diff --git a/src/client/embedded/alpha/client_proto_context.ml b/src/client/embedded/alpha/client_proto_context.ml
index 2dfeb0c56..bfe53f798 100644
--- a/src/client/embedded/alpha/client_proto_context.ml
+++ b/src/client/embedded/alpha/client_proto_context.ml
@@ -128,7 +128,7 @@ let originate_contract cctxt
     ~source ~src_pk ~src_sk ~manager_pkh ~balance ?delegatable ?delegatePubKey
     ~(code:Script.code) ~init ~fee () =
   Client_proto_programs.parse_data cctxt init >>= fun storage ->
-  let init = Script.{ storage ; storage_type = code.storage_type } in
+  let storage = Script.{ storage ; storage_type = code.storage_type } in
   Client_proto_rpcs.Context.Contract.counter cctxt block source >>=? fun pcounter ->
   let counter = Int32.succ pcounter in
   cctxt.message "Acquired the source's sequence counter (%ld -> %ld)."
@@ -138,7 +138,7 @@ let originate_contract cctxt
     ~net ~source ~sourcePubKey:src_pk ~managerPubKey:manager_pkh
     ~counter ~balance ~spendable:!spendable
     ?delegatable ?delegatePubKey
-    ~script:(code, init) ~fee () >>=? fun bytes ->
+    ~script:{ code ; storage } ~fee () >>=? fun bytes ->
   let signature = Ed25519.sign src_sk bytes in
   originate cctxt ?force ~block ~signature bytes
 
diff --git a/src/client/embedded/alpha/client_proto_programs.ml b/src/client/embedded/alpha/client_proto_programs.ml
index bba0d4cd6..b0fa25880 100644
--- a/src/client/embedded/alpha/client_proto_programs.ml
+++ b/src/client/embedded/alpha/client_proto_programs.ml
@@ -471,7 +471,7 @@ let parse_data_type cctxt s =
   with
   | exn -> report_parse_error cctxt "data_type: " exn lexbuf
 
-let unexpand_macros type_map program =
+let unexpand_macros type_map (program : Script.code) =
   let open Script in
   let rec caddr type_map acc = function
     | [] -> Some (List.rev acc)
diff --git a/src/client/embedded/alpha/client_proto_rpcs.ml b/src/client/embedded/alpha/client_proto_rpcs.ml
index fb052ecf7..bfed11df1 100644
--- a/src/client/embedded/alpha/client_proto_rpcs.ml
+++ b/src/client/embedded/alpha/client_proto_rpcs.ml
@@ -108,7 +108,7 @@ module Context = struct
       balance: Tez.t ;
       spendable: bool ;
       delegate: bool * public_key_hash option ;
-      script: Script.t ;
+      script: Script.t option ;
       assets: Asset.Map.t ;
       counter: int32 ;
     }
@@ -180,10 +180,6 @@ module Helpers = struct
 
   module Forge = struct
 
-    let script_of_option = function
-      | None -> Script.No_script
-      | Some (code, storage) -> Script { code ; storage }
-
     open Operation
 
     module Manager = struct
@@ -206,7 +202,6 @@ module Helpers = struct
           ?(spendable = true)
           ?(delegatable = true)
           ?delegatePubKey ?script ~fee () =
-        let script = script_of_option script in
         operations cctxt block ~net ~source ?sourcePubKey ~counter ~fee
           Tezos_context.[
             Origination { manager = managerPubKey ;
diff --git a/src/client/embedded/alpha/client_proto_rpcs.mli b/src/client/embedded/alpha/client_proto_rpcs.mli
index d8db09f7b..3013e592c 100644
--- a/src/client/embedded/alpha/client_proto_rpcs.mli
+++ b/src/client/embedded/alpha/client_proto_rpcs.mli
@@ -91,7 +91,7 @@ module Context : sig
       balance: Tez.t ;
       spendable: bool ;
       delegate: bool * public_key_hash option ;
-      script: Script.t ;
+      script: Script.t option ;
       assets: Asset.Map.t ;
       counter: int32 ;
     }
@@ -124,7 +124,7 @@ module Context : sig
       bool tzresult Lwt.t
     val script:
       Client_commands.context ->
-      block -> Contract.t -> Script.t tzresult Lwt.t
+      block -> Contract.t -> Script.t option tzresult Lwt.t
     val assets:
       Client_commands.context ->
       block -> Contract.t ->
@@ -222,7 +222,7 @@ module Helpers : sig
         ?spendable:bool ->
         ?delegatable:bool ->
         ?delegatePubKey: public_key_hash ->
-        ?script:(Script.code * Script.storage) ->
+        ?script:Script.t ->
         fee:Tez.t->
         unit ->
         MBytes.t tzresult Lwt.t
diff --git a/src/proto/alpha/apply.ml b/src/proto/alpha/apply.ml
index 85efbbc80..6f1dbf15a 100644
--- a/src/proto/alpha/apply.ml
+++ b/src/proto/alpha/apply.ml
@@ -12,7 +12,6 @@
 open Tezos_context
 
 type error += Bad_endorsement (* TODO: doc *)
-type error += Insert_coin (* TODO: doc *)
 type error += Contract_not_delegatable (* TODO: doc *)
 type error += Unimplemented
 type error += Invalid_voting_period
@@ -53,13 +52,13 @@ let apply_manager_operation_content ctxt origination_nonce accept_failing_script
       Contract.spend ctxt source amount >>=? fun ctxt ->
       Contract.credit ctxt destination amount >>=? fun ctxt ->
       Contract.get_script ctxt destination >>=? function
-      | No_script -> begin
+      | None -> begin
           match parameters with
           | None | Some (Prim (_, "Unit", [])) ->
               return (ctxt, origination_nonce)
           | Some _ -> fail Non_scripted_contract_with_parameter
         end
-      | Script { code ; storage } ->
+      | Some { code ; storage } ->
           match parameters with
           | None -> fail Scripted_contract_without_paramater
           | Some parameters ->
@@ -71,8 +70,9 @@ let apply_manager_operation_content ctxt origination_nonce accept_failing_script
               | Ok (storage_res, _res, _steps, ctxt, origination_nonce) ->
                   (* TODO: pay for the steps and the storage diff:
                      update_script_storage checks the storage cost *)
-                  Contract.update_script_storage
-                    ctxt destination storage_res >>=? fun ctxt ->
+                  Contract.update_script_storage_and_fees
+                    ctxt destination
+                    Script_interpreter.dummy_storage_fee storage_res >>=? fun ctxt ->
                   return (ctxt, origination_nonce)
               | Error err ->
                   if accept_failing_script && is_reject err then
@@ -81,24 +81,18 @@ let apply_manager_operation_content ctxt origination_nonce accept_failing_script
                     Lwt.return (Error err)
     end
   | Origination { manager ; delegate ; script ;
-                  spendable ; delegatable ; credit } -> begin
-      match script with
-      | No_script -> return ()
-      | Script { code ; storage } ->
-          Script_ir_translator.parse_script ctxt storage code >>=? fun _ ->
-          let storage_fee = Script.storage_cost storage in
-          let code_fee = Script.code_cost code in
-          Lwt.return Tez.(code_fee +? storage_fee) >>=? fun script_fee ->
-          Lwt.return Tez.(script_fee +? Constants.origination_burn) >>=? fun total_fee ->
-          fail_unless Tez.(credit > total_fee) Insert_coin >>=? fun () ->
-          return ()
-    end >>=? fun () ->
+                  spendable ; delegatable ; credit } ->
+      let script = match script with
+        | None -> None
+        | Some script ->
+            Some (script, (Script_interpreter.dummy_code_fee, Script_interpreter.dummy_storage_fee)) in
       Contract.spend ctxt source credit >>=? fun ctxt ->
       Lwt.return Tez.(credit -? Constants.origination_burn) >>=? fun balance ->
       Contract.originate ctxt
         origination_nonce
         ~manager ~delegate ~balance
-        ~script ~spendable ~delegatable >>=? fun (ctxt, _, origination_nonce) ->
+        ?script
+        ~spendable ~delegatable >>=? fun (ctxt, _, origination_nonce) ->
       return (ctxt, origination_nonce)
   | Issuance { asset = (asset, key); amount } ->
       Contract.issue ctxt source asset key amount >>=? fun ctxt ->
@@ -127,6 +121,7 @@ let apply_sourced_operation
     operation origination_nonce ops =
   match ops with
   | Manager_operations { source ; public_key ; fee ; counter ; operations = contents } ->
+      Contract.must_exist ctxt source >>=? fun () ->
       Contract.get_manager ctxt source >>=? fun manager ->
       check_signature_and_update_public_key
         ctxt manager public_key operation >>=? fun ctxt ->
@@ -139,6 +134,7 @@ let apply_sourced_operation
        | Some contract ->
            Contract.credit ctxt contract fee) >>=? fun ctxt ->
       fold_left_s (fun (ctxt, origination_nonce) content ->
+          Contract.must_exist ctxt source >>=? fun () ->
           apply_manager_operation_content ctxt origination_nonce
             accept_failing_script source content)
         (ctxt, origination_nonce) contents
@@ -190,7 +186,7 @@ let apply_anonymous_operation ctxt miner_contract origination_nonce kind =
       end >>=? fun delegate ->
       Contract.originate ctxt
         origination_nonce
-        ~manager ~delegate ~balance:Constants.faucet_credit ~script:No_script
+        ~manager ~delegate ~balance:Constants.faucet_credit ?script:None
         ~spendable:true ~delegatable:true >>=? fun (ctxt, _, origination_nonce) ->
       return (ctxt, origination_nonce)
 
