diff --git a/packages/ERTP/src/amountMath.js b/packages/ERTP/src/amountMath.js
index 9a900f0bf9d..d3e19063a3a 100644
--- a/packages/ERTP/src/amountMath.js
+++ b/packages/ERTP/src/amountMath.js
@@ -176,12 +176,13 @@ const checkLRAndGetHelpers = (leftAmount, rightAmount, brand = undefined) => {
 
 /**
  * @template {AssetKind} K
- * @param {MathHelpers<AssetKind>} h
+ * @param {MathHelpers<AssetValueForKind<K>>} h
  * @param {Amount<K>} leftAmount
  * @param {Amount<K>} rightAmount
  * @returns {[K, K]}
  */
 const coerceLR = (h, leftAmount, rightAmount) => {
+  // @ts-expect-error could be arbitrary subtype
   return [h.doCoerce(leftAmount.value), h.doCoerce(rightAmount.value)];
 };
 
@@ -243,9 +244,9 @@ const AmountMath = {
    * Return the amount representing an empty amount. This is the
    * identity element for MathHelpers.add and MatHelpers.subtract.
    *
-   * @template {AssetKind} K
+   * @template {AssetKind} [K='nat']
    * @param {Brand<K>} brand
-   * @param {K} [assetKind]
+   * @param {K} [assetKind='nat']
    * @returns {Amount<K>}
    */
   // @ts-expect-error TS/jsdoc things 'nat' can't be assigned to K subclassing AssetKind
@@ -254,6 +255,7 @@ const AmountMath = {
     assertRemotable(brand, 'brand');
     assertAssetKind(assetKind);
     const value = helpers[assetKind].doMakeEmpty();
+    // @ts-expect-error TS/jsdoc things 'nat' can't be assigned to K subclassing AssetKind
     return harden({ brand, value });
   },
   /**
diff --git a/packages/ERTP/src/types-module.d.ts b/packages/ERTP/src/types-module.d.ts
new file mode 100644
index 00000000000..97878d52ce7
--- /dev/null
+++ b/packages/ERTP/src/types-module.d.ts
@@ -0,0 +1,445 @@
+/**
+ * @file Generated from types.js, then find-replace to export all
+ *
+ * This file exists because types.js is ambient and some modules need the types
+ * to be explictly imported. Changing types.js to a module breaks too much.
+ */
+/* eslint-disable no-use-before-define */
+export type InterfaceSpec = import('@endo/marshal').InterfaceSpec;
+export type GetInterfaceOf = import('@endo/marshal').MarshalGetInterfaceOf;
+/**
+ * Amounts are descriptions of digital assets, answering the questions
+ * "how much" and "of what kind". Amounts are values labeled with a brand.
+ * AmountMath executes the logic of how amounts are changed when digital
+ * assets are merged, separated, or otherwise manipulated. For
+ * example, a deposit of 2 bucks into a purse that already has 3 bucks
+ * gives a new purse balance of 5 bucks. An empty purse has 0 bucks. AmountMath
+ * relies heavily on polymorphic MathHelpers, which manipulate the unbranded
+ * portion.
+ */
+export type Amount<K extends AssetKind = AssetKind> = {
+  brand: Brand<K>;
+  value: AssetValueForKind<K>;
+};
+/**
+ * An `AmountValue` describes a set or quantity of assets that can be owned or
+ * shared.
+ *
+ * A fungible `AmountValue` uses a non-negative bigint to represent a quantity
+ * of that many assets.
+ *
+ * A non-fungible `AmountValue` uses an array or CopySet of `Key`s to represent
+ * a set of whatever asset each key represents. A `Key` is a passable value
+ * that can be used as an element in a set (SetStore or CopySet) or as the
+ * key in a map (MapStore or CopyMap).
+ *
+ * `SetValue` is for the deprecated set representation, using an array directly
+ * to represent the array of its elements. `CopySetValue` is the proper
+ * representation using a CopySet.
+ *
+ * A semi-fungible `CopyBagValue` is represented as a
+ * `CopyBag` of `Key` objects. "Bag" is synonymous with MultiSet, where an
+ * element of a bag can be present once or more times, i.e., some positive
+ * bigint number of times, representing that quantity of the asset represented
+ * by that key.
+ */
+export type AmountValue = NatValue | any[] | CopySetValue | CopyBagValue;
+/**
+ * "Value" is a deprecated alias for "AmountValue". Please use
+ * "AmountValue" instead.
+ */
+export type Value = AmountValue;
+/**
+ * See doc-comment for `AmountValue`.
+ */
+export type AssetKind = 'nat' | 'set' | 'copySet' | 'copyBag';
+export type AssetValueForKind<K extends AssetKind> = K extends 'nat'
+  ? NatValue
+  : K extends 'set'
+  ? any[]
+  : K extends 'copySet'
+  ? CopySetValue
+  : K extends 'copyBag'
+  ? CopyBagValue
+  : never;
+export type AssetKindForValue<V extends AmountValue> = V extends NatValue
+  ? 'nat'
+  : V extends any[]
+  ? 'set'
+  : V extends CopySetValue
+  ? 'copySet'
+  : V extends CopyBagValue
+  ? 'copyBag'
+  : never;
+export type DisplayInfo<K extends AssetKind = AssetKind> = {
+  /**
+   * Tells the display software how
+   * many decimal places to move the decimal over to the left, or in
+   * other words, which position corresponds to whole numbers. We
+   * require fungible digital assets to be represented in integers, in
+   * the smallest unit (i.e. USD might be represented in mill, a
+   * thousandth of a dollar. In that case, `decimalPlaces` would be
+   * 3.) This property is optional, and for non-fungible digital
+   * assets, should not be specified. The decimalPlaces property
+   * should be used for *display purposes only*. Any other use is an
+   * anti-pattern.
+   */
+  decimalPlaces?: number | undefined;
+  /**
+   * - the kind of asset, either
+   * AssetKind.NAT (fungible) or
+   * AssetKind.SET or AssetKind.COPY_SET (non-fungible)
+   */
+  assetKind: K;
+};
+/**
+ * The brand identifies the kind of issuer, and has a function to get the
+ * alleged name for the kind of asset described. The alleged name (such
+ * as 'BTC' or 'moola') is provided by the maker of the issuer and should
+ * not be trusted as accurate.
+ *
+ * Every amount created by a particular AmountMath will share the same brand,
+ * but recipients cannot rely on the brand to verify that a purported amount
+ * represents the issuer they intended, since the same brand can be reused by
+ * a misbehaving issuer.
+ */
+export type Brand<K extends AssetKind = AssetKind> = {
+  /**
+   * Should be used with `issuer.getBrand` to ensure an issuer and brand match.
+   */
+  isMyIssuer: (allegedIssuer: ERef<Issuer>) => Promise<boolean>;
+  getAllegedName: () => string;
+  /**
+   * Give information to UI on how to display the amount.
+   */
+  getDisplayInfo: () => DisplayInfo;
+  getAmountShape: () => Pattern;
+};
+/**
+ * Return true if the payment continues to exist.
+ *
+ * If the payment is a promise, the operation will proceed upon
+ * resolution.
+ */
+export type IssuerIsLive = (payment: ERef<Payment>) => Promise<boolean>;
+/**
+ * Get the amount of digital assets in the payment. Because the
+ * payment is not trusted, we cannot call a method on it directly, and
+ * must use the issuer instead.
+ *
+ * If the payment is a promise, the operation will proceed upon
+ * resolution.
+ */
+export type IssuerGetAmountOf<K extends AssetKind = AssetKind> = (
+  payment: ERef<Payment>,
+) => Promise<Amount<K>>;
+/**
+ * Burn all of the digital assets in the
+ * payment. `optAmount` is optional. If `optAmount` is present, the
+ * code will insist that the amount of the digital assets in the
+ * payment is equal to `optAmount`, to prevent sending the wrong
+ * payment and other confusion.
+ *
+ * If the payment is a promise, the operation will proceed upon
+ * resolution.
+ */
+export type IssuerBurn = (
+  payment: ERef<Payment>,
+  optAmountShape?: Pattern | undefined,
+) => Promise<Amount>;
+/**
+ * Transfer all digital assets from the payment to a new payment and
+ * delete the original. `optAmount` is optional. If `optAmount` is
+ * present, the code will insist that the amount of digital assets in
+ * the payment is equal to `optAmount`, to prevent sending the wrong
+ * payment and other confusion.
+ *
+ * If the payment is a promise, the operation will proceed upon
+ * resolution.
+ */
+export type IssuerClaim = (
+  payment: ERef<Payment>,
+  optAmountShape?: Pattern | undefined,
+) => Promise<Payment>;
+/**
+ * Combine multiple payments into one payment.
+ *
+ * If any of the payments is a promise, the operation will proceed
+ * upon resolution.
+ */
+export type IssuerCombine = (
+  paymentsArray: ERef<Payment>[],
+  optTotalAmount?: Amount | undefined,
+) => Promise<Payment>;
+/**
+ * Split a single payment into two payments,
+ * A and B, according to the paymentAmountA passed in.
+ *
+ * If the payment is a promise, the operation will proceed upon
+ * resolution.
+ */
+export type IssuerSplit = (
+  payment: ERef<Payment>,
+  paymentAmountA: Amount,
+) => Promise<Payment[]>;
+/**
+ * Split a single payment into many payments, according to the amounts
+ * passed in.
+ *
+ * If the payment is a promise, the operation will proceed upon
+ * resolution.
+ */
+export type IssuerSplitMany = (
+  payment: ERef<Payment>,
+  amounts: Amount[],
+) => Promise<Payment[]>;
+/**
+ * The issuer cannot mint a new amount, but it can create empty purses
+ * and payments. The issuer can also transform payments (splitting
+ * payments, combining payments, burning payments, and claiming
+ * payments exclusively). The issuer should be gotten from a trusted
+ * source and then relied upon as the decider of whether an untrusted
+ * payment is valid.
+ */
+export type Issuer<K extends AssetKind = AssetKind> = {
+  /**
+   * Get the Brand for this Issuer. The
+   * Brand indicates the type of digital asset and is shared by the
+   * mint, the issuer, and any purses and payments of this particular
+   * kind. The brand is not closely held, so this function should not be
+   * trusted to identify an issuer alone. Fake digital assets and amount
+   * can use another issuer's brand.
+   */
+  getBrand: () => Brand<K>;
+  /**
+   * Get the allegedName for
+   * this mint/issuer
+   */
+  getAllegedName: () => string;
+  /**
+   * Get the kind of
+   * MathHelpers used by this Issuer.
+   */
+  getAssetKind: () => AssetKind;
+  /**
+   * Give information to UI
+   * on how to display amounts for this issuer.
+   */
+  getDisplayInfo: () => DisplayInfo;
+  /**
+   * Make an empty purse of this
+   * brand.
+   */
+  makeEmptyPurse: () => Purse<K>;
+  isLive: IssuerIsLive;
+  getAmountOf: IssuerGetAmountOf<K>;
+  burn: IssuerBurn;
+  claim: IssuerClaim;
+  combine: IssuerCombine;
+  split: IssuerSplit;
+  splitMany: IssuerSplitMany;
+};
+export type PaymentLedger<K extends AssetKind = AssetKind> = {
+  mint: Mint<K>;
+  issuer: Issuer<K>;
+  brand: Brand<K>;
+};
+export type IssuerKit<K extends AssetKind = AssetKind> = {
+  mint: Mint<K>;
+  issuer: Issuer<K>;
+  brand: Brand<K>;
+  displayInfo: DisplayInfo;
+};
+export type AdditionalDisplayInfo = {
+  /**
+   * Tells the display software how
+   * many decimal places to move the decimal over to the left, or in
+   * other words, which position corresponds to whole numbers. We
+   * require fungible digital assets to be represented in integers, in
+   * the smallest unit (i.e. USD might be represented in mill, a
+   * thousandth of a dollar. In that case, `decimalPlaces` would be
+   * 3.) This property is optional, and for non-fungible digital
+   * assets, should not be specified. The decimalPlaces property
+   * should be used for *display purposes only*. Any other use is an
+   * anti-pattern.
+   */
+  decimalPlaces?: number | undefined;
+  assetKind?: AssetKind | undefined;
+};
+/**
+ * Called to shut something down because something went wrong, where the reason
+ * is supposed to be an Error that describes what went wrong. Some valid
+ * implementations of `ShutdownWithFailure` will never return, either
+ * because they throw or because they immediately shutdown the enclosing unit
+ * of computation. However, they also might return, so the caller should
+ * follow this call by their own defensive `throw reason;` if appropriate.
+ */
+export type ShutdownWithFailure = (reason: Error) => void;
+/**
+ * Holding a Mint carries the right to issue new digital assets. These
+ * assets all have the same kind, which is called a Brand.
+ */
+export type Mint<K extends AssetKind = AssetKind> = {
+  /**
+   * Gets the Issuer for this mint.
+   */
+  getIssuer: () => Issuer<K>;
+  /**
+   * Creates a new Payment containing newly minted amount.
+   */
+  mintPayment: (newAmount: Amount<K>) => Payment<K>;
+};
+export type DepositFacetReceive = (
+  payment: Payment,
+  optAmountShape?: Pattern | undefined,
+) => Amount;
+export type DepositFacet = {
+  /**
+   * Deposit all the contents of payment into the purse that made this facet,
+   * returning the amount. If the optional argument `optAmount` does not equal the
+   * amount of digital assets in the payment, throw an error.
+   *
+   * If payment is a promise, throw an error.
+   */
+  receive: DepositFacetReceive;
+};
+export type PurseDeposit = (
+  payment: Payment,
+  optAmountShape?: Pattern | undefined,
+) => Amount;
+/**
+ * Purses hold amount of digital assets of the same brand, but unlike Payments,
+ * they are not meant to be sent to others. To transfer digital assets, a
+ * Payment should be withdrawn from a Purse. The amount of digital
+ * assets in a purse can change through the action of deposit() and withdraw().
+ *
+ * The primary use for Purses and Payments is for currency-like and goods-like
+ * digital assets, but they can also be used to represent other kinds of rights,
+ * such as the right to participate in a particular contract.
+ */
+export type Purse<K extends AssetKind = AssetKind> = {
+  /**
+   * Get the alleged Brand for this Purse
+   */
+  getAllegedBrand: () => Brand<K>;
+  /**
+   * Get the amount contained in this purse.
+   */
+  getCurrentAmount: () => Amount<K>;
+  /**
+   * Get a lossy notifier for changes to this purse's balance.
+   */
+  getCurrentAmountNotifier: () => Notifier<Amount<K>>;
+  /**
+   * Deposit all the contents of payment into this purse, returning the
+   * amount. If the optional argument `optAmount` does not equal the
+   * amount of digital assets in the payment, throw an error.
+   *
+   * If payment is a promise, throw an error.
+   */
+  deposit: PurseDeposit;
+  /**
+   * Return an object whose `receive` method deposits to the current Purse.
+   */
+  getDepositFacet: () => DepositFacet;
+  /**
+   * Withdraw amount from this purse into a new Payment.
+   */
+  withdraw: (amount: Amount<K>) => Payment;
+  /**
+   * The set of payments associated with this purse that are still live. These
+   * are the payments that can still be recovered in emergencies by, for example,
+   * depositing into this purse. Such a deposit action is like canceling an
+   * outstanding check because you're tired of waiting for it. Once your
+   * cancellation is acknowledged, you can spend the assets at stake on other
+   * things. Afterwards, if the recipient of the original check finally gets
+   * around to depositing it, their deposit fails.
+   */
+  getRecoverySet: () => CopySet<Payment<K>>;
+  /**
+   * For use in emergencies, such as coming back from a traumatic crash and
+   * upgrade. This deposits all the payments in this purse's recovery set
+   * into the purse itself, returning the total amount of assets recovered.
+   */
+  recoverAll: () => Amount<K>;
+};
+/**
+ * Payments hold amount of digital assets of the same brand in transit. Payments
+ * can be deposited in purses, split into multiple payments, combined, and
+ * claimed (getting an exclusive payment). Payments are linear, meaning
+ * that either a payment has the same amount of digital assets it
+ * started with, or it is used up entirely. It is impossible to partially use a
+ * payment.
+ *
+ * Payments are often received from other actors and therefore should
+ * not be trusted themselves. To get the amount of digital assets in a payment,
+ * use the trusted issuer: issuer.getAmountOf(payment),
+ *
+ * Payments can be converted to Purses by getting a trusted issuer and
+ * calling `issuer.makeEmptyPurse()` to create a purse, then
+ * `purse.deposit(payment)`.
+ */
+export type Payment<K extends AssetKind = AssetKind> = {
+  /**
+   * Get the allegedBrand, indicating the type of digital asset this
+   * payment purports to be, and which issuer to use. Because payments
+   * are not trusted, any method calls on payments should be treated
+   * with suspicion and verified elsewhere.
+   */
+  getAllegedBrand: () => Brand<K>;
+};
+/**
+ * All of the difference in how digital asset amount are manipulated can be
+ * reduced to the behavior of the math on values. We extract this
+ * custom logic into mathHelpers. MathHelpers are about value
+ * arithmetic, whereas AmountMath is about amounts, which are the
+ * values labeled with a brand. AmountMath use mathHelpers to do their value
+ * arithmetic, and then brand the results, making a new amount.
+ *
+ * The MathHelpers are designed to be called only from AmountMath, and so
+ * all methods but coerce can assume their inputs are valid. They only
+ * need to do output validation, and only when there is a possibility of
+ * invalid output.
+ */
+export type MathHelpers<V extends AmountValue> = {
+  /**
+   * Check the kind of this value and throw if it is not the
+   * expected kind.
+   */
+  doCoerce: (allegedValue: V) => V;
+  /**
+   * Get the representation for the identity element (often 0 or an
+   * empty array)
+   */
+  doMakeEmpty: () => V;
+  /**
+   * Is the value the identity element?
+   */
+  doIsEmpty: (value: V) => boolean;
+  /**
+   * Is the left greater than or equal to the right?
+   */
+  doIsGTE: (left: V, right: V) => boolean;
+  /**
+   * Does left equal right?
+   */
+  doIsEqual: (left: V, right: V) => boolean;
+  /**
+   * Return the left combined with the right.
+   */
+  doAdd: (left: V, right: V) => V;
+  /**
+   * Return what remains after removing the right from the left. If
+   * something in the right was not in the left, we throw an error.
+   */
+  doSubtract: (left: V, right: V) => V;
+};
+export type NatValue = bigint;
+export type NatMathHelpers = MathHelpers<NatValue>;
+export type SetValue = Array<Key>;
+export type SetMathHelpers = MathHelpers<any[]>;
+export type CopySetValue = CopySet<Key>;
+export type CopySetMathHelpers = MathHelpers<CopySetValue>;
+export type CopyBagValue = CopyBag<Key>;
+export type CopyBagMathHelpers = MathHelpers<CopyBagValue>;
+export type AssertAssetKind = (allegedAK: AssetKind) => void;
diff --git a/packages/ERTP/src/types.js b/packages/ERTP/src/types.js
index 57520d8039e..d4f3b92e2f0 100644
--- a/packages/ERTP/src/types.js
+++ b/packages/ERTP/src/types.js
@@ -1,8 +1,9 @@
+// @ts-check
 /// <reference types="ses"/>
 
