Sub2API v1.0 - AI API 网关（二开初始版本，基于上游 Wei-Shaw/sub2api）

backend/internal/service/gemini_native_signature_cleaner.go

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+package service
+
+import (
+	"encoding/json"
+
+	"github.com/Wei-Shaw/sub2api/internal/pkg/antigravity"
+)
+
+// CleanGeminiNativeThoughtSignatures 从 Gemini 原生 API 请求中替换 thoughtSignature 字段为 dummy 签名，
+// 以避免跨账号签名验证错误。
+//
+// 当粘性会话切换账号时（例如原账号异常、不可调度等），旧账号返回的 thoughtSignature
+// 会导致新账号的签名验证失败。通过替换为 dummy 签名，跳过签名验证。
+//
+// CleanGeminiNativeThoughtSignatures replaces thoughtSignature fields with dummy signature
+// in Gemini native API requests to avoid cross-account signature validation errors.
+//
+// When sticky session switches accounts (e.g., original account becomes unavailable),
+// thoughtSignatures from the old account will cause validation failures on the new account.
+// By replacing with dummy signature, we skip signature validation.
+func CleanGeminiNativeThoughtSignatures(body []byte) []byte {
+	if len(body) == 0 {
+		return body
+	}
+
+	// 解析 JSON
+	var data any
+	if err := json.Unmarshal(body, &data); err != nil {
+		// 如果解析失败，返回原始 body（可能不是 JSON 或格式不正确）
+		return body
+	}
+
+	// 递归替换 thoughtSignature 为 dummy 签名
+	replaced := replaceThoughtSignaturesRecursive(data)
+
+	// 重新序列化
+	result, err := json.Marshal(replaced)
+	if err != nil {
+		// 如果序列化失败，返回原始 body
+		return body
+	}
+
+	return result
+}
+
+// replaceThoughtSignaturesRecursive 递归遍历数据结构，将所有 thoughtSignature 字段替换为 dummy 签名
+func replaceThoughtSignaturesRecursive(data any) any {
+	switch v := data.(type) {
+	case map[string]any:
+		// 创建新的 map，替换 thoughtSignature 为 dummy 签名
+		result := make(map[string]any, len(v))
+		for key, value := range v {
+			// 替换 thoughtSignature 字段为 dummy 签名
+			if key == "thoughtSignature" {
+				result[key] = antigravity.DummyThoughtSignature
+				continue
+			}
+			// 递归处理嵌套结构
+			result[key] = replaceThoughtSignaturesRecursive(value)
+		}
+		return result
+
+	case []any:
+		// 递归处理数组中的每个元素
+		result := make([]any, len(v))
+		for i, item := range v {
+			result[i] = replaceThoughtSignaturesRecursive(item)
+		}
+		return result
+
+	default:
+		// 基本类型（string, number, bool, null）直接返回
+		return v
+	}
+}