diff --git a/backend/internal/session/memory_test.go b/backend/internal/session/memory_test.go
new file mode 100644
index 0000000..acfa433
--- /dev/null
+++ b/backend/internal/session/memory_test.go
@@ -0,0 +1,286 @@
+package session
+
+import (
+	"context"
+	"testing"
+	"time"
+
+	"github.com/hhs/camtalk/internal/logger"
+	"github.com/hhs/camtalk/internal/models"
+)
+
+func init() {
+	logger.Init("debug", "console")
+}
+
+func TestCreateAndGet(t *testing.T) {
+	m := NewMemoryManager(30*time.Minute, 20)
+	defer m.Stop()
+	ctx := context.Background()
+
+	config := models.DefaultConfig()
+	id, err := m.Create(ctx, config)
+	if err != nil {
+		t.Fatalf("Create: %v", err)
+	}
+	if id == "" {
+		t.Fatal("Create returned empty ID")
+	}
+
+	sess, err := m.Get(ctx, id)
+	if err != nil {
+		t.Fatalf("Get: %v", err)
+	}
+	if sess.ID != id {
+		t.Errorf("ID = %q, want %q", sess.ID, id)
+	}
+	if sess.Config.Language != "zh-CN" {
+		t.Errorf("Language = %q, want %q", sess.Config.Language, "zh-CN")
+	}
+}
+
+func TestGetNotFound(t *testing.T) {
+	m := NewMemoryManager(30*time.Minute, 20)
+	defer m.Stop()
+	ctx := context.Background()
+
+	_, err := m.Get(ctx, "nonexistent")
+	if err != ErrSessionNotFound {
+		t.Errorf("Get nonexistent: err = %v, want ErrSessionNotFound", err)
+	}
+}
+
+func TestExpire(t *testing.T) {
+	// 使用极短 TTL 测试过期
+	m := NewMemoryManager(50*time.Millisecond, 20)
+	defer m.Stop()
+	ctx := context.Background()
+
+	id, _ := m.Create(ctx, models.DefaultConfig())
+
+	// 未过期时应能获取
+	_, err := m.Get(ctx, id)
+	if err != nil {
+		t.Fatalf("Get before expire: %v", err)
+	}
+
+	// 等待过期
+	time.Sleep(80 * time.Millisecond)
+
+	_, err = m.Get(ctx, id)
+	if err != ErrSessionNotFound {
+		t.Errorf("Get after expire: err = %v, want ErrSessionNotFound", err)
+	}
+}
+
+func TestDestroy(t *testing.T) {
+	m := NewMemoryManager(30*time.Minute, 20)
+	defer m.Stop()
+	ctx := context.Background()
+
+	id, _ := m.Create(ctx, models.DefaultConfig())
+
+	if err := m.Destroy(ctx, id); err != nil {
+		t.Fatalf("Destroy: %v", err)
+	}
+
+	_, err := m.Get(ctx, id)
+	if err != ErrSessionNotFound {
+		t.Errorf("Get after Destroy: err = %v, want ErrSessionNotFound", err)
+	}
+}
+
+func TestDestroyNotFound(t *testing.T) {
+	m := NewMemoryManager(30*time.Minute, 20)
+	defer m.Stop()
+	ctx := context.Background()
+
+	err := m.Destroy(ctx, "nonexistent")
+	if err != ErrSessionNotFound {
+		t.Errorf("Destroy nonexistent: err = %v, want ErrSessionNotFound", err)
+	}
+}
+
+func TestAppendMessageAndGetHistory(t *testing.T) {
+	m := NewMemoryManager(30*time.Minute, 20)
+	defer m.Stop()
+	ctx := context.Background()
+
+	id, _ := m.Create(ctx, models.DefaultConfig())
+
+	msgs := []models.Message{
+		{Role: "user", Content: "你好"},
+		{Role: "assistant", Content: "你好！有什么可以帮你的吗？"},
+		{Role: "user", Content: "这是什么？"},
+		{Role: "assistant", Content: "这是一朵花。"},
+	}
+
+	for _, msg := range msgs {
+		if err := m.AppendMessage(ctx, id, msg); err != nil {
+			t.Fatalf("AppendMessage: %v", err)
+		}
+	}
+
+	history, err := m.GetHistory(ctx, id, 0)
+	if err != nil {
+		t.Fatalf("GetHistory: %v", err)
+	}
+	if len(history) != 4 {
+		t.Fatalf("GetHistory len = %d, want 4", len(history))
+	}
+	if history[0].Content != "你好" {
+		t.Errorf("history[0] = %q, want %q", history[0].Content, "你好")
+	}
+}
+
+func TestGetHistoryLimit(t *testing.T) {
+	m := NewMemoryManager(30*time.Minute, 20)
+	defer m.Stop()
+	ctx := context.Background()
+
+	id, _ := m.Create(ctx, models.DefaultConfig())
+
+	for i := 0; i < 10; i++ {
+		m.AppendMessage(ctx, id, models.Message{Role: "user", Content: "msg"})
+	}
+
