sim-pr-4526.md b/.changeset/serve-sim-pr-4526.md
new file mode 100644
index 0000000000..af4db16cba
--- /dev/null
+++ b/.changeset/serve-sim-pr-4526.md
@@ -0,0 +1,5 @@
+---
+'@expo/build-tools': patch
+---
+
+Recover unhealthy device-session tunnels without changing their URLs and block further traffic when shutdown starts, even if ngrok cleanup times out.
diff --git a/packages/build-tools/src/steps/functions/startAgentDeviceRemoteSession.ts b/packages/build-tools/src/steps/functions/startAgentDeviceRemoteSession.ts
index 70c169af6e..c9d4ae0599 100644
--- a/packages/build-tools/src/steps/functions/startAgentDeviceRemoteSession.ts
+++ b/packages/build-tools/src/steps/functions/startAgentDeviceRemoteSession.ts
@@ -167,6 +167,7 @@ export async function runAgentDeviceRemoteSessionAsync(
       subdomainPrefix: 'agent-device',
       baseDomain: ngrokTunnelDomain,
       authtoken: ngrokAuthtoken,
+      healthCheck: { path: '/health' },
       logger: taskLogger,
     });
     tasks.signal.throwIfAborted();
diff --git a/packages/build-tools/src/steps/functions/startAppiumRemoteSession.ts b/packages/build-tools/src/steps/functions/startAppiumRemoteSession.ts
index e848dc5631..82a17eb6b9 100644
--- a/packages/build-tools/src/steps/functions/startAppiumRemoteSession.ts
+++ b/packages/build-tools/src/steps/functions/startAppiumRemoteSession.ts
@@ -274,6 +274,7 @@ export function createStartAppiumRemoteSessionBuildFunction(
           subdomainPrefix: 'appium',
           baseDomain: ngrokTunnelDomain,
           authtoken: ngrokAuthtoken,
+          healthCheck: { path: '/status' },
           logger,
         });
 
diff --git a/packages/build-tools/src/steps/functions/startArgentRemoteSession.ts b/packages/build-tools/src/steps/functions/startArgentRemoteSession.ts
index b24986e78b..d39cc92bd4 100644
--- a/packages/build-tools/src/steps/functions/startArgentRemoteSession.ts
+++ b/packages/build-tools/src/steps/functions/startArgentRemoteSession.ts
@@ -340,6 +340,7 @@ export function createStartArgentRemoteSessionBuildFunction(
           baseDomain: ngrokTunnelDomain,
           authtoken: ngrokAuthtoken,
           rewriteHostHeader: true,
+          healthCheck: { path: '/tools', statuses: [200, 401] },
           logger,
         });
         const publicToolsUrl = toolsTunnel.url;
diff --git a/packages/build-tools/src/steps/utils/__tests__/ngrokTunnel.test.ts b/packages/build-tools/src/steps/utils/__tests__/ngrokTunnel.test.ts
new file mode 100644
index 0000000000..6612cb3c33
--- /dev/null
+++ b/packages/build-tools/src/steps/utils/__tests__/ngrokTunnel.test.ts
@@ -0,0 +1,873 @@
+import { type bunyan } from '@expo/logger';
+import * as ngrok from '@ngrok/ngrok';
+import { once } from 'node:events';
+import { createServer } from 'node:http';
+import WebSocket, { WebSocketServer } from 'ws';
+import { type AddressInfo, createConnection, createServer as createTcpServer } from 'node:net';
+
+import { turtleFetch } from '../../../utils/turtleFetch';
+import { startNgrokTunnelAsync } from '../ngrokTunnel';
+
+jest.mock('@ngrok/ngrok');
+jest.mock('node:timers', () => ({
+  setTimeout: (...args: Parameters<typeof setTimeout>) => setTimeout(...args),
+  clearTimeout: (...args: Parameters<typeof clearTimeout>) => clearTimeout(...args),
+}));
+jest.mock('../../../utils/turtleFetch');
+
+const { Response } = jest.requireActual<typeof import('node-fetch')>('node-fetch');
+const url = 'https://web-preview-fixed.example.test';
+const logger = { info: jest.fn(), warn: jest.fn() } as unknown as bunyan;
+const options = {
+  port: 4321,
+  subdomainPrefix: 'web-preview',
+  subdomainId: 'fixed',
+  baseDomain: 'example.test',
+  authtoken: 'token',
+  rewriteHostHeader: true,
+  healthCheck: { path: '/healthz' },
+  logger,
+};
+
+function listener(publicUrl = url) {
+  return { url: () => publicUrl, close: jest.fn().mockResolvedValue(undefined) };
+}
+
+let initial: ReturnType<typeof listener>;
+let replacement: ReturnType<typeof listener>;
+
+beforeEach(() => {
+  jest.useFakeTimers({ doNotFake: ['nextTick', 'setImmediate'] });
+  jest.clearAllMocks();
+  initial = listener();
+  replacement = listener();
+  jest
+    .mocked(ngrok.forward)
+    .mockReset()
+    .mockResolvedValueOnce(initial as never)
+    .mockResolvedValue(replacement as never);
+  jest
+    .mocked(turtleFetch)
+    .mockReset()
+    .mockResolvedValue(new Response(undefined, { status: 200 }));
+});
+
+afterEach(() => {
+  jest.useRealTimers();
+});
+
+function failPublicProbes() {
+  jest.mocked(turtleFetch).mockImplementation(
+    async target =>
+      new Response(undefined, {
+        status: target.startsWith('https:') ? 503 : 200,
+      })
+  );
+}
+
+it('keeps tunnels without a health check unsupervised and closes them on stop', async () => {
+  const tunnel = await startNgrokTunnelAsync({ ...options, healthCheck: undefined });
+  await jest.advanceTimersByTimeAsync(90_000);
+  expect(turtleFetch).not.toHaveBeenCalled();
+  expect(ngrok.forward).toHaveBeenCalledTimes(1);
+  await tunnel.stopAsync();
+  expect(initial.close).toHaveBeenCalledTimes(1);
+});
+
+it('probes the public service and keeps a healthy listener open', async () => {
+  const tunnel = await startNgrokTunnelAsync(options);
+  try {
+    await jest.advanceTimersByTimeAsync(45_000);
+    expect(turtleFetch).toHaveBeenCalledTimes(3);
+    expect(turtleFetch).toHaveBeenCalledWith(
+      `${url}/healthz`,
+      'GET',
+      expect.objectContaining({
+        retries: 0,
+        redirect: 'manual',
+        headers: expect.objectContaining({ 'ngrok-skip-browser-warning': 'true' }),
+      })
+    );
+    expect(ngrok.forward).toHaveBeenCalledTimes(1);
+  } finally {
+    await tunnel.stopAsync();
+  }
+  expect(initial.close).toHaveBeenCalledTimes(1);
+  await jest.advanceTimersByTimeAsync(60_000);
+  expect(turtleFetch).toHaveBeenCalledTimes(3);
+});
+
+it('reopens after three failed public probes with a healthy local service, preserving the endpoint', async () => {
+  failPublicProbes();
+  const tunnel = await startNgrokTunnelAsync(options);
+  try {
+    await jest.advanceTimersByTimeAsync(30_000);
+    expect(initial.close).not.toHaveBeenCalled();
+    await jest.advanceTimersByTimeAsync(15_000);
+    expect(initial.close).toHaveBeenCalledTimes(1);
+    expect(ngrok.forward).toHaveBeenCalledTimes(2);
+    expect(jest.mocked(ngrok.forward).mock.calls[1][0]).toEqual({
+      addr: expect.any(Number),
+      authtoken: 'token',
+      domain: 'web-preview-fixed.example.test',
+      request_header_add: ['Host:localhost:4321'],
+      force_new_session: true,
+    });
+    expect(tunnel.url).toBe(url);
+    jest.mocked(turtleFetch).mockResolvedValue(new Response(undefined, { status: 200 }));
+    await jest.advanceTimersByTimeAsync(15_000);
+    expect(logger.info).toHaveBeenCalledWith(expect.stringContaining('healthy again'));
+  } finally {
