refactor(gateway): remove parsed request object graphs

Keep large gateway payloads as raw body ranges and bind OpenAI parsed-body caches to the body bytes so failover and mapping do not reuse stale mutable state.

backend/internal/handler/gateway_handler.go

@@ -747,10 +747,10 @@ func (h *GatewayHandler) Messages(c *gin.Context) {
 			// 应用渠道模型映射到请求
 			if channelMapping.Mapped {
 				parsedReq.Model = channelMapping.MappedModel
-				parsedReq.Body.Replace(h.gatewayService.ReplaceModelInBody(parsedReq.Body.Bytes(), channelMapping.MappedModel))
+				parsedReq.ReplaceBody(h.gatewayService.ReplaceModelInBody(parsedReq.Body.Bytes(), channelMapping.MappedModel))
 			}
 			// Bedrock CC 兼容：渠道模型映射后，清理 Anthropic API 专有字段、注入 Bedrock 必需字段
-			parsedReq.Body.Replace(h.gatewayService.ApplyBedrockCCCompat(c.Request.Context(), parsedReq.Body.Bytes(), parsedReq.Model, account, apiKey.GroupID))
+			parsedReq.ReplaceBody(h.gatewayService.ApplyBedrockCCCompat(c.Request.Context(), parsedReq.Body.Bytes(), parsedReq.Model, account, apiKey.GroupID))
 			body = parsedReq.Body.Bytes()
 
 			// 转发请求 - 根据账号平台分流

backend/internal/handler/gateway_helper.go

@@ -74,8 +74,12 @@ func claudeCodeBodyMapFromParsedRequest(parsedReq *service.ParsedRequest) map[st
 	bodyMap := map[string]any{
 		"model": parsedReq.Model,
 	}
-	if parsedReq.System != nil || parsedReq.HasSystem {
+	if parsedReq.HasSystem {
-		bodyMap["system"] = parsedReq.System
+		if system, ok := parsedReq.SystemValue(); ok {
+			bodyMap["system"] = system
+		} else {
+			bodyMap["system"] = nil
+		}
 	}
 	if parsedReq.MetadataUserID != "" {
 		bodyMap["metadata"] = map[string]any{"user_id": parsedReq.MetadataUserID}
@@ -87,11 +91,9 @@ func claudeCodeBodyMapFromContextCache(c *gin.Context) map[string]any {
 	if c == nil {
 		return nil
 	}
-	if cached, ok := c.Get(service.OpenAIParsedRequestBodyKey); ok {
+	if bodyMap := service.CachedOpenAIParsedRequestBody(c); bodyMap != nil {
-		if bodyMap, ok := cached.(map[string]any); ok {
 		return bodyMap
 	}
-	}
 	if cached, ok := c.Get(claudeCodeParsedRequestContextKey); ok {
 		switch v := cached.(type) {
 		case *service.ParsedRequest:

backend/internal/handler/gateway_helper_hotpath_test.go

@@ -185,13 +185,8 @@ func TestSetClaudeCodeClientContext_ReuseParsedRequestAndContextCache(t *testing
 		c.Request.Header.Set("anthropic-beta", "message-batches-2024-09-24")
 		c.Request.Header.Set("anthropic-version", "2023-06-01")
 
-		parsedReq := &service.ParsedRequest{
+		parsedReq, err := service.ParseGatewayRequest(service.NewRequestBodyRef(validClaudeCodeBodyJSON()), "")
-			Model: "claude-3-5-sonnet-20241022",
+		require.NoError(t, err)
-			System: []any{
-				map[string]any{"text": "You are Claude Code, Anthropic's official CLI for Claude."},
-			},
-			MetadataUserID: "user_aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa_account__session_aaaaaaaa-aaaa-aaaa-aaaa-aaaaaaaaaaaa",
-		}
 
 		// body 非法 JSON，如果函数复用 parsedReq 成功则仍应判定为 Claude Code。
 		SetClaudeCodeClientContext(c, []byte(`{invalid`), parsedReq)
@@ -204,7 +199,7 @@ func TestSetClaudeCodeClientContext_ReuseParsedRequestAndContextCache(t *testing
 		c.Request.Header.Set("X-App", "claude-code")
 		c.Request.Header.Set("anthropic-beta", "message-batches-2024-09-24")
 		c.Request.Header.Set("anthropic-version", "2023-06-01")
-		c.Set(service.OpenAIParsedRequestBodyKey, map[string]any{
+		service.CacheOpenAIParsedRequestBody(c, []byte(`{invalid`), map[string]any{
 			"model": "claude-3-5-sonnet-20241022",
 			"system": []any{
 				map[string]any{"text": "You are Claude Code, Anthropic's official CLI for Claude."},

backend/internal/handler/openai_gateway_handler.go

@@ -954,7 +954,7 @@ func (h *OpenAIGatewayHandler) validateFunctionCallOutputRequest(c *gin.Context,
 		return true
 	}
 
-	c.Set(service.OpenAIParsedRequestBodyKey, reqBody)
+	service.CacheOpenAIParsedRequestBody(c, body, reqBody)
 	validation := service.ValidateFunctionCallOutputContext(reqBody)
 	if !validation.HasFunctionCallOutput {
 		return true

backend/internal/service/anthropic_session.go

@@ -4,6 +4,8 @@ import (
 	"encoding/json"
 	"strings"
 	"time"
+
+	"github.com/tidwall/gjson"
 )
 
 // Anthropic 会话 Fallback 相关常量
@@ -30,30 +32,39 @@ func BuildAnthropicDigestChain(parsed *ParsedRequest) string {
 
 	var parts []string
 
-	// 1. system prompt
+	if systemRaw := parsed.SystemRaw(); len(systemRaw) > 0 && string(systemRaw) != "null" {
-	if parsed.System != nil {
+		parts = append(parts, "s:"+shortHash(canonicalAnthropicDigestJSON(systemRaw)))
-		systemData, _ := json.Marshal(parsed.System)
-		if len(systemData) > 0 && string(systemData) != "null" {
-			parts = append(parts, "s:"+shortHash(systemData))
-		}
 	}
 
-	// 2. messages
+	messages := parsed.MessagesRaw()
-	for _, msg := range parsed.Messages {
+	if len(messages) > 0 {
-		msgMap, ok := msg.(map[string]any)
+		gjson.ParseBytes(messages).ForEach(func(_, msg gjson.Result) bool {
-		if !ok {
+			prefix := rolePrefix(msg.Get("role").String())
-			continue
+			content := msg.Get("content")
-		}
+			parts = append(parts, prefix+":"+shortHash(canonicalAnthropicDigestJSON([]byte(content.Raw))))
-		role, _ := msgMap["role"].(string)
+			return true
-		prefix := rolePrefix(role)
+		})
-		content := msgMap["content"]
-		contentData, _ := json.Marshal(content)
-		parts = append(parts, prefix+":"+shortHash(contentData))
 	}
 
 	return strings.Join(parts, "-")
 }
 
+// canonicalAnthropicDigestJSON 保持 digest 对 JSON key 顺序和空白不敏感。
+func canonicalAnthropicDigestJSON(raw []byte) []byte {
+	if len(raw) == 0 {
+		return raw
+	}
+	var value any
+	if err := json.Unmarshal(raw, &value); err != nil {
+		return raw
+	}
+	canonical, err := json.Marshal(value)
+	if err != nil {
+		return raw
+	}
+	return canonical
+}
+
 // rolePrefix 将 Anthropic 的 role 映射为单字符前缀
 func rolePrefix(role string) string {
 	switch role {

backend/internal/service/anthropic_session_test.go

@@ -1,3 +1,5 @@
+//go:build unit
+
 package service
 
 import (
@@ -5,6 +7,15 @@ import (
 	"testing"
 )
 
