coins: add explicit `CoinsViewEmpty` noop backend

diff --git a/src/bench/ccoins_caching.cpp b/src/bench/ccoins_caching.cpp
index 82735b32..12ea0760 100644
--- a/src/bench/ccoins_caching.cpp
+++ b/src/bench/ccoins_caching.cpp
@@ -26,8 +26,7 @@ static void CCoinsCaching(benchmark::Bench& bench)
     ECC_Context ecc_context{};
 
     FillableSigningProvider keystore;
-    CCoinsView coinsDummy;
-    CCoinsViewCache coins(&coinsDummy);
+    CCoinsViewCache coins{&CoinsViewEmpty::Get()};
     std::vector<CMutableTransaction> dummyTransactions =
         SetupDummyInputs(keystore, coins, {11 * COIN, 50 * COIN, 21 * COIN, 22 * COIN});
 
diff --git a/src/bitcoin-tx.cpp b/src/bitcoin-tx.cpp
index d4702a9c..4a891ad8 100644
--- a/src/bitcoin-tx.cpp
+++ b/src/bitcoin-tx.cpp
@@ -586,8 +586,7 @@ static void MutateTxSign(CMutableTransaction& tx, const std::string& flagStr)
     // starts as a clone of the raw tx:
     CMutableTransaction mergedTx{tx};
     const CMutableTransaction txv{tx};
-    CCoinsView viewDummy;
-    CCoinsViewCache view(&viewDummy);
+    CCoinsViewCache view{&CoinsViewEmpty::Get()};
 
     if (!registers.contains("privatekeys"))
         throw std::runtime_error("privatekeys register variable must be set.");
diff --git a/src/coins.cpp b/src/coins.cpp
index 87bbdcbf..e5deef34 100644
--- a/src/coins.cpp
+++ b/src/coins.cpp
@@ -41,6 +41,12 @@ void CCoinsViewBacked::BatchWrite(CoinsViewCacheCursor& cursor, const uint256& b
 std::unique_ptr<CCoinsViewCursor> CCoinsViewBacked::Cursor() const { return base->Cursor(); }
 size_t CCoinsViewBacked::EstimateSize() const { return base->EstimateSize(); }
 
+CoinsViewEmpty& CoinsViewEmpty::Get()
+{
+    static CoinsViewEmpty instance;
+    return instance;
+}
+
 std::optional<Coin> CCoinsViewCache::PeekCoin(const COutPoint& outpoint) const
 {
     if (auto it{cacheCoins.find(outpoint)}; it != cacheCoins.end()) {
diff --git a/src/coins.h b/src/coins.h
index 68d46938..876c5ed8 100644
--- a/src/coins.h
+++ b/src/coins.h
@@ -342,6 +342,18 @@ public:
     virtual size_t EstimateSize() const { return 0; }
 };
 
+/** Noop coins view. */
+class CoinsViewEmpty : public CCoinsView
+{
+protected:
+    CoinsViewEmpty() = default;
+
+public:
+    static CoinsViewEmpty& Get();
+
+    CoinsViewEmpty(const CoinsViewEmpty&) = delete;
+    CoinsViewEmpty& operator=(const CoinsViewEmpty&) = delete;
+};
 
 /** CCoinsView backed by another CCoinsView */
 class CCoinsViewBacked : public CCoinsView
diff --git a/src/node/psbt.cpp b/src/node/psbt.cpp
index faedf0b6..9d79b42f 100644
--- a/src/node/psbt.cpp
+++ b/src/node/psbt.cpp
@@ -116,8 +116,7 @@ PSBTAnalysis AnalyzePSBT(PartiallySignedTransaction psbtx)
 
         // Estimate the size
         CMutableTransaction mtx(*psbtx.tx);
-        CCoinsView view_dummy;
-        CCoinsViewCache view(&view_dummy);
+        CCoinsViewCache view{&CoinsViewEmpty::Get()};
         bool success = true;
 
         for (unsigned int i = 0; i < psbtx.tx->vin.size(); ++i) {
diff --git a/src/rpc/rawtransaction.cpp b/src/rpc/rawtransaction.cpp
index cae9bb6b..74652c17 100644
--- a/src/rpc/rawtransaction.cpp
+++ b/src/rpc/rawtransaction.cpp
@@ -623,8 +623,7 @@ static RPCMethod combinerawtransaction()
     CMutableTransaction mergedTx(txVariants[0]);
 
