diff --git a/packages/contracts/contracts/compound/CErc20RetireDelegate.sol b/packages/contracts/contracts/compound/CErc20RetireDelegate.sol
new file mode 100644
index 000000000..5d6ef0e62
--- /dev/null
+++ b/packages/contracts/contracts/compound/CErc20RetireDelegate.sol
@@ -0,0 +1,67 @@
+// SPDX-License-Identifier: UNLICENSED
+pragma solidity >=0.8.0;
+
+import "./CErc20Delegate.sol";
+
+/**
+ * @title CErc20RetireDelegate
+ * @notice One-shot remediation delegate used to retire a frozen/abandoned market.
+ *
+ * A market whose interest-rate model returns a per-block borrow rate above
+ * `borrowRateMaxMantissa` while `cash > totalFees` reverts every accruing entrypoint with
+ * `"!borrowRate"` (see CTokenFirstExtension._accrueInterestHypothetical). That freezes
+ * `mint`/`redeem`/`borrow`/`repay` and even `_setInterestRateModel`/`_withdraw*Fees`, which all
+ * call `accrueInterest()` first. The only admin lever that does not accrue is
+ * `CErc20Delegator._setImplementationSafe`, whose `_becomeImplementation(data)` hook runs during
+ * the upgrade. This delegate uses that hook to repair such a market.
+ *
+ * `_becomeImplementation` sweeps the entire underlying balance to a treasury address and zeroes
+ * the accounting (reserves, admin/ionic fees, borrows). With `totalBorrows == 0` utilization is 0,
+ * so the borrow rate drops to the base rate, `accrueInterest` stops reverting, and the market can
+ * then be unlisted via `Comptroller._unsupportMarket` (which requires `totalSupply() == 0`).
+ *
+ * Intended single-use flow (target market only — see tasks/market/retire-frozen.ts):
+ *   1. FeeDistributor owner: `_setCErc20DelegateExtensions(thisDelegate, [CTokenFirstExtension, thisDelegate])`
+ *   2. Pool admin:          `market._setImplementationSafe(thisDelegate, abi.encode(treasury))`
+ *   3. Pool admin:          `comptroller._unsupportMarket(market)`
+ *   4. (optional) Pool admin: `market._upgrade()` to restore the standard delegate.
+ *
+ * WARNING: this writes down protocol accounting and moves funds. It must NEVER be registered as
+ * the latest delegate for any delegateType, and must only be applied to a market that has been
+ * confirmed abandoned (totalSupply == 0). Validate the full sequence on a fork first.
+ */
+contract CErc20RetireDelegate is CErc20Delegate {
+  event MarketRetired(address indexed underlyingToken, address indexed treasury, uint256 sweptAmount);
+
+  /**
+   * @notice One-shot retirement hook invoked by the delegator during `_setImplementationSafe`.
+   * @param data abi.encode(address treasury) — recipient of the swept underlying.
+   */
+  function _becomeImplementation(bytes memory data) public override {
+    require(msg.sender == address(this) || hasAdminRights(), "!self || !admin");
+
+    address treasury = abi.decode(data, (address));
+    require(treasury != address(0), "!treasury");
+
+    // Sweep the full underlying balance to the treasury using the inherited safe-transfer path.
+    uint256 sweptAmount = getCashInternal();
+    if (sweptAmount > 0) {
+      doTransferOut(treasury, sweptAmount);
+    }
+
+    // Zero the degenerate accounting so utilization (and therefore the borrow rate) returns to a
+    // sane value; with totalBorrows == 0 the rate is the base rate and accrueInterest no longer
+    // reverts with "!borrowRate". totalBorrows is written off because the market is being retired.
