diff --git a/modules/abstract-lightning/package.json b/modules/abstract-lightning/package.json
index dd6e83e069..1847f495b8 100644
--- a/modules/abstract-lightning/package.json
+++ b/modules/abstract-lightning/package.json
@@ -39,7 +39,7 @@
     ]
   },
   "dependencies": {
-    "@bitgo/public-types": "6.22.0",
+    "@bitgo/public-types": "6.43.0",
     "@bitgo/sdk-core": "^38.0.0",
     "@bitgo/statics": "^58.54.0",
     "@bitgo/utxo-lib": "^11.24.0",
diff --git a/modules/bitgo/package.json b/modules/bitgo/package.json
index 13bd25bf3b..ce4fe59d0f 100644
--- a/modules/bitgo/package.json
+++ b/modules/bitgo/package.json
@@ -140,7 +140,7 @@
     "superagent": "^9.0.1"
   },
   "devDependencies": {
-    "@bitgo/public-types": "6.22.0",
+    "@bitgo/public-types": "6.43.0",
     "@bitgo/sdk-opensslbytes": "^2.1.0",
     "@bitgo/sdk-test": "^9.1.57",
     "@openpgp/web-stream-tools": "0.0.14",
diff --git a/modules/express/package.json b/modules/express/package.json
index c44cb9a9e9..52d8c8b7d0 100644
--- a/modules/express/package.json
+++ b/modules/express/package.json
@@ -60,7 +60,7 @@
     "superagent": "^9.0.1"
   },
   "devDependencies": {
-    "@bitgo/public-types": "6.22.0",
+    "@bitgo/public-types": "6.43.0",
     "@bitgo/sdk-lib-mpc": "^10.15.0",
     "@bitgo/sdk-test": "^9.1.57",
     "@types/argparse": "^1.0.36",
diff --git a/modules/sdk-coin-flrp/package.json b/modules/sdk-coin-flrp/package.json
index 9a12613156..5dec033f40 100644
--- a/modules/sdk-coin-flrp/package.json
+++ b/modules/sdk-coin-flrp/package.json
@@ -48,7 +48,7 @@
     "nock": "^13.3.1"
   },
   "dependencies": {
-    "@bitgo/public-types": "6.22.0",
+    "@bitgo/public-types": "6.43.0",
     "@bitgo/sdk-core": "^38.0.0",
     "@bitgo/secp256k1": "^1.11.0",
     "@bitgo/statics": "^58.54.0",
diff --git a/modules/sdk-coin-sol/package.json b/modules/sdk-coin-sol/package.json
index 8128e8ce49..bc7b836ca4 100644
--- a/modules/sdk-coin-sol/package.json
+++ b/modules/sdk-coin-sol/package.json
@@ -57,7 +57,7 @@
   },
   "dependencies": {
     "@bitgo/logger": "^1.4.0",
-    "@bitgo/public-types": "6.22.0",
+    "@bitgo/public-types": "6.43.0",
     "@bitgo/sdk-core": "^38.0.0",
     "@bitgo/sdk-lib-mpc": "^10.15.0",
     "@bitgo/statics": "^58.54.0",
diff --git a/modules/sdk-core/package.json b/modules/sdk-core/package.json
index 0c01439ee8..4e5edc95fa 100644
--- a/modules/sdk-core/package.json
+++ b/modules/sdk-core/package.json
@@ -40,7 +40,7 @@
     ]
   },
   "dependencies": {
-    "@bitgo/public-types": "6.22.0",
+    "@bitgo/public-types": "6.43.0",
     "@bitgo/sdk-lib-mpc": "^10.15.0",
     "@bitgo/secp256k1": "^1.11.0",
     "@bitgo/sjcl": "^1.1.0",
diff --git a/modules/sdk-core/src/bitgo/pendingApproval/pendingApproval.ts b/modules/sdk-core/src/bitgo/pendingApproval/pendingApproval.ts
index 5ca48252d4..822ef5bab4 100644
--- a/modules/sdk-core/src/bitgo/pendingApproval/pendingApproval.ts
+++ b/modules/sdk-core/src/bitgo/pendingApproval/pendingApproval.ts
@@ -31,6 +31,8 @@ type PreApproveResult = {
   halfSigned?: string;
 };
 
