testnet: Introduce Testnet4

26 files changed, 258 insertions, 30 deletions

diff --git a/contrib/completions/bash/bitcoin-cli.bash b/contrib/completions/bash/bitcoin-cli.bash
index 89e01bc09a..b04fdbcb0e 100644
--- a/contrib/completions/bash/bitcoin-cli.bash
+++ b/contrib/completions/bash/bitcoin-cli.bash
@@ -9,7 +9,7 @@ _bitcoin_rpc() {
     local rpcargs=()
     for i in ${COMP_LINE}; do
         case "$i" in
-            -conf=*|-datadir=*|-regtest|-rpc*|-testnet)
+            -conf=*|-datadir=*|-regtest|-rpc*|-testnet|-testnet4)
                 rpcargs=( "${rpcargs[@]}" "$i" )
                 ;;
         esac
diff --git a/contrib/seeds/generate-seeds.py b/contrib/seeds/generate-seeds.py
index f67e7b0f4c..72dd5d28cc 100755
--- a/contrib/seeds/generate-seeds.py
+++ b/contrib/seeds/generate-seeds.py
@@ -5,11 +5,12 @@
 '''
 Script to generate list of seed nodes for kernel/chainparams.cpp.
 
-This script expects two text files in the directory that is passed as an
+This script expects three text files in the directory that is passed as an
 argument:
 
     nodes_main.txt
     nodes_test.txt
+    nodes_testnet4.txt
 
 These files must consist of lines in the format
 
@@ -171,6 +172,9 @@ def main():
     g.write('\n')
     with open(os.path.join(indir,'nodes_test.txt'), 'r', encoding="utf8") as f:
         process_nodes(g, f, 'chainparams_seed_test')
+    g.write('\n')
+    with open(os.path.join(indir,'nodes_testnet4.txt'), 'r', encoding="utf8") as f:
+        process_nodes(g, f, 'chainparams_seed_testnet4')
     g.write('#endif // BITCOIN_CHAINPARAMSSEEDS_H\n')
 
 if __name__ == '__main__':
diff --git a/doc/REST-interface.md b/doc/REST-interface.md
index 2d7d0e3769..6664bc2a3a 100644
--- a/doc/REST-interface.md
+++ b/doc/REST-interface.md
@@ -4,7 +4,7 @@ Unauthenticated REST Interface
 The REST API can be enabled with the `-rest` option.
 
 The interface runs on the same port as the JSON-RPC interface, by default port 8332 for mainnet, port 18332 for testnet,
-port 38332 for signet, and port 18443 for regtest.
+port 48332 for testnet4, port 38332 for signet, and port 18443 for regtest.
 
 REST Interface consistency guarantees
 -------------------------------------
diff --git a/doc/files.md b/doc/files.md
index 03e52f02c9..dd16548df5 100644
--- a/doc/files.md
+++ b/doc/files.md
@@ -34,12 +34,13 @@ Windows  | `%LOCALAPPDATA%\Bitcoin\` <sup>[\[1\]](#note1)</sup>
 
 3. All content of the data directory, except for `bitcoin.conf` file, is chain-specific. This means the actual data directory paths for non-mainnet cases differ:
 
-Chain option                   | Data directory path
--------------------------------|------------------------------
-`-chain=main` (default)        | *path_to_datadir*`/`
-`-chain=test` or `-testnet`    | *path_to_datadir*`/testnet3/`
-`-chain=signet` or `-signet`   | *path_to_datadir*`/signet/`
-`-chain=regtest` or `-regtest` | *path_to_datadir*`/regtest/`
+Chain option                     | Data directory path
+---------------------------------|------------------------------
+`-chain=main` (default)          | *path_to_datadir*`/`
+`-chain=test` or `-testnet`      | *path_to_datadir*`/testnet3/`
+`-chain=testnet4` or `-testnet4` | *path_to_datadir*`/testnet4/`
+`-chain=signet` or `-signet`     | *path_to_datadir*`/signet/`
+`-chain=regtest` or `-regtest`   | *path_to_datadir*`/regtest/`
 
 ## Data directory layout
 
diff --git a/doc/release-process.md b/doc/release-process.md
index 1e6d49100e..fa2c53eb0c 100644
--- a/doc/release-process.md
+++ b/doc/release-process.md
@@ -311,13 +311,15 @@ Both variables are used as a guideline for how much space the user needs on thei
 Note that all values should be taken from a **fully synced** node and have an overhead of 5-10% added on top of its base value.
 
 To calculate `m_assumed_blockchain_size`, take the size in GiB of these directories:
-- For `mainnet` -> the data directory, excluding the `/testnet3`, `/signet`, and `/regtest` directories and any overly large files, e.g. a huge `debug.log`
+- For `mainnet` -> the data directory, excluding the `/testnet3`, `/testnet4`, `/signet`, and `/regtest` directories and any overly large files, e.g. a huge `debug.log`
 - For `testnet` -> `/testnet3`
+- For `testnet4` -> `/testnet4`
 - For `signet` -> `/signet`
 
 To calculate `m_assumed_chain_state_size`, take the size in GiB of these directories:
 - For `mainnet` -> `/chainstate`
 - For `testnet` -> `/testnet3/chainstate`
+- For `testnet4` -> `/testnet4/chainstate`
 - For `signet` -> `/signet/chainstate`
 
 Notes:
diff --git a/src/bitcoin-cli.cpp b/src/bitcoin-cli.cpp
index 44fc273163..934b5fb6dc 100644
--- a/src/bitcoin-cli.cpp
+++ b/src/bitcoin-cli.cpp
@@ -75,6 +75,7 @@ static void SetupCliArgs(ArgsManager& argsman)
 
     const auto defaultBaseParams = CreateBaseChainParams(ChainType::MAIN);
     const auto testnetBaseParams = CreateBaseChainParams(ChainType::TESTNET);
+    const auto testnet4BaseParams = CreateBaseChainParams(ChainType::TESTNET4);
     const auto signetBaseParams = CreateBaseChainParams(ChainType::SIGNET);
     const auto regtestBaseParams = CreateBaseChainParams(ChainType::REGTEST);
 
