diff --git a/packages/base-zone/src/heap-exo-state.js b/packages/base-zone/src/heap-exo-state.js
new file mode 100644
index 00000000000..adfd8e47d4e
--- /dev/null
+++ b/packages/base-zone/src/heap-exo-state.js
@@ -0,0 +1,186 @@
+// @ts-check
+
+import { passStyleOf } from '@endo/pass-style';
+import { Fail, q } from '@endo/errors';
+import { M, mustMatch } from '@endo/patterns';
+import { assertPattern } from '@agoric/store';
+
+/**
+ * @import { StateShape } from '@endo/exo'
+ */
+
+const { hasOwn, defineProperty, getOwnPropertyNames } = Object;
+const { ownKeys } = Reflect;
+
+/**
+ * @param {any} [stateShape]
+ * @returns {asserts stateShape is (StateShape | undefined)}
+ */
+const assertStateShape = stateShape => {
+  harden(stateShape);
+  stateShape === undefined ||
+    passStyleOf(stateShape) === 'copyRecord' ||
+    Fail`A stateShape must be a copyRecord: ${q(stateShape)}`;
+  assertPattern(stateShape);
+};
+
+/**
+ * @param {StateShape} [stateShape]
+ */
+const provideCheckStatePropertyValue = stateShape => {
+  /** @type {(value: any, prop: string) => void} */
+  let checkStatePropertyValue = (value, _prop) => {
+    mustMatch(value, M.any());
+  };
+  if (stateShape) {
+    checkStatePropertyValue = (value, prop) => {
+      hasOwn(stateShape, prop) ||
+        Fail`State must only have fields described by stateShape: ${q(
+          ownKeys(stateShape),
+        )}`;
+      mustMatch(value, stateShape[prop]);
+    };
+  }
+  return checkStatePropertyValue;
+};
+
+/**
+ * @param {(state: object) => Record<string, any>} getStateData
+ * @param {ReturnType<typeof provideCheckStatePropertyValue>} checkStatePropertyValue
+ */
+const provideFieldDescriptorMaker = (getStateData, checkStatePropertyValue) => {
+  /** @param {string} prop */
+  const makeFieldDescriptor = prop => {
+    return harden({
+      get() {
+        const stateData = getStateData(this);
+        stateData || Fail`Invalid state object ${this}`;
+        return stateData[prop];
+      },
+      /** @param {any} value */
+      set(value) {
+        const stateData = getStateData(this);
+        stateData || Fail`Invalid state object ${this}`;
+        harden(value);
+        checkStatePropertyValue(value, prop);
+        stateData[prop] = value;
+      },
+      enumerable: true,
+      configurable: false,
+    });
+  };
+
+  return makeFieldDescriptor;
+};
+
+/**
+ * @param {StateShape} [stateShape]
+ */
+const provideStateMakerForShape = stateShape => {
+  class State {
+    /** @type {Record<string, any>} */
+    #data;
+
+    /** @param {State} state */
+    static getStateData(state) {
+      return state.#data;
+    }
+
+    /**
+     * @param {State} state
+     * @param {Record<string, any>} data
+     */
+    static setStateData(state, data) {
+      state.#data = data;
+    }
+  }
+
+  const { getStateData, setStateData } = State;
+  // @ts-expect-error
+  delete State.getStateData;
+  // @ts-expect-error
+  delete State.setStateData;
+
+  // Private maker
+  const makeState = () => {
+    const state = new State();
+    setStateData(state, {});
+    harden(state);
+    return /** @type {Record<string, any>} */ (state);
+  };
+
+  const checkStatePropertyValue = provideCheckStatePropertyValue(stateShape);
+  const makeFieldDescriptor = provideFieldDescriptorMaker(
+    getStateData,
+    checkStatePropertyValue,
+  );
+
+  for (const prop of getOwnPropertyNames(stateShape)) {
+    defineProperty(State.prototype, prop, makeFieldDescriptor(prop));
+  }
+  harden(State);
+
+  /**
+   * @template {Record<string, any>} T
+   * @param {T} initialData
+   */
+  return initialData => {
+    const state = makeState();
+    const stateOwnKeys = new Set(ownKeys(initialData));
+    for (const prop of getOwnPropertyNames(stateShape)) {
+      stateOwnKeys.delete(prop);
+      state[prop] = initialData[prop];
+    }
+    stateOwnKeys.size === 0 ||
+      Fail`Init returned keys not allowed by stateShape: ${[...stateOwnKeys]}`;
+    return /** @type {T} */ (state);
+  };
+};
+
+const provideStateMakerWithoutShape = () => {
+  const statePrototype = harden({});
+  const checkStatePropertyValue = provideCheckStatePropertyValue();
+
+  /** @param {object} expectedState */
+  const makeGetStateData = expectedState => {
+    /** @type {Record<string, any>} */
+    const stateData = {};
+    /** @param {object} state */
+    return state => {
+      expectedState === state || Fail`Unexpected state object ${state}`;
+      return stateData;
+    };
+  };
+
+  /**
+   * @template {Record<string, any>} T
+   * @param {T} initialData
+   */
+  return initialData => {
+    /** @type {Record<string, any>} */
+    const state = { __proto__: statePrototype };
+    const getStateData = makeGetStateData(state);
+    const makeFieldDescriptor = provideFieldDescriptorMaker(
+      getStateData,
+      checkStatePropertyValue,
+    );
+
+    for (const prop of ownKeys(initialData)) {
+      assert(typeof prop === 'string');
+      defineProperty(state, prop, makeFieldDescriptor(prop));
+      state[prop] = initialData[prop];
+    }
+    harden(state);
+    return /** @type {T} */ (state);
+  };
+};
+
+/**
+ * @param {StateShape} [stateShape]
+ */
+export const provideStateMaker = stateShape => {
+  assertStateShape(stateShape);
+  return stateShape
+    ? provideStateMakerForShape(stateShape)
+    : provideStateMakerWithoutShape();
+};
diff --git a/packages/base-zone/src/heap.js b/packages/base-zone/src/heap.js
index fe6a6a72918..2f3322a6b2c 100644
--- a/packages/base-zone/src/heap.js
+++ b/packages/base-zone/src/heap.js
@@ -2,7 +2,12 @@
 // @jessie-check
 
