diff --git a/internal/handler/emby_playback.go b/internal/handler/emby_playback.go
index 5102ce2..0450f7a 100644
--- a/internal/handler/emby_playback.go
+++ b/internal/handler/emby_playback.go
@@ -1,10 +1,13 @@
 package handler
 
 import (
+	"context"
 	"errors"
 	"net/http"
 	"net/url"
 	"strings"
+	"sync"
+	"time"
 
 	"github.com/gin-gonic/gin"
 
@@ -24,10 +27,98 @@ func embyPlaybackInfoHandler(svc *service.Container) gin.HandlerFunc {
 			return
 		}
 		embyAttachRequestTokenToMediaSources(c, out)
+		// 在后台把本次条目的云盘直链换好：播放器拿到 PlaybackInfo 后通常还要
+		// 1–2 秒才请求 /Videos/{id}/stream，把换链开销落在这段等待里。
+		embyPrewarmPlaybackTargets(svc, c, out)
 		c.JSON(http.StatusOK, out)
 	}
 }
 
+// embyPrewarmTimeout 是单次预热的等待上限。115 开放平台在跨太平洋线路上单次
+// 换链实测 0.4–1.1s，这里给足余量；超时只是没预热成功，不影响后续播放。
+const embyPrewarmTimeout = 10 * time.Second
+
+// embyPrewarmInFlight 去重同一个条目的并发预热（首页刷新会并发请求多个接口，
+// 同一条目可能在短时间内被多次请求）。
+var embyPrewarmInFlight sync.Map
+
+// embyPrewarmSlots 限制同时进行的预热数量。客户端可能批量预取 PlaybackInfo
+// （逐个剧集的预取请求），预热只是优化，不能反过来把 115 换链接口打出突发。
+// 名额满时直接跳过：排队等待的预热往往等真正播放时已经没意义了。
+var embyPrewarmSlots = make(chan struct{}, 4)
+
+// embyPrewarmPlaybackTargets 在后台预热本次 PlaybackInfo 涉及条目的云盘直链。
+//
+// 起播链路里最贵的一步是「服务端拿 pickcode 去 115 开放平台换直链」：服务器在
+// 洛杉矶、115 接口在国内，冷启动实测 0.4–1.1s；之后 45 分钟内命中进程内缓存。
+// 播放器在 PlaybackInfo 与真正拉流之间有几秒间隔，这里把换链放到那段间隔里，
+// 起播时就只剩纯网络耗时。
+//
+// 只处理云盘/strm 条目，且失败一律静默忽略：预热是尽力而为的优化，不能影响
+// PlaybackInfo 的正常返回。
+func embyPrewarmPlaybackTargets(svc *service.Container, c *gin.Context, out map[string]any) {
+	if svc == nil || svc.Strm == nil || svc.Repo == nil || svc.Repo.Media == nil || out == nil {
+		return
+	}
+	ids := embyPrewarmMediaIDs(out)
+	if len(ids) == 0 {
+		return
+	}
+	userAgent := c.GetHeader("User-Agent")
+	// 预热是给「后续请求」用的：即便本次 PlaybackInfo 的连接断开，
+	// 也要把换链跑完。
+	base := context.WithoutCancel(c.Request.Context())
+	for _, mediaID := range ids {
+		if _, loaded := embyPrewarmInFlight.LoadOrStore(mediaID, struct{}{}); loaded {
+			continue
+		}
+		go func(id string) {
+			defer embyPrewarmInFlight.Delete(id)
+			select {
+			case embyPrewarmSlots <- struct{}{}:
+				defer func() { <-embyPrewarmSlots }()
+			default:
+				return
+			}
+			ctx, cancel := context.WithTimeout(base, embyPrewarmTimeout)
+			defer cancel()
+			m, err := svc.Repo.Media.FindByID(ctx, id)
+			if err != nil || m == nil {
+				return
+			}
+			raw := strings.TrimSpace(m.STRMURL)
+			if raw == "" || !service.IsStrmMediaRow(m) {
+				return
+			}
+			// 解析结果由 strm 层按 pickcode+UA 缓存；已缓存时这里是空转。
+			_, _ = svc.Strm.ResolvePlayTargetWithUA(ctx, raw, userAgent)
+		}(mediaID)
+	}
+}
+
+// embyPrewarmMediaIDs 取出 PlaybackInfo 载荷里 MediaSources 的条目 ID。
+func embyPrewarmMediaIDs(out map[string]any) []string {
+	sources, ok := out["MediaSources"].([]map[string]any)
+	if !ok || len(sources) == 0 {
+		return nil
+	}
+	ids := make([]string, 0, len(sources))
+	seen := make(map[string]struct{}, len(sources))
+	for _, src := range sources {
+		id, _ := src["Id"].(string)
+		id = strings.TrimSpace(id)
+		if id == "" {
+			continue
+		}
+		if _, dup := seen[id]; dup {
+			continue
+		}
+		seen[id] = struct{}{}
+		ids = append(ids, id)
+	}
+	return ids
+}
+
 // embySubtitleStreamHandler serves an external subtitle track advertised in a
 // MediaSource's MediaStreams via its Emby index
 // (/Videos/:id/Subtitles/:index/Stream). The index maps to a discovered
diff --git a/internal/handler/emby_playback_prewarm_test.go b/internal/handler/emby_playback_prewarm_test.go
new file mode 100644
index 0000000..80bdcce
--- /dev/null
+++ b/internal/handler/emby_playback_prewarm_test.go
@@ -0,0 +1,159 @@
+package handler
+
+import (
+	"net/http"
+	"net/http/httptest"
+	"testing"
+	"time"
+
+	"github.com/gin-gonic/gin"
+	"github.com/glebarez/sqlite"
+	"go.uber.org/zap"
+	"gorm.io/gorm"
+
+	"github.com/truewhile/MeBox/internal/config"
+	"github.com/truewhile/MeBox/internal/model"
+	"github.com/truewhile/MeBox/internal/repository"
+	"github.com/truewhile/MeBox/internal/service"
+)
+
+func newPrewarmTestContainer(t *testing.T) *service.Container {
+	t.Helper()
+	db, err := gorm.Open(sqlite.Open(":memory:"), &gorm.Config{})
+	if err != nil {
+		t.Fatalf("open db: %v", err)
+	}
+	if err := db.AutoMigrate(&model.Media{}, &model.Setting{}, &model.StrmAccount{}); err != nil {
+		t.Fatalf("migrate: %v", err)
+	}
+	if sqlDB, err := db.DB(); err == nil {
+		// 内存库 + 后台预热协程：限制单连接，避免新连接拿到空白的 :memory:。
+		sqlDB.SetMaxOpenConns(1)
+	}
+	repos := repository.New(db)
+	return &service.Container{
+		Log:  zap.NewNop(),
+		Repo: repos,
+		Strm: service.NewStrmService(&config.Config{}, zap.NewNop(), repos, nil),
+	}
+}
+
+func newPrewarmTestContext() *gin.Context {
+	gin.SetMode(gin.TestMode)
+	c, _ := gin.CreateTestContext(httptest.NewRecorder())
+	c.Request = httptest.NewRequest(http.MethodPost, "/emby/Items/media-1/PlaybackInfo", nil)
+	c.Request.Header.Set("User-Agent", "RodelPlayer/2.2607.7.0")
+	return c
+}
+
+func TestEmbyPrewarmMediaIDsExtractsDeduplicates(t *testing.T) {
+	out := map[string]any{
+		"MediaSources": []map[string]any{
+			{"Id": "src-1"},
+			{"Id": " src-1 "},
+			{"Id": "src-2"},
+			{"Id": ""},
+			{"Name": "no id"},
+		},
+	}
+	got := embyPrewarmMediaIDs(out)
+	if len(got) != 2 || got[0] != "src-1" || got[1] != "src-2" {
+		t.Fatalf("ids = %v, want [src-1 src-2]", got)
+	}
+	if got := embyPrewarmMediaIDs(map[string]any{}); len(got) != 0 {
+		t.Fatalf("missing MediaSources should yield no ids, got %v", got)
+	}
+	if got := embyPrewarmMediaIDs(map[string]any{"MediaSources": []any{}}); len(got) != 0 {
+		t.Fatalf("foreign payload shape should yield no ids, got %v", got)
+	}
+}
+
+// 预热是异步的：调用必须立即返回，并且协程结束后不能残留去重标记。
+func TestEmbyPrewarmPlaybackTargetsRunsAsyncAndCleansUp(t *testing.T) {
+	svc := newPrewarmTestContainer(t)
+	if err := svc.Repo.DB.Create(&model.Media{
+		Base:      model.Base{ID: "media-1"},
+		Title:     "Cloud",
+		Path:      "cloud://cloud115/Movie.mkv",
+		Container: "strm",
+		STRMURL:   "/api/strm/play/cloud115/video.mkv?acct=missing&pickcode=pc1",
+	}).Error; err != nil {
+		t.Fatal(err)
+	}
+
+	embyPrewarmInFlight.Delete("media-1")
+	out := map[string]any{"MediaSources": []map[string]any{{"Id": "media-1"}}}
+
+	done := make(chan struct{})
+	go func() {
+		embyPrewarmPlaybackTargets(svc, newPrewarmTestContext(), out)
+		close(done)
+	}()
+	select {
+	case <-done:
+	case <-time.After(2 * time.Second):
+		t.Fatal("embyPrewarmPlaybackTargets blocked the caller")
+	}
+
+	// 后台协程应很快跑完并释放去重标记，否则同一条目后续再也预热不了。
+	deadline := time.Now().Add(3 * time.Second)
+	for time.Now().Before(deadline) {
+		if _, busy := embyPrewarmInFlight.Load("media-1"); !busy {
+			return
+		}
+		time.Sleep(10 * time.Millisecond)
+	}
+	t.Fatal("prewarm in-flight marker leaked")
+}
+
+// 各种缺数据的情况都不允许 panic 或阻塞：预热只是尽力而为的优化。
+func TestEmbyPrewarmPlaybackTargetsIsNilSafe(t *testing.T) {
+	svc := newPrewarmTestContainer(t)
+	c := newPrewarmTestContext()
+	out := map[string]any{"MediaSources": []map[string]any{{"Id": "media-1"}}}
+
+	cases := []struct {
+		name string
+		svc  *service.Container
+		out  map[string]any
+	}{
+		{name: "空容器", svc: &service.Container{}, out: out},
+		{name: "无 Strm", svc: &service.Container{Repo: svc.Repo}, out: out},
+		{name: "无 Repo", svc: &service.Container{Strm: svc.Strm}, out: out},
+		{name: "nil 载荷", svc: svc, out: nil},
+		{name: "无 MediaSources", svc: svc, out: map[string]any{}},
+		{name: "条目不存在", svc: svc, out: out},
+	}
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			embyPrewarmPlaybackTargets(tc.svc, c, tc.out)
+		})
+	}
+}
+
+// 本地文件条目不该触发换链预热（没有云盘直链可预热）。
+func TestEmbyPrewarmSkipsLocalMedia(t *testing.T) {
+	svc := newPrewarmTestContainer(t)
+	if err := svc.Repo.DB.Create(&model.Media{
+		Base:      model.Base{ID: "local-1"},
+		Title:     "Local",
+		Path:      "/media/movies/Local.mkv",
+		LibraryID: "lib-1",
+	}).Error; err != nil {
+		t.Fatal(err)
+	}
+
+	embyPrewarmInFlight.Delete("local-1")
+	embyPrewarmPlaybackTargets(svc, newPrewarmTestContext(),
+		map[string]any{"MediaSources": []map[string]any{{"Id": "local-1"}}})
+
+	// 协程要么已经跑完（标记被清掉），要么根本没起；两种都不该留下标记。
+	deadline := time.Now().Add(2 * time.Second)
+	for time.Now().Before(deadline) {
+		if _, busy := embyPrewarmInFlight.Load("local-1"); !busy {
+			return
+		}
+		time.Sleep(10 * time.Millisecond)
+	}
+	t.Fatal("local media must not leave a prewarm marker")
+}
diff --git a/internal/service/emby_discovery.go b/internal/service/emby_discovery.go
index 8e7e43e..296e232 100644
--- a/internal/service/emby_discovery.go
+++ b/internal/service/emby_discovery.go
@@ -5,6 +5,7 @@ import (
 	"crypto/sha1"
 	"encoding/hex"
 	"strings"
+	"time"
 )
 
 // Emby 发现类接口：NextUp / Similar / Genres。
@@ -67,6 +68,19 @@ func (e *EmbyService) SimilarItems(ctx context.Context, mediaID, userID string,
 		return emptyItemsEnvelope(0), nil
 	}
 