diff --git a/src/proto/alpha/contract_repr.ml b/src/proto/alpha/contract_repr.ml
index 52b4f4c06..573a25116 100644
--- a/src/proto/alpha/contract_repr.ml
+++ b/src/proto/alpha/contract_repr.ml
@@ -14,7 +14,7 @@ type t =
   | Originated of Contract_hash.t
 type contract = t
 
-type error += Invalid_contract_notation of string
+type error += Invalid_contract_notation of string (* `Permanent *)
 
 let to_b58check = function
   | Default pbk -> Ed25519.Public_key_hash.to_b58check pbk
@@ -26,17 +26,23 @@ let of_b58check s =
   | Some (Contract_hash.Hash h) -> ok (Originated h)
   | _ -> error (Invalid_contract_notation s)
 
+let pp ppf = function
+  | Default pbk -> Ed25519.Public_key_hash.pp ppf pbk
+  | Originated h -> Contract_hash.pp ppf h
+
+let pp_short ppf = function
+  | Default pbk -> Ed25519.Public_key_hash.pp_short ppf pbk
+  | Originated h -> Contract_hash.pp_short ppf h
+
 let encoding =
   let open Data_encoding in
   describe
     ~title:
       "A contract handle"
     ~description:
-      "A contract notation as given to a RPC or inside scripts. \
-       Contract handles can be written 'd<base64 encoded ID>d' \
-       for the default contract of some ID (public key hash) or \
-       'h<base64 encoded contract ID>h' for a created contract or account, \
-       as replied by the contract origination RPC." @@
+      "A contract notation as given to an RPC or inside scripts. \
+       Can be a base58 public key hash, representing the default contract \
+       of this identity, or a base58 originated contract hash." @@
   splitted
     ~binary:
       (union ~tag_size:`Uint8 [
@@ -60,14 +66,11 @@ let () =
   let open Data_encoding in
   register_error_kind
     `Permanent
-    ~id:"InvalidContractNotationError"
+    ~id:"contract.invalid_contract_notation"
     ~title: "Invalid contract notation"
+    ~pp: (fun ppf x -> Format.fprintf ppf "Invalid contract notation %S" x)
     ~description:
-      "A malformed contract notation was given to a RPC or by a script. \
-       Contract handles can be written 'd<base encoded ID>d' \
-       for the default contract of some ID (public key hash) or \
-       'h<base encoded contract ID>h' for a created contract or account, \
-       as replied by the contract origination RPC."
+      "A malformed contract notation was given to an RPC or in a script."
     (obj1 (req "notation" string))
     (function Invalid_contract_notation loc -> Some loc | _ -> None)
     (fun loc -> Invalid_contract_notation loc)
@@ -78,7 +81,6 @@ let is_default = function
   | Default m -> Some m
   | Originated _ -> None
 
-
 type origination_nonce =
   { operation_hash: Operation_hash.t ;
     origination_index: int32 }
diff --git a/src/proto/alpha/contract_repr.mli b/src/proto/alpha/contract_repr.mli
index 2d43688c9..39e285091 100644
--- a/src/proto/alpha/contract_repr.mli
+++ b/src/proto/alpha/contract_repr.mli
@@ -16,27 +16,42 @@ type contract = t
 
 include Compare.S with type t := contract
 
+(** {2 Default contracts} *****************************************************)
+
 val default_contract : Ed25519.Public_key_hash.t -> contract
 
 val is_default : contract -> Ed25519.Public_key_hash.t option
 
+(** {2 Originated contracts} **************************************************)
+
+(** Originated contracts handles are crafted from the hash of the
+    operation that triggered their origination (and nothing else).
+    As a single operation can trigger several originations, the
+    corresponding handles are forged from a deterministic sequence of
+    nonces, initialized with the hash of the operation. *)
 type origination_nonce
 
 val originated_contract : origination_nonce -> contract
+
 val originated_contracts : origination_nonce -> contract list
 
 val initial_origination_nonce : Operation_hash.t -> origination_nonce
+
 val incr_origination_nonce : origination_nonce -> origination_nonce
 
 
 (** {2 Human readable notation} ***********************************************)
 
-type error += Invalid_contract_notation of string
+type error += Invalid_contract_notation of string (* `Permanent *)
 
 val to_b58check: contract -> string
 
 val of_b58check: string -> contract tzresult
 
+val pp: Format.formatter -> contract -> unit
+
+val pp_short: Format.formatter -> contract -> unit
+
 (** {2 Serializers} ***********************************************************)
 
 val encoding : contract Data_encoding.t
diff --git a/src/proto/alpha/contract_storage.ml b/src/proto/alpha/contract_storage.ml
index 90ba0ee9d..ffd84dd74 100644
--- a/src/proto/alpha/contract_storage.ml
+++ b/src/proto/alpha/contract_storage.ml
@@ -8,64 +8,71 @@
 (**************************************************************************)
 
