diff --git a/src/disco/gui/fd_gui.c b/src/disco/gui/fd_gui.c
index 7ed440baec..65d9899e5c 100644
--- a/src/disco/gui/fd_gui.c
+++ b/src/disco/gui/fd_gui.c
@@ -1732,6 +1732,7 @@ fd_gui_microblock_execution_begin( fd_gui_t *   gui,
     txn_entry->flags                      |= (uchar)FD_GUI_TXN_FLAGS_STARTED;
     txn_entry->flags                      |= (uchar)fd_uint_if(txn_payload->flags & FD_TXN_P_FLAGS_IS_SIMPLE_VOTE, FD_GUI_TXN_FLAGS_IS_SIMPLE_VOTE, 0U);
     txn_entry->flags                      |= (uchar)fd_uint_if((txn_payload->flags & FD_TXN_P_FLAGS_BUNDLE) || (txn_payload->flags & FD_TXN_P_FLAGS_INITIALIZER_BUNDLE), FD_GUI_TXN_FLAGS_FROM_BUNDLE, 0U);
+    txn_entry->flags                      |= (uchar)fd_uint_if(txn_payload->flags & FD_TXN_P_FLAGS_SCHEDULED_WHILE_LEADER, FD_GUI_TXN_FLAGS_SCHEDULED_WHILE_LEADER, 0U);
   }
 
   /* At the moment, bank publishes at most 1 transaction per microblock,
diff --git a/src/disco/gui/fd_gui.h b/src/disco/gui/fd_gui.h
index bb6412d69f..204cd0266b 100644
--- a/src/disco/gui/fd_gui.h
+++ b/src/disco/gui/fd_gui.h
@@ -58,6 +58,7 @@
 #define FD_GUI_TXN_FLAGS_IS_SIMPLE_VOTE  ( 4U)
 #define FD_GUI_TXN_FLAGS_FROM_BUNDLE     ( 8U)
 #define FD_GUI_TXN_FLAGS_LANDED_IN_BLOCK (16U)
+#define FD_GUI_TXN_FLAGS_SCHEDULED_WHILE_LEADER (32U)
 
 struct fd_gui_gossip_peer {
   fd_pubkey_t pubkey[ 1 ];
diff --git a/src/disco/gui/fd_gui_printf.c b/src/disco/gui/fd_gui_printf.c
index 51d2e3388e..f7c5a9117d 100644
--- a/src/disco/gui/fd_gui_printf.c
+++ b/src/disco/gui/fd_gui_printf.c
@@ -1267,6 +1267,9 @@ fd_gui_printf_slot_transactions_request( fd_gui_t * gui,
           jsonp_open_array( gui, "txn_landed" );
             for( ulong i=0UL; i<txn_cnt; i++) jsonp_bool( gui, NULL, gui->txs[ (slot->txs.start_offset + i)%FD_GUI_TXN_HISTORY_SZ ]->flags & FD_GUI_TXN_FLAGS_LANDED_IN_BLOCK );
           jsonp_close_array( gui );
+          jsonp_open_array( gui, "txn_arrived_in_slot" );
+            for( ulong i=0UL; i<txn_cnt; i++) jsonp_bool( gui, NULL, gui->txs[ (slot->txs.start_offset + i)%FD_GUI_TXN_HISTORY_SZ ]->flags & FD_GUI_TXN_FLAGS_SCHEDULED_WHILE_LEADER );
+          jsonp_close_array( gui );
         jsonp_close_object( gui );
       } else {
         jsonp_null( gui, "compute_units" );
diff --git a/src/disco/pack/fd_pack.c b/src/disco/pack/fd_pack.c
index 8b98b01b8a..0317d8d67b 100644
--- a/src/disco/pack/fd_pack.c
+++ b/src/disco/pack/fd_pack.c
@@ -51,6 +51,12 @@ struct fd_pack_private_ord_txn {
      expiration priority queue. */
   ulong expq_idx;
 