 /**
  * @typedef {import('@endo/marshal').InterfaceSpec} InterfaceSpec
- * @typedef {import('@endo/marshal').GetInterfaceOf} GetInterfaceOf
+ * @typedef {import('@endo/marshal').MarshalGetInterfaceOf} GetInterfaceOf
  */
 
 /**
@@ -409,8 +410,8 @@
  */
 
 /**
- * @template {AssetKind} K
- * @typedef {object} MathHelpers<K>
+ * @template {AmountValue} V
+ * @typedef {object} MathHelpers
  * All of the difference in how digital asset amount are manipulated can be
  * reduced to the behavior of the math on values. We extract this
  * custom logic into mathHelpers. MathHelpers are about value
diff --git a/packages/SwingSet/src/devices/timer/device-timer.js b/packages/SwingSet/src/devices/timer/device-timer.js
index bc711ee4a72..baca8630390 100644
--- a/packages/SwingSet/src/devices/timer/device-timer.js
+++ b/packages/SwingSet/src/devices/timer/device-timer.js
@@ -1,3 +1,4 @@
+// @ts-check
 /**
  * A Timer device that provides a capability that can be used to schedule wake()
  * calls at particular times. The simpler form is a handler object with a wake()
@@ -147,7 +148,9 @@ function makeTimerMap(state = undefined) {
       } else {
         // Nothing prevents a particular handler from appearing more than once
         for (const { handler } of handlers) {
+          // @ts-expect-error FIXME Waker  'handler' can't be in array of IndexedHandler
           if (handler === targetHandler && handlers.indexOf(handler) !== -1) {
+            // @ts-expect-error FIXME Waker  'handler' can't be in array of IndexedHandler
             handlers.splice(handlers.indexOf(handler), 1);
             droppedTimes.push(time);
           }
diff --git a/packages/SwingSet/src/kernel/vat-loader/types.js b/packages/SwingSet/src/kernel/vat-loader/types.js
index db6e709af9f..5568006acbe 100644
--- a/packages/SwingSet/src/kernel/vat-loader/types.js
+++ b/packages/SwingSet/src/kernel/vat-loader/types.js
@@ -1,3 +1,4 @@
+// @ts-check
 /**
  * @typedef { [unknown, ...unknown[]] } Tagged
  * @typedef { { meterType: string, allocate: number|null, compute: number|null } }
diff --git a/packages/SwingSet/src/lib-nodejs/hasher.js b/packages/SwingSet/src/lib-nodejs/hasher.js
index 32b92a5d3ae..f84847934c7 100644
--- a/packages/SwingSet/src/lib-nodejs/hasher.js
+++ b/packages/SwingSet/src/lib-nodejs/hasher.js
@@ -1,3 +1,4 @@
+// @ts-check
 import { assert } from '@agoric/assert';
 
