diff --git a/CHANGES.rst b/CHANGES.rst
index 050c63a590544f43274eb4e0a38e84d9880e2e0b..1a02d135c4a17e8be6c3fe1787f1081339e6dea9 100644
--- a/CHANGES.rst
+++ b/CHANGES.rst
@@ -95,9 +95,14 @@ Smart Rollup node
   ``/local/outbox/pending/executable`` and
   ``/local/outbox/pending/unexecutable``. (MR :gl:`!16831`)
 
-- Add a new RPC RPC ``/local/outbox/pending`` to fetch all known outbox messages
+- Add a new RPC ``/local/outbox/pending`` to fetch all known outbox messages
   with their status. (MR :gl:`!16831`)
 
+
+- Use correct constant to determine executable or lost outbox messages for RPCs
+  ``/local/outbox/pending`` and ``/local/outbox/pending/executable``. (MR
+  :gl:`!17279`)
+
 Smart Rollup WASM Debugger
 --------------------------
 
diff --git a/src/lib_smart_rollup/rollup_constants.ml b/src/lib_smart_rollup/rollup_constants.ml
index 37d1b96bac6c0ae0fb30d837251a6348352c16a9..93f74b15501b8fa22932a8cddf86511f8530d229 100644
--- a/src/lib_smart_rollup/rollup_constants.ml
+++ b/src/lib_smart_rollup/rollup_constants.ml
@@ -45,6 +45,7 @@ type sc_rollup_constants = {
   commitment_period_in_blocks : int;
   reveal_activation_level : reveal_activation_level option;
   max_number_of_stored_cemented_commitments : int;
+  max_active_outbox_levels : int;
 }
 
 type protocol_constants = {
@@ -100,6 +101,7 @@ let encoding =
                commitment_period_in_blocks;
                reveal_activation_level;
                max_number_of_stored_cemented_commitments;
+               max_active_outbox_levels;
              };
            dal =
              {
@@ -114,7 +116,8 @@ let encoding =
         ( challenge_window_in_blocks,
           commitment_period_in_blocks,
           reveal_activation_level,
-          max_number_of_stored_cemented_commitments ),
+          max_number_of_stored_cemented_commitments,
+          max_active_outbox_levels ),
         (feature_enable, attestation_lag, number_of_slots, cryptobox_parameters)
       ))
     (fun ( minimal_block_delay,
@@ -122,7 +125,8 @@ let encoding =
            ( challenge_window_in_blocks,
              commitment_period_in_blocks,
              reveal_activation_level,
-             max_number_of_stored_cemented_commitments ),
+             max_number_of_stored_cemented_commitments,
+             max_active_outbox_levels ),
            ( feature_enable,
              attestation_lag,
              number_of_slots,
@@ -136,6 +140,7 @@ let encoding =
             commitment_period_in_blocks;
             reveal_activation_level;
             max_number_of_stored_cemented_commitments;
+            max_active_outbox_levels;
           };
         dal =
           {
@@ -150,11 +155,12 @@ let encoding =
        (req "delay_increment_per_round" int64)
        (req
           "sc_rollup"
-          (obj4
+          (obj5
              (req "challenge_window_in_blocks" int31)
              (req "commitment_period_in_blocks" int31)
              (opt "reveal_activation_level" reveal_activation_level_encoding)
-             (req "max_number_of_stored_cemented_commitments" int31)))
+             (req "max_number_of_stored_cemented_commitments" int31)
+             (req "max_active_outbox_levels" int31)))
        (req
           "dal"
           (obj4
diff --git a/src/lib_smart_rollup_node/node_context.ml b/src/lib_smart_rollup_node/node_context.ml
index 8c3aa2971c331451ac5733c6bb2df0f23b72b563..ec9f352f4e5907fa10c61db18b432431fe7a6b8f 100644
--- a/src/lib_smart_rollup_node/node_context.ml
+++ b/src/lib_smart_rollup_node/node_context.ml
@@ -674,11 +674,10 @@ let get_executable_pending_outbox_messages ?outbox_level
