feat: add antigravity web search support

backend/internal/pkg/antigravity/gemini_types.go

@@ -143,9 +143,10 @@ type GeminiResponse struct {
 
 // GeminiCandidate Gemini 候选响应
 type GeminiCandidate struct {
-	Content      *GeminiContent `json:"content,omitempty"`
-	FinishReason string         `json:"finishReason,omitempty"`
-	Index        int            `json:"index,omitempty"`
+	Content            *GeminiContent           `json:"content,omitempty"`
+	FinishReason       string                   `json:"finishReason,omitempty"`
+	Index              int                      `json:"index,omitempty"`
+	GroundingMetadata  *GeminiGroundingMetadata `json:"groundingMetadata,omitempty"`
 }
 
 // GeminiUsageMetadata Gemini 用量元数据
@@ -156,6 +157,23 @@ type GeminiUsageMetadata struct {
 	TotalTokenCount         int `json:"totalTokenCount,omitempty"`
 }
 
+// GeminiGroundingMetadata Gemini grounding 元数据（Web Search）
+type GeminiGroundingMetadata struct {
+	WebSearchQueries []string               `json:"webSearchQueries,omitempty"`
+	GroundingChunks  []GeminiGroundingChunk `json:"groundingChunks,omitempty"`
+}
+
+// GeminiGroundingChunk Gemini grounding chunk
+type GeminiGroundingChunk struct {
+	Web *GeminiGroundingWeb `json:"web,omitempty"`
+}
+
+// GeminiGroundingWeb Gemini grounding web 信息
+type GeminiGroundingWeb struct {
+	Title string `json:"title,omitempty"`
+	URI   string `json:"uri,omitempty"`
+}
+
 // DefaultSafetySettings 默认安全设置（关闭所有过滤）
 var DefaultSafetySettings = []GeminiSafetySetting{
 	{Category: "HARM_CATEGORY_HARASSMENT", Threshold: "OFF"},

backend/internal/pkg/antigravity/request_transformer.go

@@ -54,6 +54,9 @@ func DefaultTransformOptions() TransformOptions {
 	}
 }
 
+// webSearchFallbackModel web_search 请求使用的降级模型
+const webSearchFallbackModel = "gemini-2.5-flash"
+
 // TransformClaudeToGemini 将 Claude 请求转换为 v1internal Gemini 格式
 func TransformClaudeToGemini(claudeReq *ClaudeRequest, projectID, mappedModel string) ([]byte, error) {
 	return TransformClaudeToGeminiWithOptions(claudeReq, projectID, mappedModel, DefaultTransformOptions())
@@ -64,12 +67,23 @@ func TransformClaudeToGeminiWithOptions(claudeReq *ClaudeRequest, projectID, map
 	// 用于存储 tool_use id -> name 映射
 	toolIDToName := make(map[string]string)
 
+	// 检测是否有 web_search 工具
+	hasWebSearchTool := hasWebSearchTool(claudeReq.Tools)
+	requestType := "agent"
+	targetModel := mappedModel
+	if hasWebSearchTool {
+		requestType = "web_search"
+		if targetModel != webSearchFallbackModel {
+			targetModel = webSearchFallbackModel
+		}
+	}
+
 	// 检测是否启用 thinking
 	isThinkingEnabled := claudeReq.Thinking != nil && claudeReq.Thinking.Type == "enabled"
 
 	// 只有 Gemini 模型支持 dummy thought workaround
 	// Claude 模型通过 Vertex/Google API 需要有效的 thought signatures
-	allowDummyThought := strings.HasPrefix(mappedModel, "gemini-")
+	allowDummyThought := strings.HasPrefix(targetModel, "gemini-")
 
 	// 1. 构建 contents
 	contents, strippedThinking, err := buildContents(claudeReq.Messages, toolIDToName, isThinkingEnabled, allowDummyThought)
@@ -89,6 +103,11 @@ func TransformClaudeToGeminiWithOptions(claudeReq *ClaudeRequest, projectID, map
 		reqCopy.Thinking = nil
 		reqForConfig = &reqCopy
 	}
+	if targetModel != "" && targetModel != reqForConfig.Model {
+		reqCopy := *reqForConfig
+		reqCopy.Model = targetModel
+		reqForConfig = &reqCopy
+	}
 	generationConfig := buildGenerationConfig(reqForConfig)
 
