diff --git a/etherlink/bin_node/lib_dev/block_producer.ml b/etherlink/bin_node/lib_dev/block_producer.ml
index c1d8b2d53be1d62e81a761bdf365efebef165a45..5039be27c8f6d2161f9f1b05a17c2ec596ad3bd2 100644
--- a/etherlink/bin_node/lib_dev/block_producer.ml
+++ b/etherlink/bin_node/lib_dev/block_producer.ml
@@ -280,9 +280,11 @@ module Handlers = struct
 
   let on_request :
       type r request_error.
-      worker -> (r, request_error) Request.t -> (r, request_error) result Lwt.t
-      =
-   fun w request ->
+      worker ->
+      (r, request_error) Request.t ->
+      Data_encoding.json option ->
+      (r, request_error) result Lwt.t =
+   fun w request _ ->
     let state = Worker.state w in
     match request with
     | Request.Produce_block (with_delayed_transactions, timestamp, force) ->
@@ -309,11 +311,11 @@ module Handlers = struct
   let on_launch _w () (parameters : Types.parameters) =
     Lwt_result_syntax.return parameters
 
-  let on_error (type a b) _w _st (_r : (a, b) Request.t) (_errs : b) :
+  let on_error (type a b) _w _st (_r : (a, b) Request.t) _ (_errs : b) :
       unit tzresult Lwt.t =
     Lwt_result_syntax.return_unit
 
-  let on_completion _ _ _ _ = Lwt.return_unit
+  let on_completion _ _ _ _ _ = Lwt.return_unit
 
   let on_no_request _ = Lwt.return_unit
 
diff --git a/etherlink/bin_node/lib_dev/blueprints_publisher.ml b/etherlink/bin_node/lib_dev/blueprints_publisher.ml
index b746d3fc27c57611c41845c5efa8a6960fc86149..6229e1e6127d8fed2af8a88fac611f5817807fe1 100644
--- a/etherlink/bin_node/lib_dev/blueprints_publisher.ml
+++ b/etherlink/bin_node/lib_dev/blueprints_publisher.ml
@@ -282,8 +282,11 @@ module Handlers = struct
 
   let on_request :
       type r request_error.
-      self -> (r, request_error) Request.t -> (r, request_error) result Lwt.t =
-   fun self request ->
+      self ->
+      (r, request_error) Request.t ->
+      Data_encoding.json option ->
+      (r, request_error) result Lwt.t =
+   fun self request _ ->
     let open Lwt_result_syntax in
     match request with
     | Publish {level; payload} ->
@@ -309,15 +312,15 @@ module Handlers = struct
                unlock the transaction pool in case it was locked. *)
             Tx_pool.unlock_transactions ())
 
-  let on_completion (type a err) _self (_r : (a, err) Request.t) (_res : a) _st
-      =
+  let on_completion (type a err) _self (_r : (a, err) Request.t) _ (_res : a)
+      _st =
     Lwt_syntax.return_unit
 
   let on_no_request _self = Lwt.return_unit
 
   let on_close _self = Lwt.return_unit
 
-  let on_error (type a b) _w _st (r : (a, b) Request.t) (errs : b) :
+  let on_error (type a b) _w _st (r : (a, b) Request.t) _ (errs : b) :
       unit tzresult Lwt.t =
     let open Lwt_result_syntax in
     let request_view = Request.view r in
diff --git a/etherlink/bin_node/lib_dev/evm_context.ml b/etherlink/bin_node/lib_dev/evm_context.ml
index f0074b180c529d356c172e423a04ad99652d0191..0c8433f4b66dcfe381d0269902be8f0584317a14 100644
--- a/etherlink/bin_node/lib_dev/evm_context.ml
+++ b/etherlink/bin_node/lib_dev/evm_context.ml
@@ -1589,8 +1589,11 @@ module Handlers = struct
 
   let on_request :
       type r request_error.
-      self -> (r, request_error) Request.t -> (r, request_error) result Lwt.t =
-   fun self request ->
+      self ->
+      (r, request_error) Request.t ->
+      Data_encoding.json option ->
+      (r, request_error) result Lwt.t =
+   fun self request _ ->
     let open Lwt_result_syntax in
     match request with
     | Apply_evm_events {finalized_level; events} ->
@@ -1648,8 +1651,8 @@ module Handlers = struct
           ctxt
           blueprint_with_events
 
-  let on_completion (type a err) _self (_r : (a, err) Request.t) (_res : a) _st
-      =
+  let on_completion (type a err) _self (_r : (a, err) Request.t) _ (_res : a)
+      _st =
     Lwt_syntax.return_unit
 
   let on_no_request _self = Lwt.return_unit
@@ -1671,7 +1674,7 @@ module Handlers = struct
       | Potential_observer_reorg _ -> Eq
   end
 
-  let on_error (type a b) _self _st (req : (a, b) Request.t) (errs : b) :
+  let on_error (type a b) _self _st (req : (a, b) Request.t) _ (errs : b) :
       unit tzresult Lwt.t =
     let open Lwt_result_syntax in
     match (req, errs) with
diff --git a/etherlink/bin_node/lib_dev/evm_events_follower.ml b/etherlink/bin_node/lib_dev/evm_events_follower.ml
index 680d1f7400b9d42c72a7cfff182933e4483dafb1..3063a1a126365641d601340aa4d294b5c307cbae 100644
--- a/etherlink/bin_node/lib_dev/evm_events_follower.ml
+++ b/etherlink/bin_node/lib_dev/evm_events_follower.ml
@@ -255,9 +255,11 @@ module Handlers = struct
 
   let on_request :
       type r request_error.
-      worker -> (r, request_error) Request.t -> (r, request_error) result Lwt.t
-      =
-   fun worker request ->
+      worker ->
+      (r, request_error) Request.t ->
+      Data_encoding.json option ->
+      (r, request_error) result Lwt.t =
+   fun worker request _ ->
     match request with
     | Request.New_rollup_node_block rollup_head ->
         protect @@ fun () -> new_rollup_block worker rollup_head
@@ -280,9 +282,10 @@ module Handlers = struct
       worker ->
       Tezos_base.Worker_types.request_status ->
       (r, request_error) Request.t ->
+      Data_encoding.json option ->
       request_error ->
       unit tzresult Lwt.t =
-   fun _w _ req errs ->
+   fun _w _ req _ errs ->
     let open Lwt_result_syntax in
     match req with
     | Request.New_rollup_node_block _ ->
@@ -300,7 +303,7 @@ module Handlers = struct
         in
         return_unit
 