+    totalReserves = 0;
+    totalAdminFees = 0;
+    totalIonicFees = 0;
+    totalBorrows = 0;
+    accrualBlockNumber = block.number;
+
+    emit MarketRetired(underlying, treasury, sweptAmount);
+  }
+
+  function contractType() external pure override returns (string memory) {
+    return "CErc20RetireDelegate";
+  }
+}
diff --git a/packages/contracts/contracts/test/RetireFrozenMarketTest.t.sol b/packages/contracts/contracts/test/RetireFrozenMarketTest.t.sol
new file mode 100644
index 000000000..cab5d85df
--- /dev/null
+++ b/packages/contracts/contracts/test/RetireFrozenMarketTest.t.sol
@@ -0,0 +1,76 @@
+// SPDX-License-Identifier: UNLICENSED
+pragma solidity ^0.8.0;
+
+import { UpgradesBaseTest } from "./UpgradesBaseTest.sol";
+import { DiamondExtension } from "../ionic/DiamondExtension.sol";
+import { ICErc20 } from "../compound/CTokenInterfaces.sol";
+import { IonicComptroller } from "../compound/ComptrollerInterface.sol";
+import { EIP20Interface } from "../compound/EIP20Interface.sol";
+import { CErc20RetireDelegate } from "../compound/CErc20RetireDelegate.sol";
+
+/**
+ * @notice Fork test for retiring the frozen `ionmsUSD` market on Base.
+ *
+ * The market `0x5BE1Cb6CB3C9bfd16Db43ed4f6c081FA9783dd1C` reverts every accruing call with
+ * `"!borrowRate"`: its reserves+fees grew to ~= cash+borrows, collapsing the utilization
+ * denominator so the IRM returns a per-block rate far above `borrowRateMaxMantissa`. `totalSupply`
+ * is 0 (no suppliers). This test proves the retirement sequence works end-to-end against live state:
+ * upgrade to `CErc20RetireDelegate` (sweep + zero accounting, no accrual) → unfreeze → unlist.
+ *
+ * Run with the Base fork:
+ *   TEST_RUN_CHAINID=8453 BASE_MAINNET_RPC_URL=... forge test --mc RetireFrozenMarketTest -vvv
+ */
+contract RetireFrozenMarketTest is UpgradesBaseTest {
+  ICErc20 internal constant ionmsUSD = ICErc20(0x5BE1Cb6CB3C9bfd16Db43ed4f6c081FA9783dd1C);
+
+  function testRetireFrozenIonmsUSD() public fork(BASE_MAINNET) {
+    address treasury = makeAddr("retireTreasury");
+    EIP20Interface underlyingToken = EIP20Interface(ionmsUSD.underlying());
+    IonicComptroller pool = ionmsUSD.comptroller();
+
+    // 1. Pre-conditions: abandoned (no suppliers) and frozen on every accruing call.
+    assertEq(ionmsUSD.totalSupply(), 0, "expected no suppliers (abandoned market)");
+    uint256 cashBefore = underlyingToken.balanceOf(address(ionmsUSD));
+    assertGt(cashBefore, 0, "expected underlying cash to sweep");
+
+    vm.expectRevert(bytes("!borrowRate"));
+    ionmsUSD.accrueInterest();
+
+    // 2. Deploy the one-shot retire delegate and register its extensions (FeeDistributor owner).
+    CErc20RetireDelegate retireImpl = new CErc20RetireDelegate();
+    DiamondExtension[] memory exts = new DiamondExtension[](2);
+    exts[0] = marketExt; // shared CTokenFirstExtension (deployed in UpgradesBaseTest.afterForkSetUp)
+    exts[1] = retireImpl;
+    vm.prank(ffd.owner());
+    ffd._setCErc20DelegateExtensions(address(retireImpl), exts);
+
+    // 3. Upgrade the market to the retire delegate (pool/ionic admin). Runs _becomeImplementation
+    //    WITHOUT accruing: sweeps the underlying to treasury and zeroes the accounting.
+    vm.prank(address(ffd));
+    ionmsUSD._setImplementationSafe(address(retireImpl), abi.encode(treasury));
+
+    // 4. Post-conditions: funds swept, accounting zeroed, market no longer frozen.
+    assertEq(underlyingToken.balanceOf(treasury), cashBefore, "treasury should receive all swept cash");
+    assertEq(underlyingToken.balanceOf(address(ionmsUSD)), 0, "market underlying balance should be 0");
+    assertEq(ionmsUSD.totalReserves(), 0, "totalReserves should be zeroed");
+    assertEq(ionmsUSD.totalAdminFees(), 0, "totalAdminFees should be zeroed");
+    assertEq(ionmsUSD.totalIonicFees(), 0, "totalIonicFees should be zeroed");
+    assertEq(ionmsUSD.totalBorrows(), 0, "totalBorrows should be written off");
+    // accrueInterest must now succeed (no "!borrowRate" revert).
+    assertEq(ionmsUSD.accrueInterest(), 0, "accrueInterest should succeed after retirement");
+
+    // 5. Unlist the market from the pool (requires totalSupply == 0, still true).