 import { Far, isPassable } from '@endo/pass-style';
-import { makeExo, defineExoClass, defineExoClassKit } from '@endo/exo';
+import { Fail } from '@endo/errors';
+import {
+  makeExo,
+  defineExoClass as rawDefineExoClass,
+  defineExoClassKit as rawDefineExoClassKit,
+} from '@endo/exo';
 import {
   makeScalarMapStore,
   makeScalarSetStore,
@@ -13,6 +18,11 @@ import {
 import { makeOnceKit } from './make-once.js';
 import { agoricVatDataKeys as keys } from './keys.js';
 import { watchPromise } from './watch-promise.js';
+import { provideStateMaker } from './heap-exo-state.js';
+
+/**
+ * @import {StateShape} from '@endo/exo'
+ */
 
 /**
  * @type {import('./types.js').Stores}
@@ -27,6 +37,62 @@ const detachedHeapStores = Far('heapStores', {
   weakSetStore: makeScalarWeakSetStore,
 });
 
+/**
+ * @template {(...args: any[]) => any} I
+ * @param {I} init
+ * @param {StateShape | undefined} stateShape
+ */
+const wrapExoInit = (init, stateShape) => {
+  harden(stateShape);
+  detachedHeapStores.isStorable(stateShape) ||
+    Fail`stateShape must be storable`;
+
+  const makeState = provideStateMaker(stateShape);
+
+  const wrappedInit = /** @type {I} */ (
+    (...args) => {
+      const initialData = init ? init(...args) : {};
+
+      typeof initialData === 'object' ||
+        Fail`initial data must be object, not ${initialData}`;
+      return makeState(initialData);
+    }
+  );
+  return wrappedInit;
+};
+
+/** @type {typeof rawDefineExoClass} */
+const defineExoClass = (
+  tag,
+  interfaceGuard,
+  rawInit,
+  methods,
+  { stateShape, ...otherOptions } = {},
+) =>
+  rawDefineExoClass(
+    tag,
+    interfaceGuard,
+    wrapExoInit(rawInit, stateShape),
+    methods,
+    otherOptions,
+  );
+
+/** @type {typeof rawDefineExoClassKit} */
+const defineExoClassKit = (
+  tag,
+  interfaceGuardKit,
+  rawInit,
+  methodsKit,
+  { stateShape, ...otherOptions } = {},
+) =>
+  rawDefineExoClassKit(
+    tag,
+    interfaceGuardKit,
+    wrapExoInit(rawInit, stateShape),
+    methodsKit,
+    otherOptions,
+  );
+
 /**
  * Create a heap (in-memory) zone that uses the default exo and store implementations.
  *