refactor: Make CWalletTx sync state type-safe

Current CWalletTx state representation makes it possible to set
inconsistent states that won't be handled correctly by wallet sync code
or serialized & deserialized back into the same form.

For example, it is possible to call setConflicted without setting a
conflicting block hash, or setConfirmed with no transaction index. And
it's possible update individual m_confirm and fInMempool data fields
without setting an overall consistent state that can be serialized and
handled correctly.

Fix this without changing behavior by using std::variant, instead of an
enum and collection of fields, to represent sync state, so state
tracking code is safer and more legible.

This is a first step to fixing state tracking bugs
https://github.com/bitcoin-core/bitcoin-devwiki/wiki/Wallet-Transaction-Conflict-Tracking,
by adding an extra margin of safety that can prevent new bugs from being
introduced as existing bugs are fixed.

16 files changed, 257 insertions, 174 deletions

diff --git a/src/Makefile.am b/src/Makefile.am
index 85450149cf..59043c6dd0 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -246,6 +246,7 @@ BITCOIN_CORE_H = \
   util/macros.h \
   util/message.h \
   util/moneystr.h \
+  util/overloaded.h \
   util/rbf.h \
   util/readwritefile.h \
   util/serfloat.h \
diff --git a/src/Makefile.test.include b/src/Makefile.test.include
index da4b85665f..f5d5f07c25 100644
--- a/src/Makefile.test.include
+++ b/src/Makefile.test.include
@@ -159,6 +159,7 @@ BITCOIN_TESTS += \
   wallet/test/wallet_tests.cpp \
   wallet/test/walletdb_tests.cpp \
   wallet/test/wallet_crypto_tests.cpp \
+  wallet/test/wallet_transaction_tests.cpp \
   wallet/test/coinselector_tests.cpp \
   wallet/test/init_tests.cpp \
   wallet/test/ismine_tests.cpp \
diff --git a/src/bench/coin_selection.cpp b/src/bench/coin_selection.cpp
index f6a8c56743..3c24fee60f 100644
--- a/src/bench/coin_selection.cpp
+++ b/src/bench/coin_selection.cpp
@@ -18,7 +18,7 @@ static void addCoin(const CAmount& nValue, const CWallet& wallet, std::vector<st
     tx.nLockTime = nextLockTime++; // so all transactions get different hashes
     tx.vout.resize(1);
     tx.vout[0].nValue = nValue;
-    wtxs.push_back(std::make_unique<CWalletTx>(MakeTransactionRef(std::move(tx))));
+    wtxs.push_back(std::make_unique<CWalletTx>(MakeTransactionRef(std::move(tx)), TxStateInactive{}));
 }
 
 // Simple benchmark for wallet coin selection. Note that it maybe be necessary
diff --git a/src/util/overloaded.h b/src/util/overloaded.h
new file mode 100644
index 0000000000..6be7453f81
--- /dev/null
+++ b/src/util/overloaded.h
@@ -0,0 +1,22 @@
+// Copyright (c) 2021 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#ifndef BITCOIN_UTIL_OVERLOADED_H
+#define BITCOIN_UTIL_OVERLOADED_H
+
+namespace util {
+//! Overloaded helper for std::visit. This helper and std::visit in general are
+//! useful to write code that switches on a variant type. Unlike if/else-if and
+//! switch/case statements, std::visit will trigger compile errors if there are
+//! unhandled cases.
+//!
+//! Implementation comes from and example usage can be found at
+//! https://en.cppreference.com/w/cpp/utility/variant/visit#Example
+template<class... Ts> struct Overloaded : Ts... { using Ts::operator()...; };
+
+//! Explicit deduction guide (not needed as of C++20)
+template<class... Ts> Overloaded(Ts...) -> Overloaded<Ts...>;
+} // namespace util
+
+#endif // BITCOIN_UTIL_OVERLOADED_H
diff --git a/src/wallet/interfaces.cpp b/src/wallet/interfaces.cpp
index 57f1a6a67a..6489e2a5fc 100644
--- a/src/wallet/interfaces.cpp
+++ b/src/wallet/interfaces.cpp
@@ -82,7 +82,10 @@ WalletTx MakeWalletTx(CWallet& wallet, const CWalletTx& wtx)
 WalletTxStatus MakeWalletTxStatus(const CWallet& wallet, const CWalletTx& wtx)
 {
     WalletTxStatus result;
-    result.block_height = wtx.m_confirm.block_height > 0 ? wtx.m_confirm.block_height : std::numeric_limits<int>::max();
+    result.block_height =
+        wtx.state<TxStateConfirmed>() ? wtx.state<TxStateConfirmed>()->confirmed_block_height :
+        wtx.state<TxStateConflicted>() ? wtx.state<TxStateConflicted>()->conflicting_block_height :
+        std::numeric_limits<int>::max();
     result.blocks_to_maturity = wallet.GetTxBlocksToMaturity(wtx);
     result.depth_in_main_chain = wallet.GetTxDepthInMainChain(wtx);
     result.time_received = wtx.nTimeReceived;
diff --git a/src/wallet/rpcdump.cpp b/src/wallet/rpcdump.cpp
index 403c978680..ef276d4a04 100644
--- a/src/wallet/rpcdump.cpp
+++ b/src/wallet/rpcdump.cpp
@@ -369,11 +369,9 @@ RPCHelpMan importprunedfunds()
 
     unsigned int txnIndex = vIndex[it - vMatch.begin()];
 
-    CWalletTx::Confirmation confirm(CWalletTx::Status::CONFIRMED, height, merkleBlock.header.GetHash(), txnIndex);
-
     CTransactionRef tx_ref = MakeTransactionRef(tx);
     if (pwallet->IsMine(*tx_ref)) {
-        pwallet->AddToWallet(std::move(tx_ref), confirm);
+        pwallet->AddToWallet(std::move(tx_ref), TxStateConfirmed{merkleBlock.header.GetHash(), height, static_cast<int>(txnIndex)});
         return NullUniValue;
     }
 
diff --git a/src/wallet/rpcwallet.cpp b/src/wallet/rpcwallet.cpp
index babb61b03a..4d63f99999 100644
--- a/src/wallet/rpcwallet.cpp
+++ b/src/wallet/rpcwallet.cpp
@@ -166,13 +166,13 @@ static void WalletTxToJSON(const CWallet& wallet, const CWalletTx& wtx, UniValue
     entry.pushKV("confirmations", confirms);
     if (wtx.IsCoinBase())
         entry.pushKV("generated", true);
-    if (confirms > 0)
+    if (auto* conf = wtx.state<TxStateConfirmed>())
     {
-        entry.pushKV("blockhash", wtx.m_confirm.hashBlock.GetHex());
-        entry.pushKV("blockheight", wtx.m_confirm.block_height);
-        entry.pushKV("blockindex", wtx.m_confirm.nIndex);
+        entry.pushKV("blockhash", conf->confirmed_block_hash.GetHex());
+        entry.pushKV("blockheight", conf->confirmed_block_height);
+        entry.pushKV("blockindex", conf->position_in_block);
         int64_t block_time;
-        CHECK_NONFATAL(chain.findBlock(wtx.m_confirm.hashBlock, FoundBlock().time(block_time)));
+        CHECK_NONFATAL(chain.findBlock(conf->confirmed_block_hash, FoundBlock().time(block_time)));
         entry.pushKV("blocktime", block_time);
     } else {
         entry.pushKV("trusted", CachedTxIsTrusted(wallet, wtx));
diff --git a/src/wallet/test/coinselector_tests.cpp b/src/wallet/test/coinselector_tests.cpp
index a8a7e12a32..8f985f31ee 100644
--- a/src/wallet/test/coinselector_tests.cpp
+++ b/src/wallet/test/coinselector_tests.cpp
@@ -74,7 +74,7 @@ static void add_coin(std::vector<COutput>& coins, CWallet& wallet, const CAmount
     uint256 txid = tx.GetHash();
 
