feat: enhance desktop client presence management and add monitoring for active platforms

server/internal/tenant/app/desktop_presence.go

@@ -16,6 +16,11 @@ const desktopClientPresenceTTL = 30 * time.Second
 const desktopAccountPresenceTTL = 30 * time.Second
 const desktopTaskConsumerPresenceTTL = 75 * time.Second
 
+type desktopAccountPresenceClient struct {
+	ClientID             uuid.UUID
+	OnlineSinceUnixMilli int64
+}
+
 func desktopClientPresenceKey(clientID uuid.UUID) string {
 	return "desktop:presence:client:" + clientID.String()
 }
@@ -44,7 +49,13 @@ func markDesktopClientPresent(ctx context.Context, redis *goredis.Client, client
 		return
 	}
 
-	_ = redis.Set(ctx, desktopClientPresenceKey(clientID), time.Now().UTC().Format(time.RFC3339), desktopClientPresenceTTL).Err()
+	key := desktopClientPresenceKey(clientID)
+	now := strconv.FormatInt(time.Now().UTC().UnixMilli(), 10)
+	set, err := redis.SetNX(ctx, key, now, desktopClientPresenceTTL).Result()
+	if err != nil || set {
+		return
+	}
+	_ = redis.Expire(ctx, key, desktopClientPresenceTTL).Err()
 }
 
 func markDesktopTaskConsumerPresent(ctx context.Context, redis *goredis.Client, clientID uuid.UUID) {
@@ -198,8 +209,11 @@ func markDesktopAccountsPresent(ctx context.Context, redis *goredis.Client, clie
 		nextAccountSet[accountID] = struct{}{}
 	}
 
-	now := float64(time.Now().UTC().UnixMilli())
-	staleBefore := strconv.FormatInt(time.Now().UTC().Add(-desktopAccountPresenceTTL).UnixMilli(), 10)
+	now := time.Now().UTC()
+	onlineSinceUnixMilli := now.UnixMilli()
+	if value, err := redis.Get(ctx, desktopClientPresenceKey(clientID)).Result(); err == nil {
+		onlineSinceUnixMilli = parseDesktopPresenceUnixMilli(value, now)
+	}
 	clientAccountsKey := desktopClientAccountsPresenceKey(clientID)
 	clientMember := clientID.String()
 
@@ -222,9 +236,8 @@ func markDesktopAccountsPresent(ctx context.Context, redis *goredis.Client, clie
 	}
 	for _, accountID := range uniqueIDs {
 		key := desktopAccountPresenceKey(accountID)
-		pipe.ZRemRangeByScore(ctx, key, "-inf", staleBefore)
 		pipe.ZAdd(ctx, key, goredis.Z{
-			Score:  now,
+			Score:  float64(onlineSinceUnixMilli),
 			Member: clientMember,
 		})
 		pipe.Expire(ctx, key, desktopAccountPresenceTTL*4)
@@ -259,44 +272,145 @@ func clearDesktopClientPresenceState(ctx context.Context, redis *goredis.Client,
 }
 
 func loadDesktopAccountPresence(ctx context.Context, redis *goredis.Client, accountIDs []uuid.UUID) map[uuid.UUID]uuid.UUID {
+	clientsByAccount := loadDesktopAccountPresenceClients(ctx, redis, accountIDs)
+	if len(clientsByAccount) == 0 {
+		return nil
+	}
+
+	result := make(map[uuid.UUID]uuid.UUID, len(clientsByAccount))
+	for accountID, clients := range clientsByAccount {
+		if len(clients) == 0 {
+			continue
+		}
+		result[accountID] = clients[len(clients)-1].ClientID
+	}
+	return result
+}
+
+func loadDesktopAccountPresenceClients(ctx context.Context, redis *goredis.Client, accountIDs []uuid.UUID) map[uuid.UUID][]desktopAccountPresenceClient {
 	if redis == nil || len(accountIDs) == 0 {
 		return nil
 	}
 
 	uniqueIDs := uniqueUUIDs(accountIDs)
-	staleBefore := strconv.FormatInt(time.Now().UTC().Add(-desktopAccountPresenceTTL).UnixMilli(), 10)
 
 	pipe := redis.Pipeline()
 	commands := make(map[uuid.UUID]*goredis.ZSliceCmd, len(uniqueIDs))
 	for _, accountID := range uniqueIDs {
 		key := desktopAccountPresenceKey(accountID)
-		pipe.ZRemRangeByScore(ctx, key, "-inf", staleBefore)
-		commands[accountID] = pipe.ZRevRangeWithScores(ctx, key, 0, 0)
+		commands[accountID] = pipe.ZRangeWithScores(ctx, key, 0, -1)
 	}
 
 	if _, err := pipe.Exec(ctx); err != nil && err != goredis.Nil {
 		return nil
 	}
 
