> ## Documentation Index
> Fetch the complete documentation index at: https://tbd-6fc993ce-hypeship-add-antigravity-mcp-client-doc.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# Proxy Errors

When a request cannot be completed at the proxy layer, Kernel serves a branded error page and sets the `X-Kernel-Proxy-Error` response header to a typed code.

The header is set on every branded proxy-layer error response, including WebSocket and subresource requests where the page body never renders. The status is always `502`, including for timeouts, so use the header rather than the status to decide what went wrong.

## Error codes

| Code                           | What happened                                                                                                                                                | Retry                                                                                                                                                                                                                                                                             |
| ------------------------------ | ------------------------------------------------------------------------------------------------------------------------------------------------------------ | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| `upstream_timeout`             | Kernel's connection to the upstream proxy provider did not complete within its deadline.                                                                     | Yes                                                                                                                                                                                                                                                                               |
| `provider_unreachable`         | The upstream proxy provider could not reach the destination.                                                                                                 | Yes                                                                                                                                                                                                                                                                               |
| `upstream_connect_failed`      | The connection to the destination failed.                                                                                                                    | Yes                                                                                                                                                                                                                                                                               |
| `upstream_dns_failure`         | The upstream proxy host could not be resolved.                                                                                                               | Yes                                                                                                                                                                                                                                                                               |
| `origin_tls_timeout`           | The proxy reached the destination, but the destination did not complete its TLS handshake in time.                                                           | Yes                                                                                                                                                                                                                                                                               |
| `restricted_route_unavailable` | The destination requires a specialized egress route and Kernel could not build one. Kernel will not fall back to a provider known to reject the destination. | Yes, except on `.gov` destinations. There, create a new residential proxy with no targeting, country-only targeting, or a U.S. state, confirm it with [`POST /proxies/{id}/check`](https://kernel.sh/docs/api-reference/proxies/check-proxy-health), then use it for the session. |
| `proxy_unavailable`            | A failure inside Kernel's own proxy layer, not your automation or the destination.                                                                           | Yes                                                                                                                                                                                                                                                                               |
| `origin_response_incomplete`   | The destination closed the connection before sending a complete response.                                                                                    | Only if safe. The destination may have received the request, so retry only when repeating the action cannot cause duplicate changes.                                                                                                                                              |
| `provider_rejected`            | The upstream proxy provider rejected the request before the destination connection was established.                                                          | No. Try a different proxy or proxy type, and check the credentials on a [custom proxy](/proxies/custom).                                                                                                                                                                          |
| `provider_blacklisted`         | The upstream proxy provider blocks this destination.                                                                                                         | No. Try a different proxy or proxy type, or disable the proxy for this destination.                                                                                                                                                                                               |
| `destination_blocked`          | Kernel policy blocks connections to internal and private addresses.                                                                                          | No. Use a public destination address.                                                                                                                                                                                                                                             |

## Recovering from a proxy error

An agent driving the browser usually recovers on its own, because a failed step leads it to re-navigate. When a person is driving the browser instead — for example through an embedded [live view](/browsers/live-view) — nobody re-navigates, and a transient provider failure becomes a dead end.

Read the header on a `502` and retry the navigation so those failures never reach the person holding the browser:

```typescript Typescript/Javascript theme={null}
const RETRYABLE = new Set([
  'upstream_timeout',
  'provider_unreachable',
  'upstream_connect_failed',
  'upstream_dns_failure',
  'origin_tls_timeout',
  'restricted_route_unavailable',
  'proxy_unavailable',
]);

async function navigate(page, url, attempts = 3) {
  for (let attempt = 1; ; attempt++) {
    const response = await page.goto(url);
    const code = response?.headers()['x-kernel-proxy-error'];

    if (!code || !RETRYABLE.has(code) || attempt === attempts) return response;

    await new Promise((resolve) => setTimeout(resolve, 1000 * attempt));
  }
}
```

`origin_response_incomplete` is deliberately absent from that set. The destination may have already acted on the request, so retrying it automatically can duplicate a submission.

## Observing proxy errors after the fact

Proxy failures are also reported as `proxy_error` [browser telemetry](/browsers/telemetry/overview) events in the `network` category. Use the header to recover in the moment, and telemetry to attribute failures per session and per URL afterwards.

The telemetry `code` does not cover every code above. `origin_response_incomplete` is not reported as a `proxy_error` event, and a header value the browser image does not recognize is reported as `unknown`, with the original value in `raw_code`. Read the header when you need the exact code.