diff --git a/go/cmd/vtctldclient/command/vreplication/workflow/state.go b/go/cmd/vtctldclient/command/vreplication/workflow/state.go
index a5555d78b0e..89e75312ab2 100644
--- a/go/cmd/vtctldclient/command/vreplication/workflow/state.go
+++ b/go/cmd/vtctldclient/command/vreplication/workflow/state.go
@@ -82,7 +82,6 @@ func commandUpdateState(cmd *cobra.Command, args []string) error {
 			TabletTypes: []topodatapb.TabletType{topodatapb.TabletType(textutil.SimulatedNullInt)},
 			OnDdl:       binlogdatapb.OnDDLAction(textutil.SimulatedNullInt),
 			State:       state,
-			Shards:      baseOptions.Shards,
 		},
 	}
 
diff --git a/go/cmd/vtctldclient/command/vreplication/workflow/update.go b/go/cmd/vtctldclient/command/vreplication/workflow/update.go
index 52df87acc8b..3d06ad3e64e 100644
--- a/go/cmd/vtctldclient/command/vreplication/workflow/update.go
+++ b/go/cmd/vtctldclient/command/vreplication/workflow/update.go
@@ -111,7 +111,7 @@ func commandUpdate(cmd *cobra.Command, args []string) error {
 			TabletTypes:               updateOptions.TabletTypes,
 			TabletSelectionPreference: tsp,
 			OnDdl:                     binlogdatapb.OnDDLAction(onddl),
-			Shards:                    baseOptions.Shards,
+			State:                     binlogdatapb.VReplicationWorkflowState(textutil.SimulatedNullInt), // We don't allow changing this in the client command
 		},
 	}
 
diff --git a/go/test/endtoend/vreplication/resharding_workflows_v2_test.go b/go/test/endtoend/vreplication/resharding_workflows_v2_test.go
index b14b649d6b7..c63fc245535 100644
--- a/go/test/endtoend/vreplication/resharding_workflows_v2_test.go
+++ b/go/test/endtoend/vreplication/resharding_workflows_v2_test.go
@@ -26,12 +26,14 @@ import (
 
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
+	"google.golang.org/protobuf/encoding/protojson"
 
 	"vitess.io/vitess/go/test/endtoend/cluster"
 	"vitess.io/vitess/go/vt/log"
 	"vitess.io/vitess/go/vt/wrangler"
 
 	binlogdatapb "vitess.io/vitess/go/vt/proto/binlogdata"
+	vtctldatapb "vitess.io/vitess/go/vt/proto/vtctldata"
 )
 
 const (
@@ -212,19 +214,42 @@ func tstWorkflowComplete(t *testing.T) error {
 // to primary,replica,rdonly (the only applicable types in these tests).
 func testWorkflowUpdate(t *testing.T) {
 	tabletTypes := "primary,replica,rdonly"
-	// Test vtctlclient first
+	// Test vtctlclient first.
 	_, err := vc.VtctlClient.ExecuteCommandWithOutput("workflow", "--", "--tablet-types", tabletTypes, "noexist.noexist", "update")
 	require.Error(t, err, err)
 	resp, err := vc.VtctlClient.ExecuteCommandWithOutput("workflow", "--", "--tablet-types", tabletTypes, ksWorkflow, "update")
 	require.NoError(t, err)
 	require.NotEmpty(t, resp)
 
