diff --git a/packages/fast-usdc/src/exos/liquidity-pool.js b/packages/fast-usdc/src/exos/liquidity-pool.js
index 4d43d7dfe710..4dcfdad6bd18 100644
--- a/packages/fast-usdc/src/exos/liquidity-pool.js
+++ b/packages/fast-usdc/src/exos/liquidity-pool.js
@@ -1,58 +1,76 @@
-import {
-  AmountMath,
-  AmountShape,
-  PaymentShape,
-  RatioShape,
-} from '@agoric/ertp';
+import { AmountMath, AmountShape } from '@agoric/ertp';
 import {
   makeRecorderTopic,
   TopicsRecordShape,
 } from '@agoric/zoe/src/contractSupport/topics.js';
-import { depositToSeat } from '@agoric/zoe/src/contractSupport/zoeHelpers.js';
 import { SeatShape } from '@agoric/zoe/src/typeGuards.js';
 import { M } from '@endo/patterns';
 import { Fail, q } from '@endo/errors';
 import {
+  borrowCalc,
   depositCalc,
   makeParity,
+  repayCalc,
   withdrawCalc,
-  withFees,
 } from '../pool-share-math.js';
-import { makeProposalShapes } from '../type-guards.js';
+import {
+  makeNatAmountShape,
+  makeProposalShapes,
+  PoolMetricsShape,
+} from '../type-guards.js';
 
 /**
  * @import {Zone} from '@agoric/zone';
- * @import {Remote, TypedPattern} from '@agoric/internal'
+ * @import {Remote} from '@agoric/internal'
  * @import {StorageNode} from '@agoric/internal/src/lib-chainStorage.js'
- * @import {MakeRecorderKit, RecorderKit} from '@agoric/zoe/src/contractSupport/recorder.js'
+ * @import {MakeRecorderKit} from '@agoric/zoe/src/contractSupport/recorder.js'
  * @import {USDCProposalShapes, ShareWorth} from '../pool-share-math.js'
+ * @import {PoolStats} from '../types.js';
  */
 
-const { add, isEqual } = AmountMath;
+const { add, isEqual, makeEmpty } = AmountMath;
 
 /** @param {Brand} brand */
 const makeDust = brand => AmountMath.make(brand, 1n);
 
 /**
- * Use of pool-share-math in offer handlers below assumes that
- * the pool balance represented by the USDC allocation in poolSeat
- * is the same as the pool balance represented by the numerator
- * of shareWorth.
+ * Verifies that the total pool balance (unencumbered + encumbered) matches the
+ * shareWorth numerator. The total pool balance consists of:
+ * 1. unencumbered balance - USDC available in the pool for borrowing
+ * 2. encumbered balance - USDC currently lent out
  *
- * Well, almost: they're the same modulo the dust used
- * to initialize shareWorth with a non-zero denominator.
+ * A negligible `dust` amount is used to initialize shareWorth with a non-zero
+ * denominator. It must remain in the pool at all times.
  *
  * @param {ZCFSeat} poolSeat
  * @param {ShareWorth} shareWorth
  * @param {Brand} USDC
+ * @param {Amount<'nat'>} encumberedBalance
  */
-const checkPoolBalance = (poolSeat, shareWorth, USDC) => {
-  const available = poolSeat.getAmountAllocated('USDC', USDC);
+const checkPoolBalance = (poolSeat, shareWorth, USDC, encumberedBalance) => {
+  const unencumberedBalance = poolSeat.getAmountAllocated('USDC', USDC);
   const dust = makeDust(USDC);
-  isEqual(add(available, dust), shareWorth.numerator) ||
-    Fail`🚨 pool balance ${q(available)} inconsistent with shareWorth ${q(shareWorth)}`;
+  const grossBalance = add(add(unencumberedBalance, dust), encumberedBalance);
+  isEqual(grossBalance, shareWorth.numerator) ||
+    Fail`🚨 pool balance ${q(unencumberedBalance)} and encumbered balance ${q(encumberedBalance)} inconsistent with shareWorth ${q(shareWorth)}`;
 };
 