-  let on_completion _ _ _ _ = Lwt.return_unit
+  let on_completion _ _ _ _ _ = Lwt.return_unit
 
   let on_no_request _ = Lwt.return_unit
 
diff --git a/etherlink/bin_node/lib_dev/evm_websocket.ml b/etherlink/bin_node/lib_dev/evm_websocket.ml
index bb3389a0eb2f2b8d7ccb55186691f34cfd8f193b..87f343c6ffc61b3be3106ed563e719e1e6602aa2 100644
--- a/etherlink/bin_node/lib_dev/evm_websocket.ml
+++ b/etherlink/bin_node/lib_dev/evm_websocket.ml
@@ -356,9 +356,11 @@ module Handlers = struct
 
   let on_request :
       type r request_error.
-      worker -> (r, request_error) Request.t -> (r, request_error) result Lwt.t
-      =
-   fun worker request ->
+      worker ->
+      (r, request_error) Request.t ->
+      Data_encoding.json option ->
+      (r, request_error) result Lwt.t =
+   fun worker request _ ->
     match request with
     | Request.Frame fr ->
         protect @@ fun () -> on_frame worker fr |> Lwt_result.ok
@@ -405,7 +407,7 @@ module Handlers = struct
     in
     return state
 
-  let on_error (type a b) _w st (r : (a, b) Request.t) (errs : b) :
+  let on_error (type a b) _w st (r : (a, b) Request.t) _ (errs : b) :
       unit tzresult Lwt.t =
     let open Lwt_result_syntax in
     let request_view = Request.view r in
@@ -415,7 +417,7 @@ module Handlers = struct
     in
     match r with Request.Frame _ -> emit_and_continue errs
 
-  let on_completion _w r _ st =
+  let on_completion _w r _ _ st =
     match Request.view r with
     | Request.View (Frame _) ->
         Event.(emit request_completed_debug) (Request.view r, st)
diff --git a/etherlink/bin_node/lib_dev/signals_publisher.ml b/etherlink/bin_node/lib_dev/signals_publisher.ml
index 6072d56c659bac54b8a01aa3cc06f4f5133d30e6..6674c18fd546ecc866f2eab08f9d443ea4060b99 100644
--- a/etherlink/bin_node/lib_dev/signals_publisher.ml
+++ b/etherlink/bin_node/lib_dev/signals_publisher.ml
@@ -179,9 +179,11 @@ module Handlers = struct
 
   let on_request :
       type r request_error.
-      worker -> (r, request_error) Request.t -> (r, request_error) result Lwt.t
-      =
-   fun w request ->
+      worker ->
+      (r, request_error) Request.t ->
+      Data_encoding.json option ->
+      (r, request_error) result Lwt.t =
+   fun w request _ ->
     match request with
     | New_rollup_node_block {finalized_level} ->
         protect @@ fun () -> Worker.new_rollup_block w finalized_level
@@ -191,11 +193,11 @@ module Handlers = struct
   let on_launch _w () (parameters : Types.parameters) =
     Types.of_parameters parameters
 
-  let on_error (type a b) _w _st (_r : (a, b) Request.t) (_errs : b) :
+  let on_error (type a b) _w _st (_r : (a, b) Request.t) _ (_errs : b) :
       unit tzresult Lwt.t =
     Lwt_result_syntax.return_unit
 
-  let on_completion _ _ _ _ = Lwt.return_unit
+  let on_completion _ _ _ _ _ = Lwt.return_unit
 
   let on_no_request _ = Lwt.return_unit
 
diff --git a/etherlink/bin_node/lib_dev/tx_pool.ml b/etherlink/bin_node/lib_dev/tx_pool.ml
index d2e922325248863e920a32d051604e74d49d0391..3e8ac69c8c6f0063709691e12b191005395a30dd 100644
--- a/etherlink/bin_node/lib_dev/tx_pool.ml
+++ b/etherlink/bin_node/lib_dev/tx_pool.ml
@@ -726,9 +726,11 @@ module Handlers = struct
 
   let on_request :
       type r request_error.
-      worker -> (r, request_error) Request.t -> (r, request_error) result Lwt.t
-      =
-   fun w request ->
+      worker ->
+      (r, request_error) Request.t ->
+      Data_encoding.json option ->
+      (r, request_error) result Lwt.t =
+   fun w request _ ->
     let open Lwt_result_syntax in
     let state = Worker.state w in
     match request with
@@ -790,11 +792,11 @@ module Handlers = struct
     in
     Lwt_result_syntax.return state
 
-  let on_error (type a b) _w _st (_r : (a, b) Request.t) (_errs : b) :
+  let on_error (type a b) _w _st (_r : (a, b) Request.t) _ (_errs : b) :
       unit tzresult Lwt.t =
     Lwt_result_syntax.return_unit
 
-  let on_completion _ _ _ _ = Lwt.return_unit
+  let on_completion _ _ _ _ _ = Lwt.return_unit
 
   let on_no_request _ = Lwt.return_unit
 
diff --git a/src/lib_injector/injector_functor.ml b/src/lib_injector/injector_functor.ml
index 630a39fcc9aa36ce221003d7eed13fd97cd81649..60826f893658eb79042e29ee38589cb8993f4c8d 100644
--- a/src/lib_injector/injector_functor.ml
+++ b/src/lib_injector/injector_functor.ml
@@ -1280,8 +1280,9 @@ module Make (Parameters : PARAMETERS) = struct
         type r request_error.
         worker ->
         (r, request_error) Request.t ->
+        Data_encoding.json option ->
         (r, request_error) result Lwt.t =
-     fun w request ->
+     fun w request _ ->
       let open Lwt_result_syntax in
       let state = Worker.state w in
       match request with
@@ -1326,7 +1327,7 @@ module Make (Parameters : PARAMETERS) = struct
            strategy
            tags
 