+    await tunnel.stopAsync();
+  }
+  expect(replacement.close).toHaveBeenCalledTimes(1);
+});
+
+it('does not reopen when the local service is unhealthy', async () => {
+  jest.mocked(turtleFetch).mockResolvedValue(new Response(undefined, { status: 503 }));
+  const tunnel = await startNgrokTunnelAsync(options);
+  try {
+    await jest.advanceTimersByTimeAsync(90_000);
+    expect(ngrok.forward).toHaveBeenCalledTimes(1);
+    expect(initial.close).not.toHaveBeenCalled();
+  } finally {
+    await tunnel.stopAsync();
+  }
+});
+
+it('resets consecutive failures after a successful public probe', async () => {
+  failPublicProbes();
+  const tunnel = await startNgrokTunnelAsync(options);
+  try {
+    await jest.advanceTimersByTimeAsync(30_000);
+    jest.mocked(turtleFetch).mockResolvedValueOnce(new Response(undefined, { status: 200 }));
+    await jest.advanceTimersByTimeAsync(15_000);
+    await jest.advanceTimersByTimeAsync(30_000);
+    expect(ngrok.forward).toHaveBeenCalledTimes(1);
+  } finally {
+    await tunnel.stopAsync();
+  }
+});
+
+it('retries a failed reopen with backoff', async () => {
+  failPublicProbes();
+  jest
+    .mocked(ngrok.forward)
+    .mockReset()
+    .mockResolvedValueOnce(initial as never)
+    .mockRejectedValueOnce(new Error('offline'))
+    .mockResolvedValue(replacement as never);
+  const tunnel = await startNgrokTunnelAsync(options);
+  try {
+    await jest.advanceTimersByTimeAsync(45_000);
+    expect(ngrok.forward).toHaveBeenCalledTimes(2);
+    await jest.advanceTimersByTimeAsync(1_999);
+    expect(ngrok.forward).toHaveBeenCalledTimes(2);
+    await jest.advanceTimersByTimeAsync(1);
+    expect(ngrok.forward).toHaveBeenCalledTimes(3);
+  } finally {
+    await tunnel.stopAsync();
+  }
+});
+
+it('closes a listener that finishes opening after shutdown, with idempotent cleanup', async () => {
+  failPublicProbes();
+  let resolveOpening!: (value: ngrok.Listener) => void;
+  jest
+    .mocked(ngrok.forward)
+    .mockReset()
+    .mockResolvedValueOnce(initial as never)
+    .mockReturnValueOnce(
+      new Promise(resolve => {
+        resolveOpening = resolve;
+      })
+    );
+  const tunnel = await startNgrokTunnelAsync(options);
+  await jest.advanceTimersByTimeAsync(45_000);
+  const stopping = tunnel.stopAsync();
+  expect(tunnel.stopAsync()).toBe(stopping);
+  const stopped = jest.fn();
+  void stopping.then(stopped);
+  await jest.advanceTimersByTimeAsync(0);
+  expect(stopped).not.toHaveBeenCalled();
+  resolveOpening(replacement as never);
+  await stopping;
+  expect(replacement.close).toHaveBeenCalledTimes(1);
+  await jest.advanceTimersByTimeAsync(120_000);
+  expect(ngrok.forward).toHaveBeenCalledTimes(2);
+});
+
+it('waits for a replacement acquired during shutdown to finish closing', async () => {
+  failPublicProbes();
+  let resolveOpening!: (value: ngrok.Listener) => void;
+  let resolveClose!: () => void;
+  jest
+    .mocked(ngrok.forward)
+    .mockReset()
+    .mockResolvedValueOnce(initial as never)
+    .mockReturnValueOnce(new Promise(resolve => (resolveOpening = resolve)));
+  replacement.close.mockReturnValue(new Promise<void>(resolve => (resolveClose = resolve)));
+  const tunnel = await startNgrokTunnelAsync(options);
+  await jest.advanceTimersByTimeAsync(45_000);
+  let stopped = false;
+  const stopping = tunnel.stopAsync().then(() => {
+    stopped = true;
+  });
+  await jest.advanceTimersByTimeAsync(0);
+  resolveOpening(replacement as never);
+  await jest.advanceTimersByTimeAsync(0);
+  const stoppedBeforeClose = stopped;
+  resolveClose();
+  await jest.advanceTimersByTimeAsync(250);
+  await stopping;
+  expect(stoppedBeforeClose).toBe(false);
+  expect(replacement.close).toHaveBeenCalledTimes(1);
+});
+
+it.each([0, 4, 5, 10])('retires a reopen cancelled after %s promise turns', async turns => {
+  failPublicProbes();
+  let resolveOpening!: (value: ngrok.Listener) => void;
+  jest
+    .mocked(ngrok.forward)
+    .mockReset()
+    .mockResolvedValueOnce(initial as never)
+    .mockReturnValueOnce(new Promise(resolve => (resolveOpening = resolve)));
+  const tunnel = await startNgrokTunnelAsync(options);
+  await jest.advanceTimersByTimeAsync(45_000);
+  resolveOpening(replacement as never);
+  for (let turn = 0; turn < turns; turn++) {
+    await Promise.resolve();
+  }
+  await tunnel.stopAsync();
+  await jest.advanceTimersByTimeAsync(0);
+  expect(replacement.close).toHaveBeenCalledTimes(1);
+});
+
+it('retries a rejected close when a reopen finishes after shutdown', async () => {
+  failPublicProbes();
+  let resolveOpening!: (value: ngrok.Listener) => void;
+  jest
+    .mocked(ngrok.forward)
+    .mockReset()
+    .mockResolvedValueOnce(initial as never)
+    .mockReturnValueOnce(new Promise(resolve => (resolveOpening = resolve)));
+  const tunnel = await startNgrokTunnelAsync(options);
+  await jest.advanceTimersByTimeAsync(45_000);
+  const stopping = tunnel.stopAsync();
+  replacement.close.mockRejectedValueOnce(new Error('temporary unlisten failure'));
+  resolveOpening(replacement as never);
+  await jest.advanceTimersByTimeAsync(250);
+  await stopping;
+  expect(replacement.close).toHaveBeenCalledTimes(2);
+  const warnings = jest.mocked(logger.warn).mock.calls.length;
+  await jest.advanceTimersByTimeAsync(120_000);
+  expect(logger.warn).toHaveBeenCalledTimes(warnings);
+});
+
+it('fails stop if an in-flight reopen still has not settled by the stop deadline', async () => {
+  failPublicProbes();
+  let resolveOpening!: (value: ngrok.Listener) => void;
+  jest
+    .mocked(ngrok.forward)
+    .mockReset()
+    .mockResolvedValueOnce(initial as never)
+    .mockReturnValueOnce(new Promise(resolve => (resolveOpening = resolve)));
+  const tunnel = await startNgrokTunnelAsync(options);
+  await jest.advanceTimersByTimeAsync(45_000);
+  const rejected = expect(tunnel.stopAsync()).rejects.toThrow(
+    'Ngrok tunnel web-preview-fixed.example.test stop timed out after 4000ms'
+  );
+  await jest.advanceTimersByTimeAsync(4_000);
+  await rejected;
+  expect(ngrok.forward).toHaveBeenCalledTimes(2);
+  resolveOpening(replacement as never);
+  await jest.advanceTimersByTimeAsync(0);
+  expect(replacement.close).toHaveBeenCalledTimes(1);
+});
+
+it('retries an old listener while a reopen outlasts shutdown', async () => {
+  failPublicProbes();
+  initial.close.mockRejectedValueOnce(new Error('agent disconnected'));
+  let resolveOpening!: (value: ngrok.Listener) => void;
+  jest
+    .mocked(ngrok.forward)
+    .mockReset()
+    .mockResolvedValueOnce(initial as never)
+    .mockReturnValueOnce(new Promise(resolve => (resolveOpening = resolve)));
+  const tunnel = await startNgrokTunnelAsync(options);
+  await jest.advanceTimersByTimeAsync(45_000);
+  expect(initial.close).toHaveBeenCalledTimes(1);
+  const rejected = expect(tunnel.stopAsync()).rejects.toThrow(