+/**
+ * @typedef {{
+ *  Principal: Amount<'nat'>;
+ *  PoolFee: Amount<'nat'>;
+ *  ContractFee: Amount<'nat'>;
+ * }} RepayAmountKWR
+ */
+
+/**
+ * @typedef {{
+ *  Principal: Payment<'nat'>;
+ *  PoolFee: Payment<'nat'>;
+ *  ContractFee: Payment<'nat'>;
+ * }} RepayPaymentKWR
+ */
+
 /**
  * @param {Zone} zone
  * @param {ZCF} zcf
@@ -65,11 +83,25 @@ export const prepareLiquidityPoolKit = (zone, zcf, USDC, tools) => {
   return zone.exoClassKit(
     'Liquidity Pool',
     {
-      feeSink: M.interface('feeSink', {
-        receive: M.call(AmountShape, PaymentShape).returns(M.promise()),
+      borrower: M.interface('borrower', {
+        getBalance: M.call().returns(AmountShape),
+        borrow: M.call(
+          SeatShape,
+          harden({ USDC: makeNatAmountShape(USDC, 1n) }),
+        ).returns(),
+      }),
+      repayer: M.interface('repayer', {
+        repay: M.call(
+          SeatShape,
+          harden({
+            Principal: makeNatAmountShape(USDC, 1n),
+            PoolFee: makeNatAmountShape(USDC, 0n),
+            ContractFee: makeNatAmountShape(USDC, 0n),
+          }),
+        ).returns(),
       }),
       external: M.interface('external', {
-        publishShareWorth: M.call().returns(),
+        publishPoolMetrics: M.call().returns(),
       }),
       depositHandler: M.interface('depositHandler', {
         handle: M.call(SeatShape, M.any()).returns(M.promise()),
@@ -89,60 +121,147 @@ export const prepareLiquidityPoolKit = (zone, zcf, USDC, tools) => {
      */
     (shareMint, node) => {
       const { brand: PoolShares } = shareMint.getIssuerRecord();
-      const proposalShapes = makeProposalShapes({ USDC, PoolShares });
+      const proposalShapes = makeProposalShapes({
+        USDC,
+        PoolShares,
+      });
       const shareWorth = makeParity(makeDust(USDC), PoolShares);
       const { zcfSeat: poolSeat } = zcf.makeEmptySeatKit();
-      const shareWorthRecorderKit = tools.makeRecorderKit(node, RatioShape);
+      const { zcfSeat: feeSeat } = zcf.makeEmptySeatKit();
+      const poolMetricsRecorderKit = tools.makeRecorderKit(
+        node,
+        PoolMetricsShape,
+      );
+      /** used for `checkPoolBalance` invariant */
+      const encumberedBalance = makeEmpty(USDC);
+      /** @type {PoolStats} */
+      const poolStats = harden({
+        totalBorrows: makeEmpty(USDC),
+        totalContractFees: makeEmpty(USDC),
+        totalPoolFees: makeEmpty(USDC),
+        totalRepays: makeEmpty(USDC),
+      });
       return {
-        shareMint,
-        shareWorth,
+        encumberedBalance,
+        feeSeat,
+        poolStats,
+        poolMetricsRecorderKit,
         poolSeat,
         PoolShares,
         proposalShapes,
-        shareWorthRecorderKit,
+        shareMint,
+        shareWorth,
       };
     },
     {
-      feeSink: {
+      borrower: {
+        getBalance() {
+          const { poolSeat } = this.state;
+          return poolSeat.getAmountAllocated('USDC', USDC);
+        },
         /**
-         * @param {Amount<'nat'>} amount
-         * @param {Payment<'nat'>} payment
+         * @param {ZCFSeat} toSeat
+         * @param {{ USDC: Amount<'nat'>}} amountKWR
          */
-        async receive(amount, payment) {
-          const { poolSeat, shareWorth } = this.state;
-          const { external } = this.facets;
-          await depositToSeat(
-            zcf,
-            poolSeat,
-            harden({ USDC: amount }),
-            harden({ USDC: payment }),
+        borrow(toSeat, amountKWR) {
+          const { encumberedBalance, poolSeat, poolStats } = this.state;
+
+          // Validate amount is available in pool
+          const post = borrowCalc(
+            amountKWR.USDC,
+            poolSeat.getAmountAllocated('USDC', USDC),
+            encumberedBalance,
+            poolStats,
           );
-          this.state.shareWorth = withFees(shareWorth, amount);
-          external.publishShareWorth();
+
+          // COMMIT POINT
+          try {
+            zcf.atomicRearrange(harden([[poolSeat, toSeat, amountKWR]]));
+          } catch (cause) {
+            const reason = Error('🚨 cannot commit borrow', { cause });
+            console.error(reason.message, cause);
+            zcf.shutdownWithFailure(reason);
+          }
+
+          Object.assign(this.state, post);
+          this.facets.external.publishPoolMetrics();
         },
+        // TODO method to repay failed `LOA.deposit()`
       },
+      repayer: {
+        /**
+         * @param {ZCFSeat} fromSeat
+         * @param {RepayAmountKWR} amounts
+         */
+        repay(fromSeat, amounts) {
+          const {
+            encumberedBalance,
+            feeSeat,
+            poolSeat,
+            poolStats,
+            shareWorth,
+          } = this.state;
+          checkPoolBalance(poolSeat, shareWorth, USDC, encumberedBalance);
+
+          // determine new shareWorth, encumberedBalance, and poolStats
+          const post = repayCalc(
+            shareWorth,
+            amounts,
+            encumberedBalance,
+            poolStats,
+          );
+
+          const { ContractFee, ...rest } = amounts;
+
+          // COMMIT POINT
+          try {
+            zcf.atomicRearrange(
+              harden([
+                [
+                  fromSeat,
+                  poolSeat,
+                  rest,
+                  { USDC: add(amounts.PoolFee, amounts.Principal) },
+                ],
+                [fromSeat, feeSeat, { ContractFee }, { USDC: ContractFee }],
+              ]),
+            );
+          } catch (cause) {
+            const reason = Error('🚨 cannot commit repay', { cause });
+            console.error(reason.message, cause);
+            zcf.shutdownWithFailure(reason);
+          }
 
+          Object.assign(this.state, post);
+          this.facets.external.publishPoolMetrics();
+        },
+      },
       external: {
-        publishShareWorth() {
-          const { shareWorth } = this.state;
-          const { recorder } = this.state.shareWorthRecorderKit;
+        publishPoolMetrics() {
+          const { poolStats, shareWorth, encumberedBalance } = this.state;
+          const { recorder } = this.state.poolMetricsRecorderKit;
           // Consumers of this .write() are off-chain / outside the VM.
           // And there's no way to recover from a failed write.
           // So don't await.
-          void recorder.write(shareWorth);
+          void recorder.write({
+            encumberedBalance,
+            shareWorth,
+            ...poolStats,
+          });
         },
       },
 
       depositHandler: {
         /** @param {ZCFSeat} lp */
         async handle(lp) {
-          const { shareWorth, shareMint, poolSeat } = this.state;
+          const { shareWorth, shareMint, poolSeat, encumberedBalance } =
+            this.state;
           const { external } = this.facets;
 