     // Fetch previous transactions (inputs):
-    CCoinsView viewDummy;
-    CCoinsViewCache view(&viewDummy);
+    CCoinsViewCache view{&CoinsViewEmpty::Get()};
     {
         NodeContext& node = EnsureAnyNodeContext(request.context);
         const CTxMemPool& mempool = EnsureMemPool(node);
@@ -638,7 +637,7 @@ static RPCMethod combinerawtransaction()
             view.AccessCoin(txin.prevout); // Load entries from viewChain into view; can fail.
         }
 
-        view.SetBackend(viewDummy); // switch back to avoid locking mempool for too long
+        view.SetBackend(CoinsViewEmpty::Get()); // switch back to avoid locking mempool for too long
     }
 
     // Use CTransaction for the constant parts of the
diff --git a/src/test/coins_tests.cpp b/src/test/coins_tests.cpp
index f8de7f5d..2a180f25 100644
--- a/src/test/coins_tests.cpp
+++ b/src/test/coins_tests.cpp
@@ -38,14 +38,14 @@ bool operator==(const Coin &a, const Coin &b) {
            a.out == b.out;
 }
 
-class CCoinsViewTest : public CCoinsView
+class CCoinsViewTest : public CoinsViewEmpty
 {
     FastRandomContext& m_rng;
     uint256 hashBestBlock_;
     std::map<COutPoint, Coin> map_;
 
 public:
-    CCoinsViewTest(FastRandomContext& rng) : m_rng{rng} {}
+    explicit CCoinsViewTest(FastRandomContext& rng) : m_rng{rng} {}
 
     std::optional<Coin> GetCoin(const COutPoint& outpoint) const override
     {
@@ -677,8 +677,7 @@ public:
         }
     }
 
-    CCoinsView root;
-    CCoinsViewCacheTest base{&root};
+    CCoinsViewCacheTest base{&CoinsViewEmpty::Get()};
     CCoinsViewCacheTest cache{&base};
 };
 
@@ -1087,8 +1086,7 @@ BOOST_AUTO_TEST_CASE(coins_resource_is_used)
 
 BOOST_AUTO_TEST_CASE(ccoins_addcoin_exception_keeps_usage_balanced)
 {
-    CCoinsView root;
-    CCoinsViewCacheTest cache{&root};
+    CCoinsViewCacheTest cache{&CoinsViewEmpty::Get()};
 
     const COutPoint outpoint{Txid::FromUint256(m_rng.rand256()), m_rng.rand32()};
 
@@ -1105,8 +1103,7 @@ BOOST_AUTO_TEST_CASE(ccoins_addcoin_exception_keeps_usage_balanced)
 
 BOOST_AUTO_TEST_CASE(ccoins_emplace_duplicate_keeps_usage_balanced)
 {
-    CCoinsView root;
-    CCoinsViewCacheTest cache{&root};
+    CCoinsViewCacheTest cache{&CoinsViewEmpty::Get()};
 
     const COutPoint outpoint{Txid::FromUint256(m_rng.rand256()), m_rng.rand32()};
 
diff --git a/src/test/fuzz/coins_view.cpp b/src/test/fuzz/coins_view.cpp
index 5af5996f..c11581d2 100644
--- a/src/test/fuzz/coins_view.cpp
+++ b/src/test/fuzz/coins_view.cpp
@@ -90,11 +90,11 @@ void initialize_coins_view()
     static const auto testing_setup = MakeNoLogFileContext<>();
 }
 
-void TestCoinsView(FuzzedDataProvider& fuzzed_data_provider, CCoinsViewCache& coins_view_cache, CCoinsView* backend_coins_view, bool is_db)
+void TestCoinsView(FuzzedDataProvider& fuzzed_data_provider, CCoinsViewCache& coins_view_cache, CCoinsView* backend_coins_view)
 {
+    const bool is_db{dynamic_cast<CCoinsViewDB*>(backend_coins_view) != nullptr};
     bool good_data{true};
     auto* original_backend{backend_coins_view};
-    CCoinsView coins_view_empty{};
 