     LOCK(wallet.cs_wallet);
-    auto ret = wallet.mapWallet.emplace(std::piecewise_construct, std::forward_as_tuple(txid), std::forward_as_tuple(MakeTransactionRef(std::move(tx))));
+    auto ret = wallet.mapWallet.emplace(std::piecewise_construct, std::forward_as_tuple(txid), std::forward_as_tuple(MakeTransactionRef(std::move(tx)), TxStateInactive{}));
     assert(ret.second);
     CWalletTx& wtx = (*ret.first).second;
     if (fIsFromMe)
diff --git a/src/wallet/test/psbt_wallet_tests.cpp b/src/wallet/test/psbt_wallet_tests.cpp
index dd24fa2c19..7bc2bb5583 100644
--- a/src/wallet/test/psbt_wallet_tests.cpp
+++ b/src/wallet/test/psbt_wallet_tests.cpp
@@ -34,12 +34,12 @@ BOOST_AUTO_TEST_CASE(psbt_updater_test)
     CDataStream s_prev_tx1(ParseHex("0200000000010158e87a21b56daf0c23be8e7070456c336f7cbaa5c8757924f545887bb2abdd7501000000171600145f275f436b09a8cc9a2eb2a2f528485c68a56323feffffff02d8231f1b0100000017a914aed962d6654f9a2b36608eb9d64d2b260db4f1118700c2eb0b0000000017a914b7f5faf40e3d40a5a459b1db3535f2b72fa921e88702483045022100a22edcc6e5bc511af4cc4ae0de0fcd75c7e04d8c1c3a8aa9d820ed4b967384ec02200642963597b9b1bc22c75e9f3e117284a962188bf5e8a74c895089046a20ad770121035509a48eb623e10aace8bfd0212fdb8a8e5af3c94b0b133b95e114cab89e4f7965000000"), SER_NETWORK, PROTOCOL_VERSION);
     CTransactionRef prev_tx1;
     s_prev_tx1 >> prev_tx1;
-    m_wallet.mapWallet.emplace(std::piecewise_construct, std::forward_as_tuple(prev_tx1->GetHash()), std::forward_as_tuple(prev_tx1));
+    m_wallet.mapWallet.emplace(std::piecewise_construct, std::forward_as_tuple(prev_tx1->GetHash()), std::forward_as_tuple(prev_tx1, TxStateInactive{}));
 
     CDataStream s_prev_tx2(ParseHex("0200000001aad73931018bd25f84ae400b68848be09db706eac2ac18298babee71ab656f8b0000000048473044022058f6fc7c6a33e1b31548d481c826c015bd30135aad42cd67790dab66d2ad243b02204a1ced2604c6735b6393e5b41691dd78b00f0c5942fb9f751856faa938157dba01feffffff0280f0fa020000000017a9140fb9463421696b82c833af241c78c17ddbde493487d0f20a270100000017a91429ca74f8a08f81999428185c97b5d852e4063f618765000000"), SER_NETWORK, PROTOCOL_VERSION);
     CTransactionRef prev_tx2;
     s_prev_tx2 >> prev_tx2;
-    m_wallet.mapWallet.emplace(std::piecewise_construct, std::forward_as_tuple(prev_tx2->GetHash()), std::forward_as_tuple(prev_tx2));
+    m_wallet.mapWallet.emplace(std::piecewise_construct, std::forward_as_tuple(prev_tx2->GetHash()), std::forward_as_tuple(prev_tx2, TxStateInactive{}));
 
     // Import descriptors for keys and scripts
     import_descriptor(m_wallet, "sh(multi(2,xprv9s21ZrQH143K2LE7W4Xf3jATf9jECxSb7wj91ZnmY4qEJrS66Qru9RFqq8xbkgT32ya6HqYJweFdJUEDf5Q6JFV7jMiUws7kQfe6Tv4RbfN/0h/0h/0h,xprv9s21ZrQH143K2LE7W4Xf3jATf9jECxSb7wj91ZnmY4qEJrS66Qru9RFqq8xbkgT32ya6HqYJweFdJUEDf5Q6JFV7jMiUws7kQfe6Tv4RbfN/0h/0h/1h))");
diff --git a/src/wallet/test/wallet_tests.cpp b/src/wallet/test/wallet_tests.cpp
index 4499eb5903..9a1398e970 100644
--- a/src/wallet/test/wallet_tests.cpp
+++ b/src/wallet/test/wallet_tests.cpp
@@ -330,7 +330,7 @@ BOOST_FIXTURE_TEST_CASE(importwallet_rescan, TestChain100Setup)
 BOOST_FIXTURE_TEST_CASE(coin_mark_dirty_immature_credit, TestChain100Setup)
 {
     CWallet wallet(m_node.chain.get(), "", m_args, CreateDummyWalletDatabase());
-    CWalletTx wtx(m_coinbase_txns.back());
+    CWalletTx wtx{m_coinbase_txns.back(), TxStateConfirmed{m_node.chainman->ActiveChain().Tip()->GetBlockHash(), m_node.chainman->ActiveChain().Height(), /*position_in_block=*/0}};
 
     LOCK(wallet.cs_wallet);
     wallet.SetWalletFlag(WALLET_FLAG_DESCRIPTORS);
@@ -338,9 +338,6 @@ BOOST_FIXTURE_TEST_CASE(coin_mark_dirty_immature_credit, TestChain100Setup)
 
     wallet.SetLastBlockProcessed(m_node.chainman->ActiveChain().Height(), m_node.chainman->ActiveChain().Tip()->GetBlockHash());
 