-	// Test vtctldclient last
+	// Test vtctldclient last.
 	_, err = vc.VtctldClient.ExecuteCommandWithOutput("workflow", "--keyspace", "noexist", "update", "--workflow", "noexist", "--tablet-types", tabletTypes)
 	require.Error(t, err)
+	// Change the tablet-types to rdonly.
+	resp, err = vc.VtctldClient.ExecuteCommandWithOutput("workflow", "--keyspace", targetKs, "update", "--workflow", workflowName, "--tablet-types", "rdonly")
+	require.NoError(t, err, err)
+	// Confirm that we changed the workflow.
+	var ures vtctldatapb.WorkflowUpdateResponse
+	require.NoError(t, err)
+	err = protojson.Unmarshal([]byte(resp), &ures)
+	require.NoError(t, err)
+	require.Greater(t, len(ures.Details), 0)
+	require.True(t, ures.Details[0].Changed)
+	// Change tablet-types back to primary,replica,rdonly.
 	resp, err = vc.VtctldClient.ExecuteCommandWithOutput("workflow", "--keyspace", targetKs, "update", "--workflow", workflowName, "--tablet-types", tabletTypes)
 	require.NoError(t, err, err)
-	require.NotEmpty(t, resp)
+	// Confirm that we changed the workflow.
+	err = protojson.Unmarshal([]byte(resp), &ures)
+	require.NoError(t, err)
+	require.Greater(t, len(ures.Details), 0)
+	require.True(t, ures.Details[0].Changed)
+	// Execute a no-op as tablet-types is already primary,replica,rdonly.
+	resp, err = vc.VtctldClient.ExecuteCommandWithOutput("workflow", "--keyspace", targetKs, "update", "--workflow", workflowName, "--tablet-types", tabletTypes)
+	require.NoError(t, err, err)
+	// Confirm that we didn't change the workflow.
+	err = protojson.Unmarshal([]byte(resp), &ures)
+	require.NoError(t, err)
+	require.Greater(t, len(ures.Details), 0)
+	require.False(t, ures.Details[0].Changed)
 }
 
 func tstWorkflowCancel(t *testing.T) error {
diff --git a/go/vt/proto/tabletmanagerdata/tabletmanagerdata.pb.go b/go/vt/proto/tabletmanagerdata/tabletmanagerdata.pb.go
index 3de3681a896..50bc4bd0e72 100644
--- a/go/vt/proto/tabletmanagerdata/tabletmanagerdata.pb.go
+++ b/go/vt/proto/tabletmanagerdata/tabletmanagerdata.pb.go
@@ -5687,6 +5687,12 @@ func (x *VDiffOptions) GetReportOptions() *VDiffReportOptions {
 	return nil
 }
 
+// UpdateVReplicationWorkflowRequest is used to update an existing VReplication
+// workflow. Note that the following fields MUST have an explicit value provided
+// if you do NOT wish to update the existing value to the given type's ZeroValue:
+// cells, tablet_types, on_ddl, and state.
+// TODO: leverage the optional modifier for these fields rather than using SimulatedNull
+// values: https://github.com/vitessio/vitess/issues/15627
 type UpdateVReplicationWorkflowRequest struct {
 	state         protoimpl.MessageState
 	sizeCache     protoimpl.SizeCache
@@ -5698,7 +5704,6 @@ type UpdateVReplicationWorkflowRequest struct {
 	TabletSelectionPreference TabletSelectionPreference            `protobuf:"varint,4,opt,name=tablet_selection_preference,json=tabletSelectionPreference,proto3,enum=tabletmanagerdata.TabletSelectionPreference" json:"tablet_selection_preference,omitempty"`
 	OnDdl                     binlogdata.OnDDLAction               `protobuf:"varint,5,opt,name=on_ddl,json=onDdl,proto3,enum=binlogdata.OnDDLAction" json:"on_ddl,omitempty"`
 	State                     binlogdata.VReplicationWorkflowState `protobuf:"varint,6,opt,name=state,proto3,enum=binlogdata.VReplicationWorkflowState" json:"state,omitempty"`
-	Shards                    []string                             `protobuf:"bytes,7,rep,name=shards,proto3" json:"shards,omitempty"`
 }
 
 func (x *UpdateVReplicationWorkflowRequest) Reset() {
@@ -5775,13 +5780,6 @@ func (x *UpdateVReplicationWorkflowRequest) GetState() binlogdata.VReplicationWo
 	return binlogdata.VReplicationWorkflowState(0)
 }
 
