diff --git a/backend/internal/handler/admin/grok_import_probe.go b/backend/internal/handler/admin/grok_import_probe.go
index 9ef4ce8cd0..da547b82f8 100644
--- a/backend/internal/handler/admin/grok_import_probe.go
+++ b/backend/internal/handler/admin/grok_import_probe.go
@@ -13,6 +13,7 @@ import (
 const (
 	grokImportProbeConcurrency = 3
 	grokImportProbeTimeout     = 25 * time.Second
+	grokImportProbeQueueLimit  = 64
 )
 
 type grokImportProber interface {
@@ -27,6 +28,8 @@ type grokImportProbeTask struct {
 type grokImportProbeScheduler struct {
 	mu          sync.Mutex
 	queue       []grokImportProbeTask
+	pending     map[int64]struct{}
+	inFlight    map[int64]struct{}
 	concurrency int
 	workers     int
 	maxWorkers  int
@@ -48,6 +51,8 @@ func newGrokImportProbeScheduler(concurrency int, timeout time.Duration) *grokIm
 	return &grokImportProbeScheduler{
 		concurrency: concurrency,
 		timeout:     timeout,
+		pending:     make(map[int64]struct{}),
+		inFlight:    make(map[int64]struct{}),
 	}
 }
 
@@ -60,7 +65,21 @@ func (s *grokImportProbeScheduler) schedule(prober grokImportProber, account *se
 	}
 
 	s.mu.Lock()
+	if _, exists := s.pending[account.ID]; exists {
+		s.mu.Unlock()
+		return
+	}
+	if _, exists := s.inFlight[account.ID]; exists {
+		s.mu.Unlock()
+		return
+	}
+	if len(s.queue) >= grokImportProbeQueueLimit {
+		s.mu.Unlock()
+		slog.Debug("grok_import_active_probe_dropped", "account_id", account.ID, "reason", "queue_full")
+		return
+	}
 	s.queue = append(s.queue, grokImportProbeTask{prober: prober, accountID: account.ID})
+	s.pending[account.ID] = struct{}{}
 	if s.workers < s.concurrency {
 		s.workers++
 		if s.workers > s.maxWorkers {
@@ -78,6 +97,7 @@ func (s *grokImportProbeScheduler) worker() {
 			return
 		}
 		s.run(task.prober, task.accountID)
+		s.finish(task.accountID)
 	}
 }
 
@@ -94,9 +114,17 @@ func (s *grokImportProbeScheduler) nextTask() (grokImportProbeTask, bool) {
 	if len(s.queue) == 0 {
 		s.queue = nil
 	}
+	delete(s.pending, task.accountID)
+	s.inFlight[task.accountID] = struct{}{}
 	return task, true
 }
 
+func (s *grokImportProbeScheduler) finish(accountID int64) {
+	s.mu.Lock()
+	delete(s.inFlight, accountID)
+	s.mu.Unlock()
+}
+
 func (s *grokImportProbeScheduler) run(prober grokImportProber, accountID int64) {
 	defer func() {
 		if recovered := recover(); recovered != nil {
@@ -108,8 +136,6 @@ func (s *grokImportProbeScheduler) run(prober grokImportProber, accountID int64)
 		}
 	}()
 
-	// Queue time is intentionally excluded: every imported account is probed,
-	// while this timeout only bounds the actual upstream probe execution.
 	ctx, cancel := context.WithTimeout(context.Background(), s.timeout)
 	defer cancel()
 	result, err := prober.QueryQuota(ctx, accountID)
diff --git a/backend/internal/handler/admin/grok_import_probe_test.go b/backend/internal/handler/admin/grok_import_probe_test.go
index 255f04d0dc..f4d8567463 100644
--- a/backend/internal/handler/admin/grok_import_probe_test.go
+++ b/backend/internal/handler/admin/grok_import_probe_test.go
@@ -142,7 +142,7 @@ func TestGrokImportProbeSchedulerProbesSingleAccountOnce(t *testing.T) {
 }
 
 func TestGrokImportProbeSchedulerQueuesBatchWithoutPerTaskGoroutines(t *testing.T) {
-	const taskCount = 100
+	const taskCount = 50
 	release := make(chan struct{})
 	scheduler := newGrokImportProbeScheduler(3, time.Second)
 	prober := newGrokImportProbeStub(taskCount)
@@ -156,7 +156,7 @@ func TestGrokImportProbeSchedulerQueuesBatchWithoutPerTaskGoroutines(t *testing.
 		awaitGrokProbeSignal(t, prober.started)
 	}
 	snapshot := snapshotGrokImportProbeScheduler(scheduler)
-	require.Equal(t, 97, snapshot.queued)
+	require.Equal(t, taskCount-3, snapshot.queued)
 	require.Equal(t, 3, snapshot.workers)
 	require.Equal(t, 3, snapshot.maxWorkers)
 	select {
@@ -182,6 +182,55 @@ func TestGrokImportProbeSchedulerQueuesBatchWithoutPerTaskGoroutines(t *testing.
 	require.Equal(t, 3, snapshot.maxWorkers)
 }
 
+func TestGrokImportProbeSchedulerDeduplicatesPendingAndInFlightAccounts(t *testing.T) {
+	scheduler := newGrokImportProbeScheduler(1, time.Second)
+	prober := newGrokImportProbeStub(2)
+	release := make(chan struct{})
+	prober.block = release
+	account := newGrokOAuthImportAccount(501)
+	queued := newGrokOAuthImportAccount(502)
+
+	scheduler.schedule(prober, account)
+	require.Equal(t, int64(501), awaitGrokProbeSignal(t, prober.started))
+	scheduler.schedule(prober, account)
+	scheduler.schedule(prober, queued)
+	scheduler.schedule(prober, queued)
+
+	scheduler.mu.Lock()
+	require.Len(t, scheduler.queue, 1)
+	require.Contains(t, scheduler.inFlight, int64(501))
+	require.Contains(t, scheduler.pending, int64(502))
+	scheduler.mu.Unlock()
+
+	close(release)
+	require.Equal(t, int64(501), awaitGrokProbeSignal(t, prober.done))
+	require.Equal(t, int64(502), awaitGrokProbeSignal(t, prober.done))
+	calls, _, _ := prober.snapshot()
+	require.Equal(t, 1, calls[501])
+	require.Equal(t, 1, calls[502])
+}
+
+func TestGrokImportProbeSchedulerBoundsPendingQueue(t *testing.T) {
+	scheduler := newGrokImportProbeScheduler(1, time.Second)
+	prober := newGrokImportProbeStub(grokImportProbeQueueLimit + 1)
+	release := make(chan struct{})
+	prober.block = release
+	scheduler.schedule(prober, newGrokOAuthImportAccount(600))
+	require.Equal(t, int64(600), awaitGrokProbeSignal(t, prober.started))
+	for id := int64(601); id < 601+grokImportProbeQueueLimit+10; id++ {
+		scheduler.schedule(prober, newGrokOAuthImportAccount(id))
+	}
+
+	scheduler.mu.Lock()
+	require.Len(t, scheduler.queue, grokImportProbeQueueLimit)
+	scheduler.mu.Unlock()
+
+	close(release)
+	for i := 0; i < grokImportProbeQueueLimit+1; i++ {
+		awaitGrokProbeSignal(t, prober.done)
+	}
+}
+
 func TestGrokImportProbeSchedulerTimeoutCancelsProbe(t *testing.T) {
 	neverRelease := make(chan struct{})
 	scheduler := newGrokImportProbeScheduler(1, 20*time.Millisecond)