diff --git a/packages/xahau-binary-codec/src/enums/definitions.json b/packages/xahau-binary-codec/src/enums/definitions.json
index 0f8ad010..e529ab5d 100644
--- a/packages/xahau-binary-codec/src/enums/definitions.json
+++ b/packages/xahau-binary-codec/src/enums/definitions.json
@@ -329,6 +329,16 @@
         "type": "UInt16"
       }
     ],
+    [
+      "HookStateScale",
+      {
+        "nth": 21,
+        "isVLEncoded": false,
+        "isSerialized": true,
+        "isSigningField": true,
+        "type": "UInt16"
+      }
+    ],
     [
       "NetworkID",
       {
@@ -2838,6 +2848,7 @@
     "tecINSUF_RESERVE_SELLER": 187,
     "tecIMMUTABLE": 188,
     "tecTOO_MANY_REMARKS": 189,
+    "tecHAS_HOOK_STATE": 190,
     "tecLAST_POSSIBLE_ENTRY": 255
   },
   "TRANSACTION_TYPES": {
diff --git a/packages/xahau/HISTORY.md b/packages/xahau/HISTORY.md
index e39c9446..cfdb5960 100644
--- a/packages/xahau/HISTORY.md
+++ b/packages/xahau/HISTORY.md
@@ -6,6 +6,7 @@ Subscribe to [the **xrpl-announce** mailing list](https://groups.google.com/g/xr
 
 ### Added
 * Support for Cron Amendment
+* Support for ExtendedHookState Amendment
 
 ## 4.0.1 (2025-10-03)
 
diff --git a/packages/xahau/src/models/ledger/AccountRoot.ts b/packages/xahau/src/models/ledger/AccountRoot.ts
index ca743273..c7547295 100644
--- a/packages/xahau/src/models/ledger/AccountRoot.ts
+++ b/packages/xahau/src/models/ledger/AccountRoot.ts
@@ -84,6 +84,7 @@ export default interface AccountRoot extends BaseLedgerEntry, HasPreviousTxnID {
   GovernanceMarks?: string
   AccountIndex?: number
   TouchCount?: number
+  HookStateScale?: number
   /* The cron job that is associated with this account. */
   Cron?: string
 }
diff --git a/packages/xahau/src/models/transactions/accountSet.ts b/packages/xahau/src/models/transactions/accountSet.ts
index dde9b552..6c165523 100644
--- a/packages/xahau/src/models/transactions/accountSet.ts
+++ b/packages/xahau/src/models/transactions/accountSet.ts
@@ -4,6 +4,7 @@ import {
   Account,
   BaseTransaction,
   isAccount,
+  isNumber,
   validateBaseTransaction,
   validateOptionalField,
 } from './common'
@@ -163,10 +164,15 @@ export interface AccountSet extends BaseTransaction {
    * account's behalf using NFTokenMint's `Issuer` field.
    */
   NFTokenMinter?: Account
+  /**
+   * The allowed scale of the hook state.
+   */
+  HookStateScale?: number
 }
 
 const MIN_TICK_SIZE = 3
 const MAX_TICK_SIZE = 15
+const MAX_HOOK_STATE_SCALE = 16
 
 /**
  * Verify the form and type of an AccountSet at runtime.
@@ -174,7 +180,7 @@ const MAX_TICK_SIZE = 15
  * @param tx - An AccountSet Transaction.
  * @throws When the AccountSet is Malformed.
  */
-// eslint-disable-next-line max-lines-per-function -- okay for this method, only a little over
+// eslint-disable-next-line max-lines-per-function, max-statements -- okay for this method, only a little over
 export function validateAccountSet(tx: Record<string, unknown>): void {
   validateBaseTransaction(tx)
 
@@ -225,4 +231,14 @@ export function validateAccountSet(tx: Record<string, unknown>): void {
       throw new ValidationError('AccountSet: invalid TickSize')
     }
   }
+
+  validateOptionalField(tx, 'HookStateScale', isNumber)
+  if (
+    typeof tx.HookStateScale === 'number' &&
+    tx.HookStateScale > MAX_HOOK_STATE_SCALE
+  ) {
+    throw new ValidationError(
+      `AccountSet: HookStateScale must be less than ${MAX_HOOK_STATE_SCALE}`,
+    )
+  }
 }
diff --git a/packages/xahau/test/models/accountSet.test.ts b/packages/xahau/test/models/accountSet.test.ts
index b3ce24ea..947615d4 100644
--- a/packages/xahau/test/models/accountSet.test.ts
+++ b/packages/xahau/test/models/accountSet.test.ts
@@ -163,4 +163,31 @@ describe('AccountSet', function () {
       'AccountSet: invalid field NFTokenMinter',
     )
   })
+
+  it(`throws w/ invalid HookStateScale`, function () {
+    account.HookStateScale = ''
+
+    assert.throws(
+      () => validateAccountSet(account),
+      ValidationError,
+      'AccountSet: invalid field HookStateScale',
+    )
+    assert.throws(
+      () => validate(account),
+      ValidationError,
+      'AccountSet: invalid field HookStateScale',
+    )
+
+    account.HookStateScale = 17
+    assert.throws(
+      () => validateAccountSet(account),
+      ValidationError,
+      'AccountSet: HookStateScale must be less than 16',
+    )
+    assert.throws(
+      () => validate(account),
+      ValidationError,
+      'AccountSet: HookStateScale must be less than 16',
+    )
+  })
 })