diff --git a/multichain-testing/test/auto-stake-it.test.ts b/multichain-testing/test/auto-stake-it.test.ts
index 1c185c588b7..29b984ceec0 100644
--- a/multichain-testing/test/auto-stake-it.test.ts
+++ b/multichain-testing/test/auto-stake-it.test.ts
@@ -27,8 +27,8 @@ test.before(async t => {
   t.context = { ...common, wallets };
 
   await startContract(contractName, contractBuilder, {
-    chainInfo: JSON.stringify(chainInfo),
-    assetInfo: JSON.stringify(assetInfo),
+    chainInfo,
+    assetInfo,
   });
 });
 
diff --git a/multichain-testing/test/basic-flows.test.ts b/multichain-testing/test/basic-flows.test.ts
index 658ce851d67..689db323524 100644
--- a/multichain-testing/test/basic-flows.test.ts
+++ b/multichain-testing/test/basic-flows.test.ts
@@ -22,8 +22,8 @@ test.before(async t => {
   const wallets = await setupTestKeys(accounts);
   t.context = { ...common, wallets };
   await startContract(contractName, contractBuilder, {
-    chainInfo: JSON.stringify(chainInfo),
-    assetInfo: JSON.stringify(assetInfo),
+    chainInfo,
+    assetInfo,
   });
 });
 
diff --git a/multichain-testing/test/deposit-withdraw-lca.test.ts b/multichain-testing/test/deposit-withdraw-lca.test.ts
index 226b29d45dd..ad7fd4824d9 100644
--- a/multichain-testing/test/deposit-withdraw-lca.test.ts
+++ b/multichain-testing/test/deposit-withdraw-lca.test.ts
@@ -20,8 +20,8 @@ test.before(async t => {
   const wallets = await setupTestKeys(accounts);
   t.context = { ...common, wallets };
   await startContract(contractName, contractBuilder, {
-    chainInfo: JSON.stringify(chainInfo),
-    assetInfo: JSON.stringify(assetInfo),
+    chainInfo,
+    assetInfo,
   });
 });
 
diff --git a/multichain-testing/test/deposit-withdraw-portfolio.test.ts b/multichain-testing/test/deposit-withdraw-portfolio.test.ts
index afd484284b8..ea97f1e7f17 100644
--- a/multichain-testing/test/deposit-withdraw-portfolio.test.ts
+++ b/multichain-testing/test/deposit-withdraw-portfolio.test.ts
@@ -20,8 +20,8 @@ test.before(async t => {
   const wallets = await setupTestKeys(accounts);
   t.context = { ...common, wallets };
   await startContract(contractName, contractBuilder, {
-    chainInfo: JSON.stringify(chainInfo),
-    assetInfo: JSON.stringify(assetInfo),
+    chainInfo,
+    assetInfo,
   });
 });
 
diff --git a/multichain-testing/test/ica-channel-close.test.ts b/multichain-testing/test/ica-channel-close.test.ts
index ab7437da525..03b0ef9ac95 100644
--- a/multichain-testing/test/ica-channel-close.test.ts
+++ b/multichain-testing/test/ica-channel-close.test.ts
@@ -28,8 +28,8 @@ test.before(async t => {
   const wallets = await setupTestKeys(accounts);
   t.context = { ...common, wallets };
   await startContract(contractName, contractBuilder, {
-    chainInfo: JSON.stringify(chainInfo),
-    assetInfo: JSON.stringify(assetInfo),
+    chainInfo,
+    assetInfo,
   });
 });
 
diff --git a/multichain-testing/test/send-anywhere.test.ts b/multichain-testing/test/send-anywhere.test.ts
index ba74b23338a..f1a8a720e5f 100644
--- a/multichain-testing/test/send-anywhere.test.ts
+++ b/multichain-testing/test/send-anywhere.test.ts
@@ -27,8 +27,8 @@ test.before(async t => {
   t.context = { ...common, wallets };
 
   await startContract(contractName, contractBuilder, {
-    chainInfo: JSON.stringify(chainInfo),
-    assetInfo: JSON.stringify(assetInfo),
+    chainInfo,
+    assetInfo,
   });
 });
 
diff --git a/multichain-testing/test/support.ts b/multichain-testing/test/support.ts
index aef2bfab173..f3f8e752d96 100644
--- a/multichain-testing/test/support.ts
+++ b/multichain-testing/test/support.ts
@@ -4,6 +4,7 @@ import { execa } from 'execa';
 import fse from 'fs-extra';
 import childProcess from 'node:child_process';
 import { withChainCapabilities } from '@agoric/orchestration';
+import { objectMap } from '@endo/patterns';
 import { makeAgdTools } from '../tools/agd-tools.js';
 import { type E2ETools } from '../tools/e2e-tools.js';
 import {
@@ -94,7 +95,7 @@ export const commonSetup = async (t: ExecutionContext) => {
   const startContract = async (
     contractName: string,
     contractBuilder: string,
-    builderOpts?: Record<string, string>,
+    builderOpts?: Record<string, unknown>,
   ) => {
     const { vstorageClient } = tools;
     const instances = Object.fromEntries(
@@ -104,7 +105,18 @@ export const commonSetup = async (t: ExecutionContext) => {
       return t.log('Contract found. Skipping installation...');
     }
     t.log('bundle and install contract', contractName);
-    await deployBuilder(contractBuilder, builderOpts);
+
+    const formattedOpts = builderOpts
+      ? objectMap(
+          // eslint-disable-next-line @typescript-eslint/no-explicit-any
+          builderOpts as Record<string, any>,
+          value => {
+            if (typeof value === 'string') return value;
+            return JSON.stringify(value);
+          },
+        )
+      : undefined;
+    await deployBuilder(contractBuilder, formattedOpts);
     await retryUntilCondition(
       () => vstorageClient.queryData(`published.agoricNames.instance`),
       res => contractName in Object.fromEntries(res),