diff --git a/packages/ERTP/src/interfaces.js b/packages/ERTP/src/interfaces.js
index 35ebaf68ca78..6e31ead19f1c 100644
--- a/packages/ERTP/src/interfaces.js
+++ b/packages/ERTP/src/interfaces.js
@@ -1,6 +1,5 @@
 /* eslint-disable no-use-before-define */
-/* global foo */
-const M = foo();
+import { M, I } from '@agoric/store';
 
 export const MatchDisplayInfo = M.rest(
   {
@@ -10,10 +9,10 @@ export const MatchDisplayInfo = M.rest(
   }),
 );
 
-export const BrandI = M.interface({
-  isMyIssuer: M.callWhen(M.await(IssuerI)).returns(M.boolean()),
-  getAllegedName: M.call().returns(M.string()),
-  getDisplayInfo: M.call().returns(MatchDisplayInfo),
+export const BrandI = I.interface('Brand', {
+  isMyIssuer: I.callWhen(I.await(IssuerI)).returns(M.boolean()),
+  getAllegedName: I.call().returns(M.string()),
+  getDisplayInfo: I.call().returns(MatchDisplayInfo),
 });
 
 export const MatchAmount = {
@@ -21,25 +20,25 @@ export const MatchAmount = {
   value: M.or(M.bigint(), M.array()),
 };
 
-export const IssuerI = M.interface({
-  getBrand: M.call().returns(BrandI),
-  getAllegedName: M.call().returns(M.string()),
-  getAssetKind: M.call().returns(M.or('nat', 'set')),
-  getDisplayInfo: M.call().returns(MatchDisplayInfo),
-  makeEmptyPurse: M.call().returns(PurseI),
+export const IssuerI = I.interface('Issuer', {
+  getBrand: I.call().returns(BrandI),
+  getAllegedName: I.call().returns(M.string()),
+  getAssetKind: I.call().returns(M.or('nat', 'set')),
+  getDisplayInfo: I.call().returns(MatchDisplayInfo),
+  makeEmptyPurse: I.call().returns(PurseI),
 
-  isLive: M.callWhen(M.await(PaymentI)).returns(M.boolean()),
-  getAmountOf: M.callWhen(M.await(PaymentI)).returns(MatchAmount),
+  isLive: I.callWhen(I.await(PaymentI)).returns(M.boolean()),
+  getAmountOf: I.callWhen(I.await(PaymentI)).returns(MatchAmount),
 });
 
-export const PaymentI = M.interface({
-  getAllegedBrand: M.call().returns(BrandI),
+export const PaymentI = I.interface('Payment', {
+  getAllegedBrand: I.call().returns(BrandI),
 });
 
-export const PurseI = M.interface({
-  getAllegedBrand: M.call().returns(BrandI),
-  deposit: M.apply(M.rest([PaymentI]).optionals([MatchAmount])).returns(
+export const PurseI = I.interface('Purse', {
+  getAllegedBrand: I.call().returns(BrandI),
+  deposit: I.apply(M.rest([PaymentI], M.partial([MatchAmount]))).returns(
     MatchAmount,
   ),
-  withdraw: M.call(MatchAmount).returns(PaymentI),
+  withdraw: I.call(MatchAmount).returns(PaymentI),
 });
diff --git a/packages/ERTP/src/paymentLedger.js b/packages/ERTP/src/paymentLedger.js
index 33331690d617..da2ed22be9d7 100644
--- a/packages/ERTP/src/paymentLedger.js
+++ b/packages/ERTP/src/paymentLedger.js
@@ -509,4 +509,4 @@ export const vivifyPaymentLedger = (
 };
 harden(vivifyPaymentLedger);
 