@@ -98,7 +99,7 @@ static void SetupCliArgs(ArgsManager& argsman)
     argsman.AddArg("-rpcconnect=<ip>", strprintf("Send commands to node running on <ip> (default: %s)", DEFAULT_RPCCONNECT), ArgsManager::ALLOW_ANY, OptionsCategory::OPTIONS);
     argsman.AddArg("-rpccookiefile=<loc>", "Location of the auth cookie. Relative paths will be prefixed by a net-specific datadir location. (default: data dir)", ArgsManager::ALLOW_ANY, OptionsCategory::OPTIONS);
     argsman.AddArg("-rpcpassword=<pw>", "Password for JSON-RPC connections", ArgsManager::ALLOW_ANY, OptionsCategory::OPTIONS);
-    argsman.AddArg("-rpcport=<port>", strprintf("Connect to JSON-RPC on <port> (default: %u, testnet: %u, signet: %u, regtest: %u)", defaultBaseParams->RPCPort(), testnetBaseParams->RPCPort(), signetBaseParams->RPCPort(), regtestBaseParams->RPCPort()), ArgsManager::ALLOW_ANY | ArgsManager::NETWORK_ONLY, OptionsCategory::OPTIONS);
+    argsman.AddArg("-rpcport=<port>", strprintf("Connect to JSON-RPC on <port> (default: %u, testnet: %u, testnet4: %u, signet: %u, regtest: %u)", defaultBaseParams->RPCPort(), testnetBaseParams->RPCPort(), testnet4BaseParams->RPCPort(), signetBaseParams->RPCPort(), regtestBaseParams->RPCPort()), ArgsManager::ALLOW_ANY | ArgsManager::NETWORK_ONLY, OptionsCategory::OPTIONS);
     argsman.AddArg("-rpcuser=<user>", "Username for JSON-RPC connections", ArgsManager::ALLOW_ANY, OptionsCategory::OPTIONS);
     argsman.AddArg("-rpcwait", "Wait for RPC server to start", ArgsManager::ALLOW_ANY, OptionsCategory::OPTIONS);
     argsman.AddArg("-rpcwaittimeout=<n>", strprintf("Timeout in seconds to wait for the RPC server to start, or 0 for no timeout. (default: %d)", DEFAULT_WAIT_CLIENT_TIMEOUT), ArgsManager::ALLOW_ANY | ArgsManager::DISALLOW_NEGATION, OptionsCategory::OPTIONS);
@@ -428,6 +429,8 @@ private:
     std::string ChainToString() const
     {
         switch (gArgs.GetChainType()) {
+        case ChainType::TESTNET4:
+            return " testnet4";
         case ChainType::TESTNET:
             return " testnet";
         case ChainType::SIGNET:
diff --git a/src/bitcoin-wallet.cpp b/src/bitcoin-wallet.cpp
index b6f5c3f15d..7d030abe97 100644
--- a/src/bitcoin-wallet.cpp
+++ b/src/bitcoin-wallet.cpp
@@ -69,7 +69,7 @@ static std::optional<int> WalletAppInit(ArgsManager& args, int argc, char* argv[
             strUsage += "\n"
                         "bitcoin-wallet is an offline tool for creating and interacting with " PACKAGE_NAME " wallet files.\n"
                         "By default bitcoin-wallet will act on wallets in the default mainnet wallet directory in the datadir.\n"
-                        "To change the target wallet, use the -datadir, -wallet and -regtest/-signet/-testnet arguments.\n\n"
+                        "To change the target wallet, use the -datadir, -wallet and -regtest/-signet/-testnet/-testnet4 arguments.\n\n"
                         "Usage:\n"
                         "  bitcoin-wallet [options] <command>\n";
             strUsage += "\n" + args.GetHelpMessage();
diff --git a/src/chainparams.cpp b/src/chainparams.cpp
index 5d4401b719..68319e8e8b 100644
--- a/src/chainparams.cpp
+++ b/src/chainparams.cpp
@@ -115,6 +115,8 @@ std::unique_ptr<const CChainParams> CreateChainParams(const ArgsManager& args, c
         return CChainParams::Main();
     case ChainType::TESTNET:
         return CChainParams::TestNet();
+    case ChainType::TESTNET4:
+        return CChainParams::TestNet4();
     case ChainType::SIGNET: {
         auto opts = CChainParams::SigNetOptions{};
         ReadSigNetArgs(args, opts);
diff --git a/src/chainparamsbase.cpp b/src/chainparamsbase.cpp
index 8cbf9e85e0..2b57b4ca55 100644
--- a/src/chainparamsbase.cpp
+++ b/src/chainparamsbase.cpp
@@ -17,7 +17,8 @@ void SetupChainParamsBaseOptions(ArgsManager& argsman)
     argsman.AddArg("-regtest", "Enter regression test mode, which uses a special chain in which blocks can be solved instantly. "
                  "This is intended for regression testing tools and app development. Equivalent to -chain=regtest.", ArgsManager::ALLOW_ANY | ArgsManager::DEBUG_ONLY, OptionsCategory::CHAINPARAMS);
     argsman.AddArg("-testactivationheight=name@height.", "Set the activation height of 'name' (segwit, bip34, dersig, cltv, csv). (regtest-only)", ArgsManager::ALLOW_ANY | ArgsManager::DEBUG_ONLY, OptionsCategory::DEBUG_TEST);
-    argsman.AddArg("-testnet", "Use the test chain. Equivalent to -chain=test.", ArgsManager::ALLOW_ANY, OptionsCategory::CHAINPARAMS);
+    argsman.AddArg("-testnet", "Use the testnet3 chain. Equivalent to -chain=test. Support for testnet3 is deprecated and will be removed with the next release. Consider moving to testnet4 now by using -testnet4.", ArgsManager::ALLOW_ANY, OptionsCategory::CHAINPARAMS);
+    argsman.AddArg("-testnet4", "Use the testnet4 chain. Equivalent to -chain=testnet4.", ArgsManager::ALLOW_ANY, OptionsCategory::CHAINPARAMS);
     argsman.AddArg("-vbparams=deployment:start:end[:min_activation_height]", "Use given start/end times and min_activation_height for specified version bits deployment (regtest-only)", ArgsManager::ALLOW_ANY | ArgsManager::DEBUG_ONLY, OptionsCategory::CHAINPARAMS);
     argsman.AddArg("-signet", "Use the signet chain. Equivalent to -chain=signet. Note that the network is defined by the -signetchallenge parameter", ArgsManager::ALLOW_ANY, OptionsCategory::CHAINPARAMS);
     argsman.AddArg("-signetchallenge", "Blocks must satisfy the given script to be considered valid (only for signet networks; defaults to the global default signet test network challenge)", ArgsManager::ALLOW_ANY | ArgsManager::DISALLOW_NEGATION, OptionsCategory::CHAINPARAMS);
@@ -33,7 +34,7 @@ const CBaseChainParams& BaseParams()
 }
 
