diff --git a/packages/boot/tools/supports.ts b/packages/boot/tools/supports.ts
index 36af57d01ccc..339f422b991c 100644
--- a/packages/boot/tools/supports.ts
+++ b/packages/boot/tools/supports.ts
@@ -46,6 +46,10 @@ import type { SwingsetController } from '@agoric/swingset-vat/src/controller/con
 import type { BridgeHandler, IBCMethod, IBCPacket } from '@agoric/vats';
 import type { BootstrapRootObject } from '@agoric/vats/src/core/lib-boot.js';
 import type { EProxy } from '@endo/eventual-send';
+import {
+  buildVTransferEvent,
+  type BuildVTransferEventParams,
+} from '@agoric/orchestration/tools/ibc-mocks.js';
 import { icaMocks, protoMsgMockMap, protoMsgMocks } from './ibc/mocks.js';
 
 const trace = makeTracer('BSTSupport', false);
@@ -615,6 +619,13 @@ export const makeSwingsetTestKit = async (
       console.log('🧻');
       return i;
     },
+
+    async inboundVTransferEvent(params: BuildVTransferEventParams) {
+      await runUtils.queueAndRun(
+        () => inbound(BridgeId.VTRANSFER, buildVTransferEvent(params)),
+        true,
+      );
+    },
   };
 
   return {
diff --git a/packages/orchestration/tools/ibc-mocks.ts b/packages/orchestration/tools/ibc-mocks.ts
index 65266645e5d0..6933bef394e8 100644
--- a/packages/orchestration/tools/ibc-mocks.ts
+++ b/packages/orchestration/tools/ibc-mocks.ts
@@ -6,7 +6,7 @@ import {
   ResponseQuery,
 } from '@agoric/cosmic-proto/tendermint/abci/types.js';
 import { encodeBase64, btoa, atob, decodeBase64 } from '@endo/base64';
-import { toRequestQueryJson } from '@agoric/cosmic-proto';
+import { type JsonSafe, toRequestQueryJson } from '@agoric/cosmic-proto';
 import {
   IBCChannelID,
   IBCEvent,
@@ -152,18 +152,19 @@ export function buildQueryPacketString(
   return btoa(makeQueryPacket(msgs.map(msg => toRequestQueryJson(msg, opts))));
 }
 
-type BuildVTransferEventParams = {
+export type BuildVTransferEventParams = {
   event?: VTransferIBCEvent['event'];
   /* defaults to cosmos1AccAddress. set to `agoric1fakeLCAAddress` to simulate an outgoing transfer event */
   sender?: ChainAddress['value'];
-  /**  defaults to agoric1fakeLCAAddress. set to a different value to simulate an outgoing transfer event */
+  /*  defaults to agoric1fakeLCAAddress. set to a different value to simulate an outgoing transfer event */
   receiver?: ChainAddress['value'];
   target?: ChainAddress['value'];
   amount?: bigint;
   denom?: string;
   destinationChannel?: IBCChannelID;
   sourceChannel?: IBCChannelID;
-  sequence?: PacketSDKType['sequence'];
+  /* support bigint and string, to facilitate bootstrap testing */
+  sequence?: PacketSDKType['sequence'] | JsonSafe<PacketSDKType['sequence']>;
 };
 
 /**