           /** @type {USDCProposalShapes['deposit']} */
           // @ts-expect-error ensured by proposalShape
           const proposal = lp.getProposal();
-          checkPoolBalance(poolSeat, shareWorth, USDC);
+          checkPoolBalance(poolSeat, shareWorth, USDC, encumberedBalance);
           const post = depositCalc(shareWorth, proposal);
 
           // COMMIT POINT
@@ -165,20 +284,21 @@ export const prepareLiquidityPoolKit = (zone, zcf, USDC, tools) => {
             console.error(reason.message, cause);
             zcf.shutdownWithFailure(reason);
           }
-          external.publishShareWorth();
+          external.publishPoolMetrics();
         },
       },
       withdrawHandler: {
         /** @param {ZCFSeat} lp */
         async handle(lp) {
-          const { shareWorth, shareMint, poolSeat } = this.state;
+          const { shareWorth, shareMint, poolSeat, encumberedBalance } =
+            this.state;
           const { external } = this.facets;
 
           /** @type {USDCProposalShapes['withdraw']} */
           // @ts-expect-error ensured by proposalShape
           const proposal = lp.getProposal();
           const { zcfSeat: burn } = zcf.makeEmptySeatKit();
-          checkPoolBalance(poolSeat, shareWorth, USDC);
+          checkPoolBalance(poolSeat, shareWorth, USDC, encumberedBalance);
           const post = withdrawCalc(shareWorth, proposal);
 
           // COMMIT POINT
@@ -201,7 +321,7 @@ export const prepareLiquidityPoolKit = (zone, zcf, USDC, tools) => {
             console.error(reason.message, cause);
             zcf.shutdownWithFailure(reason);
           }
-          external.publishShareWorth();
+          external.publishPoolMetrics();
         },
       },
       public: {
@@ -222,18 +342,25 @@ export const prepareLiquidityPoolKit = (zone, zcf, USDC, tools) => {
           );
         },
         getPublicTopics() {
-          const { shareWorthRecorderKit } = this.state;
+          const { poolMetricsRecorderKit } = this.state;
           return {
-            shareWorth: makeRecorderTopic('shareWorth', shareWorthRecorderKit),
+            poolMetrics: makeRecorderTopic(
+              'poolMetrics',
+              poolMetricsRecorderKit,
+            ),
           };
         },
       },
     },
     {
       finish: ({ facets: { external } }) => {
-        void external.publishShareWorth();
+        void external.publishPoolMetrics();
       },
     },
   );
 };
 harden(prepareLiquidityPoolKit);
+
+/**
+ * @typedef {ReturnType<ReturnType<typeof prepareLiquidityPoolKit>>} LiquidityPoolKit
+ */
diff --git a/packages/fast-usdc/src/fast-usdc.contract.js b/packages/fast-usdc/src/fast-usdc.contract.js
index 144cb0c614c6..42c7b5d57f0e 100644
--- a/packages/fast-usdc/src/fast-usdc.contract.js
+++ b/packages/fast-usdc/src/fast-usdc.contract.js
@@ -8,6 +8,7 @@ import {
 import { provideSingleton } from '@agoric/zoe/src/contractSupport/durability.js';
 import { prepareRecorderKitMakers } from '@agoric/zoe/src/contractSupport/recorder.js';
 import { M } from '@endo/patterns';
+import { depositToSeat } from '@agoric/zoe/src/contractSupport/zoeHelpers.js';
 import { prepareAdvancer } from './exos/advancer.js';
 import { prepareLiquidityPoolKit } from './exos/liquidity-pool.js';
 import { prepareSettler } from './exos/settler.js';
@@ -24,6 +25,7 @@ const trace = makeTracer('FastUsdc');
  * @import {Zone} from '@agoric/zone';
  * @import {OperatorKit} from './exos/operator-kit.js';
  * @import {CctpTxEvidence, FeeConfig} from './types.js';
+ * @import {RepayAmountKWR, RepayPaymentKWR} from './exos/liquidity-pool.js';
  */
 
 /**
@@ -112,10 +114,29 @@ export const contract = async (zcf, privateArgs, zone, tools) => {
     async makeOperatorInvitation(operatorId) {
       return feedKit.creator.makeOperatorInvitation(operatorId);
     },
-    simulateFeesFromAdvance(amount, payment) {
-      console.log('🚧🚧 UNTIL: advance fees are implemented 🚧🚧');
+    /**
+     * @param {{ USDC: Amount<'nat'>}} amounts
+     */
+    testBorrow(amounts) {
+      console.log('🚧🚧 UNTIL: borrow is integrated 🚧🚧', amounts);
+      const { zcfSeat: tmpAssetManagerSeat } = zcf.makeEmptySeatKit();
+      // eslint-disable-next-line no-use-before-define
+      poolKit.borrower.borrow(tmpAssetManagerSeat, amounts);
+      return tmpAssetManagerSeat.getCurrentAllocation();
+    },
+    /**
+     *
+     * @param {RepayAmountKWR} amounts
+     * @param {RepayPaymentKWR} payments
+     * @returns {Promise<AmountKeywordRecord>}
+     */
+    async testRepay(amounts, payments) {
+      console.log('🚧🚧 UNTIL: repay is integrated 🚧🚧', amounts);
+      const { zcfSeat: tmpAssetManagerSeat } = zcf.makeEmptySeatKit();
+      await depositToSeat(zcf, tmpAssetManagerSeat, amounts, payments);
       // eslint-disable-next-line no-use-before-define
-      return poolKit.feeSink.receive(amount, payment);
+      poolKit.repayer.repay(tmpAssetManagerSeat, amounts);
+      return tmpAssetManagerSeat.getCurrentAllocation();
     },
   });
 
diff --git a/packages/fast-usdc/src/pool-share-math.js b/packages/fast-usdc/src/pool-share-math.js
index 01b418169335..531721ac0784 100644
--- a/packages/fast-usdc/src/pool-share-math.js
+++ b/packages/fast-usdc/src/pool-share-math.js
@@ -7,7 +7,12 @@ import {
 } from '@agoric/zoe/src/contractSupport/ratio.js';
 import { Fail, q } from '@endo/errors';
 