 type error +=
-  | Balance_too_low of Contract_repr.contract * Tez_repr.t * Tez_repr.t
-  | Initial_amount_too_low of Tez_repr.t * Tez_repr.t
-  | Counter_in_the_past of Contract_repr.contract * int32 * int32
-  | Counter_in_the_future of Contract_repr.contract * int32 * int32
-  | Unspendable_contract of Contract_repr.contract
-  | Non_existing_contract (* TODO: DOC *)
-  | No_delegate (* TODO: DOC *)
-  | Undelagatable_contract (* TODO: DOC *)
-  | Failure of string
+  | Initial_amount_too_low of Contract_repr.contract * Tez_repr.t * Tez_repr.t (* `Permanent *)
+  | Balance_too_low of Contract_repr.contract * Tez_repr.t * Tez_repr.t (* `Temporary *)
+  | Cannot_pay_storage_fee of Contract_repr.contract * Tez_repr.t * Tez_repr.t (* `Temporary *)
+  | Counter_in_the_past of Contract_repr.contract * int32 * int32 (* `Branch *)
+  | Counter_in_the_future of Contract_repr.contract * int32 * int32 (* `Temporary *)
+  | Unspendable_contract of Contract_repr.contract (* `Permanent *)
+  | Non_existing_contract of Contract_repr.contract (* `Temporary *)
+  | Undelagatable_contract of Contract_repr.contract (* `Permanent *)
+  | Failure of string (* `Permanent *)
 
 let () =
-  register_error_kind
-    `Permanent
-    ~id:"contract.failure"
-    ~title:"Contract storage failure"
-    ~description:"Unexpected contract storage error"
-    ~pp:(fun ppf s -> Format.fprintf ppf "Contract_storage.Failure %S" s)
-    Data_encoding.(obj1 (req "message" string))
-    (function Failure s -> Some s | _ -> None)
-    (fun s -> Failure s) ;
   register_error_kind
     `Permanent
     ~id:"contract.initial_amount_too_low"
     ~title:"Initial amount too low"
     ~description:"Not enough tokens provided for an origination"
-    ~pp:(fun ppf (r, p) ->
-        Format.fprintf ppf "Initial amount too low (required %a but provided %a)"
+    ~pp:(fun ppf (c, r, p) ->
+        Format.fprintf ppf "Initial amount of contract %a too low (required %a but provided %a)"
+          Contract_repr.pp c
           Tez_repr.pp r Tez_repr.pp p)
-    Data_encoding.(obj2
+    Data_encoding.(obj3
+                     (req "contract" Contract_repr.encoding)
                      (req "required" Tez_repr.encoding)
                      (req "provided" Tez_repr.encoding))
-    (function Initial_amount_too_low (r, p)   -> Some (r, p) | _ -> None)
-    (fun (r, p) -> Initial_amount_too_low (r, p)) ;
+    (function Initial_amount_too_low (c, r, p)   -> Some (c, r, p) | _ -> None)
+    (fun (c, r, p) -> Initial_amount_too_low (c, r, p)) ;
   register_error_kind
-    `Branch
+    `Permanent
     ~id:"contract.unspendable_contract"
     ~title:"Unspendable contract"
     ~description:"An operation tried to spend tokens from an unspendable contract"
     ~pp:(fun ppf c ->
-        Format.fprintf ppf "The tokens of contract %s can only be spent by its script"
-          (Contract_repr.to_b58check c))
+        Format.fprintf ppf "The tokens of contract %a can only be spent by its script"
+          Contract_repr.pp c)
     Data_encoding.(obj1 (req "contract" Contract_repr.encoding))
     (function Unspendable_contract c   -> Some c | _ -> None)
     (fun c -> Unspendable_contract c) ;
   register_error_kind
     `Temporary
     ~id:"contract.balance_too_low"
-    ~title:"Too low balance"
+    ~title:"Balance too low"
     ~description:"An operation tried to spend more tokens than the contract has"
     ~pp:(fun ppf (c, b, a) ->
-        Format.fprintf ppf "Balance of contract %s too low (%a) to spend %a"
-          (Contract_repr.to_b58check c) Tez_repr.pp b Tez_repr.pp a)
+        Format.fprintf ppf "Balance of contract %a too low (%a) to spend %a"
+          Contract_repr.pp c Tez_repr.pp b Tez_repr.pp a)
     Data_encoding.(obj3
                      (req "contract" Contract_repr.encoding)
                      (req "balance" Tez_repr.encoding)
                      (req "amount" Tez_repr.encoding))
     (function Balance_too_low (c, b, a)   -> Some (c, b, a) | _ -> None)
     (fun (c, b, a) -> Balance_too_low (c, b, a)) ;
+  register_error_kind
+    `Temporary
+    ~id:"contract.cannot_pay_storage_fee"
+    ~title:"Cannot pay storage fee"
+    ~description:"The storage fee is higher than the contract balance"
+    ~pp:(fun ppf (c, b, a) ->
+        Format.fprintf ppf "Balance of contract %a too low (%a) to pay storage fee %a"
+          Contract_repr.pp c Tez_repr.pp b Tez_repr.pp a)
+    Data_encoding.(obj3
+                     (req "contract" Contract_repr.encoding)
+                     (req "balance" Tez_repr.encoding)
+                     (req "storage_fee" Tez_repr.encoding))
+    (function Cannot_pay_storage_fee (c, b, a)   -> Some (c, b, a) | _ -> None)
+    (fun (c, b, a) -> Cannot_pay_storage_fee (c, b, a)) ;
   register_error_kind
     `Temporary
     ~id:"contract.counter_in_the_future"
@@ -73,8 +80,8 @@ let () =
     ~description:"An operation assumed a contract counter in the future"
     ~pp:(fun ppf (contract, exp, found) ->
         Format.fprintf ppf
-          "Counter %ld not yet reached for contract %s (expected %ld)"
-          found (Contract_repr.to_b58check contract) exp)
+          "Counter %ld not yet reached for contract %a (expected %ld)"
+          found Contract_repr.pp contract exp)
     Data_encoding.
       (obj3
          (req "contract" Contract_repr.encoding)
@@ -89,26 +96,57 @@ let () =
     ~description:"An operation assumed a contract counter in the past"
     ~pp:(fun ppf (contract, exp, found) ->
         Format.fprintf ppf
-          "Counter %ld already used for contract %s (expected %ld)"
-          found (Contract_repr.to_b58check contract) exp)
+          "Counter %ld already used for contract %a (expected %ld)"
+          found Contract_repr.pp contract exp)
     Data_encoding.
       (obj3
          (req "contract" Contract_repr.encoding)
          (req "expected" int32)
          (req "found" int32))
     (function Counter_in_the_past (c, x, y) -> Some (c, x, y) | _ -> None)
-    (fun (c, x, y) -> Counter_in_the_past (c, x, y))
+    (fun (c, x, y) -> Counter_in_the_past (c, x, y)) ;
+  register_error_kind
+    `Temporary
+    ~id:"contract.non_existing_contract"
+    ~title:"Non existing contract"
+    ~description:"A non default contract handle is not present in the context \
+                  (either it never was or it has been destroyed)"
+    ~pp:(fun ppf contract ->
+        Format.fprintf ppf "Contract %a does not exist"
+          Contract_repr.pp contract)
+    Data_encoding.(obj1 (req "contract" Contract_repr.encoding))
+    (function Non_existing_contract c -> Some c | _ -> None)
+    (fun c -> Non_existing_contract c) ;
+  register_error_kind
+    `Permanent
+    ~id:"contract.undelagatable_contract"
+    ~title:"Non delegatable contract"
+    ~description:"Tried to delegate a default contract \
+                  or a non delegatable originated contract"
+    ~pp:(fun ppf contract ->
+        Format.fprintf ppf "Contract %a is not delegatable"
+          Contract_repr.pp contract)
+    Data_encoding.(obj1 (req "contract" Contract_repr.encoding))
+    (function Non_existing_contract c -> Some c | _ -> None)
+    (fun c -> Non_existing_contract c) ;
+  register_error_kind
+    `Permanent
+    ~id:"contract.failure"
+    ~title:"Contract storage failure"
+    ~description:"Unexpected contract storage error"
+    ~pp:(fun ppf s -> Format.fprintf ppf "Contract_storage.Failure %S" s)
+    Data_encoding.(obj1 (req "message" string))
+    (function Failure s -> Some s | _ -> None)
+    (fun s -> Failure s)
 
 let failwith msg = fail (Failure msg)
 