+    'Ngrok tunnel web-preview-fixed.example.test stop timed out after 4000ms'
+  );
+  await jest.advanceTimersByTimeAsync(4_000);
+  await rejected;
+  const oldCloseCalls = initial.close.mock.calls.length;
+  resolveOpening(replacement as never);
+  await jest.advanceTimersByTimeAsync(0);
+  expect(oldCloseCalls).toBe(2);
+  expect(replacement.close).toHaveBeenCalledTimes(1);
+  expect(ngrok.forward).toHaveBeenCalledTimes(2);
+});
+
+it('fails stop if a pending reopen arrives but cannot be retired', async () => {
+  failPublicProbes();
+  let resolveOpening!: (value: ngrok.Listener) => void;
+  jest
+    .mocked(ngrok.forward)
+    .mockReset()
+    .mockResolvedValueOnce(initial as never)
+    .mockReturnValueOnce(new Promise(resolve => (resolveOpening = resolve)));
+  replacement.close.mockRejectedValue(new Error('unlisten failed'));
+  const tunnel = await startNgrokTunnelAsync(options);
+  await jest.advanceTimersByTimeAsync(45_000);
+  const rejected = expect(tunnel.stopAsync()).rejects.toThrow(
+    'Ngrok tunnel web-preview-fixed.example.test stop timed out'
+  );
+  resolveOpening(replacement as never);
+  await jest.advanceTimersByTimeAsync(4_000);
+  await rejected;
+  expect(replacement.close.mock.calls.length).toBeGreaterThan(1);
+  expect(logger.warn).toHaveBeenCalledWith(
+    expect.objectContaining({ err: expect.any(Error) }),
+    'Could not retire late ngrok tunnel web-preview-fixed.example.test.'
+  );
+  const warnings = jest.mocked(logger.warn).mock.calls.length;
+  await jest.advanceTimersByTimeAsync(120_000);
+  expect(logger.warn).toHaveBeenCalledTimes(warnings);
+  expect(ngrok.forward).toHaveBeenCalledTimes(2);
+});
+
+it('rejects a changed public URL and closes the replacement', async () => {
+  failPublicProbes();
+  const changed = listener('https://different.example.test');
+  jest
+    .mocked(ngrok.forward)
+    .mockReset()
+    .mockResolvedValueOnce(initial as never)
+    .mockResolvedValue(changed as never);
+  const tunnel = await startNgrokTunnelAsync(options);
+  try {
+    await jest.advanceTimersByTimeAsync(45_000);
+    expect(changed.close).toHaveBeenCalledTimes(1);
+    expect(tunnel.url).toBe(url);
+    expect(logger.warn).toHaveBeenCalledWith(
+      expect.objectContaining({ err: expect.any(Error) }),
+      expect.stringContaining('Could not reopen')
+    );
+  } finally {
+    await tunnel.stopAsync();
+  }
+});
+
+it('treats ngrok error responses as failures even if their status is accepted', async () => {
+  jest.mocked(turtleFetch).mockImplementation(
+    async target =>
+      new Response(undefined, {
+        status: 200,
+        headers: target.startsWith('https:') ? { 'ngrok-error-code': 'ERR_NGROK_3200' } : {},
+      })
+  );
+  const tunnel = await startNgrokTunnelAsync(options);
+  try {
+    await jest.advanceTimersByTimeAsync(45_000);
+    expect(ngrok.forward).toHaveBeenCalledTimes(2);
+  } finally {
+    await tunnel.stopAsync();
+  }
+});
+
+it('reopens on a fresh agent session even if closing the old listener fails', async () => {
+  failPublicProbes();
+  initial.close.mockRejectedValueOnce(new Error('agent disconnected'));
+  const tunnel = await startNgrokTunnelAsync(options);
+  try {
+    await jest.advanceTimersByTimeAsync(45_000);
+    expect(ngrok.forward).toHaveBeenCalledTimes(2);
+    expect(ngrok.forward).toHaveBeenLastCalledWith(
+      expect.objectContaining({ force_new_session: true })
+    );
+    expect(ngrok.disconnect).not.toHaveBeenCalled();
+  } finally {
+    await tunnel.stopAsync();
+  }
+  expect(initial.close).toHaveBeenCalledTimes(2);
+  expect(replacement.close).toHaveBeenCalledTimes(1);
+});
+
+it('retries a rejected close before reopening an endpoint that remains bound', async () => {
+  failPublicProbes();
+  let domainOccupied = true;
+  initial.close
+    .mockRejectedValueOnce(new Error('agent disconnected'))
+    .mockImplementation(async () => {
+      domainOccupied = false;
+    });
+  jest
+    .mocked(ngrok.forward)
+    .mockReset()
+    .mockResolvedValueOnce(initial as never)
+    .mockImplementation(async () => {
+      if (domainOccupied) {
+        throw new Error('endpoint is still bound');
+      }
+      return replacement as never;
+    });
+  const tunnel = await startNgrokTunnelAsync(options);
+  try {
+    await jest.advanceTimersByTimeAsync(45_000);
+    expect(initial.close).toHaveBeenCalledTimes(1);
+    expect(ngrok.forward).toHaveBeenCalledTimes(2);
+    await jest.advanceTimersByTimeAsync(2_000);
+    expect(initial.close).toHaveBeenCalledTimes(2);
+    expect(ngrok.forward).toHaveBeenCalledTimes(3);
+    expect(tunnel.url).toBe(url);
+  } finally {
+    await tunnel.stopAsync();
+  }
+  expect(replacement.close).toHaveBeenCalledTimes(1);
+});
+
+it('retires an old listener even after its replacement is healthy', async () => {
+  failPublicProbes();
+  initial.close.mockRejectedValueOnce(new Error('agent disconnected'));
+  const tunnel = await startNgrokTunnelAsync(options);
+  try {
+    await jest.advanceTimersByTimeAsync(45_000);
+    expect(initial.close).toHaveBeenCalledTimes(1);
+    jest.mocked(turtleFetch).mockResolvedValue(new Response(undefined, { status: 200 }));
+    await jest.advanceTimersByTimeAsync(15_000);
+    expect(initial.close).toHaveBeenCalledTimes(2);
+    expect(ngrok.forward).toHaveBeenCalledTimes(2);
+  } finally {
+    await tunnel.stopAsync();
+  }
+});
+
+it('retries an old listener without repeating its close warning on every probe', async () => {
+  failPublicProbes();
+  initial.close.mockRejectedValue(new Error('old session disconnected'));
+  const tunnel = await startNgrokTunnelAsync(options);
+  await jest.advanceTimersByTimeAsync(45_000);
+  const warnings = jest.mocked(logger.warn).mock.calls.length;
+  expect(warnings).toBeGreaterThan(0);
+  jest.mocked(turtleFetch).mockResolvedValue(new Response(undefined, { status: 200 }));
+  await jest.advanceTimersByTimeAsync(120_000);
+  expect(initial.close.mock.calls.length).toBeGreaterThan(1);
+  expect(ngrok.forward).toHaveBeenCalledTimes(2);
+  expect(logger.warn).toHaveBeenCalledTimes(warnings);
+  const rejected = expect(tunnel.stopAsync()).rejects.toThrow(
+    'Ngrok tunnel web-preview-fixed.example.test stop timed out'
+  );
+  await jest.advanceTimersByTimeAsync(4_000);
+  await rejected;
+  expect(replacement.close).toHaveBeenCalledTimes(1);
+});
+
+it('retries a rejected close during shutdown', async () => {
+  const failure = new Error('agent disconnected');
+  initial.close.mockRejectedValueOnce(failure);
+  const tunnel = await startNgrokTunnelAsync(options);
+  const stopping = tunnel.stopAsync();
+  await jest.advanceTimersByTimeAsync(250);
+  await stopping;
+  expect(initial.close).toHaveBeenCalledTimes(2);
+  expect(logger.warn).toHaveBeenCalledTimes(1);
+  expect(logger.warn).toHaveBeenCalledWith(
+    { err: failure },
+    'Could not stop ngrok tunnel web-preview-fixed.example.test.'