+	history, err := m.GetHistory(ctx, id, 3)
+	if err != nil {
+		t.Fatalf("GetHistory: %v", err)
+	}
+	if len(history) != 3 {
+		t.Fatalf("GetHistory limit=3: len = %d, want 3", len(history))
+	}
+}
+
+func TestHistoryLimit(t *testing.T) {
+	const maxHistory = 5
+	m := NewMemoryManager(30*time.Minute, maxHistory)
+	defer m.Stop()
+	ctx := context.Background()
+
+	id, _ := m.Create(ctx, models.DefaultConfig())
+
+	// 插入超过上限的消息
+	for i := 0; i < 10; i++ {
+		m.AppendMessage(ctx, id, models.Message{Role: "user", Content: "msg"})
+	}
+
+	history, err := m.GetHistory(ctx, id, 0)
+	if err != nil {
+		t.Fatalf("GetHistory: %v", err)
+	}
+	if len(history) != maxHistory {
+		t.Fatalf("GetHistory after overflow: len = %d, want %d", len(history), maxHistory)
+	}
+}
+
+func TestUpdateConfig(t *testing.T) {
+	m := NewMemoryManager(30*time.Minute, 20)
+	defer m.Stop()
+	ctx := context.Background()
+
+	id, _ := m.Create(ctx, models.DefaultConfig())
+
+	ttsEnabled := false
+	detailLevel := "high"
+	patch := models.SessionConfigPatch{
+		TTSEnabled:  &ttsEnabled,
+		DetailLevel: &detailLevel,
+	}
+
+	if err := m.UpdateConfig(ctx, id, patch); err != nil {
+		t.Fatalf("UpdateConfig: %v", err)
+	}
+
+	sess, _ := m.Get(ctx, id)
+	if sess.Config.TTSEnabled != false {
+		t.Errorf("TTSEnabled = %v, want false", sess.Config.TTSEnabled)
+	}
+	if sess.Config.DetailLevel != "high" {
+		t.Errorf("DetailLevel = %q, want %q", sess.Config.DetailLevel, "high")
+	}
+	// Language 未传，应保持原值
+	if sess.Config.Language != "zh-CN" {
+		t.Errorf("Language = %q, want %q", sess.Config.Language, "zh-CN")
+	}
+}
+
+func TestActiveRequest(t *testing.T) {
+	m := NewMemoryManager(30*time.Minute, 20)
+	defer m.Stop()
+	ctx := context.Background()
+
+	id, _ := m.Create(ctx, models.DefaultConfig())
+
+	// 初始应为空
+	reqID, err := m.GetActiveRequestID(ctx, id)
+	if err != nil {
+		t.Fatalf("GetActiveRequestID: %v", err)
+	}
+	if reqID != "" {
+		t.Errorf("initial active request = %q, want empty", reqID)
+	}
+
+	// 设置
+	if err := m.SetActiveRequest(ctx, id, "req-123"); err != nil {
+		t.Fatalf("SetActiveRequest: %v", err)
+	}
+	reqID, _ = m.GetActiveRequestID(ctx, id)
+	if reqID != "req-123" {
+		t.Errorf("active request = %q, want %q", reqID, "req-123")
+	}
+
+	// 清除
+	if err := m.ClearActiveRequest(ctx, id); err != nil {
+		t.Fatalf("ClearActiveRequest: %v", err)
+	}
+	reqID, _ = m.GetActiveRequestID(ctx, id)
+	if reqID != "" {
+		t.Errorf("active request after clear = %q, want empty", reqID)
+	}
+}
+
+func TestTouchRefreshesTTL(t *testing.T) {
+	m := NewMemoryManager(100*time.Millisecond, 20)
+	defer m.Stop()
+	ctx := context.Background()
+
+	id, _ := m.Create(ctx, models.DefaultConfig())
+
+	// 50ms 后 Touch，应重置 TTL
+	time.Sleep(50 * time.Millisecond)
+	if err := m.Touch(ctx, id); err != nil {
+		t.Fatalf("Touch: %v", err)
+	}
+
+	// 再等 70ms（距创建 120ms，但距 Touch 只有 70ms），不应过期
+	time.Sleep(70 * time.Millisecond)
+	_, err := m.Get(ctx, id)
+	if err != nil {
+		t.Errorf("Get after Touch: %v, want nil (should not expire yet)", err)
+	}
+
+	// 再等 50ms（距 Touch 120ms），应过期
+	time.Sleep(50 * time.Millisecond)
+	_, err = m.Get(ctx, id)
+	if err != ErrSessionNotFound {
+		t.Errorf("Get after TTL: err = %v, want ErrSessionNotFound", err)
+	}
+}
+
+func TestActiveCount(t *testing.T) {
+	m := NewMemoryManager(30*time.Minute, 20)
+	defer m.Stop()
+	ctx := context.Background()
+
+	if m.ActiveCount() != 0 {
+		t.Errorf("initial ActiveCount = %d, want 0", m.ActiveCount())
+	}
+
+	m.Create(ctx, models.DefaultConfig())
+	m.Create(ctx, models.DefaultConfig())
+	if m.ActiveCount() != 2 {
+		t.Errorf("ActiveCount = %d, want 2", m.ActiveCount())
+	}
+}