-const { getValue, add, isEmpty, isGTE, subtract } = AmountMath;
+const { getValue, add, isEmpty, isEqual, isGTE, subtract } = AmountMath;
+
+/**
+ * @import {PoolStats} from './types';
+ * @import {RepayAmountKWR} from './exos/liquidity-pool';
+ */
 
 /**
  * Invariant: shareWorth is the pool balance divided by shares outstanding.
@@ -120,3 +125,57 @@ export const withFees = (shareWorth, fees) => {
   const balancePost = add(shareWorth.numerator, fees);
   return makeRatioFromAmounts(balancePost, shareWorth.denominator);
 };
+
+/**
+ *
+ * @param {Amount<'nat'>} requested
+ * @param {Amount<'nat'>} poolSeatAllocation
+ * @param {Amount<'nat'>} encumberedBalance
+ * @param {PoolStats} poolStats
+ */
+export const borrowCalc = (
+  requested,
+  poolSeatAllocation,
+  encumberedBalance,
+  poolStats,
+) => {
+  // pool must never go empty
+  !isGTE(requested, poolSeatAllocation) ||
+    Fail`Cannot borrow. Requested ${q(requested)} must be less than pool balance ${q(poolSeatAllocation)}.`;
+
+  return harden({
+    encumberedBalance: add(encumberedBalance, requested),
+    poolStats: {
+      ...poolStats,
+      totalBorrows: add(poolStats.totalBorrows, requested),
+    },
+  });
+};
+
+/**
+ * @param {ShareWorth} shareWorth
+ * @param {RepayAmountKWR} amounts
+ * @param {Amount<'nat'>} encumberedBalance
+ * @param {PoolStats} poolStats
+ */
+export const repayCalc = (
+  shareWorth,
+  amounts,
+  encumberedBalance,
+  poolStats,
+) => {
+  !isGTE(amounts.Principal, encumberedBalance) ||
+    isEqual(amounts.Principal, encumberedBalance) ||
+    Fail`Cannot repay. Principal ${q(amounts.Principal)} exceeds encumberedBalance ${q(encumberedBalance)}.`;
+
+  return harden({
+    shareWorth: withFees(shareWorth, amounts.PoolFee),
+    encumberedBalance: subtract(encumberedBalance, amounts.Principal),
+    poolStats: {
+      ...poolStats,
+      totalRepays: add(poolStats.totalRepays, amounts.Principal),
+      totalPoolFees: add(poolStats.totalPoolFees, amounts.PoolFee),
+      totalContractFees: add(poolStats.totalContractFees, amounts.ContractFee),
+    },
+  });
+};
diff --git a/packages/fast-usdc/src/type-guards.js b/packages/fast-usdc/src/type-guards.js
index f4aa9db982df..677144eeffe6 100644
--- a/packages/fast-usdc/src/type-guards.js
+++ b/packages/fast-usdc/src/type-guards.js
@@ -1,4 +1,4 @@
-import { BrandShape, RatioShape } from '@agoric/ertp';
+import { AmountShape, BrandShape, RatioShape } from '@agoric/ertp';
 import { M } from '@endo/patterns';
 import { PendingTxStatus } from './constants.js';
 
@@ -6,7 +6,7 @@ import { PendingTxStatus } from './constants.js';
  * @import {TypedPattern} from '@agoric/internal';
  * @import {FastUsdcTerms} from './fast-usdc.contract.js';
  * @import {USDCProposalShapes} from './pool-share-math.js';
- * @import {CctpTxEvidence, FeeConfig, PendingTx} from './types.js';
+ * @import {CctpTxEvidence, FeeConfig, PendingTx, PoolMetrics} from './types.js';
  */
 
 /**
@@ -82,3 +82,14 @@ export const FeeConfigShape = {
   contractRate: RatioShape,
 };
 harden(FeeConfigShape);
+
+/** @type {TypedPattern<PoolMetrics>} */
+export const PoolMetricsShape = {
+  encumberedBalance: AmountShape,
+  shareWorth: RatioShape,
+  totalContractFees: AmountShape,
+  totalPoolFees: AmountShape,
+  totalBorrows: AmountShape,
+  totalRepays: AmountShape,
+};
+harden(PoolMetricsShape);
diff --git a/packages/fast-usdc/src/types.ts b/packages/fast-usdc/src/types.ts
index 6cb3a94cd624..c4b7820d4c85 100644
--- a/packages/fast-usdc/src/types.ts
+++ b/packages/fast-usdc/src/types.ts
@@ -1,5 +1,6 @@
 import type { ChainAddress } from '@agoric/orchestration';
 import type { IBCChannelID } from '@agoric/vats';
+import type { Amount } from '@agoric/ertp';
 import type { PendingTxStatus } from './constants.js';
 
 export type EvmHash = `0x${string}`;
@@ -42,4 +43,16 @@ export type FeeConfig = {
   contractRate: Ratio;
 };
 