 /**
- * Port numbers for incoming Tor connections (8334, 18334, 38334, 18445) have
+ * Port numbers for incoming Tor connections (8334, 18334, 38334, 48334, 18445) have
  * been chosen arbitrarily to keep ranges of used ports tight.
  */
 std::unique_ptr<CBaseChainParams> CreateBaseChainParams(const ChainType chain)
@@ -43,6 +44,8 @@ std::unique_ptr<CBaseChainParams> CreateBaseChainParams(const ChainType chain)
         return std::make_unique<CBaseChainParams>("", 8332, 8334);
     case ChainType::TESTNET:
         return std::make_unique<CBaseChainParams>("testnet3", 18332, 18334);
+    case ChainType::TESTNET4:
+        return std::make_unique<CBaseChainParams>("testnet4", 48332, 48334);
     case ChainType::SIGNET:
         return std::make_unique<CBaseChainParams>("signet", 38332, 38334);
     case ChainType::REGTEST:
diff --git a/src/chainparamsseeds.h b/src/chainparamsseeds.h
index 554d0cae5a..2a7e52316a 100644
--- a/src/chainparamsseeds.h
+++ b/src/chainparamsseeds.h
@@ -1786,4 +1786,16 @@ static const uint8_t chainparams_seed_test[] = {
     0x04,0x20,0xbd,0x0e,0xc8,0x73,0x43,0xa7,0xc6,0x25,0x15,0xcf,0x3e,0x23,0xa8,0xb0,0xbf,0xe8,0x20,0xa7,0xec,0x2a,0xf6,0x37,0x6c,0x60,0x5e,0x4d,0xed,0xf4,0xb1,0xef,0xf7,0xb2,0x47,0x9d,
     0x04,0x20,0xc8,0x88,0xfe,0x71,0x5f,0xa3,0x6c,0x96,0x6a,0xd7,0x9e,0x38,0x84,0x9f,0x44,0xe1,0x6b,0xdc,0x98,0x31,0xad,0x96,0x29,0xe7,0x00,0x83,0x63,0x03,0xae,0x69,0x2e,0x63,0x47,0x9d,
 };
+
+static const uint8_t chainparams_seed_testnet4[] = {
+    0x01,0x04,0x39,0x80,0xb0,0xa3,0xbc,0xcd,
+    0x01,0x04,0x33,0x9e,0xf8,0x08,0xbc,0xcd,
+    0x01,0x04,0x5f,0xd9,0x49,0xa2,0xbc,0xcd,
+    0x01,0x04,0x12,0xbd,0x9c,0x66,0xbc,0xcd,
+    0x01,0x04,0x67,0x63,0xab,0xd4,0xbc,0xcd,
+    0x01,0x04,0x52,0x43,0x66,0x0f,0xbc,0xcd,
+    0x01,0x04,0x58,0x63,0xf8,0x32,0xbc,0xcd,
+    0x01,0x04,0x67,0xa5,0xc0,0xd2,0xbc,0xcd,
+    0x01,0x04,0x12,0xc9,0xcf,0x37,0xbc,0xcd,
+};
 #endif // BITCOIN_CHAINPARAMSSEEDS_H
diff --git a/src/common/args.cpp b/src/common/args.cpp
index caff36fdb3..a37a16b62b 100644
--- a/src/common/args.cpp
+++ b/src/common/args.cpp
@@ -159,6 +159,7 @@ std::list<SectionInfo> ArgsManager::GetUnrecognizedSections() const
         ChainTypeToString(ChainType::REGTEST),
         ChainTypeToString(ChainType::SIGNET),
         ChainTypeToString(ChainType::TESTNET),
+        ChainTypeToString(ChainType::TESTNET4),
         ChainTypeToString(ChainType::MAIN),
     };
 
@@ -773,10 +774,11 @@ std::variant<ChainType, std::string> ArgsManager::GetChainArg() const
     const bool fRegTest = get_net("-regtest");
     const bool fSigNet  = get_net("-signet");
     const bool fTestNet = get_net("-testnet");
+    const bool fTestNet4 = get_net("-testnet4");
     const auto chain_arg = GetArg("-chain");
 
-    if ((int)chain_arg.has_value() + (int)fRegTest + (int)fSigNet + (int)fTestNet > 1) {
-        throw std::runtime_error("Invalid combination of -regtest, -signet, -testnet and -chain. Can use at most one.");
+    if ((int)chain_arg.has_value() + (int)fRegTest + (int)fSigNet + (int)fTestNet + (int)fTestNet4 > 1) {
+        throw std::runtime_error("Invalid combination of -regtest, -signet, -testnet, -testnet4 and -chain. Can use at most one.");
     }
     if (chain_arg) {
         if (auto parsed = ChainTypeFromString(*chain_arg)) return *parsed;
@@ -786,6 +788,7 @@ std::variant<ChainType, std::string> ArgsManager::GetChainArg() const
     if (fRegTest) return ChainType::REGTEST;
     if (fSigNet) return ChainType::SIGNET;
     if (fTestNet) return ChainType::TESTNET;
+    if (fTestNet4) return ChainType::TESTNET4;
     return ChainType::MAIN;
 }
 
diff --git a/src/common/args.h b/src/common/args.h
index 78a61313b9..323a86d8dc 100644
--- a/src/common/args.h
+++ b/src/common/args.h
@@ -423,7 +423,7 @@ private:
     fs::path GetDataDir(bool net_specific) const;
 