   let max_level = (Reference.get lcc).level in
   let constants = (Reference.get current_protocol).constants.sc_rollup in
   let min_level =
-    Int32.sub
-      max_level
-      (Int32.of_int
-         (constants.max_number_of_stored_cemented_commitments
-        * constants.commitment_period_in_blocks))
+    Int32.sub max_level (Int32.of_int constants.max_active_outbox_levels)
+    |> Int32.succ
+    (* Protocol uses strict inequality, see function [validate_outbox_level] in
+       src/proto_alpha/lib_protocol/sc_rollup_operations.ml. *)
   in
   match outbox_level with
   | None -> Store.Outbox_messages.pending store ~min_level ~max_level
@@ -723,13 +722,13 @@ let get_pending_outbox_messages ?outbox_level
   in
   let lcc = (Reference.get lcc).level in
   let constants = (Reference.get current_protocol).constants.sc_rollup in
+  (* Messages below, and including, this level are lost because protocol uses
+     strict inequality. See function [validate_outbox_level] in
+     src/proto_alpha/lib_protocol/sc_rollup_operations.ml. *)
   let lost_level =
-    Int32.sub
-      lcc
-      (Int32.of_int
-         (constants.max_number_of_stored_cemented_commitments
-        * constants.commitment_period_in_blocks))
+    Int32.sub lcc (Int32.of_int constants.max_active_outbox_levels)
   in
+
   let+ messages =
     match outbox_level with
     | None -> Store.Outbox_messages.pending store ~min_level:0l ~max_level
@@ -743,7 +742,7 @@ let get_pending_outbox_messages ?outbox_level
   List.rev_map
     (fun ((outbox_level, _) as msg) ->
       let status =
-        if outbox_level < lost_level then `Lost
+        if outbox_level <= lost_level then `Lost
         else if outbox_level <= lcc then `Executable
         else `Pending
       in
diff --git a/src/lib_smart_rollup_node/node_context_loader.ml b/src/lib_smart_rollup_node/node_context_loader.ml
index 7817449db7c000e616571a40803dd7231405c3cf..cb6c5888f03abf6dbc77958df42c606d6cef1977 100644
--- a/src/lib_smart_rollup_node/node_context_loader.ml
+++ b/src/lib_smart_rollup_node/node_context_loader.ml
@@ -459,6 +459,7 @@ module Internal_for_tests = struct
                         dal_attested_slots_validity_lag = Int32.max_int;
                       };
                   max_number_of_stored_cemented_commitments = 0;
+                  max_active_outbox_levels = 0;
                 };
               dal =
                 {
diff --git a/src/lib_smart_rollup_node/test/helpers/helpers.ml b/src/lib_smart_rollup_node/test/helpers/helpers.ml
index d48eba01faec437a91d2a484880963d95dd18760..656f5a81ab270da5c1cb9eb58f12afd5f6ac99ae 100644
--- a/src/lib_smart_rollup_node/test/helpers/helpers.ml
+++ b/src/lib_smart_rollup_node/test/helpers/helpers.ml
@@ -42,38 +42,49 @@ let make_block_hash level messages =
 let default_constants =
   (* Same as default test constants for alpha excepted for
      commitment_period_in_block. *)
+  let open Tezos_protocol_alpha.Protocol.Alpha_context in
+  let Constants.Parametric.
+        {
+          minimal_block_delay;
+          delay_increment_per_round;
+          sc_rollup =
+            {
+              challenge_window_in_blocks;
+              reveal_activation_level;
+              max_number_of_stored_cemented_commitments;
+              max_active_outbox_levels;
+              _;
+            };
+          dal =
+            {
+              feature_enable;
+              attestation_lag;
+              number_of_slots;
+              cryptobox_parameters;
+              _;
+            };
+          _;
+        } =
+    Tezos_protocol_alpha_parameters.Default_parameters.constants_test
+  in
   Rollup_constants.
