diff --git a/ydb/core/mind/hive/monitoring.cpp b/ydb/core/mind/hive/monitoring.cpp
index efd4ca0f709d..c89871cf35eb 100644
--- a/ydb/core/mind/hive/monitoring.cpp
+++ b/ydb/core/mind/hive/monitoring.cpp
@@ -2859,6 +2859,7 @@ class TReassignTabletWaitActor : public TActor<TReassignTabletWaitActor>, public
     ui32 TabletsTotal = std::numeric_limits<ui32>::max();
     ui32 TabletsDone = 0;
     THive* Hive;
+    NJson::TJsonValue Response;
 
     static constexpr NKikimrServices::TActivity::EType ActorActivityType() {
         return NKikimrServices::TActivity::HIVE_MON_REQUEST;
@@ -2883,10 +2884,24 @@ class TReassignTabletWaitActor : public TActor<TReassignTabletWaitActor>, public
         return SelfId().LocalId();
     }
 
+<<<<<<< HEAD
     void Handle(TEvPrivate::TEvRestartComplete::TPtr&) {
         ++TabletsDone;
+=======
+    void AddTablet(TLeaderTabletInfo* tablet) {
+        tablet->ActorsToNotifyOnRestart.push_back(SelfId());
+        ++TabletsTotal;
+    }
+
+    void AddContext(const TString& key, const TString& value) {
+        Response[key] = value;
+    }
+
+    void CheckCompletion() {
+>>>>>>> 3dc0eba1e0e (remove legacy multiple tablets reassign http api (#29554))
         if (TabletsDone >= TabletsTotal) {
-            Send(Source, new NMon::TEvRemoteJsonInfoRes(TStringBuilder() << "{\"total\":" << TabletsDone << "}"));
+            Response["total"] = TabletsDone;
+            Send(Source, new NMon::TEvRemoteJsonInfoRes(NJson::WriteJson(Response, false)));
             PassAway();
         }
     }
@@ -2901,30 +2916,83 @@ class TReassignTabletWaitActor : public TActor<TReassignTabletWaitActor>, public
 
 class TTxMonEvent_ReassignTablet : public TTransactionBase<THive> {
 public:
+    struct TTabletFilter {
+        struct TAllTablets {};
+
+        std::variant<std::monostate, TTabletId, TAllTablets> TabletId;
+        TTabletTypes::EType TabletType = TTabletTypes::TypeInvalid;
+
+        explicit TTabletFilter(const TCgiParameters& cgi) {
+            auto tablet = cgi.Get("tablet");
+            if (tablet == "all") {
+                TabletId = TAllTablets();
+            } else if (auto tabletId = TryFromString<TTabletId>(tablet)) {
+                TabletId = *tabletId;
+            }
+
+            TabletType = (TTabletTypes::EType)FromStringWithDefault<int>(cgi.Get("type"), TabletType);
+        }
+
+        bool CheckTabletId(const TLeaderTabletInfo* tablet) const {
+            if (auto* tabletId = std::get_if<TTabletId>(&TabletId)) {
+                return tablet->Id == *tabletId;
+            }
+            return true;
+        }
+
+        bool CheckTabletType(const TLeaderTabletInfo* tablet) const {
+            return TabletType == TTabletTypes::TypeInvalid || TabletType == tablet->Type;
+        }
+
+        bool operator()(const TLeaderTabletInfo* tablet) const {
+            return CheckTabletId(tablet) && CheckTabletType(tablet);
+        }
+
+        bool IsValidFilter(TString& error) const {
+            if (std::holds_alternative<std::monostate>(TabletId)) {
+                error = "must specify tablet";
+                return false;
+            }
+            return true;
+        }
+
+        bool AllowsEverything() const {
+            return std::holds_alternative<TAllTablets>(TabletId) && TabletType == TTabletTypes::TypeInvalid;
+        }
+
+    };
+
     TAutoPtr<NMon::TEvRemoteHttpInfo> Event;
     const TActorId Source;
-    TTabletId TabletId = 0;
-    TTabletTypes::EType TabletType = TTabletTypes::TypeInvalid;
+    TTabletFilter TabletFilter;
     TVector<ui32> TabletChannels;
     ui32 GroupId = 0;
     TVector<ui32> ForcedGroupIds;
-    int TabletPercent = 100;
     TString Error;
     bool Wait = true;
+<<<<<<< HEAD
+=======
+    bool Async = false;
+    bool BypassLimit = false;
+
+    static constexpr size_t REASSIGN_SOFT_LIMIT = 500;
+>>>>>>> 3dc0eba1e0e (remove legacy multiple tablets reassign http api (#29554))
 