-    CWalletTx::Confirmation confirm(CWalletTx::Status::CONFIRMED, m_node.chainman->ActiveChain().Height(), m_node.chainman->ActiveChain().Tip()->GetBlockHash(), 0);
-    wtx.m_confirm = confirm;
-
     // Call GetImmatureCredit() once before adding the key to the wallet to
     // cache the current immature credit amount, which is 0.
     BOOST_CHECK_EQUAL(CachedTxGetImmatureCredit(wallet, wtx), 0);
@@ -355,7 +352,7 @@ BOOST_FIXTURE_TEST_CASE(coin_mark_dirty_immature_credit, TestChain100Setup)
 static int64_t AddTx(ChainstateManager& chainman, CWallet& wallet, uint32_t lockTime, int64_t mockTime, int64_t blockTime)
 {
     CMutableTransaction tx;
-    CWalletTx::Confirmation confirm;
+    TxState state = TxStateInactive{};
     tx.nLockTime = lockTime;
     SetMockTime(mockTime);
     CBlockIndex* block = nullptr;
@@ -367,13 +364,13 @@ static int64_t AddTx(ChainstateManager& chainman, CWallet& wallet, uint32_t lock
         block = inserted.first->second;
         block->nTime = blockTime;
         block->phashBlock = &hash;
-        confirm = {CWalletTx::Status::CONFIRMED, block->nHeight, hash, 0};
+        state = TxStateConfirmed{hash, block->nHeight, /*position_in_block=*/0};
     }
-
-    // If transaction is already in map, to avoid inconsistencies, unconfirmation
-    // is needed before confirm again with different block.
-    return wallet.AddToWallet(MakeTransactionRef(tx), confirm, [&](CWalletTx& wtx, bool /* new_tx */) {
-        wtx.setUnconfirmed();
+    return wallet.AddToWallet(MakeTransactionRef(tx), state, [&](CWalletTx& wtx, bool /* new_tx */) {
+        // Assign wtx.m_state to simplify test and avoid the need to simulate
+        // reorg events. Without this, AddToWallet asserts false when the same
+        // transaction is confirmed in different blocks.
+        wtx.m_state = state;
         return true;
     })->nTimeSmart;
 }
@@ -534,8 +531,7 @@ public:
         wallet->SetLastBlockProcessed(wallet->GetLastBlockHeight() + 1, m_node.chainman->ActiveChain().Tip()->GetBlockHash());
         auto it = wallet->mapWallet.find(tx->GetHash());
         BOOST_CHECK(it != wallet->mapWallet.end());
-        CWalletTx::Confirmation confirm(CWalletTx::Status::CONFIRMED, m_node.chainman->ActiveChain().Height(), m_node.chainman->ActiveChain().Tip()->GetBlockHash(), 1);
-        it->second.m_confirm = confirm;
+        it->second.m_state = TxStateConfirmed{m_node.chainman->ActiveChain().Tip()->GetBlockHash(), m_node.chainman->ActiveChain().Height(), /*position_in_block=*/1};
         return it->second;
     }
 
diff --git a/src/wallet/test/wallet_transaction_tests.cpp b/src/wallet/test/wallet_transaction_tests.cpp
new file mode 100644
index 0000000000..5ef2904f66
--- /dev/null
+++ b/src/wallet/test/wallet_transaction_tests.cpp
@@ -0,0 +1,24 @@
+// Copyright (c) 2021 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#include <wallet/transaction.h>
+
+#include <wallet/test/wallet_test_fixture.h>
+
+#include <boost/test/unit_test.hpp>
+
+BOOST_FIXTURE_TEST_SUITE(wallet_transaction_tests, WalletTestingSetup)
+
+BOOST_AUTO_TEST_CASE(roundtrip)
+{
+    for (uint8_t hash = 0; hash < 5; ++hash) {
+        for (int index = -2; index < 3; ++index) {
+            TxState state = TxStateInterpretSerialized(TxStateUnrecognized{uint256{hash}, index});
+            BOOST_CHECK_EQUAL(TxStateSerializedBlockHash(state), uint256{hash});
+            BOOST_CHECK_EQUAL(TxStateSerializedIndex(state), index);
+        }
+    }
+}
+
+BOOST_AUTO_TEST_SUITE_END()
diff --git a/src/wallet/transaction.cpp b/src/wallet/transaction.cpp
index cf98b516f1..a926c0ecc1 100644
--- a/src/wallet/transaction.cpp
+++ b/src/wallet/transaction.cpp
@@ -15,7 +15,7 @@ bool CWalletTx::IsEquivalentTo(const CWalletTx& _tx) const
 
 bool CWalletTx::InMempool() const
 {
-    return fInMempool;
+    return state<TxStateInMempool>();
 }
 
 int64_t CWalletTx::GetTxTime() const
diff --git a/src/wallet/transaction.h b/src/wallet/transaction.h
index 1ccef31056..52d72cccf3 100644
--- a/src/wallet/transaction.h
+++ b/src/wallet/transaction.h
@@ -11,12 +11,102 @@
 #include <wallet/ismine.h>
 #include <threadsafety.h>
 #include <tinyformat.h>
+#include <util/overloaded.h>
 #include <util/strencodings.h>
 #include <util/string.h>
 
 #include <list>
+#include <variant>
 #include <vector>
 
+//! State of transaction confirmed in a block.
+struct TxStateConfirmed {
+    uint256 confirmed_block_hash;
+    int confirmed_block_height;
+    int position_in_block;
+
+    explicit TxStateConfirmed(const uint256& block_hash, int height, int index) : confirmed_block_hash(block_hash), confirmed_block_height(height), position_in_block(index) {}
+};
+
+//! State of transaction added to mempool.
+struct TxStateInMempool {
+};
+
+//! State of rejected transaction that conflicts with a confirmed block.
+struct TxStateConflicted {
+    uint256 conflicting_block_hash;
+    int conflicting_block_height;
+
+    explicit TxStateConflicted(const uint256& block_hash, int height) : conflicting_block_hash(block_hash), conflicting_block_height(height) {}
+};
+
+//! State of transaction not confirmed or conflicting with a known block and
+//! not in the mempool. May conflict with the mempool, or with an unknown block,
+//! or be abandoned, never broadcast, or rejected from the mempool for another
+//! reason.
+struct TxStateInactive {
+    bool abandoned;
+
+    explicit TxStateInactive(bool abandoned = false) : abandoned(abandoned) {}
+};
+
+//! State of transaction loaded in an unrecognized state with unexpected hash or
+//! index values. Treated as inactive (with serialized hash and index values
+//! preserved) by default, but may enter another state if transaction is added
+//! to the mempool, or confirmed, or abandoned, or found conflicting.
+struct TxStateUnrecognized {
+    uint256 block_hash;
+    int index;
+
+    TxStateUnrecognized(const uint256& block_hash, int index) : block_hash(block_hash), index(index) {}
+};
+
+//! All possible CWalletTx states
+using TxState = std::variant<TxStateConfirmed, TxStateInMempool, TxStateConflicted, TxStateInactive, TxStateUnrecognized>;
+
+//! Subset of states transaction sync logic is implemented to handle.
+using SyncTxState = std::variant<TxStateConfirmed, TxStateInMempool, TxStateInactive>;
+
+//! Try to interpret deserialized TxStateUnrecognized data as a recognized state.
+static inline TxState TxStateInterpretSerialized(TxStateUnrecognized data)
+{
+    if (data.block_hash == uint256::ZERO) {
+        if (data.index == 0) return TxStateInactive{};
+    } else if (data.block_hash == uint256::ONE) {
+        if (data.index == -1) return TxStateInactive{/*abandoned=*/true};
+    } else if (data.index >= 0) {
+        return TxStateConfirmed{data.block_hash, /*height=*/-1, data.index};
+    } else if (data.index == -1) {
+        return TxStateConflicted{data.block_hash, /*height=*/-1};
+    }
+    return data;
+}
+
+//! Get TxState serialized block hash. Inverse of TxStateInterpretSerialized.
+static inline uint256 TxStateSerializedBlockHash(const TxState& state)
+{
+    return std::visit(util::Overloaded{
+        [](const TxStateInactive& inactive) { return inactive.abandoned ? uint256::ONE : uint256::ZERO; },
+        [](const TxStateInMempool& in_mempool) { return uint256::ZERO; },
+        [](const TxStateConfirmed& confirmed) { return confirmed.confirmed_block_hash; },
+        [](const TxStateConflicted& conflicted) { return conflicted.conflicting_block_hash; },
+        [](const TxStateUnrecognized& unrecognized) { return unrecognized.block_hash; }
+    }, state);
+}
+
+//! Get TxState serialized block index. Inverse of TxStateInterpretSerialized.
+static inline int TxStateSerializedIndex(const TxState& state)
+{
+    return std::visit(util::Overloaded{
+        [](const TxStateInactive& inactive) { return inactive.abandoned ? -1 : 0; },
+        [](const TxStateInMempool& in_mempool) { return 0; },
+        [](const TxStateConfirmed& confirmed) { return confirmed.position_in_block; },
+        [](const TxStateConflicted& conflicted) { return -1; },
+        [](const TxStateUnrecognized& unrecognized) { return unrecognized.index; }
+    }, state);
+}
+
+
 typedef std::map<std::string, std::string> mapValue_t;
 