     {
-      minimal_block_delay = 1L;
-      delay_increment_per_round = 1L;
+      minimal_block_delay = Period.to_seconds minimal_block_delay;
+      delay_increment_per_round = Period.to_seconds delay_increment_per_round;
       sc_rollup =
         {
-          challenge_window_in_blocks = 4032;
+          challenge_window_in_blocks;
           commitment_period_in_blocks = 3;
           reveal_activation_level =
             Some
-              {
-                blake2B = 0l;
-                metadata = 0l;
-                dal_page = 0l;
-                dal_parameters = 0l;
-                dal_attested_slots_validity_lag = Int32.max_int;
-              };
-          max_number_of_stored_cemented_commitments = 5;
+              (Tezos_smart_rollup_layer2_alpha.Sc_rollup_proto_types.Constants
+               .reveal_activation_level_to_octez
+                 reveal_activation_level);
+          max_number_of_stored_cemented_commitments;
+          max_active_outbox_levels = Int32.to_int max_active_outbox_levels;
         };
       dal =
-        {
-          feature_enable = false;
-          attestation_lag = 4;
-          number_of_slots = 16;
-          cryptobox_parameters =
-            {
-              redundancy_factor = 8;
-              page_size = 4096;
-              slot_size = 32768;
-              number_of_shards = 64;
-            };
-        };
+        {feature_enable; attestation_lag; number_of_slots; cryptobox_parameters};
     }
 
 let add_l2_genesis_block (node_ctxt : _ Node_context.t) ~boot_sector =
diff --git a/src/proto_017_PtNairob/lib_sc_rollup_node/layer1_helpers.ml b/src/proto_017_PtNairob/lib_sc_rollup_node/layer1_helpers.ml
index cf87e038cf28c382d78b5e6092f1b49957647e04..fc7cdd3563089d40d6f8d564d4f527056c8b4f4e 100644
--- a/src/proto_017_PtNairob/lib_sc_rollup_node/layer1_helpers.ml
+++ b/src/proto_017_PtNairob/lib_sc_rollup_node/layer1_helpers.ml
@@ -135,6 +135,7 @@ let constants_of_parametric
             challenge_window_in_blocks;
             commitment_period_in_blocks;
             max_number_of_stored_cemented_commitments;
+            max_active_outbox_levels;
             _;
           };
         dal =
@@ -158,6 +159,7 @@ let constants_of_parametric
           commitment_period_in_blocks;
           reveal_activation_level = None;
           max_number_of_stored_cemented_commitments;
+          max_active_outbox_levels = Int32.to_int max_active_outbox_levels;
         };
       dal =
         {feature_enable; attestation_lag; number_of_slots; cryptobox_parameters};
diff --git a/src/proto_018_Proxford/lib_sc_rollup_node/layer1_helpers.ml b/src/proto_018_Proxford/lib_sc_rollup_node/layer1_helpers.ml
index 69fbaad853c199687c33f164ee8b115c8675574f..42537b7c44b24bec293bea848b12832421e23263 100644
--- a/src/proto_018_Proxford/lib_sc_rollup_node/layer1_helpers.ml
+++ b/src/proto_018_Proxford/lib_sc_rollup_node/layer1_helpers.ml
@@ -136,6 +136,7 @@ let constants_of_parametric
             commitment_period_in_blocks;
             reveal_activation_level;
             max_number_of_stored_cemented_commitments;
+            max_active_outbox_levels;
             _;
           };
         dal =
@@ -162,6 +163,7 @@ let constants_of_parametric
               (Sc_rollup_proto_types.Constants.reveal_activation_level_to_octez
                  reveal_activation_level);
           max_number_of_stored_cemented_commitments;
+          max_active_outbox_levels = Int32.to_int max_active_outbox_levels;
         };
       dal =
         {feature_enable; attestation_lag; number_of_slots; cryptobox_parameters};
diff --git a/src/proto_019_PtParisB/lib_sc_rollup_node/layer1_helpers.ml b/src/proto_019_PtParisB/lib_sc_rollup_node/layer1_helpers.ml
index 69fbaad853c199687c33f164ee8b115c8675574f..42537b7c44b24bec293bea848b12832421e23263 100644
--- a/src/proto_019_PtParisB/lib_sc_rollup_node/layer1_helpers.ml
+++ b/src/proto_019_PtParisB/lib_sc_rollup_node/layer1_helpers.ml
@@ -136,6 +136,7 @@ let constants_of_parametric
             commitment_period_in_blocks;
             reveal_activation_level;
             max_number_of_stored_cemented_commitments;
+            max_active_outbox_levels;
             _;
           };
         dal =
@@ -162,6 +163,7 @@ let constants_of_parametric
               (Sc_rollup_proto_types.Constants.reveal_activation_level_to_octez
                  reveal_activation_level);