     TTxMonEvent_ReassignTablet(const TActorId& source, NMon::TEvRemoteHttpInfo::TPtr& ev, TSelf* hive)
         : TBase(hive)
         , Event(ev->Release())
         , Source(source)
+        , TabletFilter(Event->Cgi())
     {
-        TabletId = FromStringWithDefault<TTabletId>(Event->Cgi().Get("tablet"), TabletId);
-        TabletType = (TTabletTypes::EType)FromStringWithDefault<int>(Event->Cgi().Get("type"), TabletType);
         TabletChannels = Scan<ui32>(SplitString(Event->Cgi().Get("channel"), ","));
-        TabletPercent = FromStringWithDefault<int>(Event->Cgi().Get("percent"), TabletPercent);
         GroupId = FromStringWithDefault(Event->Cgi().Get("group"), GroupId);
         ForcedGroupIds = Scan<ui32>(SplitString(Event->Cgi().Get("forcedGroup"), ","));
-        TabletPercent = std::min(std::abs(TabletPercent), 100);
         Wait = FromStringWithDefault(Event->Cgi().Get("wait"), Wait);
+<<<<<<< HEAD
+=======
+        Async = FromStringWithDefault(Event->Cgi().Get("async"), Async);
+        BypassLimit = FromStringWithDefault(Event->Cgi().Get("bypassLimit"), BypassLimit);
+>>>>>>> 3dc0eba1e0e (remove legacy multiple tablets reassign http api (#29554))
     }
 
     TTxType GetTxType() const override { return NHive::TXTYPE_MON_REASSIGN_TABLET; }
@@ -2951,6 +3019,7 @@ class TTxMonEvent_ReassignTablet : public TTransactionBase<THive> {
             Error = "forcedGroup size should be equal to channel size";
             return true;
         }
+<<<<<<< HEAD
         TVector<TLeaderTabletInfo*> tablets;
         if (TabletId != 0) {
             TLeaderTabletInfo* tablet = Self->FindTablet(TabletId);
@@ -2967,13 +3036,23 @@ class TTxMonEvent_ReassignTablet : public TTransactionBase<THive> {
             for (auto& pr : Self->Tablets) {
                 tablets.push_back(&pr.second);
             }
+=======
+        if (!ForcedGroupIds.empty() && Async) {
+            Error = "cannot provide force groups in async mode";
+            return true;
         }
-        if (TabletPercent != 100) {
-            std::sort(tablets.begin(), tablets.end(), [this](TLeaderTabletInfo* a, TLeaderTabletInfo* b) -> bool {
-                return GetMaxTimestamp(a) < GetMaxTimestamp(b);
-            });
-            tablets.resize(tablets.size() * TabletPercent / 100);
+        if (!TabletFilter.IsValidFilter(Error)) {
+            return true;
+>>>>>>> 3dc0eba1e0e (remove legacy multiple tablets reassign http api (#29554))
+        }
+        if (TabletFilter.AllowsEverything() && GroupId == 0) {
+            Error = "cannot reassign all tablets";
+            return true;
         }
+        auto tablets = Self->Tablets
+            | std::views::transform([](auto&& p) -> TLeaderTabletInfo* { return &p.second; })
+            | std::views::filter(TabletFilter);
+
         TVector<THolder<TEvHive::TEvReassignTablet>> operations;
         TActorId waitActorId;
         TReassignTabletWaitActor* waitActor = nullptr;
@@ -3011,7 +3090,17 @@ class TTxMonEvent_ReassignTablet : public TTransactionBase<THive> {
             if (Wait) {
                 tablet->ActorsToNotifyOnRestart.emplace_back(waitActorId); // volatile settings, will not persist upon restart
             }
+<<<<<<< HEAD
             operations.emplace_back(new TEvHive::TEvReassignTablet(tablet->Id, channels, forcedGroupIds));
+=======
+            operations.emplace_back(new TEvHive::TEvReassignTablet(tablet->Id, channels, forcedGroupIds, Async));
+            if (!BypassLimit && operations.size() >= REASSIGN_SOFT_LIMIT) {
+                if (Wait) {
+                    waitActor->AddContext("limit_reached", "true");
+                }
+                break;
+            }
+>>>>>>> 3dc0eba1e0e (remove legacy multiple tablets reassign http api (#29554))
         }
         if (Wait) {
             waitActor->TabletsTotal = operations.size();