     if (is_db) coins_view_cache.SetBestBlock(uint256::ONE);
     COutPoint random_out_point;
@@ -158,7 +158,7 @@ void TestCoinsView(FuzzedDataProvider& fuzzed_data_provider, CCoinsViewCache& co
                     // Reset() clears the best block; db backends require a non-null hash.
                     if (is_db) coins_view_cache.SetBestBlock(uint256::ONE);
                 }
-                backend_coins_view = use_original_backend ? original_backend : &coins_view_empty;
+                backend_coins_view = use_original_backend ? original_backend : &CoinsViewEmpty::Get();
                 coins_view_cache.SetBackend(*backend_coins_view);
             },
             [&] {
@@ -350,9 +350,8 @@ void TestCoinsView(FuzzedDataProvider& fuzzed_data_provider, CCoinsViewCache& co
 FUZZ_TARGET(coins_view, .init = initialize_coins_view)
 {
     FuzzedDataProvider fuzzed_data_provider{buffer.data(), buffer.size()};
-    CCoinsView backend_coins_view;
-    CCoinsViewCache coins_view_cache{&backend_coins_view, /*deterministic=*/true};
-    TestCoinsView(fuzzed_data_provider, coins_view_cache, &backend_coins_view, /*is_db=*/false);
+    CCoinsViewCache coins_view_cache{&CoinsViewEmpty::Get(), /*deterministic=*/true};
+    TestCoinsView(fuzzed_data_provider, coins_view_cache, &CoinsViewEmpty::Get());
 }
 
 FUZZ_TARGET(coins_view_db, .init = initialize_coins_view)
@@ -365,7 +364,7 @@ FUZZ_TARGET(coins_view_db, .init = initialize_coins_view)
     };
     CCoinsViewDB backend_coins_view{std::move(db_params), CoinsViewOptions{}};
     CCoinsViewCache coins_view_cache{&backend_coins_view, /*deterministic=*/true};
-    TestCoinsView(fuzzed_data_provider, coins_view_cache, &backend_coins_view, /*is_db=*/true);
+    TestCoinsView(fuzzed_data_provider, coins_view_cache, &backend_coins_view);
 }
 
 // Creates a CoinsViewOverlay and a MutationGuardCoinsViewCache as the base.
@@ -375,8 +374,7 @@ FUZZ_TARGET(coins_view_db, .init = initialize_coins_view)
 FUZZ_TARGET(coins_view_overlay, .init = initialize_coins_view)
 {
     FuzzedDataProvider fuzzed_data_provider{buffer.data(), buffer.size()};
-    CCoinsView backend_base_coins_view;
-    MutationGuardCoinsViewCache backend_cache{&backend_base_coins_view, /*deterministic=*/true};
+    MutationGuardCoinsViewCache backend_cache{&CoinsViewEmpty::Get(), /*deterministic=*/true};
     CoinsViewOverlay coins_view_cache{&backend_cache, /*deterministic=*/true};
-    TestCoinsView(fuzzed_data_provider, coins_view_cache, &backend_cache, /*is_db=*/false);
+    TestCoinsView(fuzzed_data_provider, coins_view_cache, &backend_cache);
 }
diff --git a/src/test/fuzz/coinscache_sim.cpp b/src/test/fuzz/coinscache_sim.cpp
index c8534e4f..23828132 100644
--- a/src/test/fuzz/coinscache_sim.cpp
+++ b/src/test/fuzz/coinscache_sim.cpp
@@ -139,7 +139,7 @@ struct CacheLevel
  *
  * The initial state consists of the empty UTXO set.
  */
-class CoinsViewBottom final : public CCoinsView
+class CoinsViewBottom final : public CoinsViewEmpty
 {
     std::map<COutPoint, Coin> m_data;
 
@@ -153,11 +153,6 @@ public:
         return std::nullopt;
     }
 
-    uint256 GetBestBlock() const final { return {}; }
-    std::vector<uint256> GetHeadBlocks() const final { return {}; }
-    std::unique_ptr<CCoinsViewCursor> Cursor() const final { return {}; }
-    size_t EstimateSize() const final { return m_data.size(); }
-
     void BatchWrite(CoinsViewCacheCursor& cursor, const uint256&) final
     {
         for (auto it{cursor.Begin()}; it != cursor.End(); it = cursor.NextAndMaybeErase(*it)) {
diff --git a/src/test/fuzz/transaction.cpp b/src/test/fuzz/transaction.cpp
index a8b2d2a2..299db8c1 100644
--- a/src/test/fuzz/transaction.cpp
+++ b/src/test/fuzz/transaction.cpp
@@ -86,8 +86,7 @@ FUZZ_TARGET(transaction, .init = initialize_transaction)
     (void)RecursiveDynamicUsage(tx);
     (void)SignalsOptInRBF(tx);
 