 import { createHash } from 'crypto';
diff --git a/packages/SwingSet/src/vats/network/multiaddr.js b/packages/SwingSet/src/vats/network/multiaddr.js
index 3e411ef273c..74c9108bef3 100644
--- a/packages/SwingSet/src/vats/network/multiaddr.js
+++ b/packages/SwingSet/src/vats/network/multiaddr.js
@@ -1,3 +1,4 @@
+// @ts-check
 /**
  * @typedef {[string, string][]} Multiaddr
  * @typedef {string} Textaddr An address string formatted as in https://github.com/multiformats/multiaddr
@@ -38,6 +39,7 @@ export function parse(ma) {
     if (m[2]) {
       acc.push([m[1], m[3]]);
     } else {
+      // @ts-expect-error '[string]' is not assignable to parameter of type '[string, string]'
       acc.push([m[1]]);
     }
   }
diff --git a/packages/SwingSet/tools/internal-types.js b/packages/SwingSet/tools/internal-types.js
index 7926471379c..a2eb20039a2 100644
--- a/packages/SwingSet/tools/internal-types.js
+++ b/packages/SwingSet/tools/internal-types.js
@@ -1,3 +1,4 @@
+// @ts-check
 /**
  * @typedef {object} ManualTimerAdmin
  * @property { (when: Timestamp) => void } advanceTo
diff --git a/packages/SwingSet/tools/manual-timer.js b/packages/SwingSet/tools/manual-timer.js
index 3cb39ec1184..b491ae11e74 100644
--- a/packages/SwingSet/tools/manual-timer.js
+++ b/packages/SwingSet/tools/manual-timer.js
@@ -53,7 +53,7 @@ const setup = () => {
  * kernel. You can make time pass by calling `advanceTo(when)`.
  *
  * @param {ManualTimerOptions} [options]
- * @returns {ManualTimer}
+ * @returns {TimerService & { advanceTo: (when: Timestamp) => void; }}
  */
 export const buildManualTimer = (options = {}) => {
   const { startTime = 0n, ...other } = options;
diff --git a/packages/agoric-cli/package.json b/packages/agoric-cli/package.json
index fd513e99384..96f903cd366 100644
--- a/packages/agoric-cli/package.json
+++ b/packages/agoric-cli/package.json
@@ -20,7 +20,7 @@
     "integration-test": "ava --config .ava-integration-test.config.js",
     "lint-fix": "yarn lint:eslint --fix",
     "lint": "run-s --continue-on-error lint:*",
-    "lint:types": "tsc --maxNodeModuleJsDepth 4 -p jsconfig.json",
+    "lint:types": "tsc --maxNodeModuleJsDepth 0 -p jsconfig.json",
     "lint:eslint": "eslint ."
   },
   "devDependencies": {
diff --git a/packages/agoric-cli/src/commands/psm.js b/packages/agoric-cli/src/commands/psm.js
index ed9f637eab3..6dcdd7ef803 100644
--- a/packages/agoric-cli/src/commands/psm.js
+++ b/packages/agoric-cli/src/commands/psm.js
@@ -162,8 +162,12 @@ export const makePsmCommand = async logger => {
       const opts = this.opts();
       console.warn('running with options', opts);
       const instance = await lookupPsmInstance(opts.pair);
-      // @ts-expect-error RpcRemote types not real instances
-      const spendAction = makePSMSpendAction(instance, agoricNames.brand, opts);
+      const spendAction = makePSMSpendAction(
+        instance,
+        // @ts-expect-error xxx RpcRemote
+        agoricNames.brand,
+        opts,
+      );
       outputAction(spendAction);
     });
 
@@ -182,7 +186,6 @@ export const makePsmCommand = async logger => {
         id: Number(opts.offerId),
         invitationSpec: {
           source: 'purse',
-          // @ts-expect-error rpc
           instance: economicCommittee,
           description: 'Voter0', // XXX it may not always be
         },
@@ -212,7 +215,6 @@ export const makePsmCommand = async logger => {
         id: Number(opts.offerId),
         invitationSpec: {
           source: 'purse',
-          // @ts-expect-error rpc
           instance: psmCharter,
           description: 'PSM charter member invitation',
         },
@@ -316,8 +318,8 @@ export const makePsmCommand = async logger => {
 
       const psmInstance = lookupPsmInstance(opts.pair);
 
-      /** @type {Brand} */
-      // @ts-expect-error yes, it is a brand
+      /** @type {import('../types.js').Brand} */
+      // @ts-expect-error xxx RpcRemote
       const istBrand = agoricNames.brand.IST;
       const scaledAmount = harden({
         brand: istBrand,
diff --git a/packages/agoric-cli/src/lib/format.js b/packages/agoric-cli/src/lib/format.js
index 4265203fce6..1c7e1964632 100644
--- a/packages/agoric-cli/src/lib/format.js
+++ b/packages/agoric-cli/src/lib/format.js
@@ -59,7 +59,7 @@ export const asPercent = ratio => {
 };
 
 /**
- * @param {Amount[]} balances
+ * @param {Array<import('../types').Amount>} balances
  * @param {AssetDescriptor[]} assets
  */
 export const simplePurseBalances = (balances, assets) => {
diff --git a/packages/agoric-cli/src/lib/psm.js b/packages/agoric-cli/src/lib/psm.js
index 7a90febd736..2516a85e1e9 100644
--- a/packages/agoric-cli/src/lib/psm.js
+++ b/packages/agoric-cli/src/lib/psm.js
@@ -4,9 +4,6 @@ import { COSMOS_UNIT, makeAmountFormatter } from './format.js';
 // eslint-disable-next-line no-unused-vars -- typeof below
 import { makeAgoricNames } from './rpc.js';
 
-// Ambient types. Needed only for dev but this does a runtime import.
-import '@agoric/zoe/src/zoeService/types.js';
-
 /** @typedef {import('@agoric/smart-wallet/src/offers').OfferSpec} OfferSpec */
 /** @typedef {import('@agoric/smart-wallet/src/offers').OfferStatus} OfferStatus */
 /** @typedef {import('@agoric/smart-wallet/src/smartWallet').BridgeAction} BridgeAction */
@@ -32,7 +29,6 @@ export const simpleOffers = (state, agoricNames) => {
       payouts,
     } = o;
     const entry = Object.entries(agoricNames.instance).find(
-      // @ts-expect-error xxx RpcRemote
       ([_name, candidate]) => candidate === instance,
     );
     const instanceName = entry ? entry[0] : '???';
@@ -52,11 +48,11 @@ export const simpleOffers = (state, agoricNames) => {
 };
 
 /**
- * @param {Record<string, Brand>} brands
+ * @param {Record<string, import('../types').Brand>} brands
  * @param {({ wantMinted: number | undefined, giveMinted: number | undefined })} opts
  * @param {number} [fee=0]
  * @param {string} [anchor]
- * @returns {Proposal}
+ * @returns {import('../types').Proposal}
  */
 export const makePSMProposal = (brands, opts, fee = 0, anchor = 'AUSD') => {
   const giving = opts.giveMinted ? 'minted' : 'anchor';
@@ -82,8 +78,8 @@ export const makePSMProposal = (brands, opts, fee = 0, anchor = 'AUSD') => {
 };
 
 /**
- * @param {Instance} instance
- * @param {Record<string, Brand>} brands
+ * @param {import('../types').Instance} instance
+ * @param {Record<string, import('../types').Brand>} brands
  * @param {{ offerId: number, feePct?: number } &
  *         ({ wantMinted: number | undefined, giveMinted: number | undefined })} opts
  * @returns {BridgeAction}
diff --git a/packages/agoric-cli/src/lib/rpc.js b/packages/agoric-cli/src/lib/rpc.js
index a095713a260..f53bce33fd1 100644
--- a/packages/agoric-cli/src/lib/rpc.js
+++ b/packages/agoric-cli/src/lib/rpc.js
@@ -117,7 +117,7 @@ export const makeVStorage = powers => {
  * - if a part being serialized has a boardId property, it passes through as a slot value whereas the normal marshaller would treat it as a copyRecord
  *
  * @param {(slot: string, iface: string) => any} slotToVal
- * @returns {Marshaller}
+ * @returns {import('@endo/marshal').Marshal<string>}
  */
 export const boardSlottingMarshaller = (slotToVal = (s, _i) => s) => ({
   /** @param {{body: string, slots: string[]}} capData */
diff --git a/packages/agoric-cli/src/lib/wallet.js b/packages/agoric-cli/src/lib/wallet.js
index 9f93af96937..ed39800aad9 100644
--- a/packages/agoric-cli/src/lib/wallet.js
+++ b/packages/agoric-cli/src/lib/wallet.js
@@ -1,4 +1,5 @@
 // @ts-check
+/* eslint-disable @typescript-eslint/prefer-ts-expect-error -- https://github.com/Agoric/agoric-sdk/issues/4620 */
 import { boardSlottingMarshaller, storageHelper } from './rpc.js';
 
 /**
@@ -16,7 +17,7 @@ export const getWalletState = async (addr, ctx, { vstorage }) => {
 
   /** @type {Map<number, import('./psm').OfferSpec>} */
   const offers = new Map();
-  /** @type {Map<Brand, Amount>} */
+  /** @type {Map<import('../types').Brand, import('../types').Amount>} */
   const balances = new Map();
   /** @type {import('./format').AssetDescriptor[]} */
   const brands = [];
@@ -37,17 +38,18 @@ export const getWalletState = async (addr, ctx, { vstorage }) => {
       case 'balance': {
         const { currentAmount } = update;
         if (!balances.has(currentAmount.brand)) {
+          // @ts-ignore https://github.com/agoric/agoric-sdk/issues/4560
           balances.set(currentAmount.brand, currentAmount);
         }
         break;
       }
       case 'brand': {
-        // @ts-expect-error cast for unserialization hack
+        // @ts-ignore https://github.com/agoric/agoric-sdk/issues/4560
         brands.push(update.descriptor);
         break;
       }
       default:
-        // @ts-expect-error
+        // @ts-ignore https://github.com/agoric/agoric-sdk/issues/4560
         throw Error(`unsupported update ${update.updated}`);
     }
   });
diff --git a/packages/agoric-cli/src/types.d.ts b/packages/agoric-cli/src/types.d.ts
new file mode 100644
index 00000000000..cd3fbb5dfcf
--- /dev/null
+++ b/packages/agoric-cli/src/types.d.ts
@@ -0,0 +1,6 @@
+// This package has maxNodeModuleJsDepth=0 to prevent ambient imports.
+// A consequence is that types that are only provided ambiently have to be defined.
+
+export { Amount, Brand, Proposal } from '@agoric/ertp/src/types-module';
+
+export type Instance = unknown;
diff --git a/packages/deploy-script-support/src/externalTypes.js b/packages/deploy-script-support/src/externalTypes.js
index 19502b21c62..b575d15364a 100644
--- a/packages/deploy-script-support/src/externalTypes.js
+++ b/packages/deploy-script-support/src/externalTypes.js
@@ -1,3 +1,4 @@
+// @ts-check
 /**
  * @callback InstallSaveAndPublish
  * @param {string} resolvedPath
diff --git a/packages/governance/src/constants.js b/packages/governance/src/constants.js
index 7fa2b609003..854bfed07a1 100644
--- a/packages/governance/src/constants.js
+++ b/packages/governance/src/constants.js
@@ -1,3 +1,4 @@
+// @ts-check
 /**
  * Enum of parameter types
  *
diff --git a/packages/governance/src/types.js b/packages/governance/src/types.js
index cef771f4f41..54da4dac4de 100644
--- a/packages/governance/src/types.js
+++ b/packages/governance/src/types.js
@@ -279,7 +279,7 @@
 