+export interface PoolStats {
+  totalBorrows: Amount<'nat'>;
+  totalContractFees: Amount<'nat'>;
+  totalPoolFees: Amount<'nat'>;
+  totalRepays: Amount<'nat'>;
+}
+
+export interface PoolMetrics extends PoolStats {
+  encumberedBalance: Amount<'nat'>;
+  shareWorth: Ratio;
+}
+
 export type * from './constants.js';
diff --git a/packages/fast-usdc/src/utils/fees.js b/packages/fast-usdc/src/utils/fees.js
index 9019a54f8b49..08b14c819919 100644
--- a/packages/fast-usdc/src/utils/fees.js
+++ b/packages/fast-usdc/src/utils/fees.js
@@ -9,6 +9,7 @@ const { add, isGTE, min, subtract } = AmountMath;
 /**
  * @import {Amount} from '@agoric/ertp';
  * @import {FeeConfig} from '../types.js';
+ * @import {RepayAmountKWR} from '../exos/liquidity-pool.js';
  */
 
 /** @param {FeeConfig} feeConfig */
@@ -42,7 +43,7 @@ export const makeFeeTools = feeConfig => {
      * Calculate the split of fees between pool and contract.
      *
      * @param {Amount<'nat'>} requested
-     * @returns {{ Principal: Amount<'nat'>, PoolFee: Amount<'nat'>, ContractFee: Amount<'nat'> }} an {@link AmountKeywordRecord}
+     * @returns {RepayAmountKWR} an {@link AmountKeywordRecord}
      * @throws {Error} if requested does not exceed fees
      */
     calculateSplit(requested) {
diff --git a/packages/fast-usdc/test/fast-usdc.contract.test.ts b/packages/fast-usdc/test/fast-usdc.contract.test.ts
index e2f85526ce81..93aa94ec9a3d 100644
--- a/packages/fast-usdc/test/fast-usdc.contract.test.ts
+++ b/packages/fast-usdc/test/fast-usdc.contract.test.ts
@@ -2,7 +2,10 @@ import { test } from '@agoric/zoe/tools/prepare-test-env-ava.js';
 import type { ExecutionContext } from 'ava';
 
 import { AmountMath } from '@agoric/ertp/src/amountMath.js';
-import { inspectMapStore } from '@agoric/internal/src/testing-utils.js';
+import {
+  eventLoopIteration,
+  inspectMapStore,
+} from '@agoric/internal/src/testing-utils.js';
 import {
   divideBy,
   multiplyBy,
@@ -12,9 +15,14 @@ import { setUpZoeForTest } from '@agoric/zoe/tools/setup-zoe.js';
 import { E } from '@endo/far';
 import path from 'path';
 import fetchedChainInfo from '@agoric/orchestration/src/fetched-chain-info.js';
+import { objectMap } from '@endo/patterns';
+import { deeplyFulfilledObject } from '@agoric/internal';
+import type { Subscriber } from '@agoric/notifier';
 import { MockCctpTxEvidences } from './fixtures.js';
 import { commonSetup } from './supports.js';
 import type { FastUsdcTerms } from '../src/fast-usdc.contract.js';
+import { makeFeeTools } from '../src/utils/fees.js';
+import type { PoolMetrics } from '../src/types.js';
 
 const dirname = path.dirname(new URL(import.meta.url).pathname);
 
@@ -140,7 +148,7 @@ const makeLpTools = (
     publicFacet,
   }: {
     zoe: ZoeService;
-    subscriber: ERef<Subscriber<Ratio>>;
+    subscriber: ERef<Subscriber<PoolMetrics>>;
     publicFacet: StartedInstanceKit<StartFn>['publicFacet'];
     terms: StandardTerms & FastUsdcTerms;
   },
@@ -154,7 +162,9 @@ const makeLpTools = (
     let deposited = AmountMath.makeEmpty(usdc.brand);
     const me = harden({
       deposit: async (qty: bigint) => {
-        const { value: shareWorth } = await E(subscriber).getUpdateSince();
+        const {
+          value: { shareWorth },
+        } = await E(subscriber).getUpdateSince();
         const give = { USDC: usdc.make(qty) };
         const proposal = harden({
           give,
@@ -178,7 +188,9 @@ const makeLpTools = (
           .getCurrentAmount()
           .then(a => a as Amount<'nat'>);
         const give = { PoolShare: scaleAmount(portion, myShares) };
-        const { value: shareWorth } = await E(subscriber).getUpdateSince();
+        const {
+          value: { shareWorth },
+        } = await E(subscriber).getUpdateSince();
         const myUSDC = multiplyBy(myShares, shareWorth);
         const myFees = subtract(myUSDC, deposited);
         t.log(name, 'sees fees earned', ...logAmt(myFees));
@@ -194,13 +206,12 @@ const makeLpTools = (
           .then(pmt => E(zoe).offer(toWithdraw, proposal, { PoolShare: pmt }))
           .then(seat => E(seat).getPayout('USDC'));
         const amt = await E(usdcPurse).deposit(usdcPmt);
-        t.log(name, 'withdaw payout', ...logAmt(amt));
+        t.log(name, 'withdraw payout', ...logAmt(amt));
         t.true(isGTE(amt, proposal.want.USDC));
       },
     });
     return me;
   };
-
   const purseOf = (value: bigint) =>
     E(terms.issuers.USDC)
       .makeEmptyPurse()
@@ -215,6 +226,7 @@ const makeLpTools = (
 test('LP deposits, earns fees, withdraws', async t => {
   const common = await commonSetup(t);
   const {
+    commonPrivateArgs,
     brands: { usdc },
     utils,
   } = common;
@@ -224,7 +236,7 @@ test('LP deposits, earns fees, withdraws', async t => {
   const terms = await E(zoe).getTerms(instance);
 