-/** @typedef {ReturnType<vivifyPaymentLedger>} PaymentLedger */
+/** @typedef {ReturnType<typeof vivifyPaymentLedger>} PaymentLedger */
diff --git a/packages/store/src/index.js b/packages/store/src/index.js
index c54a88363872..07fe0146de32 100755
--- a/packages/store/src/index.js
+++ b/packages/store/src/index.js
@@ -55,6 +55,7 @@ export {
   matches,
   fit,
 } from './patterns/patternMatchers.js';
+export { I } from './patterns/interface-tools.js';
 export { compareRank, isRankSorted, sortByRank } from './patterns/rankOrder.js';
 export {
   makeDecodePassable,
diff --git a/packages/store/src/patterns/defineHeapKind.js b/packages/store/src/patterns/defineHeapKind.js
new file mode 100644
index 000000000000..1c7af8bca716
--- /dev/null
+++ b/packages/store/src/patterns/defineHeapKind.js
@@ -0,0 +1,37 @@
+import { makeLegacyWeakMap } from '../legacy/legacyWeakMap.js';
+import { defendVTable } from './interface-tools.js';
+
+const { create, freeze, seal } = Object;
+
+export const defineHeapKind = (
+  ifaceGuard,
+  init,
+  rawVTable,
+  { finish = undefined } = {},
+) => {
+  if (typeof ifaceGuard === 'string') {
+    ifaceGuard = harden({
+      klass: 'Interface',
+      farName: ifaceGuard,
+      methodGuards: {},
+    });
+  }
+  const { klass } = ifaceGuard;
+  assert(klass === 'Interface');
+  // legacyWeakMap to avoid hardening state
+  const contextMapStore = makeLegacyWeakMap();
+  const defensiveVTable = defendVTable(rawVTable, contextMapStore, ifaceGuard);
+  const makeInstance = (...args) => {
+    // Don't freeze state
+    const state = seal(init(...args));
+    const self = harden(create(defensiveVTable));
+    const context = freeze({ state, self });
+    contextMapStore.init(self, context);
+    if (finish) {
+      finish(context);
+    }
+    return self;
+  };
+  return harden(makeInstance);
+};
+harden(defineHeapKind);
diff --git a/packages/store/src/patterns/interface-tools.js b/packages/store/src/patterns/interface-tools.js
new file mode 100644
index 000000000000..a8ae2b77d785
--- /dev/null
+++ b/packages/store/src/patterns/interface-tools.js
@@ -0,0 +1,179 @@
+import { PASS_STYLE, assertRemotable } from '@endo/marshal';
+import { E } from '@endo/eventual-send';
+import { M, fit } from './patternMatchers.js';
+
+const { details: X, quote: q } = assert;
+const { apply, ownKeys } = Reflect;
+const { fromEntries, entries, create, setPrototypeOf, defineProperties } =
+  Object;
+
+const makeMethodGuardMaker = (callKind, argGuards) =>
+  harden({
+    returns: (returnGuard = M.undefined()) =>
+      harden({
+        klass: 'methodGuard',
+        callKind,
+        argGuards,
+        returnGuard,
+      }),
+  });
+
+const makeAwaitArgGuard = argGuard =>
+  harden({
+    klass: 'awaitArg',
+    argGuard,
+  });
+
+const isAwaitArgGuard = argGuard =>
+  argGuard && typeof argGuard === 'object' && argGuard.klass === 'awaitArg';
+
+export const I = harden({
+  interface: (farName, methodGuards) => {
+    for (const [_, methodGuard] of entries(methodGuards)) {
+      assert(
+        methodGuard.klass === 'methodGuard',
+        X`unrecognize method guard ${methodGuard}`,
+      );
+    }
+    return harden({
+      klass: 'Interface',
+      farName,
+      methodGuards,
+    });
+  },
+  call: (...argGuards) => makeMethodGuardMaker('sync', argGuards),
+  callWhen: (...argGuards) => makeMethodGuardMaker('async', argGuards),
+  apply: argGuards => makeMethodGuardMaker('sync', argGuards),
+  applyWhen: argGuards => makeMethodGuardMaker('async', argGuards),
+
+  await: argGuard => makeAwaitArgGuard(argGuard),
+});
+
+const mimicMethodNameLength = (defensiveMethod, rawMethod) => {
+  defineProperties(defensiveMethod, {
+    name: { value: rawMethod.name },
+    length: { value: rawMethod.length - 1 },
+  });
+};
+
+const defendSyncMethod = (rawMethod, contextMapStore, methodGuard, label) => {
+  const { argGuards, returnGuard } = methodGuard;
+
+  const { defensiveSyncMethod } = {
+    // Note purposeful use of `this` and concise method syntax
+    defensiveSyncMethod(...args) {
+      assert(
+        contextMapStore.has(this),
+        X`method can only be used on its own instances: ${rawMethod}`,
+      );
+      const context = contextMapStore.get(this);
+      fit(harden(args), argGuards, `${label}: args`);
+      const result = apply(rawMethod, undefined, [context, ...args]);
+      fit(result, returnGuard, `${label}: result`);
+      return result;
+    },
+  };
+  mimicMethodNameLength(defensiveSyncMethod, rawMethod);
+  return harden(defensiveSyncMethod);
+};
+
+const defendAsyncMethod = (rawMethod, contextMapStore, methodGuard, label) => {
+  const { argGuards, returnGuard } = methodGuard;
+
+  const rawArgGuards = [];
+  const awaitIndexes = [];
+  for (let i = 0; i < argGuards.length; i += 1) {
+    const argGuard = argGuards[i];
+    if (isAwaitArgGuard(argGuard)) {
+      rawArgGuards.push(argGuard.argGuard);