+  /* arrival_slot: The slot during which this transaction first arrived
+     to pack, if this validator was a leader at the time. Otherwise,
+     this is ULONG_MAX. This is used by monitoring tools to gauge if a
+     transaction.arrived in the same slot it was scheduled. */
+  ulong arrival_leader_slot;
+
   /* We want rewards*compute_est to fit in a ulong so that r1/c1 < r2/c2 can be
      computed as r1*c2 < r2*c1, with the product fitting in a ulong.
      compute_est has a small natural limit of mid-20 bits. rewards doesn't have
@@ -551,6 +557,7 @@ struct fd_pack_private {
   /* compressed_slot_number: a number in (FD_PACK_SKIP_CNT, USHORT_MAX]
      that advances each time we start packing for a new slot. */
   ushort     compressed_slot_number;
+  ulong      leader_slot;
 
   /* bitset_avail: a stack of which bits are not currently reserved and
      can be used to represent an account address.
@@ -1149,9 +1156,11 @@ populate_bitsets( fd_pack_t         * pack,
 int
 fd_pack_insert_txn_fini( fd_pack_t  * pack,
                          fd_txn_e_t * txne,
+                         ulong        leader_slot,
                          ulong        expires_at ) {
 
   fd_pack_ord_txn_t * ord = (fd_pack_ord_txn_t *)txne;
+  ord->arrival_leader_slot = leader_slot;
 
   fd_txn_t * txn   = TXN(txne->txnp);
   uchar * payload  = txne->txnp->payload;
@@ -1626,6 +1635,7 @@ fd_pack_schedule_impl( fd_pack_t          * pack,
 #   endif
 
     fd_pack_ord_txn_t * cur = treap_rev_iter_ele( _cur, pool );
+    cur->txn->flags &= fd_uint_if(cur->arrival_leader_slot == pack->leader_slot, cur->txn->flags | FD_TXN_P_FLAGS_SCHEDULED_WHILE_LEADER, cur->txn->flags & ~(FD_TXN_P_FLAGS_SCHEDULED_WHILE_LEADER));
 
     min_cus   = fd_ulong_min( min_cus,   cur->compute_est     );
     min_bytes = fd_ulong_min( min_bytes, cur->txn->payload_sz );
@@ -2044,6 +2054,8 @@ fd_pack_try_schedule_bundle( fd_pack_t  * pack,
 
   while( !(doesnt_fit | has_conflict) & !treap_rev_iter_done( _cur ) ) {
     fd_pack_ord_txn_t * cur = treap_rev_iter_ele( _cur, pool );
+    cur->txn->flags &= fd_uint_if(cur->arrival_leader_slot == pack->leader_slot, cur->txn->flags | FD_TXN_P_FLAGS_SCHEDULED_WHILE_LEADER, cur->txn->flags & ~(FD_TXN_P_FLAGS_SCHEDULED_WHILE_LEADER));
+
     ulong this_bundle_idx = RC_TO_REL_BUNDLE_IDX( cur->rewards, cur->compute_est );
     if( FD_UNLIKELY( this_bundle_idx!=bundle_idx ) ) break;
 
@@ -2403,6 +2415,11 @@ fd_pack_expire_before( fd_pack_t * pack,
   return deleted_cnt;
 }
 
+void
+fd_pack_start_block( fd_pack_t * pack, ulong leader_slot ) {
+  pack->leader_slot = leader_slot;
+}
+
 void
 fd_pack_end_block( fd_pack_t * pack ) {
   /* rounded division */
@@ -2412,6 +2429,7 @@ fd_pack_end_block( fd_pack_t * pack ) {
   fd_histf_sample( pack->rebated_cus_per_block,   pack->cumulative_rebated_cus                               );
   fd_histf_sample( pack->scheduled_cus_per_block, pack->cumulative_rebated_cus + pack->cumulative_block_cost );
 