+	// 详情页每次打开都会请求相似推荐，而重建要走「取候选池 + 内存打分」
+	// （实测冷 340ms / 热 70ms）。推荐列表短暂陈旧无害，用短 TTL 缓存，
+	// 新建库或换用户都会因为键名不同而自然隔离。
+	cacheKey := e.embySimilarCacheKey(mediaID, userID, limit)
+	if e.cache != nil {
+		var cached map[string]any
+		if e.cache.GetJSON(ctx, cacheKey, &cached) && cached != nil {
+			if _, ok := cached["Items"]; ok {
+				return cached, nil
+			}
+		}
+	}
+
 	// Bug 2 fix: resolve virtual series IDs (msgo-series-*) and real series
 	// table IDs to a representative episode so SimilarCandidates (which calls
 	// Media.FindByID) can seed similarity from concrete media metadata.
@@ -109,12 +123,20 @@ func (e *EmbyService) SimilarItems(ctx context.Context, mediaID, userID string,
 	if err != nil {
 		return nil, err
 	}
-	return map[string]any{
+	out := map[string]any{
 		"Items":            items,
 		"TotalRecordCount": int64(len(items)),
-	}, nil
+	}
+	if e.cache != nil {
+		e.cache.SetJSON(ctx, cacheKey, out, embySimilarCacheTTL)
+	}
+	return out, nil
 }
 
+// embySimilarCacheTTL 是「相似推荐」结果的缓存时长。列表只是推荐，短暂陈旧
+// 无害；TTL 取短一些，让新入库的内容尽快出现。
+const embySimilarCacheTTL = 2 * time.Minute
+
 // Genres 返回类型清单。parentID 非空时（客户端按媒体库浏览类型）只统计该库。
 func (e *EmbyService) Genres(ctx context.Context, userID, parentID string) (map[string]any, error) {
 	discovery := e.discoveryService()
diff --git a/internal/service/emby_items_cache.go b/internal/service/emby_items_cache.go
index a31a030..83b5716 100644
--- a/internal/service/emby_items_cache.go
+++ b/internal/service/emby_items_cache.go
@@ -67,6 +67,15 @@ func (e *EmbyService) embyLatestCacheKey(userID, parentID string, limit int) str
 	return "media:emby:" + hex.EncodeToString(sum[:])
 }
 
+// embySimilarCacheKey 是「相似推荐」结果的缓存键。
+//
+// userID 必须参与键名：候选集的可见性（AllowedLibraryIDs、NSFW）由用户决定，
+// 混用会把别的用户可见的条目推荐给当前用户。limit 同理影响结果条数与排序。
+func (e *EmbyService) embySimilarCacheKey(mediaID, userID string, limit int) string {
+	sum := sha256.Sum256([]byte(strings.Join([]string{"similar-v1", mediaID, userID, strconv.Itoa(limit)}, "|")))
+	return "media:emby:" + hex.EncodeToString(sum[:])
+}
+
 // defaultEmbyLatestCacheTTLSeconds 是 Emby「最新添加」缓存的兜底时长。
 const defaultEmbyLatestCacheTTLSeconds = 300
 
diff --git a/internal/service/emby_remote.go b/internal/service/emby_remote.go
index 0916bbd..19ec3b2 100644
--- a/internal/service/emby_remote.go
+++ b/internal/service/emby_remote.go
@@ -86,6 +86,54 @@ type EmbyRemoteService struct {
 	// （没有它时 URL 恒定，缩略图会永久停留在旧版本）。
 	imageTagMu sync.RWMutex
 	imageTags  map[string]string
+
+	// remoteGate 是发往远程 Emby 的并发闸门。第三方客户端刷新首页时会为每个
+	// 远程媒体库各请求一次 /Items/Latest，挂着几十个库就是几十路并发（生产环境
+	// 实测 50 路同时打进来，单个请求被拖到 5s+）。限制在途请求数后单个请求的
+	// 等待时间反而下降，也不会把 2C 小机和对方服务器一起打满。
+	//
+	// nil 表示不限流（测试直接构造结构体时走这条路）。
+	remoteGate chan struct{}
+}
+
+// embyRemoteConcurrencyLimit 是同时发往远程 Emby 的请求数上限。
+const embyRemoteConcurrencyLimit = 8
+
+// enterRemoteGate 取得一个远程请求名额，返回释放函数。未配置闸门时返回空操作。
+func (r *EmbyRemoteService) enterRemoteGate(ctx context.Context) (func(), error) {
+	if r == nil || r.remoteGate == nil {
+		return func() {}, nil
+	}
+	select {
+	case r.remoteGate <- struct{}{}:
+		return func() { <-r.remoteGate }, nil
+	case <-ctx.Done():
+		return nil, ctx.Err()
+	}
+}
+
+// fetchRemoteBody 在并发闸门内发起请求并读完响应体，返回状态码与字节。
+func (r *EmbyRemoteService) fetchRemoteBody(ctx context.Context, req *http.Request, path string) (int, []byte, error) {
+	release, err := r.enterRemoteGate(ctx)
+	if err != nil {
+		return 0, nil, err
+	}
+	defer release()
+	resp, err := r.http.Do(req)
+	if err != nil {
+		return 0, nil, redactSensitiveError(fmt.Errorf("请求远程 Emby 失败: %w", err))
+	}
+	defer resp.Body.Close()
+	// 读 8MB+1 以区分"刚好 8MB"与"被截断"：截断的 JSON 会让
+	// Unmarshal 报 unexpected end，难以定位；这里显式报错。
+	data, readErr := io.ReadAll(io.LimitReader(resp.Body, (8<<20)+1))
+	if readErr != nil {
+		return resp.StatusCode, nil, readErr
+	}
+	if len(data) > 8<<20 {
+		return resp.StatusCode, data, fmt.Errorf("远程 Emby 响应超过 8MB 上限（路径 %s）：请减小分页或 Fields 字段", path)
+	}
+	return resp.StatusCode, data, nil
 }
 
 type embyRemotePersonImageRef struct {
@@ -113,6 +161,7 @@ func NewEmbyRemoteService(cfg *config.Config, log *zap.Logger, repo *repository.
 		stream: &http.Client{
 			Transport: &embyRemoteTransport{base: http.DefaultTransport},
 		},
+		remoteGate: make(chan struct{}, embyRemoteConcurrencyLimit),
 	}
 }
 