+func mustParseAnthropicDigestRequest(t *testing.T, body string) *ParsedRequest {
+	t.Helper()
+	parsed, err := ParseGatewayRequest(NewRequestBodyRef([]byte(body)), "")
+	if err != nil {
+		t.Fatalf("ParseGatewayRequest failed: %v", err)
+	}
+	return parsed
+}
+
 func TestBuildAnthropicDigestChain_NilRequest(t *testing.T) {
 	result := BuildAnthropicDigestChain(nil)
 	if result != "" {
@@ -13,9 +24,7 @@ func TestBuildAnthropicDigestChain_NilRequest(t *testing.T) {
 }
 
 func TestBuildAnthropicDigestChain_EmptyMessages(t *testing.T) {
-	parsed := &ParsedRequest{
+	parsed := mustParseAnthropicDigestRequest(t, `{"messages":[]}`)
-		Messages: []any{},
-	}
 	result := BuildAnthropicDigestChain(parsed)
 	if result != "" {
 		t.Errorf("expected empty string for empty messages, got: %s", result)
@@ -23,11 +32,7 @@ func TestBuildAnthropicDigestChain_EmptyMessages(t *testing.T) {
 }
 
 func TestBuildAnthropicDigestChain_SingleUserMessage(t *testing.T) {
-	parsed := &ParsedRequest{
+	parsed := mustParseAnthropicDigestRequest(t, `{"messages":[{"role":"user","content":"hello"}]}`)
-		Messages: []any{
-			map[string]any{"role": "user", "content": "hello"},
-		},
-	}
 	result := BuildAnthropicDigestChain(parsed)
 	parts := splitChain(result)
 	if len(parts) != 1 {
@@ -39,12 +44,7 @@ func TestBuildAnthropicDigestChain_SingleUserMessage(t *testing.T) {
 }
 
 func TestBuildAnthropicDigestChain_UserAndAssistant(t *testing.T) {
-	parsed := &ParsedRequest{
+	parsed := mustParseAnthropicDigestRequest(t, `{"messages":[{"role":"user","content":"hello"},{"role":"assistant","content":"hi there"}]}`)
-		Messages: []any{
-			map[string]any{"role": "user", "content": "hello"},
-			map[string]any{"role": "assistant", "content": "hi there"},
-		},
-	}
 	result := BuildAnthropicDigestChain(parsed)
 	parts := splitChain(result)
 	if len(parts) != 2 {
@@ -59,12 +59,7 @@ func TestBuildAnthropicDigestChain_UserAndAssistant(t *testing.T) {
 }
 
 func TestBuildAnthropicDigestChain_WithSystemString(t *testing.T) {
-	parsed := &ParsedRequest{
+	parsed := mustParseAnthropicDigestRequest(t, `{"system":"You are a helpful assistant","messages":[{"role":"user","content":"hello"}]}`)
-		System: "You are a helpful assistant",
-		Messages: []any{
-			map[string]any{"role": "user", "content": "hello"},
-		},
-	}
 	result := BuildAnthropicDigestChain(parsed)
 	parts := splitChain(result)
 	if len(parts) != 2 {
@@ -79,14 +74,7 @@ func TestBuildAnthropicDigestChain_WithSystemString(t *testing.T) {
 }
 
 func TestBuildAnthropicDigestChain_WithSystemContentBlocks(t *testing.T) {
-	parsed := &ParsedRequest{
+	parsed := mustParseAnthropicDigestRequest(t, `{"system":[{"type":"text","text":"You are a helpful assistant"}],"messages":[{"role":"user","content":"hello"}]}`)
-		System: []any{
-			map[string]any{"type": "text", "text": "You are a helpful assistant"},
-		},
-		Messages: []any{
-			map[string]any{"role": "user", "content": "hello"},
-		},
-	}
 	result := BuildAnthropicDigestChain(parsed)
 	parts := splitChain(result)
 	if len(parts) != 2 {
@@ -100,74 +88,33 @@ func TestBuildAnthropicDigestChain_WithSystemContentBlocks(t *testing.T) {
 func TestBuildAnthropicDigestChain_ConversationPrefixRelationship(t *testing.T) {
 	// 核心测试：验证对话增长时链的前缀关系
 	// 上一轮的完整链一定是下一轮链的前缀
-	system := "You are a helpful assistant"
+	round1 := mustParseAnthropicDigestRequest(t, `{"system":"You are a helpful assistant","messages":[{"role":"user","content":"hello"}]}`)
-
-	// 第 1 轮: system + user
-	round1 := &ParsedRequest{
-		System: system,
-		Messages: []any{
-			map[string]any{"role": "user", "content": "hello"},
-		},
-	}
 	chain1 := BuildAnthropicDigestChain(round1)
 
-	// 第 2 轮: system + user + assistant + user
+	round2 := mustParseAnthropicDigestRequest(t, `{"system":"You are a helpful assistant","messages":[{"role":"user","content":"hello"},{"role":"assistant","content":"hi there"},{"role":"user","content":"how are you?"}]}`)
-	round2 := &ParsedRequest{
-		System: system,
-		Messages: []any{
-			map[string]any{"role": "user", "content": "hello"},
-			map[string]any{"role": "assistant", "content": "hi there"},
-			map[string]any{"role": "user", "content": "how are you?"},
-		},
-	}
 	chain2 := BuildAnthropicDigestChain(round2)
 
-	// 第 3 轮: system + user + assistant + user + assistant + user
+	round3 := mustParseAnthropicDigestRequest(t, `{"system":"You are a helpful assistant","messages":[{"role":"user","content":"hello"},{"role":"assistant","content":"hi there"},{"role":"user","content":"how are you?"},{"role":"assistant","content":"I'm doing well"},{"role":"user","content":"great"}]}`)
-	round3 := &ParsedRequest{
-		System: system,
-		Messages: []any{
-			map[string]any{"role": "user", "content": "hello"},
-			map[string]any{"role": "assistant", "content": "hi there"},
-			map[string]any{"role": "user", "content": "how are you?"},
-			map[string]any{"role": "assistant", "content": "I'm doing well"},
-			map[string]any{"role": "user", "content": "great"},
-		},
-	}
 	chain3 := BuildAnthropicDigestChain(round3)
 
 	t.Logf("Chain1: %s", chain1)
 	t.Logf("Chain2: %s", chain2)
 	t.Logf("Chain3: %s", chain3)
 
-	// chain1 是 chain2 的前缀
 	if !strings.HasPrefix(chain2, chain1) {
 		t.Errorf("chain1 should be prefix of chain2:\n  chain1: %s\n  chain2: %s", chain1, chain2)
 	}
-
-	// chain2 是 chain3 的前缀
 	if !strings.HasPrefix(chain3, chain2) {
 		t.Errorf("chain2 should be prefix of chain3:\n  chain2: %s\n  chain3: %s", chain2, chain3)
 	}
-
-	// chain1 也是 chain3 的前缀（传递性）
 	if !strings.HasPrefix(chain3, chain1) {
 		t.Errorf("chain1 should be prefix of chain3:\n  chain1: %s\n  chain3: %s", chain1, chain3)
 	}
 }
 
 func TestBuildAnthropicDigestChain_DifferentSystemProducesDifferentChain(t *testing.T) {
-	parsed1 := &ParsedRequest{
+	parsed1 := mustParseAnthropicDigestRequest(t, `{"system":"System A","messages":[{"role":"user","content":"hello"}]}`)
-		System: "System A",
+	parsed2 := mustParseAnthropicDigestRequest(t, `{"system":"System B","messages":[{"role":"user","content":"hello"}]}`)
-		Messages: []any{
-			map[string]any{"role": "user", "content": "hello"},
-		},
-	}
-	parsed2 := &ParsedRequest{
-		System: "System B",
-		Messages: []any{
-			map[string]any{"role": "user", "content": "hello"},
-		},
-	}
 
 	chain1 := BuildAnthropicDigestChain(parsed1)
 	chain2 := BuildAnthropicDigestChain(parsed2)
@@ -176,7 +123,6 @@ func TestBuildAnthropicDigestChain_DifferentSystemProducesDifferentChain(t *test
 		t.Error("Different system prompts should produce different chains")
 	}
 
