diff --git a/backend/internal/pkg/geminicli/constants.go b/backend/internal/pkg/geminicli/constants.go
index 9b204640..19a3ddd9 100644
--- a/backend/internal/pkg/geminicli/constants.go
+++ b/backend/internal/pkg/geminicli/constants.go
@@ -3,8 +3,8 @@ package geminicli
 
 import (
 	"fmt"
+	"os"
 	"runtime"
-	"strings"
 	"time"
 )
 
@@ -51,15 +51,49 @@ const (
 
 	SessionTTL = 30 * time.Minute
 
-	// GeminiCLIUserAgent mimics Gemini CLI to maximize compatibility with internal endpoints.
-	// Note: The real Gemini CLI uses OS-appropriate platform strings.
-	// Use GetGeminiCLIUserAgent() for runtime-aware User-Agent.
-	GeminiCLIUserAgent = "GeminiCLI/0.1.5"
+	// GeminiCLIUserAgent 静态回退值（不含 model）
+	// 优先使用 GetGeminiCLIUserAgent(model) 获取完整格式
+	GeminiCLIUserAgent = "GeminiCLI/0.33.1"
+
+	// FakeNodeVersion 模拟真实 Gemini CLI 的 Node.js 版本
+	// 用于 x-goog-api-client 和 token exchange User-Agent
+	FakeNodeVersion = "24.13.1"
+
+	// GoogleAuthLibraryUA 模拟 google-auth-library 的 User-Agent
+	// 真实 Gemini CLI token exchange 由 google-auth-library 发起
+	GoogleAuthLibraryUA = "google-api-nodejs-client"
 )
 