@@ -645,21 +694,11 @@ func (r *EmbyRemoteService) doGetOnLine(ctx context.Context, acct *model.StrmAcc
 			return err
 		}
 		req.Header.Set("X-Emby-Token", cfg.Token)
-		resp, err := r.http.Do(req)
+		status, data, err := r.fetchRemoteBody(ctx, req, path)
 		if err != nil {
-			return redactSensitiveError(fmt.Errorf("请求远程 Emby 失败: %w", err))
+			return err
 		}
-		// 读 8MB+1 以区分"刚好 8MB"与"被截断"：截断的 JSON 会让
-		// Unmarshal 报 unexpected end，难以定位；这里显式报错。
-		data, readErr := io.ReadAll(io.LimitReader(resp.Body, (8<<20)+1))
-		resp.Body.Close()
-		if readErr != nil {
-			return readErr
-		}
-		if len(data) > 8<<20 {
-			return fmt.Errorf("远程 Emby 响应超过 8MB 上限（路径 %s）：请减小分页或 Fields 字段", path)
-		}
-		if resp.StatusCode == http.StatusUnauthorized && attempt == 0 {
+		if status == http.StatusUnauthorized && attempt == 0 {
 			// 401：只清当前线路的内存 token 并立即重认证；不在此时删除
 			// DB 里的 api_key——①外层还会按线路故障转移（其他线路可能
 			// 存有自己的 token）；②纯 api_key 账号删除后无法再认证，一次
@@ -673,8 +712,8 @@ func (r *EmbyRemoteService) doGetOnLine(ctx context.Context, acct *model.StrmAcc
 			master.RemoteUserID = cfg.RemoteUserID
 			continue
 		}
-		if resp.StatusCode >= 300 {
-			return redactSensitiveError(fmt.Errorf("远程 Emby 请求失败(%d): %s", resp.StatusCode, strings.TrimSpace(string(data))))
+		if status >= 300 {
+			return redactSensitiveError(fmt.Errorf("远程 Emby 请求失败(%d): %s", status, strings.TrimSpace(string(data))))
 		}
 		if out == nil {
 			return nil
@@ -1617,6 +1656,12 @@ func (r *EmbyRemoteService) doMutateOnLine(ctx context.Context, cfg *EmbyRemoteC
 		return err
 	}
 	req.Header.Set("X-Emby-Token", cfg.Token)
+	// 状态同步同样走远程并发闸门：它和首页那批 Latest 请求共用对方服务器。
+	release, err := r.enterRemoteGate(ctx)
+	if err != nil {
+		return err
+	}
+	defer release()
 	resp, err := r.http.Do(req)
 	if err != nil {
 		return redactSensitiveError(fmt.Errorf("请求远程 Emby 失败: %w", err))
diff --git a/internal/service/emby_remote_gate_test.go b/internal/service/emby_remote_gate_test.go
new file mode 100644
index 0000000..50e213a
--- /dev/null
+++ b/internal/service/emby_remote_gate_test.go
@@ -0,0 +1,112 @@
+package service
+
+import (
+	"context"
+	"errors"
+	"net/http"
+	"net/http/httptest"
+	"sync"
+	"testing"
+	"time"
+
+	"go.uber.org/zap"
+
+	"github.com/truewhile/MeBox/internal/config"
+)
+
+// 远程 Emby 的并发闸门必须真的把在途请求数压在上限之内：第三方客户端首页会为
+// 每个远程媒体库各请求一次 /Items/Latest，几十个库就是几十路并发。
+func TestRemoteGateLimitsConcurrentRequests(t *testing.T) {
+	const gate = 3
+	const requests = 12
+
+	var mu sync.Mutex
+	inflight, peak := 0, 0
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
+		mu.Lock()
+		inflight++
+		if inflight > peak {
+			peak = inflight
+		}
+		mu.Unlock()
+
+		time.Sleep(20 * time.Millisecond)
+
+		mu.Lock()
+		inflight--
+		mu.Unlock()
+		_, _ = w.Write([]byte(`{"Items":[]}`))
+	}))
+	defer srv.Close()
+
+	svc := &EmbyRemoteService{http: srv.Client(), remoteGate: make(chan struct{}, gate)}
+
+	var wg sync.WaitGroup
+	for i := 0; i < requests; i++ {
+		wg.Add(1)
+		go func() {
+			defer wg.Done()
+			req, err := http.NewRequestWithContext(context.Background(), http.MethodGet, srv.URL+"/Items/Latest", nil)
+			if err != nil {
+				return
+			}
+			if _, _, err := svc.fetchRemoteBody(context.Background(), req, "/Items/Latest"); err != nil {
+				t.Errorf("fetchRemoteBody: %v", err)
+			}
+		}()
+	}
+	wg.Wait()
+
+	mu.Lock()
+	defer mu.Unlock()
+	if peak == 0 {
+		t.Fatal("test server never saw a request")
+	}
+	if peak > gate {
+		t.Fatalf("peak concurrency = %d, want <= %d", peak, gate)
+	}
+}
+
+// 闸门排队时要响应请求取消，不能把整个 HTTP 请求挂死。
+func TestRemoteGateHonoursContextCancellation(t *testing.T) {
+	svc := &EmbyRemoteService{remoteGate: make(chan struct{}, 1)}
+	svc.remoteGate <- struct{}{} // 占满名额
+
+	ctx, cancel := context.WithCancel(context.Background())
+	cancel()
+	if _, err := svc.enterRemoteGate(ctx); !errors.Is(err, context.Canceled) {
+		t.Fatalf("err = %v, want context.Canceled", err)
+	}
+
+	// 释放名额后必须能正常拿到。
+	<-svc.remoteGate
+	release, err := svc.enterRemoteGate(context.Background())
+	if err != nil {
+		t.Fatalf("enterRemoteGate after release: %v", err)
+	}
+	release()
+	if len(svc.remoteGate) != 0 {
+		t.Fatalf("gate leaked a permit: len = %d", len(svc.remoteGate))
+	}
+}
+
+// 未配置闸门（测试里直接构造结构体）时不应限流，保持旧行为。
+func TestRemoteGateAbsentIsUnlimited(t *testing.T) {
+	svc := &EmbyRemoteService{}
+	release, err := svc.enterRemoteGate(context.Background())
+	if err != nil {
+		t.Fatalf("enterRemoteGate: %v", err)
+	}
+	release()
+}
+
+// 生产路径构造出来的服务必须带闸门，否则上面的限制形同虚设。
+func TestNewEmbyRemoteServiceInitialisesGate(t *testing.T) {
+	svc := NewEmbyRemoteService(&config.Config{}, zap.NewNop(), nil, nil)
+	if svc.remoteGate == nil {
+		t.Fatal("remoteGate must be initialised by the constructor")
+	}
+	if cap(svc.remoteGate) != embyRemoteConcurrencyLimit {
+		t.Fatalf("gate capacity = %d, want %d", cap(svc.remoteGate), embyRemoteConcurrencyLimit)
+	}
+}
diff --git a/internal/service/emby_similar_cache_test.go b/internal/service/emby_similar_cache_test.go
new file mode 100644
index 0000000..c3f6961
--- /dev/null
+++ b/internal/service/emby_similar_cache_test.go
@@ -0,0 +1,118 @@
+package service
+
+import (
+	"context"
+	"testing"
+
+	"go.uber.org/zap"
+
+	"github.com/truewhile/MeBox/internal/config"
+	"github.com/truewhile/MeBox/internal/model"
+)
+
+// totalRecordCount 兼容两种来源：直算出来的是 int64，经过进程内缓存 JSON
+// 往返后是 float64。两者序列化成 Emby 响应时完全一致。
+func totalRecordCount(t *testing.T, out map[string]any) int {
+	t.Helper()
+	switch v := out["TotalRecordCount"].(type) {
+	case int64:
+		return int(v)
+	case int:
+		return v
+	case float64:
+		return int(v)
+	default:
+		t.Fatalf("unexpected TotalRecordCount type %T (%v)", out["TotalRecordCount"], out["TotalRecordCount"])
+		return 0
+	}
+}
+
+// 相似推荐的结果要缓存：详情页每次打开都会请求它，重建要走「取候选池 + 内存打分」
+// （实测冷 340ms / 热 70ms）。