 /**
  * @typedef { ElectorateCreatorFacet & {
- *   getVoterInvitations: () => Promise<Invitation>[]
+ *   getVoterInvitations: () => Promise<Invitation<{voter: import('../test/swingsetTests/contractGovernor/vat-voter.js').EVatVoter}>>[]
  * }} CommitteeElectorateCreatorFacet
  */
 
diff --git a/packages/inter-protocol/scripts/manual-price-feed.js b/packages/inter-protocol/scripts/manual-price-feed.js
index 877e38c9f22..1d07176b2a3 100644
--- a/packages/inter-protocol/scripts/manual-price-feed.js
+++ b/packages/inter-protocol/scripts/manual-price-feed.js
@@ -1,3 +1,4 @@
+// @ts-check
 import { E } from '@endo/far';
 import { deeplyFulfilled } from '@endo/marshal';
 import { makeNotifierFromAsyncIterable } from '@agoric/notifier';
diff --git a/packages/inter-protocol/src/psm/psm.js b/packages/inter-protocol/src/psm/psm.js
index dbd67a0a435..b82942f018b 100644
--- a/packages/inter-protocol/src/psm/psm.js
+++ b/packages/inter-protocol/src/psm/psm.js
@@ -328,3 +328,5 @@ export const start = async (zcf, privateArgs, baggage) => {
     publicFacet,
   });
 };
+
+/** @typedef {Awaited<ReturnType<typeof start>>['publicFacet']} PsmPublicFacet */
diff --git a/packages/inter-protocol/src/reserve/assetReserve.js b/packages/inter-protocol/src/reserve/assetReserve.js
index bcad490da99..eaa2bad3894 100644
--- a/packages/inter-protocol/src/reserve/assetReserve.js
+++ b/packages/inter-protocol/src/reserve/assetReserve.js
@@ -407,6 +407,7 @@ const start = async (zcf, privateArgs, baggage) => {
     reduceLiquidationShortfall,
   };
 
+  /** @param {MethodContext} context */
   const makeShortfallReportingInvitation = ({ facets }) => {
     const handleShortfallReportingOffer = () => {
       return facets.shortfallReportingFacet;
@@ -464,7 +465,7 @@ export { start };
  * @property {() => Invitation} makeAddCollateralInvitation
  * @property {() => Allocation} getAllocations
  * @property {(issuer: Issuer) => void} addIssuer
- * @property {() => Invitation} makeShortfallReportingInvitation
+ * @property {() => Invitation<ShortfallReporter>} makeShortfallReportingInvitation
  * @property {() => MetricsNotification} getMetrics
  */
 
diff --git a/packages/inter-protocol/src/stakeFactory/types.js b/packages/inter-protocol/src/stakeFactory/types.js
index fd637f4e80d..c435de171fa 100644
--- a/packages/inter-protocol/src/stakeFactory/types.js
+++ b/packages/inter-protocol/src/stakeFactory/types.js
@@ -1,3 +1,4 @@
+// @ts-check
 /**
  * For example, an agoric1... Cosmos address
  *
diff --git a/packages/inter-protocol/src/vaultFactory/types.js b/packages/inter-protocol/src/vaultFactory/types.js
index 63eba52ffdf..8354bec93b9 100644
--- a/packages/inter-protocol/src/vaultFactory/types.js
+++ b/packages/inter-protocol/src/vaultFactory/types.js
@@ -117,7 +117,7 @@
 
 /**
  * @typedef {object} Liquidator
- * @property {() => Promise<Invitation<{ debt: Amount<'nat'> }, void>>} makeLiquidateInvitation
+ * @property {() => Promise<Invitation<void, { debt: Amount<'nat'>; penaltyRate: Ratio; }>>} makeLiquidateInvitation
  */
 
 /**
diff --git a/packages/inter-protocol/src/vpool-xyk-amm/addPool.js b/packages/inter-protocol/src/vpool-xyk-amm/addPool.js
index e67492cfb18..e08c7fc9e4d 100644
--- a/packages/inter-protocol/src/vpool-xyk-amm/addPool.js
+++ b/packages/inter-protocol/src/vpool-xyk-amm/addPool.js
@@ -157,6 +157,7 @@ export const makeAddPoolInvitation = (
       );
     const minLiqAmount = AmountMath.make(
       liquidityBrand,
+      // @ts-expect-error known nat
       minPoolLiquidity.value,
     );
 
diff --git a/packages/inter-protocol/src/vpool-xyk-amm/multipoolMarketMaker.js b/packages/inter-protocol/src/vpool-xyk-amm/multipoolMarketMaker.js
index 1e6b7ca6183..9d436d92b94 100644
--- a/packages/inter-protocol/src/vpool-xyk-amm/multipoolMarketMaker.js
+++ b/packages/inter-protocol/src/vpool-xyk-amm/multipoolMarketMaker.js
@@ -55,7 +55,7 @@ const trace = makeTracer('XykAmm', false);
  * @typedef {Readonly<{
  * zcf: ZCF<AmmTerms>,
  * secondaryBrandToPool: WeakMapStore<Brand,PoolFacets>,
- * secondaryBrandToLiquidityMint: WeakMapStore<Brand,ZCFMint>,
+ * secondaryBrandToLiquidityMint: WeakMapStore<Brand,ZCFMint<'nat'>>,
  * centralBrand: Brand,
  * timer: TimerService,
  * quoteIssuerKit: IssuerKit,
diff --git a/packages/inter-protocol/src/vpool-xyk-amm/params.js b/packages/inter-protocol/src/vpool-xyk-amm/params.js
index dd21be5578a..71682e4b3bc 100644
--- a/packages/inter-protocol/src/vpool-xyk-amm/params.js
+++ b/packages/inter-protocol/src/vpool-xyk-amm/params.js
@@ -13,7 +13,7 @@ const DEFAULT_PROTOCOL_FEE_BP = 6n;
  * @param {Invitation} electorateInvitation - invitation for the question poser
  * @param {bigint} protocolFeeBP
  * @param {bigint} poolFeeBP
- * @param {Amount} minInitialLiquidity
+ * @param {Amount<'nat'>} minInitialLiquidity
  */
 const makeAmmParams = (
   electorateInvitation,
diff --git a/packages/inter-protocol/src/vpool-xyk-amm/pool.js b/packages/inter-protocol/src/vpool-xyk-amm/pool.js
index eb5b81940ff..4e1ec873adf 100644
--- a/packages/inter-protocol/src/vpool-xyk-amm/pool.js
+++ b/packages/inter-protocol/src/vpool-xyk-amm/pool.js
@@ -84,7 +84,7 @@ export const definePoolKind = (baggage, ammPowers, storageNode, marshaller) => {
   );
 
   /**
-   * @param {ZCFMint} liquidityZcfMint
+   * @param {ZCFMint<'nat'>} liquidityZcfMint
    * @param {ZCFSeat} poolSeat
    * @param {Brand} secondaryBrand
    * @returns {ImmutableState & MutableState}
diff --git a/packages/inter-protocol/test/psm/setupPsm.js b/packages/inter-protocol/test/psm/setupPsm.js
index 1dba9fd8e17..6d5ef1e2e43 100644
--- a/packages/inter-protocol/test/psm/setupPsm.js
+++ b/packages/inter-protocol/test/psm/setupPsm.js
@@ -170,7 +170,7 @@ export const setupPsm = async (
   };
   const governedInstance = E(governorPublicFacet).getGovernedContract();
 
-  /** @type { GovernedPublicFacet<PSM> } */
+  /** @type { GovernedPublicFacet<import('../../src/psm/psm.js').PsmPublicFacet> } */
   const psmPublicFacet = await E(governorCreatorFacet).getPublicFacet();
   const psm = {
     psmCreatorFacet: psmFacets.psmCreatorFacet,
diff --git a/packages/inter-protocol/test/reserve/setup.js b/packages/inter-protocol/test/reserve/setup.js
index e0a54a66681..24080e5d200 100644
--- a/packages/inter-protocol/test/reserve/setup.js
+++ b/packages/inter-protocol/test/reserve/setup.js
@@ -1,3 +1,4 @@
+// @ts-check
 import buildManualTimer from '@agoric/zoe/tools/manualTimer.js';
 import { E } from '@endo/eventual-send';
 import {
@@ -9,11 +10,15 @@ import { provideBundle } from '../supports.js';
 const reserveRoot = './src/reserve/assetReserve.js'; // package relative
 const faucetRoot = './test/vaultFactory/faucet.js';
 
+/**
+ * @typedef {ReturnType<typeof setUpZoeForTest>} FarZoeKit
+ */
+
 /**
  * NOTE: called separately by each test so AMM/zoe/priceAuthority don't interfere
  *
  * @param {*} t
- * @param {ManualTimer | undefined=} timer
+ * @param {ManualTimer | undefined} timer
  * @param {FarZoeKit} farZoeKit
  * @param {Issuer} runIssuer
  * @param {{ committeeName: string, committeeSize: number}} electorateTerms
@@ -35,9 +40,13 @@ const setupReserveBootstrap = async (
     timer,
     farZoeKit,
   );
-  const { produce } = /** @type { EconomyBootstrapPowers } */ (ammSpaces.space);
+  const { produce } =
+    /** @type { import('../../src/proposals/econ-behaviors.js').EconomyBootstrapPowers } */ (
+      ammSpaces.space
+    );
   const zoe = await farZoeKit.zoe;
 
+  // @ts-expect-error xxx
   produce.chainTimerService.resolve(timer);
   produce.zoe.resolve(zoe);
 
diff --git a/packages/inter-protocol/test/vaultFactory/test-vaultFactory.js b/packages/inter-protocol/test/vaultFactory/test-vaultFactory.js
index ef635924fc7..020dc240158 100644
--- a/packages/inter-protocol/test/vaultFactory/test-vaultFactory.js
+++ b/packages/inter-protocol/test/vaultFactory/test-vaultFactory.js
@@ -1498,10 +1498,10 @@ test('transfer vault', async t => {
     return amount.value[0];
   };
 