   const { subscriber } = E.get(
-    E.get(E(publicFacet).getPublicTopics()).shareWorth,
+    E.get(E(publicFacet).getPublicTopics()).poolMetrics,
   );
 
   const { makeLP, purseOf } = makeLpTools(t, common, {
@@ -233,23 +245,266 @@ test('LP deposits, earns fees, withdraws', async t => {
     terms,
     zoe,
   });
-
   const lps = {
     alice: makeLP('Alice', purseOf(60n)),
     bob: makeLP('Bob', purseOf(50n)),
   };
 
   await Promise.all([lps.alice.deposit(60n), lps.bob.deposit(40n)]);
+
   {
-    const feeAmt = usdc.make(25n);
-    t.log('contract accrues some amount of fees:', ...logAmt(feeAmt));
-    const feePmt = await utils.pourPayment(feeAmt);
-    await E(creatorFacet).simulateFeesFromAdvance(feeAmt, feePmt);
+    t.log('simulate borrow and repay so pool accrues fees');
+    const feeTools = makeFeeTools(commonPrivateArgs.feeConfig);
+    const requestedAmount = usdc.make(50n);
+    const splits = feeTools.calculateSplit(requestedAmount);
+
+    const amt = await E(creatorFacet).testBorrow({ USDC: splits.Principal });
+    t.deepEqual(
+      amt.USDC,
+      splits.Principal,
+      'testBorrow returns requested amount',
+    );
+    const repayPayments = await deeplyFulfilledObject(
+      objectMap(splits, utils.pourPayment),
+    );
+    const remaining = await E(creatorFacet).testRepay(splits, repayPayments);
+    for (const r of Object.values(remaining)) {
+      t.is(r.value, 0n, 'testRepay consumes all payments');
+    }
   }
-
   await Promise.all([lps.alice.withdraw(0.2), lps.bob.withdraw(0.8)]);
 });
 