+func TestSimilarItemsServesCachedPayload(t *testing.T) {
+	svc := newTestEmbyService(t)
+	repos := svc.repo
+	svc.SetRuntimeCache(NewRuntimeCacheService(&config.Config{}, zap.NewNop()))
+
+	libID := seedDiscoveryLibrary(t, repos, "movie")
+	source := seedSimilarMedia(t, repos, libID, "源片", "Action", 2010, 7)
+	seedSimilarMedia(t, repos, libID, "候选甲", "Action", 2010, 7)
+	seedSimilarMedia(t, repos, libID, "候选乙", "Comedy", 2011, 6)
+
+	ctx := context.Background()
+	first, err := svc.SimilarItems(ctx, source.ID, "user-1", 10)
+	if err != nil {
+		t.Fatalf("first SimilarItems: %v", err)
+	}
+	want := totalRecordCount(t, first)
+	if want == 0 {
+		t.Fatalf("first call returned no candidates, test data is wrong: %+v", first)
+	}
+
+	// 把候选全部删掉：第二次如果还返回原结果，只可能是命中缓存。
+	if err := repos.DB.Where("id <> ?", source.ID).Delete(&model.Media{}).Error; err != nil {
+		t.Fatal(err)
+	}
+
+	second, err := svc.SimilarItems(ctx, source.ID, "user-1", 10)
+	if err != nil {
+		t.Fatalf("second SimilarItems: %v", err)
+	}
+	if got := totalRecordCount(t, second); got != want {
+		t.Fatalf("cached call returned %d items, want %d (cache miss?)", got, want)
+	}
+
+	// 另一个用户（不同的可见性）不能复用别人的缓存：这里应当重新查询并得到 0。
+	other, err := svc.SimilarItems(ctx, source.ID, "user-2", 10)
+	if err != nil {
+		t.Fatalf("other user SimilarItems: %v", err)
+	}
+	if got := totalRecordCount(t, other); got != 0 {
+		t.Fatalf("other user got %d items, want 0 (per-user cache key)", got)
+	}
+}
+
+// limit 不同必须分开缓存，否则一次小 limit 请求会污染后续更大的请求。
+func TestSimilarItemsCacheSeparatesLimit(t *testing.T) {
+	svc := newTestEmbyService(t)
+	repos := svc.repo
+	svc.SetRuntimeCache(NewRuntimeCacheService(&config.Config{}, zap.NewNop()))
+
+	libID := seedDiscoveryLibrary(t, repos, "movie")
+	source := seedSimilarMedia(t, repos, libID, "源片", "Action", 2010, 7)
+	for _, title := range []string{"甲", "乙", "丙", "丁"} {
+		seedSimilarMedia(t, repos, libID, "候选"+title, "Action", 2010, 7)
+	}
+
+	ctx := context.Background()
+	small, err := svc.SimilarItems(ctx, source.ID, "user-1", 2)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if got := totalRecordCount(t, small); got != 2 {
+		t.Fatalf("limit=2 returned %d items, want 2", got)
+	}
+	large, err := svc.SimilarItems(ctx, source.ID, "user-1", 4)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if got := totalRecordCount(t, large); got != 4 {
+		t.Fatalf("limit=4 returned %d items, want 4 (limit must be part of the cache key)", got)
+	}
+}
+
+// 没有注入缓存时（测试/精简部署）也必须正常工作。
+func TestSimilarItemsWithoutCacheStillWorks(t *testing.T) {
+	svc := newTestEmbyService(t)
+	libID := seedDiscoveryLibrary(t, svc.repo, "movie")
+	source := seedSimilarMedia(t, svc.repo, libID, "源片", "Action", 2010, 7)
+	seedSimilarMedia(t, svc.repo, libID, "候选甲", "Action", 2010, 7)
+
+	out, err := svc.SimilarItems(context.Background(), source.ID, "user-1", 10)
+	if err != nil {
+		t.Fatalf("SimilarItems: %v", err)
+	}
+	if got := totalRecordCount(t, out); got == 0 {
+		t.Fatalf("expected candidates without a cache, got %+v", out)
+	}
+}
diff --git a/internal/service/service_builder.go b/internal/service/service_builder.go
index 901fa3e..ef2d96c 100644
--- a/internal/service/service_builder.go
+++ b/internal/service/service_builder.go
@@ -145,6 +145,9 @@ func (b *serviceContainerBuilder) initContentServices() {
 	b.c.Transcoder.SetStrmPlayTargetResolver(b.c.Strm.ResolvePlayTarget)
 	b.c.Transcoder.SetProbe(b.c.FFprobe)
 	b.c.Subtitle.SetStrmPlayTargetResolver(b.c.Strm.ResolvePlayTarget)
+	// 播放链路：/Videos/{id}/stream 与 /api/stream/{id} 在服务端完成换链后直接
+	// 302 到最终直链，客户端少跟随一次 302（高延迟线路上省一个往返）。
+	b.c.Stream.SetStrmPlayTargetResolver(b.c.Strm.ResolvePlayTargetWithUA)
 	// 弹幕识别需要把远程 Emby 条目解析为 Media 元数据及可拉取前 16MB 的直链 URL。
 	if b.c.EmbyRemote != nil {
 		b.c.Danmaku.SetRemoteMediaResolver(func(ctx context.Context, encodedID string) (*model.Media, string, error) {
diff --git a/internal/service/stream_direct_redirect_test.go b/internal/service/stream_direct_redirect_test.go
new file mode 100644
index 0000000..c1fefd2
--- /dev/null
+++ b/internal/service/stream_direct_redirect_test.go
@@ -0,0 +1,200 @@
+package service
+
+import (
+	"context"
+	"errors"
+	"net/http"
+	"net/http/httptest"
+	"net/url"
+	"strings"
+	"testing"
+
+	"go.uber.org/zap"
+
+	"github.com/truewhile/MeBox/internal/config"
+	"github.com/truewhile/MeBox/internal/model"
+	"github.com/truewhile/MeBox/internal/repository"
+	"github.com/truewhile/MeBox/internal/service/cloud"
+)
+
+// directRedirectTestRepo 建一个带网盘账号表的库：normalizeCloudPlayTarget 需要
+// StrmAccount 才能判断 strm 目标是不是本机账号生成的。
+func directRedirectTestRepo(t *testing.T) *repository.Container {
+	t.Helper()
+	return repository.New(newServiceTestDB(t, &model.Media{}, &model.Setting{}, &model.StrmAccount{}))
+}
+
+func seedCloudSTRMMedia(t *testing.T, repos *repository.Container, id, strmURL string) {
+	t.Helper()
+	if err := repos.DB.Create(&model.Media{
+		Base:      model.Base{ID: id},
+		Title:     "Cloud",
+		Path:      "cloud://cloud115/Movie.mkv",
+		Container: "strm",
+		STRMURL:   strmURL,
+	}).Error; err != nil {
+		t.Fatal(err)
+	}
+}
+
+// 服务端能换到最终直链时必须直接 302 过去：客户端原本要跟着
+// /Videos/{id}/stream → /api/strm/play 两次 302，现在缩成一跳。
+func TestServeFileRedirectsStraightToResolvedDirectURL(t *testing.T) {
+	repos := directRedirectTestRepo(t)
+	seedCloudSTRMMedia(t, repos, "cloud-direct", "/api/strm/play/cloud115/video.mkv?acct=a1&pickcode=pc1")
+	direct := "https://cdnfhnfile.115cdn.net/637b/Movie.mkv?t=1&k=sig"
+
+	var gotRaw, gotUA string
+	svc := NewStreamService(&config.Config{}, zap.NewNop(), repos, nil).
+		SetStrmPlayTargetResolver(func(_ context.Context, raw, userAgent string) (*StrmPlayResult, error) {
+			gotRaw, gotUA = raw, userAgent
+			// 生产环境 115 直链就是这样返回的：绑定 UA、Proxy=false。
+			return &StrmPlayResult{
+				RedirectURL: direct,