-func (x *UpdateVReplicationWorkflowRequest) GetShards() []string {
-	if x != nil {
-		return x.Shards
-	}
-	return nil
-}
-
 type UpdateVReplicationWorkflowResponse struct {
 	state         protoimpl.MessageState
 	sizeCache     protoimpl.SizeCache
@@ -6889,7 +6887,7 @@ var file_tabletmanagerdata_proto_rawDesc = []byte{
 	0x18, 0x03, 0x20, 0x01, 0x28, 0x0b, 0x32, 0x25, 0x2e, 0x74, 0x61, 0x62, 0x6c, 0x65, 0x74, 0x6d,
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@@ -6912,42 +6910,41 @@ var file_tabletmanagerdata_proto_rawDesc = []byte{
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+	0x07, 0x55, 0x4e, 0x4b, 0x4e, 0x4f, 0x57, 0x4e, 0x10, 0x03, 0x42, 0x30, 0x5a, 0x2e, 0x76, 0x69,
+	0x74, 0x65, 0x73, 0x73, 0x2e, 0x69, 0x6f, 0x2f, 0x76, 0x69, 0x74, 0x65, 0x73, 0x73, 0x2f, 0x67,
+	0x6f, 0x2f, 0x76, 0x74, 0x2f, 0x70, 0x72, 0x6f, 0x74, 0x6f, 0x2f, 0x74, 0x61, 0x62, 0x6c, 0x65,
+	0x74, 0x6d, 0x61, 0x6e, 0x61, 0x67, 0x65, 0x72, 0x64, 0x61, 0x74, 0x61, 0x62, 0x06, 0x70, 0x72,
+	0x6f, 0x74, 0x6f, 0x33,
 }
 