+    vm.prank(pool.admin());
+    uint256 err = pool._unsupportMarket(ionmsUSD);
+    assertEq(err, 0, "unsupportMarket should succeed");
+    assertFalse(_isListed(pool, ionmsUSD), "market should be unlisted");
+  }
+
+  function _isListed(IonicComptroller pool, ICErc20 market) internal view returns (bool) {
+    ICErc20[] memory all = pool.getAllMarkets();
+    for (uint256 i = 0; i < all.length; i++) {
+      if (address(all[i]) == address(market)) return true;
+    }
+    return false;
+  }
+}
diff --git a/packages/contracts/tasks/market/index.ts b/packages/contracts/tasks/market/index.ts
index 60eaaeba3..d38ad4505 100644
--- a/packages/contracts/tasks/market/index.ts
+++ b/packages/contracts/tasks/market/index.ts
@@ -7,6 +7,7 @@ import "./deploy-dynamic-rewards-market";
 import "./deploy-static-rewards-market";
 import "./deploy";
 import "./borrow";
+import "./retire-frozen";
 import { Address } from "viem";
 import { HardhatRuntimeEnvironment } from "hardhat/types";
 
diff --git a/packages/contracts/tasks/market/retire-frozen.ts b/packages/contracts/tasks/market/retire-frozen.ts
new file mode 100644
index 000000000..a83a74134
--- /dev/null
+++ b/packages/contracts/tasks/market/retire-frozen.ts
@@ -0,0 +1,130 @@
+import { task, types } from "hardhat/config";
+import { Address, encodeAbiParameters, Hash, parseAbiParameters } from "viem";
+import { prepareAndLogTransaction } from "../../chainDeploy/helpers/logging";
+
+/**
+ * Retire a frozen/abandoned cToken market that reverts every accruing call with "!borrowRate".
+ *
+ * Such a market cannot be repaired through any accruing entrypoint (mint/redeem/borrow/repay,
+ * _setInterestRateModel, _withdraw*Fees all accrue first). The only non-accruing admin lever is
+ * `_setImplementationSafe`, so we upgrade the market to a one-shot `CErc20RetireDelegate` whose
+ * `_becomeImplementation(abi.encode(treasury))` sweeps the underlying to `treasury` and zeroes the
+ * accounting (reserves/fees/borrows). That unfreezes `accrueInterest`, after which the market can be
+ * unlisted via `_unsupportMarket` (requires totalSupply == 0).
+ *
+ * SAFETY: refuses to run unless `totalSupply == 0` (no suppliers). Validate on a fork first
+ * (see contracts/test/RetireFrozenMarketTest.t.sol).
+ *
+ * Example:
+ *   yarn hardhat market:retire-frozen --network base \
+ *     --market 0x5BE1Cb6CB3C9bfd16Db43ed4f6c081FA9783dd1C \
+ *     --treasury 0x<treasury>
+ */
+export default task("market:retire-frozen", "Retire a frozen/abandoned market: sweep funds, zero state, unlist")
+  .addParam("market", "Address of the frozen cToken market", undefined, types.string)
+  .addParam("treasury", "Recipient of the swept underlying", undefined, types.string)
+  .addOptionalParam("unsupport", "Whether to unlist the market from the pool after retiring", true, types.boolean)
+  .setAction(async ({ market, treasury, unsupport }, { viem, deployments, getNamedAccounts }) => {
+    const { deployer } = await getNamedAccounts();
+    const publicClient = await viem.getPublicClient();
+
+    const cToken = await viem.getContractAt("ICErc20", market as Address);
+
+    // --- Safety guard: only retire abandoned markets (no suppliers) ---
+    const totalSupply = await cToken.read.totalSupply();
+    if (totalSupply !== 0n) {
+      throw new Error(`Refusing to retire ${market}: totalSupply is ${totalSupply} (expected 0 — has suppliers).`);
+    }
+
+    const underlying = await cToken.read.underlying();
+    const comptrollerAddress = await cToken.read.comptroller();
+    const cash = await (await viem.getContractAt("ICErc20", underlying)).read.balanceOf([market as Address]);
+    console.log(`Retiring market ${market} (underlying ${underlying}); sweeping ${cash} to ${treasury}`);
+
+    const feeDistributor = await viem.getContractAt(
+      "FeeDistributor",
+      (await deployments.get("FeeDistributor")).address as Address
+    );
+    const cTokenFirstExtension = (await deployments.get("CTokenFirstExtension")).address as Address;
+
+    // 1. Deploy the one-shot retire delegate.