     /**
-     * Return -regtest/-signet/-testnet/-chain= setting as a ChainType enum if a
+     * Return -regtest/-signet/-testnet/-testnet4/-chain= setting as a ChainType enum if a
      * recognized chain type was set, or as a string if an unrecognized chain
      * name was set. Raise an exception if an invalid combination of flags was
      * provided.
diff --git a/src/consensus/params.h b/src/consensus/params.h
index 25f53eb620..d970e41637 100644
--- a/src/consensus/params.h
+++ b/src/consensus/params.h
@@ -108,6 +108,7 @@ struct Params {
     /** Proof of work parameters */
     uint256 powLimit;
     bool fPowAllowMinDifficultyBlocks;
+    bool enforce_BIP94;
     bool fPowNoRetargeting;
     int64_t nPowTargetSpacing;
     int64_t nPowTargetTimespan;
diff --git a/src/init.cpp b/src/init.cpp
index 9e570d6128..8c5e1f0037 100644
--- a/src/init.cpp
+++ b/src/init.cpp
@@ -450,10 +450,12 @@ void SetupServerArgs(ArgsManager& argsman)
 
     const auto defaultBaseParams = CreateBaseChainParams(ChainType::MAIN);
     const auto testnetBaseParams = CreateBaseChainParams(ChainType::TESTNET);
+    const auto testnet4BaseParams = CreateBaseChainParams(ChainType::TESTNET4);
     const auto signetBaseParams = CreateBaseChainParams(ChainType::SIGNET);
     const auto regtestBaseParams = CreateBaseChainParams(ChainType::REGTEST);
     const auto defaultChainParams = CreateChainParams(argsman, ChainType::MAIN);
     const auto testnetChainParams = CreateChainParams(argsman, ChainType::TESTNET);
+    const auto testnet4ChainParams = CreateChainParams(argsman, ChainType::TESTNET4);
     const auto signetChainParams = CreateChainParams(argsman, ChainType::SIGNET);
     const auto regtestChainParams = CreateChainParams(argsman, ChainType::REGTEST);
 
