Merge pull request #3218 from wucm667/fix/antigravity-system-role-message

fix(antigravity): 处理 messages 中 role:system 消息，修复 Claude Code 接入 400

backend/internal/pkg/antigravity/request_transformer.go

@@ -107,13 +107,19 @@ func TransformClaudeToGeminiWithOptions(claudeReq *ClaudeRequest, projectID, map
 	allowDummyThought := strings.HasPrefix(targetModel, "gemini-")
 
 	// 1. 构建 contents
-	contents, strippedThinking, err := buildContents(claudeReq.Messages, toolIDToName, isThinkingEnabled, allowDummyThought)
+	contents, messageSystemParts, strippedThinking, err := buildContents(claudeReq.Messages, toolIDToName, isThinkingEnabled, allowDummyThought)
 	if err != nil {
 		return nil, fmt.Errorf("build contents: %w", err)
 	}
 
 	// 2. 构建 systemInstruction（使用 targetModel 而非原始请求模型，确保身份注入基于最终模型）
 	systemInstruction := buildSystemInstruction(claudeReq.System, targetModel, opts, claudeReq.Tools)
+	if len(messageSystemParts) > 0 {
+		if systemInstruction == nil {
+			systemInstruction = &GeminiContent{Role: "user"}
+		}
+		systemInstruction.Parts = append(systemInstruction.Parts, messageSystemParts...)
+	}
 
 	// 3. 构建 generationConfig
 	reqForConfig := claudeReq
@@ -357,8 +363,9 @@ func buildSystemInstruction(system json.RawMessage, modelName string, opts Trans
 }
 
 // buildContents 构建 contents
-func buildContents(messages []ClaudeMessage, toolIDToName map[string]string, isThinkingEnabled, allowDummyThought bool) ([]GeminiContent, bool, error) {
+func buildContents(messages []ClaudeMessage, toolIDToName map[string]string, isThinkingEnabled, allowDummyThought bool) ([]GeminiContent, []GeminiPart, bool, error) {
 	var contents []GeminiContent
+	var systemParts []GeminiPart
 	strippedThinking := false
 
 	for i, msg := range messages {
@@ -369,12 +376,17 @@ func buildContents(messages []ClaudeMessage, toolIDToName map[string]string, isT
 
 		parts, strippedThisMsg, err := buildParts(msg.Content, toolIDToName, allowDummyThought)
 		if err != nil {
-			return nil, false, fmt.Errorf("build parts for message %d: %w", i, err)
+			return nil, nil, false, fmt.Errorf("build parts for message %d: %w", i, err)
 		}
 		if strippedThisMsg {
 			strippedThinking = true
 		}
 
+		if role == "system" {
+			systemParts = append(systemParts, parts...)
+			continue
+		}
+
 		// 只有 Gemini 模型支持 dummy thinking block workaround
 		// 只对最后一条 assistant 消息添加（Pre-fill 场景）
 		// 历史 assistant 消息不能添加没有 signature 的 dummy thinking block
@@ -406,7 +418,7 @@ func buildContents(messages []ClaudeMessage, toolIDToName map[string]string, isT
 		})
 	}
 
-	return contents, strippedThinking, nil
+	return contents, systemParts, strippedThinking, nil
 }
 
 // DummyThoughtSignature 用于跳过 Gemini 3 thought_signature 验证

backend/internal/pkg/antigravity/request_transformer_test.go

@@ -424,6 +424,115 @@ func TestTransformClaudeToGeminiWithOptions_PreservesBillingHeaderSystemBlock(t
 	}
 }
 