+    const retire = await deployments.deploy("CErc20RetireDelegate", {
+      from: deployer,
+      args: [],
+      log: true,
+      waitConfirmations: 1
+    });
+    if (retire.transactionHash) await publicClient.waitForTransactionReceipt({ hash: retire.transactionHash as Hash });
+    const retireDelegate = retire.address as Address;
+    console.log(`CErc20RetireDelegate: ${retireDelegate}`);
+
+    // 2. Register the retire delegate's extensions in the FeeDistributor (owner). Mirrors the
+    //    canonical [delegate, CTokenFirstExtension] registration in 03-deploy-ctokens-set-extensions.
+    const ffdOwner = await feeDistributor.read.owner();
+    const currentExts = await feeDistributor.read.getCErc20DelegateExtensions([retireDelegate]);
+    const extsArgs: [Address, Address[]] = [retireDelegate, [retireDelegate, cTokenFirstExtension]];
+    if (currentExts.length < 2 || currentExts[0] !== retireDelegate || currentExts[1] !== cTokenFirstExtension) {
+      if (ffdOwner.toLowerCase() !== deployer.toLowerCase()) {
+        await prepareAndLogTransaction({
+          contractInstance: feeDistributor,
+          functionName: "_setCErc20DelegateExtensions",
+          args: extsArgs,
+          description: "Register CErc20RetireDelegate extensions",
+          inputs: [
+            { internalType: "address", name: "cErc20Delegate", type: "address" },
+            { internalType: "address[]", name: "extensions", type: "address[]" }
+          ]
+        });
+      } else {
+        const tx = await feeDistributor.write._setCErc20DelegateExtensions(extsArgs);
+        await publicClient.waitForTransactionReceipt({ hash: tx });
+        console.log(`Registered extensions for retire delegate: ${tx}`);
+      }
+    } else {
+      console.log(`Retire delegate extensions already registered`);
+    }
+
+    // 3. Upgrade the market to the retire delegate (pool/ionic admin). This sweeps + zeroes state.
+    const becomeData = encodeAbiParameters(parseAbiParameters("address"), [treasury as Address]);
+    const cTokenDelegator = await viem.getContractAt("CErc20Delegator", market as Address);
+    const comptroller = await viem.getContractAt("IonicComptroller", comptrollerAddress as Address);
+    const poolAdmin = await comptroller.read.admin();
+    if (poolAdmin.toLowerCase() !== deployer.toLowerCase()) {
+      await prepareAndLogTransaction({
+        contractInstance: cTokenDelegator,
+        functionName: "_setImplementationSafe",
+        args: [retireDelegate, becomeData],
+        description: `Retire market ${market}: set CErc20RetireDelegate (sweep to ${treasury})`,
+        inputs: [
+          { internalType: "address", name: "implementation_", type: "address" },
+          { internalType: "bytes", name: "implementationData", type: "bytes" }
+        ]
+      });
+    } else {
+      const tx = await cTokenDelegator.write._setImplementationSafe([retireDelegate, becomeData]);
+      await publicClient.waitForTransactionReceipt({ hash: tx });
+      console.log(`Retired market (swept + zeroed) via _setImplementationSafe: ${tx}`);
+    }
+
+    // 4. Unlist the market from the pool (admin). Requires totalSupply == 0 (already enforced).
+    if (unsupport) {
+      if (poolAdmin.toLowerCase() !== deployer.toLowerCase()) {
+        await prepareAndLogTransaction({
+          contractInstance: comptroller,
+          functionName: "_unsupportMarket",
+          args: [market as Address],
+          description: `Unlist retired market ${market}`,
+          inputs: [{ internalType: "address", name: "cToken", type: "address" }]
+        });
+      } else {
+        const tx = await comptroller.write._unsupportMarket([market as Address]);
+        await publicClient.waitForTransactionReceipt({ hash: tx });
+        console.log(`Unsupported (unlisted) market: ${tx}`);
+      }
+    }
+
+    console.log(
+      `Done. If multisig transactions were queued, execute them in order: ` +
+        `(1) register extensions, (2) _setImplementationSafe, (3) _unsupportMarket.`
+    );
+  });