+// TODO(WCN-541): add optional attestation pass-through for PUT /pendingapprovals/:id (deferred
+// until multisig attestation, WCN-539, is verified end-to-end on staging).
 type ApprovePendingApprovalRequestBody = {
   state: 'approved';
   otp: string | undefined;
diff --git a/modules/sdk-core/src/bitgo/tss/common.ts b/modules/sdk-core/src/bitgo/tss/common.ts
index 7903038740..83ec34bad7 100644
--- a/modules/sdk-core/src/bitgo/tss/common.ts
+++ b/modules/sdk-core/src/bitgo/tss/common.ts
@@ -111,6 +111,8 @@ export async function sendSignatureShare(
   const urlPath = '/wallet/' + walletId + '/txrequests/' + txRequestId + addendum + '/signatureshares';
   const reqTracer = reqId || new RequestTracer();
   bitgo.setRequestTracer(reqTracer);
+  // TODO(WCN-541): add optional attestation pass-through for MPC /signatureshares, first round
+  // only (deferred until multisig attestation, WCN-539, is verified end-to-end on staging).
   return bitgo
     .post(bitgo.url(urlPath, 2))
     .send({
diff --git a/modules/sdk-core/src/bitgo/utils/tss/baseTSSUtils.ts b/modules/sdk-core/src/bitgo/utils/tss/baseTSSUtils.ts
index 2b983ccdd7..1d830a3ede 100644
--- a/modules/sdk-core/src/bitgo/utils/tss/baseTSSUtils.ts
+++ b/modules/sdk-core/src/bitgo/utils/tss/baseTSSUtils.ts
@@ -514,6 +514,8 @@ export default class BaseTssUtils<KeyShare> extends MpcUtils implements ITssUtil
     preview?: boolean,
     reqId?: IRequestTracer
   ): Promise<TxRequest> {
+    // TODO(WCN-541): add optional attestation pass-through for MPC /txrequests (deferred until
+    // multisig attestation, WCN-539, is verified end-to-end on staging).
     const whitelistedParams = {
       intent: {
         ...intentOptions,
diff --git a/modules/sdk-core/src/bitgo/wallet/BuildParams.ts b/modules/sdk-core/src/bitgo/wallet/BuildParams.ts
index a635b2057b..a7f4499828 100644
--- a/modules/sdk-core/src/bitgo/wallet/BuildParams.ts
+++ b/modules/sdk-core/src/bitgo/wallet/BuildParams.ts
@@ -64,6 +64,27 @@ export const BuildParamsOffchain = t.partial({
   idfUserId: t.unknown,
 });
 
+/**
+ * WebAuthn attestation proving a passkey user signed off on this withdrawal intent.
+ * Pure pass-through — the SDK does not validate or interpret this payload.
+ *
+ * @bitgo/public-types' TxSendBody now declares this field natively (WCN-539), so /tx/send and
+ * /tx/initiate no longer need a local copy. This one remains for BuildParams (custodial
+ * /tx/build), which has no upstream equivalent yet.
+ *
+ * TODO(WCN-541): add attestation pass-through for MPC (/txrequests, /signatureshares) and
+ * /pendingapprovals — see the TODO(WCN-541) markers in baseTSSUtils.ts, common.ts, and
+ * pendingApproval.ts.
+ */
+export const AttestationPayload = t.type({
+  signature: t.string,
+  credentialId: t.string,
+  clientDataJSON: t.string,
+  authenticatorData: t.string,
+});
+
+export type AttestationPayload = t.TypeOf<typeof AttestationPayload>;
+
 export const BuildParams = t.exact(
   t.intersection([
     BuildParamsUTXO,
@@ -135,6 +156,8 @@ export const BuildParams = t.exact(
       feeToken: t.unknown,
       // Bridging parameters for cross-chain operations (e.g., BTC to sBTC)
       bridgingParams: t.unknown,
+      // WebAuthn attestation for the withdrawal intent (WCN-539) — pass-through only.
+      attestation: AttestationPayload,
     }),
   ])
 );
diff --git a/modules/sdk-core/src/bitgo/wallet/iWallet.ts b/modules/sdk-core/src/bitgo/wallet/iWallet.ts
index a9663e6bbc..067660bcb6 100644
--- a/modules/sdk-core/src/bitgo/wallet/iWallet.ts
+++ b/modules/sdk-core/src/bitgo/wallet/iWallet.ts
@@ -38,6 +38,7 @@ import {
   TxRequest,
 } from '../utils';
 import { SerializedNtilde } from '../../account-lib/mpc/tss/ecdsa/types';
+import { AttestationPayload } from './BuildParams';
 import { IAddressBook } from '../address-book';
 import { WalletUser, AddressQueryResult } from '@bitgo/public-types';
 import { SubmitTransactionResponse } from '../inscriptionBuilder';
@@ -203,6 +204,8 @@ export interface PrebuildTransactionOptions {
   idfUserId?: string;
   idfVersion?: number;
   comment?: string;
+  /** WebAuthn attestation for the withdrawal intent (WCN-539) — pass-through only. */
+  attestation?: AttestationPayload;
   [index: string]: unknown;
   tokenName?: string;
   nftCollectionId?: string;
@@ -883,6 +886,8 @@ export interface SubmitTransactionOptions {
   };
   comment?: string;
   txRequestId?: string;
+  /** WebAuthn attestation for the withdrawal intent (WCN-539) — pass-through only. */
+  attestation?: AttestationPayload;
 }
 