-	// 但 user 部分的 hash 应该相同
 	parts1 := splitChain(chain1)
 	parts2 := splitChain(chain2)
 	if parts1[1] != parts2[1] {
@@ -185,20 +131,8 @@ func TestBuildAnthropicDigestChain_DifferentSystemProducesDifferentChain(t *test
 }
 
 func TestBuildAnthropicDigestChain_DifferentContentProducesDifferentChain(t *testing.T) {
-	parsed1 := &ParsedRequest{
+	parsed1 := mustParseAnthropicDigestRequest(t, `{"messages":[{"role":"user","content":"hello"},{"role":"assistant","content":"ORIGINAL reply"},{"role":"user","content":"next"}]}`)
-		Messages: []any{
+	parsed2 := mustParseAnthropicDigestRequest(t, `{"messages":[{"role":"user","content":"hello"},{"role":"assistant","content":"TAMPERED reply"},{"role":"user","content":"next"}]}`)
-			map[string]any{"role": "user", "content": "hello"},
-			map[string]any{"role": "assistant", "content": "ORIGINAL reply"},
-			map[string]any{"role": "user", "content": "next"},
-		},
-	}
-	parsed2 := &ParsedRequest{
-		Messages: []any{
-			map[string]any{"role": "user", "content": "hello"},
-			map[string]any{"role": "assistant", "content": "TAMPERED reply"},
-			map[string]any{"role": "user", "content": "next"},
-		},
-	}
 
 	chain1 := BuildAnthropicDigestChain(parsed1)
 	chain2 := BuildAnthropicDigestChain(parsed2)
@@ -209,24 +143,16 @@ func TestBuildAnthropicDigestChain_DifferentContentProducesDifferentChain(t *tes
 
 	parts1 := splitChain(chain1)
 	parts2 := splitChain(chain2)
-	// 第一个 user message hash 应该相同
 	if parts1[0] != parts2[0] {
 		t.Error("First user message hash should be the same")
 	}
-	// assistant reply hash 应该不同
 	if parts1[1] == parts2[1] {
 		t.Error("Assistant reply hash should differ")
 	}
 }
 
 func TestBuildAnthropicDigestChain_Deterministic(t *testing.T) {
-	parsed := &ParsedRequest{
+	parsed := mustParseAnthropicDigestRequest(t, `{"system":"test system","messages":[{"role":"user","content":"hello"},{"role":"assistant","content":"hi"}]}`)
-		System: "test system",
-		Messages: []any{
-			map[string]any{"role": "user", "content": "hello"},
-			map[string]any{"role": "assistant", "content": "hi"},
-		},
-	}
 
 	chain1 := BuildAnthropicDigestChain(parsed)
 	chain2 := BuildAnthropicDigestChain(parsed)
@@ -236,6 +162,18 @@ func TestBuildAnthropicDigestChain_Deterministic(t *testing.T) {
 	}
 }
 
+func TestBuildAnthropicDigestChain_CanonicalJSON(t *testing.T) {
+	parsed1 := mustParseAnthropicDigestRequest(t, `{"system":[{"type":"text","text":"system"}],"messages":[{"role":"user","content":{"type":"text","text":"hello"}}]}`)
+	parsed2 := mustParseAnthropicDigestRequest(t, `{"system":[{"text":"system","type":"text"}],"messages":[{"role":"user","content":{"text":"hello","type":"text"}}]}`)
+
+	chain1 := BuildAnthropicDigestChain(parsed1)
+	chain2 := BuildAnthropicDigestChain(parsed2)
+
+	if chain1 != chain2 {
+		t.Errorf("semantically equivalent JSON should produce same chain: %s vs %s", chain1, chain2)
+	}
+}
+
 func TestGenerateAnthropicDigestSessionKey(t *testing.T) {
 	tests := []struct {
 		name       string
@@ -278,7 +216,6 @@ func TestGenerateAnthropicDigestSessionKey(t *testing.T) {
 		})
 	}
 
-	// 验证不同 uuid 产生不同 sessionKey
 	t.Run("different uuid different key", func(t *testing.T) {
 		hash := "sameprefix123456"
 		result1 := GenerateAnthropicDigestSessionKey(hash, "uuid0001-session-a")
@@ -297,18 +234,7 @@ func TestAnthropicSessionTTL(t *testing.T) {
 }
 
 func TestBuildAnthropicDigestChain_ContentBlocks(t *testing.T) {
-	// 测试 content 为 content blocks 数组的情况
+	parsed := mustParseAnthropicDigestRequest(t, `{"messages":[{"role":"user","content":[{"type":"text","text":"describe this image"},{"type":"image","source":{"type":"base64"}}]}]}`)
-	parsed := &ParsedRequest{
-		Messages: []any{
-			map[string]any{
-				"role": "user",
-				"content": []any{
-					map[string]any{"type": "text", "text": "describe this image"},
-					map[string]any{"type": "image", "source": map[string]any{"type": "base64"}},
-				},
-			},
-		},
-	}
 	result := BuildAnthropicDigestChain(parsed)
 	parts := splitChain(result)
 	if len(parts) != 1 {

backend/internal/service/gateway_oauth_metadata_test.go

@@ -14,8 +14,6 @@ func TestBuildOAuthMetadataUserID_FallbackWithoutAccountUUID(t *testing.T) {
 		Model:          "claude-sonnet-4-5",
 		Stream:         true,
 		MetadataUserID: "",
-		System:         nil,
-		Messages:       nil,
 	}
 
 	account := &Account{

backend/internal/service/gateway_request.go

@@ -51,6 +51,12 @@ type SessionContext struct {
 	APIKeyID  int64
 }
 
+type jsonRange struct {
+	start int        // 原始请求体中的起始偏移（闭区间）
+	end   int        // 原始请求体中的结束偏移（开区间）
+	kind  gjson.Type // JSON 值类型，用于调用方做轻量分支
+}
+
 type RequestBodyRef struct {
 	data []byte
 }
@@ -80,6 +86,76 @@ func (b *RequestBodyRef) Replace(data []byte) {
 	b.data = data
 }
 
+func missingJSONRange() jsonRange {
+	return jsonRange{start: -1, end: -1}
+}
+
+func rangeFromResult(r gjson.Result) jsonRange {
+	if r.Raw == "" || r.Index <= 0 {
+		return missingJSONRange()
+	}
+	end := r.Index + len(r.Raw)
+	if end < r.Index {
+		return missingJSONRange()
+	}
+	return jsonRange{start: r.Index, end: end, kind: r.Type}
+}
+
+func (r jsonRange) exists() bool {
+	return r.start >= 0 && r.end >= r.start
+}
+
+func clearGatewayRequestRanges(parsed *ParsedRequest) {
+	if parsed == nil {
+		return
+	}
+	parsed.HasSystem = false
+	parsed.systemRange = missingJSONRange()
+	parsed.messagesRange = missingJSONRange()
+}
+
+func setGatewayRequestRanges(parsed *ParsedRequest, protocol string, jsonStr string) {
+	if parsed == nil {
+		return
+	}
+	switch protocol {
+	case domain.PlatformGemini:
+		if sysParts := gjson.Get(jsonStr, "systemInstruction.parts"); sysParts.Exists() && sysParts.IsArray() {
+			parsed.systemRange = rangeFromResult(sysParts)
+		}
+		if contents := gjson.Get(jsonStr, "contents"); contents.Exists() && contents.IsArray() {
+			parsed.messagesRange = rangeFromResult(contents)
+		}
+	default:
+		if sys := gjson.Get(jsonStr, "system"); sys.Exists() {
+			parsed.HasSystem = true
+			parsed.systemRange = rangeFromResult(sys)
+		}
+		if msgs := gjson.Get(jsonStr, "messages"); msgs.Exists() && msgs.IsArray() {
+			parsed.messagesRange = rangeFromResult(msgs)
+		}
+	}
+}
+
+func refreshGatewayRequestRanges(parsed *ParsedRequest, protocol string) error {
+	if parsed == nil {
+		return fmt.Errorf("empty request body")
+	}
+	clearGatewayRequestRanges(parsed)
+	if parsed.Body == nil {
+		return fmt.Errorf("empty request body")
+	}
+
+	bodyBytes := parsed.Body.Bytes()
+	if !gjson.ValidBytes(bodyBytes) {
+		return fmt.Errorf("invalid json")
+	}
+
+	jsonStr := *(*string)(unsafe.Pointer(&bodyBytes))
+	setGatewayRequestRanges(parsed, protocol, jsonStr)
+	return nil
+}
+
 // ParsedRequest 保存网关请求的预解析结果
 //
 // 性能优化说明：
@@ -93,18 +169,20 @@ func (b *RequestBodyRef) Replace(data []byte) {
 // 2. 将解析结果 ParsedRequest 传递给 Service 层
 // 3. 避免重复 json.Unmarshal，减少 CPU 和内存开销
 type ParsedRequest struct {
-	Body            *RequestBodyRef // 原始请求体引用（保留用于转发）
+	Body            *RequestBodyRef // 原始请求体引用（保留用于转发）；替换内容请走 ReplaceBody
 	Model           string          // 请求的模型名称
 	Stream          bool            // 是否为流式请求
 	MetadataUserID  string          // metadata.user_id（用于会话亲和）
-	System          any             // system 字段内容
-	Messages        []any           // messages 数组
 	HasSystem       bool            // 是否包含 system 字段（包含 null 也视为显式传入）
 	ThinkingEnabled bool            // 是否开启 thinking（部分平台会影响最终模型名）
 	OutputEffort    string          // output_config.effort（Claude API 的推理强度控制）
 	MaxTokens       int             // max_tokens 值（用于探测请求拦截）
 	SessionContext  *SessionContext // 可选：请求上下文区分因子（nil 时行为不变）
 