-	result := make(map[uuid.UUID]uuid.UUID, len(commands))
+	result := make(map[uuid.UUID][]desktopAccountPresenceClient, len(commands))
+	clientIDs := make([]uuid.UUID, 0)
+	staleMembersByAccount := make(map[uuid.UUID][]interface{})
 	for accountID, cmd := range commands {
 		values := cmd.Val()
 		if len(values) == 0 {
 			continue
 		}
-		clientIDText, ok := values[0].Member.(string)
-		if !ok || clientIDText == "" {
-			continue
+		seenClients := make(map[uuid.UUID]struct{}, len(values))
+		for _, value := range values {
+			clientIDText, ok := value.Member.(string)
+			if !ok || clientIDText == "" {
+				staleMembersByAccount[accountID] = append(staleMembersByAccount[accountID], value.Member)
+				continue
+			}
+			clientID, err := uuid.Parse(clientIDText)
+			if err != nil {
+				staleMembersByAccount[accountID] = append(staleMembersByAccount[accountID], clientIDText)
+				continue
+			}
+			if _, exists := seenClients[clientID]; exists {
+				continue
+			}
+			seenClients[clientID] = struct{}{}
+			result[accountID] = append(result[accountID], desktopAccountPresenceClient{
+				ClientID:             clientID,
+				OnlineSinceUnixMilli: int64(value.Score),
+			})
+			clientIDs = append(clientIDs, clientID)
 		}
-		clientID, err := uuid.Parse(clientIDText)
-		if err != nil {
-			continue
-		}
-		result[accountID] = clientID
 	}
+
+	clientIDs = uniqueUUIDs(clientIDs)
+	if len(clientIDs) == 0 {
+		pruneDesktopAccountPresenceMembers(ctx, redis, staleMembersByAccount)
+		cleanupDesktopAccountPresenceKeys(ctx, redis, uniqueIDs)
+		return nil
+	}
+
+	presencePipe := redis.Pipeline()
+	presenceCommands := make(map[uuid.UUID]*goredis.IntCmd, len(clientIDs))
+	for _, clientID := range clientIDs {
+		presenceCommands[clientID] = presencePipe.Exists(ctx, desktopClientPresenceKey(clientID))
+	}
+	if _, err := presencePipe.Exec(ctx); err != nil && err != goredis.Nil {
+		return nil
+	}
+
+	for accountID, clients := range result {
+		kept := clients[:0]
+		for _, client := range clients {
+			cmd := presenceCommands[client.ClientID]
+			if cmd != nil && cmd.Val() > 0 {
+				kept = append(kept, client)
+				continue
+			}
+			staleMembersByAccount[accountID] = append(staleMembersByAccount[accountID], client.ClientID.String())
+		}
+		if len(kept) == 0 {
+			delete(result, accountID)
+			continue
+		}
+		result[accountID] = kept
+	}
+
+	pruneDesktopAccountPresenceMembers(ctx, redis, staleMembersByAccount)
+	cleanupDesktopAccountPresenceKeys(ctx, redis, uniqueIDs)
 	return result
 }
 
+func parseDesktopPresenceUnixMilli(value string, fallback time.Time) int64 {
+	return parseDesktopPresenceTime(value, fallback).UnixMilli()
+}
+
+func parseDesktopPresenceTime(value string, fallback time.Time) time.Time {
+	if millis, err := strconv.ParseInt(value, 10, 64); err == nil && millis > 0 {
+		return time.UnixMilli(millis).UTC()
+	}
+	if parsed, err := time.Parse(time.RFC3339Nano, value); err == nil {
+		return parsed.UTC()
+	}
+	if parsed, err := time.Parse(time.RFC3339, value); err == nil {
+		return parsed.UTC()
+	}
+	return fallback.UTC()
+}
+
+func pruneDesktopAccountPresenceMembers(ctx context.Context, redis *goredis.Client, membersByAccount map[uuid.UUID][]interface{}) {
+	if redis == nil || len(membersByAccount) == 0 {
+		return
+	}
+
+	pipe := redis.Pipeline()
+	shouldExec := false
+	for accountID, members := range membersByAccount {
+		if len(members) == 0 {
+			continue
+		}
+		pipe.ZRem(ctx, desktopAccountPresenceKey(accountID), members...)
+		shouldExec = true
+	}
+	if shouldExec {
+		_, _ = pipe.Exec(ctx)
+	}
+}
+
 func uniqueUUIDs(values []uuid.UUID) []uuid.UUID {
 	if len(values) == 0 {
 		return nil

server/internal/tenant/app/desktop_presence_test.go

@@ -2,6 +2,7 @@ package app
 
 import (
 	"context"
+	"strconv"
 	"testing"
 	"time"
 