-let create_base c contract ~balance ~manager ~delegate ~script ~spendable ~delegatable =
+let create_base c contract ~balance ~manager ~delegate ?script ~spendable ~delegatable =
   (match Contract_repr.is_default contract with
    | None -> return 0l
    | Some _ -> Storage.Contract.Global_counter.get c) >>=? fun counter ->
   Storage.Contract.Balance.init c contract balance >>=? fun c ->
   Storage.Contract.Manager.init c contract manager >>=? fun c ->
-  (* TODO, to answer:
-     If the contract is not delegatable, can it be created with a delegate ? *)
   begin
     match delegate with
     | None -> return c
@@ -120,26 +158,28 @@ let create_base c contract ~balance ~manager ~delegate ~script ~spendable ~deleg
   Storage.Contract.Assets.init c contract Asset_repr.Map.empty >>=? fun c ->
   Storage.Contract.Counter.init c contract counter >>=? fun c ->
   (match script with
-   | Script_repr.Script { code ; storage } ->
+   | Some ({ Script_repr.code ; storage }, (code_fees, storage_fees)) ->
        Storage.Contract.Code.init c contract code >>=? fun c ->
-       Storage.Contract.Storage.init c contract storage
-   | No_script ->
+       Storage.Contract.Storage.init c contract storage >>=? fun c ->
+       Storage.Contract.Code_fees.init c contract code_fees >>=? fun c ->
+       Storage.Contract.Storage_fees.init c contract storage_fees
+   | None ->
        return c) >>=? fun c ->
   Roll_storage.Contract.init c contract >>=? fun c ->
   Roll_storage.Contract.add_amount c contract balance >>=? fun c ->
   Storage.Contract.Set.add c contract >>=? fun c ->
   Lwt.return (Ok (c, contract))
 
-let create c nonce ~balance ~manager ~delegate ~script ~spendable ~delegatable =
+let create c nonce ~balance ~manager ~delegate ?script ~spendable ~delegatable =
   let contract = Contract_repr.originated_contract nonce in
-  create_base c contract ~balance ~manager ~delegate ~script ~spendable ~delegatable >>=? fun (ctxt, contract) ->
+  create_base c contract ~balance ~manager ~delegate ?script ~spendable ~delegatable >>=? fun (ctxt, contract) ->
   return (ctxt, contract, Contract_repr.incr_origination_nonce nonce)
 
 let create_default c manager ~balance =
-  let contract = Contract_repr.default_contract manager in
-  create_base c contract ~manager ~delegate:(Some manager)
-    ~spendable:true ~delegatable:false ~script:Script_repr.No_script
-    ~balance
+  create_base c (Contract_repr.default_contract manager)
+    ~balance ~manager ~delegate:(Some manager)
+    ?script:None
+    ~spendable:true ~delegatable:false
 
 let delete c contract =
   Storage.Contract.Balance.get c contract >>=? fun balance ->
@@ -153,6 +193,8 @@ let delete c contract =
   Storage.Contract.Counter.delete c contract >>=? fun c ->
   Storage.Contract.Code.remove c contract >>= fun c ->
   Storage.Contract.Storage.remove c contract >>= fun c ->
+  Storage.Contract.Code_fees.remove c contract >>= fun c ->
+  Storage.Contract.Storage_fees.remove c contract >>= fun c ->
   Storage.Contract.Set.del c contract
 
 let exists c contract =
@@ -163,6 +205,11 @@ let exists c contract =
       | None -> return false
       | Some _ -> return true
 
+let must_exist c contract =
+  exists c contract >>=? function
+  | true -> return ()
+  | false -> fail (Non_existing_contract contract)
+
 let list c =
   Storage.Contract.Set.elements c
 
@@ -186,8 +233,8 @@ let get_script c contract =
   Storage.Contract.Code.get_option c contract >>=? fun code ->
   Storage.Contract.Storage.get_option c contract >>=? fun storage ->
   match code, storage with
-  | None, None -> return Script_repr.No_script
-  | Some code, Some storage -> return (Script_repr.Script { code ; storage })
+  | None, None -> return None
+  | Some code, Some storage -> return (Some { Script_repr.code ; storage })
   | None, Some _ | Some _, None -> failwith "get_script"
 
 let get_counter c contract =
@@ -210,11 +257,6 @@ let get_manager c contract =
 
 let get_delegate_opt = Roll_storage.get_contract_delegate
 
-let get_delegate c contract =
-  get_delegate_opt c contract >>=? function
-  | None -> fail No_delegate
-  | Some delegate -> return delegate
-
 let get_balance c contract =
   Storage.Contract.Balance.get_option c contract >>=? function
   | None -> begin
@@ -255,7 +297,7 @@ let set_delegate c contract delegate =
   (* A contract delegate can be set only if the contract is delegatable *)
   Storage.Contract.Delegatable.get c contract >>=? fun delegatable ->
   if not delegatable
-  then fail Undelagatable_contract
+  then fail (Undelagatable_contract contract)
   else
     match delegate with
     | None ->
@@ -264,61 +306,56 @@ let set_delegate c contract delegate =
     | Some delegate ->
         Storage.Contract.Delegate.init_set c contract delegate
 
-let script_storage_fee script =
-  match script with
-  | Script_repr.No_script -> return Constants_repr.minimal_contract_balance
-  | Script { code ; storage } ->
-     let storage_fee = Script_repr.storage_cost storage in
-     let code_fee = Script_repr.code_cost code in
-     Lwt.return Tez_repr.(code_fee +? storage_fee) >>=? fun script_fee ->
-     Lwt.return Tez_repr.(Constants_repr.minimal_contract_balance +? script_fee)
+let contract_fee c contract =
+  Storage.Contract.Code_fees.get_option c contract >>=? fun code_fees ->
+  Storage.Contract.Storage_fees.get_option c contract >>=? fun storage_fees ->
+  match code_fees, storage_fees with
+  | (None, Some _) | (Some _, None) -> failwith "contract_fee"
+  | None, None ->
+      return Constants_repr.minimal_contract_balance
+  | Some code_fees, Some storage_fees ->
+      Lwt.return Tez_repr.(code_fees +? storage_fees) >>=? fun script_fees ->
+      Lwt.return Tez_repr.(Constants_repr.minimal_contract_balance +? script_fees)
 
-let update_script_storage c contract storage =
+let update_script_storage_and_fees c contract storage_fees storage =
   let open Script_repr in
   Storage.Contract.Balance.get_option c contract >>=? function
   | None ->
       (* The contract was destroyed *)
       return c
   | Some balance ->
-      get_script c contract >>=? function
-      | No_script -> failwith "update_script_storage"
-      | Script { code ; storage = { storage_type } } ->
-         script_storage_fee
-           (Script_repr.Script { code ; storage = { storage; storage_type }}) >>=? fun fee ->
-         fail_unless Tez_repr.(balance > fee)
-           (Balance_too_low (contract, balance, fee)) >>=? fun () ->
-         Storage.Contract.Storage.set c contract { storage; storage_type }
+      Storage.Contract.Storage.get c contract >>=? fun { storage_type } ->
+      Storage.Contract.Storage_fees.set c contract storage_fees >>=? fun c ->
+      contract_fee c contract >>=? fun fee ->
+      fail_unless Tez_repr.(balance > fee)
+        (Cannot_pay_storage_fee (contract, balance, fee)) >>=? fun () ->
+      Storage.Contract.Storage.set c contract { storage; storage_type }
 