+	protocol      string    // 当前 Body 的协议格式，用于 Body 替换后刷新 raw range
+	systemRange   jsonRange // system/systemInstruction.parts 的 raw JSON 范围，绑定 Body 当前内容
+	messagesRange jsonRange // messages/contents 的 raw JSON 范围，绑定 Body 当前内容
+
 	// GroupID 请求所属分组 ID（来自 API Key）
 	GroupID *int64
 
@@ -174,6 +252,9 @@ func ParseGatewayRequest(body *RequestBodyRef, protocol string) (*ParsedRequest,
 
 	parsed := &ParsedRequest{
 		Body:          body,
+		protocol:      protocol,
+		systemRange:   missingJSONRange(),
+		messagesRange: missingJSONRange(),
 	}
 
 	// --- gjson 提取简单字段（避免完整 Unmarshal） ---
@@ -219,60 +300,73 @@ func ParseGatewayRequest(body *RequestBodyRef, protocol string) (*ParsedRequest,
 	}
 
 	// --- system/messages 提取 ---
-	// 避免把整个 body Unmarshal 到 map（会产生大量 map/接口分配）。
+	// 只保存大字段 raw range，不默认反序列化成 []any/map[string]any 对象图。
-	// 使用 gjson 抽取目标字段的 Raw，再对该子树进行 Unmarshal。
+	setGatewayRequestRanges(parsed, protocol, jsonStr)
-
-	switch protocol {
-	case domain.PlatformGemini:
-		// Gemini 原生格式: systemInstruction.parts / contents
-		if sysParts := gjson.Get(jsonStr, "systemInstruction.parts"); sysParts.Exists() && sysParts.IsArray() {
-			var parts []any
-			if err := json.Unmarshal(sliceRawFromBody(bodyBytes, sysParts), &parts); err != nil {
-				return nil, err
-			}
-			parsed.System = parts
-		}
-
-		if contents := gjson.Get(jsonStr, "contents"); contents.Exists() && contents.IsArray() {
-			var msgs []any
-			if err := json.Unmarshal(sliceRawFromBody(bodyBytes, contents), &msgs); err != nil {
-				return nil, err
-			}
-			parsed.Messages = msgs
-		}
-	default:
-		// Anthropic / OpenAI 格式: system / messages
-		// system 字段只要存在就视为显式提供（即使为 null），
-		// 以避免客户端传 null 时被默认 system 误注入。
-		if sys := gjson.Get(jsonStr, "system"); sys.Exists() {
-			parsed.HasSystem = true
-			switch sys.Type {
-			case gjson.Null:
-				parsed.System = nil
-			case gjson.String:
-				// 与 encoding/json 的 Unmarshal 行为一致：返回解码后的字符串。
-				parsed.System = sys.String()
-			default:
-				var system any
-				if err := json.Unmarshal(sliceRawFromBody(bodyBytes, sys), &system); err != nil {
-					return nil, err
-				}
-				parsed.System = system
-			}
-		}
-
-		if msgs := gjson.Get(jsonStr, "messages"); msgs.Exists() && msgs.IsArray() {
-			var messages []any
-			if err := json.Unmarshal(sliceRawFromBody(bodyBytes, msgs), &messages); err != nil {
-				return nil, err
-			}
-			parsed.Messages = messages
-		}
-	}
 
 	return parsed, nil
 }
 
+func (p *ParsedRequest) raw(r jsonRange) []byte {
+	if p == nil || p.Body == nil || !r.exists() {
+		return nil
+	}
+	body := p.Body.Bytes()
+	if r.end > len(body) {
+		return nil
+	}
+	return body[r.start:r.end]
+}
+
+func (p *ParsedRequest) SystemRaw() []byte {
+	return p.raw(p.systemRange)
+}
+
+func (p *ParsedRequest) MessagesRaw() []byte {
+	return p.raw(p.messagesRange)
+}
+
+func (p *ParsedRequest) DecodeSystem(dst any) error {
+	raw := p.SystemRaw()
+	if len(raw) == 0 {
+		return nil
+	}
+	return json.Unmarshal(raw, dst)
+}
+
+func (p *ParsedRequest) DecodeMessages(dst any) error {
+	raw := p.MessagesRaw()
+	if len(raw) == 0 {
+		return nil
+	}
+	return json.Unmarshal(raw, dst)
+}
+
+func (p *ParsedRequest) SystemValue() (any, bool) {
+	raw := p.SystemRaw()
+	if len(raw) == 0 {
+		return nil, false
+	}
+	var system any
+	if err := json.Unmarshal(raw, &system); err != nil {
+		return nil, false
+	}
+	return system, true
+}
+
+func (p *ParsedRequest) ReplaceBody(data []byte) {
+	if p == nil {
+		return
+	}
+	if p.Body == nil {
+		p.Body = NewRequestBodyRef(data)
+	} else {
+		p.Body.Replace(data)
+	}
+	if err := refreshGatewayRequestRanges(p, p.protocol); err != nil {
+		clearGatewayRequestRanges(p)
+	}
+}
+
 // sliceRawFromBody 返回 Result.Raw 对应的原始字节切片。
 // 优先使用 Result.Index 直接从 body 切片，避免对大字段（如 messages）产生额外拷贝。
 // 当 Index 不可用时，退化为复制（理论上极少发生）。

backend/internal/service/gateway_request_test.go

@@ -10,6 +10,7 @@ import (
 
 	"github.com/Wei-Shaw/sub2api/internal/domain"
 	"github.com/stretchr/testify/require"
+	"github.com/tidwall/gjson"
 )
 
 func TestParseGatewayRequest(t *testing.T) {
@@ -20,8 +21,8 @@ func TestParseGatewayRequest(t *testing.T) {
 	require.True(t, parsed.Stream)
 	require.Equal(t, "session_123e4567-e89b-12d3-a456-426614174000", parsed.MetadataUserID)
 	require.True(t, parsed.HasSystem)
-	require.NotNil(t, parsed.System)
+	require.NotEmpty(t, parsed.SystemRaw())
-	require.Len(t, parsed.Messages, 1)
+	require.NotEmpty(t, parsed.MessagesRaw())
 	require.False(t, parsed.ThinkingEnabled)
 }
 