+  pack->leader_slot                 = ULONG_MAX;
   pack->microblock_cnt              = 0UL;
   pack->data_bytes_consumed         = 0UL;
   pack->cumulative_block_cost       = 0UL;
@@ -2493,6 +2511,7 @@ release_tree( treap_t           * treap,
 void
 fd_pack_clear_all( fd_pack_t * pack ) {
   pack->pending_txn_cnt        = 0UL;
+  pack->leader_slot            = ULONG_MAX;
   pack->microblock_cnt         = 0UL;
   pack->cumulative_block_cost  = 0UL;
   pack->cumulative_vote_cost   = 0UL;
diff --git a/src/disco/pack/fd_pack.h b/src/disco/pack/fd_pack.h
index c9569d1c7c..7c73dd42d6 100644
--- a/src/disco/pack/fd_pack.h
+++ b/src/disco/pack/fd_pack.h
@@ -70,12 +70,13 @@
 
 /* ---- End consensus-critical constants */
 
-#define FD_TXN_P_FLAGS_IS_SIMPLE_VOTE     ( 1U)
-#define FD_TXN_P_FLAGS_BUNDLE             ( 2U)
-#define FD_TXN_P_FLAGS_INITIALIZER_BUNDLE ( 4U)
-#define FD_TXN_P_FLAGS_SANITIZE_SUCCESS   ( 8U)
-#define FD_TXN_P_FLAGS_EXECUTE_SUCCESS    (16U)
-#define FD_TXN_P_FLAGS_FEES_ONLY          (32U)
+#define FD_TXN_P_FLAGS_IS_SIMPLE_VOTE         ( 1U)
+#define FD_TXN_P_FLAGS_BUNDLE                 ( 2U)
+#define FD_TXN_P_FLAGS_INITIALIZER_BUNDLE     ( 4U)
+#define FD_TXN_P_FLAGS_SANITIZE_SUCCESS       ( 8U)
+#define FD_TXN_P_FLAGS_EXECUTE_SUCCESS        (16U)
+#define FD_TXN_P_FLAGS_FEES_ONLY              (32U)
+#define FD_TXN_P_FLAGS_SCHEDULED_WHILE_LEADER (64U)
 
 #define FD_TXN_P_FLAGS_RESULT_MASK  (0xFF000000U)
 
@@ -346,9 +347,9 @@ FD_STATIC_ASSERT( FD_PACK_INSERT_ACCEPT_VOTE_REPLACE<FD_PACK_INSERT_RETVAL_CNT-F
    returns one of the FD_PACK_INSERT_ACCEPT_* or FD_PACK_INSERT_REJECT_*
    codes explained above.
  */
-fd_txn_e_t * fd_pack_insert_txn_init  ( fd_pack_t * pack                                     );
-int          fd_pack_insert_txn_fini  ( fd_pack_t * pack, fd_txn_e_t * txn, ulong expires_at );
-void         fd_pack_insert_txn_cancel( fd_pack_t * pack, fd_txn_e_t * txn                   );
+fd_txn_e_t * fd_pack_insert_txn_init  ( fd_pack_t * pack                                                        );
+int          fd_pack_insert_txn_fini  ( fd_pack_t * pack, fd_txn_e_t * txn, ulong leader_slot, ulong expires_at );
+void         fd_pack_insert_txn_cancel( fd_pack_t * pack, fd_txn_e_t * txn                                      );
 
 /* fd_pack_insert_bundle_{init,fini,cancel} are parallel to the
    similarly named fd_pack_insert_txn functions but can be used to
@@ -633,10 +634,11 @@ void fd_pack_rebate_cus( fd_pack_t * pack, fd_pack_rebate_t const * rebate );
 int fd_pack_microblock_complete( fd_pack_t * pack, ulong bank_tile );
 
 /* fd_pack_expire_before deletes all available transactions with
-   expires_at values strictly less than expire_before.  pack must be a
-   local join of a pack object.  Returns the number of transactions
-   deleted.  Subsequent calls to fd_pack_expire_before with the same or
-   a smaller value are no-ops. */
+   expires_at values strictly less than expire_before, and updates pack
+   with the provides leader slot value. pack must be a local join of a
+   pack object.  Returns the number of transactions deleted.  Subsequent
+   calls to fd_pack_expire_before with the same or a smaller value are
+   no-ops. */
 ulong fd_pack_expire_before( fd_pack_t * pack, ulong expire_before );
 