 	// 4. 构建 tools
@@ -127,8 +146,8 @@ func TransformClaudeToGeminiWithOptions(claudeReq *ClaudeRequest, projectID, map
 		Project:     projectID,
 		RequestID:   "agent-" + uuid.New().String(),
 		UserAgent:   "antigravity", // 固定值，与官方客户端一致
-		RequestType: "agent",
-		Model:       mappedModel,
+		RequestType: requestType,
+		Model:       targetModel,
 		Request:     innerRequest,
 	}
 
@@ -513,37 +532,43 @@ func buildGenerationConfig(req *ClaudeRequest) *GeminiGenerationConfig {
 	return config
 }
 
+func hasWebSearchTool(tools []ClaudeTool) bool {
+	for _, tool := range tools {
+		if isWebSearchTool(tool) {
+			return true
+		}
+	}
+	return false
+}
+
+func isWebSearchTool(tool ClaudeTool) bool {
+	if strings.HasPrefix(tool.Type, "web_search") || tool.Type == "google_search" {
+		return true
+	}
+
+	name := strings.TrimSpace(tool.Name)
+	switch name {
+	case "web_search", "google_search", "web_search_20250305":
+		return true
+	default:
+		return false
+	}
+}
+
 // buildTools 构建 tools
 func buildTools(tools []ClaudeTool) []GeminiToolDeclaration {
 	if len(tools) == 0 {
 		return nil
 	}
 
-	// 检查是否有 web_search 工具
-	hasWebSearch := false
-	for _, tool := range tools {
-		if tool.Name == "web_search" {
-			hasWebSearch = true
-			break
-		}
-	}
-
-	if hasWebSearch {
-		// Web Search 工具映射
-		return []GeminiToolDeclaration{{
-			GoogleSearch: &GeminiGoogleSearch{
-				EnhancedContent: &GeminiEnhancedContent{
-					ImageSearch: &GeminiImageSearch{
-						MaxResultCount: 5,
-					},
-				},
-			},
-		}}
-	}
+	hasWebSearch := hasWebSearchTool(tools)
 
 	// 普通工具
 	var funcDecls []GeminiFunctionDecl
 	for _, tool := range tools {
+		if isWebSearchTool(tool) {
+			continue
+		}
 		// 跳过无效工具名称
 		if strings.TrimSpace(tool.Name) == "" {
 			log.Printf("Warning: skipping tool with empty name")
@@ -586,7 +611,20 @@ func buildTools(tools []ClaudeTool) []GeminiToolDeclaration {
 	}
 
 	if len(funcDecls) == 0 {
-		return nil
+		if !hasWebSearch {
+			return nil
+		}
+
+		// Web Search 工具映射
+		return []GeminiToolDeclaration{{
+			GoogleSearch: &GeminiGoogleSearch{
+				EnhancedContent: &GeminiEnhancedContent{
+					ImageSearch: &GeminiImageSearch{
+						MaxResultCount: 5,
+					},
+				},
+			},
+		}}
 	}
 
 	return []GeminiToolDeclaration{{

backend/internal/pkg/antigravity/response_transformer.go

@@ -3,6 +3,7 @@ package antigravity
 import (
 	"encoding/json"
 	"fmt"
+	"strings"
 )
 
 // TransformGeminiToClaude 将 Gemini 响应转换为 Claude 格式（非流式）
@@ -63,6 +64,12 @@ func (p *NonStreamingProcessor) Process(geminiResp *GeminiResponse, responseID,
 		p.processPart(&part)
 	}
 
+	if len(geminiResp.Candidates) > 0 {
+		if grounding := geminiResp.Candidates[0].GroundingMetadata; grounding != nil {
+			p.processGrounding(grounding)
+		}
+	}
+
 	// 刷新剩余内容
 	p.flushThinking()
 	p.flushText()
@@ -190,6 +197,18 @@ func (p *NonStreamingProcessor) processPart(part *GeminiPart) {
 	}
 }
 