@@ -111,3 +112,59 @@ func TestDesktopTaskConsumerPresenceIsSeparateFromHeartbeatPresence(t *testing.T
 	require.NotNil(t, taskConsumerPresence)
 	assert.True(t, taskConsumerPresence[clientID])
 }
+
+func TestDesktopClientPresenceKeepsOriginalOnlineSinceAcrossHeartbeats(t *testing.T) {
+	ctx := context.Background()
+	server := miniredis.RunT(t)
+	redis := goredis.NewClient(&goredis.Options{Addr: server.Addr()})
+	t.Cleanup(func() {
+		require.NoError(t, redis.Close())
+	})
+
+	clientID := uuid.New()
+
+	markDesktopClientPresent(ctx, redis, clientID)
+	firstOnlineSince := redis.Get(ctx, desktopClientPresenceKey(clientID)).Val()
+	require.NotEmpty(t, firstOnlineSince)
+
+	time.Sleep(time.Millisecond)
+	markDesktopClientPresent(ctx, redis, clientID)
+	secondOnlineSince := redis.Get(ctx, desktopClientPresenceKey(clientID)).Val()
+
+	assert.Equal(t, firstOnlineSince, secondOnlineSince)
+	assert.Positive(t, redis.TTL(ctx, desktopClientPresenceKey(clientID)).Val())
+}
+
+func TestDesktopAccountPresenceClientsKeepLongRunningOnlineClientAndOrderByOnlineSince(t *testing.T) {
+	ctx := context.Background()
+	server := miniredis.RunT(t)
+	redis := goredis.NewClient(&goredis.Options{Addr: server.Addr()})
+	t.Cleanup(func() {
+		require.NoError(t, redis.Close())
+	})
+
+	accountID := uuid.New()
+	earlierClientID := uuid.New()
+	laterClientID := uuid.New()
+	offlineClientID := uuid.New()
+	now := time.Date(2026, 6, 19, 10, 0, 0, 0, time.UTC)
+	earlierOnlineSince := now.Add(-time.Hour).UnixMilli()
+	laterOnlineSince := now.UnixMilli()
+
+	require.NoError(t, redis.Set(ctx, desktopClientPresenceKey(earlierClientID), strconv.FormatInt(earlierOnlineSince, 10), desktopClientPresenceTTL).Err())
+	require.NoError(t, redis.Set(ctx, desktopClientPresenceKey(laterClientID), strconv.FormatInt(laterOnlineSince, 10), desktopClientPresenceTTL).Err())
+	require.NoError(t, redis.ZAdd(ctx, desktopAccountPresenceKey(accountID),
+		goredis.Z{Score: float64(laterOnlineSince), Member: laterClientID.String()},
+		goredis.Z{Score: float64(earlierOnlineSince), Member: earlierClientID.String()},
+		goredis.Z{Score: float64(now.Add(-2 * time.Hour).UnixMilli()), Member: offlineClientID.String()},
+	).Err())
+
+	clientsByAccount := loadDesktopAccountPresenceClients(ctx, redis, []uuid.UUID{accountID})
+
+	require.Len(t, clientsByAccount[accountID], 2)
+	assert.Equal(t, earlierClientID, clientsByAccount[accountID][0].ClientID)
+	assert.Equal(t, earlierOnlineSince, clientsByAccount[accountID][0].OnlineSinceUnixMilli)
+	assert.Equal(t, laterClientID, clientsByAccount[accountID][1].ClientID)
+	assert.Equal(t, laterOnlineSince, clientsByAccount[accountID][1].OnlineSinceUnixMilli)
+	assert.False(t, redis.ZScore(ctx, desktopAccountPresenceKey(accountID), offlineClientID.String()).Val() > 0)
+}

server/internal/tenant/app/monitoring_daily_task_worker.go

@@ -31,6 +31,7 @@ const (
 	defaultMonitoringDailyMaxMaterializePerRun   = 64
 	defaultMonitoringDailyMaxMaterializePerPlan  = 12
 	defaultMonitoringDailyMaxMaterializePerBrand = 4
+	monitoringDailyPlatformActiveWindow          = 24 * time.Hour
 	monitoringDailyMaterializeStartOffset        = 5 * time.Minute
 )
 