-let unconditional_spend c contract amount =
+let spend_from_script c contract amount =
   Storage.Contract.Balance.get c contract >>=? fun balance ->
-  match Tez_repr.(balance - amount) with
-  | None ->
-      fail (Balance_too_low (contract, balance, amount))
-  | Some new_balance ->
-      get_script c contract >>=? fun script ->
-      script_storage_fee script >>=? fun fee ->
-      if Tez_repr.(fee <= new_balance) then
-        Storage.Contract.Balance.set c contract new_balance >>=? fun c ->
-        Roll_storage.Contract.remove_amount c contract amount
-      else
-        delete c contract
+  Lwt.return Tez_repr.(balance -? amount) |>
+  trace (Balance_too_low (contract, balance, amount)) >>=? fun new_balance ->
+  contract_fee c contract >>=? fun fee ->
+  if Tez_repr.(new_balance > fee) then
+    Storage.Contract.Balance.set c contract new_balance >>=? fun c ->
+    Roll_storage.Contract.remove_amount c contract amount
+  else
+    (* TODO: do we really want to allow overspending ? *)
+    delete c contract
 
 let credit c contract amount =
   Storage.Contract.Balance.get_option c contract >>=? function
   | None -> begin
-      (* If the contract does not exists and it is a default contract,
-         create it *)
       match Contract_repr.is_default contract with
-      | None -> fail Non_existing_contract
+      | None -> fail (Non_existing_contract contract)
       | Some manager ->
           if Tez_repr.(amount < Constants_repr.minimal_contract_balance)
           then
-            (* If this is not enough to maintain the contract alive,
-               we just drop the money *)
+            (* Not enough to keep a default contract alive: burn the tokens *)
             return c
           else
+            (* Otherwise, create the default contract. *)
             create_default c manager ~balance:amount >>=? fun (c, _) ->
-            (* TODO: fail_unless Contract_repr.(contract = new_contract) still needed ?? *)
             return c
     end
   | Some balance ->
@@ -339,16 +376,15 @@ let spend c contract amount =
   Storage.Contract.Spendable.get c contract >>=? fun spendable ->
   if not spendable
   then fail (Unspendable_contract contract)
-  else unconditional_spend c contract amount
+  else spend_from_script c contract amount
 
-let originate c nonce ~balance ~manager ~script ~delegate ~spendable ~delegatable  =
-  script_storage_fee script >>=? fun fee ->
+let originate c nonce ~balance ~manager ?script ~delegate ~spendable ~delegatable  =
+  create c nonce ~balance ~manager ~delegate ?script ~spendable ~delegatable >>=? fun (c, contract, nonce) ->
+  (* check contract fee *)
+  contract_fee c contract >>=? fun fee ->
   fail_unless Tez_repr.(balance > fee)
-    (Initial_amount_too_low (fee, balance)) >>=? fun () ->
-  create c nonce ~balance ~manager ~delegate ~script ~spendable ~delegatable
+    (Initial_amount_too_low (contract, balance, fee)) >>=? fun () ->
+  return (c, contract, nonce)
 
 let init c =
   Storage.Contract.Global_counter.init c 0l
-
-let pp fmt c =
-  Format.pp_print_string fmt (Contract_repr.to_b58check c)
diff --git a/src/proto/alpha/contract_storage.mli b/src/proto/alpha/contract_storage.mli
index 603c56831..a46394e55 100644
--- a/src/proto/alpha/contract_storage.mli
+++ b/src/proto/alpha/contract_storage.mli
@@ -8,19 +8,20 @@
 (**************************************************************************)
 
 type error +=
-  | Balance_too_low of Contract_repr.contract * Tez_repr.t * Tez_repr.t
-  | Initial_amount_too_low of Tez_repr.t * Tez_repr.t
-  | Counter_in_the_past of Contract_repr.contract * int32 * int32
-  | Counter_in_the_future of Contract_repr.contract * int32 * int32
-  | Unspendable_contract of Contract_repr.contract
-  | Non_existing_contract
-  | No_delegate
-  | Undelagatable_contract
-  | Failure of string
+  | Initial_amount_too_low of Contract_repr.contract * Tez_repr.t * Tez_repr.t (* `Permanent *)
+  | Balance_too_low of Contract_repr.contract * Tez_repr.t * Tez_repr.t (* `Temporary *)
+  | Cannot_pay_storage_fee of Contract_repr.contract * Tez_repr.t * Tez_repr.t (* `Temporary *)
+  | Counter_in_the_past of Contract_repr.contract * int32 * int32 (* `Branch *)
+  | Counter_in_the_future of Contract_repr.contract * int32 * int32 (* `Temporary *)
+  | Unspendable_contract of Contract_repr.contract (* `Permanent *)
+  | Non_existing_contract of Contract_repr.contract (* `Temporary *)
+  | Undelagatable_contract of Contract_repr.contract (* `Permanent *)
+  | Failure of string (* `Permanent *)
 
 val delete : Storage.t -> Contract_repr.t -> Storage.t tzresult Lwt.t
 
 val exists: Storage.t -> Contract_repr.t -> bool tzresult Lwt.t
+val must_exist: Storage.t -> Contract_repr.t -> unit tzresult Lwt.t
 
 val list: Storage.t -> Contract_repr.t list tzresult Lwt.t
 
@@ -31,19 +32,14 @@ val is_delegatable : Storage.t -> Contract_repr.t -> bool tzresult Lwt.t
 val is_spendable : Storage.t -> Contract_repr.t -> bool tzresult Lwt.t
 
 val get_manager: Storage.t -> Contract_repr.t -> Ed25519.Public_key_hash.t tzresult Lwt.t
-val get_delegate: Storage.t -> Contract_repr.t -> Ed25519.Public_key_hash.t tzresult Lwt.t
 val get_delegate_opt: Storage.t -> Contract_repr.t -> Ed25519.Public_key_hash.t option tzresult Lwt.t
 val get_balance: Storage.t -> Contract_repr.t -> Tez_repr.t tzresult Lwt.t
 val get_assets: Storage.t -> Contract_repr.t -> Asset_repr.Map.t tzresult Lwt.t
 val get_counter: Storage.t -> Contract_repr.t -> int32 tzresult Lwt.t
 
-val get_script: Storage.t -> Contract_repr.t -> Script_repr.t tzresult Lwt.t
+val get_script: Storage.t -> Contract_repr.t -> Script_repr.t option tzresult Lwt.t
 
-(** Update_script_storage fails if the contract has not enouth tez to
-    store the new data.
-    It does not fail if the contract does not exists *)
-val update_script_storage: Storage.t -> Contract_repr.t -> Script_repr.expr ->
-  Storage.t tzresult Lwt.t
+val update_script_storage_and_fees: Storage.t -> Contract_repr.t -> Tez_repr.t -> Script_repr.expr -> Storage.t tzresult Lwt.t
 