+      awaitIndexes.push(i);
+    } else {
+      rawArgGuards.push(argGuard);
+    }
+  }
+  harden(rawArgGuards);
+  harden(awaitIndexes);
+  const { defensiveAsyncMethod } = {
+    // Note purposeful use of `this` and concise method syntax
+    defensiveAsyncMethod(...args) {
+      assert(
+        contextMapStore.has(this),
+        X`method can only be used on its own instances: ${rawMethod}`,
+      );
+      const context = contextMapStore.get(this);
+      const awaitList = awaitIndexes.map(i => args[i]);
+      const p = Promise.all(awaitList);
+      const rawArgs = [...args];
+      return E.when(p, awaitedArgs => {
+        for (let j = 0; j < awaitIndexes.length; j += 1) {
+          rawArgs[awaitIndexes[j]] = awaitedArgs[j];
+        }
+        fit(harden(rawArgs), rawArgGuards, `${label}: args`);
+        const resultP = apply(rawMethod, undefined, [context, ...rawArgs]);
+        return E.when(resultP, result => {
+          fit(result, returnGuard, `${label}: result`);
+          return result;
+        });
+      });
+    },
+  };
+  mimicMethodNameLength(defensiveAsyncMethod, rawMethod);
+  return harden(defensiveAsyncMethod);
+};
+
+const defendMethod = (rawMethod, contextMapStore, methodGuard, label) => {
+  const { klass, callKind } = methodGuard;
+  assert(klass === 'methodGuard');
+
+  if (callKind === 'sync') {
+    return defendSyncMethod(rawMethod, contextMapStore, methodGuard, label);
+  } else {
+    assert(callKind === 'async');
+    return defendAsyncMethod(rawMethod, contextMapStore, methodGuard, label);
+  }
+};
+
+const defaultMethodGuard = I.apply(M.array()).returns();
+
+export const defendVTable = (rawVTable, contextMapStore, iface) => {
+  const { klass, farName, methodGuards } = iface;
+  assert(klass === 'Interface');
+  assert.typeof(farName, 'string');
+
+  const methodGuardNames = ownKeys(methodGuards);
+  for (const methodGuardName of methodGuardNames) {
+    assert(
+      methodGuardName in rawVTable,
+      X`${q(methodGuardName)} not implemented by ${rawVTable}`,
+    );
+  }
+  const methodNames = ownKeys(rawVTable);
+  // like Object.entries, but unenumerable and symbol as well.
+  const rawMethodEntries = methodNames.map(mName => [mName, rawVTable[mName]]);
+  const defensiveMethodEntries = rawMethodEntries.map(([mName, rawMethod]) => {
+    const methodGuard = methodGuards[mName] || defaultMethodGuard;
+    const defensiveMethod = defendMethod(
+      rawMethod,
+      contextMapStore,
+      methodGuard,
+      `${farName}.${mName}`,
+    );
+    return [mName, defensiveMethod];
+  });
+  // Return the defensive VTable, which can be use on a shared
+  // prototype and shared by instances, avoiding the per-object-per-method
+  // allocation cost of the objects as closure pattern. That's why we
+  // use `this` above. To make it safe, each defensive method starts with
+  // a fail-fast brand check on `this`, ensuring that the methods can only be
+  // applied to legitimate instances.
+  const defensiveVTable = fromEntries(defensiveMethodEntries);
+  const remotableProto = create(Object.prototype, {
+    [PASS_STYLE]: { value: 'remotable' },
+    [Symbol.toStringTag]: { value: `Alleged: ${farName}` },
+  });
+  setPrototypeOf(defensiveVTable, remotableProto);
+  harden(defensiveVTable);
+  assertRemotable(defensiveVTable);
+  return defensiveVTable;
+};
+harden(defendVTable);
diff --git a/packages/store/test/test-interface-tools.js b/packages/store/test/test-interface-tools.js
new file mode 100644
index 000000000000..83dbed5a45bb
--- /dev/null
+++ b/packages/store/test/test-interface-tools.js
@@ -0,0 +1,31 @@
+// @ts-check
+
+import { test } from '@agoric/swingset-vat/tools/prepare-test-env-ava.js';
+import { passStyleOf } from '@endo/marshal';
+
+import { I } from '../src/patterns/interface-tools.js';
+import { defineHeapKind } from '../src/patterns/defineHeapKind.js';
+import { M } from '../src/patterns/patternMatchers.js';
+
+test('how far-able is defineHeapKind', t => {
+  const bobIFace = I.interface('bob', {
+    foo: I.call(M.number()).returns(M.undefined()),
+  });
+  const makeBob = defineHeapKind(bobIFace, field => ({ field }), {
+    foo: ({ state, self }, carol) => {
+      t.is(state.field, 8);
+      t.is(typeof self.foo, 'function');
+      t.is(self.foo.name, 'foo');
+      t.is(self.foo.length, 1);
+      t.is(carol, 77);
+      state.field += carol;
+      t.is(state.field, 85);
+    },
+  });
+  const bob = makeBob(8);
+  t.is(passStyleOf(bob), 'remotable');
+  bob.foo(77);
+  t.throws(() => bob.foo(true), {
+    message: /^bob.foo: args: \[0\]: boolean true - Must be a number$/,
+  });
+});
diff --git a/packages/vat-data/src/kind-utils.js b/packages/vat-data/src/kind-utils.js
index fe2f21684f4c..2262b784eb3f 100644
--- a/packages/vat-data/src/kind-utils.js
+++ b/packages/vat-data/src/kind-utils.js
@@ -15,13 +15,14 @@ import {
 const { entries, fromEntries } = Object;
 