+				Link:        &cloud.DirectLink{URL: direct, Headers: map[string]string{"User-Agent": userAgent}},
+			}, nil
+		})
+
+	req := httptest.NewRequest(http.MethodGet, "http://nas.local:18080/api/stream/cloud-direct?token=jwt123", nil)
+	req.Header.Set("User-Agent", "RodelPlayer/2.2607.7.0")
+	w := httptest.NewRecorder()
+
+	if err := svc.ServeFile(w, req, "cloud-direct"); err != nil {
+		t.Fatalf("ServeFile: %v", err)
+	}
+	if w.Code != http.StatusFound {
+		t.Fatalf("status = %d, want 302", w.Code)
+	}
+	loc := w.Header().Get("Location")
+	if loc != direct {
+		t.Fatalf("Location = %q, want the resolved direct link %q", loc, direct)
+	}
+	if strings.Contains(loc, "jwt123") || strings.Contains(loc, "media_id=") {
+		t.Fatalf("internal auth query must not leak to the CDN link: %q", loc)
+	}
+	if got := w.Header().Get("Cache-Control"); !strings.Contains(got, "no-store") {
+		t.Fatalf("direct redirect must stay uncacheable, got %q", got)
+	}
+	// 换链必须带播放器 UA（115 直链绑定换取时的 UA，且按 UA 分键缓存）。
+	if gotUA != "RodelPlayer/2.2607.7.0" {
+		t.Fatalf("resolver UA = %q, want the player UA", gotUA)
+	}
+	if !strings.Contains(gotRaw, "pickcode=pc1") {
+		t.Fatalf("resolver raw = %q, want the strm target", gotRaw)
+	}
+}
+
+// 只要拿不到「客户端自己能直接拉取的直链」，就必须回退到改动前的 strm 端点跳转，
+// 保证行为不会比改动前更差。
+func TestServeFileFallsBackWhenDirectResolveUnavailable(t *testing.T) {
+	strmURL := "/api/strm/play/cloud115/video.mkv?acct=a1&pickcode=pc1"
+	cases := []struct {
+		name    string
+		result  *StrmPlayResult
+		wantErr error
+	}{
+		{name: "换链失败", wantErr: errors.New("115 换链失败")},
+		{
+			name: "需要服务端反向代理",
+			result: &StrmPlayResult{
+				Proxy: true,
+				Link:  &cloud.DirectLink{URL: "https://cdn.example/x", Headers: map[string]string{"Authorization": "Basic x"}},
+			},
+		},
+		{name: "没有直链（别的 MeBox 实例）", result: &StrmPlayResult{RedirectURL: "https://other.example/api/strm/play/cloud115/video.mkv?acct=o&pickcode=p"}},
+		{name: "解析到本地文件", result: &StrmPlayResult{LocalPath: "/media/Movie.mkv"}},
+		{name: "返回 nil", result: nil},
+		{
+			name: "链接要求额外请求头",
+			result: &StrmPlayResult{
+				RedirectURL: "https://cdn.example/x",
+				Link: &cloud.DirectLink{
+					URL:     "https://cdn.example/x",
+					Headers: map[string]string{"User-Agent": "ua", "Authorization": "Bearer t"},
+				},
+			},
+		},
+	}
+
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			repos := directRedirectTestRepo(t)
+			seedCloudSTRMMedia(t, repos, "cloud-fallback", strmURL)
+			svc := NewStreamService(&config.Config{}, zap.NewNop(), repos, nil).
+				SetStrmPlayTargetResolver(func(context.Context, string, string) (*StrmPlayResult, error) {
+					return tc.result, tc.wantErr
+				})
+
+			req := httptest.NewRequest(http.MethodGet, "http://nas.local:18080/api/stream/cloud-fallback?token=jwt123", nil)
+			w := httptest.NewRecorder()
+
+			if err := svc.ServeFile(w, req, "cloud-fallback"); err != nil {
+				t.Fatalf("ServeFile: %v", err)
+			}
+			if w.Code != http.StatusFound {
+				t.Fatalf("status = %d, want 302", w.Code)
+			}
+			loc := w.Header().Get("Location")
+			if !strings.Contains(loc, "/api/strm/play/cloud115/video.mkv") {
+				t.Fatalf("Location = %q, want the strm endpoint fallback", loc)
+			}
+			if strings.Contains(loc, "cdn.example") || strings.Contains(loc, "other.example") {
+				t.Fatalf("Location = %q, must not point at an unusable direct link", loc)
+			}
+		})
+	}
+}
+
+// 没有注入解析器（测试/精简部署）时保持原有跳转，不受本次优化影响。
+func TestServeFileKeepsSTRMEndpointWithoutResolver(t *testing.T) {
+	repos := directRedirectTestRepo(t)
+	seedCloudSTRMMedia(t, repos, "cloud-plain", "/api/strm/play/cloud115/video.mkv?acct=a1&pickcode=pc1")
+	svc := NewStreamService(&config.Config{}, zap.NewNop(), repos, nil)
+
+	req := httptest.NewRequest(http.MethodGet, "http://nas.local:18080/api/stream/cloud-plain?token=jwt123", nil)
+	w := httptest.NewRecorder()
+	if err := svc.ServeFile(w, req, "cloud-plain"); err != nil {
+		t.Fatalf("ServeFile: %v", err)
+	}
+	if loc := w.Header().Get("Location"); !strings.Contains(loc, "/api/strm/play/cloud115/video.mkv") {
+		t.Fatalf("Location = %q, want the strm endpoint", loc)
+	}
+}
+
+// playbackQueryWithUA 负责把播放器 UA 透传给换链方，同时不能改动原 URL。
+func TestPlaybackQueryWithUAInjectsUserAgent(t *testing.T) {
+	u, err := url.Parse("/api/strm/play/cloud115/video.mkv?acct=a1&pickcode=pc1")
+	if err != nil {
+		t.Fatal(err)
+	}
+	q := playbackQueryWithUA(u, "  RodelPlayer/2.2607.7.0  ")
+	if got := q.Get("__ua"); got != "RodelPlayer/2.2607.7.0" {
+		t.Fatalf("__ua = %q, want the trimmed player UA", got)
+	}
+	if q.Get("pickcode") != "pc1" || q.Get("acct") != "a1" {
+		t.Fatalf("original query lost: %v", q)
+	}
+	if strings.Contains(u.RawQuery, "__ua") {
+		t.Fatalf("source URL must not be mutated: %q", u.RawQuery)
+	}
+	if got := playbackQueryWithUA(u, "   ").Get("__ua"); got != "" {
+		t.Fatalf("blank UA must not be injected, got %q", got)
+	}
+	if got := playbackQueryWithUA(nil, "ua").Get("__ua"); got != "ua" {
+		t.Fatalf("nil URL must still accept the UA, got %q", got)
+	}
+}
+
+// ResolvePlayTargetWithUA 是 ResolvePlayTarget 的 UA 版本：空 UA 时行为必须与
+// 原方法完全一致（外部直链透传）。
+func TestResolvePlayTargetWithUAKeepsPassthroughBehaviour(t *testing.T) {
+	svc := &StrmService{}
+	raw := "https://cdn.example.test/Movie.mkv?sign=1"
+	got, err := svc.ResolvePlayTargetWithUA(context.Background(), raw, "RodelPlayer/1.0")
+	if err != nil {
+		t.Fatalf("ResolvePlayTargetWithUA: %v", err)
+	}
+	if got == nil || got.RedirectURL != raw {
+		t.Fatalf("result = %+v, want passthrough of %q", got, raw)
+	}
+}
diff --git a/internal/service/stream_file.go b/internal/service/stream_file.go
index ba53cde..570c904 100644
--- a/internal/service/stream_file.go
+++ b/internal/service/stream_file.go
@@ -6,6 +6,7 @@ import (
 	"net/url"
 	"os"
 	"strings"
+	"time"
 