 var (
diff --git a/go/vt/proto/tabletmanagerdata/tabletmanagerdata_vtproto.pb.go b/go/vt/proto/tabletmanagerdata/tabletmanagerdata_vtproto.pb.go
index 4d5b4188e5e..c03bdb152f3 100644
--- a/go/vt/proto/tabletmanagerdata/tabletmanagerdata_vtproto.pb.go
+++ b/go/vt/proto/tabletmanagerdata/tabletmanagerdata_vtproto.pb.go
@@ -2159,11 +2159,6 @@ func (m *UpdateVReplicationWorkflowRequest) CloneVT() *UpdateVReplicationWorkflo
 		copy(tmpContainer, rhs)
 		r.TabletTypes = tmpContainer
 	}
-	if rhs := m.Shards; rhs != nil {
-		tmpContainer := make([]string, len(rhs))
-		copy(tmpContainer, rhs)
-		r.Shards = tmpContainer
-	}
 	if len(m.unknownFields) > 0 {
 		r.unknownFields = make([]byte, len(m.unknownFields))
 		copy(r.unknownFields, m.unknownFields)
@@ -7435,15 +7430,6 @@ func (m *UpdateVReplicationWorkflowRequest) MarshalToSizedBufferVT(dAtA []byte)
 		i -= len(m.unknownFields)
 		copy(dAtA[i:], m.unknownFields)
 	}
-	if len(m.Shards) > 0 {
-		for iNdEx := len(m.Shards) - 1; iNdEx >= 0; iNdEx-- {
-			i -= len(m.Shards[iNdEx])
-			copy(dAtA[i:], m.Shards[iNdEx])
-			i = encodeVarint(dAtA, i, uint64(len(m.Shards[iNdEx])))
-			i--
-			dAtA[i] = 0x3a
-		}
-	}
 	if m.State != 0 {
 		i = encodeVarint(dAtA, i, uint64(m.State))
 		i--
@@ -9587,12 +9573,6 @@ func (m *UpdateVReplicationWorkflowRequest) SizeVT() (n int) {
 	if m.State != 0 {
 		n += 1 + sov(uint64(m.State))
 	}
-	if len(m.Shards) > 0 {
-		for _, s := range m.Shards {
-			l = len(s)
-			n += 1 + l + sov(uint64(l))
-		}
-	}
 	n += len(m.unknownFields)
 	return n
 }
@@ -21105,38 +21085,6 @@ func (m *UpdateVReplicationWorkflowRequest) UnmarshalVT(dAtA []byte) error {
 					break
 				}
 			}
-		case 7:
-			if wireType != 2 {
-				return fmt.Errorf("proto: wrong wireType = %d for field Shards", wireType)
-			}
-			var stringLen uint64
-			for shift := uint(0); ; shift += 7 {
-				if shift >= 64 {
-					return ErrIntOverflow
-				}
-				if iNdEx >= l {
-					return io.ErrUnexpectedEOF
-				}
-				b := dAtA[iNdEx]
-				iNdEx++
-				stringLen |= uint64(b&0x7F) << shift
-				if b < 0x80 {
-					break
-				}
-			}
-			intStringLen := int(stringLen)
-			if intStringLen < 0 {
-				return ErrInvalidLength
-			}
-			postIndex := iNdEx + intStringLen
-			if postIndex < 0 {
-				return ErrInvalidLength
-			}
-			if postIndex > l {
-				return io.ErrUnexpectedEOF
-			}
-			m.Shards = append(m.Shards, string(dAtA[iNdEx:postIndex]))
-			iNdEx = postIndex
 		default:
 			iNdEx = preIndex
 			skippy, err := skip(dAtA[iNdEx:])
diff --git a/go/vt/vtctl/vtctl.go b/go/vt/vtctl/vtctl.go
index 919783e2f76..324cdda0a76 100644
--- a/go/vt/vtctl/vtctl.go
+++ b/go/vt/vtctl/vtctl.go
@@ -3829,6 +3829,7 @@ func commandWorkflow(ctx context.Context, wr *wrangler.Wrangler, subFlags *pflag
 				TabletTypes:               tabletTypes,
 				TabletSelectionPreference: tsp,
 				OnDdl:                     binlogdatapb.OnDDLAction(onddl),
+				State:                     binlogdatapb.VReplicationWorkflowState(textutil.SimulatedNullInt), // We don't allow changing this in the client command
 			}
 		}
 		results, err = wr.WorkflowAction(ctx, workflow, keyspace, action, *dryRun, rpcReq, *shards) // Only update currently uses the new RPC path
diff --git a/go/vt/vtctl/workflow/server.go b/go/vt/vtctl/workflow/server.go
index af0f16b2138..635d47d8bf2 100644
--- a/go/vt/vtctl/workflow/server.go
+++ b/go/vt/vtctl/workflow/server.go
@@ -2235,10 +2235,8 @@ func (s *Server) WorkflowUpdate(ctx context.Context, req *vtctldatapb.WorkflowUp
 	span.Annotate("tablet_types", req.TabletRequest.TabletTypes)
 	span.Annotate("on_ddl", req.TabletRequest.OnDdl)
 	span.Annotate("state", req.TabletRequest.State)
-	span.Annotate("shards", req.TabletRequest.Shards)
 
 	vx := vexec.NewVExec(req.Keyspace, req.TabletRequest.Workflow, s.ts, s.tmc, s.env.Parser())
-	vx.SetShardSubset(req.TabletRequest.Shards)
 	callback := func(ctx context.Context, tablet *topo.TabletInfo) (*querypb.QueryResult, error) {
 		res, err := s.tmc.UpdateVReplicationWorkflow(ctx, tablet.Tablet, req.TabletRequest)
 		if err != nil {
diff --git a/go/vt/vttablet/tabletmanager/rpc_vreplication.go b/go/vt/vttablet/tabletmanager/rpc_vreplication.go
index 02c2eb10056..a9ce8b841a5 100644
--- a/go/vt/vttablet/tabletmanager/rpc_vreplication.go
+++ b/go/vt/vttablet/tabletmanager/rpc_vreplication.go
@@ -257,6 +257,7 @@ func (tm *TabletManager) UpdateVReplicationWorkflow(ctx context.Context, req *ta
 		return &tabletmanagerdatapb.UpdateVReplicationWorkflowResponse{Result: nil}, nil
 	}
 