-    let on_error (type a b) w st (r : (a, b) Request.t) (errs : b) :
+    let on_error (type a b) w st (r : (a, b) Request.t) _ (errs : b) :
         unit tzresult Lwt.t =
       let open Lwt_result_syntax in
       let state = Worker.state w in
@@ -1340,7 +1341,7 @@ module Make (Parameters : PARAMETERS) = struct
       | Request.Inject -> emit_and_return_errors errs
       | Request.Clear _ -> emit_and_return_errors errs
 
-    let on_completion w r _ st =
+    let on_completion w r _ _ st =
       let state = Worker.state w in
       Event.(emit2 request_completed_debug) state (Request.view r) st
 
diff --git a/src/lib_shell/block_validator.ml b/src/lib_shell/block_validator.ml
index aaf5bac63d77b3c7b7c5251b66db384eb0912343..59f49796f3b704e02e137d7fcdd67d7c263081da 100644
--- a/src/lib_shell/block_validator.ml
+++ b/src/lib_shell/block_validator.ml
@@ -518,8 +518,11 @@ let metrics = Shell_metrics.Block_validator.init Name.base
 
 let on_request :
     type r request_error.
-    t -> (r, request_error) Request.t -> (r, request_error) result Lwt.t =
- fun w r ->
+    t ->
+    (r, request_error) Request.t ->
+    Data_encoding.json option ->
+    (r, request_error) result Lwt.t =
+ fun w r _ ->
   Prometheus.Counter.inc_one metrics.worker_counters.worker_request_count ;
   match r with
   | Request.Request_validation r ->
@@ -562,7 +565,7 @@ let on_launch _ _ (limits, start_testchain, db, validation_process) :
       inapplicable_blocks_after_validation;
     }
 
-let on_error (type a b) (_w : t) st (r : (a, b) Request.t) (errs : b) =
+let on_error (type a b) (_w : t) st (r : (a, b) Request.t) _ (errs : b) =
   let open Lwt_syntax in
   Prometheus.Counter.inc_one metrics.worker_counters.worker_error_count ;
   match r with
@@ -595,8 +598,13 @@ let check_and_quit_on_context_errors errors =
 
 let on_completion :
     type a b.
-    t -> (a, b) Request.t -> a -> Worker_types.request_status -> unit Lwt.t =
- fun _w request v st ->
+    t ->
+    (a, b) Request.t ->
+    Data_encoding.json option ->
+    a ->
+    Worker_types.request_status ->
+    unit Lwt.t =
+ fun _w request _ v st ->
   let open Lwt_syntax in
   Prometheus.Counter.inc_one metrics.worker_counters.worker_completion_count ;
   match (request, v) with
diff --git a/src/lib_shell/chain_validator.ml b/src/lib_shell/chain_validator.ml
index 2975a65e429795578166b606eab9e1683bb079e8..cc935f8087cb801b76370bdebaffd0b8efd11e52 100644
--- a/src/lib_shell/chain_validator.ml
+++ b/src/lib_shell/chain_validator.ml
@@ -603,7 +603,7 @@ let on_disconnection w peer_id =
           return_unit)
 
 let on_request (type a b) w start_testchain active_chains spawn_child
-    (req : (a, b) Request.t) : (a, b) result Lwt.t =
+    (req : (a, b) Request.t) _ : (a, b) result Lwt.t =
   let nv = Worker.state w in
   Prometheus.Counter.inc_one
     nv.parameters.metrics.worker_counters.worker_request_count ;
@@ -670,7 +670,7 @@ let collect_proto ~metrics (chain_store, block) =
           Lwt.return_unit)
         (fun _ -> Lwt.return_unit)
 
-let on_error (type a b) w st (request : (a, b) Request.t) (errs : b) :
+let on_error (type a b) w st (request : (a, b) Request.t) _ (errs : b) :
     unit tzresult Lwt.t =
   let open Lwt_result_syntax in
   let nv = Worker.state w in
@@ -705,7 +705,7 @@ let on_error (type a b) w st (request : (a, b) Request.t) (errs : b) :
   | Notify_head _ -> ( match errs with _ -> .)
   | Disconnection _ -> ( match errs with _ -> .)
 
-let on_completion (type a b) w (req : (a, b) Request.t) (update : a)
+let on_completion (type a b) w (req : (a, b) Request.t) _ (update : a)
     request_status =
   let open Lwt_syntax in
   let nv = Worker.state w in
diff --git a/src/lib_shell/peer_validator.ml b/src/lib_shell/peer_validator.ml
index eac665dbb06b0f642442e2aa74d4079669c9e97a..7c26f170237d3b144269f2acb29a83da714026f0 100644
--- a/src/lib_shell/peer_validator.ml
+++ b/src/lib_shell/peer_validator.ml
@@ -377,7 +377,7 @@ let on_no_request w =
     pv.peer_id ;
   Lwt.return_unit
 
-let on_request (type a b) w (req : (a, b) Request.t) : (a, b) result Lwt.t =
+let on_request (type a b) w (req : (a, b) Request.t) _ : (a, b) result Lwt.t =
   let open Lwt_syntax in
   let pv = Worker.state w in
   match req with
@@ -400,7 +400,7 @@ let on_request (type a b) w (req : (a, b) Request.t) : (a, b) result Lwt.t =
          locator [@profiler.span_s {verbosity = Notice} ["New branch"]])
 
 let on_completion (type a request_error) _w (r : (a, request_error) Request.t) _
-    st =
+    _ st =
   (match r with
   | Request.New_head _ -> Prometheus.Counter.inc_one metrics.new_head_completed
   | Request.New_branch _ ->
@@ -408,7 +408,7 @@ let on_completion (type a request_error) _w (r : (a, request_error) Request.t) _
 
   Events.(emit request_completed) (Request.view r, st)
 
