diff --git a/api/openapi.yaml b/api/openapi.yaml
index 8233788..ae50452 100644
--- a/api/openapi.yaml
+++ b/api/openapi.yaml
@@ -1108,12 +1108,16 @@ paths:
                 $ref: "#/components/schemas/ApplicationError"
               example: {type: "VALIDATION_ERROR", message: "Invalid request data."}
         "404":
-          description: Channel not found
+          description: Channel or wallet not found
           content:
             application/json:
               schema:
                 $ref: "#/components/schemas/ApplicationError"
-              example: {type: "NOT_FOUND", message: "The requested channel was not found."}
+              examples:
+                channelNotFound:
+                  value: {type: "NOT_FOUND", code: "CHANNEL_NOT_FOUND", message: "channel with ID abc not found"}
+                walletNotFound:
+                  value: {type: "NOT_FOUND", code: "WALLET_NOT_FOUND", message: "wallet with address 0x742d35Cc6634C0532925a3b844Bc454e4438f44e and chain_selector 16015286601757825753 not found"}
         "500":
           description: Internal server error
           content:
@@ -2151,6 +2155,22 @@ components:
         - to
         - value
         - data
+    ApplicationErrorCode:
+      type: string
+      description: Machine-readable error code for NOT_FOUND responses.
+      enum:
+        - CHANNEL_NOT_FOUND
+        - WALLET_NOT_FOUND
+        - OPERATION_NOT_FOUND
+        - WATCHER_NOT_FOUND
+        - QUERY_NOT_FOUND
+      x-enum-varnames:
+        - ApplicationErrorCodeChannelNotFound
+        - ApplicationErrorCodeWalletNotFound
+        - ApplicationErrorCodeOperationNotFound
+        - ApplicationErrorCodeWatcherNotFound
+        - ApplicationErrorCodeQueryNotFound
+      example: "WALLET_NOT_FOUND"
     ApplicationError:
       description: Standard error response body.
       type: object
@@ -2165,6 +2185,8 @@ components:
             - "CONFLICT"
             - "INTERNAL_ERROR"
             - "ORGANIZATION_NOT_FOUND"
+        code:
+          $ref: "#/components/schemas/ApplicationErrorCode"
         message:
           type: string
           description: Error message describing the issue
diff --git a/client/client.gen.go b/client/client.gen.go
index 98ae384..5cfd82c 100644
--- a/client/client.gen.go
+++ b/client/client.gen.go
@@ -31,6 +31,15 @@ const (
 	VALIDATIONERROR      ApplicationErrorType = "VALIDATION_ERROR"
 )
 
+// Defines values for ApplicationErrorCode.
+const (
+	ApplicationErrorCodeChannelNotFound   ApplicationErrorCode = "CHANNEL_NOT_FOUND"
+	ApplicationErrorCodeOperationNotFound ApplicationErrorCode = "OPERATION_NOT_FOUND"
+	ApplicationErrorCodeQueryNotFound     ApplicationErrorCode = "QUERY_NOT_FOUND"
+	ApplicationErrorCodeWalletNotFound    ApplicationErrorCode = "WALLET_NOT_FOUND"
+	ApplicationErrorCodeWatcherNotFound   ApplicationErrorCode = "WATCHER_NOT_FOUND"
+)
+
 // Defines values for BlockNumberBlockSelectionType.
 const (
 	BlockNumberBlockSelectionTypeBlockNumber BlockNumberBlockSelectionType = "block_number"
@@ -144,6 +153,9 @@ const (
 
 // ApplicationError Standard error response body.
 type ApplicationError struct {
+	// Code Machine-readable error code for NOT_FOUND responses.
+	Code *ApplicationErrorCode `json:"code,omitempty"`
+
 	// Message Error message describing the issue
 	Message string `json:"message"`
 
@@ -154,6 +166,9 @@ type ApplicationError struct {
 // ApplicationErrorType Error type
 type ApplicationErrorType string
 