 /* fd_pack_delete_txn removes a transaction (identified by its first
@@ -644,6 +646,11 @@ ulong fd_pack_expire_before( fd_pack_t * pack, ulong expire_before );
    transaction was found (and then removed) and 0 if not. */
 int fd_pack_delete_transaction( fd_pack_t * pack, fd_ed25519_sig_t const * sig0 );
 
+/* fd_pack_start_block resets state that is known at the beginning of
+block.  leader_slot is used by pack to set the
+FD_TXN_P_FLAGS_SCHEDULED_WHILE_LEADER flag on scheduled transactions. */
+void fd_pack_start_block( fd_pack_t * pack, ulong leader_slot );
+
 /* fd_pack_end_block resets some state to prepare for the next block.
    Specifically, the per-block limits are cleared and transactions in
    the microblocks scheduled after the call to this function are allowed
diff --git a/src/disco/pack/fd_pack_tile.c b/src/disco/pack/fd_pack_tile.c
index 91be28f939..ee3598c3a8 100644
--- a/src/disco/pack/fd_pack_tile.c
+++ b/src/disco/pack/fd_pack_tile.c
@@ -424,7 +424,7 @@ insert_from_extra( fd_pack_ctx_t * ctx ) {
   ulong blockhash_slot = insert->txnp->blockhash_slot;
 
   long insert_duration = -fd_tickcount();
-  int result = fd_pack_insert_txn_fini( ctx->pack, spot, blockhash_slot );
+  int result = fd_pack_insert_txn_fini( ctx->pack, spot, ctx->leader_slot, blockhash_slot );
   insert_duration      += fd_tickcount();
   ctx->insert_result[ result + FD_PACK_INSERT_RETVAL_OFF ]++;
   fd_histf_sample( ctx->insert_duration, (ulong)insert_duration );
@@ -972,7 +972,7 @@ after_frag( fd_pack_ctx_t *     ctx,
     } else {
       ulong blockhash_slot = sig;
       long insert_duration = -fd_tickcount();
-      int result = fd_pack_insert_txn_fini( ctx->pack, ctx->cur_spot, blockhash_slot );
+      int result = fd_pack_insert_txn_fini( ctx->pack, ctx->cur_spot, ctx->leader_slot, blockhash_slot );
       insert_duration      += fd_tickcount();
       ctx->insert_result[ result + FD_PACK_INSERT_RETVAL_OFF ]++;
       fd_histf_sample( ctx->insert_duration, (ulong)insert_duration );
diff --git a/src/disco/pack/test_pack.c b/src/disco/pack/test_pack.c
index 3bc059deb3..960072fe44 100644
--- a/src/disco/pack/test_pack.c
+++ b/src/disco/pack/test_pack.c
@@ -224,7 +224,7 @@ insert( ulong i,
   fd_memcpy( slot->txnp->payload, payload_scratch[ i ], payload_sz[ i ] );
   fd_memcpy( TXN(slot->txnp),     txn,     fd_txn_footprint( txn->instr_cnt, txn->addr_table_lookup_cnt ) );
 
-  return fd_pack_insert_txn_fini( pack, slot, i );
+  return fd_pack_insert_txn_fini( pack, slot, 0UL, i );
 }
 
 static void
@@ -588,7 +588,7 @@ performance_test2( void ) {
         fd_memcpy( slot->txnp->payload, payload_scratch[ i ], payload_sz[ i ]                                                );
         fd_memcpy( TXN(slot->txnp),     txn,                  fd_txn_footprint( txn->instr_cnt, txn->addr_table_lookup_cnt ) );
 