+  /** @type {Promise<Invitation<VaultKit>>} */
   const transferInvite = E(aliceVault).makeTransferInvitation();
   const inviteProps = await getInvitationProperties(transferInvite);
   trace(t, 'TRANSFER INVITE', transferInvite, inviteProps);
-  /** @type {UserSeat<VaultKit>} */
   const transferSeat = await E(zoe).offer(transferInvite);
   const {
     vault: transferVault,
@@ -1561,8 +1561,8 @@ test('transfer vault', async t => {
     }),
     harden({ Minted: paybackPayment }),
   );
+  /** @type {Invitation<VaultKit>} */
   const t2Invite = await E(transferVault).makeTransferInvitation();
-  /** @type {UserSeat<VaultKit>} */
   const t2Seat = await E(zoe).offer(t2Invite);
   const {
     vault: t2Vault,
@@ -2269,7 +2269,6 @@ test('excessive debt on collateral type', async t => {
   const { lender } = services.vaultFactory;
   const collateralAmount = aeth.make(1_000_000n);
   const centralAmount = run.make(1_000_000n);
-  /** @type {UserSeat<VaultKit>} */
   const loanSeat = await E(zoe).offer(
     E(lender).makeVaultInvitation(),
     harden({
@@ -2859,7 +2858,7 @@ test('manager notifiers', async t => {
   // can't use 0n because of https://github.com/Agoric/agoric-sdk/issues/5548
   // but since this test is of metrics, we take the opportunity to check totalCollateral changing
   const given = aeth.make(2n);
-  vaultSeat = await E(services.zoe).offer(
+  let vaultOpSeat = await E(services.zoe).offer(
     await E(vault).makeAdjustBalancesInvitation(),
     harden({
       // nominal collateral
@@ -2870,14 +2869,14 @@ test('manager notifiers', async t => {
       Collateral: t.context.aeth.mint.mintPayment(given),
     }),
   );
-  await E(vaultSeat).getOfferResult();
+  await E(vaultOpSeat).getOfferResult();
   await m.assertChange({
     totalDebt: { value: DEBT1_EXTRA },
     totalCollateral: { value: AMPLE + given.value },
   });
 
   trace('13. Close loan');
-  vaultSeat = await E(services.zoe).offer(
+  vaultOpSeat = await E(services.zoe).offer(
     await E(vault).makeCloseInvitation(),
     harden({
       give: { Minted: run.make(DEBT1_EXTRA) },
@@ -2887,7 +2886,7 @@ test('manager notifiers', async t => {
       Minted: await getRunFromFaucet(t, DEBT1_EXTRA),
     }),
   );
-  await E(vaultSeat).getOfferResult();
+  await E(vaultOpSeat).getOfferResult();
   await m.assertChange({
     numActiveVaults: 0,
     totalCollateral: { value: 0n },
diff --git a/packages/smart-wallet/src/offers.js b/packages/smart-wallet/src/offers.js
index 60e6fe589fe..6955a467adf 100644
--- a/packages/smart-wallet/src/offers.js
+++ b/packages/smart-wallet/src/offers.js
@@ -127,7 +127,9 @@ export const makeOfferExecutor = ({
                 updateStatus({ result });
                 break;
               case 'copyRecord':
+                // @ts-expect-error result narrowed by passStyle
                 if ('invitationMakers' in result) {
+                  // @ts-expect-error result narrowed by passStyle
                   // save for continuing invitation offer
                   onNewContinuingOffer(id, result.invitationMakers);
                 }
diff --git a/packages/solo/src/chain-cosmos-sdk.js b/packages/solo/src/chain-cosmos-sdk.js
index 75ebe383033..c506d342c01 100644
--- a/packages/solo/src/chain-cosmos-sdk.js
+++ b/packages/solo/src/chain-cosmos-sdk.js
@@ -1,3 +1,4 @@
+// @ts-check
 /* global setTimeout Buffer */
 import path from 'path';
 import fs from 'fs';
@@ -80,7 +81,7 @@ const makeTempFile = async (prefix, contents) => {
         if (err) {
           return reject(err);
         }
-        return resolve();
+        return resolve(undefined);
       });
     });
   } finally {
@@ -89,7 +90,7 @@ const makeTempFile = async (prefix, contents) => {
         if (e) {
           return reject(e);
         }
-        return resolve();
+        return resolve(undefined);
       });
     });
   }
@@ -214,6 +215,7 @@ export async function connectToChain(
         },
       );
       if (stdin) {
+        assert(proc.stdin, 'no stdin');
         proc.stdin.write(stdin);
         proc.stdin.end();
       }
@@ -583,6 +585,7 @@ ${chainID} chain does not yet know of address ${clientAddr}${adviseEgress(
     const bigPool = messagePool.concat(newMessages);
 
     // Sort the big pool by sequence number.
+    // @ts-expect-error FIXME bigint as sort value
     const sortedPool = bigPool.sort((a, b) => a[0] - b[0]);
 
     // Only keep messages that have a unique sequence number.
@@ -727,7 +730,7 @@ ${chainID} chain does not yet know of address ${clientAddr}${adviseEgress(
    *
    * It then delivers the mailbox to inbound.  There are no optimisations.
    *
-   * @param {number=} lastMailboxUpdate
+   * @param {UpdateCount=} lastMailboxUpdate
    */
   const recurseEachMailboxUpdate = async (lastMailboxUpdate = undefined) => {
     const { updateCount, value: mailbox } = await mbNotifier.getUpdateSince(
@@ -758,6 +761,7 @@ ${chainID} chain does not yet know of address ${clientAddr}${adviseEgress(
     // Reset the backoff period.
     retryBackoff = randomizeDelay(INITIAL_SEND_RETRY_DELAY_MS);
   };
+  /** @param {Error} [e]  */
   const failedSend = (e = undefined) => {
     if (e) {
       console.error(`Error sending`, e);
@@ -778,6 +782,7 @@ ${chainID} chain does not yet know of address ${clientAddr}${adviseEgress(
   };
 
   // This function ensures we only have one outgoing send operation at a time.
+  /** @type {(lastSendUpdate?: UpdateCount) => Promise<void>} */
   const recurseEachSend = async (lastSendUpdate = undefined) => {
     // See when there is another requested send since our last time.
     const { updateCount } = await sendNotifier.getUpdateSince(lastSendUpdate);
diff --git a/packages/solo/src/outbound.js b/packages/solo/src/outbound.js
index 0a6b3ec65ec..21d6f736509 100644
--- a/packages/solo/src/outbound.js
+++ b/packages/solo/src/outbound.js
@@ -1,3 +1,4 @@
+// @ts-check
 /* global process */
 import anylogger from 'anylogger';
 
@@ -14,7 +15,7 @@ const log = anylogger('outbound');
  * @property {(newMessages: Array<[number, string]>, acknum: number) => void} deliverator
  * @property {number} highestSent
  * @property {number} highestAck
- * @property {number} trips
+ * @property {number} [trips]
  */
 
 /**
@@ -32,6 +33,7 @@ export function deliver(mbs) {
       continue;
     }
     const t = knownTargets.get(target);
+    assert(t, `missing target ${target}`);
     const newMessages = [];
     data[target].outbox.forEach(m => {
       const [msgnum, body] = m;
diff --git a/packages/solo/src/scratch.js b/packages/solo/src/scratch.js
index 74d57e1cdab..f598e1f56c2 100644
--- a/packages/solo/src/scratch.js
+++ b/packages/solo/src/scratch.js
@@ -1,3 +1,4 @@
+// @ts-check
 import { E } from '@endo/eventual-send';
 import { Far } from '@endo/marshal';
 
diff --git a/packages/ui-components/package.json b/packages/ui-components/package.json
index 08a9811d6e6..1e0859b56e6 100644
--- a/packages/ui-components/package.json
+++ b/packages/ui-components/package.json
@@ -28,7 +28,7 @@
     "lint-fix": "yarn lint:eslint --fix",
     "lint": "run-s --continue-on-error lint:*",
     "lint:eslint": "eslint .",
-    "lint:types": "tsc --maxNodeModuleJsDepth 4 -p jsconfig.json"
+    "lint:types": "tsc --maxNodeModuleJsDepth 0 -p jsconfig.json"
   },
   "eslintConfig": {
     "extends": [
diff --git a/packages/ui-components/src/components/NatPurseSelector.jsx b/packages/ui-components/src/components/NatPurseSelector.jsx
index 9529eb0e3a2..5ddb7e1b3af 100644
--- a/packages/ui-components/src/components/NatPurseSelector.jsx
+++ b/packages/ui-components/src/components/NatPurseSelector.jsx
@@ -9,9 +9,9 @@ import { stringifyValue } from '../display/index.js';
  * components represent initial state as null/undefined.
  *
  * @param {Array<PursesJSONState> | null} purses Unfiltered purses. This may be null to simplify use in UIs.
- * @param {Brand} [optBrand] - optional brand to filter for
+ * @param {import('@agoric/ertp/src/types-module').Brand} [optBrand] - optional brand to filter for
  * @returns {PursesJSONState[] | null}
- * @typedef {{ brand: Brand, displayInfo: any }} PursesJSONState
+ * @typedef {{ brand: import('@agoric/ertp/src/types-module').Brand, displayInfo: any }} PursesJSONState
  * see wallet/api/src/types.js
  * @deprecated
  */
@@ -26,7 +26,7 @@ export const filterPurses = (purses, optBrand) => {
 };
 
 /**
- * @typedef {{ pursePetname: string, brandPetname: string, value: AmountValue, displayInfo: DisplayInfo }} Purse
+ * @typedef {{ pursePetname: string, brandPetname: string, value: import('@agoric/ertp/src/types-module').AmountValue, displayInfo: import('@agoric/ertp/src/types-module').DisplayInfo }} Purse
  */
 
 const isNatPurse = ({ displayInfo: { assetKind } }) =>
diff --git a/packages/ui-components/src/display/display.js b/packages/ui-components/src/display/display.js
index 5e6d7b908d4..061feeca12d 100644
--- a/packages/ui-components/src/display/display.js
+++ b/packages/ui-components/src/display/display.js
@@ -1,21 +1,20 @@
 // @ts-check
-import { assert, details } from '@agoric/assert';
 import { AssetKind } from '@agoric/ertp';
-import '@agoric/ertp/exported.js';
-
+import { parseAsCopyBag } from './copyBagValue/parseAsCopyBag.js';
+import { stringifyCopyBag } from './copyBagValue/stringifyCopyBag.js';
 import { parseAsNat } from './natValue/parseAsNat.js';
 import { stringifyNat } from './natValue/stringifyNat.js';
 import { parseAsSet } from './setValue/parseAsSet.js';
 import { stringifySet } from './setValue/stringifySet.js';
-import { parseAsCopyBag } from './copyBagValue/parseAsCopyBag.js';
-import { stringifyCopyBag } from './copyBagValue/stringifyCopyBag.js';
+
+const { details } = assert;
 
 /**
  *
  * @param {string} str - string to parse as a value
- * @param {AssetKind} [assetKind] - assetKind of the value
+ * @param {import('@agoric/ertp/src/types.js').AssetKind} [assetKind] - assetKind of the value
  * @param {number} [decimalPlaces] - places to move the decimal to the left
- * @returns {AmountValue}
+ * @returns {import('@agoric/ertp/src/types.js').AmountValue}
  */
 export const parseAsValue = (
   str,
@@ -36,10 +35,10 @@ export const parseAsValue = (
 
 /**
  * @param {string} str - string to parse as a value
- * @param {Brand} brand - brand to use in the amount
- * @param {AssetKind} [assetKind] - assetKind of the value
+ * @param {import('@agoric/ertp/src/types.js').Brand} brand - brand to use in the amount
+ * @param {import('@agoric/ertp/src/types.js').AssetKind} [assetKind] - assetKind of the value
  * @param {number} [decimalPlaces] - places to move the decimal to the left
- * @returns {Amount}
+ * @returns {import('@agoric/ertp/src/types.js').Amount}
  */
 export const parseAsAmount = (
   str,
@@ -52,8 +51,8 @@ export const parseAsAmount = (
 