 (** fails if the contract is not delegatable *)
 val set_delegate : Storage.t -> Contract_repr.t -> Ed25519.Public_key_hash.t option -> Storage.t tzresult Lwt.t
@@ -53,8 +49,8 @@ val credit : Storage.t -> Contract_repr.t -> Tez_repr.t -> Storage.t tzresult Lw
 (** checks that the contract is spendable and decrease_balance *)
 val spend : Storage.t -> Contract_repr.t -> Tez_repr.t -> Storage.t tzresult Lwt.t
 
-(* decrease balance uncondionally *)
-val unconditional_spend : Storage.t -> Contract_repr.t -> Tez_repr.t -> Storage.t tzresult Lwt.t
+(** decrease_balance even if the contract is not spendable *)
+val spend_from_script : Storage.t -> Contract_repr.t -> Tez_repr.t -> Storage.t tzresult Lwt.t
 
 val issue :
   Storage.t -> Contract_repr.t ->  Asset_repr.t -> Ed25519.Public_key_hash.t -> Tez_repr.t -> Storage.t tzresult Lwt.t
@@ -64,7 +60,7 @@ val originate :
   Contract_repr.origination_nonce ->
   balance:Tez_repr.t ->
   manager:Ed25519.Public_key_hash.t ->
-  script:Script_repr.t ->
+  ?script:(Script_repr.t * (Tez_repr.t * Tez_repr.t)) ->
   delegate:Ed25519.Public_key_hash.t option ->
   spendable:bool ->
   delegatable:bool ->
@@ -72,5 +68,3 @@ val originate :
 
 val init :
   Storage.t -> Storage.t tzresult Lwt.t
-
-val pp: Format.formatter -> Contract_repr.t -> unit
diff --git a/src/proto/alpha/mining.ml b/src/proto/alpha/mining.ml
index 38a9c5b4a..8cc281238 100644
--- a/src/proto/alpha/mining.ml
+++ b/src/proto/alpha/mining.ml
@@ -76,13 +76,12 @@ let pay_mining_bond c
   if Compare.Int32.(priority >= Constants.first_free_mining_slot c)
   then return c
   else
-    Contract.unconditional_spend c
-      (Contract.default_contract id) Constants.mining_bond_cost
+    Contract.spend c (Contract.default_contract id) Constants.mining_bond_cost
     |> trace Cannot_pay_mining_bond
 
 let pay_endorsement_bond c id =
   let bond = Constants.endorsement_bond_cost in
-  Contract.unconditional_spend c (Contract.default_contract id) bond
+  Contract.spend c (Contract.default_contract id) bond
   |> trace Cannot_pay_endorsement_bond >>=? fun c ->
   return (c, bond)
 
diff --git a/src/proto/alpha/operation_repr.ml b/src/proto/alpha/operation_repr.ml
index 20c32b9d0..c4bdf50be 100644
--- a/src/proto/alpha/operation_repr.ml
+++ b/src/proto/alpha/operation_repr.ml
@@ -53,7 +53,7 @@ and manager_operation =
   | Origination of {
       manager: Ed25519.Public_key_hash.t ;
       delegate: Ed25519.Public_key_hash.t option ;
-      script: Script_repr.t ;
+      script: Script_repr.t option ;
       spendable: bool ;
       delegatable: bool ;
       credit: Tez_repr.tez ;
@@ -113,7 +113,7 @@ module Encoding = struct
        (opt "spendable" bool)
        (opt "delegatable" bool)
        (opt "delegate" Ed25519.Public_key_hash.encoding)
-       (req "script" Script_repr.encoding))
+       (opt "script" Script_repr.encoding))
 
   let origination_case tag =
     case ~tag origination_encoding
diff --git a/src/proto/alpha/operation_repr.mli b/src/proto/alpha/operation_repr.mli
index 99c425944..9d2e6d9f8 100644
--- a/src/proto/alpha/operation_repr.mli
+++ b/src/proto/alpha/operation_repr.mli
@@ -53,7 +53,7 @@ and manager_operation =
   | Origination of {
       manager: Ed25519.Public_key_hash.t ;
       delegate: Ed25519.Public_key_hash.t option ;
-      script: Script_repr.t ;
+      script: Script_repr.t option ;
       spendable: bool ;
       delegatable: bool ;
       credit: Tez_repr.tez ;
diff --git a/src/proto/alpha/script_interpreter.ml b/src/proto/alpha/script_interpreter.ml
index 8b2e2a5f7..01cdf880f 100644
--- a/src/proto/alpha/script_interpreter.ml
+++ b/src/proto/alpha/script_interpreter.ml
@@ -13,6 +13,9 @@ open Script
 open Script_typed_ir
 open Script_ir_translator
 
+let dummy_code_fee = Tez.zero
+let dummy_storage_fee = Tez.zero
+
 (* ---- Run-time errors -----------------------------------------------------*)
 