@@ -467,7 +469,7 @@ void SetupServerArgs(ArgsManager& argsman)
 #if HAVE_SYSTEM
     argsman.AddArg("-alertnotify=<cmd>", "Execute command when an alert is raised (%s in cmd is replaced by message)", ArgsManager::ALLOW_ANY, OptionsCategory::OPTIONS);
 #endif
-    argsman.AddArg("-assumevalid=<hex>", strprintf("If this block is in the chain assume that it and its ancestors are valid and potentially skip their script verification (0 to verify all, default: %s, testnet: %s, signet: %s)", defaultChainParams->GetConsensus().defaultAssumeValid.GetHex(), testnetChainParams->GetConsensus().defaultAssumeValid.GetHex(), signetChainParams->GetConsensus().defaultAssumeValid.GetHex()), ArgsManager::ALLOW_ANY, OptionsCategory::OPTIONS);
+    argsman.AddArg("-assumevalid=<hex>", strprintf("If this block is in the chain assume that it and its ancestors are valid and potentially skip their script verification (0 to verify all, default: %s, testnet3: %s, testnet4: %s, signet: %s)", defaultChainParams->GetConsensus().defaultAssumeValid.GetHex(), testnetChainParams->GetConsensus().defaultAssumeValid.GetHex(), testnet4ChainParams->GetConsensus().defaultAssumeValid.GetHex(), signetChainParams->GetConsensus().defaultAssumeValid.GetHex()), ArgsManager::ALLOW_ANY, OptionsCategory::OPTIONS);
     argsman.AddArg("-blocksdir=<dir>", "Specify directory to hold blocks subdirectory for *.dat files (default: <datadir>)", ArgsManager::ALLOW_ANY, OptionsCategory::OPTIONS);
     argsman.AddArg("-fastprune", "Use smaller block files and lower minimum prune height for testing purposes", ArgsManager::ALLOW_ANY | ArgsManager::DEBUG_ONLY, OptionsCategory::DEBUG_TEST);
 #if HAVE_SYSTEM
@@ -486,7 +488,7 @@ void SetupServerArgs(ArgsManager& argsman)
     argsman.AddArg("-maxmempool=<n>", strprintf("Keep the transaction memory pool below <n> megabytes (default: %u)", DEFAULT_MAX_MEMPOOL_SIZE_MB), ArgsManager::ALLOW_ANY, OptionsCategory::OPTIONS);
     argsman.AddArg("-maxorphantx=<n>", strprintf("Keep at most <n> unconnectable transactions in memory (default: %u)", DEFAULT_MAX_ORPHAN_TRANSACTIONS), ArgsManager::ALLOW_ANY, OptionsCategory::OPTIONS);
     argsman.AddArg("-mempoolexpiry=<n>", strprintf("Do not keep transactions in the mempool longer than <n> hours (default: %u)", DEFAULT_MEMPOOL_EXPIRY_HOURS), ArgsManager::ALLOW_ANY, OptionsCategory::OPTIONS);
-    argsman.AddArg("-minimumchainwork=<hex>", strprintf("Minimum work assumed to exist on a valid chain in hex (default: %s, testnet: %s, signet: %s)", defaultChainParams->GetConsensus().nMinimumChainWork.GetHex(), testnetChainParams->GetConsensus().nMinimumChainWork.GetHex(), signetChainParams->GetConsensus().nMinimumChainWork.GetHex()), ArgsManager::ALLOW_ANY | ArgsManager::DEBUG_ONLY, OptionsCategory::OPTIONS);
+    argsman.AddArg("-minimumchainwork=<hex>", strprintf("Minimum work assumed to exist on a valid chain in hex (default: %s, testnet3: %s, testnet4: %s, signet: %s)", defaultChainParams->GetConsensus().nMinimumChainWork.GetHex(), testnetChainParams->GetConsensus().nMinimumChainWork.GetHex(), testnet4ChainParams->GetConsensus().nMinimumChainWork.GetHex(), signetChainParams->GetConsensus().nMinimumChainWork.GetHex()), ArgsManager::ALLOW_ANY | ArgsManager::DEBUG_ONLY, OptionsCategory::OPTIONS);
     argsman.AddArg("-par=<n>", strprintf("Set the number of script verification threads (0 = auto, up to %d, <0 = leave that many cores free, default: %d)",
         MAX_SCRIPTCHECK_THREADS, DEFAULT_SCRIPTCHECK_THREADS), ArgsManager::ALLOW_ANY, OptionsCategory::OPTIONS);
     argsman.AddArg("-persistmempool", strprintf("Whether to save the mempool on shutdown and load on restart (default: %u)", DEFAULT_PERSIST_MEMPOOL), ArgsManager::ALLOW_ANY, OptionsCategory::OPTIONS);
@@ -515,7 +517,7 @@ void SetupServerArgs(ArgsManager& argsman)
     argsman.AddArg("-addnode=<ip>", strprintf("Add a node to connect to and attempt to keep the connection open (see the addnode RPC help for more info). This option can be specified multiple times to add multiple nodes; connections are limited to %u at a time and are counted separately from the -maxconnections limit.", MAX_ADDNODE_CONNECTIONS), ArgsManager::ALLOW_ANY | ArgsManager::NETWORK_ONLY, OptionsCategory::CONNECTION);
     argsman.AddArg("-asmap=<file>", strprintf("Specify asn mapping used for bucketing of the peers (default: %s). Relative paths will be prefixed by the net-specific datadir location.", DEFAULT_ASMAP_FILENAME), ArgsManager::ALLOW_ANY, OptionsCategory::CONNECTION);
     argsman.AddArg("-bantime=<n>", strprintf("Default duration (in seconds) of manually configured bans (default: %u)", DEFAULT_MISBEHAVING_BANTIME), ArgsManager::ALLOW_ANY, OptionsCategory::CONNECTION);
-    argsman.AddArg("-bind=<addr>[:<port>][=onion]", strprintf("Bind to given address and always listen on it (default: 0.0.0.0). Use [host]:port notation for IPv6. Append =onion to tag any incoming connections to that address and port as incoming Tor connections (default: 127.0.0.1:%u=onion, testnet: 127.0.0.1:%u=onion, signet: 127.0.0.1:%u=onion, regtest: 127.0.0.1:%u=onion)", defaultBaseParams->OnionServiceTargetPort(), testnetBaseParams->OnionServiceTargetPort(), signetBaseParams->OnionServiceTargetPort(), regtestBaseParams->OnionServiceTargetPort()), ArgsManager::ALLOW_ANY | ArgsManager::NETWORK_ONLY, OptionsCategory::CONNECTION);
+    argsman.AddArg("-bind=<addr>[:<port>][=onion]", strprintf("Bind to given address and always listen on it (default: 0.0.0.0). Use [host]:port notation for IPv6. Append =onion to tag any incoming connections to that address and port as incoming Tor connections (default: 127.0.0.1:%u=onion, testnet3: 127.0.0.1:%u=onion, testnet4: 127.0.0.1:%u=onion, signet: 127.0.0.1:%u=onion, regtest: 127.0.0.1:%u=onion)", defaultBaseParams->OnionServiceTargetPort(), testnetBaseParams->OnionServiceTargetPort(), testnet4BaseParams->OnionServiceTargetPort(), signetBaseParams->OnionServiceTargetPort(), regtestBaseParams->OnionServiceTargetPort()), ArgsManager::ALLOW_ANY | ArgsManager::NETWORK_ONLY, OptionsCategory::CONNECTION);
     argsman.AddArg("-cjdnsreachable", "If set, then this host is configured for CJDNS (connecting to fc00::/8 addresses would lead us to the CJDNS network, see doc/cjdns.md) (default: 0)", ArgsManager::ALLOW_ANY, OptionsCategory::CONNECTION);
     argsman.AddArg("-connect=<ip>", "Connect only to the specified node; -noconnect disables automatic connections (the rules for this peer are the same as for -addnode). This option can be specified multiple times to connect to multiple nodes.", ArgsManager::ALLOW_ANY | ArgsManager::NETWORK_ONLY, OptionsCategory::CONNECTION);
     argsman.AddArg("-discover", "Discover own IP addresses (default: 1 when listening and no -externalip or -proxy)", ArgsManager::ALLOW_ANY, OptionsCategory::CONNECTION);
@@ -542,7 +544,7 @@ void SetupServerArgs(ArgsManager& argsman)
     argsman.AddArg("-peerbloomfilters", strprintf("Support filtering of blocks and transaction with bloom filters (default: %u)", DEFAULT_PEERBLOOMFILTERS), ArgsManager::ALLOW_ANY, OptionsCategory::CONNECTION);
     argsman.AddArg("-peerblockfilters", strprintf("Serve compact block filters to peers per BIP 157 (default: %u)", DEFAULT_PEERBLOCKFILTERS), ArgsManager::ALLOW_ANY, OptionsCategory::CONNECTION);
     argsman.AddArg("-txreconciliation", strprintf("Enable transaction reconciliations per BIP 330 (default: %d)", DEFAULT_TXRECONCILIATION_ENABLE), ArgsManager::ALLOW_ANY | ArgsManager::DEBUG_ONLY, OptionsCategory::CONNECTION);
-    argsman.AddArg("-port=<port>", strprintf("Listen for connections on <port> (default: %u, testnet: %u, signet: %u, regtest: %u). Not relevant for I2P (see doc/i2p.md).", defaultChainParams->GetDefaultPort(), testnetChainParams->GetDefaultPort(), signetChainParams->GetDefaultPort(), regtestChainParams->GetDefaultPort()), ArgsManager::ALLOW_ANY | ArgsManager::NETWORK_ONLY, OptionsCategory::CONNECTION);
+    argsman.AddArg("-port=<port>", strprintf("Listen for connections on <port> (default: %u, testnet3: %u, testnet4: %u, signet: %u, regtest: %u). Not relevant for I2P (see doc/i2p.md).", defaultChainParams->GetDefaultPort(), testnetChainParams->GetDefaultPort(), testnet4ChainParams->GetDefaultPort(), signetChainParams->GetDefaultPort(), regtestChainParams->GetDefaultPort()), ArgsManager::ALLOW_ANY | ArgsManager::NETWORK_ONLY, OptionsCategory::CONNECTION);
 #ifdef HAVE_SOCKADDR_UN
     argsman.AddArg("-proxy=<ip:port|path>", "Connect through SOCKS5 proxy, set -noproxy to disable (default: disabled). May be a local file path prefixed with 'unix:' if the proxy supports it.", ArgsManager::ALLOW_ANY | ArgsManager::DISALLOW_ELISION, OptionsCategory::CONNECTION);
 #else
@@ -659,7 +661,7 @@ void SetupServerArgs(ArgsManager& argsman)
     argsman.AddArg("-rpccookiefile=<loc>", "Location of the auth cookie. Relative paths will be prefixed by a net-specific datadir location. (default: data dir)", ArgsManager::ALLOW_ANY, OptionsCategory::RPC);
     argsman.AddArg("-rpccookieperms=<readable-by>", strprintf("Set permissions on the RPC auth cookie file so that it is readable by [owner|group|all] (default: owner [via umask 0077])"), ArgsManager::ALLOW_ANY, OptionsCategory::RPC);
     argsman.AddArg("-rpcpassword=<pw>", "Password for JSON-RPC connections", ArgsManager::ALLOW_ANY | ArgsManager::SENSITIVE, OptionsCategory::RPC);
-    argsman.AddArg("-rpcport=<port>", strprintf("Listen for JSON-RPC connections on <port> (default: %u, testnet: %u, signet: %u, regtest: %u)", defaultBaseParams->RPCPort(), testnetBaseParams->RPCPort(), signetBaseParams->RPCPort(), regtestBaseParams->RPCPort()), ArgsManager::ALLOW_ANY | ArgsManager::NETWORK_ONLY, OptionsCategory::RPC);
+    argsman.AddArg("-rpcport=<port>", strprintf("Listen for JSON-RPC connections on <port> (default: %u, testnet3: %u, testnet4: %u, signet: %u, regtest: %u)", defaultBaseParams->RPCPort(), testnetBaseParams->RPCPort(), testnet4BaseParams->RPCPort(), signetBaseParams->RPCPort(), regtestBaseParams->RPCPort()), ArgsManager::ALLOW_ANY | ArgsManager::NETWORK_ONLY, OptionsCategory::RPC);
     argsman.AddArg("-rpcservertimeout=<n>", strprintf("Timeout during HTTP requests (default: %d)", DEFAULT_HTTP_SERVER_TIMEOUT), ArgsManager::ALLOW_ANY | ArgsManager::DEBUG_ONLY, OptionsCategory::RPC);
     argsman.AddArg("-rpcthreads=<n>", strprintf("Set the number of threads to service RPC calls (default: %d)", DEFAULT_HTTP_THREADS), ArgsManager::ALLOW_ANY, OptionsCategory::RPC);
     argsman.AddArg("-rpcuser=<user>", "Username for JSON-RPC connections", ArgsManager::ALLOW_ANY | ArgsManager::SENSITIVE, OptionsCategory::RPC);
@@ -906,6 +908,11 @@ bool AppInitParameterInteraction(const ArgsManager& args)
         return InitError(errors);
     }
 