@@ -501,6 +502,13 @@ func (s *MonitoringService) generateDailyMonitoringTasksForBrand(
 	if dispatchLimit <= 0 {
 		return createdCount, dueCount, 0, 0, nil
 	}
+	dispatchablePlatformIDs, err := s.loadDailyMonitorDispatchablePlatformIDs(ctx, plan.TenantID, plan.WorkspaceID, candidates)
+	if err != nil {
+		return createdCount, dueCount, 0, 0, err
+	}
+	if len(dispatchablePlatformIDs) == 0 {
+		return createdCount, dueCount, 0, 0, nil
+	}
 	specs, err := s.loadDueDailyMonitorDesktopTaskSpecs(
 		ctx,
 		s.monitoringPool,
@@ -510,6 +518,7 @@ func (s *MonitoringService) generateDailyMonitoringTasksForBrand(
 		businessDay,
 		now.Add(defaultMonitoringDailyLookahead),
 		now.Add(-defaultMonitoringDailyDesktopRetryCooldown),
+		dispatchablePlatformIDs,
 		dispatchLimit,
 	)
 	if err != nil {
@@ -606,6 +615,8 @@ func (s *MonitoringService) loadDailyMonitoringPrimaryClientPlans(
 			   AND p.status = 'active'
 			   AND p.deleted_at IS NULL
 			WHERE dc.revoked_at IS NULL
+			  AND dc.last_seen_at IS NOT NULL
+			  AND dc.last_seen_at >= NOW() - $5::interval
 			  AND EXISTS (
 				SELECT 1
 				FROM platform_accounts pa
@@ -650,7 +661,7 @@ func (s *MonitoringService) loadDailyMonitoringPrimaryClientPlans(
 			$3::int AS max_questions_per_brand
 		FROM selected_clients c
 		ORDER BY c.tenant_id ASC, c.workspace_id ASC
-	`, freeBrandLimit, paidBrandLimit, questionLimit, supportedPlatforms)
+	`, freeBrandLimit, paidBrandLimit, questionLimit, supportedPlatforms, formatPgInterval(monitoringDailyPlatformActiveWindow))
 	if err != nil {
 		appErr := response.ErrInternal(50041, "query_failed", "failed to load daily monitoring plans")
 		appErr.Cause = err
@@ -716,27 +727,32 @@ func (s *MonitoringService) loadDailyMonitoringPlanPlatformJSON(
 			) AS input(tenant_id, workspace_id, client_id)
 		)
 		SELECT
-			p.tenant_id,
-			p.workspace_id,
-			p.client_id,
+			sc.tenant_id,
+			sc.workspace_id,
+			sc.client_id,
 			jsonb_agg(p.platform_id ORDER BY p.platform_id) AS enabled_platforms
-		FROM (
+		FROM selected_clients sc
+		JOIN (
 			SELECT DISTINCT
-				sc.tenant_id,
-				sc.workspace_id,
-				sc.client_id,
+				dc.tenant_id,
+				dc.workspace_id,
 				pa.platform_id
-			FROM selected_clients sc
+			FROM desktop_clients dc
 			JOIN platform_accounts pa
-				ON pa.tenant_id = sc.tenant_id
-			   AND pa.workspace_id = sc.workspace_id
-			   AND pa.client_id = sc.client_id
+				ON pa.tenant_id = dc.tenant_id
+			   AND pa.workspace_id = dc.workspace_id
+			   AND pa.client_id = dc.id
 			WHERE pa.deleted_at IS NULL
 			  AND pa.platform_id = ANY($4::text[])
+			  AND dc.revoked_at IS NULL
+			  AND dc.last_seen_at IS NOT NULL
+			  AND dc.last_seen_at >= NOW() - $5::interval
 		) p
-		GROUP BY p.tenant_id, p.workspace_id, p.client_id
-		ORDER BY p.tenant_id ASC, p.workspace_id ASC, p.client_id ASC
-	`, tenantIDs, workspaceIDs, clientIDs, supportedPlatforms)
+		  ON p.tenant_id = sc.tenant_id
+		 AND p.workspace_id = sc.workspace_id
+		GROUP BY sc.tenant_id, sc.workspace_id, sc.client_id
+		ORDER BY sc.tenant_id ASC, sc.workspace_id ASC, sc.client_id ASC
+	`, tenantIDs, workspaceIDs, clientIDs, supportedPlatforms, formatPgInterval(monitoringDailyPlatformActiveWindow))
 	if err != nil {
 		appErr := response.ErrInternal(50041, "query_failed", "failed to load daily monitoring plan platforms")
 		appErr.Cause = err
@@ -888,6 +904,46 @@ func (s *MonitoringService) countDailyMonitoringMaterializedTasks(ctx context.Co
 	return count, nil
 }
 
