diff --git a/server/cmd/latencyprobe/main.go b/server/cmd/latencyprobe/main.go
new file mode 100644
index 0000000..9922fc8
--- /dev/null
+++ b/server/cmd/latencyprobe/main.go
@@ -0,0 +1,267 @@
+// latencyprobe：12B 延迟验收工具——走本地网关全链路（WS 网关 → gummy）实测延迟分布。
+//
+// 复刻桌面客户端行为：单条持久 WS 连接，串行多次会话，音频实时推流（100ms/帧）。
+//
+// 测量口径对齐桌面端 dictation.rs：
+//
+//	first_partial_ms     = start 帧发出 → 本会话首个 partial 收到
+//	                       （桌面端另含麦克风启动耗时 audio.start_ms，此处不含）
+//	release_to_commit_ms = stop 帧发出 → 本会话尾部 final 收到（文本完整落定）
+//	                       （桌面端另含文字注入耗时，通常 <10ms，此处不含；
+//	                        若 stop 后先到 usage 帧，桌面端会提前以 partial 文本注入，
+//	                        该情形单独计数为 usage_first）
+//
+// 用法（服务端需已以 gummy provider 启动）：
+//
+//	go run ./cmd/latencyprobe -wav /path/to/16k-mono-16bit.wav -n 12
+package main
+
+import (
+	"encoding/binary"
+	"encoding/json"
+	"flag"
+	"fmt"
+	"net/http"
+	"os"
+	"sort"
+	"time"
+
+	"github.com/gorilla/websocket"
+
+	"dudu/server/internal/auth"
+	"dudu/server/internal/store"
+	"dudu/server/pkg/protocol"
+)
+
+type event struct {
+	msg protocol.ServerMsg
+	at  time.Time
+}
+
+func main() {
+	addr := flag.String("addr", "localhost:8080", "服务端地址")
+	wavPath := flag.String("wav", "", "16kHz/16bit/mono wav 文件路径")
+	n := flag.Int("n", 12, "会话次数（注意 30 分钟滑动窗口上限 30 次/设备）")
+	dsn := flag.String("dsn", "host=localhost user=dudu password=dudu dbname=dudu port=5432 sslmode=disable TimeZone=Asia/Shanghai", "postgres dsn（用于确保探针用户存在且余额充足）")
+	secret := flag.String("secret", "dev-secret-change-me", "JWT secret（须与服务端一致）")
+	userID := flag.String("user", "latency-probe", "探针用户 ID")
+	deviceID := flag.String("device", "probe-dev", "探针设备 ID")
+	flag.Parse()
+	if *wavPath == "" {
+		fmt.Fprintln(os.Stderr, "用法: latencyprobe -wav test.wav [-n 12]")
+		os.Exit(2)
+	}
+
+	pcm, err := readWavData(*wavPath)
+	if err != nil {
+		fmt.Fprintln(os.Stderr, "读 wav 失败:", err)
+		os.Exit(1)
+	}
+	audioSec := float64(len(pcm)) / float64(protocol.SampleRate*2)
+	fmt.Printf("音频 %.1fs · %d 次会话 · 单连接串行 · 实时推流（100ms/帧）\n", audioSec, *n)
+
+	// 确保探针用户存在且余额充足（试用 180s/天 不够跑长测）。
+	db, err := store.Open(*dsn)
+	if err != nil {
+		fmt.Fprintln(os.Stderr, "postgres 连接失败:", err)
+		os.Exit(1)
+	}
+	var u store.User
+	db.Where(store.User{ID: *userID}).FirstOrCreate(&u)
+	if err := db.Model(&store.User{}).Where("id = ?", *userID).Update("balance_seconds", 360000).Error; err != nil {
+		fmt.Fprintln(os.Stderr, "更新探针用户余额失败:", err)
+		os.Exit(1)
+	}
+
+	token, err := auth.NewJWT(*secret, time.Hour, nil).Sign(*userID)
+	if err != nil {
+		fmt.Fprintln(os.Stderr, "签发 JWT 失败:", err)
+		os.Exit(1)
+	}
+
+	// 单条持久连接（桌面端同款）：会话串行复用，读循环常驻。
+	url := fmt.Sprintf("ws://%s/v1/asr/stream?device_id=%s", *addr, *deviceID)
+	hdr := http.Header{"Authorization": {"Bearer " + token}}