+// ApplicationErrorCode Machine-readable error code for NOT_FOUND responses.
+type ApplicationErrorCode string
+
 // BlockNumberBlockSelection defines model for BlockNumberBlockSelection.
 type BlockNumberBlockSelection struct {
 	// BlockNumber Decimal uint64 block number.
diff --git a/ginserver/ginserver.gen.go b/ginserver/ginserver.gen.go
index 18b7493..3a0b9e8 100644
--- a/ginserver/ginserver.gen.go
+++ b/ginserver/ginserver.gen.go
@@ -29,6 +29,15 @@ const (
 	VALIDATIONERROR      ApplicationErrorType = "VALIDATION_ERROR"
 )
 
+// Defines values for ApplicationErrorCode.
+const (
+	ApplicationErrorCodeChannelNotFound   ApplicationErrorCode = "CHANNEL_NOT_FOUND"
+	ApplicationErrorCodeOperationNotFound ApplicationErrorCode = "OPERATION_NOT_FOUND"
+	ApplicationErrorCodeQueryNotFound     ApplicationErrorCode = "QUERY_NOT_FOUND"
+	ApplicationErrorCodeWalletNotFound    ApplicationErrorCode = "WALLET_NOT_FOUND"
+	ApplicationErrorCodeWatcherNotFound   ApplicationErrorCode = "WATCHER_NOT_FOUND"
+)
+
 // Defines values for BlockNumberBlockSelectionType.
 const (
 	BlockNumberBlockSelectionTypeBlockNumber BlockNumberBlockSelectionType = "block_number"
@@ -142,6 +151,9 @@ const (
 
 // ApplicationError Standard error response body.
 type ApplicationError struct {
+	// Code Machine-readable error code for NOT_FOUND responses.
+	Code *ApplicationErrorCode `json:"code,omitempty"`
+
 	// Message Error message describing the issue
 	Message string `json:"message"`
 
@@ -152,6 +164,9 @@ type ApplicationError struct {
 // ApplicationErrorType Error type
 type ApplicationErrorType string
 
+// ApplicationErrorCode Machine-readable error code for NOT_FOUND responses.
+type ApplicationErrorCode string
+
 // BlockNumberBlockSelection defines model for BlockNumberBlockSelection.
 type BlockNumberBlockSelection struct {
 	// BlockNumber Decimal uint64 block number.
diff --git a/stdserver/stdserver.gen.go b/stdserver/stdserver.gen.go
index 1598057..7ee1bd5 100644
--- a/stdserver/stdserver.gen.go
+++ b/stdserver/stdserver.gen.go
@@ -29,6 +29,15 @@ const (
 	VALIDATIONERROR      ApplicationErrorType = "VALIDATION_ERROR"
 )
 
+// Defines values for ApplicationErrorCode.
+const (
+	ApplicationErrorCodeChannelNotFound   ApplicationErrorCode = "CHANNEL_NOT_FOUND"
+	ApplicationErrorCodeOperationNotFound ApplicationErrorCode = "OPERATION_NOT_FOUND"
+	ApplicationErrorCodeQueryNotFound     ApplicationErrorCode = "QUERY_NOT_FOUND"
+	ApplicationErrorCodeWalletNotFound    ApplicationErrorCode = "WALLET_NOT_FOUND"
+	ApplicationErrorCodeWatcherNotFound   ApplicationErrorCode = "WATCHER_NOT_FOUND"
+)
+
 // Defines values for BlockNumberBlockSelectionType.
 const (
 	BlockNumberBlockSelectionTypeBlockNumber BlockNumberBlockSelectionType = "block_number"
@@ -142,6 +151,9 @@ const (
 
 // ApplicationError Standard error response body.
 type ApplicationError struct {
+	// Code Machine-readable error code for NOT_FOUND responses.
+	Code *ApplicationErrorCode `json:"code,omitempty"`
+
 	// Message Error message describing the issue
 	Message string `json:"message"`
 
@@ -152,6 +164,9 @@ type ApplicationError struct {
 // ApplicationErrorType Error type
 type ApplicationErrorType string
 
+// ApplicationErrorCode Machine-readable error code for NOT_FOUND responses.
+type ApplicationErrorCode string
+
 // BlockNumberBlockSelection defines model for BlockNumberBlockSelection.
 type BlockNumberBlockSelection struct {
 	// BlockNumber Decimal uint64 block number.