+test('LP borrow', async t => {
+  const common = await commonSetup(t);
+  const {
+    brands: { usdc },
+  } = common;
+
+  const { instance, creatorFacet, publicFacet, zoe } =
+    await startContract(common);
+  const terms = await E(zoe).getTerms(instance);
+
+  const { subscriber } = E.get(
+    E.get(E(publicFacet).getPublicTopics()).poolMetrics,
+  );
+
+  const { makeLP, purseOf } = makeLpTools(t, common, {
+    publicFacet,
+    subscriber,
+    terms,
+    zoe,
+  });
+  const lps = {
+    alice: makeLP('Alice', purseOf(100n)),
+  };
+  // seed pool with funds
+  await lps.alice.deposit(100n);
+
+  const { value } = await E(subscriber).getUpdateSince();
+  const { shareWorth, encumberedBalance } = value;
+  const poolSeatAllocation = subtract(
+    subtract(shareWorth.numerator, encumberedBalance),
+    usdc.make(1n),
+  );
+  t.log('Attempting to borrow entire pool seat allocation', poolSeatAllocation);
+  await t.throwsAsync(
+    E(creatorFacet).testBorrow({ USDC: poolSeatAllocation }),
+    {
+      message: /Cannot borrow/,
+    },
+    'borrow fails when requested equals pool seat allocation',
+  );
+
+  await t.throwsAsync(
+    E(creatorFacet).testBorrow({ USDC: usdc.make(200n) }),
+    {
+      message: /Cannot borrow/,
+    },
+    'borrow fails when requested exceeds pool seat allocation',
+  );
+
+  await t.throwsAsync(E(creatorFacet).testBorrow({ USDC: usdc.make(0n) }), {
+    message: /arg 1: USDC: value: "\[0n\]" - Must be >= "\[1n\]"/,
+  });
+
+  await t.throwsAsync(
+    E(creatorFacet).testBorrow(
+      // @ts-expect-error intentionally incorrect KW
+      { Fee: usdc.make(1n) },
+    ),
+    {
+      message: /Must have missing properties \["USDC"\]/,
+    },
+  );
+
+  // LPs can still withdraw (contract did not shutdown)
+  await lps.alice.withdraw(0.5);
+
+  const amt = await E(creatorFacet).testBorrow({ USDC: usdc.make(30n) });
+  t.deepEqual(amt, { USDC: usdc.make(30n) }, 'borrow succeeds');
+
+  await eventLoopIteration();
+  t.like(await E(subscriber).getUpdateSince(), {
+    value: {
+      encumberedBalance: {
+        value: 30n,
+      },
+      totalBorrows: {
+        value: 30n,
+      },
+      totalRepays: {
+        value: 0n,
+      },
+    },
+  });
+});
+
+test('LP repay', async t => {
+  const common = await commonSetup(t);
+  const {
+    commonPrivateArgs,
+    brands: { usdc },
+    utils,
+  } = common;
+
+  const { instance, creatorFacet, publicFacet, zoe } =
+    await startContract(common);
+  const terms = await E(zoe).getTerms(instance);
+
+  const { subscriber } = E.get(
+    E.get(E(publicFacet).getPublicTopics()).poolMetrics,
+  );
+  const feeTools = makeFeeTools(commonPrivateArgs.feeConfig);
+  const { makeLP, purseOf } = makeLpTools(t, common, {
+    publicFacet,
+    subscriber,
+    terms,
+    zoe,
+  });
+  const lps = {
+    alice: makeLP('Alice', purseOf(100n)),
+  };
+  // seed pool with funds
+  await lps.alice.deposit(100n);
+
+  // borrow funds from pool to increase encumbered balance
+  await E(creatorFacet).testBorrow({ USDC: usdc.make(50n) });
+
+  {
+    t.log('cannot repay more than encumbered balance');
+    const repayAmounts = feeTools.calculateSplit(usdc.make(100n));
+    const repayPayments = await deeplyFulfilledObject(
+      objectMap(repayAmounts, utils.pourPayment),
+    );
+    await t.throwsAsync(
+      E(creatorFacet).testRepay(repayAmounts, repayPayments),
+      {
+        message: /Cannot repay/,
+      },
+    );
+  }
+
+  {
+    const pmt = utils.pourPayment(usdc.make(50n));
+    await t.throwsAsync(
+      E(creatorFacet).testRepay(
+        // @ts-expect-error intentionally incorrect KWR
+        { USDC: usdc.make(50n) },
+        { USDC: pmt },
+      ),
+      {
+        message:
+          /Must have missing properties \["Principal","PoolFee","ContractFee"\]/,
+      },
+    );
+  }
+  {
+    const pmt = utils.pourPayment(usdc.make(50n));
+    await t.throwsAsync(
+      E(creatorFacet).testRepay(
+        // @ts-expect-error intentionally incorrect KWR
+        { Principal: usdc.make(50n) },
+        { Principal: pmt },
+      ),
+      {
+        message: /Must have missing properties \["PoolFee","ContractFee"\]/,
+      },
+    );
+  }
+  {
+    const amts = {
+      Principal: usdc.make(0n),
+      ContractFee: usdc.make(0n),
+      PoolFee: usdc.make(0n),
+    };
+    const pmts = await deeplyFulfilledObject(
+      objectMap(amts, utils.pourPayment),
+    );
+    await t.throwsAsync(E(creatorFacet).testRepay(amts, pmts), {
+      message: /arg 1: Principal: value: "\[0n\]" - Must be >= "\[1n\]"/,
+    });
+  }
+
+  {
+    t.log('repay succeeds with no Pool or Contract Fee');
+    const amts = {
+      Principal: usdc.make(25n),
+      ContractFee: usdc.make(0n),
+      PoolFee: usdc.make(0n),
+    };
+    const pmts = await deeplyFulfilledObject(
+      objectMap(amts, utils.pourPayment),
+    );
+    const repayResult = await E(creatorFacet).testRepay(amts, pmts);
+
+    for (const r of Object.values(repayResult)) {
+      t.is(r.value, 0n, 'testRepay consumes all payments');
+    }
+  }
+
+  const amts = {
+    Principal: usdc.make(25n),
+    ContractFee: usdc.make(1n),
+    PoolFee: usdc.make(2n),
+  };
+  const pmts = await deeplyFulfilledObject(objectMap(amts, utils.pourPayment));
+  const repayResult = await E(creatorFacet).testRepay(amts, pmts);
+
+  for (const r of Object.values(repayResult)) {
+    t.is(r.value, 0n, 'testRepay consumes all payments');
+  }
+
+  await eventLoopIteration();
+  t.like(await E(subscriber).getUpdateSince(), {
+    value: {
+      encumberedBalance: {
+        value: 0n,
+      },
+      totalBorrows: {
+        value: 50n,
+      },
+      totalRepays: {
+        value: 50n,
+      },
+      totalContractFees: {
+        value: 1n,
+      },
+      totalPoolFees: {
+        value: 2n,
+      },
+      shareWorth: {
+        numerator: {
+          value: 103n, // 100n (alice lp) + 1n (dust) + 2n (pool fees)
+        },
+      },
+    },
+  });
+
+  // LPs can still withdraw (contract did not shutdown)