-let on_error (type a b) w st (request : (a, b) Request.t) (err : b) :
+let on_error (type a b) w st (request : (a, b) Request.t) _ (err : b) :
     unit tzresult Lwt.t =
   let open Lwt_syntax in
   let pv = Worker.state w in
@@ -565,21 +565,21 @@ let on_launch _ name parameters : (_, launch_error) result Lwt.t =
   Lwt.return (Ok pv)
 
 let table =
-  let merge w (Worker.Any_request neu) old =
+  let merge w (Worker.Any_request (neu, metadata_neu)) old =
     let pv = Worker.state w in
     match neu with
     | Request.New_branch (locator, _) ->
         pv.last_advertised_head <- (locator.head_hash, locator.head_header) ;
-        Some (Worker.Any_request neu)
+        Some (Worker.Any_request (neu, metadata_neu))
     | Request.New_head (hash, header) -> (
         pv.last_advertised_head <- (hash, header) ;
         (* TODO penalize decreasing fitness *)
         match old with
-        | Some (Worker.Any_request (Request.New_branch _) as old) ->
+        | Some (Worker.Any_request (Request.New_branch _, _) as old) ->
             Some old (* ignore *)
-        | Some (Worker.Any_request (Request.New_head _)) ->
-            Some (Any_request neu)
-        | None -> Some (Any_request neu))
+        | Some (Worker.Any_request (Request.New_head _, _)) ->
+            Some (Any_request (neu, metadata_neu))
+        | None -> Some (Any_request (neu, metadata_neu)))
   in
   Worker.create_table (Dropbox {merge})
 
diff --git a/src/lib_shell/prevalidator.ml b/src/lib_shell/prevalidator.ml
index 4435c871f052faff62eb4f9e209614b9a0d24087..c4a14e8c2e7cb5c641a452a91b7bfc20c663a70d 100644
--- a/src/lib_shell/prevalidator.ml
+++ b/src/lib_shell/prevalidator.ml
@@ -1430,8 +1430,9 @@ module Make
         type r request_error.
         worker ->
         (r, request_error) Request.t ->
+        Data_encoding.json option ->
         (r, request_error) result Lwt.t =
-     fun w request ->
+     fun w request _ ->
       let open Lwt_result_syntax in
       Prometheus.Counter.inc_one metrics.worker_counters.worker_request_count ;
       let pv = Worker.state w in
@@ -1624,7 +1625,7 @@ module Make
         (Operation_hash.Set.to_seq fetching) ;
       return pv
 
-    let on_error (type a b) _w st (request : (a, b) Request.t) (errs : b) :
+    let on_error (type a b) _w st (request : (a, b) Request.t) _ (errs : b) :
         unit tzresult Lwt.t =
       Prometheus.Counter.inc_one metrics.worker_counters.worker_error_count ;
       let open Lwt_syntax in
@@ -1645,7 +1646,7 @@ module Make
           let* () = Events.(emit request_failed) (request_view, st, errs) in
           Lwt.return_error errs
 
-    let on_completion _w r _ st =
+    let on_completion _w r _ _ st =
       Prometheus.Counter.inc_one metrics.worker_counters.worker_completion_count ;
       match Request.view r with
       | View (Inject _) | View (Ban _) | Request.View (Flush _) ->
diff --git a/src/lib_smart_rollup_node/batcher.ml b/src/lib_smart_rollup_node/batcher.ml
index e34982682334e50e8693349533a625c2c5a9431a..a6c7206c5d410bc71c826ba791bb2c1816e8a883 100644
--- a/src/lib_smart_rollup_node/batcher.ml
+++ b/src/lib_smart_rollup_node/batcher.ml
@@ -298,9 +298,11 @@ module Handlers = struct
 
   let on_request :
       type r request_error.
-      worker -> (r, request_error) Request.t -> (r, request_error) result Lwt.t
-      =
-   fun w request ->
+      worker ->
+      (r, request_error) Request.t ->
+      Data_encoding.json option ->
+      (r, request_error) result Lwt.t =
+   fun w request _ ->
     let state = Worker.state w in
     match request with
     | Request.Register {order; messages; drop_duplicate} ->
@@ -322,7 +324,7 @@ module Handlers = struct
     let state = init_batcher_state plugin node_ctxt in
     return state
 
-  let on_error (type a b) _w st (r : (a, b) Request.t) (errs : b) :
+  let on_error (type a b) _w st (r : (a, b) Request.t) _ (errs : b) :
       unit tzresult Lwt.t =
     let open Lwt_result_syntax in
     let request_view = Request.view r in
@@ -338,7 +340,7 @@ module Handlers = struct
     | Request.Clear_queues -> emit_and_return_errors errs
     | Request.Remove_messages _ -> emit_and_return_errors errs
 
-  let on_completion _w r _ st =
+  let on_completion _w r _ _ st =
     match Request.view r with
     | Request.View
         (Register _ | Produce_batches | Clear_queues | Remove_messages _) ->
diff --git a/src/lib_smart_rollup_node/dal_injection_queue.ml b/src/lib_smart_rollup_node/dal_injection_queue.ml
index d6eb7896228ccb4bdd356010bddbb79edcc80bd6..248c65f0e76c2680522b68266e99120d7bfada80 100644
--- a/src/lib_smart_rollup_node/dal_injection_queue.ml
+++ b/src/lib_smart_rollup_node/dal_injection_queue.ml
@@ -483,9 +483,11 @@ module Handlers = struct
 
   let on_request :
       type r request_error.
-      worker -> (r, request_error) Request.t -> (r, request_error) result Lwt.t
-      =
-   fun w request ->
+      worker ->
+      (r, request_error) Request.t ->
+      Data_encoding.json option ->
+      (r, request_error) result Lwt.t =
+   fun w request _ ->
     let state = Worker.state w in
     match request with
     | Request.Register {message} ->
@@ -500,7 +502,7 @@ module Handlers = struct
   let on_launch _w () Types.{node_ctxt; dal_node_ctxt} =
     init_dal_worker_state node_ctxt dal_node_ctxt
 
-  let on_error (type a b) _w st (r : (a, b) Request.t) (errs : b) :
+  let on_error (type a b) _w st (r : (a, b) Request.t) _ (errs : b) :
       unit tzresult Lwt.t =
     let open Lwt_result_syntax in
     match r with
@@ -514,7 +516,7 @@ module Handlers = struct
         let*! () = Events.(emit request_failed) (Request.view r, st, errs) in
         return_unit
 