 /** Legacy class used for deserializing vtxPrev for backwards compatibility.
@@ -45,12 +135,6 @@ public:
  */
 class CWalletTx
 {
-private:
-    /** Constant used in hashBlock to indicate tx has been abandoned, only used at
-     * serialization/deserialization to avoid ambiguity with conflicted.
-     */
-    static constexpr const uint256& ABANDON_HASH = uint256::ONE;
-
 public:
     /**
      * Key/value map with information about the transaction.
@@ -111,11 +195,9 @@ public:
      */
     mutable bool m_is_cache_empty{true};
     mutable bool fChangeCached;
-    mutable bool fInMempool;
     mutable CAmount nChangeCached;
 
-    CWalletTx(CTransactionRef arg)
-        : tx(std::move(arg))
+    CWalletTx(CTransactionRef tx, const TxState& state) : tx(std::move(tx)), m_state(state)
     {
         Init();
     }
@@ -129,44 +211,12 @@ public:
         nTimeSmart = 0;
         fFromMe = false;
         fChangeCached = false;
-        fInMempool = false;
         nChangeCached = 0;
         nOrderPos = -1;
-        m_confirm = Confirmation{};
     }
 
     CTransactionRef tx;
-
-    /** New transactions start as UNCONFIRMED. At BlockConnected,
-     * they will transition to CONFIRMED. In case of reorg, at BlockDisconnected,
-     * they roll back to UNCONFIRMED. If we detect a conflicting transaction at
-     * block connection, we update conflicted tx and its dependencies as CONFLICTED.
-     * If tx isn't confirmed and outside of mempool, the user may switch it to ABANDONED
-     * by using the abandontransaction call. This last status may be override by a CONFLICTED
-     * or CONFIRMED transition.
-     */
-    enum Status {
-        UNCONFIRMED,
-        CONFIRMED,
-        CONFLICTED,
-        ABANDONED
-    };
-
-    /** Confirmation includes tx status and a triplet of {block height/block hash/tx index in block}
-     * at which tx has been confirmed. All three are set to 0 if tx is unconfirmed or abandoned.
-     * Meaning of these fields changes with CONFLICTED state where they instead point to block hash
-     * and block height of the deepest conflicting tx.
-     */
-    struct Confirmation {
-        Status status;
-        int block_height;
-        uint256 hashBlock;
-        int nIndex;
-        Confirmation(Status status = UNCONFIRMED, int block_height = 0, uint256 block_hash = uint256(), int block_index = 0)
-            : status{status}, block_height{block_height}, hashBlock{block_hash}, nIndex{block_index} {}
-    };
-
-    Confirmation m_confirm;
+    TxState m_state;
 
     template<typename Stream>
     void Serialize(Stream& s) const
@@ -184,8 +234,8 @@ public:
         std::vector<uint8_t> dummy_vector1; //!< Used to be vMerkleBranch
         std::vector<uint8_t> dummy_vector2; //!< Used to be vtxPrev
         bool dummy_bool = false; //!< Used to be fSpent
-        uint256 serializedHash = isAbandoned() ? ABANDON_HASH : m_confirm.hashBlock;
-        int serializedIndex = isAbandoned() || isConflicted() ? -1 : m_confirm.nIndex;
+        uint256 serializedHash = TxStateSerializedBlockHash(m_state);
+        int serializedIndex = TxStateSerializedIndex(m_state);
         s << tx << serializedHash << dummy_vector1 << serializedIndex << dummy_vector2 << mapValueCopy << vOrderForm << fTimeReceivedIsTxTime << nTimeReceived << fFromMe << dummy_bool;
     }
 
@@ -197,24 +247,11 @@ public:
         std::vector<uint256> dummy_vector1; //!< Used to be vMerkleBranch
         std::vector<CMerkleTx> dummy_vector2; //!< Used to be vtxPrev
         bool dummy_bool; //! Used to be fSpent
+        uint256 serialized_block_hash;
         int serializedIndex;
-        s >> tx >> m_confirm.hashBlock >> dummy_vector1 >> serializedIndex >> dummy_vector2 >> mapValue >> vOrderForm >> fTimeReceivedIsTxTime >> nTimeReceived >> fFromMe >> dummy_bool;
-
-        /* At serialization/deserialization, an nIndex == -1 means that hashBlock refers to
-         * the earliest block in the chain we know this or any in-wallet ancestor conflicts
-         * with. If nIndex == -1 and hashBlock is ABANDON_HASH, it means transaction is abandoned.
-         * In same context, an nIndex >= 0 refers to a confirmed transaction (if hashBlock set) or
-         * unconfirmed one. Older clients interpret nIndex == -1 as unconfirmed for backward
-         * compatibility (pre-commit 9ac63d6).
-         */
-        if (serializedIndex == -1 && m_confirm.hashBlock == ABANDON_HASH) {
-            setAbandoned();
-        } else if (serializedIndex == -1) {
-            setConflicted();
-        } else if (!m_confirm.hashBlock.IsNull()) {
-            m_confirm.nIndex = serializedIndex;
-            setConfirmed();
-        }
+        s >> tx >> serialized_block_hash >> dummy_vector1 >> serializedIndex >> dummy_vector2 >> mapValue >> vOrderForm >> fTimeReceivedIsTxTime >> nTimeReceived >> fFromMe >> dummy_bool;
+
+        m_state = TxStateInterpretSerialized({serialized_block_hash, serializedIndex});
 
         const auto it_op = mapValue.find("n");
         nOrderPos = (it_op != mapValue.end()) ? LocaleIndependentAtoi<int64_t>(it_op->second) : -1;
@@ -250,20 +287,13 @@ public:
 
     int64_t GetTxTime() const;
 
-    bool isAbandoned() const { return m_confirm.status == CWalletTx::ABANDONED; }
-    void setAbandoned()
-    {
-        m_confirm.status = CWalletTx::ABANDONED;
-        m_confirm.hashBlock = uint256();
-        m_confirm.block_height = 0;
-        m_confirm.nIndex = 0;
-    }
-    bool isConflicted() const { return m_confirm.status == CWalletTx::CONFLICTED; }
-    void setConflicted() { m_confirm.status = CWalletTx::CONFLICTED; }
-    bool isUnconfirmed() const { return m_confirm.status == CWalletTx::UNCONFIRMED; }
-    void setUnconfirmed() { m_confirm.status = CWalletTx::UNCONFIRMED; }
-    bool isConfirmed() const { return m_confirm.status == CWalletTx::CONFIRMED; }
-    void setConfirmed() { m_confirm.status = CWalletTx::CONFIRMED; }
+    template<typename T> const T* state() const { return std::get_if<T>(&m_state); }
+    template<typename T> T* state() { return std::get_if<T>(&m_state); }
+
+    bool isAbandoned() const { return state<TxStateInactive>() && state<TxStateInactive>()->abandoned; }
+    bool isConflicted() const { return state<TxStateConflicted>(); }
+    bool isUnconfirmed() const { return !isAbandoned() && !isConflicted() && !isConfirmed(); }
+    bool isConfirmed() const { return state<TxStateConfirmed>(); }
     const uint256& GetHash() const { return tx->GetHash(); }
     bool IsCoinBase() const { return tx->IsCoinBase(); }
 