@@ -61,7 +62,7 @@ func TestParseGatewayRequest_SystemNull(t *testing.T) {
 	require.NoError(t, err)
 	// 显式传入 system:null 也应视为“字段已存在”，避免默认 system 被注入。
 	require.True(t, parsed.HasSystem)
-	require.Nil(t, parsed.System)
+	require.Equal(t, []byte("null"), parsed.SystemRaw())
 }
 
 func TestParseGatewayRequest_InvalidModelType(t *testing.T) {
@@ -88,9 +89,9 @@ func TestParseGatewayRequest_GeminiContents(t *testing.T) {
 	}`)
 	parsed, err := ParseGatewayRequest(NewRequestBodyRef(body), domain.PlatformGemini)
 	require.NoError(t, err)
-	require.Len(t, parsed.Messages, 3, "should parse contents as Messages")
+	require.Len(t, gjson.ParseBytes(parsed.MessagesRaw()).Array(), 3, "should parse contents as Messages")
 	require.False(t, parsed.HasSystem, "Gemini format should not set HasSystem")
-	require.Nil(t, parsed.System, "no systemInstruction means nil System")
+	require.Nil(t, parsed.SystemRaw(), "no systemInstruction means nil System")
 }
 
 func TestParseGatewayRequest_GeminiSystemInstruction(t *testing.T) {
@@ -104,14 +105,11 @@ func TestParseGatewayRequest_GeminiSystemInstruction(t *testing.T) {
 	}`)
 	parsed, err := ParseGatewayRequest(NewRequestBodyRef(body), domain.PlatformGemini)
 	require.NoError(t, err)
-	require.NotNil(t, parsed.System, "should parse systemInstruction.parts as System")
+	system := gjson.ParseBytes(parsed.SystemRaw())
-	parts, ok := parsed.System.([]any)
+	require.True(t, system.IsArray(), "should parse systemInstruction.parts as System")
-	require.True(t, ok)
+	require.Len(t, system.Array(), 1)
-	require.Len(t, parts, 1)
+	require.Equal(t, "You are a helpful assistant.", system.Get("0.text").String())
-	partMap, ok := parts[0].(map[string]any)
+	require.Len(t, gjson.ParseBytes(parsed.MessagesRaw()).Array(), 1)
-	require.True(t, ok)
-	require.Equal(t, "You are a helpful assistant.", partMap["text"])
-	require.Len(t, parsed.Messages, 1)
 }
 
 func TestParseGatewayRequest_GeminiWithModel(t *testing.T) {
@@ -122,7 +120,7 @@ func TestParseGatewayRequest_GeminiWithModel(t *testing.T) {
 	parsed, err := ParseGatewayRequest(NewRequestBodyRef(body), domain.PlatformGemini)
 	require.NoError(t, err)
 	require.Equal(t, "gemini-2.5-pro", parsed.Model)
-	require.Len(t, parsed.Messages, 1)
+	require.Len(t, gjson.ParseBytes(parsed.MessagesRaw()).Array(), 1)
 }
 
 func TestParseGatewayRequest_GeminiIgnoresAnthropicFields(t *testing.T) {
@@ -135,22 +133,22 @@ func TestParseGatewayRequest_GeminiIgnoresAnthropicFields(t *testing.T) {
 	parsed, err := ParseGatewayRequest(NewRequestBodyRef(body), domain.PlatformGemini)
 	require.NoError(t, err)
 	require.False(t, parsed.HasSystem, "Gemini protocol should not parse Anthropic system field")
-	require.Nil(t, parsed.System, "no systemInstruction = nil System")
+	require.Nil(t, parsed.SystemRaw(), "no systemInstruction = nil System")
-	require.Len(t, parsed.Messages, 1, "should use contents, not messages")
+	require.Len(t, gjson.ParseBytes(parsed.MessagesRaw()).Array(), 1, "should use contents, not messages")
 }
 
 func TestParseGatewayRequest_GeminiEmptyContents(t *testing.T) {
 	body := []byte(`{"contents": []}`)
 	parsed, err := ParseGatewayRequest(NewRequestBodyRef(body), domain.PlatformGemini)
 	require.NoError(t, err)
-	require.Empty(t, parsed.Messages)
+	require.Empty(t, gjson.ParseBytes(parsed.MessagesRaw()).Array())
 }
 
 func TestParseGatewayRequest_GeminiNoContents(t *testing.T) {
 	body := []byte(`{"model": "gemini-2.5-flash"}`)
 	parsed, err := ParseGatewayRequest(NewRequestBodyRef(body), domain.PlatformGemini)
 	require.NoError(t, err)
-	require.Nil(t, parsed.Messages)
+	require.Nil(t, parsed.MessagesRaw())
 	require.Equal(t, "gemini-2.5-flash", parsed.Model)
 }
 
@@ -165,11 +163,10 @@ func TestParseGatewayRequest_AnthropicIgnoresGeminiFields(t *testing.T) {
 	parsed, err := ParseGatewayRequest(NewRequestBodyRef(body), domain.PlatformAnthropic)
 	require.NoError(t, err)
 	require.True(t, parsed.HasSystem)
-	require.Equal(t, "real system", parsed.System)
+	require.Equal(t, "real system", gjson.ParseBytes(parsed.SystemRaw()).String())
-	require.Len(t, parsed.Messages, 1)
+	messages := gjson.ParseBytes(parsed.MessagesRaw()).Array()
-	msg, ok := parsed.Messages[0].(map[string]any)
+	require.Len(t, messages, 1)
-	require.True(t, ok)
+	require.Equal(t, "real content", messages[0].Get("content").String())
-	require.Equal(t, "real content", msg["content"])
 }
 
 func TestFilterThinkingBlocks(t *testing.T) {
@@ -970,10 +967,10 @@ func TestParseGatewayRequest_OptionalFieldsMissing(t *testing.T) {
 			require.Equal(t, tt.wantMaxTokens, parsed.MaxTokens)
 
 			if tt.wantMessagesNil {
-				require.Nil(t, parsed.Messages)
+				require.Nil(t, parsed.MessagesRaw())
 			}
 			if tt.wantMessagesLen > 0 {
-				require.Len(t, parsed.Messages, tt.wantMessagesLen)
+				require.Len(t, gjson.ParseBytes(parsed.MessagesRaw()).Array(), tt.wantMessagesLen)
 			}
 		})
 	}
@@ -1087,25 +1084,8 @@ func parseGatewayRequestOld(body []byte, protocol string) (*ParsedRequest, error
 		}
 	}
 
-	// system / messages（按协议分支）
+	if err := refreshGatewayRequestRanges(parsed, protocol); err != nil {
-	switch protocol {
+		return nil, err
-	case domain.PlatformGemini:
-		if sysInst, ok := req["systemInstruction"].(map[string]any); ok {
-			if parts, ok := sysInst["parts"].([]any); ok {
-				parsed.System = parts
-			}
-		}
-		if contents, ok := req["contents"].([]any); ok {
-			parsed.Messages = contents
-		}
-	default:
-		if system, ok := req["system"]; ok {
-			parsed.HasSystem = true
-			parsed.System = system
-		}
-		if messages, ok := req["messages"].([]any); ok {
-			parsed.Messages = messages
-		}
 	}
 
 	return parsed, nil

backend/internal/service/gateway_service.go

@@ -748,31 +748,10 @@ func (s *GatewayService) GenerateSessionHash(parsed *ParsedRequest) string {
 		_, _ = combined.WriteString(strconv.FormatInt(parsed.SessionContext.APIKeyID, 10))
 		_, _ = combined.WriteString("|")
 	}
-	if parsed.System != nil {
+	if systemText := extractTextFromSystemRaw(parsed.SystemRaw()); systemText != "" {
-		systemText := s.extractTextFromSystem(parsed.System)
-		if systemText != "" {
 		_, _ = combined.WriteString(systemText)
 	}
-	}
+	appendMessageTextsFromRaw(&combined, parsed.MessagesRaw())
-	for _, msg := range parsed.Messages {
-		if m, ok := msg.(map[string]any); ok {
-			if content, exists := m["content"]; exists {
-				// Anthropic: messages[].content
-				if msgText := s.extractTextFromContent(content); msgText != "" {
-					_, _ = combined.WriteString(msgText)
-				}
-			} else if parts, ok := m["parts"].([]any); ok {
-				// Gemini: contents[].parts[].text
-				for _, part := range parts {
-					if partMap, ok := part.(map[string]any); ok {
-						if text, ok := partMap["text"].(string); ok {
-							_, _ = combined.WriteString(text)
-						}
-					}
-				}
-			}
-		}
-	}
 	if combined.Len() > 0 {
 		hash := s.hashContent(combined.String())
 		slog.Info("sticky.hash_source",
@@ -847,82 +826,127 @@ func (s *GatewayService) extractCacheableContent(parsed *ParsedRequest) string {
 		return ""
 	}
 