+  );
+});
+
+it('logs the first close rejection once while bounded shutdown retries it', async () => {
+  const failure = new Error('agent disconnected');
+  initial.close.mockRejectedValue(failure);
+  const tunnel = await startNgrokTunnelAsync(options);
+  const rejected = expect(tunnel.stopAsync()).rejects.toThrow('stop timed out');
+  await jest.advanceTimersByTimeAsync(4_000);
+  await rejected;
+  expect(initial.close.mock.calls.length).toBeGreaterThan(1);
+  expect(logger.warn).toHaveBeenCalledTimes(1);
+  expect(logger.warn).toHaveBeenCalledWith(
+    { err: failure },
+    'Could not stop ngrok tunnel web-preview-fixed.example.test.'
+  );
+});
+
+it('bounds shutdown during recovery without duplicating a pending native close', async () => {
+  failPublicProbes();
+  let finishClose!: () => void;
+  initial.close.mockReturnValueOnce(new Promise<void>(resolve => (finishClose = resolve)));
+  const tunnel = await startNgrokTunnelAsync(options);
+  await jest.advanceTimersByTimeAsync(45_000);
+  const stopping = tunnel.stopAsync();
+  expect(tunnel.stopAsync()).toBe(stopping);
+  const rejected = expect(stopping).rejects.toThrow(
+    'Ngrok tunnel web-preview-fixed.example.test stop timed out after 4000ms'
+  );
+  await jest.advanceTimersByTimeAsync(4_000);
+  await rejected;
+  expect(initial.close).toHaveBeenCalledTimes(1);
+  expect(ngrok.forward).toHaveBeenCalledTimes(1);
+  const warnings = jest.mocked(logger.warn).mock.calls.length;
+  finishClose();
+  await jest.advanceTimersByTimeAsync(120_000);
+  expect(logger.warn).toHaveBeenCalledTimes(warnings);
+  expect(initial.close).toHaveBeenCalledTimes(1);
+});
+
+it('bounds a stalled listener close before reopening', async () => {
+  failPublicProbes();
+  initial.close.mockImplementationOnce(async () => await new Promise(() => {}));
+  const tunnel = await startNgrokTunnelAsync(options);
+  try {
+    await jest.advanceTimersByTimeAsync(49_999);
+    expect(ngrok.forward).toHaveBeenCalledTimes(1);
+    await jest.advanceTimersByTimeAsync(1);
+    expect(ngrok.forward).toHaveBeenCalledTimes(2);
+  } finally {
+    const stopping = tunnel.stopAsync();
+    const rejected = expect(stopping).rejects.toThrow(
+      'Ngrok tunnel web-preview-fixed.example.test stop timed out'
+    );
+    await jest.advanceTimersByTimeAsync(4_000);
+    await rejected;
+  }
+});
+
+it('does not queue more native opens while a timed-out open is still pending', async () => {
+  failPublicProbes();
+  let resolveOpening!: (value: ngrok.Listener) => void;
+  jest
+    .mocked(ngrok.forward)
+    .mockReset()
+    .mockResolvedValueOnce(initial as never)
+    .mockReturnValueOnce(
+      new Promise(resolve => {
+        resolveOpening = resolve;
+      })
+    )
+    .mockResolvedValue(replacement as never);
+  const tunnel = await startNgrokTunnelAsync(options);
+  const late = listener();
+  try {
+    await jest.advanceTimersByTimeAsync(180_000);
+    expect(ngrok.forward).toHaveBeenCalledTimes(2);
+    resolveOpening(late as never);
+    await jest.advanceTimersByTimeAsync(30_000);
+    expect(late.close).toHaveBeenCalledTimes(1);
+    expect(ngrok.forward).toHaveBeenCalledTimes(3);
+  } finally {
+    await tunnel.stopAsync();
+  }
+  expect(replacement.close).toHaveBeenCalledTimes(1);
+});
+
+it('bounds initial tunnel creation and retires a late listener', async () => {
+  let resolveOpening!: (value: ngrok.Listener) => void;
+  jest
+    .mocked(ngrok.forward)
+    .mockReset()
+    .mockReturnValueOnce(
+      new Promise(resolve => {
+        resolveOpening = resolve;
+      })
+    );
+  const opening = startNgrokTunnelAsync(options);
+  const rejected = expect(opening).rejects.toThrow('Ngrok tunnel open timed out');
+  await jest.advanceTimersByTimeAsync(15_000);
+  await rejected;
+  resolveOpening(initial as never);
+  await jest.advanceTimersByTimeAsync(0);
+  expect(initial.close).toHaveBeenCalledTimes(1);
+});
+
+it('retries a rejected close after initial tunnel creation timed out', async () => {
+  let resolveOpening!: (value: ngrok.Listener) => void;
+  jest
+    .mocked(ngrok.forward)
+    .mockReset()
+    .mockReturnValueOnce(new Promise(resolve => (resolveOpening = resolve)));
+  const opening = startNgrokTunnelAsync(options);
+  const rejected = expect(opening).rejects.toThrow('Ngrok tunnel open timed out');
+  await jest.advanceTimersByTimeAsync(15_000);
+  await rejected;
+  initial.close.mockRejectedValueOnce(new Error('temporary unlisten failure'));
+  resolveOpening(initial as never);
+  await jest.advanceTimersByTimeAsync(250);
+  expect(initial.close).toHaveBeenCalledTimes(2);
+});
+
+it('retires only the late listener without blaming it for an older stuck listener', async () => {
+  failPublicProbes();
+  initial.close.mockRejectedValue(new Error('old session disconnected'));
+  let resolveOpening!: (value: ngrok.Listener) => void;
+  jest
+    .mocked(ngrok.forward)
+    .mockReset()
+    .mockResolvedValueOnce(initial as never)
+    .mockReturnValueOnce(new Promise(resolve => (resolveOpening = resolve)))
+    .mockResolvedValue(replacement as never);
+  const tunnel = await startNgrokTunnelAsync(options);
+  try {
+    await jest.advanceTimersByTimeAsync(60_000);
+    const late = listener();
+    resolveOpening(late as never);
+    jest.mocked(turtleFetch).mockResolvedValue(new Response(undefined, { status: 200 }));
+    await jest.advanceTimersByTimeAsync(4_000);
+    expect(late.close).toHaveBeenCalledTimes(1);
+    expect(
+      jest
+        .mocked(logger.warn)
+        .mock.calls.some(([, message]) => message?.includes('Could not retire late'))
+    ).toBe(false);
+  } finally {
+    initial.close.mockResolvedValue(undefined);
+    await tunnel.stopAsync();
+  }
+});
+
+it('recovers using actual HTTP health probes with a local ngrok adapter', async () => {
+  const actualFetch = jest.requireActual<typeof import('node-fetch')>('node-fetch').default;
+  const realSetTimeout = jest.requireActual<typeof import('node:timers')>('node:timers').setTimeout;
+  let broken = true;
+  const local = createServer((_req, res) => {
+    res.writeHead(200);
+    res.end('healthy');
+  });
+  const publicServer = createServer((_req, res) => {
+    res.writeHead(broken ? 503 : 200);
+    res.end('probe');
+  });
+  await Promise.all(
+    [local, publicServer].map(
+      server => new Promise<void>(resolve => server.listen(0, '127.0.0.1', resolve))
+    )
+  );
+  const publicUrl = `http://127.0.0.1:${(publicServer.address() as AddressInfo).port}`;
+  let completedRequests = 0;
+  jest.mocked(turtleFetch).mockImplementation(async (target, method, requestOptions) => {