+func (p *NonStreamingProcessor) processGrounding(grounding *GeminiGroundingMetadata) {
+	groundingText := buildGroundingText(grounding)
+	if groundingText == "" {
+		return
+	}
+
+	p.flushThinking()
+	p.flushText()
+	p.textBuilder += groundingText
+	p.flushText()
+}
+
 // flushText 刷新 text builder
 func (p *NonStreamingProcessor) flushText() {
 	if p.textBuilder == "" {
@@ -262,6 +281,44 @@ func (p *NonStreamingProcessor) buildResponse(geminiResp *GeminiResponse, respon
 	}
 }
 
+func buildGroundingText(grounding *GeminiGroundingMetadata) string {
+	if grounding == nil {
+		return ""
+	}
+
+	var builder strings.Builder
+
+	if len(grounding.WebSearchQueries) > 0 {
+		builder.WriteString("\n\n---\nWeb search queries: ")
+		builder.WriteString(strings.Join(grounding.WebSearchQueries, ", "))
+	}
+
+	if len(grounding.GroundingChunks) > 0 {
+		var links []string
+		for i, chunk := range grounding.GroundingChunks {
+			if chunk.Web == nil {
+				continue
+			}
+			title := strings.TrimSpace(chunk.Web.Title)
+			if title == "" {
+				title = "Source"
+			}
+			uri := strings.TrimSpace(chunk.Web.URI)
+			if uri == "" {
+				uri = "#"
+			}
+			links = append(links, fmt.Sprintf("[%d] [%s](%s)", i+1, title, uri))
+		}
+
+		if len(links) > 0 {
+			builder.WriteString("\n\nSources:\n")
+			builder.WriteString(strings.Join(links, "\n"))
+		}
+	}
+
+	return builder.String()
+}
+
 // generateRandomID 生成随机 ID
 func generateRandomID() string {
 	const chars = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"

backend/internal/pkg/antigravity/stream_transformer.go

@@ -27,6 +27,8 @@ type StreamingProcessor struct {
 	pendingSignature  string
 	trailingSignature string
 	originalModel     string
+	webSearchQueries  []string
+	groundingChunks   []GeminiGroundingChunk
 
 	// 累计 usage
 	inputTokens     int
@@ -93,6 +95,10 @@ func (p *StreamingProcessor) ProcessLine(line string) []byte {
 		}
 	}
 
+	if len(geminiResp.Candidates) > 0 {
+		p.captureGrounding(geminiResp.Candidates[0].GroundingMetadata)
+	}
+
 	// 检查是否结束
 	if len(geminiResp.Candidates) > 0 {
 		finishReason := geminiResp.Candidates[0].FinishReason
@@ -200,6 +206,20 @@ func (p *StreamingProcessor) processPart(part *GeminiPart) []byte {
 	return result.Bytes()
 }
 
+func (p *StreamingProcessor) captureGrounding(grounding *GeminiGroundingMetadata) {
+	if grounding == nil {
+		return
+	}
+
+	if len(grounding.WebSearchQueries) > 0 && len(p.webSearchQueries) == 0 {
+		p.webSearchQueries = append([]string(nil), grounding.WebSearchQueries...)
+	}
+
+	if len(grounding.GroundingChunks) > 0 && len(p.groundingChunks) == 0 {
+		p.groundingChunks = append([]GeminiGroundingChunk(nil), grounding.GroundingChunks...)
+	}
+}
+
 // processThinking 处理 thinking
 func (p *StreamingProcessor) processThinking(text, signature string) []byte {
 	var result bytes.Buffer
@@ -417,6 +437,23 @@ func (p *StreamingProcessor) emitFinish(finishReason string) []byte {
 		p.trailingSignature = ""
 	}
 
+	if len(p.webSearchQueries) > 0 || len(p.groundingChunks) > 0 {
+		groundingText := buildGroundingText(&GeminiGroundingMetadata{
+			WebSearchQueries: p.webSearchQueries,
+			GroundingChunks:  p.groundingChunks,
+		})
+		if groundingText != "" {
+			_, _ = result.Write(p.startBlock(BlockTypeText, map[string]any{
+				"type": "text",
+				"text": "",
+			}))
+			_, _ = result.Write(p.emitDelta("text_delta", map[string]any{
+				"text": groundingText,
+			}))
+			_, _ = result.Write(p.endBlock())
+		}
+	}
+
 	// 确定 stop_reason
 	stopReason := "end_turn"
 	if p.usedTool {