Pseudo-accounts to use sequence 0

src/xrpld/app/tx/detail/InvariantCheck.cpp

@@ -884,6 +884,8 @@ ValidNewAccountRoot::visitEntry(
     {
         accountsCreated_++;
         accountSeq_ = (*after)[sfSequence];
+        pseudoAccount_ =
+            after->isFieldPresent(sfAMMID) || after->isFieldPresent(sfVaultID);
     }
 }
 
@@ -912,8 +914,13 @@ ValidNewAccountRoot::finalize(
          tx.getTxnType() == ttXCHAIN_ADD_ACCOUNT_CREATE_ATTESTATION) &&
         result == tesSUCCESS)
     {
-        std::uint32_t const startingSeq{
-            view.rules().enabled(featureDeletableAccounts) ? view.seq() : 1};
+        std::uint32_t const startingSeq =  //
+            (pseudoAccount_ &&
+             view.rules().enabled(featureSingleAssetVault))   //
+            ? 0                                               //
+            : view.rules().enabled(featureDeletableAccounts)  //
+                ? view.seq()                                  //
+                : 1;
 
         if (accountSeq_ != startingSeq)
         {

src/xrpld/app/tx/detail/InvariantCheck.h

@@ -438,6 +438,7 @@ class ValidNewAccountRoot
 {
     std::uint32_t accountsCreated_ = 0;
     std::uint32_t accountSeq_ = 0;
+    bool pseudoAccount_ = false;
 
 public:
     void

src/xrpld/ledger/detail/View.cpp

@@ -1058,8 +1058,16 @@ createPseudoAccount(
     auto account = std::make_shared<SLE>(keylet::account(accountId));
     account->setAccountID(sfAccount, accountId);
     account->setFieldAmount(sfBalance, STAmount{});
-    std::uint32_t const seqno{
-        view.rules().enabled(featureDeletableAccounts) ? view.seq() : 1};
+
+    // Pseudo-accounts can't submit transactions, so set the sequence number
+    // to 0 to make them easier to spot and verify, and add an extra level
+    // of protection.
+    std::uint32_t const seqno =                           //
+        view.rules().enabled(featureSingleAssetVault)     //
+        ? 0                                               //
+        : view.rules().enabled(featureDeletableAccounts)  //
+            ? view.seq()                                  //
+            : 1;
     account->setFieldU32(sfSequence, seqno);
     // Ignore reserves requirement, disable the master key, allow default
     // rippling, and enable deposit authorization to prevent payments into