+    const response = await actualFetch(target, { ...requestOptions, method });
+    completedRequests++;
+    return response;
+  });
+  const first = listener(publicUrl);
+  const next = listener(publicUrl);
+  jest
+    .mocked(ngrok.forward)
+    .mockReset()
+    .mockResolvedValueOnce(first as never)
+    .mockImplementation(async () => {
+      broken = false;
+      return next as never;
+    });
+  const tunnel = await startNgrokTunnelAsync({
+    ...options,
+    port: (local.address() as AddressInfo).port,
+  });
+  try {
+    for (let count = 0; count < 3; count++) {
+      await jest.advanceTimersByTimeAsync(15_000);
+      for (let turns = 0; turns < 50 && completedRequests < (count + 1) * 2; turns++) {
+        await new Promise(resolve => realSetTimeout(resolve, 10));
+      }
+      expect(completedRequests).toBe((count + 1) * 2);
+    }
+    expect(ngrok.forward).toHaveBeenCalledTimes(2);
+    expect(first.close).toHaveBeenCalledTimes(1);
+    expect((await actualFetch(`${tunnel.url}/healthz`)).status).toBe(200);
+  } finally {
+    await tunnel.stopAsync();
+    await Promise.all(
+      [local, publicServer].map(
+        server =>
+          new Promise<void>((resolve, reject) =>
+            server.close(err => (err ? reject(err) : resolve()))
+          )
+      )
+    );
+  }
+  expect(next.close).toHaveBeenCalledTimes(1);
+});
+
+it('blocks HTTP and existing WebSockets on Stop even when ngrok cannot close', async () => {
+  jest.useRealTimers();
+  const actualFetch = jest.requireActual<typeof import('node-fetch')>('node-fetch').default;
+  let requests = 0;
+  let messages = 0;
+  const backend = createServer((_request, response) => {
+    requests++;
+    response.end('owned backend');
+  });
+  const websockets = new WebSocketServer({ server: backend });
+  websockets.on('connection', socket => {
+    socket.on('message', data => {
+      messages++;
+      socket.send(data);
+    });
+  });
+  backend.listen(0, '127.0.0.1');
+  await once(backend, 'listening');
+  const backendPort = (backend.address() as AddressInfo).port;
+  const tunnel = await startNgrokTunnelAsync({
+    ...options,
+    port: backendPort,
+    healthCheck: undefined,
+  });
+  const targetPort = (jest.mocked(ngrok.forward).mock.calls[0][0] as ngrok.Config).addr;
+  const targetUrl = `http://127.0.0.1:${targetPort}`;
+  const socket = new WebSocket(`ws://127.0.0.1:${targetPort}`);
+  const opened = once(socket, 'open');
+  try {
+    expect(await (await actualFetch(targetUrl)).text()).toBe('owned backend');
+    await opened;
+    const echoed = once(socket, 'message');
+    socket.send('before-stop');
+    expect((await echoed)[0].toString()).toBe('before-stop');
+    const closed = once(socket, 'close');
+    initial.close.mockRejectedValue(new Error('agent disconnected'));
+    const stopping = tunnel.stopAsync();
+    const rejected = expect(stopping).rejects.toThrow('stop timed out after 4000ms');
+    await expect(actualFetch(targetUrl, { timeout: 1_000 })).rejects.toThrow();
+    await closed;
+    expect(requests).toBe(1);
+    expect(messages).toBe(1);
+    expect(await (await actualFetch(`http://127.0.0.1:${backendPort}`)).text()).toBe(
+      'owned backend'
+    );
+    await rejected;
+    await expect(actualFetch(targetUrl, { timeout: 1_000 })).rejects.toThrow();
+    expect(requests).toBe(2);
+    expect(messages).toBe(1);
+    const competing = createTcpServer();
+    const conflict = once(competing, 'error');
+    competing.listen(targetPort as number, '127.0.0.1');
+    expect((await conflict)[0]).toMatchObject({ code: 'EADDRINUSE' });
+  } finally {
+    socket.terminate();
+    for (const client of websockets.clients) {
+      client.terminate();
+    }
+    websockets.close();
+    backend.closeAllConnections();
+    await new Promise<void>(resolve => backend.close(() => resolve()));
+    await tunnel.stopAsync().catch(() => {});
+  }
+});
+
+it('releases its local target when initial tunnel creation fails', async () => {
+  jest.useRealTimers();
+  jest.mocked(ngrok.forward).mockReset().mockRejectedValue(new Error('forward failed'));
+  await expect(startNgrokTunnelAsync(options)).rejects.toThrow('forward failed');
+  const targetPort = (jest.mocked(ngrok.forward).mock.calls[0][0] as ngrok.Config).addr;
+  const server = createServer();
+  server.listen(targetPort as number, '127.0.0.1');
+  await once(server, 'listening');
+  await new Promise<void>(resolve => server.close(() => resolve()));
+});
+
+it('preserves a full response for a half-closed slow reader', async () => {
+  jest.useRealTimers();
+  const payload = Buffer.alloc(4 * 1024 * 1024, 37);
+  const backend = createTcpServer({ allowHalfOpen: true }, socket => {
+    socket.resume();
+    socket.on('end', () => socket.end(payload));
+  });
+  backend.listen(0, '127.0.0.1');
+  await once(backend, 'listening');
+  const tunnel = await startNgrokTunnelAsync({
+    ...options,
+    port: (backend.address() as AddressInfo).port,
+    healthCheck: undefined,
+  });
+  const targetPort = (jest.mocked(ngrok.forward).mock.calls[0][0] as ngrok.Config).addr as number;
+  const socket = createConnection({ host: '127.0.0.1', port: targetPort, allowHalfOpen: true });
+  try {
+    const chunks: Buffer[] = [];
+    socket.on('data', chunk => chunks.push(chunk));
+    const ended = once(socket, 'end');
+    socket.pause();
+    socket.end('request');
+    await new Promise(resolve => setTimeout(resolve, 100));
+    socket.resume();
+    await ended;
+    expect(Buffer.concat(chunks).equals(payload)).toBe(true);
+  } finally {
+    socket.destroy();
+    await tunnel.stopAsync();
+    await new Promise<void>(resolve => backend.close(() => resolve()));
+  }
+});
+
+it.each(['resolve', 'reject'])(
+  'releases the target after timed-out startup later %s',
+  async outcome => {
+    let resolveOpening!: (value: ngrok.Listener) => void;
+    let rejectOpening!: (error: Error) => void;
+    jest
+      .mocked(ngrok.forward)
+      .mockReset()
+      .mockReturnValue(
+        new Promise((resolve, reject) => {
+          resolveOpening = resolve;
+          rejectOpening = reject;
+        })
+      );
+    const opening = startNgrokTunnelAsync(options);
+    const rejected = expect(opening).rejects.toThrow('open timed out');
+    await new Promise<void>(resolve => setImmediate(resolve));
+    await jest.advanceTimersByTimeAsync(15_000);
+    await rejected;
+    const targetPort = (jest.mocked(ngrok.forward).mock.calls[0][0] as ngrok.Config).addr as number;
+    if (outcome === 'resolve') {