diff --git a/src/wallet/wallet.cpp b/src/wallet/wallet.cpp
index 7f60dd6906..5b8a174fcb 100644
--- a/src/wallet/wallet.cpp
+++ b/src/wallet/wallet.cpp
@@ -99,7 +99,11 @@ static void UpdateWalletSetting(interfaces::Chain& chain,
  */
 static void RefreshMempoolStatus(CWalletTx& tx, interfaces::Chain& chain)
 {
-    tx.fInMempool = chain.isInMempool(tx.GetHash());
+    if (chain.isInMempool(tx.GetHash())) {
+        tx.m_state = TxStateInMempool();
+    } else if (tx.state<TxStateInMempool>()) {
+        tx.m_state = TxStateInactive();
+    }
 }
 
 bool AddWallet(WalletContext& context, const std::shared_ptr<CWallet>& wallet)
@@ -885,7 +889,7 @@ bool CWallet::IsSpentKey(const uint256& hash, unsigned int n) const
     return false;
 }
 
-CWalletTx* CWallet::AddToWallet(CTransactionRef tx, const CWalletTx::Confirmation& confirm, const UpdateWalletTxFn& update_wtx, bool fFlushOnClose, bool rescanning_old_block)
+CWalletTx* CWallet::AddToWallet(CTransactionRef tx, const TxState& state, const UpdateWalletTxFn& update_wtx, bool fFlushOnClose, bool rescanning_old_block)
 {
     LOCK(cs_wallet);
 
@@ -906,12 +910,11 @@ CWalletTx* CWallet::AddToWallet(CTransactionRef tx, const CWalletTx::Confirmatio
     }
 
     // Inserts only if not already there, returns tx inserted or tx found
-    auto ret = mapWallet.emplace(std::piecewise_construct, std::forward_as_tuple(hash), std::forward_as_tuple(tx));
+    auto ret = mapWallet.emplace(std::piecewise_construct, std::forward_as_tuple(hash), std::forward_as_tuple(tx, state));
     CWalletTx& wtx = (*ret.first).second;
     bool fInsertedNew = ret.second;
     bool fUpdated = update_wtx && update_wtx(wtx, fInsertedNew);
     if (fInsertedNew) {
-        wtx.m_confirm = confirm;
         wtx.nTimeReceived = chain().getAdjustedTime();
         wtx.nOrderPos = IncOrderPosNext(&batch);
         wtx.m_it_wtxOrdered = wtxOrdered.insert(std::make_pair(wtx.nOrderPos, &wtx));
@@ -921,16 +924,12 @@ CWalletTx* CWallet::AddToWallet(CTransactionRef tx, const CWalletTx::Confirmatio
 
     if (!fInsertedNew)
     {
-        if (confirm.status != wtx.m_confirm.status) {
-            wtx.m_confirm.status = confirm.status;
-            wtx.m_confirm.nIndex = confirm.nIndex;
-            wtx.m_confirm.hashBlock = confirm.hashBlock;
-            wtx.m_confirm.block_height = confirm.block_height;
+        if (state.index() != wtx.m_state.index()) {
+            wtx.m_state = state;
             fUpdated = true;
         } else {
-            assert(wtx.m_confirm.nIndex == confirm.nIndex);
-            assert(wtx.m_confirm.hashBlock == confirm.hashBlock);
-            assert(wtx.m_confirm.block_height == confirm.block_height);
+            assert(TxStateSerializedIndex(wtx.m_state) == TxStateSerializedIndex(state));
+            assert(TxStateSerializedBlockHash(wtx.m_state) == TxStateSerializedBlockHash(state));
         }
         // If we have a witness-stripped version of this transaction, and we
         // see a new version with a witness, then we must be upgrading a pre-segwit
@@ -964,10 +963,10 @@ CWalletTx* CWallet::AddToWallet(CTransactionRef tx, const CWalletTx::Confirmatio
     if (!strCmd.empty())
     {
         boost::replace_all(strCmd, "%s", hash.GetHex());
-        if (confirm.status == CWalletTx::Status::CONFIRMED)
+        if (auto* conf = wtx.state<TxStateConfirmed>())
         {
-            boost::replace_all(strCmd, "%b", confirm.hashBlock.GetHex());
-            boost::replace_all(strCmd, "%h", ToString(confirm.block_height));
+            boost::replace_all(strCmd, "%b", conf->confirmed_block_hash.GetHex());
+            boost::replace_all(strCmd, "%h", ToString(conf->confirmed_block_height));
         } else {
             boost::replace_all(strCmd, "%b", "unconfirmed");
             boost::replace_all(strCmd, "%h", "-1");
@@ -990,7 +989,7 @@ CWalletTx* CWallet::AddToWallet(CTransactionRef tx, const CWalletTx::Confirmatio
 
 bool CWallet::LoadToWallet(const uint256& hash, const UpdateWalletTxFn& fill_wtx)
 {
-    const auto& ins = mapWallet.emplace(std::piecewise_construct, std::forward_as_tuple(hash), std::forward_as_tuple(nullptr));
+    const auto& ins = mapWallet.emplace(std::piecewise_construct, std::forward_as_tuple(hash), std::forward_as_tuple(nullptr, TxStateInactive{}));
     CWalletTx& wtx = ins.first->second;
     if (!fill_wtx(wtx, ins.second)) {
         return false;
@@ -998,22 +997,21 @@ bool CWallet::LoadToWallet(const uint256& hash, const UpdateWalletTxFn& fill_wtx
     // If wallet doesn't have a chain (e.g wallet-tool), don't bother to update txn.
     if (HaveChain()) {
         bool active;
-        int height;
-        if (chain().findBlock(wtx.m_confirm.hashBlock, FoundBlock().inActiveChain(active).height(height)) && active) {
-            // Update cached block height variable since it not stored in the
-            // serialized transaction.
-            wtx.m_confirm.block_height = height;
-        } else if (wtx.isConflicted() || wtx.isConfirmed()) {
+        auto lookup_block = [&](const uint256& hash, int& height, TxState& state) {
             // If tx block (or conflicting block) was reorged out of chain
             // while the wallet was shutdown, change tx status to UNCONFIRMED
             // and reset block height, hash, and index. ABANDONED tx don't have
             // associated blocks and don't need to be updated. The case where a
             // transaction was reorged out while online and then reconfirmed
             // while offline is covered by the rescan logic.
-            wtx.setUnconfirmed();
-            wtx.m_confirm.hashBlock = uint256();
-            wtx.m_confirm.block_height = 0;
-            wtx.m_confirm.nIndex = 0;
+            if (!chain().findBlock(hash, FoundBlock().inActiveChain(active).height(height)) || !active) {
+                state = TxStateInactive{};
+            }
+        };
+        if (auto* conf = wtx.state<TxStateConfirmed>()) {
+            lookup_block(conf->confirmed_block_hash, conf->confirmed_block_height, wtx.m_state);
+        } else if (auto* conf = wtx.state<TxStateConflicted>()) {
+            lookup_block(conf->conflicting_block_hash, conf->conflicting_block_height, wtx.m_state);
         }
     }
     if (/* insertion took place */ ins.second) {
@@ -1024,27 +1022,27 @@ bool CWallet::LoadToWallet(const uint256& hash, const UpdateWalletTxFn& fill_wtx
         auto it = mapWallet.find(txin.prevout.hash);
         if (it != mapWallet.end()) {
             CWalletTx& prevtx = it->second;
-            if (prevtx.isConflicted()) {
-                MarkConflicted(prevtx.m_confirm.hashBlock, prevtx.m_confirm.block_height, wtx.GetHash());
+            if (auto* prev = prevtx.state<TxStateConflicted>()) {
+                MarkConflicted(prev->conflicting_block_hash, prev->conflicting_block_height, wtx.GetHash());
             }
         }
     }
     return true;
 }
 