-// GetGeminiCLIUserAgent 返回带有正确平台信息的 Gemini CLI User-Agent
-func GetGeminiCLIUserAgent() string {
-	osName := strings.Title(runtime.GOOS) // Darwin, Linux, Windows
-	arch := strings.ToUpper(runtime.GOARCH)
-	return fmt.Sprintf("GeminiCLI/0.1.5 (%s; %s)", osName, arch)
+// defaultGeminiCLIVersion 可通过环境变量 GEMINI_CLI_VERSION 覆盖
+var defaultGeminiCLIVersion = "0.33.1"
+
+func init() {
+	if v := os.Getenv("GEMINI_CLI_VERSION"); v != "" {
+		defaultGeminiCLIVersion = v
+	}
+}
+
+// GetGeminiCLIUserAgent 返回匹配真实 Gemini CLI 格式的 User-Agent
+// 真实格式: GeminiCLI/{version}/{model} ({platform}; {arch})
+// 示例: GeminiCLI/0.33.1/gemini-2.5-pro (darwin; arm64)
+func GetGeminiCLIUserAgent(model ...string) string {
+	m := "unknown"
+	if len(model) > 0 && model[0] != "" {
+		m = model[0]
+	}
+	return fmt.Sprintf("GeminiCLI/%s/%s (%s; %s)",
+		defaultGeminiCLIVersion, m, runtime.GOOS, runtime.GOARCH)
+}
+
+// GetGeminiCLIGoogAPIClient 返回 x-goog-api-client 头的值
+// 真实 Gemini CLI 通过 google-auth-library DefaultTransporter 自动注入:
+// gl-node/{nodeVersion}
+func GetGeminiCLIGoogAPIClient() string {
+	return fmt.Sprintf("gl-node/%s", FakeNodeVersion)
+}
+
+// GetGeminiCLITokenExchangeUA 返回 token exchange/refresh 时的 User-Agent
+// 真实 Gemini CLI 使用 google-auth-library 发起 token 交换
+func GetGeminiCLITokenExchangeUA() string {
+	return GoogleAuthLibraryUA
 }
diff --git a/backend/internal/repository/gemini_oauth_client.go b/backend/internal/repository/gemini_oauth_client.go
index eb14f313..3841dfe0 100644
--- a/backend/internal/repository/gemini_oauth_client.go
+++ b/backend/internal/repository/gemini_oauth_client.go
@@ -63,6 +63,8 @@ func (c *geminiOAuthClient) ExchangeCode(ctx context.Context, oauthType, code, c
 	resp, err := client.R().
 		SetContext(ctx).
 		SetFormDataFromValues(formData).
+		SetHeader("User-Agent", geminicli.GetGeminiCLITokenExchangeUA()).
+		SetHeader("X-Goog-Api-Client", geminicli.GetGeminiCLIGoogAPIClient()).
 		SetSuccessResult(&tokenResp).
 		Post(c.tokenURL)
 	if err != nil {
@@ -106,6 +108,8 @@ func (c *geminiOAuthClient) RefreshToken(ctx context.Context, oauthType, refresh
 	resp, err := client.R().
 		SetContext(ctx).
 		SetFormDataFromValues(formData).
+		SetHeader("User-Agent", geminicli.GetGeminiCLITokenExchangeUA()).
+		SetHeader("X-Goog-Api-Client", geminicli.GetGeminiCLIGoogAPIClient()).
 		SetSuccessResult(&tokenResp).
 		Post(c.tokenURL)
 	if err != nil {
diff --git a/backend/internal/repository/geminicli_codeassist_client.go b/backend/internal/repository/geminicli_codeassist_client.go
index b5bc6497..7e0d85b3 100644
--- a/backend/internal/repository/geminicli_codeassist_client.go
+++ b/backend/internal/repository/geminicli_codeassist_client.go
@@ -34,7 +34,8 @@ func (c *geminiCliCodeAssistClient) LoadCodeAssist(ctx context.Context, accessTo
 		SetContext(ctx).
 		SetHeader("Authorization", "Bearer "+accessToken).
 		SetHeader("Content-Type", "application/json").
-		SetHeader("User-Agent", geminicli.GeminiCLIUserAgent).
+		SetHeader("User-Agent", geminicli.GetGeminiCLIUserAgent()).
+		SetHeader("X-Goog-Api-Client", geminicli.GetGeminiCLIGoogAPIClient()).
 		SetBody(reqBody).
 		SetSuccessResult(&out).
 		Post(c.baseURL + "/v1internal:loadCodeAssist")
@@ -78,7 +79,8 @@ func (c *geminiCliCodeAssistClient) OnboardUser(ctx context.Context, accessToken
 		SetContext(ctx).
 		SetHeader("Authorization", "Bearer "+accessToken).
 		SetHeader("Content-Type", "application/json").
-		SetHeader("User-Agent", geminicli.GeminiCLIUserAgent).
+		SetHeader("User-Agent", geminicli.GetGeminiCLIUserAgent()).
+		SetHeader("X-Goog-Api-Client", geminicli.GetGeminiCLIGoogAPIClient()).
 		SetBody(reqBody).
 		SetSuccessResult(&out).
 		Post(c.baseURL + "/v1internal:onboardUser")
@@ -116,7 +118,7 @@ func createGeminiCliReqClient(proxyURL string) (*req.Client, error) {
 func defaultLoadCodeAssistRequest() *geminicli.LoadCodeAssistRequest {
 	return &geminicli.LoadCodeAssistRequest{
 		Metadata: geminicli.LoadCodeAssistMetadata{
-			IDEType:    "ANTIGRAVITY",
+			IDEType:    "IDE_UNSPECIFIED",
 			Platform:   "PLATFORM_UNSPECIFIED",
 			PluginType: "GEMINI",
 		},
@@ -127,7 +129,7 @@ func defaultOnboardUserRequest() *geminicli.OnboardUserRequest {
 	return &geminicli.OnboardUserRequest{
 		TierID: "LEGACY",
 		Metadata: geminicli.LoadCodeAssistMetadata{
-			IDEType:    "ANTIGRAVITY",
+			IDEType:    "IDE_UNSPECIFIED",
 			Platform:   "PLATFORM_UNSPECIFIED",
 			PluginType: "GEMINI",
 		},
diff --git a/backend/internal/service/account_test_service.go b/backend/internal/service/account_test_service.go
index 12617336..0ba0e9a3 100644
--- a/backend/internal/service/account_test_service.go
+++ b/backend/internal/service/account_test_service.go
@@ -1464,7 +1464,8 @@ func (s *AccountTestService) buildCodeAssistRequest(ctx context.Context, accessT
 
 	req.Header.Set("Content-Type", "application/json")
 	req.Header.Set("Authorization", "Bearer "+accessToken)
-	req.Header.Set("User-Agent", geminicli.GeminiCLIUserAgent)
+	req.Header.Set("User-Agent", geminicli.GetGeminiCLIUserAgent())
+	req.Header.Set("X-Goog-Api-Client", geminicli.GetGeminiCLIGoogAPIClient())
 