+      resolveOpening(replacement as never);
+    } else {
+      rejectOpening(new Error('forward failed'));
+    }
+    await jest.advanceTimersByTimeAsync(0);
+    const server = createTcpServer();
+    server.listen(targetPort, '127.0.0.1');
+    await once(server, 'listening');
+    await new Promise<void>(resolve => server.close(() => resolve()));
+  }
+);
+
+it('drains a full upload when the backend ends its response early', async () => {
+  jest.useRealTimers();
+  const payload = Buffer.alloc(4 * 1024 * 1024, 51);
+  let received!: Buffer;
+  let receivedRequest!: () => void;
+  const completed = new Promise<void>(resolve => {
+    receivedRequest = resolve;
+  });
+  const backend = createTcpServer({ allowHalfOpen: true }, socket => {
+    const chunks: Buffer[] = [];
+    socket.on('data', chunk => chunks.push(chunk));
+    socket.on('end', () => {
+      received = Buffer.concat(chunks);
+      receivedRequest();
+    });
+    socket.pause();
+    socket.end('early response');
+    setTimeout(() => socket.resume(), 100);
+  });
+  backend.listen(0, '127.0.0.1');
+  await once(backend, 'listening');
+  const tunnel = await startNgrokTunnelAsync({
+    ...options,
+    port: (backend.address() as AddressInfo).port,
+    healthCheck: undefined,
+  });
+  const targetPort = (jest.mocked(ngrok.forward).mock.calls[0][0] as ngrok.Config).addr as number;
+  const socket = createConnection({ host: '127.0.0.1', port: targetPort, allowHalfOpen: true });
+  try {
+    socket.resume();
+    socket.end(payload);
+    await completed;
+    expect(received.equals(payload)).toBe(true);
+  } finally {
+    socket.destroy();
+    await tunnel.stopAsync();
+    await new Promise<void>(resolve => backend.close(() => resolve()));
+  }
+});
diff --git a/packages/build-tools/src/steps/utils/__tests__/remoteDeviceRunSession.test.ts b/packages/build-tools/src/steps/utils/__tests__/remoteDeviceRunSession.test.ts
index 6fc8170446..1539d79385 100644
--- a/packages/build-tools/src/steps/utils/__tests__/remoteDeviceRunSession.test.ts
+++ b/packages/build-tools/src/steps/utils/__tests__/remoteDeviceRunSession.test.ts
@@ -932,7 +932,7 @@ describe(waitForWebPreviewReadyAsync, () => {
 
 describe(startNgrokTunnelAsync, () => {
   it.each(['rejected', 'stalled'] as const)(
-    'retains a %s close failure on repeated stops',
+    'bounds %s listener retirement and reuses the stop promise',
     async mode => {
       jest.useFakeTimers();
       try {
@@ -954,14 +954,12 @@ describe(startNgrokTunnelAsync, () => {
           logger: createLoggerMock(),
         });
         const stopping = tunnel.stopAsync();
-        const assertion = expect(stopping).rejects.toThrow(
-          mode === 'rejected' ? 'close failed' : 'Ngrok tunnel stop timed out after 4000ms.'
-        );
+        const assertion = expect(stopping).rejects.toThrow(/stop timed out after 4000ms/);
         expect(tunnel.stopAsync()).toBe(stopping);
         await jest.advanceTimersByTimeAsync(4_000);
         await assertion;
         await expect(tunnel.stopAsync()).rejects.toThrow();
-        expect(close).toHaveBeenCalledTimes(1);
+        expect(close).toHaveBeenCalled();
       } finally {
         jest.useRealTimers();
       }
@@ -985,7 +983,7 @@ describe(startNgrokTunnelAsync, () => {
 
     expect(ngrok.forward).toHaveBeenCalledWith(
       expect.objectContaining({
-        addr: 4321,
+        addr: expect.any(Number),
         authtoken: 'token',
         domain: expect.stringMatching(/^web-preview-[a-f0-9]{32}\.eas-simulator\.ngrok\.dev$/),
       })
@@ -1302,7 +1300,10 @@ describe(startDeviceSessionHostAsync, () => {
         recordingDirectory,
       }),
     ]);
-    expect(ngrok.forward).toHaveBeenCalledWith(expect.objectContaining({ addr: port }));
+    expect(ngrok.forward).toHaveBeenCalledWith(
+      expect.objectContaining({ addr: expect.any(Number) })
+    );
+    expect(ngrok.forward).not.toHaveBeenCalledWith(expect.objectContaining({ addr: port }));
     expect(preview.apiUrl).toBe('https://android-preview.example.test');
 
     await host.finishAsync();
@@ -1438,7 +1439,10 @@ describe(startDeviceSessionHostAsync, () => {
         packageVersion,
       }),
     ]);
-    expect(ngrok.forward).toHaveBeenCalledWith(expect.objectContaining({ addr: port }));
+    expect(ngrok.forward).toHaveBeenCalledWith(
+      expect.objectContaining({ addr: expect.any(Number) })
+    );
+    expect(ngrok.forward).not.toHaveBeenCalledWith(expect.objectContaining({ addr: port }));
     expect(preview.apiUrl).toBe('https://ios-preview.example.test');
 
     await host.finishAsync();
diff --git a/packages/build-tools/src/steps/utils/deviceSessionHost.ts b/packages/build-tools/src/steps/utils/deviceSessionHost.ts
index f4056ec12c..e14953c471 100644
--- a/packages/build-tools/src/steps/utils/deviceSessionHost.ts
+++ b/packages/build-tools/src/steps/utils/deviceSessionHost.ts
@@ -623,6 +623,7 @@ async function startDeviceSessionHostInternalAsync(
           subdomainId,
           baseDomain,
           authtoken,
+          healthCheck: { path: isAndroid ? '/readyz' : '/healthz' },
           logger,
         });
         if (finishTask) {
diff --git a/packages/build-tools/src/steps/utils/ngrokTunnel.ts b/packages/build-tools/src/steps/utils/ngrokTunnel.ts
new file mode 100644
index 0000000000..5c581bcd6b
--- /dev/null
+++ b/packages/build-tools/src/steps/utils/ngrokTunnel.ts
@@ -0,0 +1,368 @@
+import { SystemError } from '@expo/eas-build-job';
+import { type bunyan } from '@expo/logger';
+import * as ngrok from '@ngrok/ngrok';
+import { randomBytes } from 'node:crypto';
+import { once } from 'node:events';
+import { type AddressInfo, type Socket, createConnection, createServer } from 'node:net';
+import { clearTimeout, setTimeout } from 'node:timers';
+
+import { turtleFetch } from '../../utils/turtleFetch';
+import { withDeviceRunSessionTimeoutAsync } from './deviceRunSessionTimeout';
+
+const PROBE_INTERVAL_MS = 15_000;
+const FAILURE_THRESHOLD = 3;
+const STOP_TIMEOUT_MS = 4_000;
+
+export type NgrokTunnelHandle = {
+  url: string;
+  subdomainId: string;
+  stopAsync: () => Promise<void>;
+};
+
+export async function startNgrokTunnelAsync({
+  port,
+  subdomainPrefix,
+  subdomainId = randomBytes(16).toString('hex'),
+  baseDomain,
+  authtoken,
+  rewriteHostHeader,
+  healthCheck,
+  logger,
+}: {
+  port: number;
+  subdomainPrefix: string;
+  subdomainId?: string;
+  baseDomain: string;
+  authtoken: string;
+  rewriteHostHeader?: boolean;
+  healthCheck?: { path: string; statuses?: number[] };
+  logger: bunyan;
+}): Promise<NgrokTunnelHandle> {