 /**
  *
- * @param {AmountValue} value - value to stringify
- * @param {AssetKind} [assetKind] - assetKind of the value
+ * @param {import('@agoric/ertp/src/types.js').AmountValue} value - value to stringify
+ * @param {import('@agoric/ertp/src/types.js').AssetKind} [assetKind] - assetKind of the value
  * @param {number} [decimalPlaces] - places to move the decimal to the
  * right in the string
  * @param {number} [placesToShow] - places after the decimal to show
@@ -66,7 +65,6 @@ export const stringifyValue = (
   placesToShow = 2,
 ) => {
   if (assetKind === AssetKind.NAT) {
-    // @ts-expect-error AmountValue is a Nat
     return stringifyNat(value, decimalPlaces, placesToShow);
   }
   if (assetKind === AssetKind.SET) {
@@ -98,8 +96,8 @@ export const stringifyPurseValue = purse => {
 /**
  * Stringify the value in an amount
  *
- * @param {Amount} amount
- * @param {AssetKind} [assetKind] - assetKind of the value
+ * @param {import('@agoric/ertp/src/types.js').Amount} amount
+ * @param {import('@agoric/ertp/src/types.js').AssetKind} [assetKind] - assetKind of the value
  * @param {number} [decimalPlaces] - places to move the decimal to the
  * right in the string
  * @param {number} [placesToShow] - places after the decimal to show
diff --git a/packages/ui-components/src/display/natValue/stringifyRatioAsFraction.js b/packages/ui-components/src/display/natValue/stringifyRatioAsFraction.js
index 66ee71570bf..4cd31b07461 100644
--- a/packages/ui-components/src/display/natValue/stringifyRatioAsFraction.js
+++ b/packages/ui-components/src/display/natValue/stringifyRatioAsFraction.js
@@ -3,16 +3,13 @@
 import { assert } from '@agoric/assert';
 import { isNatValue } from '@agoric/ertp';
 
-// eslint-disable-next-line import/no-extraneous-dependencies
-import '@agoric/zoe/exported.js';
-
 import { stringifyNat } from './stringifyNat.js';
 
 const PLACES_TO_SHOW = 2;
 
 /**
- * @param {Ratio} ratio
- * @param {(brand: Brand) => number | undefined } getDecimalPlaces
+ * @param {import('./stringifyRatioAsPercent.js').Ratio} ratio
+ * @param {(brand: import('@agoric/ertp/src/types.js').Brand) => number | undefined } getDecimalPlaces
  * @param {number} [numPlacesToShow]
  * @param {number} [denomPlacesToShow]
  * @returns {string}
diff --git a/packages/ui-components/src/display/natValue/stringifyRatioAsPercent.js b/packages/ui-components/src/display/natValue/stringifyRatioAsPercent.js
index dceb6587b0d..e3fdd2c004b 100644
--- a/packages/ui-components/src/display/natValue/stringifyRatioAsPercent.js
+++ b/packages/ui-components/src/display/natValue/stringifyRatioAsPercent.js
@@ -1,17 +1,22 @@
 // @ts-check
 
-import { assert, details } from '@agoric/assert';
-import '@agoric/zoe/exported.js';
-
 import { captureNum } from './helpers/captureNum.js';
 import { roundToDecimalPlaces } from './helpers/roundToDecimalPlaces.js';
 
+const { details } = assert;
+
 const PERCENT_BASE = 100n;
 const PLACES_TO_SHOW = 0;
 
+/**
+ * @typedef {object} Ratio
+ * @property {import('@agoric/ertp/src/types.js').Amount<'nat'>} numerator
+ * @property {import('@agoric/ertp/src/types.js').Amount<'nat'>} denominator
+ */
+
 /**
  * @param {Ratio} ratio
- * @param {(brand: Brand) => number | undefined } getDecimalPlaces
+ * @param {(brand: import('@agoric/ertp/src/types.js').Brand) => number | undefined } getDecimalPlaces
  * @param {number} [placesToShow]
  * @returns {string}
  */
diff --git a/packages/ui-components/src/index.js b/packages/ui-components/src/index.js
index 393b2d3b95d..b63c7983450 100644
--- a/packages/ui-components/src/index.js
+++ b/packages/ui-components/src/index.js
@@ -1,3 +1,6 @@
+// @ts-check
+/// <reference types="ses"/>
+
 /* eslint-disable import/no-unresolved */
 export { default as makeNatAmountInput } from './components/NatAmountInput.js';
 // eslint-disable-next-line import/no-unresolved
diff --git a/packages/vat-data/src/far-class-utils.js b/packages/vat-data/src/far-class-utils.js
index 0c627c67558..a61615336f6 100644
--- a/packages/vat-data/src/far-class-utils.js
+++ b/packages/vat-data/src/far-class-utils.js
@@ -1,3 +1,4 @@
+// @ts-check
 import { initEmpty } from '@agoric/store';
 
 import { provideKindHandle } from './kind-utils.js';
@@ -11,7 +12,8 @@ import {
 
 /** @template L,R @typedef {import('@endo/eventual-send').RemotableBrand<L, R>} RemotableBrand */
 /** @template T @typedef {import('@endo/eventual-send').ERef<T>} ERef */
-/** @typedef {import('@agoric/store').InterfaceGuard} InterfaceGuard */
+// FIXME import InterfaceGuard from @agoric/store
+/** @typedef {*} InterfaceGuard */
 /** @typedef {import('./types.js').Baggage} Baggage */
 /** @template T @typedef {import('./types.js').DefineKindOptions<T>} DefineKindOptions */
 /** @template T @typedef {import('./types.js').KindFacet<T>} KindFacet */
@@ -197,6 +199,8 @@ export const vivifyFarInstance = (
     options,
   );
 
+  // eslint-disable-next-line @typescript-eslint/prefer-ts-expect-error -- https://github.com/Agoric/agoric-sdk/issues/4620
+  // @ts-ignore could be instantiated with an arbitrary type
   return provide(baggage, `the_${kindName}`, () => makeSingleton());
 };
 harden(vivifyFarInstance);
diff --git a/packages/vat-data/src/index.js b/packages/vat-data/src/index.js
index 4d5c7bc0432..0e41ced012c 100644
--- a/packages/vat-data/src/index.js
+++ b/packages/vat-data/src/index.js
@@ -1,3 +1,4 @@
+// @ts-check
 /// <reference types="ses"/>
 export * from './vat-data-bindings.js';
 export * from './kind-utils.js';
diff --git a/packages/vat-data/src/kind-utils.js b/packages/vat-data/src/kind-utils.js
index 9062e8a0ec2..33a3fc66cd8 100644
--- a/packages/vat-data/src/kind-utils.js
+++ b/packages/vat-data/src/kind-utils.js
@@ -1,3 +1,4 @@
+// @ts-check
 import {
   provide,
   defineDurableKind,
diff --git a/packages/wallet/api/src/findOrMakeInvitation.js b/packages/wallet/api/src/findOrMakeInvitation.js
index 0959c058747..0a9c5723095 100644
--- a/packages/wallet/api/src/findOrMakeInvitation.js
+++ b/packages/wallet/api/src/findOrMakeInvitation.js
@@ -1,3 +1,4 @@
+// @ts-check
 import { assert, details as X, q } from '@agoric/assert';
 import { E } from '@endo/eventual-send';
 import { passStyleOf } from '@endo/marshal';
@@ -19,11 +20,11 @@ const assertFirstCapASCII = str => {
 };
 
 /**
- * @param {Amount} invitationPurseBalance
+ * @param {Amount<'set'>} invitationPurseBalance
  * @param {object} query
  * @param {Board} query.board
  * @param {string} query.boardId
- * @returns {Array}
+ * @returns {Promise<Array>}
  * @deprecated
  */
 const findByBoardId = async (invitationPurseBalance, { board, boardId }) => {
@@ -40,7 +41,7 @@ const findByBoardId = async (invitationPurseBalance, { board, boardId }) => {
 // An invitation matching the query parameters is already expected
 // to be deposited in the default Zoe invitation purse
 /**
- * @param {Amount} invitationPurseBalance
+ * @param {Amount<'set'>} invitationPurseBalance
  * @param {Record<string, any>} kvs
  */
 const findByKeyValuePairs = async (invitationPurseBalance, kvs) => {
diff --git a/packages/wallet/ui/package.json b/packages/wallet/ui/package.json
index 963ddf13178..d0b96cd78b1 100644
--- a/packages/wallet/ui/package.json
+++ b/packages/wallet/ui/package.json
@@ -66,7 +66,7 @@
     "build:ses": "cp ../../../node_modules/ses/dist/lockdown.umd.js public/",
     "build:react": "react-app-rewired build",
     "lint": "run-s --continue-on-error lint:*",
-    "lint:types": "tsc --maxNodeModuleJsDepth 3 -p jsconfig.json",
+    "lint:types": "tsc --maxNodeModuleJsDepth 0 -p jsconfig.json",
     "lint:eslint": "eslint '**/*.{js,jsx}'",
     "lint-fix": "yarn lint:eslint --fix",
     "test": "CI=true react-app-rewired test",
diff --git a/packages/wallet/ui/src/contexts/Provider.jsx b/packages/wallet/ui/src/contexts/Provider.jsx
index 158c365df1c..0d2e1277ee0 100644
--- a/packages/wallet/ui/src/contexts/Provider.jsx
+++ b/packages/wallet/ui/src/contexts/Provider.jsx
@@ -126,6 +126,7 @@ const Provider = ({ children }) => {
   const [issuers, setIssuers] = useReducer(issuersReducer, null);
   const [issuerSuggestions, setIssuerSuggestions] = useState(null);
   const [services, setServices] = useState(null);
+  /** @type {any} */
   const [backend, setBackend] = useState(null);
   const [schemaActions, setSchemaActions] = useState(null);
   const [connectionComponent, setConnectionComponent] = useState(null);
@@ -274,7 +275,6 @@ const Provider = ({ children }) => {
         throw e;
       }
     };
-    // @ts-expect-error backend may be null
     setSchemaActions(E.get(backend).actions);
     for (const [prop, setter] of backendSetters.entries()) {
       const iterator = E.get(backend)[prop];
@@ -289,7 +289,6 @@ const Provider = ({ children }) => {
       }).catch(rethrowIfNotCancelled);
     }
 
-    // @ts-expect-error backend may be null
     const issuerSuggestionsNotifier = E.get(backend).issuerSuggestions;
     observeIterator(issuerSuggestionsNotifier, {
       fail: rethrowIfNotCancelled,
diff --git a/packages/wallet/ui/src/index.jsx b/packages/wallet/ui/src/index.jsx
index 783a6fc2436..682f3cfdd48 100644
--- a/packages/wallet/ui/src/index.jsx
+++ b/packages/wallet/ui/src/index.jsx
@@ -1,5 +1,8 @@
+// @ts-check
+/// <reference types="ses"/>
 import '@endo/eventual-send/shim';
 
