[Bug] 使用 OpenAI 的 GPT-5，持续遇到 Gateway time-out Error code 504

### 📦 Deployment Method

Vercel

### 📌 Version

v2.16.1

### 💻 Operating System

Windows

### 📌 System Version

Windows 11, version 24H2

### 🌐 Browser

Chrome

### 📌 Browser Version

138.0.7204.169

### 🐛 Bug Description

使用 OpenAI 的 gpt-5 时（在 versel 上部署，接 API Key），会报 `504: Gateway time-out` ，然而用别的模型都不会有这样的报错：
```
{
"error": {
"code": "504",
"message": "An error occurred with your deployment"
}
}
```
尝试了将 vercel 的 Function Max Duration 调到 60s，仍然没有变化。然而，有时如果输入 “test”“hello”这样简短的问题，则不会遇到错误，而是能正常回答。

### 📷 Recurrence Steps

使用 OpenAI 的 GPT-5，询问比较长的问题。

### 🚦 Expected Behavior

_No response_

### 📝 Additional Information

_No response_

Start by reproducing the issue on a Vercel deployment running v2.16.1 with OpenAI GPT-5, using a long prompt and then a short prompt such as “test” or “hello.” Compare the behavior with other models and with Function Max Duration set to 60 seconds. Done means identifying whether the timeout is caused by the application or the deployment and documenting a verified fix or limitation.

Written by the indexing model from the issue text.