+  const domain = `${subdomainPrefix}-${subdomainId}.${baseDomain}`;
+  const controller = new AbortController();
+  const { signal } = controller;
+  const sockets = new Set<Socket>();
+  const target = createServer({ allowHalfOpen: true }, client => {
+    if (signal.aborted) {
+      client.destroy();
+      return;
+    }
+    const upstream = createConnection({ host: '127.0.0.1', port, allowHalfOpen: true });
+    for (const socket of [client, upstream]) {
+      sockets.add(socket);
+      socket.on('error', () => {
+        client.destroy();
+        upstream.destroy();
+      });
+      socket.on('close', () => sockets.delete(socket));
+    }
+    client.pipe(upstream).pipe(client);
+  });
+  target.listen(0, '127.0.0.1');
+  await once(target, 'listening');
+  target.unref();
+  signal.addEventListener(
+    'abort',
+    () => {
+      for (const socket of sockets) {
+        socket.destroy();
+      }
+    },
+    { once: true }
+  );
+  const config: ngrok.Config = {
+    addr: (target.address() as AddressInfo).port,
+    authtoken,
+    domain,
+    ...(rewriteHostHeader ? { request_header_add: [`Host:localhost:${port}`] } : {}),
+  };
+
+  const ownedListeners = new Set<ngrok.Listener>();
+  const retiredListeners = new Set<ngrok.Listener>();
+  const closingListeners = new Map<ngrok.Listener, Promise<void>>();
+  let pendingOpen: Promise<ngrok.Listener> | undefined;
+  let currentListener: ngrok.Listener | undefined;
+  function releaseTarget(): void {
+    if (signal.aborted && !pendingOpen && ownedListeners.size === 0 && target.listening) {
+      target.close();
+    }
+  }
+
+  async function closeAsync(
+    listener: ngrok.Listener,
+    closeSignal: AbortSignal,
+    logFailure = true
+  ): Promise<void> {
+    retiredListeners.add(listener);
+    let closing = closingListeners.get(listener);
+    if (!closing) {
+      closing = Promise.resolve().then(async () => await listener.close());
+      closingListeners.set(listener, closing);
+      void closing.then(
+        () => {
+          closingListeners.delete(listener);
+          retiredListeners.delete(listener);
+          ownedListeners.delete(listener);
+          releaseTarget();
+        },
+        () => closingListeners.delete(listener)
+      );
+    }
+    try {
+      await withDeviceRunSessionTimeoutAsync(
+        { name: 'Ngrok tunnel close', timeoutMs: 5_000, signal: closeSignal },
+        async () => await closing
+      );
+    } catch (err) {
+      if (logFailure && !closeSignal.aborted) {
+        logger.warn({ err }, `Could not stop ngrok tunnel ${domain}.`);
+      }
+    }
+  }
+
+  async function retireListenersAsync(retirementSignal: AbortSignal): Promise<void> {
+    let logFailure = true;
+    while (retiredListeners.size > 0) {
+      retirementSignal.throwIfAborted();
+      await Promise.all(
+        [...retiredListeners].map(retired => closeAsync(retired, retirementSignal, logFailure))
+      );
+      logFailure = false;
+      if (retiredListeners.size > 0) {
+        await waitAsync(250, retirementSignal);
+      }
+    }
+  }
+
+  async function retireLateListenerAsync(listener: ngrok.Listener): Promise<void> {
+    retiredListeners.add(listener);
+    try {
+      await withDeviceRunSessionTimeoutAsync(
+        { name: 'Late ngrok tunnel retirement', timeoutMs: STOP_TIMEOUT_MS },
+        async retirementSignal => {
+          while (retiredListeners.has(listener)) {
+            retirementSignal.throwIfAborted();
+            await closeAsync(listener, retirementSignal, false);
+            if (retiredListeners.has(listener)) {
+              await waitAsync(250, retirementSignal);
+            }
+          }
+        }
+      );
+    } catch (err) {
+      logger.warn({ err }, `Could not retire late ngrok tunnel ${domain}.`);
+    }
+  }
+
+  async function openAsync(forceNewSession = false): Promise<ngrok.Listener> {
+    if (pendingOpen) {
+      throw new SystemError(`A previous ngrok tunnel open for ${domain} is still pending.`);
+    }
+    let acquired: ngrok.Listener | undefined;
+    let retirement: Promise<void> | undefined;
+    const retireAcquired = () => {
+      if (acquired) {
+        retirement ??= retireLateListenerAsync(acquired);
+      }
+    };
+    try {
+      return await withDeviceRunSessionTimeoutAsync(
+        { name: 'Ngrok tunnel open', timeoutMs: 15_000, signal },
+        async openSignal => {
+          openSignal.throwIfAborted();
+          const opening = ngrok
+            .forward({
+              ...config,
+              ...(forceNewSession ? { force_new_session: true } : {}),
+            })
+            .then(listener => {
+              acquired = listener;
+              ownedListeners.add(listener);
+              return listener;
+            })
+            .finally(() => {
+              pendingOpen = undefined;
+            });
+          pendingOpen = opening;
+          void opening
+            .then(() => {
+              if (openSignal.aborted) {
+                retireAcquired();
+              }
+            })
+            .catch(() => releaseTarget());
+          const listener = await opening;
+          openSignal.throwIfAborted();
+          return listener;
+        }
+      );
+    } catch (err) {
+      retireAcquired();
+      throw err;
+    }
+  }
+
+  logger.info(`Starting ngrok tunnel ${domain} -> http://localhost:${port}.`);
+  let publicUrl: string | null;
+  try {
+    currentListener = await openAsync();
+    publicUrl = currentListener.url();
+    if (!publicUrl) {
+      await closeAsync(currentListener, signal);
+      currentListener = undefined;
+      throw new SystemError(`ngrok tunnel for ${domain} did not return a public URL.`);
+    }
+  } catch (error) {
+    controller.abort();
+    releaseTarget();
+    throw error;
+  }
+
+  const url = publicUrl;
+
+  async function probeAsync(
+    baseUrl: string,
+    { path, statuses = [200] }: NonNullable<typeof healthCheck>
+  ): Promise<boolean> {
+    try {
+      return await withDeviceRunSessionTimeoutAsync(
+        { name: 'Ngrok tunnel health probe', timeoutMs: 5_000, signal },
+        async probeSignal => {
+          const requestController = new AbortController();
+          try {
+            const response = await turtleFetch(new URL(path, baseUrl).href, 'GET', {
+              retries: 0,
+              redirect: 'manual',
+              shouldThrowOnNotOk: false,
+              headers: { 'ngrok-skip-browser-warning': 'true', 'Cache-Control': 'no-cache' },
+              signal: AbortSignal.any([probeSignal, requestController.signal]),