 	"github.com/truewhile/MeBox/internal/model"
 	"github.com/truewhile/MeBox/internal/repository"
@@ -33,6 +34,14 @@ func (s *StreamService) ServeFileWithCloudMode(w http.ResponseWriter, r *http.Re
 		if !cloudPlaybackModeEnabled(r.Context(), s.repo, cloudMode) {
 			return ErrCloudPlaybackDisabled
 		}
+		// 能在服务端换到最终直链就直接 302 过去：客户端少跟随一次 302，等于
+		// 省掉一次「DNS+TCP+TLS+请求」的往返。解析结果同时写进 strm 层直链
+		// 缓存，后续 /api/strm/play 请求直接命中。
+		if direct, ok := s.resolveDirectPlayTargetURL(r, strmURL); ok {
+			setCloudRedirectNoStore(w)
+			http.Redirect(w, r, direct, http.StatusFound)
+			return nil
+		}
 		// 云盘播放 URL 先规范化为相对路径，免疫扫描时固化的旧 host；
 		// 指向别的 MeBox 实例的地址保持原样，按第三方直链透传。
 		target := normalizeCloudPlayTarget(r.Context(), s.repo, s.cfg, r, strmURL)
@@ -72,6 +81,43 @@ func setCloudRedirectNoStore(w http.ResponseWriter) {
 	w.Header().Set("Expires", "0")
 }
 