+  await lps.alice.withdraw(1);
+});
+
 test('baggage', async t => {
   const {
     brands: { usdc },
diff --git a/packages/fast-usdc/test/pool-share-math.test.ts b/packages/fast-usdc/test/pool-share-math.test.ts
index 9451c92e266f..6796d9b8a2e3 100644
--- a/packages/fast-usdc/test/pool-share-math.test.ts
+++ b/packages/fast-usdc/test/pool-share-math.test.ts
@@ -7,8 +7,10 @@ import {
 } from '@agoric/zoe/src/contractSupport/ratio.js';
 import { mustMatch } from '@endo/patterns';
 import {
+  borrowCalc,
   depositCalc,
   makeParity,
+  repayCalc,
   withdrawCalc,
   withFees,
 } from '../src/pool-share-math.js';
@@ -295,3 +297,146 @@ testProp(
     );
   },
 );
+
+const makeInitialPoolStats = () => ({
+  totalBorrows: makeEmpty(brands.USDC),
+  totalRepays: makeEmpty(brands.USDC),
+  totalPoolFees: makeEmpty(brands.USDC),
+  totalContractFees: makeEmpty(brands.USDC),
+});
+
+test('basic borrow calculation', t => {
+  const { USDC } = brands;
+  const requested = make(USDC, 100n);
+  const poolSeatAllocation = make(USDC, 200n);
+  const encumberedBalance = make(USDC, 50n);
+  const poolStats = makeInitialPoolStats();
+
+  const result = borrowCalc(
+    requested,
+    poolSeatAllocation,
+    encumberedBalance,
+    poolStats,
+  );
+
+  t.deepEqual(
+    result.encumberedBalance,
+    make(USDC, 150n),
+    'Outstanding lends should increase by borrowed amount',
+  );
+  t.deepEqual(
+    result.poolStats.totalBorrows,
+    make(USDC, 100n),
+    'Total borrows should increase by borrowed amount',
+  );
+  t.deepEqual(
+    Object.keys(result.poolStats),
+    Object.keys(poolStats),
+    'borrowCalc returns all poolStats fields',
+  );
+});
+
+test('borrow fails when requested exceeds or equals pool seat allocation', t => {
+  const { USDC } = brands;
+  const requested = make(USDC, 200n);
+  const poolSeatAllocation = make(USDC, 100n);
+  const encumberedBalance = make(USDC, 0n);
+  const poolStats = makeInitialPoolStats();
+
+  t.throws(
+    () =>
+      borrowCalc(requested, poolSeatAllocation, encumberedBalance, poolStats),
+    {
+      message: /Cannot borrow/,
+    },
+  );
+  t.throws(
+    () => borrowCalc(requested, make(USDC, 200n), encumberedBalance, poolStats),
+    {
+      message: /Cannot borrow/,
+    },
+    'throw when request equals pool seat allocation',
+  );
+  t.notThrows(() =>
+    borrowCalc(requested, make(USDC, 201n), encumberedBalance, poolStats),
+  );
+});
+
+test('basic repay calculation', t => {
+  const { USDC } = brands;
+  const shareWorth = makeParity(make(USDC, 1n), brands.PoolShares);
+  const amounts = {
+    Principal: make(USDC, 100n),
+    PoolFee: make(USDC, 10n),
+    ContractFee: make(USDC, 5n),
+  };
+  const encumberedBalance = make(USDC, 200n);
+  const poolStats = makeInitialPoolStats();
+
+  const result = repayCalc(shareWorth, amounts, encumberedBalance, poolStats);
+
+  t.deepEqual(
+    result.encumberedBalance,
+    make(USDC, 100n),
+    'Outstanding lends should decrease by principal',
+  );
+  t.deepEqual(
+    result.poolStats.totalRepays,
+    amounts.Principal,
+    'Total repays should increase by principal',
+  );
+  t.deepEqual(
+    result.poolStats.totalPoolFees,
+    amounts.PoolFee,
+    'Total pool fees should increase by pool fee',
+  );
+  t.deepEqual(
+    result.poolStats.totalContractFees,
+    amounts.ContractFee,
+    'Total contract fees should increase by contract fee',
+  );
+  t.deepEqual(
+    result.poolStats.totalBorrows,
+    poolStats.totalBorrows,
+    'Total borrows should remain unchanged',
+  );
+  t.deepEqual(
+    result.shareWorth.numerator,
+    make(USDC, 11n),
+    'Share worth numerator should increase by pool fee',
+  );
+  t.deepEqual(
+    Object.keys(result.poolStats),
+    Object.keys(poolStats),
+    'repayCalc returns all poolStats fields',
+  );
+});
+
+test('repay fails when principal exceeds encumbered balance', t => {
+  const { USDC } = brands;
+
+  const shareWorth = makeParity(make(USDC, 1n), brands.PoolShares);
+  const amounts = {
+    Principal: make(USDC, 200n),
+    PoolFee: make(USDC, 10n),
+    ContractFee: make(USDC, 5n),
+  };
+  const encumberedBalance = make(USDC, 100n);
+  const poolStats = {
+    ...makeInitialPoolStats(),
+    totalBorrows: make(USDC, 100n),
+  };
+
+  t.throws(() => repayCalc(shareWorth, amounts, encumberedBalance, poolStats), {
+    message: /Cannot repay/,
+  });
+
+  t.notThrows(
+    () =>
+      repayCalc(shareWorth, amounts, make(USDC, 200n), {
+        ...makeInitialPoolStats(),
+        totalBorrows: make(USDC, 200n),
+      }),
+    'repay succeeds when principal equals encumbered balance',
+  );
+});
diff --git a/packages/fast-usdc/test/snapshots/fast-usdc.contract.test.ts.md b/packages/fast-usdc/test/snapshots/fast-usdc.contract.test.ts.md
index 16063f382245..8421aa9cc3cb 100644
--- a/packages/fast-usdc/test/snapshots/fast-usdc.contract.test.ts.md
+++ b/packages/fast-usdc/test/snapshots/fast-usdc.contract.test.ts.md
@@ -53,10 +53,11 @@ Generated by [AVA](https://avajs.dev).
           'Transaction Feed_kindHandle': 'Alleged: kind',
         },
         'Liquidity Pool kit': {
+          borrower: Object @Alleged: Liquidity Pool borrower {},
           depositHandler: Object @Alleged: Liquidity Pool depositHandler {},
           external: Object @Alleged: Liquidity Pool external {},
-          feeSink: Object @Alleged: Liquidity Pool feeSink {},
           public: Object @Alleged: Liquidity Pool public {},
+          repayer: Object @Alleged: Liquidity Pool repayer {},
           withdrawHandler: Object @Alleged: Liquidity Pool withdrawHandler {},
         },
         'Liquidity Pool_kindHandle': 'Alleged: kind',
diff --git a/packages/fast-usdc/test/snapshots/fast-usdc.contract.test.ts.snap b/packages/fast-usdc/test/snapshots/fast-usdc.contract.test.ts.snap
index 1aaf6a60fc12..7658bda5e411 100644
Binary files a/packages/fast-usdc/test/snapshots/fast-usdc.contract.test.ts.snap and b/packages/fast-usdc/test/snapshots/fast-usdc.contract.test.ts.snap differ