-  let on_completion _w r _ st =
+  let on_completion _w r _ _ st =
     match Request.view r with
     | Request.View (Register _ | Produce_dal_slots _ | Set_dal_slot_indices _)
       ->
diff --git a/src/lib_smart_rollup_node/publisher.ml b/src/lib_smart_rollup_node/publisher.ml
index b5ee32901af92b8a5bfc1bd8a8c4e60e4dde2ebc..a34e0e935ba5c84bf2dd072ba80d26b672da8082 100644
--- a/src/lib_smart_rollup_node/publisher.ml
+++ b/src/lib_smart_rollup_node/publisher.ml
@@ -610,9 +610,11 @@ module Handlers = struct
 
   let on_request :
       type r request_error.
-      worker -> (r, request_error) Request.t -> (r, request_error) result Lwt.t
-      =
-   fun w request ->
+      worker ->
+      (r, request_error) Request.t ->
+      Data_encoding.json option ->
+      (r, request_error) result Lwt.t =
+   fun w request _ ->
     let state = Worker.state w in
     match request with
     | Request.Publish -> protect @@ fun () -> on_publish_commitments state
@@ -623,7 +625,7 @@ module Handlers = struct
 
   let on_launch _w () Types.{node_ctxt} = Lwt_result.return node_ctxt
 
-  let on_error (type a b) _w st (r : (a, b) Request.t) (errs : b) :
+  let on_error (type a b) _w st (r : (a, b) Request.t) _ (errs : b) :
       unit tzresult Lwt.t =
     let open Lwt_result_syntax in
     let request_view = Request.view r in
@@ -638,7 +640,7 @@ module Handlers = struct
     | Request.Cement -> emit_and_return_errors errs
     | Request.Execute_outbox -> emit_and_return_errors errs
 
-  let on_completion _w r _ st =
+  let on_completion _w r _ _ st =
     Commitment_event.Publisher.request_completed (Request.view r) st
 
   let on_no_request _ = Lwt.return_unit
diff --git a/src/lib_smart_rollup_node/refutation_coordinator.ml b/src/lib_smart_rollup_node/refutation_coordinator.ml
index 1aacbb3ca00c4d873d998924c4b1c47b03f02339..ed813140460527b5433dbc673b11540f9dc410c3 100644
--- a/src/lib_smart_rollup_node/refutation_coordinator.ml
+++ b/src/lib_smart_rollup_node/refutation_coordinator.ml
@@ -155,9 +155,11 @@ module Handlers = struct
 
   let on_request :
       type r request_error.
-      worker -> (r, request_error) Request.t -> (r, request_error) result Lwt.t
-      =
-   fun w request ->
+      worker ->
+      (r, request_error) Request.t ->
+      Data_encoding.json option ->
+      (r, request_error) result Lwt.t =
+   fun w request _ ->
     let state = Worker.state w in
     match request with
     | Request.Process b -> protect @@ fun () -> on_process b state
@@ -167,7 +169,7 @@ module Handlers = struct
   let on_launch _w () node_ctxt =
     Lwt_result.return {node_ctxt; pending_opponents = Pkh_table.create 5}
 
-  let on_error (type a b) _w st (r : (a, b) Request.t) (errs : b) :
+  let on_error (type a b) _w st (r : (a, b) Request.t) _ (errs : b) :
       unit tzresult Lwt.t =
     let open Lwt_result_syntax in
     let request_view = Request.view r in
@@ -179,7 +181,7 @@ module Handlers = struct
     in
     match r with Request.Process _ -> emit_and_return_errors errs
 
-  let on_completion _w r _ st =
+  let on_completion _w r _ _ st =
     Refutation_game_event.Coordinator.request_completed (Request.view r) st
 
   let on_no_request _ = Lwt.return_unit
diff --git a/src/lib_smart_rollup_node/refutation_player.ml b/src/lib_smart_rollup_node/refutation_player.ml
index d3474672b0ddf2ada62ae4af24541717b74d082a..70a7860ccbe61b0020ef098e735a924c970ef703 100644
--- a/src/lib_smart_rollup_node/refutation_player.ml
+++ b/src/lib_smart_rollup_node/refutation_player.ml
@@ -71,9 +71,11 @@ module Handlers = struct
 
   let on_request :
       type r request_error.
-      worker -> (r, request_error) Request.t -> (r, request_error) result Lwt.t
-      =
-   fun w request ->
+      worker ->
+      (r, request_error) Request.t ->
+      Data_encoding.json option ->
+      (r, request_error) result Lwt.t =
+   fun w request _ ->
     let state = Worker.state w in
     match request with
     | Request.Play game -> protect @@ fun () -> on_play game state
@@ -102,7 +104,7 @@ module Handlers = struct
           last_move_cache = None;
         }
 
-  let on_error (type a b) _w st (r : (a, b) Request.t) (errs : b) :
+  let on_error (type a b) _w st (r : (a, b) Request.t) _ (errs : b) :
       unit tzresult Lwt.t =
     let open Lwt_result_syntax in
     let request_view = Request.view r in
@@ -116,7 +118,7 @@ module Handlers = struct
     | Request.Play _ -> emit_and_return_errors errs
     | Request.Play_opening _ -> emit_and_return_errors errs
 
-  let on_completion _w r _ st =
+  let on_completion _w r _ _ st =
     Refutation_game_event.Player.request_completed (Request.view r) st
 
   let on_no_request _ = Lwt.return_unit
diff --git a/src/lib_workers/test/test_workers_unit.ml b/src/lib_workers/test/test_workers_unit.ml
index 6850bfffc2bca975d8563e3431f7a0a24ad46b0d..360f2dcf143451cb16900f779529dc12aba711d5 100644
--- a/src/lib_workers/test/test_workers_unit.ml
+++ b/src/lib_workers/test/test_workers_unit.ml
@@ -45,9 +45,11 @@ let create_handlers (type a) ?on_completion () =
 
     let on_request :
         type r request_error.
-        self -> (r, request_error) Request.t -> (r, request_error) result Lwt.t
-        =
-     fun _w request ->
+        self ->
+        (r, request_error) Request.t ->
+        Data_encoding.json option ->
+        (r, request_error) result Lwt.t =
+     fun _w request _ ->
       let open Lwt_result_syntax in
       match request with
       | Request.RqA _i -> return_unit
@@ -62,7 +64,7 @@ let create_handlers (type a) ?on_completion () =
       let open Lwt_result_syntax in
       return (ref [])
 