-	var builder strings.Builder
+	systemText := extractCacheableTextFromSystemRaw(parsed.SystemRaw())
-
+	if messageText := extractCacheableTextFromMessagesRaw(parsed.MessagesRaw()); messageText != "" {
-	// 检查 system 中的 cacheable 内容
+		return messageText
-	if system, ok := parsed.System.([]any); ok {
-		for _, part := range system {
-			if partMap, ok := part.(map[string]any); ok {
-				if cc, ok := partMap["cache_control"].(map[string]any); ok {
-					if cc["type"] == "ephemeral" {
-						if text, ok := partMap["text"].(string); ok {
-							_, _ = builder.WriteString(text)
 	}
-					}
-				}
-			}
-		}
-	}
-	systemText := builder.String()
-
-	// 检查 messages 中的 cacheable 内容
-	for _, msg := range parsed.Messages {
-		if msgMap, ok := msg.(map[string]any); ok {
-			if msgContent, ok := msgMap["content"].([]any); ok {
-				for _, part := range msgContent {
-					if partMap, ok := part.(map[string]any); ok {
-						if cc, ok := partMap["cache_control"].(map[string]any); ok {
-							if cc["type"] == "ephemeral" {
-								return s.extractTextFromContent(msgMap["content"])
-							}
-						}
-					}
-				}
-			}
-		}
-	}
-
 	return systemText
 }
 
-func (s *GatewayService) extractTextFromSystem(system any) string {
+func extractTextFromSystemRaw(raw []byte) string {
-	switch v := system.(type) {
+	system := gjson.ParseBytes(raw)
-	case string:
+	switch system.Type {
-		return v
+	case gjson.String:
-	case []any:
+		return system.String()
-		var texts []string
+	case gjson.JSON:
-		for _, part := range v {
+		if !system.IsArray() {
-			if partMap, ok := part.(map[string]any); ok {
+			return ""
-				if text, ok := partMap["text"].(string); ok {
-					texts = append(texts, text)
 		}
+		var builder strings.Builder
+		system.ForEach(func(_, part gjson.Result) bool {
+			if text := part.Get("text").String(); text != "" {
+				_, _ = builder.WriteString(text)
 			}
-		}
+			return true
-		return strings.Join(texts, "")
+		})
+		return builder.String()
 	}
 	return ""
 }
 
-func (s *GatewayService) extractTextFromContent(content any) string {
+func extractTextFromContentRaw(content gjson.Result) string {
-	switch v := content.(type) {
+	switch content.Type {
-	case string:
+	case gjson.String:
-		return v
+		return content.String()
-	case []any:
+	case gjson.JSON:
-		var texts []string
+		if !content.IsArray() {
-		for _, part := range v {
+			return ""
-			if partMap, ok := part.(map[string]any); ok {
+		}
-				if partMap["type"] == "text" {
+		var builder strings.Builder
-					if text, ok := partMap["text"].(string); ok {
+		content.ForEach(func(_, part gjson.Result) bool {
-						texts = append(texts, text)
+			if part.Get("type").String() == "text" {
+				if text := part.Get("text").String(); text != "" {
+					_, _ = builder.WriteString(text)
 				}
 			}
-			}
+			return true
-		}
+		})
-		return strings.Join(texts, "")
+		return builder.String()
 	}
 	return ""
 }
 
+func appendMessageTextsFromRaw(builder *strings.Builder, raw []byte) {
+	if builder == nil || len(raw) == 0 {
+		return
+	}
+	messages := gjson.ParseBytes(raw)
+	if !messages.IsArray() {
+		return
+	}
+	messages.ForEach(func(_, msg gjson.Result) bool {
+		if content := msg.Get("content"); content.Exists() {
+			_, _ = builder.WriteString(extractTextFromContentRaw(content))
+			return true
+		}
+		parts := msg.Get("parts")
+		if parts.IsArray() {
+			parts.ForEach(func(_, part gjson.Result) bool {
+				if text := part.Get("text").String(); text != "" {
+					_, _ = builder.WriteString(text)
+				}
+				return true
+			})
+		}
+		return true
+	})
+}
+
+func extractCacheableTextFromSystemRaw(raw []byte) string {
+	system := gjson.ParseBytes(raw)
+	if !system.IsArray() {
+		return ""
+	}
+	var builder strings.Builder
+	system.ForEach(func(_, part gjson.Result) bool {
+		if part.Get("cache_control.type").String() == "ephemeral" {
+			if text := part.Get("text").String(); text != "" {
+				_, _ = builder.WriteString(text)
+			}
+		}
+		return true
+	})
+	return builder.String()
+}
+
+func extractCacheableTextFromMessagesRaw(raw []byte) string {
+	messages := gjson.ParseBytes(raw)
+	if !messages.IsArray() {
+		return ""
+	}
+	var text string
+	messages.ForEach(func(_, msg gjson.Result) bool {
+		content := msg.Get("content")
+		if !content.IsArray() {
+			return true
+		}
+		found := false
+		content.ForEach(func(_, part gjson.Result) bool {
+			if part.Get("cache_control.type").String() == "ephemeral" {
+				found = true
+				return false
+			}
+			return true
+		})
+		if found {
+			text = extractTextFromContentRaw(content)
+			return false
+		}
+		return true
+	})
+	return text
+}
+
 func (s *GatewayService) hashContent(content string) string {
 	h := xxhash.Sum64String(content)
 	return strconv.FormatUint(h, 36)
@@ -1284,7 +1308,7 @@ func (s *GatewayService) applyClaudeCodeOAuthMimicryToBody(
 
 	systemRewritten := false
 	if !strings.Contains(strings.ToLower(model), "haiku") {
-		body = rewriteSystemForNonClaudeCode(body, systemRaw)
+		body = rewriteSystemForNonClaudeCode(body, normalizeSystemParam(systemRaw))
 		systemRewritten = true
 	}
 
@@ -4474,7 +4498,8 @@ func (s *GatewayService) Forward(ctx context.Context, c *gin.Context, account *A
 		// Parrot 的 transform_request 从不检查客户端 system 内容，直接覆盖。
 		systemRewritten := false
 		if !strings.Contains(strings.ToLower(reqModel), "haiku") {
-			body = rewriteSystemForNonClaudeCode(body, parsed.System)
+			systemRaw, _ := parsed.SystemValue()
+			body = rewriteSystemForNonClaudeCode(body, systemRaw)
 			systemRewritten = true
 		}
 

backend/internal/service/gateway_service_benchmark_test.go

@@ -2,6 +2,7 @@ package service
 
 import (
 	"strconv"
+	"strings"
 	"testing"
 )
 
