feat: 默认客户端错误规则支持预置中文返回提示

[ding113]

现在的客户端错误规则，客户端看到的可能类似500 {"error": ["message": "Provider returned 500: Internal Server Error", "type": "internal_server_error"}}，这对用户不友好，因为无法知道命中了哪个规则，以及如何解决。

应该支持给错误规则设定返回语，并给所有默认错误规则预置返回语。比如上传的 PDF 页数超过 100 页，请减少页数后重试。
放置在message字段中。而type字段则应该返回实际命中的错误规则的类型。

[github-actions]

Thank you for this feature suggestion.

Analysis

Based on my investigation of the codebase, I've confirmed the current behavior and the feasibility of this enhancement.

Current Implementation:

The error rule system already supports response body override via the overrideResponse field in the database schema (src/drizzle/schema.ts:344-347). When an error matches a rule with overrideResponse configured, the proxy returns that custom response instead of the raw upstream error.

However, as you correctly identified, the default error rules defined in src/repository/error-rules.ts:292-479 do not currently include any overrideResponse values. This means users see raw upstream errors like:

{"error": {"message": "Provider returned 500: Internal Server Error", "type": "internal_server_error"}}

Existing Infrastructure:

The system already supports three error response formats (src/repository/error-rules.ts:14-58):

1. Claude format: { type: "error", error: { type: "...", message: "..." } }
2. Gemini format: { error: { code: number, message: "...", status: "..." } }
3. OpenAI format: { error: { message: "...", type: "..." } }

The error handler (src/app/v1/_lib/proxy/error-handler.ts:116-183) properly processes these override responses when configured.

Relevant Code Locations:

• Default rules definition: src/repository/error-rules.ts:292-479
• Error override response types: src/repository/error-rules.ts:14-58
• Error handler override logic: src/app/v1/_lib/proxy/error-handler.ts:88-207
• Database schema: src/drizzle/schema.ts:335-361

Implementation Considerations:

1. Add overrideResponse with Chinese user-friendly messages to each default rule in DEFAULT_ERROR_RULES
2. The error type field should reflect the matched rule's category value (e.g., pdf_limit, prompt_limit, content_filter)
3. Consider whether to use Claude, Gemini, or OpenAI error format as the default (or make it configurable)

Example for PDF limit rule (current):

{
  pattern: "PDF has too many pages|maximum of.*PDF pages",
  category: "pdf_limit",
  description: "PDF page limit exceeded",
  matchType: "regex" as const,
  isDefault: true,
  isEnabled: true,
  priority: 80,
}

Example with override (proposed):

{
  pattern: "PDF has too many pages|maximum of.*PDF pages",
  category: "pdf_limit",
  description: "PDF page limit exceeded",
  matchType: "regex" as const,
  isDefault: true,
  isEnabled: true,
  priority: 80,
  overrideResponse: {
    type: "error",
    error: {
      type: "pdf_limit",
      message: "上传的 PDF 页数超过 100 页，请减少页数后重试"
    }
  },
}

This is a well-scoped enhancement that leverages existing infrastructure.

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Automated response from Claude AI