-    let on_error (type a b) w _st (r : (a, b) Request.t) (errs : b) :
+    let on_error (type a b) w _st (r : (a, b) Request.t) _ (errs : b) :
         unit tzresult Lwt.t =
       let open Lwt_result_syntax in
       let history = Worker.state w in
@@ -76,7 +78,7 @@ let create_handlers (type a) ?on_completion () =
               history := "RqErr" :: !history ;
               return_unit)
 
-    let on_completion w r _ _st =
+    let on_completion w r _ _ _st =
       let open Lwt_syntax in
       let history = Worker.state w in
       let () =
@@ -112,16 +114,18 @@ let create_bounded ?on_completion =
 let create_dropbox ?on_completion =
   let table =
     let open Worker in
-    let merge _w (Any_request neu) (old : _ option) =
-      let (Any_request r) =
+    let merge _w (Any_request (neu, neu_metadata)) (old : _ option) =
+      let (Any_request (r, metadata)) =
         match (neu, old) with
-        | RqA i1, Some (Any_request (RqA i2)) -> Any_request (RqA (i1 + i2))
-        | (RqA _ as rqa), _ -> Any_request rqa
-        | _, Some (Any_request (RqA _ as rqa)) -> Any_request rqa
-        | RqB, _ -> Any_request neu
-        | RqErr _, _ -> Any_request neu
+        | RqA i1, Some (Any_request (RqA i2, _)) ->
+            Any_request (RqA (i1 + i2), neu_metadata)
+        | (RqA _ as rqa), _ -> Any_request (rqa, neu_metadata)
+        | _, Some (Any_request ((RqA _ as rqa), metadata)) ->
+            Any_request (rqa, metadata)
+        | RqB, _ -> Any_request (neu, neu_metadata)
+        | RqErr _, _ -> Any_request (neu, neu_metadata)
       in
-      Some (Worker.Any_request r)
+      Some (Worker.Any_request (r, metadata))
     in
     Worker.create_table (Dropbox {merge})
   in
diff --git a/src/lib_workers/worker.ml b/src/lib_workers/worker.ml
index ecc05caff66e94031ebb9d5349178696397004dd..7e3c3b6b27eb68c4d771c23e285e3322dc500911 100644
--- a/src/lib_workers/worker.ml
+++ b/src/lib_workers/worker.ml
@@ -56,6 +56,8 @@ module type T = sig
     | Request_error of 'a
     | Any of exn
 
+  type metadata = Data_encoding.json
+
   (** Supported kinds of internal buffers. *)
   type _ buffer_kind =
     | Queue : infinite queue buffer_kind
@@ -66,7 +68,7 @@ module type T = sig
       }
         -> dropbox buffer_kind
 
-  and any_request = Any_request : _ Request.t -> any_request
+  and any_request = Any_request : _ Request.t * metadata option -> any_request
 
   (** Create a table of workers. *)
   val create_table : 'kind buffer_kind -> 'kind table
@@ -92,6 +94,7 @@ module type T = sig
     val on_request :
       self ->
       ('a, 'request_error) Request.t ->
+      metadata option ->
       ('a, 'request_error) result Lwt.t
 
     (** Called when no request has been made before the timeout, if
@@ -111,6 +114,7 @@ module type T = sig
       self ->
       Worker_types.request_status ->
       ('a, 'request_error) Request.t ->
+      metadata option ->
       'request_error ->
       unit tzresult Lwt.t
 
@@ -119,6 +123,7 @@ module type T = sig
     val on_completion :
       self ->
       ('a, 'request_error) Request.t ->
+      metadata option ->
       'a ->
       Worker_types.request_status ->
       unit Lwt.t
@@ -143,9 +148,11 @@ module type T = sig
   module type BOX = sig
     type t
 
-    val put_request : t -> ('a, 'request_error) Request.t -> unit
+    val put_request :
+      ?metadata:metadata -> t -> ('a, 'request_error) Request.t -> unit
 
     val put_request_and_wait :
+      ?metadata:metadata ->
       t ->
       ('a, 'request_error) Request.t ->
       ('a, 'request_error message_error) result Lwt.t
@@ -155,11 +162,13 @@ module type T = sig
     type 'a t
 
     val push_request_and_wait :
+      ?metadata:metadata ->
       'q t ->
       ('a, 'request_error) Request.t ->
       ('a, 'request_error message_error) result Lwt.t
 
-    val push_request : 'q t -> ('a, 'request_error) Request.t -> bool Lwt.t
+    val push_request :
+      ?metadata:metadata -> 'q t -> ('a, 'request_error) Request.t -> bool Lwt.t
 
     val pending_requests : 'a t -> (Time.System.t * Request.view) list
 
@@ -175,7 +184,10 @@ module type T = sig
 
     (** Adds a message to the queue immediately. *)
     val push_request_now :
-      infinite queue t -> ('a, 'request_error) Request.t -> unit
+      ?metadata:metadata ->
+      infinite queue t ->
+      ('a, 'request_error) Request.t ->
+      unit
   end
 
   (** Exports the canceler to allow cancellation of other tasks when this
@@ -247,9 +259,13 @@ struct
     | Request_error of 'a
     | Any of exn
 
+  type metadata = Data_encoding.json
+
   type message =
     | Message :
-        ('a, 'b) Request.t * ('a, 'b message_error) result Lwt.u option
+        ('a, 'b) Request.t
+        * metadata option
+        * ('a, 'b message_error) result Lwt.u option
         -> message
 
   type 'a queue
@@ -269,7 +285,7 @@ struct
       }
         -> dropbox buffer_kind
 
-  and any_request = Any_request : _ Request.t -> any_request
+  and any_request = Any_request : _ Request.t * metadata option -> any_request
 
   and _ buffer =
     | Queue_buffer :
@@ -306,27 +322,32 @@ struct
     | Worker_types.Launching _ | Running _ | Closing _ -> None
     | Closed (_, _, errs) -> errs
 
-  let queue_item ?u r = (Time.System.now (), Message (r, u))
+  let queue_item ?u metadata r = (Time.System.now (), Message (r, metadata, u))
 