 type error += Quota_exceeded
@@ -394,65 +397,64 @@ let rec interp
               logged_return (Item (manager, rest), qta - 1, ctxt)
           | Transfer_tokens storage_type,
             Item (p, Item (amount, Item ((tp, Unit_t, destination), Item (sto, Empty)))) -> begin
-              Contract.unconditional_spend ctxt source amount >>=? fun ctxt ->
+              Contract.spend_from_script ctxt source amount >>=? fun ctxt ->
+              Lwt.return Tez.(amount -? Constants.origination_burn) >>=? fun amount ->
               Contract.credit ctxt destination amount >>=? fun ctxt ->
               Contract.get_script ctxt destination >>=? fun destination_script ->
               let sto = unparse_data storage_type sto in
-              Contract.update_script_storage ctxt source sto >>=? fun ctxt ->
+              Contract.update_script_storage_and_fees ctxt source dummy_storage_fee sto >>=? fun ctxt ->
               begin match destination_script with
-                | No_script ->
+                | None ->
                     (* we see non scripted contracts as (unit, unit) contract *)
                     Lwt.return (ty_eq tp Unit_t |>
                                 record_trace (Invalid_contract (loc, destination))) >>=? fun (Eq _) ->
                     return (ctxt, qta, origination)
-                | Script { code ; storage } ->
+                | Some { code ; storage } ->
                     let p = unparse_data tp p in
                     execute origination source destination ctxt storage code amount p qta
                     >>=? fun (csto, ret, qta, ctxt, origination) ->
-                    Contract.update_script_storage
-                      ctxt destination csto >>=? fun ctxt ->
+                    Contract.update_script_storage_and_fees ctxt destination dummy_storage_fee csto >>=? fun ctxt ->
                     trace
                       (Invalid_contract (loc, destination))
                       (parse_data ctxt Unit_t ret) >>=? fun () ->
                     return (ctxt, qta, origination)
               end >>=? fun (ctxt, qta, origination) ->
               Contract.get_script ctxt source >>=? (function
-                  | No_script -> assert false
-                  | Script { storage = { storage } } ->
+                  | None -> assert false
+                  | Some { storage = { storage } } ->
                       parse_data ctxt storage_type storage >>=? fun sto ->
                       logged_return ~origination (Item ((), Item (sto, Empty)), qta - 1, ctxt))
             end
           | Transfer_tokens storage_type,
             Item (p, Item (amount, Item ((tp, tr, destination), Item (sto, Empty)))) -> begin
-              Contract.unconditional_spend ctxt source amount >>=? fun ctxt ->
+              Contract.spend_from_script ctxt source amount >>=? fun ctxt ->
               Contract.credit ctxt destination amount >>=? fun ctxt ->
               Contract.get_script ctxt destination >>=? function
-              | No_script -> fail (Invalid_contract (loc, destination))
-              | Script { code ; storage } ->
+              | None -> fail (Invalid_contract (loc, destination))
+              | Some { code ; storage } ->
                   let sto = unparse_data storage_type sto in
-                  Contract.update_script_storage ctxt source sto >>=? fun ctxt ->
+                  Contract.update_script_storage_and_fees ctxt source dummy_storage_fee sto >>=? fun ctxt ->
                   let p = unparse_data tp p in
                   execute origination source destination ctxt storage code amount p qta
                   >>=? fun (sto, ret, qta, ctxt, origination) ->
-                  Contract.update_script_storage
-                    ctxt destination sto >>=? fun ctxt ->
+                  Contract.update_script_storage_and_fees ctxt destination dummy_storage_fee sto >>=? fun ctxt ->
                   trace
                     (Invalid_contract (loc, destination))
                     (parse_data ctxt tr ret) >>=? fun v ->
                   Contract.get_script ctxt source >>=? (function
-                      | No_script -> assert false
-                      | Script { storage = { storage } } ->
+                      | None -> assert false
+                      | Some { storage = { storage } } ->
                           parse_data ctxt storage_type storage >>=? fun sto ->
                           logged_return ~origination (Item (v, Item (sto, Empty)), qta - 1, ctxt))
             end
           | Create_account,
             Item (manager, Item (delegate, Item (delegatable, Item (credit, rest)))) ->
-              Contract.unconditional_spend ctxt source credit >>=? fun ctxt ->
+              Contract.spend_from_script ctxt source credit >>=? fun ctxt ->
               Lwt.return Tez.(credit -? Constants.origination_burn) >>=? fun balance ->
               Contract.originate ctxt
                 origination
                 ~manager ~delegate ~balance
-                ~script:No_script ~spendable:true ~delegatable >>=? fun (ctxt, contract, origination) ->
+                ?script:None ~spendable:true ~delegatable >>=? fun (ctxt, contract, origination) ->
               logged_return ~origination (Item ((Unit_t, Unit_t, contract), rest), qta - 1, ctxt)
           | Create_contract (g, p, r),
             Item (manager, Item (delegate, Item (delegatable, Item (credit,
@@ -460,19 +462,13 @@ let rec interp
               let code, storage =
                 { code; arg_type = unparse_ty p; ret_type = unparse_ty r; storage_type =  unparse_ty g },
                 { storage = unparse_data g init; storage_type =  unparse_ty g } in
-              let storage_fee = Script.storage_cost storage in
-              let code_fee = Script.code_cost code in
-              Lwt.return Tez.(code_fee +? storage_fee) >>=? fun script_fee ->
-              Lwt.return Tez.(script_fee +?
-                              Constants.origination_burn) >>=? fun total_fee ->
-              fail_unless Tez.(credit > total_fee)
-                (Contract.Initial_amount_too_low (total_fee, credit)) >>=? fun () ->
-              Contract.unconditional_spend ctxt source credit >>=? fun ctxt ->
+              Contract.spend_from_script ctxt source credit >>=? fun ctxt ->
               Lwt.return Tez.(credit -? Constants.origination_burn) >>=? fun balance ->
               Contract.originate ctxt
                 origination
                 ~manager ~delegate ~balance
-                ~script:(Script { code ; storage }) ~spendable:true ~delegatable
+                ~script:({ code ; storage }, (dummy_code_fee, dummy_storage_fee))
+                ~spendable:true ~delegatable
               >>=? fun (ctxt, contract, origination) ->
               logged_return ~origination (Item ((p, r, contract), rest), qta - 1, ctxt)
           | Balance, rest ->
diff --git a/src/proto/alpha/script_interpreter.mli b/src/proto/alpha/script_interpreter.mli
index a5aad7940..df7413e04 100644
--- a/src/proto/alpha/script_interpreter.mli
+++ b/src/proto/alpha/script_interpreter.mli
@@ -14,6 +14,9 @@ type error += Overflow of Script.location
 type error += Reject of Script.location
 type error += Division_by_zero of Script.location
 
+val dummy_code_fee : Tez.t
+val dummy_storage_fee : Tez.t
+
 (* calling convention :
    ((amount, arg), globals)) -> (ret, globals) *)
 
diff --git a/src/proto/alpha/script_ir_translator.ml b/src/proto/alpha/script_ir_translator.ml
index e2a307b20..a31b1c8c5 100644
--- a/src/proto/alpha/script_ir_translator.ml
+++ b/src/proto/alpha/script_ir_translator.ml
@@ -1388,14 +1388,14 @@ and parse_contract
         trace
           (Invalid_contract (loc, contract)) @@
         Contract.get_script ctxt contract >>=? function
-        | No_script ->
+        | None ->
             Lwt.return
               (ty_eq arg Unit_t >>? fun (Eq _) ->
                ty_eq ret Unit_t >>? fun (Eq _) ->
                let contract : (arg, ret) typed_contract =
                  (arg, ret, contract) in
                ok contract)
-        | Script { code = { arg_type; ret_type} } ->
+        | Some { code = { arg_type; ret_type} } ->
             Lwt.return
               (parse_ty arg_type >>? fun (Ex_ty targ) ->
                parse_ty ret_type >>? fun (Ex_ty tret) ->
diff --git a/src/proto/alpha/script_repr.ml b/src/proto/alpha/script_repr.ml
index ab7a4f627..e42e2436b 100644
--- a/src/proto/alpha/script_repr.ml
+++ b/src/proto/alpha/script_repr.ml
@@ -110,9 +110,6 @@ type storage =
   { storage : expr ;
     storage_type : expr }
 
-let storage_cost _ = Tez_repr.of_cents_exn 50L (* FIXME *)
-let code_cost _ = Tez_repr.of_cents_exn 50L (* FIXME *)
-
 open Data_encoding
 
 let storage_encoding =
@@ -140,22 +137,14 @@ let hash_expr data =
   Script_expr_hash.(hash_bytes [ bytes ] |> to_b58check)
 
 type t =
-  | No_script
-  | Script of {
-      code: code ;
-      storage: storage ;
-    }
+  { code : code ;
+    storage : storage }
 
 let encoding =
   let open Data_encoding in
-  union ~tag_size:`Uint8 [
-    case ~tag:0 empty
-      (function No_script -> Some () | _ -> None)
-      (fun () -> No_script) ;
-    case ~tag:1
-      (obj2
-         (req "code" code_encoding)
-         (req "storage" storage_encoding))
-      (function Script { code ; storage } -> Some (code, storage) | _ -> None)
-      (fun (code, storage) -> Script { code ; storage })
-  ]
+  conv
+    (function { code ; storage } -> (code, storage))
+    (fun (code, storage) -> { code ; storage })
+    (obj2
+       (req "code" code_encoding)
+       (req "storage" storage_encoding))
diff --git a/src/proto/alpha/script_repr.mli b/src/proto/alpha/script_repr.mli
index 1626022bb..43c8f371c 100644
--- a/src/proto/alpha/script_repr.mli
+++ b/src/proto/alpha/script_repr.mli
@@ -7,8 +7,6 @@
 (*                                                                        *)
 (**************************************************************************)
 
-(** Tezos protocol 1234abc1212 - untyped script representation *)
-
 type location =
   int
 