 /**
- * Make a version of the argument function that takes a kind context but ignores it.
+ * Make a version of the argument function that takes a kind context but
+ * ignores it.
  *
  * @type {<T extends Function>(fn: T) => import('./types.js').PlusContext<never, T>}
  */
 export const ignoreContext =
   fn =>
-  (context, ...args) =>
+  (_context, ...args) =>
     fn(...args);
 // @ts-expect-error TODO statically recognize harden
 harden(ignoreContext);
diff --git a/patches/@endo+marshal+0.6.9.patch b/patches/@endo+marshal+0.6.9.patch
new file mode 100644
index 000000000000..7cb9b4b8778c
--- /dev/null
+++ b/patches/@endo+marshal+0.6.9.patch
@@ -0,0 +1,36 @@
+diff --git a/node_modules/@endo/marshal/src/helpers/remotable.js b/node_modules/@endo/marshal/src/helpers/remotable.js
+index c19adca..645bf10 100644
+--- a/node_modules/@endo/marshal/src/helpers/remotable.js
++++ b/node_modules/@endo/marshal/src/helpers/remotable.js
+@@ -77,6 +77,22 @@ const checkRemotableProtoOf = (original, check = x => x) => {
+    *        }}
+    */
+   const proto = getPrototypeOf(original);
++
++  // From agoric-sdk patch in anticipation of
++  // https://github.com/endojs/endo/pull/1251
++  // TODO: once agoric-sdk is upgraded to depend on that PR, remove this patch.
++  const protoProto = getPrototypeOf(proto);
++  if (
++    typeof original === 'object' &&
++    proto !== objectPrototype &&
++    protoProto !== objectPrototype
++  ) {
++    return (
++      // eslint-disable-next-line no-use-before-define
++      RemotableHelper.canBeValid(proto, check) && checkRemotable(proto, check)
++    );
++  }
++
+   if (
+     !(
+       check(
+@@ -95,8 +111,6 @@ const checkRemotableProtoOf = (original, check = x => x) => {
+     return false;
+   }
+ 
+-  const protoProto = getPrototypeOf(proto);
+-
+   if (typeof original === 'object') {
+     if (
+       !check(