-  let drop_request w merge message_box request =
+  let drop_request ?metadata w merge message_box request =
     try
       match
         match Lwt_dropbox.peek message_box with
-        | None -> merge w (Any_request request) None
-        | Some (_, Message (old, _)) ->
+        | None -> merge w (Any_request (request, metadata)) None
+        | Some (_, Message (old, metadata_old, _)) ->
             Lwt.ignore_result (Lwt_dropbox.take message_box) ;
-            merge w (Any_request request) (Some (Any_request old))
+            merge
+              w
+              (Any_request (request, metadata))
+              (Some (Any_request (old, metadata_old)))
       with
       | None -> ()
-      | Some (Any_request neu) ->
-          Lwt_dropbox.put message_box (Time.System.now (), Message (neu, None))
+      | Some (Any_request (neu, metadata)) ->
+          Lwt_dropbox.put
+            message_box
+            (Time.System.now (), Message (neu, metadata, None))
     with Lwt_dropbox.Closed -> ()
 
-  let drop_request_and_wait w message_box request =
+  let drop_request_and_wait ?metadata w message_box request =
     let t, u = Lwt.wait () in
     Lwt.catch
       (fun () ->
-        Lwt_dropbox.put message_box (queue_item ~u request) ;
+        Lwt_dropbox.put message_box (queue_item metadata ~u request) ;
         t)
       (function
         | Lwt_dropbox.Closed ->
@@ -338,9 +359,11 @@ struct
   module type BOX = sig
     type t
 
-    val put_request : t -> ('a, 'request_error) Request.t -> unit
+    val put_request :
+      ?metadata:metadata -> t -> ('a, 'request_error) Request.t -> unit
 
     val put_request_and_wait :
+      ?metadata:metadata ->
       t ->
       ('a, 'request_error) Request.t ->
       ('a, 'request_error message_error) result Lwt.t
@@ -350,11 +373,13 @@ struct
     type 'a t
 
     val push_request_and_wait :
+      ?metadata:metadata ->
       'q t ->
       ('a, 'request_error) Request.t ->
       ('a, 'request_error message_error) result Lwt.t
 
-    val push_request : 'q t -> ('a, 'request_error) Request.t -> bool Lwt.t
+    val push_request :
+      ?metadata:metadata -> 'q t -> ('a, 'request_error) Request.t -> bool Lwt.t
 
     val pending_requests : 'a t -> (Time.System.t * Request.view) list
 
@@ -362,23 +387,23 @@ struct
   end
 
   module Dropbox = struct
-    let put_request (w : dropbox t) request =
+    let put_request ?metadata (w : dropbox t) request =
       let (Dropbox {merge}) = w.table.buffer_kind in
       let (Dropbox_buffer message_box) = w.buffer in
-      drop_request w merge message_box request
+      drop_request ?metadata w merge message_box request
 
-    let put_request_and_wait (w : dropbox t) request =
+    let put_request_and_wait ?metadata (w : dropbox t) request =
       let (Dropbox_buffer message_box) = w.buffer in
-      drop_request_and_wait w message_box request
+      drop_request_and_wait ?metadata w message_box request
   end
 
   module Queue = struct
-    let push_request (type a) (w : a queue t) request =
+    let push_request ?metadata (type a) (w : a queue t) request =
       match w.buffer with
       | Queue_buffer message_queue ->
           if Lwt_pipe.Unbounded.is_closed message_queue then Lwt.return_false
           else (
-            Lwt_pipe.Unbounded.push message_queue (queue_item request) ;
+            Lwt_pipe.Unbounded.push message_queue (queue_item metadata request) ;
             (* because pushing on an unbounded pipe is immediate, we return within
                Lwt explicitly for compatibility with the other case *)
             Lwt.return_true)
@@ -387,21 +412,23 @@ struct
           else
             let open Lwt_syntax in
             let* () =
-              Lwt_pipe.Bounded.push message_queue (queue_item request)
+              Lwt_pipe.Bounded.push message_queue (queue_item metadata request)
             in
             Lwt.return_true
 
-    let push_request_now (w : infinite queue t) request =
+    let push_request_now ?metadata (w : infinite queue t) request =
       let (Queue_buffer message_queue) = w.buffer in
       if Lwt_pipe.Unbounded.is_closed message_queue then ()
-      else Lwt_pipe.Unbounded.push message_queue (queue_item request)
+      else Lwt_pipe.Unbounded.push message_queue (queue_item metadata request)
 
-    let push_request_and_wait (type a) (w : a queue t) request =
+    let push_request_and_wait ?metadata (type a) (w : a queue t) request =
       match w.buffer with
       | Queue_buffer message_queue -> (
           try
             let t, u = Lwt.wait () in
-            Lwt_pipe.Unbounded.push message_queue (queue_item ~u request) ;
+            Lwt_pipe.Unbounded.push
+              message_queue
+              (queue_item ~u metadata request) ;
             t
           with Lwt_pipe.Closed ->
             Lwt.return_error (Closed (extract_status_errors w)))
@@ -409,7 +436,9 @@ struct
           let t, u = Lwt.wait () in
           Lwt.try_bind
             (fun () ->
-              Lwt_pipe.Bounded.push message_queue (queue_item ~u request))
+              Lwt_pipe.Bounded.push
+                message_queue
+                (queue_item ~u metadata request))
             (fun () -> t)
             (function
               | Lwt_pipe.Closed ->
@@ -426,7 +455,9 @@ struct
               Lwt_pipe.Bounded.peek_all_now message_queue
         with Lwt_pipe.Closed -> []
       in
-      List.map (function t, Message (req, _) -> (t, Request.view req)) peeked
+      List.map
+        (function t, Message (req, _, _) -> (t, Request.view req))
+        peeked
 
     let pending_requests_length (type a) (w : a queue t) =
       let pipe_length (type a) (q : a buffer) =
@@ -440,9 +471,9 @@ struct
 
   let close (type a) (w : a t) =
     let wakeup = function
-      | _, Message (_, Some u) ->
+      | _, Message (_, _, Some u) ->
           Lwt.wakeup_later u (Error (Closed (extract_status_errors w)))
-      | _, Message (_, None) -> ()
+      | _, Message (_, _, None) -> ()
     in
     let close_queue message_queue =
       let messages = Lwt_pipe.Bounded.pop_all_now message_queue in
@@ -514,6 +545,7 @@ struct
     val on_request :
       self ->
       ('a, 'request_error) Request.t ->
+      metadata option ->
       ('a, 'request_error) result Lwt.t
 