           max_number_of_stored_cemented_commitments;
+          max_active_outbox_levels = Int32.to_int max_active_outbox_levels;
         };
       dal =
         {feature_enable; attestation_lag; number_of_slots; cryptobox_parameters};
diff --git a/src/proto_020_PsParisC/lib_sc_rollup_node/layer1_helpers.ml b/src/proto_020_PsParisC/lib_sc_rollup_node/layer1_helpers.ml
index be34d0530273bc66c97dab912cd06445987e1846..3781c46aac9921f1f95e359f1cc1ab590a0d5ff0 100644
--- a/src/proto_020_PsParisC/lib_sc_rollup_node/layer1_helpers.ml
+++ b/src/proto_020_PsParisC/lib_sc_rollup_node/layer1_helpers.ml
@@ -136,6 +136,7 @@ let constants_of_parametric
             commitment_period_in_blocks;
             reveal_activation_level;
             max_number_of_stored_cemented_commitments;
+            max_active_outbox_levels;
             _;
           };
         dal =
@@ -162,6 +163,7 @@ let constants_of_parametric
               (Sc_rollup_proto_types.Constants.reveal_activation_level_to_octez
                  reveal_activation_level);
           max_number_of_stored_cemented_commitments;
+          max_active_outbox_levels = Int32.to_int max_active_outbox_levels;
         };
       dal =
         {feature_enable; attestation_lag; number_of_slots; cryptobox_parameters};
diff --git a/src/proto_021_PsQuebec/lib_sc_rollup_node/layer1_helpers.ml b/src/proto_021_PsQuebec/lib_sc_rollup_node/layer1_helpers.ml
index 51a92aaf69715c35fc74b42b6eb49e9d914c5067..2a1a85e1d0478a0c7c3ead5740bdb6fcd274e152 100644
--- a/src/proto_021_PsQuebec/lib_sc_rollup_node/layer1_helpers.ml
+++ b/src/proto_021_PsQuebec/lib_sc_rollup_node/layer1_helpers.ml
@@ -136,6 +136,7 @@ let constants_of_parametric
             commitment_period_in_blocks;
             reveal_activation_level;
             max_number_of_stored_cemented_commitments;
+            max_active_outbox_levels;
             _;
           };
         dal =
@@ -162,6 +163,7 @@ let constants_of_parametric
               (Sc_rollup_proto_types.Constants.reveal_activation_level_to_octez
                  reveal_activation_level);
           max_number_of_stored_cemented_commitments;
+          max_active_outbox_levels = Int32.to_int max_active_outbox_levels;
         };
       dal =
         {feature_enable; attestation_lag; number_of_slots; cryptobox_parameters};
diff --git a/src/proto_022_PsRiotum/lib_sc_rollup_node/layer1_helpers.ml b/src/proto_022_PsRiotum/lib_sc_rollup_node/layer1_helpers.ml
index 51a92aaf69715c35fc74b42b6eb49e9d914c5067..2a1a85e1d0478a0c7c3ead5740bdb6fcd274e152 100644
--- a/src/proto_022_PsRiotum/lib_sc_rollup_node/layer1_helpers.ml
+++ b/src/proto_022_PsRiotum/lib_sc_rollup_node/layer1_helpers.ml
@@ -136,6 +136,7 @@ let constants_of_parametric
             commitment_period_in_blocks;
             reveal_activation_level;
             max_number_of_stored_cemented_commitments;
+            max_active_outbox_levels;
             _;
           };
         dal =
@@ -162,6 +163,7 @@ let constants_of_parametric
               (Sc_rollup_proto_types.Constants.reveal_activation_level_to_octez
                  reveal_activation_level);
           max_number_of_stored_cemented_commitments;
+          max_active_outbox_levels = Int32.to_int max_active_outbox_levels;
         };
       dal =
         {feature_enable; attestation_lag; number_of_slots; cryptobox_parameters};
diff --git a/src/proto_alpha/lib_sc_rollup_node/layer1_helpers.ml b/src/proto_alpha/lib_sc_rollup_node/layer1_helpers.ml
index 6aae50684e54a787a4b7db00ea8749fb831b1356..023570d04c3b5a6a6700e86faa4913bb467a1d6b 100644
--- a/src/proto_alpha/lib_sc_rollup_node/layer1_helpers.ml
+++ b/src/proto_alpha/lib_sc_rollup_node/layer1_helpers.ml
@@ -136,6 +136,7 @@ let constants_of_parametric
             commitment_period_in_blocks;
             reveal_activation_level;
             max_number_of_stored_cemented_commitments;
+            max_active_outbox_levels;
             _;
           };
         dal =
@@ -162,6 +163,7 @@ let constants_of_parametric
               (Sc_rollup_proto_types.Constants.reveal_activation_level_to_octez
                  reveal_activation_level);
           max_number_of_stored_cemented_commitments;
+          max_active_outbox_levels = Int32.to_int max_active_outbox_levels;
         };
       dal =
         {feature_enable; attestation_lag; number_of_slots; cryptobox_parameters};