+	rowsAffected := uint64(0)
 	for _, row := range res.Named().Rows {
 		id := row.AsInt64("id", 0)
 		cells := strings.Split(row.AsString("cell", ""), ",")
@@ -317,11 +318,12 @@ func (tm *TabletManager) UpdateVReplicationWorkflow(ctx context.Context, req *ta
 		if err != nil {
 			return nil, err
 		}
+		rowsAffected += res.RowsAffected
 	}
 
 	return &tabletmanagerdatapb.UpdateVReplicationWorkflowResponse{
 		Result: &querypb.QueryResult{
-			RowsAffected: uint64(len(res.Rows)),
+			RowsAffected: rowsAffected,
 		},
 	}, nil
 }
diff --git a/proto/tabletmanagerdata.proto b/proto/tabletmanagerdata.proto
index e1a0e97f03e..f33cb4914ed 100644
--- a/proto/tabletmanagerdata.proto
+++ b/proto/tabletmanagerdata.proto
@@ -631,6 +631,12 @@ message VDiffOptions {
   VDiffReportOptions report_options = 3;
 }
 
+// UpdateVReplicationWorkflowRequest is used to update an existing VReplication
+// workflow. Note that the following fields MUST have an explicit value provided
+// if you do NOT wish to update the existing value to the given type's ZeroValue:
+// cells, tablet_types, on_ddl, and state.
+// TODO: leverage the optional modifier for these fields rather than using SimulatedNull
+// values: https://github.com/vitessio/vitess/issues/15627
 message UpdateVReplicationWorkflowRequest {
   string workflow = 1;
   repeated string cells = 2;
@@ -638,7 +644,7 @@ message UpdateVReplicationWorkflowRequest {
   TabletSelectionPreference tablet_selection_preference = 4;
   binlogdata.OnDDLAction on_ddl = 5;
   binlogdata.VReplicationWorkflowState state = 6;
-  repeated string shards = 7;
+  reserved 7; // unused, was: repeated string shards
 }
 
 message UpdateVReplicationWorkflowResponse {
diff --git a/web/vtadmin/src/proto/vtadmin.d.ts b/web/vtadmin/src/proto/vtadmin.d.ts
index 53fc9df7e7f..69f7891e271 100644
--- a/web/vtadmin/src/proto/vtadmin.d.ts
+++ b/web/vtadmin/src/proto/vtadmin.d.ts
@@ -28927,9 +28927,6 @@ export namespace tabletmanagerdata {
 
         /** UpdateVReplicationWorkflowRequest state */
         state?: (binlogdata.VReplicationWorkflowState|null);
-
-        /** UpdateVReplicationWorkflowRequest shards */
-        shards?: (string[]|null);
     }
 
     /** Represents an UpdateVReplicationWorkflowRequest. */
@@ -28959,9 +28956,6 @@ export namespace tabletmanagerdata {
         /** UpdateVReplicationWorkflowRequest state. */
         public state: binlogdata.VReplicationWorkflowState;
 
-        /** UpdateVReplicationWorkflowRequest shards. */
-        public shards: string[];
-
         /**
          * Creates a new UpdateVReplicationWorkflowRequest instance using the specified properties.
          * @param [properties] Properties to set
diff --git a/web/vtadmin/src/proto/vtadmin.js b/web/vtadmin/src/proto/vtadmin.js
index fc8c6a862fe..3263bc3eb51 100644
--- a/web/vtadmin/src/proto/vtadmin.js
+++ b/web/vtadmin/src/proto/vtadmin.js
@@ -66687,7 +66687,6 @@ export const tabletmanagerdata = $root.tabletmanagerdata = (() => {
          * @property {tabletmanagerdata.TabletSelectionPreference|null} [tablet_selection_preference] UpdateVReplicationWorkflowRequest tablet_selection_preference
          * @property {binlogdata.OnDDLAction|null} [on_ddl] UpdateVReplicationWorkflowRequest on_ddl
          * @property {binlogdata.VReplicationWorkflowState|null} [state] UpdateVReplicationWorkflowRequest state
-         * @property {Array.<string>|null} [shards] UpdateVReplicationWorkflowRequest shards
          */
 