     val on_no_request : self -> unit Lwt.t
@@ -524,12 +556,14 @@ struct
       self ->
       Worker_types.request_status ->
       ('a, 'request_error) Request.t ->
+      metadata option ->
       'request_error ->
       unit tzresult Lwt.t
 
     val on_completion :
       self ->
       ('a, 'request_error) Request.t ->
+      metadata option ->
       'a ->
       Worker_types.request_status ->
       unit Lwt.t
@@ -579,7 +613,7 @@ struct
       | Ok None ->
           let* () = Handlers.on_no_request w in
           loop ()
-      | Ok (Some (pushed, Message (request, u))) -> (
+      | Ok (Some (pushed, Message (request, metadata, u))) -> (
           let current_request = Request.view request in
           let treated = Time.System.now () in
           w.current_request <- Some (pushed, treated, current_request) ;
@@ -587,14 +621,16 @@ struct
             match u with
             | None -> (
                 let open Lwt_result_syntax in
-                let*! res = Handlers.on_request w request in
+                let*! res = Handlers.on_request w request metadata in
                 match res with
                 | Error err -> Lwt.return_error err
                 | Ok res ->
                     let completed = Time.System.now () in
                     w.current_request <- None ;
                     let status = Worker_types.{pushed; treated; completed} in
-                    let*! () = Handlers.on_completion w request res status in
+                    let*! () =
+                      Handlers.on_completion w request metadata res status
+                    in
                     let*! () =
                       Worker_events.(emit request_no_errors)
                         (current_request, status)
@@ -606,7 +642,7 @@ struct
                    (Error). To that end, we treat it locally like a regular
                    promise (which happens to carry a [result]) within the Lwt
                    monad. *)
-                let* res = Handlers.on_request w request in
+                let* res = Handlers.on_request w request metadata in
                 match res with
                 | Error err ->
                     Lwt.wakeup_later u (Error (Request_error err)) ;
@@ -616,7 +652,9 @@ struct
                     let completed = Time.System.now () in
                     let status = Worker_types.{pushed; treated; completed} in
                     w.current_request <- None ;
-                    let* () = Handlers.on_completion w request res status in
+                    let* () =
+                      Handlers.on_completion w request metadata res status
+                    in
                     let* () =
                       Worker_events.(emit request_no_errors)
                         (current_request, status)
@@ -635,6 +673,7 @@ struct
                       w
                       Worker_types.{pushed; treated; completed}
                       request
+                      metadata
                       err
                 | None -> assert false
               in
diff --git a/src/lib_workers/worker.mli b/src/lib_workers/worker.mli
index 9f28073b99bf3aa1aa405cb94af00d46b7847b4a..6dafd21d37bdea26b1d3cc770f2fc48a944abeb1 100644
--- a/src/lib_workers/worker.mli
+++ b/src/lib_workers/worker.mli
@@ -67,6 +67,8 @@ module type T = sig
     | Request_error of 'a
     | Any of exn
 
+  type metadata = Data_encoding.json
+
   (** Supported kinds of internal buffers. *)
   type _ buffer_kind =
     | Queue : infinite queue buffer_kind
@@ -77,7 +79,7 @@ module type T = sig
       }
         -> dropbox buffer_kind
 
-  and any_request = Any_request : _ Request.t -> any_request
+  and any_request = Any_request : _ Request.t * metadata option -> any_request
 
   (** Create a table of workers. *)
   val create_table : 'kind buffer_kind -> 'kind table
@@ -104,6 +106,7 @@ module type T = sig
     val on_request :
       self ->
       ('a, 'request_error) Request.t ->
+      metadata option ->
       ('a, 'request_error) result Lwt.t
 
     (** Called when no request has been made before the timeout, if
@@ -121,6 +124,7 @@ module type T = sig
       self ->
       Worker_types.request_status ->
       ('a, 'request_error) Request.t ->
+      metadata option ->
       'request_error ->
       unit tzresult Lwt.t
 
@@ -129,6 +133,7 @@ module type T = sig
     val on_completion :
       self ->
       ('a, 'request_error) Request.t ->
+      metadata option ->
       'a ->
       Worker_types.request_status ->
       unit Lwt.t
@@ -158,12 +163,14 @@ module type T = sig
 
     (** [put_request worker request] sends the [request] to the [worker]. If the
         [worker] dropbox is closed, then it is a no-op. *)
-    val put_request : t -> ('a, 'request_error) Request.t -> unit
+    val put_request :
+      ?metadata:metadata -> t -> ('a, 'request_error) Request.t -> unit
 
     (** [put_request_and_wait worker request] sends the [request] to the
         [worker] and waits for its completion. If the worker dropbox is closed,
         then it returns [Error Closed]. *)
     val put_request_and_wait :
+      ?metadata:metadata ->
       t ->
       ('a, 'request_error) Request.t ->
       ('a, 'request_error message_error) result Lwt.t
@@ -178,6 +185,7 @@ module type T = sig
         then it returns [Error Closed]. If the buffer is a bounded queue and the
         underlying queue is full, the call is blocking. *)
     val push_request_and_wait :
+      ?metadata:metadata ->
       'q t ->
       ('a, 'request_error) Request.t ->
       ('a, 'request_error message_error) result Lwt.t
@@ -186,7 +194,8 @@ module type T = sig
         promise returned is [true] if the request was pushed successfuly or
         [false] if the worker queue is closed. If the buffer is a bounded queue
         and the underlying queue is full, the call is blocking. *)
-    val push_request : 'q t -> ('a, 'request_error) Request.t -> bool Lwt.t
+    val push_request :
+      ?metadata:metadata -> 'q t -> ('a, 'request_error) Request.t -> bool Lwt.t
 
     val pending_requests : 'a t -> (Time.System.t * Request.view) list
 
@@ -202,7 +211,10 @@ module type T = sig
 
     (** Adds a message to the queue immediately. *)
     val push_request_now :
-      infinite queue t -> ('a, 'request_error) Request.t -> unit
+      ?metadata:metadata ->
+      infinite queue t ->
+      ('a, 'request_error) Request.t ->
+      unit
   end
 
   (** Exports the canceler to allow cancellation of other tasks when this