+func (s *MonitoringService) loadDailyMonitorDispatchablePlatformIDs(
+	ctx context.Context,
+	tenantID, workspaceID int64,
+	candidates []monitoringDailyTaskCandidate,
+) ([]string, error) {
+	if len(candidates) == 0 {
+		return nil, nil
+	}
+	specs := make([]monitorDesktopTaskSpec, 0, len(candidates))
+	for _, candidate := range candidates {
+		platformID := normalizeMonitoringPlatformID(candidate.Platform.ID)
+		if platformID == "" {
+			continue
+		}
+		specs = append(specs, monitorDesktopTaskSpec{
+			TenantID:     tenantID,
+			WorkspaceID:  workspaceID,
+			PlatformID:   platformID,
+			QuestionID:   candidate.Question.ID,
+			QuestionText: candidate.Question.QuestionText,
+		})
+	}
+	if len(specs) == 0 {
+		return nil, nil
+	}
+
+	targets, err := s.loadMonitorDesktopTaskTargets(ctx, tenantID, workspaceID, 0, specs)
+	if err != nil {
+		return nil, err
+	}
+	if len(targets) == 0 {
+		return nil, nil
+	}
+	platformIDs := make([]string, 0, len(targets))
+	for platformID := range targets {
+		platformIDs = append(platformIDs, platformID)
+	}
+	return reconcileEnabledMonitoringPlatforms(platformIDs), nil
+}
+
 func (s *MonitoringService) ensureDailyMonitoringCollectTasks(
 	ctx context.Context,
 	tx pgx.Tx,
@@ -984,11 +1040,16 @@ func (s *MonitoringService) loadDueDailyMonitorDesktopTaskSpecs(
 	businessDate time.Time,
 	cutoff time.Time,
 	retryBefore time.Time,
+	platformIDs []string,
 	limit int,
 ) ([]monitorDesktopTaskSpec, error) {
 	if q == nil || limit <= 0 {
 		return nil, nil
 	}
+	platformIDs = reconcileEnabledMonitoringPlatforms(platformIDs)
+	if len(platformIDs) == 0 {
+		return nil, nil
+	}
 
 	rows, err := q.Query(ctx, `
 		WITH candidate_tasks AS (
@@ -1003,10 +1064,11 @@ func (s *MonitoringService) loadDueDailyMonitorDesktopTaskSpecs(
 			  AND t.trigger_source = 'automatic'
 			  AND t.run_mode = 'desktop_standard'
 			  AND COALESCE(t.execution_owner, 'legacy') = 'desktop_tasks'
+			  AND t.ai_platform_id = ANY($7::text[])
 			  AND (t.dispatch_after IS NULL OR t.dispatch_after <= $5)
 			  AND (t.last_dispatched_at IS NULL OR t.last_dispatched_at <= $6)
 			ORDER BY t.dispatch_after ASC NULLS FIRST, t.dispatch_priority DESC, t.id ASC
-			LIMIT $7
+			LIMIT $8
 			FOR UPDATE SKIP LOCKED
 		),
 		claimed_tasks AS (
@@ -1043,7 +1105,7 @@ func (s *MonitoringService) loadDueDailyMonitorDesktopTaskSpecs(
 			), '') AS question_text_snapshot
 			FROM claimed_tasks t
 			ORDER BY t.dispatch_after ASC NULLS FIRST, t.dispatch_priority DESC, t.id ASC
-	`, tenantID, brandID, monitoringCollectorType, monitoringBusinessDateText(businessDate), cutoff.UTC(), retryBefore.UTC(), limit)
+	`, tenantID, brandID, monitoringCollectorType, monitoringBusinessDateText(businessDate), cutoff.UTC(), retryBefore.UTC(), platformIDs, limit)
 	if err != nil {
 		return nil, response.ErrInternal(50041, "query_failed", "failed to load due daily monitor desktop task specs")
 	}

server/internal/tenant/app/monitoring_daily_task_worker_test.go

@@ -10,6 +10,8 @@ import (
 	"time"
 
 	"github.com/google/uuid"
+	"github.com/jackc/pgx/v5"
+	"github.com/jackc/pgx/v5/pgconn"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 
@@ -329,9 +331,87 @@ func TestMonitoringSchedulerMetricsPrometheusHandlerIncludesRuntimeAndProcessCol
 	assert.True(t, strings.HasPrefix(recorder.Header().Get("Content-Type"), "text/plain"))
 }
 