@@ -34,17 +35,20 @@ func BenchmarkExtractCacheableContent_System(b *testing.B) {
 }
 
 func buildSystemCacheableRequest(parts int) *ParsedRequest {
-	systemParts := make([]any, 0, parts)
+	var builder strings.Builder
+	builder.WriteString(`{"system":[`)
 	for i := 0; i < parts; i++ {
-		systemParts = append(systemParts, map[string]any{
+		if i > 0 {
-			"text": "system_part_" + strconv.Itoa(i),
+			builder.WriteByte(',')
-			"cache_control": map[string]any{
-				"type": "ephemeral",
-			},
-		})
 		}
-	return &ParsedRequest{
+		builder.WriteString(`{"text":"system_part_`)
-		System:    systemParts,
+		builder.WriteString(strconv.Itoa(i))
-		HasSystem: true,
+		builder.WriteString(`","cache_control":{"type":"ephemeral"}}`)
 	}
+	builder.WriteString(`]}`)
+	parsed, err := ParseGatewayRequest(NewRequestBodyRef([]byte(builder.String())), "")
+	if err != nil {
+		panic(err)
+	}
+	return parsed
 }

backend/internal/service/openai_gateway_service.go

@@ -36,6 +36,13 @@ import (
 	"go.uber.org/zap"
 )
 
+// openAIParsedRequestBodyCache 绑定 body 指纹，避免 handler 预解析的旧 body 污染后续 forwardBody。
+type openAIParsedRequestBodyCache struct {
+	bodyHash uint64
+	bodyLen  int
+	reqBody  map[string]any
+}
+
 const (
 	// ChatGPT internal API for OAuth accounts
 	chatgptCodexURL = "https://chatgpt.com/backend-api/codex/responses"
@@ -2284,6 +2291,20 @@ func (s *OpenAIGatewayService) shouldFailoverOpenAIUpstreamResponse(statusCode i
 	return isOpenAITransientProcessingError(statusCode, upstreamMsg, upstreamBody)
 }
 
+func marshalOpenAIUpstreamJSON(v any) ([]byte, error) {
+	var buf bytes.Buffer
+	enc := json.NewEncoder(&buf)
+	enc.SetEscapeHTML(false)
+	if err := enc.Encode(v); err != nil {
+		return nil, err
+	}
+	out := buf.Bytes()
+	if len(out) > 0 && out[len(out)-1] == '\n' {
+		out = out[:len(out)-1]
+	}
+	return out, nil
+}
+
 func (s *OpenAIGatewayService) handleFailoverSideEffects(ctx context.Context, resp *http.Response, account *Account, requestedModel ...string) {
 	body, _ := io.ReadAll(io.LimitReader(resp.Body, 2<<20))
 	if len(requestedModel) > 0 {
@@ -2561,7 +2582,11 @@ func (s *OpenAIGatewayService) Forward(ctx context.Context, c *gin.Context, acco
 		// 确保高版本模型向低版本模型映射不报错
 		if !SupportsVerbosity(upstreamModel) {
 			if text, ok := reqBody["text"].(map[string]any); ok {
+				if _, exists := text["verbosity"]; exists {
 					delete(text, "verbosity")
+					bodyModified = true
+					markPatchDelete("text.verbosity")
+				}
 			}
 		}
 	}
@@ -2762,7 +2787,7 @@ func (s *OpenAIGatewayService) Forward(ctx context.Context, c *gin.Context, acco
 		}
 		if !serializedByPatch {
 			var marshalErr error
-			body, marshalErr = json.Marshal(reqBody)
+			body, marshalErr = marshalOpenAIUpstreamJSON(reqBody)
 			if marshalErr != nil {
 				return nil, fmt.Errorf("serialize request body: %w", marshalErr)
 			}
@@ -3043,7 +3068,7 @@ func (s *OpenAIGatewayService) Forward(ctx context.Context, c *gin.Context, acco
 			upstreamCode := extractUpstreamErrorCode(respBody)
 			if !httpInvalidEncryptedContentRetryTried && resp.StatusCode == http.StatusBadRequest && upstreamCode == "invalid_encrypted_content" {
 				if trimOpenAIEncryptedReasoningItems(reqBody) {
-					body, err = json.Marshal(reqBody)
+					body, err = marshalOpenAIUpstreamJSON(reqBody)
 					if err != nil {
 						return nil, fmt.Errorf("serialize invalid_encrypted_content retry body: %w", err)
 					}
@@ -3074,6 +3099,8 @@ func (s *OpenAIGatewayService) Forward(ctx context.Context, c *gin.Context, acco
 				})
 
 				s.handleFailoverSideEffects(ctx, resp, account, upstreamModel)
+				// reqBody 会被本次账号尝试原地修改，failover 前必须释放，避免下一账号复用脏 map。
+				releaseOpenAIParsedRequestBody(c)
 				return nil, &UpstreamFailoverError{
 					StatusCode:             resp.StatusCode,
 					ResponseBody:           respBody,
@@ -6711,7 +6738,7 @@ func sanitizeEmptyBase64InputImagesInOpenAIBody(body []byte) ([]byte, bool, erro
 	if !sanitizeEmptyBase64InputImagesInOpenAIRequestBodyMap(reqBody) {
 		return body, false, nil
 	}
-	normalized, err := json.Marshal(reqBody)
+	normalized, err := marshalOpenAIUpstreamJSON(reqBody)
 	if err != nil {
 		return body, false, fmt.Errorf("serialize sanitized request body: %w", err)
 	}
@@ -6817,10 +6844,13 @@ func isEmptyBase64DataURI(raw string) bool {
 }
 
 func getOpenAIRequestBodyMap(c *gin.Context, body []byte) (map[string]any, error) {
+	// 同一个 gin.Context 内 failover/渠道映射可能传入新 body，缓存必须先校验 body 指纹。
+	bodyHash := xxhash.Sum64(body)
+	bodyLen := len(body)
 	if c != nil {
 		if cached, ok := c.Get(OpenAIParsedRequestBodyKey); ok {
-			if reqBody, ok := cached.(map[string]any); ok && reqBody != nil {
+			if cache, ok := cached.(openAIParsedRequestBodyCache); ok && cache.reqBody != nil && cache.bodyLen == bodyLen && cache.bodyHash == bodyHash {
-				return reqBody, nil
+				return cache.reqBody, nil
 			}
 		}
 	}
@@ -6830,11 +6860,36 @@ func getOpenAIRequestBodyMap(c *gin.Context, body []byte) (map[string]any, error
 		return nil, fmt.Errorf("parse request: %w", err)
 	}
 	if c != nil {
-		c.Set(OpenAIParsedRequestBodyKey, reqBody)
+		c.Set(OpenAIParsedRequestBodyKey, openAIParsedRequestBodyCache{bodyHash: bodyHash, bodyLen: bodyLen, reqBody: reqBody})
 	}
 	return reqBody, nil
 }
 
+// CacheOpenAIParsedRequestBody 仅缓存与当前 body 绑定的解析结果。
+func CacheOpenAIParsedRequestBody(c *gin.Context, body []byte, reqBody map[string]any) {
+	if c == nil || reqBody == nil {
+		return
+	}
+	c.Set(OpenAIParsedRequestBodyKey, openAIParsedRequestBodyCache{
+		bodyHash: xxhash.Sum64(body),
+		bodyLen:  len(body),
+		reqBody:  reqBody,
+	})
+}
+
+// CachedOpenAIParsedRequestBody 只给同请求内不关心 body 参数的轻量识别逻辑使用。
+func CachedOpenAIParsedRequestBody(c *gin.Context) map[string]any {
+	if c == nil {
+		return nil
+	}
+	if cached, ok := c.Get(OpenAIParsedRequestBodyKey); ok {
+		if cache, ok := cached.(openAIParsedRequestBodyCache); ok {
+			return cache.reqBody
+		}
+	}
+	return nil
+}
+
 func releaseOpenAIParsedRequestBody(c *gin.Context) {
 	if c == nil {
 		return

backend/internal/service/openai_gateway_service_hotpath_test.go

@@ -112,7 +112,7 @@ func TestGetOpenAIRequestBodyMap_UsesContextCache(t *testing.T) {
 	c, _ := gin.CreateTestContext(rec)
 
 	cached := map[string]any{"model": "cached-model", "stream": true}
-	c.Set(OpenAIParsedRequestBodyKey, cached)
+	CacheOpenAIParsedRequestBody(c, []byte(`{invalid-json`), cached)
 
 	got, err := getOpenAIRequestBodyMap(c, []byte(`{invalid-json`))
 	require.NoError(t, err)
@@ -134,11 +134,19 @@ func TestGetOpenAIRequestBodyMap_WriteBackContextCache(t *testing.T) {
 	require.NoError(t, err)
 	require.Equal(t, "gpt-5", got["model"])
 
