diff --git a/backend/internal/service/antigravity_gateway_service.go b/backend/internal/service/antigravity_gateway_service.go
index 8f4d2bfd..3b6ddcb1 100644
--- a/backend/internal/service/antigravity_gateway_service.go
+++ b/backend/internal/service/antigravity_gateway_service.go
@@ -730,9 +730,6 @@ func (s *AntigravityGatewayService) Forward(ctx context.Context, c *gin.Context,
 		proxyURL = account.Proxy.URL()
 	}
 
-	// Sanitize thinking blocks (clean cache_control and flatten history thinking)
-	sanitizeThinkingBlocks(&claudeReq)
-
 	// 获取转换选项
 	// Antigravity 上游要求必须包含身份提示词，否则会返回 429
 	transformOpts := s.getClaudeTransformOptions(ctx)
@@ -744,9 +741,6 @@ func (s *AntigravityGatewayService) Forward(ctx context.Context, c *gin.Context,
 		return nil, fmt.Errorf("transform request: %w", err)
 	}
 
-	// Safety net: ensure no cache_control leaked into Gemini request
-	geminiBody = cleanCacheControlFromGeminiJSON(geminiBody)
-
 	// Antigravity 上游只支持流式请求，统一使用 streamGenerateContent
 	// 如果客户端请求非流式，在响应处理阶段会收集完整流式响应后转换返回
 	action := "streamGenerateContent"
@@ -887,143 +881,6 @@ func extractAntigravityErrorMessage(body []byte) string {
 	return ""
 }
 
-// cleanCacheControlFromGeminiJSON removes cache_control from Gemini JSON (emergency fix)
-// This should not be needed if transformation is correct, but serves as a safety net
-func cleanCacheControlFromGeminiJSON(body []byte) []byte {
-	// Try a more robust approach: parse and clean
-	var data map[string]any
-	if err := json.Unmarshal(body, &data); err != nil {
-		log.Printf("[Antigravity] Failed to parse Gemini JSON for cache_control cleaning: %v", err)
-		return body
-	}
-
-	cleaned := removeCacheControlFromAny(data)
-	if !cleaned {
-		return body
-	}
-
-	if result, err := json.Marshal(data); err == nil {
-		log.Printf("[Antigravity] Successfully cleaned cache_control from Gemini JSON")
-		return result
-	}
-
-	return body
-}
-
-// removeCacheControlFromAny recursively removes cache_control fields
-func removeCacheControlFromAny(v any) bool {
-	cleaned := false
-
-	switch val := v.(type) {
-	case map[string]any:
-		for k, child := range val {
-			if k == "cache_control" {
-				delete(val, k)
-				cleaned = true
-			} else if removeCacheControlFromAny(child) {
-				cleaned = true
-			}
-		}
-	case []any:
-		for _, item := range val {
-			if removeCacheControlFromAny(item) {
-				cleaned = true
-			}
-		}
-	}
-
-	return cleaned
-}
-
-// sanitizeThinkingBlocks cleans cache_control and flattens history thinking blocks
-// Thinking blocks do NOT support cache_control field (Anthropic API/Vertex AI requirement)
-// Additionally, history thinking blocks are flattened to text to avoid upstream validation errors
-func sanitizeThinkingBlocks(req *antigravity.ClaudeRequest) {
-	if req == nil {
-		return
-	}
-
-	log.Printf("[Antigravity] sanitizeThinkingBlocks: processing request with %d messages", len(req.Messages))
-
-	// Clean system blocks
-	if len(req.System) > 0 {
-		var systemBlocks []map[string]any
-		if err := json.Unmarshal(req.System, &systemBlocks); err == nil {
-			for i := range systemBlocks {
-				if blockType, _ := systemBlocks[i]["type"].(string); blockType == "thinking" || systemBlocks[i]["thinking"] != nil {
-					if removeCacheControlFromAny(systemBlocks[i]) {
-						log.Printf("[Antigravity] Deep cleaned cache_control from thinking block in system[%d]", i)
-					}
-				}
-			}
-			// Marshal back
-			if cleaned, err := json.Marshal(systemBlocks); err == nil {
-				req.System = cleaned
-			}
-		}
-	}
-
-	// Clean message content blocks and flatten history
-	lastMsgIdx := len(req.Messages) - 1
-	for msgIdx := range req.Messages {
-		raw := req.Messages[msgIdx].Content
-		if len(raw) == 0 {
-			continue
-		}
-
-		// Try to parse as blocks array
-		var blocks []map[string]any
-		if err := json.Unmarshal(raw, &blocks); err != nil {
-			continue
-		}
-
-		cleaned := false
-		for blockIdx := range blocks {
-			blockType, _ := blocks[blockIdx]["type"].(string)
-
-			// Check for thinking blocks (typed or untyped)
-			if blockType == "thinking" || blocks[blockIdx]["thinking"] != nil {
-				// 1. Clean cache_control
-				if removeCacheControlFromAny(blocks[blockIdx]) {
-					log.Printf("[Antigravity] Deep cleaned cache_control from thinking block in messages[%d].content[%d]", msgIdx, blockIdx)
-					cleaned = true
-				}
-
-				// 2. Flatten to text if it's a history message (not the last one)
-				if msgIdx < lastMsgIdx {
-					log.Printf("[Antigravity] Flattening history thinking block to text at messages[%d].content[%d]", msgIdx, blockIdx)
-
-					// Extract thinking content
-					var textContent string
-					if t, ok := blocks[blockIdx]["thinking"].(string); ok {
-						textContent = t
-					} else {
-						// Fallback for non-string content (marshal it)
-						if b, err := json.Marshal(blocks[blockIdx]["thinking"]); err == nil {
-							textContent = string(b)
-						}
-					}
-
-					// Convert to text block
-					blocks[blockIdx]["type"] = "text"
-					blocks[blockIdx]["text"] = textContent
-					delete(blocks[blockIdx], "thinking")
-					delete(blocks[blockIdx], "signature")
-					delete(blocks[blockIdx], "cache_control") // Ensure it's gone
-					cleaned = true
-				}
-			}
-		}
-
-		// Marshal back if modified
-		if cleaned {
-			if marshaled, err := json.Marshal(blocks); err == nil {
-				req.Messages[msgIdx].Content = marshaled
-			}
-		}
-	}
-}
-
 // stripThinkingFromClaudeRequest converts thinking blocks to text blocks in a Claude Messages request.
 // This preserves the thinking content while avoiding signature validation errors.
 // Note: redacted_thinking blocks are removed because they cannot be converted to text.