@@ -29,11 +27,8 @@ type storage =
     storage_type : expr }
 
 type t =
-  | No_script
-  | Script of {
-      code: code ;
-      storage: storage ;
-    }
+  { code : code ;
+    storage : storage }
 
 val location_encoding : location Data_encoding.t
 val expr_encoding : expr Data_encoding.t
@@ -41,7 +36,4 @@ val storage_encoding : storage Data_encoding.t
 val code_encoding : code Data_encoding.t
 val encoding : t Data_encoding.t
 
-val storage_cost : storage -> Tez_repr.tez
-val code_cost : code -> Tez_repr.tez
-
 val hash_expr : expr -> string
diff --git a/src/proto/alpha/services.ml b/src/proto/alpha/services.ml
index f3fdb521e..e471318c0 100644
--- a/src/proto/alpha/services.ml
+++ b/src/proto/alpha/services.ml
@@ -253,7 +253,7 @@ module Context = struct
       RPC.service
         ~description: "Access the code and data of the contract."
         ~input: empty
-        ~output: (wrap_tzerror Script.encoding)
+        ~output: (wrap_tzerror (option Script.encoding))
         RPC.Path.(custom_root / "context" / "contracts" /: Contract.arg / "script")
 
     let assets custom_root =
@@ -268,7 +268,7 @@ module Context = struct
       balance: Tez.t ;
       spendable: bool ;
       delegate: bool * public_key_hash option ;
-      script: Script.t ;
+      script: Script.t option ;
       assets: Asset.Map.t ;
       counter: int32 ;
     }
@@ -291,7 +291,7 @@ module Context = struct
              (req "delegate" @@ obj2
                 (req "setable" bool)
                 (opt "value" Ed25519.Public_key_hash.encoding))
-             (dft "script" Script.encoding No_script)
+             (opt "script" Script.encoding)
              (req "assets" Asset.Map.encoding)
              (req "counter" int32))
         RPC.Path.(custom_root / "context" / "contracts" /: Contract.arg)
diff --git a/src/proto/alpha/storage.ml b/src/proto/alpha/storage.ml
index ed66dbf73..05050946b 100644
--- a/src/proto/alpha/storage.ml
+++ b/src/proto/alpha/storage.ml
@@ -117,6 +117,8 @@ module Key = struct
     let counter c = contract_store c ["counter"]
     let code c = contract_store c ["code"]
     let storage c = contract_store c ["storage"]
+    let code_fees c = contract_store c ["code_fees"]
+    let storage_fees c = contract_store c ["storage_fees"]
   end
 
   module Vote = struct
@@ -330,6 +332,24 @@ module Contract = struct
       let encoding = Script_repr.storage_encoding
     end)
 
+  module Code_fees =
+    Make_indexed_data_storage(struct
+      type key = Contract_repr.t
+      type value = Tez_repr.t
+      let name = "contract code fees"
+      let key = Key.Contract.code_fees
+      let encoding = Tez_repr.encoding
+    end)
+
+  module Storage_fees =
+    Make_indexed_data_storage(struct
+      type key = Contract_repr.t
+      type value = Tez_repr.t
+      let name = "contract storage fees"
+      let key = Key.Contract.storage_fees
+      let encoding = Tez_repr.encoding
+    end)
+
 end
 
 (** Votes **)
diff --git a/src/proto/alpha/storage.mli b/src/proto/alpha/storage.mli
index 731242152..fbe29cd8f 100644
--- a/src/proto/alpha/storage.mli
+++ b/src/proto/alpha/storage.mli
@@ -174,6 +174,16 @@ module Contract : sig
      and type value = Script_repr.storage
      and type context := t
 
+  module Code_fees : Indexed_data_storage
+    with type key = Contract_repr.t
+     and type value = Tez_repr.t
+     and type context := t
+
+  module Storage_fees : Indexed_data_storage
+    with type key = Contract_repr.t
+     and type value = Tez_repr.t
+     and type context := t
+
 end
 
 (** Votes *)
diff --git a/src/proto/alpha/tezos_context.mli b/src/proto/alpha/tezos_context.mli
index 2010013b7..793ae2f37 100644
--- a/src/proto/alpha/tezos_context.mli
+++ b/src/proto/alpha/tezos_context.mli
@@ -126,11 +126,8 @@ module Script : sig
   }
 
   type t =
-    | No_script
-    | Script of {
-        code: code ;
-        storage: storage ;
-      }
+    { code : code ;
+      storage : storage }
 
   val location_encoding: location Data_encoding.t
   val expr_encoding: expr Data_encoding.t
@@ -138,10 +135,7 @@ module Script : sig
   val code_encoding: code Data_encoding.t
   val encoding: t Data_encoding.t
 
-  val storage_cost: storage -> Tez.t
-  val code_cost: code -> Tez.t
-
-  val hash_expr: expr -> string
+  val hash_expr : expr -> string
 
 end
 
@@ -316,6 +310,8 @@ module Contract : sig
   val is_default: contract -> public_key_hash option
 
   val exists: context -> contract -> bool tzresult Lwt.t
+  val must_exist: context -> contract -> unit tzresult Lwt.t
+
   val list: context -> contract list tzresult Lwt.t
 
   type origination_nonce
@@ -328,8 +324,6 @@ module Contract : sig
 
   val get_manager:
     context -> contract -> public_key_hash tzresult Lwt.t
-  val get_delegate:
-    context -> contract -> public_key_hash tzresult Lwt.t
   val get_delegate_opt:
     context -> contract -> public_key_hash option tzresult Lwt.t
   val is_delegatable:
@@ -337,7 +331,7 @@ module Contract : sig
   val is_spendable:
     context -> contract -> bool tzresult Lwt.t
   val get_script:
-    context -> contract -> Script.t tzresult Lwt.t
+    context -> contract -> (Script.t option) tzresult Lwt.t
 
   val get_counter: context -> contract -> int32 tzresult Lwt.t
   val get_balance:
@@ -348,14 +342,14 @@ module Contract : sig
   val set_delegate:
     context -> contract -> public_key_hash option -> context tzresult Lwt.t
 
-  type error += Initial_amount_too_low of Tez.t * Tez.t
+  type error += Initial_amount_too_low of contract * Tez.t * Tez.t
 
   val originate:
     context ->
     origination_nonce ->
     balance: Tez.t ->
     manager: public_key_hash ->
-    script: Script.t ->
+    ?script: (Script.t * (Tez.t * Tez.t)) ->
     delegate: public_key_hash option ->
     spendable: bool ->
     delegatable: bool -> (context * contract * origination_nonce) tzresult Lwt.t
@@ -364,7 +358,7 @@ module Contract : sig
 
   val spend:
     context -> contract -> Tez.t -> context tzresult Lwt.t
-  val unconditional_spend:
+  val spend_from_script:
     context -> contract -> Tez.t -> context tzresult Lwt.t
 
   val credit:
@@ -373,8 +367,8 @@ module Contract : sig
     context -> contract ->
     Asset.t -> public_key_hash -> Tez.t -> context tzresult Lwt.t
 
-  val update_script_storage:
-    context -> contract -> Script.expr -> context tzresult Lwt.t
+  val update_script_storage_and_fees:
+    context -> contract -> Tez.t -> Script.expr -> context tzresult Lwt.t
 
   val increment_counter:
     context -> contract -> context tzresult Lwt.t
@@ -474,7 +468,7 @@ and manager_operation =
   | Origination of {
       manager: public_key_hash ;
       delegate: public_key_hash option ;
-      script: Script.t ;
+      script: Script.t option ;
       spendable: bool ;
       delegatable: bool ;
       credit: Tez.t ;