diff --git a/service/ccm/service.go b/service/ccm/service.go
index 8a9d8f17f..d3f76381f 100644
--- a/service/ccm/service.go
+++ b/service/ccm/service.go
@@ -5,6 +5,8 @@ import (
 	"encoding/json"
 	"net/http"
 	"strings"
+	"sync"
+	"time"
 
 	"github.com/sagernet/sing-box/adapter"
 	boxService "github.com/sagernet/sing-box/adapter/service"
@@ -163,10 +165,29 @@ type Service struct {
 	allCredentials []Credential
 	userConfigMap  map[string]*option.CCMUser
 
+	sessionModelAccess sync.Mutex
+	sessionModels      map[sessionModelKey]time.Time
+
 	statusSubscriber *observable.Subscriber[struct{}]
 	statusObserver   *observable.Observer[struct{}]
 }
 
+type sessionModelKey struct {
+	sessionID string
+	model     string
+}
+
+func (s *Service) cleanSessionModels() {
+	now := time.Now()
+	s.sessionModelAccess.Lock()
+	for key, createdAt := range s.sessionModels {
+		if now.Sub(createdAt) > sessionExpiry {
+			delete(s.sessionModels, key)
+		}
+	}
+	s.sessionModelAccess.Unlock()
+}
+
 func NewService(ctx context.Context, logger log.ContextLogger, tag string, options option.CCMServiceOptions) (adapter.Service, error) {
 	initCCMUserAgent(logger)
 
@@ -212,6 +233,7 @@ func NewService(ctx context.Context, logger log.ContextLogger, tag string, optio
 			Listen:  options.ListenOptions,
 		}),
 		userManager:      userManager,
+		sessionModels:    make(map[sessionModelKey]time.Time),
 		statusSubscriber: statusSubscriber,
 		statusObserver:   observable.NewObserver[struct{}](statusSubscriber, 8),
 	}
diff --git a/service/ccm/service_handler.go b/service/ccm/service_handler.go
index 9ce78db53..94af4e90e 100644
--- a/service/ccm/service_handler.go
+++ b/service/ccm/service_handler.go
@@ -218,6 +218,7 @@ func (s *Service) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 	}
 
 	provider.pollIfStale()
+	s.cleanSessionModels()
 
 	anthropicBetaHeader := r.Header.Get("anthropic-beta")
 	if isFastModeRequest(anthropicBetaHeader) {
@@ -235,7 +236,22 @@ func (s *Service) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 		writeNonRetryableCredentialError(w, r, unavailableCredentialMessage(provider, err.Error()))
 		return
 	}
-	if isNew {
+	modelDisplay := requestModel
+	if requestModel != "" && isExtendedContextRequest(anthropicBetaHeader) {
+		modelDisplay += "[1m]"
+	}
+	isNewModel := false
+	if sessionID != "" && modelDisplay != "" {
+		key := sessionModelKey{sessionID, modelDisplay}
+		s.sessionModelAccess.Lock()
+		_, exists := s.sessionModels[key]
+		if !exists {
+			s.sessionModels[key] = time.Now()
+			isNewModel = true
+		}
+		s.sessionModelAccess.Unlock()
+	}
+	if isNew || isNewModel {
 		logParts := []any{"assigned credential ", selectedCredential.tagName()}
 		if sessionID != "" {
 			logParts = append(logParts, " for session ", sessionID)
@@ -243,11 +259,7 @@ func (s *Service) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 		if username != "" {
 			logParts = append(logParts, " by user ", username)
 		}
-		if requestModel != "" {
-			modelDisplay := requestModel
-			if isExtendedContextRequest(anthropicBetaHeader) {
-				modelDisplay += "[1m]"
-			}
+		if modelDisplay != "" {
 			logParts = append(logParts, ", model=", modelDisplay)
 		}
 		s.logger.DebugContext(ctx, logParts...)