 export interface SendOptions {
diff --git a/modules/sdk-core/test/unit/bitgo/wallet/BuildParams.ts b/modules/sdk-core/test/unit/bitgo/wallet/BuildParams.ts
index e88da25a62..e1f619b3ba 100644
--- a/modules/sdk-core/test/unit/bitgo/wallet/BuildParams.ts
+++ b/modules/sdk-core/test/unit/bitgo/wallet/BuildParams.ts
@@ -1,5 +1,5 @@
 import * as assert from 'assert';
-import { BuildParams } from '../../../../src/bitgo/wallet/BuildParams';
+import { BuildParams, buildParamKeys, AttestationPayload } from '../../../../src/bitgo/wallet/BuildParams';
 
 describe('BuildParams', function () {
   it('enforces codec', function () {
@@ -74,4 +74,36 @@ describe('BuildParams', function () {
       }
     );
   });
+
+  it('should whitelist attestation (WCN-539) while stripping unrelated unknown params', function () {
+    const attestation = {
+      signature: 'sig',
+      credentialId: 'cred-id',
+      clientDataJSON: 'client-data',
+      authenticatorData: 'auth-data',
+    };
+    assert.deepStrictEqual(
+      BuildParams.encode({
+        recipients: [{ amount: '10000', address: '2N9Ego9KidiZR8tMP82g6RaggQtcbR9zNzH' }],
+        attestation,
+        unknownField: 'should be stripped',
+      } as any),
+      {
+        recipients: [{ amount: '10000', address: '2N9Ego9KidiZR8tMP82g6RaggQtcbR9zNzH' }],
+        attestation,
+      }
+    );
+    assert.ok(buildParamKeys.includes('attestation'), 'buildParamKeys must include attestation');
+  });
+
+  it('AttestationPayload codec requires all four fields', function () {
+    const valid = {
+      signature: 'sig',
+      credentialId: 'cred-id',
+      clientDataJSON: 'client-data',
+      authenticatorData: 'auth-data',
+    };
+    assert.strictEqual(AttestationPayload.is(valid), true);
+    assert.strictEqual(AttestationPayload.is({ ...valid, signature: undefined }), false);
+  });
 });
diff --git a/modules/sdk-core/test/unit/bitgo/wallet/SendTransactionRequest.ts b/modules/sdk-core/test/unit/bitgo/wallet/SendTransactionRequest.ts
index c1030ff859..12e3b09906 100644
--- a/modules/sdk-core/test/unit/bitgo/wallet/SendTransactionRequest.ts
+++ b/modules/sdk-core/test/unit/bitgo/wallet/SendTransactionRequest.ts
@@ -24,4 +24,13 @@ describe('SendTransactionRequest', function () {
       addressType: 'p2sh',
     });
   });
+
+  it('preserves attestation (WCN-539: @bitgo/public-types TxSendBody declares it natively)', function () {
+    const attestation = { signature: 'sig', credentialId: 'c', clientDataJSON: 'cd', authenticatorData: 'ad' };
+
+    assert.deepStrictEqual(TxSendBody.encode({ txHex: '00', attestation } as any), {
+      txHex: '00',
+      attestation,
+    });
+  });
 });
diff --git a/yarn.lock b/yarn.lock
index 4eabf566b6..23d7ac50a3 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -997,10 +997,10 @@
     monocle-ts "^2.3.13"
     newtype-ts "^0.3.5"
 
-"@bitgo/public-types@6.22.0":
-  version "6.22.0"
-  resolved "https://registry.npmjs.org/@bitgo/public-types/-/public-types-6.22.0.tgz#bbef2866c9b2d35e4a6179f7c400abc4f419d0ec"
-  integrity sha512-FueZVrrAKfevkoC9/TtKQLq5S19PzKfsNSj+0uHt1rEoKJ5vS1Icf/M/8pIwYVR11Kn3mjWzqbYJrJUZI/3FHQ==
+"@bitgo/public-types@6.43.0":
+  version "6.43.0"
+  resolved "https://registry.npmjs.org/@bitgo/public-types/-/public-types-6.43.0.tgz#3d749f011ae7cad1c992ccc49c7b9cc24dbc5e1a"
+  integrity sha512-aYzRp7IH/Xbyi8/CzlYDiPpJmtQN0BlJGanqupDj4YTMJ9UjwIJLaUjOtJuVTT+ZrChcgdDZgajnmPDdPV2J1w==
   dependencies:
     fp-ts "^2.0.0"
     io-ts "npm:@bitgo-forks/io-ts@2.1.4"