+func TestTransformClaudeToGeminiWithOptions_MessageRoles(t *testing.T) {
+	transform := func(t *testing.T, claudeReq *ClaudeRequest) V1InternalRequest {
+		t.Helper()
+
+		body, err := TransformClaudeToGeminiWithOptions(claudeReq, "project-1", "gemini-2.5-flash", DefaultTransformOptions())
+		require.NoError(t, err)
+
+		var req V1InternalRequest
+		require.NoError(t, json.Unmarshal(body, &req))
+		return req
+	}
+
+	systemText := func(content *GeminiContent) string {
+		if content == nil {
+			return ""
+		}
+		var texts []string
+		for _, part := range content.Parts {
+			texts = append(texts, part.Text)
+		}
+		return strings.Join(texts, "\n")
+	}
+
+	t.Run("message system role moves to system instruction", func(t *testing.T) {
+		req := transform(t, &ClaudeRequest{
+			Model: "claude-3-5-sonnet-latest",
+			Messages: []ClaudeMessage{
+				{
+					Role:    "system",
+					Content: json.RawMessage(`[{"type":"text","text":"skills context"}]`),
+				},
+				{
+					Role:    "user",
+					Content: json.RawMessage(`"hello"`),
+				},
+			},
+		})
+
+		require.Len(t, req.Request.Contents, 1)
+		require.Equal(t, "user", req.Request.Contents[0].Role)
+		require.Contains(t, systemText(req.Request.SystemInstruction), "skills context")
+		for _, content := range req.Request.Contents {
+			require.NotEqual(t, "system", content.Role)
+		}
+	})
+
+	t.Run("assistant role still maps to model", func(t *testing.T) {
+		req := transform(t, &ClaudeRequest{
+			Model: "claude-3-5-sonnet-latest",
+			Messages: []ClaudeMessage{
+				{
+					Role:    "assistant",
+					Content: json.RawMessage(`"hello from assistant"`),
+				},
+			},
+		})
+
+		require.Len(t, req.Request.Contents, 1)
+		require.Equal(t, "model", req.Request.Contents[0].Role)
+		require.Equal(t, "hello from assistant", req.Request.Contents[0].Parts[0].Text)
+	})
+
+	t.Run("top level and message system instructions are merged", func(t *testing.T) {
+		req := transform(t, &ClaudeRequest{
+			Model:  "claude-3-5-sonnet-latest",
+			System: json.RawMessage(`"top level system"`),
+			Messages: []ClaudeMessage{
+				{
+					Role:    "system",
+					Content: json.RawMessage(`"message system"`),
+				},
+				{
+					Role:    "user",
+					Content: json.RawMessage(`"hello"`),
+				},
+			},
+		})
+
+		mergedSystem := systemText(req.Request.SystemInstruction)
+		require.Contains(t, mergedSystem, "top level system")
+		require.Contains(t, mergedSystem, "message system")
+		require.Less(t, strings.Index(mergedSystem, "top level system"), strings.Index(mergedSystem, "message system"))
+		require.Len(t, req.Request.Contents, 1)
+		require.Equal(t, "user", req.Request.Contents[0].Role)
+	})
+
+	t.Run("ordinary user assistant conversation is unchanged", func(t *testing.T) {
+		req := transform(t, &ClaudeRequest{
+			Model: "claude-3-5-sonnet-latest",
+			Messages: []ClaudeMessage{
+				{
+					Role:    "user",
+					Content: json.RawMessage(`"question"`),
+				},
+				{
+					Role:    "assistant",
+					Content: json.RawMessage(`"answer"`),
+				},
+			},
+		})
+
+		require.Len(t, req.Request.Contents, 2)
+		require.Equal(t, "user", req.Request.Contents[0].Role)
+		require.Equal(t, "question", req.Request.Contents[0].Parts[0].Text)
+		require.Equal(t, "model", req.Request.Contents[1].Role)
+		require.Equal(t, "answer", req.Request.Contents[1].Parts[0].Text)
+	})
+}
+
 func TestTransformClaudeToGeminiWithOptions_PreservesWebSearchAlongsideFunctions(t *testing.T) {
 	claudeReq := &ClaudeRequest{
 		Model: "claude-3-5-sonnet-latest",