Proxy mode causes 500 "request body tampered" error with upstream providers enforcing strict CLI fingerprinting

[seehowthehunt]

Self Checks / 自检

• I have read the FAQ section in README.
  我已阅读 README 中的常见问题。

• I have searched for existing issues, including closed ones.
  我已搜索过已有的 Issue，包括已关闭的。

CC Switch Version / 版本号

v3.12.3

Operating System / 操作系统

Windows

Related App / 涉及应用

Claude Code

Steps to Reproduce / 重现步骤

When proxy mode is enabled in cc-switch, running the claude CLI from a standard system terminal results in a 500 error from certain upstream API providers. However, running it via the cc-switch "open terminal" button works perfectly under the exact same proxy settings.
Steps:

1. Enable cc-switch proxy mode.
2. Open a regular system terminal (e.g., standard PowerShell, CMD, or Git Bash) — do not use the cc-switch "open terminal" button.
3. Run claude and send a prompt.

Expected Behavior / 期望行为

The request succeeds normally and Claude responds.

Actual Behavior / 实际行为

Repeatedly throws the following 500 error:
500 {"error":{"type":"request_fail","upstream_error":{"error":{"message":"您的请求体疑似被篡改，请使用我们的官方分发平台。(Your request body appears to have been tampered with. Please use our official distribution platform.) (request_ori_id: ca3d10e3-d3ab-4fc2-9dbf-b6e31688de07) (request id: 202604040134081245928442FNadTjQ)","type":"<nil>"},"type":"error"}},"type":"error"}

Additional Context / 补充信息

Isolation tests:

• Disabling proxy mode → Works fine.
• Using the cc-switch "open terminal" button (with proxy mode ON) → Works fine.
• Using standard API endpoints (like DeepSeek) with proxy mode ON → Works fine. The issue only occurs with specific upstream gateways (like Cubence and Packy).