+import React from 'react';
 import ReactDOM from 'react-dom';
 import { BrowserRouter as Router } from 'react-router-dom';
 import {
@@ -24,6 +27,7 @@ const appTheme = createTheme({
     success: {
       main: 'rgb(76, 175, 80)',
     },
+    // @ts-expect-error unknown property
     cancel: {
       main: '#595959',
     },
diff --git a/packages/zoe/src/contractFacet/types.js b/packages/zoe/src/contractFacet/types.js
index eb5487c7f8b..8938c3b7874 100644
--- a/packages/zoe/src/contractFacet/types.js
+++ b/packages/zoe/src/contractFacet/types.js
@@ -1,3 +1,4 @@
+// @ts-check
 /// <reference types="ses"/>
 
 // XXX can be tighter than 'any'
@@ -39,7 +40,7 @@
  * @property {(issuer: Issuer) => Brand} getBrandForIssuer
  * @property {(brand: Brand) => Issuer} getIssuerForBrand
  * @property {GetAssetKindByBrand} getAssetKind
- * @property {<K extends AssetKind>(keyword: Keyword, assetKind?: K, displayInfo?: AdditionalDisplayInfo) => Promise<ZCFMint<K>>} makeZCFMint
+ * @property {<K extends AssetKind = 'nat'>(keyword: Keyword, assetKind?: K, displayInfo?: AdditionalDisplayInfo) => Promise<ZCFMint<K>>} makeZCFMint
  * @property {ZCFRegisterFeeMint} registerFeeMint
  * @property {ZCFMakeEmptySeatKit} makeEmptySeatKit
  * @property {SetTestJig} setTestJig
@@ -85,8 +86,13 @@
  */
 
 /**
- * @template {object} [OR=unknown] OR is OfferResult
- * @callback MakeInvitation
+ * @typedef {<R>(
+ *   offerHandler: OfferHandler<R>,
+ *   description: string,
+ *   customProperties?: object,
+ *   proposalShape?: Pattern,
+ * ) => Promise<Invitation<Awaited<R>>>
+ * } MakeInvitation
  *
  * Make a credible Zoe invitation for a particular smart contract
  * indicated by the `instance` in the details of the invitation. Zoe
@@ -97,12 +103,11 @@
  * getting in the `customProperties`. `customProperties` will be
  * placed in the details of the invitation.
  *
- * @param {OfferHandler<OR>} offerHandler - a contract specific function
+ * @param offerHandler - a contract specific function
  * that handles the offer, such as saving it or performing a trade
- * @param {string} description
- * @param {object=} customProperties
- * @param {Pattern} [proposalShape]
- * @returns {Promise<Invitation<OR>>}
+ * @param description
+ * @param [customProperties]
+ * @param [proposalShape]
  */
 
 /**
@@ -110,7 +115,7 @@
  * @param {Keyword} keyword
  * @param {FeeMintAccess} allegedFeeMintAccess - an object that
  * purports to be the object that grants access to the fee mint
- * @returns {Promise<ZCFMint>
+ * @returns {Promise<ZCFMint<'nat'>>}
  */
 
 /**
@@ -218,12 +223,15 @@
 
 /**
  * API for a contract start function.
- * FIXME before merge: assumes synchronous
  *
- * @template {object} [PF] Public facet
- * @template {object} [CF] Creator facet
- * @template {object} [CT] Custom terms
- * @template {object} [PA] Private args
+ * CAVEAT: assumes synchronous
+ *
+ * @deprecated define function signature directly
+ *
+ * @template {object} [PF=any] Public facet
+ * @template {object} [CF=any] Creator facet
+ * @template {object} [CT=any] Custom terms
+ * @template {object} [PA=any] Private args
  * @callback ContractStartFn
  * @param {ZCF<CT>} zcf
  * @param {PA} privateArgs
diff --git a/packages/zoe/src/contractFacet/zcfZygote.js b/packages/zoe/src/contractFacet/zcfZygote.js
index 42d3917a5e5..4af02ee4232 100644
--- a/packages/zoe/src/contractFacet/zcfZygote.js
+++ b/packages/zoe/src/contractFacet/zcfZygote.js
@@ -150,6 +150,7 @@ export const makeZCFZygote = async (
       assetKind,
       displayInfo,
     );
+    // @ts-expect-error could be instantiated with a different subtype
     return zcfMintFactory.makeZCFMintInternal(keyword, zoeMint);
   };
 
@@ -161,6 +162,7 @@ export const makeZCFZygote = async (
       keyword,
       feeMintAccess,
     );
+    // @ts-expect-error could be instantiated with a different subtype
     return zcfMintFactory.makeZCFMintInternal(keyword, zoeMint);
   };
 
@@ -182,6 +184,7 @@ export const makeZCFZygote = async (
       return record;
     },
     makeInvitation: (
+      // @ts-expect-error xxx arbitrary subtype
       offerHandler = Far('default offer handler', () => {}),
       description,
       customProperties = harden({}),
diff --git a/packages/zoe/src/contractSupport/statistics.js b/packages/zoe/src/contractSupport/statistics.js
index 5ea2ed8fbe7..932cdb9e387 100644
--- a/packages/zoe/src/contractSupport/statistics.js
+++ b/packages/zoe/src/contractSupport/statistics.js
@@ -1,3 +1,4 @@
+// @ts-check
 /**
  * @template T
  * @typedef {object} TypedMath
diff --git a/packages/zoe/src/contractSupport/zoeHelpers.js b/packages/zoe/src/contractSupport/zoeHelpers.js
index 6f828fc5bca..b53727d61d9 100644
--- a/packages/zoe/src/contractSupport/zoeHelpers.js
+++ b/packages/zoe/src/contractSupport/zoeHelpers.js
@@ -293,7 +293,7 @@ const reverse = (keywordRecord = {}) => {
  * @param {ZCF} zcf
  *   Zoe Contract Facet for contractA
  *
- * @param {ERef<Invitation<A, R>>} invitation
+ * @param {ERef<Invitation<R, A>>} invitation
  *   Invitation to contractB
  *
  * @param {KeywordKeywordRecord=} keywordMapping
diff --git a/packages/zoe/src/contracts/callSpread/types.js b/packages/zoe/src/contracts/callSpread/types.js
index 158d723fbb9..409e8e3f9fb 100644
--- a/packages/zoe/src/contracts/callSpread/types.js
+++ b/packages/zoe/src/contracts/callSpread/types.js
@@ -1,3 +1,4 @@
+// @ts-check
 /**
  * @typedef {'long' | 'short'} PositionKind
  */
diff --git a/packages/zoe/src/contracts/loan/types.js b/packages/zoe/src/contracts/loan/types.js
index 6526f4a4445..74ec24e7069 100644
--- a/packages/zoe/src/contracts/loan/types.js
+++ b/packages/zoe/src/contracts/loan/types.js
@@ -1,3 +1,4 @@
+// @ts-check
 /**
  * @typedef {Notifier<Timestamp>} PeriodNotifier
  *
diff --git a/packages/zoe/src/contracts/otcDesk.js b/packages/zoe/src/contracts/otcDesk.js
index 4147ebca83c..9d7fba4a974 100644
--- a/packages/zoe/src/contracts/otcDesk.js
+++ b/packages/zoe/src/contracts/otcDesk.js
@@ -66,7 +66,7 @@ const start = zcf => {
    * @returns {Promise<Payment>}
    */
   const makeQuote = async (price, assets, timeAuthority, deadline) => {
-    /** @type {{ creatorInvitation: Invitation<unknown, Payment>} } */
+    /** @type {{ creatorInvitation: Invitation<Payment>} } */
     const { creatorInvitation } = await E(zoe).startInstance(
       coveredCallInstallation,
       zcf.getTerms().issuers,
@@ -84,6 +84,7 @@ const start = zcf => {
       },
     });
 
+    /** @type {{ userSeatPromise: Promise<UserSeat<Payment>>}} */
     const { userSeatPromise: coveredCallUserSeat } = await offerTo(
       zcf,
       creatorInvitation,
diff --git a/packages/zoe/src/contracts/priceAggregatorTypes.js b/packages/zoe/src/contracts/priceAggregatorTypes.js
index 18129083e6c..67187fe244e 100644
--- a/packages/zoe/src/contracts/priceAggregatorTypes.js
+++ b/packages/zoe/src/contracts/priceAggregatorTypes.js
@@ -1,3 +1,4 @@
+// @ts-check
 /**
  * @typedef {object} OracleAdmin
  * @property {() => Promise<void>} delete
diff --git a/packages/zoe/src/contracts/types.js b/packages/zoe/src/contracts/types.js
index c1df139ad2c..b1e8dee0269 100644
--- a/packages/zoe/src/contracts/types.js
+++ b/packages/zoe/src/contracts/types.js
@@ -1,3 +1,4 @@
+// @ts-check
 /**
  * @typedef {object} SellItemsPublicFacet
  * @property {() => Issuer} getItemsIssuer
diff --git a/packages/zoe/src/types.js b/packages/zoe/src/types.js
index 7b6bfe65e66..b0e17137c12 100644
--- a/packages/zoe/src/types.js
+++ b/packages/zoe/src/types.js
@@ -1,3 +1,4 @@
+// @ts-check
 /// <reference types="ses"/>
 
 /**
@@ -29,8 +30,9 @@
  * @property {Installation} installation
  * @property {Instance} instance
  * @property {AnyTerms} terms - contract parameters
- 
- *
+ */
+
+/**
  * @template {AssetKind} [K=AssetKind]
  * @typedef {object} IssuerRecord
  * @property {Brand<K>} brand
@@ -39,11 +41,10 @@
  * @property {any} [displayInfo]
  *
  * @typedef {AmountKeywordRecord} Allocation
- * @typedef {Record<Keyword,AmountMath>} AmountMathKeywordRecord
  */
 
 /**
- * @template [OfferArgs]
- * @template [OfferResult]
+ * @template {object} [R=unknown] Offer result
+ * @template {object} [A=never] Offer args
  * @typedef {Payment<'set'>} Invitation
  */
diff --git a/packages/zoe/src/zoeService/offer/offer.js b/packages/zoe/src/zoeService/offer/offer.js
index bcc87071b7c..2bd217890cd 100644
--- a/packages/zoe/src/zoeService/offer/offer.js
+++ b/packages/zoe/src/zoeService/offer/offer.js
@@ -82,6 +82,7 @@ export const makeOfferMethod = (
       offerArgs,
     );
     // AWAIT ///
+    // @ts-expect-error cast
     return userSeat;
   };
   return offer;
diff --git a/packages/zoe/src/zoeService/types.js b/packages/zoe/src/zoeService/types.js
index 0dcd4ab02c9..3f670008b92 100644
--- a/packages/zoe/src/zoeService/types.js
+++ b/packages/zoe/src/zoeService/types.js
@@ -1,3 +1,4 @@
+// @ts-check
 /// <reference types="ses"/>
 