+func TestLoadDueDailyMonitorDesktopTaskSpecsFiltersToDispatchablePlatforms(t *testing.T) {
+	ctx := context.Background()
+	queryer := &captureDailyMonitorTaskQueryer{}
+	businessDay := time.Date(2026, 6, 19, 0, 0, 0, 0, time.UTC)
+
+	specs, err := (&MonitoringService{}).loadDueDailyMonitorDesktopTaskSpecs(
+		ctx,
+		queryer,
+		4,
+		8,
+		2,
+		businessDay,
+		businessDay.Add(time.Hour),
+		businessDay.Add(-time.Hour),
+		[]string{"qwen", "unknown", "doubao"},
+		7,
+	)
+
+	require.NoError(t, err)
+	assert.Empty(t, specs)
+	assert.True(t, queryer.called)
+	assert.Contains(t, normalizeSQLWhitespace(queryer.sql), "AND t.ai_platform_id = ANY($7::text[])")
+	assert.Contains(t, normalizeSQLWhitespace(queryer.sql), "LIMIT $8")
+	require.Len(t, queryer.args, 8)
+	assert.Equal(t, int64(4), queryer.args[0])
+	assert.Equal(t, int64(2), queryer.args[1])
+	assert.Equal(t, []string{"doubao", "qwen"}, queryer.args[6])
+	assert.Equal(t, 7, queryer.args[7])
+}
+
+func TestLoadDueDailyMonitorDesktopTaskSpecsSkipsWithoutDispatchablePlatforms(t *testing.T) {
+	ctx := context.Background()
+	queryer := &captureDailyMonitorTaskQueryer{}
+	businessDay := time.Date(2026, 6, 19, 0, 0, 0, 0, time.UTC)
+
+	specs, err := (&MonitoringService{}).loadDueDailyMonitorDesktopTaskSpecs(
+		ctx,
+		queryer,
+		4,
+		8,
+		2,
+		businessDay,
+		businessDay.Add(time.Hour),
+		businessDay.Add(-time.Hour),
+		[]string{"unknown"},
+		7,
+	)
+
+	require.NoError(t, err)
+	assert.Empty(t, specs)
+	assert.False(t, queryer.called)
+}
+
 func mustParseDailyMonitoringUUID(t *testing.T, value string) uuid.UUID {
 	t.Helper()
 	id, err := uuid.Parse(value)
 	require.NoError(t, err)
 	return id
 }
+
+type captureDailyMonitorTaskQueryer struct {
+	called bool
+	sql    string
+	args   []any
+}
+
+func (q *captureDailyMonitorTaskQueryer) Query(_ context.Context, sql string, args ...any) (pgx.Rows, error) {
+	q.called = true
+	q.sql = sql
+	q.args = args
+	return emptyDailyMonitorRows{}, nil
+}
+
+type emptyDailyMonitorRows struct{}
+
+func (r emptyDailyMonitorRows) Close()                                       {}
+func (r emptyDailyMonitorRows) Err() error                                   { return nil }
+func (r emptyDailyMonitorRows) CommandTag() pgconn.CommandTag                { return pgconn.CommandTag{} }
+func (r emptyDailyMonitorRows) FieldDescriptions() []pgconn.FieldDescription { return nil }
+func (r emptyDailyMonitorRows) Next() bool                                   { return false }
+func (r emptyDailyMonitorRows) Scan(...any) error                            { return nil }
+func (r emptyDailyMonitorRows) Values() ([]any, error)                       { return nil, nil }
+func (r emptyDailyMonitorRows) RawValues() [][]byte                          { return nil }
+func (r emptyDailyMonitorRows) Conn() *pgx.Conn                              { return nil }

server/internal/tenant/app/monitoring_phase2_desktop_tasks.go

@@ -56,6 +56,16 @@ type monitorDesktopTaskTarget struct {
 	ClientID  uuid.UUID
 }
 
+type monitorDesktopTaskTargetCandidate struct {
+	Target               monitorDesktopTaskTarget
+	HealthRank           int
+	OnlineRank           int
+	SourceRank           int
+	OnlineSinceUnixMilli int64
+	RecordOrder          int
+	ClientOrder          int
+}
+
 type monitorDesktopInterruptTarget struct {
 	TaskID              string
 	MonitorTaskID       int64
@@ -334,7 +344,7 @@ func (s *MonitoringService) loadMonitorDesktopTaskTargets(
 	}
 
 	accountIDs := monitorDesktopAccountCandidateAccountIDs(candidates)
-	accountPresence := loadDesktopAccountPresence(ctx, s.redis, accountIDs)
+	accountPresence := loadDesktopAccountPresenceClients(ctx, s.redis, accountIDs)
 	clientIDs := monitorDesktopAccountCandidateClientIDs(candidates, accountPresence)
 	onlineClients, err := s.loadOnlineMonitorDesktopClients(ctx, workspaceID, clientIDs)
 	if err != nil {
@@ -373,15 +383,17 @@ func monitorDesktopAccountCandidateAccountIDs(candidates []monitorDesktopAccount
 	return uniqueUUIDs(result)
 }
 
-func monitorDesktopAccountCandidateClientIDs(candidates []monitorDesktopAccountCandidate, accountPresence map[uuid.UUID]uuid.UUID) []uuid.UUID {
+func monitorDesktopAccountCandidateClientIDs(candidates []monitorDesktopAccountCandidate, accountPresence map[uuid.UUID][]desktopAccountPresenceClient) []uuid.UUID {
 	result := make([]uuid.UUID, 0, len(candidates)*2)
 	for _, candidate := range candidates {
 		if candidate.DBClientID != nil && *candidate.DBClientID != uuid.Nil {
 			result = append(result, *candidate.DBClientID)
 		}
 		if accountPresence != nil {
-			if clientID, ok := accountPresence[candidate.AccountID]; ok && clientID != uuid.Nil {
-				result = append(result, clientID)
+			for _, client := range accountPresence[candidate.AccountID] {
+				if client.ClientID != uuid.Nil {
+					result = append(result, client.ClientID)
+				}
 			}
 		}
 	}
@@ -430,35 +442,95 @@ func (s *MonitoringService) loadOnlineMonitorDesktopClients(ctx context.Context,
 
 func selectMonitorDesktopTaskTargets(
 	candidates []monitorDesktopAccountCandidate,
-	accountPresence map[uuid.UUID]uuid.UUID,
+	accountPresence map[uuid.UUID][]desktopAccountPresenceClient,
 	onlineClients map[uuid.UUID]bool,
 ) map[string]monitorDesktopTaskTarget {
 	result := make(map[string]monitorDesktopTaskTarget)
-	targetsByPlatform := make(map[string][]monitorDesktopTaskTarget)
+	bestByPlatform := make(map[string]monitorDesktopTaskTargetCandidate)
 	for _, candidate := range candidates {
 		platformID := normalizeMonitoringPlatformID(candidate.PlatformID)
 		if platformID == "" || candidate.AccountID == uuid.Nil {
 			continue
 		}
 