-bool CWallet::AddToWalletIfInvolvingMe(const CTransactionRef& ptx, CWalletTx::Confirmation confirm, bool fUpdate, bool rescanning_old_block)
+bool CWallet::AddToWalletIfInvolvingMe(const CTransactionRef& ptx, const SyncTxState& state, bool fUpdate, bool rescanning_old_block)
 {
     const CTransaction& tx = *ptx;
     {
         AssertLockHeld(cs_wallet);
 
-        if (!confirm.hashBlock.IsNull()) {
+        if (auto* conf = std::get_if<TxStateConfirmed>(&state)) {
             for (const CTxIn& txin : tx.vin) {
                 std::pair<TxSpends::const_iterator, TxSpends::const_iterator> range = mapTxSpends.equal_range(txin.prevout);
                 while (range.first != range.second) {
                     if (range.first->second != tx.GetHash()) {
-                        WalletLogPrintf("Transaction %s (in block %s) conflicts with wallet transaction %s (both spend %s:%i)\n", tx.GetHash().ToString(), confirm.hashBlock.ToString(), range.first->second.ToString(), range.first->first.hash.ToString(), range.first->first.n);
-                        MarkConflicted(confirm.hashBlock, confirm.block_height, range.first->second);
+                        WalletLogPrintf("Transaction %s (in block %s) conflicts with wallet transaction %s (both spend %s:%i)\n", tx.GetHash().ToString(), conf->confirmed_block_hash.ToString(), range.first->second.ToString(), range.first->first.hash.ToString(), range.first->first.n);
+                        MarkConflicted(conf->confirmed_block_hash, conf->confirmed_block_height, range.first->second);
                     }
                     range.first++;
                 }
@@ -1070,7 +1068,8 @@ bool CWallet::AddToWalletIfInvolvingMe(const CTransactionRef& ptx, CWalletTx::Co
 
             // Block disconnection override an abandoned tx as unconfirmed
             // which means user may have to call abandontransaction again
-            return AddToWallet(MakeTransactionRef(tx), confirm, /* update_wtx= */ nullptr, /* fFlushOnClose= */ false, rescanning_old_block);
+            TxState tx_state = std::visit([](auto&& s) -> TxState { return s; }, state);
+            return AddToWallet(MakeTransactionRef(tx), tx_state, /*update_wtx=*/nullptr, /*fFlushOnClose=*/false, rescanning_old_block);
         }
     }
     return false;
@@ -1126,7 +1125,7 @@ bool CWallet::AbandonTransaction(const uint256& hashTx)
         if (currentconfirm == 0 && !wtx.isAbandoned()) {
             // If the orig tx was not in block/mempool, none of its spends can be in mempool
             assert(!wtx.InMempool());
-            wtx.setAbandoned();
+            wtx.m_state = TxStateInactive{/*abandoned=*/true};
             wtx.MarkDirty();
             batch.WriteTx(wtx);
             NotifyTransactionChanged(wtx.GetHash(), CT_UPDATED);
@@ -1178,10 +1177,7 @@ void CWallet::MarkConflicted(const uint256& hashBlock, int conflicting_height, c
         if (conflictconfirms < currentconfirm) {
             // Block is 'more conflicted' than current confirm; update.
             // Mark transaction as conflicted with this block.
-            wtx.m_confirm.nIndex = 0;
-            wtx.m_confirm.hashBlock = hashBlock;
-            wtx.m_confirm.block_height = conflicting_height;
-            wtx.setConflicted();
+            wtx.m_state = TxStateConflicted{hashBlock, conflicting_height};
             wtx.MarkDirty();
             batch.WriteTx(wtx);
             // Iterate over all its outputs, and mark transactions in the wallet that spend them conflicted too
@@ -1199,9 +1195,9 @@ void CWallet::MarkConflicted(const uint256& hashBlock, int conflicting_height, c
     }
 }
 
-void CWallet::SyncTransaction(const CTransactionRef& ptx, CWalletTx::Confirmation confirm, bool update_tx, bool rescanning_old_block)
+void CWallet::SyncTransaction(const CTransactionRef& ptx, const SyncTxState& state, bool update_tx, bool rescanning_old_block)
 {
-    if (!AddToWalletIfInvolvingMe(ptx, confirm, update_tx, rescanning_old_block))
+    if (!AddToWalletIfInvolvingMe(ptx, state, update_tx, rescanning_old_block))
         return; // Not one of ours
 
     // If a transaction changes 'conflicted' state, that changes the balance
@@ -1212,7 +1208,7 @@ void CWallet::SyncTransaction(const CTransactionRef& ptx, CWalletTx::Confirmatio
 
 void CWallet::transactionAddedToMempool(const CTransactionRef& tx, uint64_t mempool_sequence) {
     LOCK(cs_wallet);
-    SyncTransaction(tx, {CWalletTx::Status::UNCONFIRMED, /*block_height=*/0, /*block_hash=*/{}, /*block_index=*/0});
+    SyncTransaction(tx, TxStateInMempool{});
 
     auto it = mapWallet.find(tx->GetHash());
     if (it != mapWallet.end()) {
@@ -1253,7 +1249,7 @@ void CWallet::transactionRemovedFromMempool(const CTransactionRef& tx, MemPoolRe
         // distinguishing between conflicted and unconfirmed transactions are
         // imperfect, and could be improved in general, see
         // https://github.com/bitcoin-core/bitcoin-devwiki/wiki/Wallet-Transaction-Conflict-Tracking
-        SyncTransaction(tx, {CWalletTx::Status::UNCONFIRMED, /*block_height=*/0, /*block_hash=*/{}, /*block_index=*/0});
+        SyncTransaction(tx, TxStateInactive{});
     }
 }
 
@@ -1265,7 +1261,7 @@ void CWallet::blockConnected(const CBlock& block, int height)
     m_last_block_processed_height = height;
     m_last_block_processed = block_hash;
     for (size_t index = 0; index < block.vtx.size(); index++) {
-        SyncTransaction(block.vtx[index], {CWalletTx::Status::CONFIRMED, height, block_hash, (int)index});
+        SyncTransaction(block.vtx[index], TxStateConfirmed{block_hash, height, static_cast<int>(index)});
         transactionRemovedFromMempool(block.vtx[index], MemPoolRemovalReason::BLOCK, 0 /* mempool_sequence */);
     }
 }
@@ -1281,7 +1277,7 @@ void CWallet::blockDisconnected(const CBlock& block, int height)
     m_last_block_processed_height = height - 1;
     m_last_block_processed = block.hashPrevBlock;
     for (const CTransactionRef& ptx : block.vtx) {
-        SyncTransaction(ptx, {CWalletTx::Status::UNCONFIRMED, /*block_height=*/0, /*block_hash=*/{}, /*block_index=*/0});
+        SyncTransaction(ptx, TxStateInactive{});
     }
 }
 