+    // Testnet3 deprecation warning
+    if (chain == ChainType::TESTNET) {
+        LogInfo("Warning: Support for testnet3 is deprecated and will be removed in an upcoming release. Consider switching to testnet4.\n");
+    }
+
     // Warn if unrecognized section name are present in the config file.
     bilingual_str warnings;
     for (const auto& section : args.GetUnrecognizedSections()) {
diff --git a/src/kernel/chainparams.cpp b/src/kernel/chainparams.cpp
index 0a5b7f9f0d..bbddc3dfec 100644
--- a/src/kernel/chainparams.cpp
+++ b/src/kernel/chainparams.cpp
@@ -100,6 +100,7 @@ public:
         consensus.nPowTargetTimespan = 14 * 24 * 60 * 60; // two weeks
         consensus.nPowTargetSpacing = 10 * 60;
         consensus.fPowAllowMinDifficultyBlocks = false;
+        consensus.enforce_BIP94 = false;
         consensus.fPowNoRetargeting = false;
         consensus.nRuleChangeActivationThreshold = 1815; // 90% of 2016
         consensus.nMinerConfirmationWindow = 2016; // nPowTargetTimespan / nPowTargetSpacing
@@ -219,6 +220,7 @@ public:
         consensus.nPowTargetTimespan = 14 * 24 * 60 * 60; // two weeks
         consensus.nPowTargetSpacing = 10 * 60;
         consensus.fPowAllowMinDifficultyBlocks = true;
+        consensus.enforce_BIP94 = false;
         consensus.fPowNoRetargeting = false;
         consensus.nRuleChangeActivationThreshold = 1512; // 75% for testchains
         consensus.nMinerConfirmationWindow = 2016; // nPowTargetTimespan / nPowTargetSpacing
@@ -297,6 +299,104 @@ public:
 };
 
