Any web_fetch: TypeError: fetch failed

### Describe the bug

Prompt: what's the html title on https://example.com

Always getting: TypeError: fetch failed

This is not about a lack of proxy settings, environment variables. Copilot has no problem access models, or logging the user in, etc.

Every single web_fetch tool call fails, no matter what website.

curl commands from the same terminal work, other simple node apps work. Even getting Copilot itself to test/troubleshoot, all the network commands it runs, work, whether node apps, curl, powershell, etc. Something is deeply broken in web_fetch and the error reporting is completely useless. I suspect it's related to a corporate proxy, but this is a web_fetch only problem. Please add something useful the debug logs. Please, fix this, once and for all. This lack of logging going on from day one. "Fetch failed" isn't good enough, especially at debug or all level.

Seems you have put in 100 times more effort in logging information about your own telemetry requests. Seems like misguided priorities.

These are set, and should not be necessary anyway:

NODE_TLS_REJECT_UNAUTHORIZED=0
NODE_USE_ENV_PROXY=1
NODE_USE_SYSTEM_CA=1

And these are set and correct:

HTTPS_PROXY=http://xxx.xxx.xxx.xxx:8082
HTTP_PROXY=http://xxx.xxx.xxx.xxx:8082

As seen in the logs:

2026-06-26T16:12:55.063Z [INFO] Proxy configuration: HTTP_PROXY=http://xxx.xxx.xxx.xxx:8082, HTTPS_PROXY=http://xxx.xxx.xxx.xxx:8082, NO_PROXY=localhost,127.0.0.1,*.xxx.xxx,192.168.*,xxx.ie

### Affected version
GitHub Copilot CLI 1.0.65
Windows 11

_No response_

### Steps to reproduce the behavior

Run the prompt.

### Expected behavior

Working response + proper logging in failure case.

### Additional context

_No response_

首先在 Windows 11 上的 GitHub Copilot CLI 1.0.65 中針對 https://example.com 重現 web_fetch prompt，然後檢查 web_fetch 的失敗路徑及其偵錯輸出。當請求成功，或失敗訊息回報有用的原因而不只是「TypeError: fetch failed」時，即表示完成。

由索引模型根據 Issue 內容生成。