         /**
@@ -66701,7 +66700,6 @@ export const tabletmanagerdata = $root.tabletmanagerdata = (() => {
         function UpdateVReplicationWorkflowRequest(properties) {
             this.cells = [];
             this.tablet_types = [];
-            this.shards = [];
             if (properties)
                 for (let keys = Object.keys(properties), i = 0; i < keys.length; ++i)
                     if (properties[keys[i]] != null)
@@ -66756,14 +66754,6 @@ export const tabletmanagerdata = $root.tabletmanagerdata = (() => {
          */
         UpdateVReplicationWorkflowRequest.prototype.state = 0;
 
-        /**
-         * UpdateVReplicationWorkflowRequest shards.
-         * @member {Array.<string>} shards
-         * @memberof tabletmanagerdata.UpdateVReplicationWorkflowRequest
-         * @instance
-         */
-        UpdateVReplicationWorkflowRequest.prototype.shards = $util.emptyArray;
-
         /**
          * Creates a new UpdateVReplicationWorkflowRequest instance using the specified properties.
          * @function create
@@ -66805,9 +66795,6 @@ export const tabletmanagerdata = $root.tabletmanagerdata = (() => {
                 writer.uint32(/* id 5, wireType 0 =*/40).int32(message.on_ddl);
             if (message.state != null && Object.hasOwnProperty.call(message, "state"))
                 writer.uint32(/* id 6, wireType 0 =*/48).int32(message.state);
-            if (message.shards != null && message.shards.length)
-                for (let i = 0; i < message.shards.length; ++i)
-                    writer.uint32(/* id 7, wireType 2 =*/58).string(message.shards[i]);
             return writer;
         };
 
@@ -66875,12 +66862,6 @@ export const tabletmanagerdata = $root.tabletmanagerdata = (() => {
                         message.state = reader.int32();
                         break;
                     }
-                case 7: {
-                        if (!(message.shards && message.shards.length))
-                            message.shards = [];
-                        message.shards.push(reader.string());
-                        break;
-                    }
                 default:
                     reader.skipType(tag & 7);
                     break;
@@ -66979,13 +66960,6 @@ export const tabletmanagerdata = $root.tabletmanagerdata = (() => {
                 case 6:
                     break;
                 }
-            if (message.shards != null && message.hasOwnProperty("shards")) {
-                if (!Array.isArray(message.shards))
-                    return "shards: array expected";
-                for (let i = 0; i < message.shards.length; ++i)
-                    if (!$util.isString(message.shards[i]))
-                        return "shards: string[] expected";
-            }
             return null;
         };
 
@@ -67147,13 +67121,6 @@ export const tabletmanagerdata = $root.tabletmanagerdata = (() => {
                 message.state = 6;
                 break;
             }
-            if (object.shards) {
-                if (!Array.isArray(object.shards))
-                    throw TypeError(".tabletmanagerdata.UpdateVReplicationWorkflowRequest.shards: array expected");
-                message.shards = [];
-                for (let i = 0; i < object.shards.length; ++i)
-                    message.shards[i] = String(object.shards[i]);
-            }
             return message;
         };
 
@@ -67173,7 +67140,6 @@ export const tabletmanagerdata = $root.tabletmanagerdata = (() => {
             if (options.arrays || options.defaults) {
                 object.cells = [];
                 object.tablet_types = [];
-                object.shards = [];
             }
             if (options.defaults) {
                 object.workflow = "";
@@ -67199,11 +67165,6 @@ export const tabletmanagerdata = $root.tabletmanagerdata = (() => {
                 object.on_ddl = options.enums === String ? $root.binlogdata.OnDDLAction[message.on_ddl] === undefined ? message.on_ddl : $root.binlogdata.OnDDLAction[message.on_ddl] : message.on_ddl;
             if (message.state != null && message.hasOwnProperty("state"))
                 object.state = options.enums === String ? $root.binlogdata.VReplicationWorkflowState[message.state] === undefined ? message.state : $root.binlogdata.VReplicationWorkflowState[message.state] : message.state;
-            if (message.shards && message.shards.length) {
-                object.shards = [];
-                for (let j = 0; j < message.shards.length; ++j)
-                    object.shards[j] = message.shards[j];
-            }
             return object;
         };