 /**
+ * Testnet (v4): public test network which is reset from time to time.
+ */
+class CTestNet4Params : public CChainParams {
+public:
+    CTestNet4Params() {
+        m_chain_type = ChainType::TESTNET4;
+        consensus.signet_blocks = false;
+        consensus.signet_challenge.clear();
+        consensus.nSubsidyHalvingInterval = 210000;
+        consensus.BIP34Height = 1;
+        consensus.BIP34Hash = uint256{};
+        consensus.BIP65Height = 1;
+        consensus.BIP66Height = 1;
+        consensus.CSVHeight = 1;
+        consensus.SegwitHeight = 1;
+        consensus.MinBIP9WarningHeight = 0;
+        consensus.powLimit = uint256S("00000000ffffffffffffffffffffffffffffffffffffffffffffffffffffffff");
+        consensus.nPowTargetTimespan = 14 * 24 * 60 * 60; // two weeks
+        consensus.nPowTargetSpacing = 10 * 60;
+        consensus.fPowAllowMinDifficultyBlocks = true;
+        consensus.enforce_BIP94 = true;
+        consensus.fPowNoRetargeting = false;
+        consensus.nRuleChangeActivationThreshold = 1512; // 75% for testchains
+        consensus.nMinerConfirmationWindow = 2016; // nPowTargetTimespan / nPowTargetSpacing
+        consensus.vDeployments[Consensus::DEPLOYMENT_TESTDUMMY].bit = 28;
+        consensus.vDeployments[Consensus::DEPLOYMENT_TESTDUMMY].nStartTime = Consensus::BIP9Deployment::NEVER_ACTIVE;
+        consensus.vDeployments[Consensus::DEPLOYMENT_TESTDUMMY].nTimeout = Consensus::BIP9Deployment::NO_TIMEOUT;
+        consensus.vDeployments[Consensus::DEPLOYMENT_TESTDUMMY].min_activation_height = 0; // No activation delay
+
+        // Deployment of Taproot (BIPs 340-342)
+        consensus.vDeployments[Consensus::DEPLOYMENT_TAPROOT].bit = 2;
+        consensus.vDeployments[Consensus::DEPLOYMENT_TAPROOT].nStartTime = Consensus::BIP9Deployment::ALWAYS_ACTIVE;
+        consensus.vDeployments[Consensus::DEPLOYMENT_TAPROOT].nTimeout = Consensus::BIP9Deployment::NO_TIMEOUT;
+        consensus.vDeployments[Consensus::DEPLOYMENT_TAPROOT].min_activation_height = 0; // No activation delay
+
+        consensus.nMinimumChainWork = uint256{};
+        consensus.defaultAssumeValid = uint256{};
+
+        pchMessageStart[0] = 0x1c;
+        pchMessageStart[1] = 0x16;
+        pchMessageStart[2] = 0x3f;
+        pchMessageStart[3] = 0x28;
+        nDefaultPort = 48333;
+        nPruneAfterHeight = 1000;
+        m_assumed_blockchain_size = 0;
+        m_assumed_chain_state_size = 0;
+
+        const char* testnet4_genesis_msg = "03/May/2024 000000000000000000001ebd58c244970b3aa9d783bb001011fbe8ea8e98e00e";
+        const CScript testnet4_genesis_script = CScript() << ParseHex("000000000000000000000000000000000000000000000000000000000000000000") << OP_CHECKSIG;
+        genesis = CreateGenesisBlock(testnet4_genesis_msg,
+                testnet4_genesis_script,
+                1714777860,
+                393743547,
+                0x1d00ffff,
+                1,
+                50 * COIN);
+        consensus.hashGenesisBlock = genesis.GetHash();
+        assert(consensus.hashGenesisBlock == uint256S("0x00000000da84f2bafbbc53dee25a72ae507ff4914b867c565be350b0da8bf043"));
+        assert(genesis.hashMerkleRoot == uint256S("0x7aa0a7ae1e223414cb807e40cd57e667b718e42aaf9306db9102fe28912b7b4e"));
+
+        vFixedSeeds.clear();
+        vSeeds.clear();
+        // nodes with support for servicebits filtering should be at the top
+        vSeeds.emplace_back("seed.testnet4.bitcoin.sprovoost.nl."); // Sjors Provoost
+        vSeeds.emplace_back("seed.testnet4.wiz.biz."); // Jason Maurice
+
+        base58Prefixes[PUBKEY_ADDRESS] = std::vector<unsigned char>(1,111);
+        base58Prefixes[SCRIPT_ADDRESS] = std::vector<unsigned char>(1,196);
+        base58Prefixes[SECRET_KEY] =     std::vector<unsigned char>(1,239);
+        base58Prefixes[EXT_PUBLIC_KEY] = {0x04, 0x35, 0x87, 0xCF};
+        base58Prefixes[EXT_SECRET_KEY] = {0x04, 0x35, 0x83, 0x94};
+
+        bech32_hrp = "tb";
+
+        vFixedSeeds = std::vector<uint8_t>(std::begin(chainparams_seed_testnet4), std::end(chainparams_seed_testnet4));
+
+        fDefaultConsistencyChecks = false;
+        m_is_mockable_chain = false;
+
+        checkpointData = {
+            {
+                {},
+            }
+        };
+
+        m_assumeutxo_data = {
+            {}
+        };
+
+        chainTxData = ChainTxData{
+            .nTime    = 0,
+            .tx_count = 0,
+            .dTxRate  = 0,
+        };
+    }
+};
+
+/**
  * Signet: test network with an additional consensus parameter (see BIP325).
  */
 class SigNetParams : public CChainParams {
@@ -356,6 +456,7 @@ public:
         consensus.nPowTargetTimespan = 14 * 24 * 60 * 60; // two weeks
         consensus.nPowTargetSpacing = 10 * 60;
         consensus.fPowAllowMinDifficultyBlocks = false;
+        consensus.enforce_BIP94 = false;
         consensus.fPowNoRetargeting = false;
         consensus.nRuleChangeActivationThreshold = 1815; // 90% of 2016
         consensus.nMinerConfirmationWindow = 2016; // nPowTargetTimespan / nPowTargetSpacing
@@ -434,6 +535,7 @@ public:
         consensus.nPowTargetTimespan = 14 * 24 * 60 * 60; // two weeks
         consensus.nPowTargetSpacing = 10 * 60;
         consensus.fPowAllowMinDifficultyBlocks = true;
+        consensus.enforce_BIP94 = false;
         consensus.fPowNoRetargeting = true;
         consensus.nRuleChangeActivationThreshold = 108; // 75% for testchains
         consensus.nMinerConfirmationWindow = 144; // Faster than normal for regtest (144 instead of 2016)
@@ -563,6 +665,11 @@ std::unique_ptr<const CChainParams> CChainParams::TestNet()
     return std::make_unique<const CTestNetParams>();
 }
 