-        fd_pack_insert_txn_fini( pack, slot, 0UL );
+        fd_pack_insert_txn_fini( pack, slot, 0UL, 0UL );
       }
       ulong scheduled = 0UL;
       for( ulong i=0UL; i<1024UL/MAX_TXN_PER_MICROBLOCK+1UL; i++ ) {
@@ -677,7 +677,7 @@ void performance_test( int extra_bench ) {
         fd_memcpy( slot->txnp->payload, payload_scratch[ j&1 ], payload_sz[ j&1 ]                                              );
         fd_memcpy( TXN(slot->txnp),     txn,                    fd_txn_footprint( txn->instr_cnt, txn->addr_table_lookup_cnt ) );
 
-        fd_pack_insert_txn_fini( pack, slot, 0UL );
+        fd_pack_insert_txn_fini( pack, slot, 0UL, 0UL );
       }
       if( FD_LIKELY( iter>=WARMUP ) ) insert   += fd_log_wallclock( );
 
@@ -722,7 +722,7 @@ void performance_test( int extra_bench ) {
         fd_memcpy( slot->txnp->payload, payload_scratch[ j&1 ], payload_sz[ j&1 ]                                              );
         fd_memcpy( TXN(slot->txnp),     txn,                    fd_txn_footprint( txn->instr_cnt, txn->addr_table_lookup_cnt ) );
 
-        fd_pack_insert_txn_fini( pack, slot, 0UL );
+        fd_pack_insert_txn_fini( pack, slot, 0UL, 0UL );
       }
 
       FD_TEST( fd_pack_avail_txn_cnt( pack )==heap_sz );
@@ -750,7 +750,7 @@ void performance_test( int extra_bench ) {
         fd_memcpy( slot->txnp->payload, payload_scratch[ j&1 ], payload_sz[ j&1 ]                                              );
         fd_memcpy( TXN(slot->txnp),     txn,                    fd_txn_footprint( txn->instr_cnt, txn->addr_table_lookup_cnt ) );
 
-        fd_pack_insert_txn_fini( pack, slot, 0UL );
+        fd_pack_insert_txn_fini( pack, slot, 0UL, 0UL );
       }
 
       FD_TEST( fd_pack_avail_txn_cnt( pack )==heap_sz );
@@ -823,7 +823,7 @@ void performance_end_block( void ) {
         fd_memcpy( slot->txnp->payload, payload_scratch[ 0UL ], payload_sz[ 0UL ]                                              );
         fd_memcpy( TXN(slot->txnp),     txn,                    fd_txn_footprint( txn->instr_cnt, txn->addr_table_lookup_cnt ) );
 
-        fd_pack_insert_txn_fini( pack, slot, 0UL );
+        fd_pack_insert_txn_fini( pack, slot, 0UL, 0UL );
       }
       while( fd_pack_avail_txn_cnt( pack )>0UL ) {
         FD_TEST( fd_pack_schedule_next_microblock( pack, 5000000UL, 0.0f, 0UL, ALL, outcome.results ) );
@@ -856,7 +856,7 @@ void heap_overflow_test( void ) {
     fd_memcpy( slot->txnp->payload, payload_scratch[ j ], payload_sz[ j ]                                                );
     fd_memcpy( TXN(slot->txnp),     txn,                  fd_txn_footprint( txn->instr_cnt, txn->addr_table_lookup_cnt ) );
 
-    fd_pack_insert_txn_fini( pack, slot, 0UL );
+    fd_pack_insert_txn_fini( pack, slot, 0UL, 0UL );
   }
   FD_TEST( fd_pack_avail_txn_cnt( pack )==1024UL );
 
@@ -872,7 +872,7 @@ void heap_overflow_test( void ) {
     fd_memcpy( slot->txnp->payload, payload_scratch[ j ], payload_sz[ j ]                                              );
     fd_memcpy( TXN(slot->txnp),     txn,                  fd_txn_footprint( txn->instr_cnt, txn->addr_table_lookup_cnt ) );
 
-    fd_pack_insert_txn_fini( pack, slot, 0UL );
+    fd_pack_insert_txn_fini( pack, slot, 0UL, 0UL );
   }
 
   FD_TEST( fd_pack_avail_txn_cnt( pack )==1024UL );