-		if clientID, ok := accountPresence[candidate.AccountID]; ok && clientID != uuid.Nil && onlineClients[clientID] {
-			targetsByPlatform[platformID] = append(targetsByPlatform[platformID], monitorDesktopTaskTarget{AccountID: candidate.AccountID, ClientID: clientID})
+		seenClientIDs := make(map[uuid.UUID]struct{})
+		if accountPresence != nil {
+			for index, client := range accountPresence[candidate.AccountID] {
+				if client.ClientID == uuid.Nil || !onlineClients[client.ClientID] {
+					continue
+				}
+				seenClientIDs[client.ClientID] = struct{}{}
+				item := monitorDesktopTaskTargetCandidate{
+					Target: monitorDesktopTaskTarget{
+						AccountID: candidate.AccountID,
+						ClientID:  client.ClientID,
+					},
+					HealthRank:           candidate.HealthRank,
+					OnlineRank:           0,
+					SourceRank:           0,
+					OnlineSinceUnixMilli: client.OnlineSinceUnixMilli,
+					RecordOrder:          candidate.RecordOrder,
+					ClientOrder:          index,
+				}
+				if current, ok := bestByPlatform[platformID]; !ok || item.betterThan(current) {
+					bestByPlatform[platformID] = item
+				}
+			}
+		}
+		if candidate.DBClientID == nil || *candidate.DBClientID == uuid.Nil || !onlineClients[*candidate.DBClientID] {
 			continue
 		}
-		if candidate.DBClientID != nil && *candidate.DBClientID != uuid.Nil && onlineClients[*candidate.DBClientID] {
-			targetsByPlatform[platformID] = append(targetsByPlatform[platformID], monitorDesktopTaskTarget{AccountID: candidate.AccountID, ClientID: *candidate.DBClientID})
+		if _, exists := seenClientIDs[*candidate.DBClientID]; exists {
+			continue
+		}
+		item := monitorDesktopTaskTargetCandidate{
+			Target: monitorDesktopTaskTarget{
+				AccountID: candidate.AccountID,
+				ClientID:  *candidate.DBClientID,
+			},
+			HealthRank:  candidate.HealthRank,
+			OnlineRank:  0,
+			SourceRank:  1,
+			RecordOrder: candidate.RecordOrder,
+		}
+		if current, ok := bestByPlatform[platformID]; !ok || item.betterThan(current) {
+			bestByPlatform[platformID] = item
 		}
 	}
-	for platformID, targets := range targetsByPlatform {
-		if len(targets) == 0 {
-			continue
-		}
-		index := randomIndex(len(targets))
-		result[platformID] = targets[index]
+	for platformID, candidate := range bestByPlatform {
+		result[platformID] = candidate.Target
 	}
 	return result
 }
 
+func (candidate monitorDesktopTaskTargetCandidate) betterThan(current monitorDesktopTaskTargetCandidate) bool {
+	if candidate.HealthRank != current.HealthRank {
+		return candidate.HealthRank < current.HealthRank
+	}
+	if candidate.SourceRank != current.SourceRank {
+		return candidate.SourceRank < current.SourceRank
+	}
+	if candidate.OnlineSinceUnixMilli != current.OnlineSinceUnixMilli {
+		if candidate.OnlineSinceUnixMilli == 0 {
+			return false
+		}
+		if current.OnlineSinceUnixMilli == 0 {
+			return true
+		}
+		return candidate.OnlineSinceUnixMilli < current.OnlineSinceUnixMilli
+	}
+	if candidate.OnlineRank != current.OnlineRank {
+		return candidate.OnlineRank < current.OnlineRank
+	}
+	if candidate.RecordOrder != current.RecordOrder {
+		return candidate.RecordOrder < current.RecordOrder
+	}
+	if candidate.ClientOrder != current.ClientOrder {
+		return candidate.ClientOrder < current.ClientOrder
+	}
+	return candidate.Target.ClientID.String() < current.Target.ClientID.String()
+}
+
 func (s *MonitoringService) upsertMonitorDesktopTask(
 	ctx context.Context,
 	tx pgx.Tx,