+            });
+            return !response.headers.has('ngrok-error-code') && statuses.includes(response.status);
+          } finally {
+            requestController.abort();
+          }
+        }
+      );
+    } catch {
+      return false;
+    }
+  }
+
+  async function superviseAsync(check: NonNullable<typeof healthCheck>): Promise<void> {
+    let failures = 0;
+    let attempts = 0;
+    let localUnhealthy = false;
+    while (
+      await waitAsync(
+        currentListener || localUnhealthy
+          ? PROBE_INTERVAL_MS
+          : Math.min(1_000 * 2 ** Math.min(attempts, 5), 30_000),
+        signal
+      )
+    ) {
+      await Promise.all([...retiredListeners].map(retired => closeAsync(retired, signal, false)));
+      if (signal.aborted) {
+        return;
+      }
+      if (currentListener && (await probeAsync(url, check))) {
+        if (failures > 0 || attempts > 0 || localUnhealthy) {
+          logger.info(`Ngrok tunnel ${domain} is healthy again.`);
+        }
+        failures = 0;
+        attempts = 0;
+        localUnhealthy = false;
+        continue;
+      }
+      if (signal.aborted) {
+        return;
+      }
+      if (!(await probeAsync(`http://127.0.0.1:${port}`, check))) {
+        if (!localUnhealthy && !signal.aborted) {
+          logger.warn(`Local service on port ${port} is unhealthy; waiting for it to recover.`);
+        }
+        localUnhealthy = true;
+        failures = 0;
+        continue;
+      }
+      localUnhealthy = false;
+      if (currentListener) {
+        failures++;
+        if (failures < FAILURE_THRESHOLD) {
+          continue;
+        }
+        logger.warn(`Ngrok tunnel ${domain} failed ${failures} health probes; reopening it.`);
+        await closeAsync(currentListener, signal);
+        currentListener = undefined;
+      }
+      if (signal.aborted) {
+        return;
+      }
+      attempts++;
+      try {
+        const reopened = await openAsync(/* forceNewSession */ true);
+        if (reopened.url() !== url) {
+          await closeAsync(reopened, signal);
+          throw new SystemError(
+            `Reopened ngrok tunnel for ${domain} returned a different public URL.`
+          );
+        }
+        currentListener = reopened;
+        failures = 0;
+      } catch (err) {
+        if (!signal.aborted && (attempts === 1 || attempts % 5 === 0)) {
+          logger.warn(
+            { err, attempt: attempts },
+            `Could not reopen ngrok tunnel ${domain}; will retry.`
+          );
+        }
+      }
+    }
+  }
+
+  const supervision = healthCheck
+    ? superviseAsync(healthCheck).catch(err => {
+        if (!signal.aborted) {
+          logger.warn({ err }, `Ngrok tunnel supervision stopped for ${domain}.`);
+        }
+      })
+    : Promise.resolve();
+  let stopTask: Promise<void> | undefined;
+  return {
+    url,
+    subdomainId,
+    stopAsync: () =>
+      (stopTask ??= (async () => {
+        controller.abort();
+        await withDeviceRunSessionTimeoutAsync(
+          { name: `Ngrok tunnel ${domain} stop`, timeoutMs: STOP_TIMEOUT_MS },
+          async stopSignal => {
+            await supervision;
+            if (currentListener) {
+              retiredListeners.add(currentListener);
+              currentListener = undefined;
+            }
+            await Promise.all([pendingOpen?.catch(() => {}), retireListenersAsync(stopSignal)]);
+            await retireListenersAsync(stopSignal);
+          }
+        );
+        releaseTarget();
+      })()),
+  };
+}
+
+function waitAsync(ms: number, signal: AbortSignal): Promise<boolean> {
+  if (signal.aborted) {
+    return Promise.resolve(false);
+  }
+  return new Promise(resolve => {
+    const onAbort = () => {
+      clearTimeout(timer);
+      resolve(false);
+    };
+    const timer = setTimeout(() => {
+      signal.removeEventListener('abort', onAbort);
+      resolve(true);
+    }, ms);
+    signal.addEventListener('abort', onAbort, { once: true });
+  });
+}
diff --git a/packages/build-tools/src/steps/utils/remoteDeviceRunSession.ts b/packages/build-tools/src/steps/utils/remoteDeviceRunSession.ts
index ce779b21d1..06d3a2b4c7 100644
--- a/packages/build-tools/src/steps/utils/remoteDeviceRunSession.ts
+++ b/packages/build-tools/src/steps/utils/remoteDeviceRunSession.ts
@@ -9,9 +9,7 @@ import {
   spawnAsync,
 } from '@expo/steps';
 import spawn from '@expo/turtle-spawn';
-import * as ngrok from '@ngrok/ngrok';
 import { z } from 'zod';
-import { randomBytes } from 'node:crypto';
 import fs from 'node:fs';
 import { createServer } from 'node:net';
 import path from 'node:path';
@@ -967,63 +965,7 @@ export async function findAvailablePortAsync(): Promise<number> {
   return address.port;
 }
 
-export type NgrokTunnelHandle = {
-  url: string;
-  subdomainId: string;
-  stopAsync: () => Promise<void>;
-};
-
-export async function startNgrokTunnelAsync({
-  port,
-  subdomainPrefix,
-  subdomainId: subdomainIdArg,
-  baseDomain,
-  authtoken,
-  rewriteHostHeader,
-  logger,
-}: {
-  port: number;
-  subdomainPrefix: string;
-  subdomainId?: string;
-  baseDomain: string;
-  authtoken: string;
-  rewriteHostHeader?: boolean;
-  logger: bunyan;
-}): Promise<NgrokTunnelHandle> {
-  const subdomainId = subdomainIdArg ?? randomBytes(16).toString('hex');
-  const domain = `${subdomainPrefix}-${subdomainId}.${baseDomain}`;
-  logger.info(`Starting ngrok tunnel ${domain} -> http://localhost:${port}.`);
-  // Run the ngrok agent in-process via the SDK; it keeps the session alive until
-  // the process exits, and the step blocks forever to hold it open.
-  const listener = await ngrok.forward({
-    addr: port,
-    authtoken,
-    domain,
-    ...(rewriteHostHeader ? { request_header_add: [`Host:localhost:${port}`] } : {}),
-  });
-  const url = listener.url();
-  if (!url) {
-    await listener.close();
-    throw new SystemError(`ngrok tunnel for ${domain} did not return a public URL.`);
-  }
-  let stopTask: Promise<void> | undefined;
-  return {
-    url,
-    subdomainId,
-    stopAsync: () =>
-      (stopTask ??= (async () => {
-        try {
-          await withDeviceRunSessionTimeoutAsync(
-            { name: 'Ngrok tunnel stop', timeoutMs: 4_000 },
-            async () => await listener.close()
-          );
-        } catch (error) {
-          logger.warn({ err: error }, `Could not stop ngrok tunnel ${domain}.`);
-          throw error;
-        }
-      })()),
-  };
-}
+export { type NgrokTunnelHandle, startNgrokTunnelAsync } from './ngrokTunnel';
 
 export async function waitForFileAsync<T>({
   filePath,