 /**
@@ -48,7 +49,7 @@
  * code breaks.
  * @property {GetConfiguration} getConfiguration
  * @property {GetBundleIDFromInstallation} getBundleIDFromInstallation
- * @property {GetProposalShapeForInvitation} getProposalShapeForInvitation
+ * @property {(invitationHandle: InvitationHandle) => Pattern | undefined} getProposalShapeForInvitation
  */
 
 /**
@@ -151,13 +152,18 @@
  * Verify that an alleged Invitation is real, and return the Bundle ID it
  * will use for contract code.
  *
- * @param {ERef<Installation>}
+ * @param {ERef<Installation>} allegedInstallation
  * @returns {Promise<BundleID>}
  */
 
 /**
- * @template {object} [OR=any]
- * @callback Offer
+ * @typedef {<A, R>(
+ *   invitation: ERef<Invitation<R, A>>,
+ *   proposal?: Proposal,
+ *   paymentKeywordRecord?: PaymentPKeywordRecord,
+ *   offerArgs?: A,
+ *   ) => Promise<UserSeat<R>>
+ * } Offer
  *
  * To redeem an invitation, the user normally provides a proposal (their
  * rules for the offer) as well as payments to be escrowed by Zoe.  If
@@ -172,12 +178,6 @@
  * `paymentKeywordRecord` is a record with keywords as keys, and the
  * values are the actual payments to be escrowed. A payment is
  * expected for every rule under `give`.
- *
- * @param {ERef<Invitation<OR>>} invitation
- * @param {Proposal=} proposal
- * @param {PaymentPKeywordRecord=} paymentKeywordRecord
- * @param {object=} offerArgs
- * @returns {Promise<UserSeat<OR>>} seat
  */
 
 /**
diff --git a/packages/zoe/test/unitTests/contracts/test-priceAggregatorChainlink.js b/packages/zoe/test/unitTests/contracts/test-priceAggregatorChainlink.js
index 51abcfd8361..ac410bb0aa4 100644
--- a/packages/zoe/test/unitTests/contracts/test-priceAggregatorChainlink.js
+++ b/packages/zoe/test/unitTests/contracts/test-priceAggregatorChainlink.js
@@ -1,6 +1,6 @@
-// @ts-nocheck
+// @ts-check
 // eslint-disable-next-line import/no-extraneous-dependencies
-import { test } from '@agoric/zoe/tools/prepare-test-env-ava.js';
+import { test as unknownTest } from '@agoric/zoe/tools/prepare-test-env-ava.js';
 
 import path from 'path';
 
@@ -17,6 +17,9 @@ import buildManualTimer from '../../../tools/manualTimer.js';
 import '../../../exported.js';
 import '../../../src/contracts/exported.js';
 
+/** @type {import('ava').TestFn<any>} */
+const test = unknownTest;
+
 /**
  * @callback MakeFakePriceOracle
  * @param {ExecutionContext} t
@@ -42,8 +45,9 @@ const oraclePath = `${dirname}/../../../src/contracts/oracle.js`;
 const aggregatorPath = `${dirname}/../../../src/contracts/priceAggregatorChainlink.js`;
 
 test.before(
+  // comment to maintain formatting for git blame
   'setup aggregator and oracles',
-  /** @param {ExecutionContext} ot */ async ot => {
+  async ot => {
     // Outside of tests, we should use the long-lived Zoe on the
     // testnet. In this test, we must create a new Zoe.
     const { admin, vatAdminState } = makeFakeVatAdmin();
@@ -73,6 +77,7 @@ test.before(
       /** @type {OracleHandler} */
       const oracleHandler = Far('OracleHandler', {
         async onQuery({ increment }, _fee) {
+          // @ts-expect-error xxx
           valueOut += increment;
           return harden({
             reply: `${valueOut}`,
@@ -134,7 +139,7 @@ test.before(
   },
 );
 
-test('basic', /** @param {ExecutionContext} t */ async t => {
+test('basic', async t => {
   const { makeFakePriceOracle, zoe } = t.context;
 
   const maxSubmissionCount = 1000;
@@ -211,7 +216,7 @@ test('basic', /** @param {ExecutionContext} t */ async t => {
   t.deepEqual(round3Attempt1.answer, 5000n);
 });
 
-test('timeout', /** @param {ExecutionContext} t */ async t => {
+test('timeout', async t => {
   const { makeFakePriceOracle, zoe } = t.context;
 
   const maxSubmissionCount = 1000;
@@ -281,7 +286,7 @@ test('timeout', /** @param {ExecutionContext} t */ async t => {
   t.deepEqual(round3Attempt1.answer, 2000n);
 });
 
-test('issue check', /** @param {ExecutionContext} t */ async t => {
+test('issue check', async t => {
   const { makeFakePriceOracle, zoe } = t.context;
 
   const maxSubmissionCount = 1000;
@@ -339,7 +344,7 @@ test('issue check', /** @param {ExecutionContext} t */ async t => {
   t.deepEqual(round2Attempt1.answer, 2000n);
 });
 
-test('supersede', /** @param {ExecutionContext} t */ async t => {
+test('supersede', async t => {
   const { makeFakePriceOracle, zoe } = t.context;
 
   const maxSubmissionCount = 1000;
@@ -405,7 +410,7 @@ test('supersede', /** @param {ExecutionContext} t */ async t => {
   }
 });
 
-test('interleaved', /** @param {ExecutionContext} t */ async t => {
+test('interleaved', async t => {
   const { makeFakePriceOracle, zoe } = t.context;
 
   const maxSubmissionCount = 3;
@@ -543,7 +548,7 @@ test('interleaved', /** @param {ExecutionContext} t */ async t => {
   t.deepEqual(round6Attempt1.answer, 5000n);
 });
 
-test('larger', /** @param {ExecutionContext} t */ async t => {
+test('larger', async t => {
   const { makeFakePriceOracle, zoe } = t.context;
 
   const maxSubmissionCount = 1000;
@@ -626,7 +631,7 @@ test('larger', /** @param {ExecutionContext} t */ async t => {
   t.deepEqual(round2Attempt1.answer, 600n);
 });
 
-test('suggest', /** @param {ExecutionContext} t */ async t => {
+test('suggest', async t => {
   const { makeFakePriceOracle, zoe } = t.context;
 
   const maxSubmissionCount = 1000;
diff --git a/packages/zoe/test/unitTests/test-fakePriceAuthority.js b/packages/zoe/test/unitTests/test-fakePriceAuthority.js
index 2c185fb0a7d..1965df99d52 100644
--- a/packages/zoe/test/unitTests/test-fakePriceAuthority.js
+++ b/packages/zoe/test/unitTests/test-fakePriceAuthority.js
@@ -130,6 +130,7 @@ test('priceAuthority quoteWhenGTE', async t => {
     .quoteWhenGTE(moola(1n), bucks(40n))
     .then(quote => {
       const quoteInAmount = quote.quoteAmount.value[0];
+      // @ts-expect-error could be TimestampRecord
       t.is(4n, manualTimer.getCurrentTimestamp());
       t.is(4n, quoteInAmount.timestamp);
       assertAmountsEqual(t, bucks(40n), quoteInAmount.amountOut);
@@ -156,6 +157,7 @@ test('priceAuthority quoteWhenLT', async t => {
     .quoteWhenLT(moola(1n), bucks(30n))
     .then(quote => {
       const quoteInAmount = quote.quoteAmount.value[0];
+      // @ts-expect-error could be TimestampRecord
       t.is(3n, manualTimer.getCurrentTimestamp());
       t.is(3n, quoteInAmount.timestamp);
       assertAmountsEqual(t, bucks(29n), quoteInAmount.amountOut);
@@ -181,6 +183,7 @@ test('priceAuthority quoteWhenGT', async t => {
     .quoteWhenGT(moola(1n), bucks(40n))
     .then(quote => {
       const quoteInAmount = quote.quoteAmount.value[0];
+      // @ts-expect-error could be TimestampRecord
       t.is(3n, manualTimer.getCurrentTimestamp());
       t.is(3n, quoteInAmount.timestamp);
       assertAmountsEqual(t, bucks(41n), quoteInAmount.amountOut);
@@ -207,6 +210,7 @@ test('priceAuthority quoteWhenLTE', async t => {
     .then(quote => {
       const quoteInAmount = quote.quoteAmount.value[0];
       t.is(4n, quoteInAmount.timestamp);
+      // @ts-expect-error could be TimestampRecord
       t.is(4n, manualTimer.getCurrentTimestamp());
       assertAmountsEqual(t, bucks(25n), quoteInAmount.amountOut);
       assertAmountsEqual(t, moola(1n), quoteInAmount.amountIn);
diff --git a/packages/zoe/test/unitTests/test-manualTimer.js b/packages/zoe/test/unitTests/test-manualTimer.js
index d0306ef7ace..0d229fc43a1 100644
--- a/packages/zoe/test/unitTests/test-manualTimer.js
+++ b/packages/zoe/test/unitTests/test-manualTimer.js
@@ -23,6 +23,7 @@ test('manualTimer makeNotifier', async t => {
   await Promise.resolve();
   await manualTimer.tick();
   const update2 = await p2;
+  // @ts-expect-error could be TimestampRecord
   t.truthy(BigInt(update2.updateCount) > BigInt(update1.updateCount));
   t.truthy(update2.value > update1.value);
 });
diff --git a/packages/zoe/test/unitTests/zcf/test-zcf.js b/packages/zoe/test/unitTests/zcf/test-zcf.js
index ea04fb202c8..7ffc08cae9b 100644
--- a/packages/zoe/test/unitTests/zcf/test-zcf.js
+++ b/packages/zoe/test/unitTests/zcf/test-zcf.js
@@ -769,7 +769,7 @@ test(`zcfSeat.isOfferSafe from zcf.makeEmptySeatKit`, async t => {
  * @param {Keyword} zcfMintKeyword
  * @param {ZCFSeat} zcfSeat
  * @param {Keyword} gainsKeyword
- * @param {AmountValue} gainsValue
+ * @param {bigint} gainsValue
  * @returns {Promise<IssuerRecord>}
  */
 const allocateEasy = async (
diff --git a/packages/zoe/tools/internal-types.js b/packages/zoe/tools/internal-types.js
index 325d196a9c5..8cb41ab2fb7 100644
--- a/packages/zoe/tools/internal-types.js
+++ b/packages/zoe/tools/internal-types.js
@@ -1,3 +1,4 @@
+// @ts-check
 /**
  * @typedef {object} ManualTimerAdmin
  * @property {(msg?: string) => Promise<void>} tick
@@ -5,9 +6,5 @@
  */
 
 /**
- * @typedef { import('@agoric/swingset-vat').ManualTimer } SwingSetManualTimer
- */
-
-/**
- * @typedef {ManualTimerAdmin & SwingSetManualTimer} ManualTimer
+ * @typedef {TimerService & ManualTimerAdmin} ManualTimer
  */
diff --git a/packages/zoe/tools/types.js b/packages/zoe/tools/types.js
index d79c243ed5c..57e3e519b97 100644
--- a/packages/zoe/tools/types.js
+++ b/packages/zoe/tools/types.js
@@ -1,3 +1,4 @@
+// @ts-check
 /**
  * @typedef {object} PriceQuote
  * @property {Amount<'set'>} quoteAmount