@@ -1645,7 +1641,7 @@ CWallet::ScanResult CWallet::ScanForWalletTransactions(const uint256& start_bloc
                 break;
             }
             for (size_t posInBlock = 0; posInBlock < block.vtx.size(); ++posInBlock) {
-                SyncTransaction(block.vtx[posInBlock], {CWalletTx::Status::CONFIRMED, block_height, block_hash, (int)posInBlock}, fUpdate, /* rescanning_old_block */ true);
+                SyncTransaction(block.vtx[posInBlock], TxStateConfirmed{block_hash, block_height, static_cast<int>(posInBlock)}, fUpdate, /*rescanning_old_block=*/true);
             }
             // scan succeeded, record block as most recent successfully scanned
             result.last_scanned_block = block_hash;
@@ -1720,7 +1716,7 @@ void CWallet::ReacceptWalletTransactions()
     }
 }
 
-bool CWallet::SubmitTxMemoryPoolAndRelay(const CWalletTx& wtx, std::string& err_string, bool relay) const
+bool CWallet::SubmitTxMemoryPoolAndRelay(CWalletTx& wtx, std::string& err_string, bool relay) const
 {
     // Can't relay if wallet is not broadcasting
     if (!GetBroadcastTransactions()) return false;
@@ -1734,17 +1730,17 @@ bool CWallet::SubmitTxMemoryPoolAndRelay(const CWalletTx& wtx, std::string& err_
 
     // Submit transaction to mempool for relay
     WalletLogPrintf("Submitting wtx %s to mempool for relay\n", wtx.GetHash().ToString());
-    // We must set fInMempool here - while it will be re-set to true by the
+    // We must set TxStateInMempool here. Even though it will also be set later by the
     // entered-mempool callback, if we did not there would be a race where a
     // user could call sendmoney in a loop and hit spurious out of funds errors
     // because we think that this newly generated transaction's change is
     // unavailable as we're not yet aware that it is in the mempool.
     //
-    // Irrespective of the failure reason, un-marking fInMempool
-    // out-of-order is incorrect - it should be unmarked when
+    // If broadcast fails for any reason, trying to set wtx.m_state here would be incorrect.
+    // If transaction was previously in the mempool, it should be updated when
     // TransactionRemovedFromMempool fires.
     bool ret = chain().broadcastTransaction(wtx.tx, m_default_max_tx_fee, relay, err_string);
-    wtx.fInMempool |= ret;
+    if (ret) wtx.m_state = TxStateInMempool{};
     return ret;
 }
 
@@ -1831,7 +1827,8 @@ bool CWallet::SignTransaction(CMutableTransaction& tx) const
             return false;
         }
         const CWalletTx& wtx = mi->second;
-        coins[input.prevout] = Coin(wtx.tx->vout[input.prevout.n], wtx.m_confirm.block_height, wtx.IsCoinBase());
+        int prev_height = wtx.state<TxStateConfirmed>() ? wtx.state<TxStateConfirmed>()->confirmed_block_height : 0;
+        coins[input.prevout] = Coin(wtx.tx->vout[input.prevout.n], prev_height, wtx.IsCoinBase());
     }
     std::map<int, bilingual_str> input_errors;
     return SignTransaction(tx, coins, SIGHASH_DEFAULT, input_errors);
@@ -1956,7 +1953,7 @@ void CWallet::CommitTransaction(CTransactionRef tx, mapValue_t mapValue, std::ve
 
     // Add tx to wallet, because if it has change it's also ours,
     // otherwise just for transaction history.
-    AddToWallet(tx, {}, [&](CWalletTx& wtx, bool new_tx) {
+    AddToWallet(tx, TxStateInactive{}, [&](CWalletTx& wtx, bool new_tx) {
         CHECK_NONFATAL(wtx.mapValue.empty());
         CHECK_NONFATAL(wtx.vOrderForm.empty());
         wtx.mapValue = std::move(mapValue);
@@ -1974,7 +1971,7 @@ void CWallet::CommitTransaction(CTransactionRef tx, mapValue_t mapValue, std::ve
     }
 
     // Get the inserted-CWalletTx from mapWallet so that the
-    // fInMempool flag is cached properly
+    // wtx cached mempool state is updated correctly
     CWalletTx& wtx = mapWallet.at(tx->GetHash());
 
     if (!fBroadcastTransactions) {
@@ -2321,10 +2318,10 @@ void CWallet::GetKeyBirthTimes(std::map<CKeyID, int64_t>& mapKeyBirth) const {
     mapKeyBirth.clear();
 
     // map in which we'll infer heights of other keys
-    std::map<CKeyID, const CWalletTx::Confirmation*> mapKeyFirstBlock;
-    CWalletTx::Confirmation max_confirm;
-    max_confirm.block_height = GetLastBlockHeight() > 144 ? GetLastBlockHeight() - 144 : 0; // the tip can be reorganized; use a 144-block safety margin
-    CHECK_NONFATAL(chain().findAncestorByHeight(GetLastBlockHash(), max_confirm.block_height, FoundBlock().hash(max_confirm.hashBlock)));
+    std::map<CKeyID, const TxStateConfirmed*> mapKeyFirstBlock;
+    TxStateConfirmed max_confirm{uint256{}, /*height=*/-1, /*index=*/-1};
+    max_confirm.confirmed_block_height = GetLastBlockHeight() > 144 ? GetLastBlockHeight() - 144 : 0; // the tip can be reorganized; use a 144-block safety margin
+    CHECK_NONFATAL(chain().findAncestorByHeight(GetLastBlockHash(), max_confirm.confirmed_block_height, FoundBlock().hash(max_confirm.confirmed_block_hash)));
 
