499 client_closed_request errors during web-search tool usage

Description

When using the web-search tool (or when the model invokes web search during a conversation), the request fails with a 499 status code and client_closed_request error. The upstream error message is "client closed request during web-search".

Reproduction

1. Use a model that triggers web search (e.g. qwen3.8-max-preview via alibaba-token-plan-intl provider)
2. Send a request that requires web search
3. The request fails with status 499

Log entry

{
  "requestId": "ocx-ms2c6sko-10n",
  "timestamp": 1785102920232,
  "model": "qwen3.8-max-preview",
  "provider": "alibaba-token-plan-intl",
  "requestedModel": "alibaba-token-plan-intl/qwen3.8-max-preview",
  "requestedEffort": "high",
  "configuredServiceTier": "default",
  "resolvedModel": "qwen3.8-max-preview",
  "status": 499,
  "durationMs": 304120,
  "errorCode": "client_closed_request",
  "terminalStatus": "failed",
  "closeReason": "client_cancel",
  "upstreamError": "client closed request during web-search",
  "usageStatus": "unreported",
  "displayMetrics": {
    "tokPerSecond": { "kind": "unavailable", "reason": "usage_missing" },
    "cost": { "kind": "unavailable", "reason": "usage_missing" }
  }
}

Key details

• Status: 499 (client closed request)
• Error code: client_closed_request
• Close reason: client_cancel
• Upstream error: client closed request during web-search
• Duration: ~304s before failure
• Provider: alibaba-token-plan-intl
• Model: qwen3.8-max-preview

The request appears to be cancelled by the client while the upstream provider is still processing the web search, resulting in a 499 rather than a successful response.