server/internal/tenant/app/monitoring_phase2_desktop_tasks_test.go

@@ -20,8 +20,10 @@ func TestSelectMonitorDesktopTaskTargetsPrefersPresentAccountClient(t *testing.T
 				DBClientID: &staleClientID,
 			},
 		},
-		map[uuid.UUID]uuid.UUID{
-			accountID: liveClientID,
+		map[uuid.UUID][]desktopAccountPresenceClient{
+			accountID: {
+				{ClientID: liveClientID, OnlineSinceUnixMilli: 100},
+			},
 		},
 		map[uuid.UUID]bool{
 			liveClientID: true,
@@ -77,30 +79,71 @@ func TestSelectMonitorDesktopTaskTargetsSkipsOfflineClients(t *testing.T) {
 	assert.Empty(t, targets)
 }
 
-func TestSelectMonitorDesktopTaskTargetsRandomizesAmongOnlineCandidates(t *testing.T) {
-	clientIDs := []uuid.UUID{
-		mustParseDailyMonitoringUUID(t, "00000000-0000-0000-0000-000000000301"),
-		mustParseDailyMonitoringUUID(t, "00000000-0000-0000-0000-000000000302"),
-	}
-	accountIDs := []uuid.UUID{
-		mustParseDailyMonitoringUUID(t, "00000000-0000-0000-0000-000000000401"),
-		mustParseDailyMonitoringUUID(t, "00000000-0000-0000-0000-000000000402"),
-	}
+func TestSelectMonitorDesktopTaskTargetsPrefersHealthierOnlineCandidate(t *testing.T) {
+	riskClientID := mustParseDailyMonitoringUUID(t, "00000000-0000-0000-0000-000000000301")
+	liveClientID := mustParseDailyMonitoringUUID(t, "00000000-0000-0000-0000-000000000302")
+	riskAccountID := mustParseDailyMonitoringUUID(t, "00000000-0000-0000-0000-000000000401")
+	liveAccountID := mustParseDailyMonitoringUUID(t, "00000000-0000-0000-0000-000000000402")
 
-	for i := 0; i < 40; i++ {
-		targets := selectMonitorDesktopTaskTargets(
-			[]monitorDesktopAccountCandidate{
-				{PlatformID: "qwen", AccountID: accountIDs[0], DBClientID: &clientIDs[0]},
-				{PlatformID: "qwen", AccountID: accountIDs[1], DBClientID: &clientIDs[1]},
+	targets := selectMonitorDesktopTaskTargets(
+		[]monitorDesktopAccountCandidate{
+			{
+				PlatformID:  "qwen",
+				AccountID:   riskAccountID,
+				DBClientID:  &riskClientID,
+				HealthRank:  1,
+				RecordOrder: 0,
 			},
-			nil,
-			map[uuid.UUID]bool{
-				clientIDs[0]: true,
-				clientIDs[1]: true,
+			{
+				PlatformID:  "qwen",
+				AccountID:   liveAccountID,
+				DBClientID:  &liveClientID,
+				HealthRank:  0,
+				RecordOrder: 1,
 			},
-		)
-		target := targets["qwen"]
-		assert.Contains(t, clientIDs, target.ClientID)
-		assert.Contains(t, accountIDs, target.AccountID)
-	}
+		},
+		nil,
+		map[uuid.UUID]bool{
+			riskClientID: true,
+			liveClientID: true,
+		},
+	)
+
+	assert.Equal(t, monitorDesktopTaskTarget{
+		AccountID: liveAccountID,
+		ClientID:  liveClientID,
+	}, targets["qwen"])
+}
+
+func TestSelectMonitorDesktopTaskTargetsPrefersEarlierOnlineClientForSameAccount(t *testing.T) {
+	accountID := mustParseDailyMonitoringUUID(t, "00000000-0000-0000-0000-000000000501")
+	earlierClientID := mustParseDailyMonitoringUUID(t, "00000000-0000-0000-0000-000000000601")
+	laterClientID := mustParseDailyMonitoringUUID(t, "00000000-0000-0000-0000-000000000602")
+
+	targets := selectMonitorDesktopTaskTargets(
+		[]monitorDesktopAccountCandidate{
+			{
+				PlatformID:  "doubao",
+				AccountID:   accountID,
+				DBClientID:  &laterClientID,
+				HealthRank:  0,
+				RecordOrder: 0,
+			},
+		},
+		map[uuid.UUID][]desktopAccountPresenceClient{
+			accountID: {
+				{ClientID: laterClientID, OnlineSinceUnixMilli: 200},
+				{ClientID: earlierClientID, OnlineSinceUnixMilli: 100},
+			},
+		},
+		map[uuid.UUID]bool{
+			earlierClientID: true,
+			laterClientID:   true,
+		},
+	)
+
+	assert.Equal(t, monitorDesktopTaskTarget{
+		AccountID: accountID,
+		ClientID:  earlierClientID,
+	}, targets["doubao"])
 }