-    CCoinsView coins_view;
-    const CCoinsViewCache coins_view_cache(&coins_view);
+    const CCoinsViewCache coins_view_cache{&CoinsViewEmpty::Get()};
     (void)ValidateInputsStandardness(tx, coins_view_cache);
     (void)IsWitnessStandard(tx, coins_view_cache);
 
diff --git a/src/test/script_p2sh_tests.cpp b/src/test/script_p2sh_tests.cpp
index 04a03ca4..f80090aa 100644
--- a/src/test/script_p2sh_tests.cpp
+++ b/src/test/script_p2sh_tests.cpp
@@ -277,8 +277,7 @@ BOOST_AUTO_TEST_CASE(switchover)
 
 BOOST_AUTO_TEST_CASE(ValidateInputsStandardness)
 {
-    CCoinsView coinsDummy;
-    CCoinsViewCache coins(&coinsDummy);
+    CCoinsViewCache coins{&CoinsViewEmpty::Get()};
     FillableSigningProvider keystore;
     CKey key[6];
     for (int i = 0; i < 6; i++)
diff --git a/src/test/sigopcount_tests.cpp b/src/test/sigopcount_tests.cpp
index d3fec0f9..a463f43e 100644
--- a/src/test/sigopcount_tests.cpp
+++ b/src/test/sigopcount_tests.cpp
@@ -116,8 +116,7 @@ BOOST_AUTO_TEST_CASE(GetTxSigOpCost)
     CMutableTransaction spendingTx;
 
     // Create utxo set
-    CCoinsView coinsDummy;
-    CCoinsViewCache coins(&coinsDummy);
+    CCoinsViewCache coins{&CoinsViewEmpty::Get()};
     // Create key
     CKey key = GenerateRandomKey();
     CPubKey pubkey = key.GetPubKey();
diff --git a/src/test/transaction_tests.cpp b/src/test/transaction_tests.cpp
index 2bb9e8a4..19c416c2 100644
--- a/src/test/transaction_tests.cpp
+++ b/src/test/transaction_tests.cpp
@@ -392,8 +392,7 @@ BOOST_AUTO_TEST_CASE(basic_transaction_tests)
 BOOST_AUTO_TEST_CASE(test_Get)
 {
     FillableSigningProvider keystore;
-    CCoinsView coinsDummy;
-    CCoinsViewCache coins(&coinsDummy);
+    CCoinsViewCache coins{&CoinsViewEmpty::Get()};
     std::vector<CMutableTransaction> dummyTransactions =
         SetupDummyInputs(keystore, coins, {11*CENT, 50*CENT, 21*CENT, 22*CENT});
 
@@ -749,8 +748,7 @@ BOOST_AUTO_TEST_CASE(test_witness)
 BOOST_AUTO_TEST_CASE(test_IsStandard)
 {
     FillableSigningProvider keystore;
-    CCoinsView coinsDummy;
-    CCoinsViewCache coins(&coinsDummy);
+    CCoinsViewCache coins{&CoinsViewEmpty::Get()};
     std::vector<CMutableTransaction> dummyTransactions =
         SetupDummyInputs(keystore, coins, {11*CENT, 50*CENT, 21*CENT, 22*CENT});
 
@@ -1022,8 +1020,7 @@ BOOST_AUTO_TEST_CASE(test_IsStandard)
 
 BOOST_AUTO_TEST_CASE(max_standard_legacy_sigops)
 {
-    CCoinsView coins_dummy;
-    CCoinsViewCache coins(&coins_dummy);
+    CCoinsViewCache coins{&CoinsViewEmpty::Get()};
     CKey key;
     key.MakeNewKey(true);
 