-	cached, ok := c.Get(OpenAIParsedRequestBodyKey)
+	require.Equal(t, got, CachedOpenAIParsedRequestBody(c))
-	require.True(t, ok)
+}
-	cachedMap, ok := cached.(map[string]any)
+
-	require.True(t, ok)
+func TestGetOpenAIRequestBodyMap_IgnoresCacheForDifferentBody(t *testing.T) {
-	require.Equal(t, got, cachedMap)
+	gin.SetMode(gin.TestMode)
+	rec := httptest.NewRecorder()
+	c, _ := gin.CreateTestContext(rec)
+
+	CacheOpenAIParsedRequestBody(c, []byte(`{"model":"cached-model"}`), map[string]any{"model": "cached-model"})
+
+	got, err := getOpenAIRequestBodyMap(c, []byte(`{"model":"forward-model"}`))
+	require.NoError(t, err)
+	require.Equal(t, "forward-model", got["model"])
 }
 
 func TestSanitizeEmptyBase64InputImagesInOpenAIRequestBodyMap(t *testing.T) {

backend/internal/service/openai_oauth_passthrough_test.go

@@ -14,6 +14,7 @@ import (
 
 	"github.com/Wei-Shaw/sub2api/internal/config"
 	"github.com/Wei-Shaw/sub2api/internal/pkg/logger"
+	"github.com/Wei-Shaw/sub2api/internal/pkg/openai_compat"
 	"github.com/Wei-Shaw/sub2api/internal/pkg/tlsfingerprint"
 	"github.com/gin-gonic/gin"
 	"github.com/stretchr/testify/require"
@@ -101,6 +102,57 @@ func TestOpenAIGatewayService_ResponsesUnknownModelDoesNotFallbackToGPT54(t *tes
 	require.True(t, rec.Code >= http.StatusBadRequest)
 }
 
+func TestOpenAIGatewayService_NativeResponsesBodyModificationPreservesHTMLChars(t *testing.T) {
+	gin.SetMode(gin.TestMode)
+
+	payloadText := strings.Repeat(`<tag>&value</tag>`, 128)
+	originalBody := []byte(fmt.Sprintf(`{"model":"gpt-5.5","stream":false,"max_output_tokens":100,"previous_response_id":"resp_prev","input":[{"type":"message","role":"user","content":[{"type":"input_text","text":%q}]}]}`, payloadText))
+	rec := httptest.NewRecorder()
+	c, _ := gin.CreateTestContext(rec)
+	c.Request = httptest.NewRequest(http.MethodPost, "/v1/responses", bytes.NewReader(originalBody))
+	c.Request.Header.Set("Content-Type", "application/json")
+
+	upstream := &httpUpstreamRecorder{resp: &http.Response{
+		StatusCode: http.StatusBadRequest,
+		Header:     http.Header{"Content-Type": []string{"application/json"}, "x-request-id": []string{"rid_native_reencode"}},
+		Body:       io.NopCloser(strings.NewReader(`{"error":{"type":"invalid_request_error","message":"stop after capture"}}`)),
+	}}
+	svc := &OpenAIGatewayService{
+		cfg: &config.Config{Security: config.SecurityConfig{URLAllowlist: config.URLAllowlistConfig{
+			Enabled:           false,
+			AllowInsecureHTTP: true,
+		}}},
+		httpUpstream: upstream,
+	}
+	account := &Account{
+		ID:          456,
+		Name:        "openai-apikey",
+		Platform:    PlatformOpenAI,
+		Type:        AccountTypeAPIKey,
+		Concurrency: 1,
+		Credentials: map[string]any{
+			"api_key":  "sk-test",
+			"base_url": "http://upstream.example",
+		},
+		Extra: map[string]any{
+			openai_compat.ExtraKeyResponsesMode:      string(openai_compat.ResponsesSupportModeAuto),
+			openai_compat.ExtraKeyResponsesSupported: true,
+		},
+		Status:      StatusActive,
+		Schedulable: true,
+	}
+
+	result, err := svc.Forward(context.Background(), c, account, originalBody)
+	require.Error(t, err)
+	require.Nil(t, result)
+	require.NotNil(t, upstream.lastReq)
+	require.Equal(t, "http://upstream.example/v1/responses", upstream.lastReq.URL.String())
+	require.Contains(t, string(upstream.lastBody), payloadText)
+	require.NotContains(t, string(upstream.lastBody), `\\u003c`)
+	require.NotContains(t, string(upstream.lastBody), `\\u003e`)
+	require.NotContains(t, string(upstream.lastBody), `\\u0026`)
+}
+
 func TestOpenAIGatewayService_OAuthMessagesBridgeDoesNotInjectDefaultInstructions(t *testing.T) {
 	gin.SetMode(gin.TestMode)
 

backend/internal/service/user_msg_queue_service.go

@@ -12,6 +12,7 @@ import (
 
 	"github.com/Wei-Shaw/sub2api/internal/config"
 	"github.com/Wei-Shaw/sub2api/internal/pkg/logger"
+	"github.com/tidwall/gjson"
 )
 
 // UserMsgQueueCache 用户消息串行队列 Redis 缓存接口
@@ -62,43 +63,48 @@ func NewUserMessageQueueService(cache UserMsgQueueCache, rpmCache RPMCache, cfg
 // 2. 最后一条消息 role == "user"
 // 3. 最后一条消息 content（如果是数组）中不含 type:"tool_result" / "tool_use_result"
 func IsRealUserMessage(parsed *ParsedRequest) bool {
-	if parsed == nil || len(parsed.Messages) == 0 {
+	if parsed == nil {
+		return false
+	}
+	messagesRaw := parsed.MessagesRaw()
+	if len(messagesRaw) == 0 {
 		return false
 	}
 
-	lastMsg := parsed.Messages[len(parsed.Messages)-1]
+	messages := gjson.ParseBytes(messagesRaw)
-	msgMap, ok := lastMsg.(map[string]any)
+	if !messages.IsArray() {
-	if !ok {
+		return false
+	}
+	lastMsg := gjson.Result{}
+	messages.ForEach(func(_, msg gjson.Result) bool {
+		lastMsg = msg
+		return true
+	})
+	if !lastMsg.Exists() || !lastMsg.IsObject() {
+		return false
+	}
+	if lastMsg.Get("role").String() != "user" {
 		return false
 	}
 
-	role, _ := msgMap["role"].(string)
+	content := lastMsg.Get("content")
-	if role != "user" {
+	if !content.Exists() {
-		return false
+		return true
+	}
+	if !content.IsArray() {
+		return true
 	}
 
-	// 检查 content 是否包含 tool_result 类型
+	isReal := true
-	content, ok := msgMap["content"]
+	content.ForEach(func(_, item gjson.Result) bool {
-	if !ok {
+		itemType := item.Get("type").String()
-		return true // 没有 content 字段，视为普通用户消息
-	}
-
-	contentArr, ok := content.([]any)
-	if !ok {
-		return true // content 不是数组（可能是 string），视为普通用户消息
-	}
-
-	for _, item := range contentArr {
-		itemMap, ok := item.(map[string]any)
-		if !ok {
-			continue
-		}
-		itemType, _ := itemMap["type"].(string)
 		if itemType == "tool_result" || itemType == "tool_use_result" {
+			isReal = false
 			return false
 		}
-	}
 		return true
+	})
+	return isReal
 }
 
 // TryAcquire 尝试立即获取串行锁