+	conn, _, err := websocket.DefaultDialer.Dial(url, hdr)
+	if err != nil {
+		fmt.Fprintln(os.Stderr, "dial 失败:", err)
+		os.Exit(1)
+	}
+	defer conn.Close()
+	events := make(chan event, 256)
+	go func() {
+		defer close(events)
+		for {
+			var msg protocol.ServerMsg
+			if err := conn.ReadJSON(&msg); err != nil {
+				return
+			}
+			events <- event{msg, time.Now()}
+		}
+	}()
+
+	var firstPartials, releaseToCommits []time.Duration
+	usageFirst := 0
+	for i := 0; i < *n; i++ {
+		sid := fmt.Sprintf("probe-%d-%d", time.Now().UnixNano(), i)
+		r, err := runSession(conn, events, sid, pcm)
+		if err != nil {
+			fmt.Printf("  #%02d 失败: %v\n", i+1, err)
+		} else {
+			firstPartials = append(firstPartials, r.firstPartial)
+			releaseToCommits = append(releaseToCommits, r.releaseToCommit)
+			note := ""
+			if r.usageBeforeFinal {
+				usageFirst++
+				note = "  ⚠️usage先到"
+			}
+			fmt.Printf("  #%02d first_partial=%5dms  release_to_commit=%4dms  %q%s\n",
+				i+1, r.firstPartial.Milliseconds(), r.releaseToCommit.Milliseconds(), truncate(r.text, 24), note)
+		}
+		time.Sleep(800 * time.Millisecond) // 会话间隔（无论成败），模拟自然停顿
+	}
+
+	if len(firstPartials) == 0 {
+		fmt.Fprintln(os.Stderr, "无有效样本")
+		os.Exit(1)
+	}
+	fmt.Println()
+	report("first_partial     ", firstPartials, 500*time.Millisecond)
+	report("release_to_commit ", releaseToCommits, 300*time.Millisecond)
+	if usageFirst > 0 {
+		fmt.Printf("⚠️ %d/%d 次会话 stop 后 usage 帧先于尾部 final 到达（桌面端将以 partial 文本提前注入，丢失 final 修正）\n",
+			usageFirst, len(firstPartials))
+	}
+}
+
+type sessionResult struct {
+	firstPartial     time.Duration
+	releaseToCommit  time.Duration
+	text             string
+	usageBeforeFinal bool
+}
+
+// runSession 在共享连接上执行一次会话：start → 实时推流 → stop → 等尾部 final。
+// 事件按 session_id 过滤，前一会话的迟到帧不串扰。
+func runSession(conn *websocket.Conn, events <-chan event, sid string, pcm []byte) (r sessionResult, err error) {
+	start, _ := json.Marshal(protocol.ClientMsg{Type: protocol.MsgStart, SessionID: sid, SampleRate: protocol.SampleRate, Format: "pcm16"})
+	t0 := time.Now()
+	if err := conn.WriteMessage(websocket.TextMessage, start); err != nil {
+		return r, fmt.Errorf("start: %w", err)
+	}
+
+	handle := func(ev event, tStop *time.Time) error {
+		if ev.msg.SessionID != sid {
+			return nil // 旧会话迟到帧
+		}
+		switch ev.msg.Type {
+		case protocol.MsgPartial:
+			if r.firstPartial == 0 {
+				r.firstPartial = ev.at.Sub(t0)
+			}
+		case protocol.MsgFinal:
+			r.text += ev.msg.Text
+			if tStop != nil && r.releaseToCommit == 0 {
+				r.releaseToCommit = ev.at.Sub(*tStop)
+			}
+		case protocol.MsgUsage:
+			if tStop != nil && r.releaseToCommit == 0 {
+				r.usageBeforeFinal = true // 桌面端此刻已提前注入 partial 文本
+			}
+		case protocol.MsgError:
+			return fmt.Errorf("server error: %s %s", ev.msg.Code, ev.msg.Message)