@@ -1132,8 +1129,7 @@ BOOST_AUTO_TEST_CASE(max_standard_legacy_sigops)
 BOOST_AUTO_TEST_CASE(checktxinputs_invalid_transactions_test)
 {
     auto check_invalid{[](CAmount input_value, CAmount output_value, bool coinbase, int spend_height, TxValidationResult expected_result, std::string_view expected_reason) {
-        CCoinsView coins_dummy;
-        CCoinsViewCache inputs(&coins_dummy);
+        CCoinsViewCache inputs{&CoinsViewEmpty::Get()};
 
         const COutPoint prevout{Txid::FromUint256(uint256::ONE), 0};
         inputs.AddCoin(prevout, Coin{{input_value, CScript() << OP_TRUE}, /*nHeightIn=*/1, coinbase}, /*possible_overwrite=*/false);
@@ -1181,8 +1177,7 @@ BOOST_AUTO_TEST_CASE(getvalueout_out_of_range_throws)
 /** Sanity check the return value of SpendsNonAnchorWitnessProg for various output types. */
 BOOST_AUTO_TEST_CASE(spends_witness_prog)
 {
-    CCoinsView coins_dummy;
-    CCoinsViewCache coins(&coins_dummy);
+    CCoinsViewCache coins{&CoinsViewEmpty::Get()};
     CKey key;
     key.MakeNewKey(true);
     const CPubKey pubkey{key.GetPubKey()};
diff --git a/src/test/util/setup_common.cpp b/src/test/util/setup_common.cpp
index 8b746193..5c50553e 100644
--- a/src/test/util/setup_common.cpp
+++ b/src/test/util/setup_common.cpp
@@ -465,8 +465,7 @@ std::pair<CMutableTransaction, CAmount> TestChain100Setup::CreateValidTransactio
         keystore.AddKey(input_signing_key);
     }
     // - Populate a CoinsViewCache with the unspent output
-    CCoinsView coins_view;
-    CCoinsViewCache coins_cache(&coins_view);
+    CCoinsViewCache coins_cache{&CoinsViewEmpty::Get()};
     for (const auto& input_transaction : input_transactions) {
         AddCoins(coins_cache, *input_transaction.get(), input_height);
     }
diff --git a/src/validation.cpp b/src/validation.cpp
index 2b0de23d..e15afd6c 100644
--- a/src/validation.cpp
+++ b/src/validation.cpp
@@ -437,7 +437,7 @@ class MemPoolAccept
 public:
     explicit MemPoolAccept(CTxMemPool& mempool, Chainstate& active_chainstate) :
         m_pool(mempool),
-        m_view(&m_dummy),
+        m_view(&CoinsViewEmpty::Get()),
         m_viewmempool(&active_chainstate.CoinsTip(), m_pool),
         m_active_chainstate(active_chainstate)
     {
@@ -737,10 +737,6 @@ private:
     /** When m_view is connected to m_viewmempool as its backend, it can pull coins from the mempool and from the UTXO
      * set. This is also where temporary coins are stored. */
     CCoinsViewMemPool m_viewmempool;
-    /** When m_view is connected to m_dummy, it can no longer look up coins from the mempool or UTXO set (meaning no disk
-     * operations happen), but can still return coins it accessed previously. Useful for keeping track of which coins
-     * were pulled from disk. */
-    CCoinsView m_dummy;
 
     Chainstate& m_active_chainstate;
 
@@ -867,14 +863,14 @@ bool MemPoolAccept::PreChecks(ATMPArgs& args, Workspace& ws)
         }
     }
 
-    // This is const, but calls into the back end CoinsViews. The CCoinsViewDB at the bottom of the
-    // hierarchy brings the best block into scope. See CCoinsViewDB::GetBestBlock().
-    m_view.GetBestBlock();
+    // This is const, but calls into `CCoinsViewCache::GetBestBlock()` to refresh
+    // the cached best block through `m_viewmempool` after caching inputs.
+    (void)m_view.GetBestBlock();
 
-    // we have all inputs cached now, so switch back to dummy (to protect
-    // against bugs where we pull more inputs from disk that miss being added
-    // to coins_to_uncache)
-    m_view.SetBackend(m_dummy);
+    // All required inputs are cached now, so switch m_view to the empty backend.
+    // This keeps already-fetched cache entries for later checks and prevents new
+    // backend lookups (which would avoid coins_to_uncache tracking).
+    m_view.SetBackend(CoinsViewEmpty::Get());
 
     assert(m_active_chainstate.m_blockman.LookupBlockIndex(m_view.GetBestBlock()) == m_active_chainstate.m_chain.Tip());