     {
         LegacyScriptPubKeyMan* spk_man = GetLegacyScriptPubKeyMan();
@@ -2352,15 +2349,15 @@ void CWallet::GetKeyBirthTimes(std::map<CKeyID, int64_t>& mapKeyBirth) const {
         for (const auto& entry : mapWallet) {
             // iterate over all wallet transactions...
             const CWalletTx &wtx = entry.second;
-            if (wtx.m_confirm.status == CWalletTx::CONFIRMED) {
+            if (auto* conf = wtx.state<TxStateConfirmed>()) {
                 // ... which are already in a block
                 for (const CTxOut &txout : wtx.tx->vout) {
                     // iterate over all their outputs
                     for (const auto &keyid : GetAffectedKeys(txout.scriptPubKey, *spk_man)) {
                         // ... and all their affected keys
                         auto rit = mapKeyFirstBlock.find(keyid);
-                        if (rit != mapKeyFirstBlock.end() && wtx.m_confirm.block_height < rit->second->block_height) {
-                            rit->second = &wtx.m_confirm;
+                        if (rit != mapKeyFirstBlock.end() && conf->confirmed_block_height < rit->second->confirmed_block_height) {
+                            rit->second = conf;
                         }
                     }
                 }
@@ -2371,7 +2368,7 @@ void CWallet::GetKeyBirthTimes(std::map<CKeyID, int64_t>& mapKeyBirth) const {
     // Extract block timestamps for those keys
     for (const auto& entry : mapKeyFirstBlock) {
         int64_t block_time;
-        CHECK_NONFATAL(chain().findBlock(entry.second->hashBlock, FoundBlock().time(block_time)));
+        CHECK_NONFATAL(chain().findBlock(entry.second->confirmed_block_hash, FoundBlock().time(block_time)));
         mapKeyBirth[entry.first] = block_time - TIMESTAMP_WINDOW; // block times can be 2h off
     }
 }
@@ -2401,11 +2398,18 @@ void CWallet::GetKeyBirthTimes(std::map<CKeyID, int64_t>& mapKeyBirth) const {
  */
 unsigned int CWallet::ComputeTimeSmart(const CWalletTx& wtx, bool rescanning_old_block) const
 {
+    std::optional<uint256> block_hash;
+    if (auto* conf = wtx.state<TxStateConfirmed>()) {
+        block_hash = conf->confirmed_block_hash;
+    } else if (auto* conf = wtx.state<TxStateConflicted>()) {
+        block_hash = conf->conflicting_block_hash;
+    }
+
     unsigned int nTimeSmart = wtx.nTimeReceived;
-    if (!wtx.isUnconfirmed() && !wtx.isAbandoned()) {
+    if (block_hash) {
         int64_t blocktime;
         int64_t block_max_time;
-        if (chain().findBlock(wtx.m_confirm.hashBlock, FoundBlock().time(blocktime).maxTime(block_max_time))) {
+        if (chain().findBlock(*block_hash, FoundBlock().time(blocktime).maxTime(block_max_time))) {
             if (rescanning_old_block) {
                 nTimeSmart = block_max_time;
             } else {
@@ -2437,7 +2441,7 @@ unsigned int CWallet::ComputeTimeSmart(const CWalletTx& wtx, bool rescanning_old
                 nTimeSmart = std::max(latestEntry, std::min(blocktime, latestNow));
             }
         } else {
-            WalletLogPrintf("%s: found %s in block %s not in index\n", __func__, wtx.GetHash().ToString(), wtx.m_confirm.hashBlock.ToString());
+            WalletLogPrintf("%s: found %s in block %s not in index\n", __func__, wtx.GetHash().ToString(), block_hash->ToString());
         }
     }
     return nTimeSmart;
@@ -2944,9 +2948,13 @@ CKeyPool::CKeyPool(const CPubKey& vchPubKeyIn, bool internalIn)
 int CWallet::GetTxDepthInMainChain(const CWalletTx& wtx) const
 {
     AssertLockHeld(cs_wallet);
-    if (wtx.isUnconfirmed() || wtx.isAbandoned()) return 0;
-
-    return (GetLastBlockHeight() - wtx.m_confirm.block_height + 1) * (wtx.isConflicted() ? -1 : 1);
+    if (auto* conf = wtx.state<TxStateConfirmed>()) {
+        return GetLastBlockHeight() - conf->confirmed_block_height + 1;
+    } else if (auto* conf = wtx.state<TxStateConflicted>()) {
+        return -1 * (GetLastBlockHeight() - conf->conflicting_block_height + 1);
+    } else {
+        return 0;
+    }
 }
 
 int CWallet::GetTxBlocksToMaturity(const CWalletTx& wtx) const
diff --git a/src/wallet/wallet.h b/src/wallet/wallet.h
index 3855ad821d..cb7178fc01 100644
--- a/src/wallet/wallet.h
+++ b/src/wallet/wallet.h
@@ -275,7 +275,7 @@ private:
      * Should be called with rescanning_old_block set to true, if the transaction is
      * not discovered in real time, but during a rescan of old blocks.
      */
-    bool AddToWalletIfInvolvingMe(const CTransactionRef& tx, CWalletTx::Confirmation confirm, bool fUpdate, bool rescanning_old_block) EXCLUSIVE_LOCKS_REQUIRED(cs_wallet);
+    bool AddToWalletIfInvolvingMe(const CTransactionRef& tx, const SyncTxState& state, bool fUpdate, bool rescanning_old_block) EXCLUSIVE_LOCKS_REQUIRED(cs_wallet);
 
     /** Mark a transaction (and its in-wallet descendants) as conflicting with a particular block. */
     void MarkConflicted(const uint256& hashBlock, int conflicting_height, const uint256& hashTx);
@@ -285,7 +285,7 @@ private:
 
     void SyncMetaData(std::pair<TxSpends::iterator, TxSpends::iterator>) EXCLUSIVE_LOCKS_REQUIRED(cs_wallet);
 
-    void SyncTransaction(const CTransactionRef& tx, CWalletTx::Confirmation confirm, bool update_tx = true, bool rescanning_old_block = false) EXCLUSIVE_LOCKS_REQUIRED(cs_wallet);
+    void SyncTransaction(const CTransactionRef& tx, const SyncTxState& state, bool update_tx = true, bool rescanning_old_block = false) EXCLUSIVE_LOCKS_REQUIRED(cs_wallet);
 
     /** WalletFlags set on this wallet. */
     std::atomic<uint64_t> m_wallet_flags{0};
@@ -508,7 +508,7 @@ public:
     //! @return true if wtx is changed and needs to be saved to disk, otherwise false
     using UpdateWalletTxFn = std::function<bool(CWalletTx& wtx, bool new_tx)>;
 
-    CWalletTx* AddToWallet(CTransactionRef tx, const CWalletTx::Confirmation& confirm, const UpdateWalletTxFn& update_wtx=nullptr, bool fFlushOnClose=true, bool rescanning_old_block = false);
+    CWalletTx* AddToWallet(CTransactionRef tx, const TxState& state, const UpdateWalletTxFn& update_wtx=nullptr, bool fFlushOnClose=true, bool rescanning_old_block = false);
     bool LoadToWallet(const uint256& hash, const UpdateWalletTxFn& fill_wtx) EXCLUSIVE_LOCKS_REQUIRED(cs_wallet);
     void transactionAddedToMempool(const CTransactionRef& tx, uint64_t mempool_sequence) override;
     void blockConnected(const CBlock& block, int height) override;
@@ -576,7 +576,7 @@ public:
     void CommitTransaction(CTransactionRef tx, mapValue_t mapValue, std::vector<std::pair<std::string, std::string>> orderForm);
 
     /** Pass this transaction to node for mempool insertion and relay to peers if flag set to true */
-    bool SubmitTxMemoryPoolAndRelay(const CWalletTx& wtx, std::string& err_string, bool relay) const;
+    bool SubmitTxMemoryPoolAndRelay(CWalletTx& wtx, std::string& err_string, bool relay) const;
 
     bool DummySignTx(CMutableTransaction &txNew, const std::set<CTxOut> &txouts, const CCoinControl* coin_control = nullptr) const
     {
diff --git a/src/wallet/walletdb.cpp b/src/wallet/walletdb.cpp
index c920d4af51..f392649bd9 100644
--- a/src/wallet/walletdb.cpp
+++ b/src/wallet/walletdb.cpp
@@ -987,7 +987,7 @@ DBErrors WalletBatch::FindWalletTx(std::vector<uint256>& vTxHash, std::list<CWal
                 uint256 hash;
                 ssKey >> hash;
                 vTxHash.push_back(hash);
-                vWtx.emplace_back(nullptr /* tx */);
+                vWtx.emplace_back(/*tx=*/nullptr, TxStateInactive{});
                 ssValue >> vWtx.back();
             }
         }