+		}
+		return nil
+	}
+
+	// 实时推流 + 并行收包。
+	ticker := time.NewTicker(protocol.FrameMillis * time.Millisecond)
+	defer ticker.Stop()
+	off := 0
+	for off < len(pcm) {
+		select {
+		case <-ticker.C:
+			end := min(off+protocol.FrameBytes, len(pcm))
+			if err := conn.WriteMessage(websocket.BinaryMessage, pcm[off:end]); err != nil {
+				return r, fmt.Errorf("audio: %w", err)
+			}
+			off = end
+		case ev, ok := <-events:
+			if !ok {
+				return r, fmt.Errorf("连接已断开")
+			}
+			if err := handle(ev, nil); err != nil {
+				return r, err
+			}
+		}
+	}
+
+	stop, _ := json.Marshal(protocol.ClientMsg{Type: protocol.MsgStop, SessionID: sid})
+	tStop := time.Now()
+	if err := conn.WriteMessage(websocket.TextMessage, stop); err != nil {
+		return r, fmt.Errorf("stop: %w", err)
+	}
+
+	// 收尾：等尾部 final（文本完整落定），10s 兜底。
+	deadline := time.After(10 * time.Second)
+	for r.releaseToCommit == 0 {
+		select {
+		case ev, ok := <-events:
+			if !ok {
+				return r, fmt.Errorf("连接已断开")
+			}
+			if err := handle(ev, &tStop); err != nil {
+				return r, err
+			}
+		case <-deadline:
+			return r, fmt.Errorf("收尾超时：stop 后 10s 未收到尾部 final")
+		}
+	}
+	if r.firstPartial == 0 {
+		return r, fmt.Errorf("全程未收到 partial")
+	}
+	return r, nil
+}
+
+func report(name string, ds []time.Duration, target time.Duration) {
+	sorted := append([]time.Duration(nil), ds...)
+	sort.Slice(sorted, func(i, j int) bool { return sorted[i] < sorted[j] })
+	p50 := sorted[len(sorted)/2]
+	p95 := sorted[(len(sorted)*95+99)/100-1]
+	verdict := "✅ 达标"
+	if p95 > target {
+		verdict = "❌ 超标"
+	}
+	fmt.Printf("%s n=%d  P50=%dms  P95=%dms  min=%dms  max=%dms  目标P95<%dms  %s\n",
+		name, len(sorted), p50.Milliseconds(), p95.Milliseconds(),
+		sorted[0].Milliseconds(), sorted[len(sorted)-1].Milliseconds(), target.Milliseconds(), verdict)
+}
+
+func truncate(s string, n int) string {
+	r := []rune(s)
+	if len(r) <= n {
+		return s
+	}
+	return string(r[:n]) + "…"
+}
+
+// readWavData 提取 wav 的 data chunk（仅支持 PCM，同 gummycheck）。
+func readWavData(path string) ([]byte, error) {
+	b, err := os.ReadFile(path)
+	if err != nil {
+		return nil, err
+	}
+	if len(b) < 44 || string(b[0:4]) != "RIFF" || string(b[8:12]) != "WAVE" {
+		return nil, fmt.Errorf("不是 wav 文件")
+	}
+	off := 12
+	for off+8 <= len(b) {
+		id := string(b[off : off+4])
+		size := int(binary.LittleEndian.Uint32(b[off+4 : off+8]))
+		if id == "data" {
+			return b[off+8 : min(off+8+size, len(b))], nil
+		}
+		off += 8 + size
+	}
+	return nil, fmt.Errorf("未找到 data chunk")
+}
diff --git a/server/internal/asr/gummy.go b/server/internal/asr/gummy.go
index 5e9fdfb..2fb7cdc 100644
--- a/server/internal/asr/gummy.go
+++ b/server/internal/asr/gummy.go
@@ -8,6 +8,7 @@ import (
 	"context"
 	"encoding/json"