 	return req, nil
 }
diff --git a/backend/internal/service/gemini_messages_compat_service.go b/backend/internal/service/gemini_messages_compat_service.go
index 0e0898b6..490722ce 100644
--- a/backend/internal/service/gemini_messages_compat_service.go
+++ b/backend/internal/service/gemini_messages_compat_service.go
@@ -669,7 +669,8 @@ func (s *GeminiMessagesCompatService) Forward(ctx context.Context, c *gin.Contex
 				}
 				upstreamReq.Header.Set("Content-Type", "application/json")
 				upstreamReq.Header.Set("Authorization", "Bearer "+accessToken)
-				upstreamReq.Header.Set("User-Agent", geminicli.GetGeminiCLIUserAgent())
+				upstreamReq.Header.Set("User-Agent", geminicli.GetGeminiCLIUserAgent(mappedModel))
+				upstreamReq.Header.Set("X-Goog-Api-Client", geminicli.GetGeminiCLIGoogAPIClient())
 				return upstreamReq, "x-request-id", nil
 			} else {
 				// Mode 2: AI Studio API with OAuth (like API key mode, but using Bearer token)
@@ -690,7 +691,8 @@ func (s *GeminiMessagesCompatService) Forward(ctx context.Context, c *gin.Contex
 				}
 				upstreamReq.Header.Set("Content-Type", "application/json")
 				upstreamReq.Header.Set("Authorization", "Bearer "+accessToken)
-				upstreamReq.Header.Set("User-Agent", geminicli.GetGeminiCLIUserAgent())
+				upstreamReq.Header.Set("User-Agent", geminicli.GetGeminiCLIUserAgent(mappedModel))
+				upstreamReq.Header.Set("X-Goog-Api-Client", geminicli.GetGeminiCLIGoogAPIClient())
 				return upstreamReq, "x-request-id", nil
 			}
 		}
@@ -1171,7 +1173,8 @@ func (s *GeminiMessagesCompatService) ForwardNative(ctx context.Context, c *gin.
 				}
 				upstreamReq.Header.Set("Content-Type", "application/json")
 				upstreamReq.Header.Set("Authorization", "Bearer "+accessToken)
-				upstreamReq.Header.Set("User-Agent", geminicli.GetGeminiCLIUserAgent())
+				upstreamReq.Header.Set("User-Agent", geminicli.GetGeminiCLIUserAgent(mappedModel))
+				upstreamReq.Header.Set("X-Goog-Api-Client", geminicli.GetGeminiCLIGoogAPIClient())
 				return upstreamReq, "x-request-id", nil
 			} else {
 				// Mode 2: AI Studio API with OAuth (like API key mode, but using Bearer token)
@@ -1192,7 +1195,8 @@ func (s *GeminiMessagesCompatService) ForwardNative(ctx context.Context, c *gin.
 				}
 				upstreamReq.Header.Set("Content-Type", "application/json")
 				upstreamReq.Header.Set("Authorization", "Bearer "+accessToken)
-				upstreamReq.Header.Set("User-Agent", geminicli.GetGeminiCLIUserAgent())
+				upstreamReq.Header.Set("User-Agent", geminicli.GetGeminiCLIUserAgent(mappedModel))
+				upstreamReq.Header.Set("X-Goog-Api-Client", geminicli.GetGeminiCLIGoogAPIClient())
 				return upstreamReq, "x-request-id", nil
 			}
 		}
diff --git a/backend/internal/service/gemini_oauth_service.go b/backend/internal/service/gemini_oauth_service.go
index 08a74a37..091f9aa3 100644
--- a/backend/internal/service/gemini_oauth_service.go
+++ b/backend/internal/service/gemini_oauth_service.go
@@ -1037,7 +1037,8 @@ func fetchProjectIDFromResourceManager(ctx context.Context, accessToken, proxyUR
 	}
 
 	req.Header.Set("Authorization", "Bearer "+accessToken)
-	req.Header.Set("User-Agent", geminicli.GeminiCLIUserAgent)
+	req.Header.Set("User-Agent", geminicli.GetGeminiCLIUserAgent())
+	req.Header.Set("X-Goog-Api-Client", geminicli.GetGeminiCLIGoogAPIClient())
 
 	client, err := httpclient.GetClient(httpclient.Options{
 		ProxyURL:           strings.TrimSpace(proxyURL),