+// directPlayResolveTimeout 是服务端换链的等待上限。115 开放平台在跨太平洋线路
+// 上单次换链实测 0.4–1.1s，这里给足余量；一旦超时就回退到原来的 strm 端点跳转，
+// 由 /api/strm/play 再去换链，最坏情况只是回到改动前的行为。
+const directPlayResolveTimeout = 10 * time.Second
+
+// resolveDirectPlayTargetURL 尝试在服务端把 strm 目标解析成客户端可直接拉取的
+// 最终直链，供调用方直接 302。
+//
+// 只在「明确的直链」上短路：需要服务端反向代理（云盘 WebDAV 等必须附加请求头）、
+// 解析到本地文件、以及解析失败都会返回 false，由调用方按改动前的方式回退到
+// strm 端点跳转，行为不会变差。
+func (s *StreamService) resolveDirectPlayTargetURL(r *http.Request, raw string) (string, bool) {
+	if s == nil || s.strmResolve == nil || r == nil {
+		return "", false
+	}
+	ctx, cancel := context.WithTimeout(r.Context(), directPlayResolveTimeout)
+	defer cancel()
+	// 必须带播放器 UA：115 直链绑定换取时的 UA，且按 UA 分键缓存，换错会拿到
+	// 与播放器不匹配（或未命中缓存）的地址。
+	result, err := s.strmResolve(ctx, raw, r.Header.Get("User-Agent"))
+	if err != nil || result == nil || result.Proxy || result.Link == nil {
+		return "", false
+	}
+	// 客户端只能自带 User-Agent 这类基础请求头。链接一旦要求其它头（Referer /
+	// Authorization），就必须继续由服务端反向代理，不能在这里短路。
+	for name := range result.Link.Headers {
+		if !strings.EqualFold(strings.TrimSpace(name), "User-Agent") {
+			return "", false
+		}
+	}
+	direct := strings.TrimSpace(result.RedirectURL)
+	if direct == "" {
+		return "", false
+	}
+	return direct, true
+}
+
 func isCloudPlaybackTarget(raw string) bool {
 	_, _, ok := parseCloudMediaPlaybackURL(raw)
 	return ok
diff --git a/internal/service/stream_service.go b/internal/service/stream_service.go
index e44d6ea..1a927c9 100644
--- a/internal/service/stream_service.go
+++ b/internal/service/stream_service.go
@@ -33,6 +33,10 @@ type StreamService struct {
 	log        *zap.Logger
 	repo       *repository.Container
 	transcoder *TranscoderService
+	// strmResolve 把 strm 目标解析成最终直链。注入后 /Videos/{id}/stream 能直接
+	// 302 到 CDN 地址，省掉 /api/strm/play 那一跳；未注入时保持原有的两跳行为，
+	// 因此测试与精简部署不受影响。
+	strmResolve func(ctx context.Context, raw, userAgent string) (*StrmPlayResult, error)
 }
 