 	"fmt"
+	"log/slog"
 	"os"
 	"sync"
 	"time"
@@ -34,10 +35,12 @@ func (g *GummyProvider) StartSession(ctx context.Context, cfg SessionConfig) (Se
 		"Authorization": {"bearer " + g.APIKey},
 		"X-DashScope-DataInspection": {"enable"},
 	}
+	tDial := time.Now()
 	conn, _, err := websocket.DefaultDialer.DialContext(ctx, dashscopeWS, header)
 	if err != nil {
 		return nil, fmt.Errorf("dashscope dial: %w", err)
 	}
+	dialMs := time.Since(tDial).Milliseconds()
 
 	taskID := uuid.NewString()
 	runTask := map[string]any{
@@ -75,8 +78,13 @@ func (g *GummyProvider) StartSession(ctx context.Context, cfg SessionConfig) (Se
 	go s.readLoop()
 
 	// 协议要求：必须等 task-started 后才能推音频，否则服务端静默丢弃
+	tWait := time.Now()
 	select {
 	case <-s.started:
+		// 会话建立耗时是 first_partial 延迟的组成部分（12B）：dial 冷启（DNS+TLS）
+		// 可达 ~600ms、暖路径 ~60ms，task-started 通常 ~60ms。持续观测供延迟排查。
+		slog.Info("gummy: session ready", "task", taskID,
+			"dial_ms", dialMs, "task_started_wait_ms", time.Since(tWait).Milliseconds())
 		return s, nil
 	case <-s.done:
 		return nil, fmt.Errorf("dashscope: closed before task-started")
diff --git a/server/internal/gateway/gateway.go b/server/internal/gateway/gateway.go
index a56c540..3979941 100644
--- a/server/internal/gateway/gateway.go
+++ b/server/internal/gateway/gateway.go
@@ -137,6 +137,12 @@ func (h *Handler) HandleWS(c *gin.Context) {
 // startSession 执行 start 预检并建立 Provider 会话；失败时返回 nil（已下发 error 帧）。
 func (h *Handler) startSession(ctx context.Context, ws *wsConn, uid, deviceID string, msg protocol.ClientMsg) *session {
 	now := time.Now()
+	// start 处理耗时（预检 + provider 握手）串行阻塞在读循环里，直接叠加进客户端
+	// 可感知的 first_partial 延迟（12B），持续观测供延迟排查。
+	defer func() {
+		slog.Info("gateway: start handled", "session", msg.SessionID,
+			"total_ms", time.Since(now).Milliseconds())
+	}()
 
 	// ① 设备 30min 窗口：次数 + 累计时长
 	if ok, err := store.AllowSession(ctx, h.RDB, deviceID, now); err != nil || !ok {
diff --git a/server/internal/store/redis.go b/server/internal/store/redis.go
index cbb6d37..b362bb4 100644
--- a/server/internal/store/redis.go
+++ b/server/internal/store/redis.go
@@ -46,10 +46,14 @@ else
   end
 end
 if sum + val > limit then return 0 end
-local seq = redis.call('INCR', key .. ':seq')
-redis.call('EXPIRE', key .. ':seq', window + 60) -- 17C：seq 计数器与 ZSET 同寿命，避免按设备永久泄漏
-redis.call('ZADD', key, now, now .. '-' .. seq .. ':' .. val)
-redis.call('EXPIRE', key, window + 60)
+-- val=0 为"只查不记"（AudioWindowExhausted 的 start 预检）：不落 0 值成员，
+-- 避免污染窗口 ZSET 并空耗 seq；count 模式 val 恒为 1，不受影响。
+if val > 0 then
+  local seq = redis.call('INCR', key .. ':seq')
+  redis.call('EXPIRE', key .. ':seq', window + 60) -- 17C：seq 计数器与 ZSET 同寿命，避免按设备永久泄漏
+  redis.call('ZADD', key, now, now .. '-' .. seq .. ':' .. val)
+  redis.call('EXPIRE', key, window + 60)
+end
 return 1
 `)