[BUG] HuggingFace acceleration returns 502 Bad Gateway, local proxy receives request but upstream origin fails

Checklist

• I have searched existing issues, no similar issue found
• I have read the documentation
• I am using the latest version, problem persists
• Official release, no modified binary / installation files

Describe the bug

When enabling acceleration for all huggingface.* related domains, the local proxy successfully receives HTTP/2 requests from the browser. But requests forwarded to the upstream huggingface.co return 502 Bad Gateway.

The browser renders a completely blank page. CSS, JavaScript and favicon cannot be loaded. It is impossible to log in or access HuggingFace competition pages.

Troubleshooting I have performed:

• All hugging‑related domains including cdn.huggingface.co are selected for acceleration
• Watt Toolkit root certificate has been installed
• Multiple acceleration nodes have been tried
• Tested in browser incognito mode, ad‑block extensions disabled

Downloading models in Python with hf‑mirror.com works correctly. However, the mirror cannot replace the official website for account login and competition submission which require origin‑site authentication.

Expected behavior The proxy forwards requests normally and the page renders completely.

Actual behavior All requests to huggingface.co get 502 responses, browser page stays blank.

Reproduce Steps

1. Open Watt Toolkit, navigate to Network Acceleration, search for hugging, select all huggingface‑related domains.
2. Click "Start Acceleration".
3. Open browser incognito tab, visit https://huggingface.co/, hard refresh with Ctrl+F5.
4. Page remains blank. Check application logs, multiple 502 responses can be observed.

Logs

Log path: %Tmp%\Steam++\Logs

Environment

• CPU Arch: x64
• OS Version: Windows 10 Pro 19045.3570
• Download source: GitHub Releases
• Toolkit version: 3.1.0 for Windows 10 x64
• Self‑contained runtime: Yes

Additional note Local HTTP/2 handshake completes successfully. The failure happens between local proxy and HuggingFace origin server. Switching acceleration nodes cannot resolve this issue stably.