 // NewStreamService is the constructor.
@@ -45,6 +49,16 @@ func NewStreamService(cfg *config.Config, log *zap.Logger, repo *repository.Cont
 	}
 }
 
+// SetStrmPlayTargetResolver 注入 strm 播放目标解析器（通常为
+// StrmService.ResolvePlayTargetWithUA）。注入后播放链路会在服务端完成换链并直接
+// 302 到最终直链，避免客户端在高延迟线路上多跟随一次 302。
+func (s *StreamService) SetStrmPlayTargetResolver(resolve func(ctx context.Context, raw, userAgent string) (*StrmPlayResult, error)) *StreamService {
+	if s != nil {
+		s.strmResolve = resolve
+	}
+	return s
+}
+
 // ErrMediaNotFound is returned when the media row or its file is missing.
 var ErrMediaNotFound = errors.New("media not found")
 
diff --git a/internal/service/strm_play.go b/internal/service/strm_play.go
index 7df1d3d..2b3952e 100644
--- a/internal/service/strm_play.go
+++ b/internal/service/strm_play.go
@@ -124,6 +124,16 @@ func (s *StrmService) resolveLocalPlay(ctx context.Context, rawPath string) (*St
 //   - 绝对 http(s) 链接（直接透传，包含别的 MeBox / MediaStationGo 实例的播放端点）
 //   - 其余协议（webdav:// 等）返回错误，由调用方决定是否静默跳过
 func (s *StrmService) ResolvePlayTarget(ctx context.Context, raw string) (*StrmPlayResult, error) {
+	return s.ResolvePlayTargetWithUA(ctx, raw, "")
+}
+
+// ResolvePlayTargetWithUA 与 ResolvePlayTarget 相同，但会把调用方的 User-Agent
+// 透传给需要按 UA 换取直链的提供方（115 直链绑定换取时的 UA，换错会被 CDN 拒绝）。
+//
+// 用途：播放链路在服务端直接把 strm 目标解析成最终直链并 302（见
+// StreamService.resolveDirectPlayTargetURL），此时必须带上播放器的 UA，才能拿到
+// 与 /api/strm/play 端点一致的、按 UA 分键缓存的那条直链。
+func (s *StrmService) ResolvePlayTargetWithUA(ctx context.Context, raw, userAgent string) (*StrmPlayResult, error) {
 	raw = strings.TrimSpace(raw)
 	if raw == "" {
 		return nil, errors.New("空播放目标")
@@ -150,14 +160,14 @@ func (s *StrmService) ResolvePlayTarget(ctx context.Context, raw string) (*StrmP
 		if len(segs) < 1 || strings.TrimSpace(segs[0]) == "" {
 			return nil, errors.New("无效的 strm 播放地址")
 		}
-		return s.ResolvePlay(ctx, segs[0], u.Query())
+		return s.ResolvePlay(ctx, segs[0], playbackQueryWithUA(u, userAgent))
 	case strings.HasPrefix(lowerPath, "/api/cloud/play/"):
 		typ := strings.TrimSpace(strings.TrimPrefix(u.Path, "/api/cloud/play/"))
 		acct, err := s.firstEnabledAccountOf(ctx, typ)
 		if err != nil || acct == nil {
 			return nil, errors.New("没有可用的网盘账号，无法解析直链")
 		}
-		q := u.Query()
+		q := playbackQueryWithUA(u, userAgent)
 		q.Set("acct", acct.ID)
 		return s.ResolvePlay(ctx, typ, q)
 	case u.Scheme == "http" || u.Scheme == "https":
@@ -167,6 +177,19 @@ func (s *StrmService) ResolvePlayTarget(ctx context.Context, raw string) (*StrmP
 	}
 }
 
+// playbackQueryWithUA 复制播放目标的查询串并注入 __ua。ResolvePlay 的云盘提供方
+// 据此按播放器 UA 换取直链，与 /api/strm/play 端点写入 __ua 的语义保持一致。
+func playbackQueryWithUA(u *url.URL, userAgent string) url.Values {
+	q := url.Values{}
+	if u != nil {
+		q = url.Values(u.Query())
+	}
+	if ua := strings.TrimSpace(userAgent); ua != "" {
+		q.Set("__ua", ua)
+	}
+	return q
+}
+
 // isLocalPlaybackTarget 报告播放地址是否属于本机。这里没有 HTTP 请求上下文，
 // 「本机」由 strm.base_url / 各同步目录覆盖的 base_url / 本机网盘账号共同界定
 // （见 isInternalPlaybackTarget）。