+std::unique_ptr<const CChainParams> CChainParams::TestNet4()
+{
+    return std::make_unique<const CTestNet4Params>();
+}
+
 std::vector<int> CChainParams::GetAvailableSnapshotHeights() const
 {
     std::vector<int> heights;
diff --git a/src/kernel/chainparams.h b/src/kernel/chainparams.h
index e367de2f93..c4584600fd 100644
--- a/src/kernel/chainparams.h
+++ b/src/kernel/chainparams.h
@@ -161,6 +161,7 @@ public:
     static std::unique_ptr<const CChainParams> SigNet(const SigNetOptions& options);
     static std::unique_ptr<const CChainParams> Main();
     static std::unique_ptr<const CChainParams> TestNet();
+    static std::unique_ptr<const CChainParams> TestNet4();
 
 protected:
     CChainParams() = default;
diff --git a/src/qt/guiconstants.h b/src/qt/guiconstants.h
index 0386689baf..30ffa302a4 100644
--- a/src/qt/guiconstants.h
+++ b/src/qt/guiconstants.h
@@ -50,6 +50,7 @@ static const int TOOLTIP_WRAP_THRESHOLD = 80;
 #define QAPP_ORG_DOMAIN "bitcoin.org"
 #define QAPP_APP_NAME_DEFAULT "Bitcoin-Qt"
 #define QAPP_APP_NAME_TESTNET "Bitcoin-Qt-testnet"
+#define QAPP_APP_NAME_TESTNET4 "Bitcoin-Qt-testnet4"
 #define QAPP_APP_NAME_SIGNET "Bitcoin-Qt-signet"
 #define QAPP_APP_NAME_REGTEST "Bitcoin-Qt-regtest"
 
diff --git a/src/qt/guiutil.cpp b/src/qt/guiutil.cpp
index 0e3a0d9a9d..baa19d7c24 100644
--- a/src/qt/guiutil.cpp
+++ b/src/qt/guiutil.cpp
@@ -115,6 +115,7 @@ static std::string DummyAddress(const CChainParams &params)
         break;
     case ChainType::SIGNET:
     case ChainType::TESTNET:
+    case ChainType::TESTNET4:
         addr = "tb1p35yvjel7srp783ztf8v6jdra7dhfzk5jaun8xz2qp6ws7z80n4tqa6qnlg";
         break;
     case ChainType::REGTEST:
diff --git a/src/qt/networkstyle.cpp b/src/qt/networkstyle.cpp
index b6314f5533..d3f7c02d05 100644
--- a/src/qt/networkstyle.cpp
+++ b/src/qt/networkstyle.cpp
@@ -19,6 +19,7 @@ static const struct {
 } network_styles[] = {
     {ChainType::MAIN, QAPP_APP_NAME_DEFAULT, 0, 0},
     {ChainType::TESTNET, QAPP_APP_NAME_TESTNET, 70, 30},
+    {ChainType::TESTNET4, QAPP_APP_NAME_TESTNET4, 70, 30},
     {ChainType::SIGNET, QAPP_APP_NAME_SIGNET, 35, 15},
     {ChainType::REGTEST, QAPP_APP_NAME_REGTEST, 160, 30},
 };
diff --git a/src/test/argsman_tests.cpp b/src/test/argsman_tests.cpp
index 5f0318e8c4..297595a9cf 100644
--- a/src/test/argsman_tests.cpp
+++ b/src/test/argsman_tests.cpp
@@ -644,10 +644,12 @@ BOOST_AUTO_TEST_CASE(util_GetChainTypeString)
 {
     TestArgsManager test_args;
     const auto testnet = std::make_pair("-testnet", ArgsManager::ALLOW_ANY);
+    const auto testnet4 = std::make_pair("-testnet4", ArgsManager::ALLOW_ANY);
     const auto regtest = std::make_pair("-regtest", ArgsManager::ALLOW_ANY);
-    test_args.SetupArgs({testnet, regtest});
+    test_args.SetupArgs({testnet, testnet4, regtest});
 
     const char* argv_testnet[] = {"cmd", "-testnet"};
+    const char* argv_testnet4[] = {"cmd", "-testnet4"};
     const char* argv_regtest[] = {"cmd", "-regtest"};
     const char* argv_test_no_reg[] = {"cmd", "-testnet", "-noregtest"};
     const char* argv_both[] = {"cmd", "-testnet", "-regtest"};
@@ -663,6 +665,12 @@ BOOST_AUTO_TEST_CASE(util_GetChainTypeString)
     BOOST_CHECK(test_args.ParseParameters(2, argv_testnet, error));
     BOOST_CHECK_EQUAL(test_args.GetChainTypeString(), "test");
 
+    BOOST_CHECK(test_args.ParseParameters(0, argv_testnet4, error));
+    BOOST_CHECK_EQUAL(test_args.GetChainTypeString(), "main");
+
+    BOOST_CHECK(test_args.ParseParameters(2, argv_testnet4, error));
+    BOOST_CHECK_EQUAL(test_args.GetChainTypeString(), "testnet4");
+
     BOOST_CHECK(test_args.ParseParameters(2, argv_regtest, error));
     BOOST_CHECK_EQUAL(test_args.GetChainTypeString(), "regtest");
 
@@ -758,8 +766,8 @@ struct ArgsMergeTestingSetup : public BasicTestingSetup {
             ForEachNoDup(conf_actions, SET, SECTION_NEGATE, [&] {
                 for (bool soft_set : {false, true}) {
                     for (bool force_set : {false, true}) {
-                        for (const std::string& section : {ChainTypeToString(ChainType::MAIN), ChainTypeToString(ChainType::TESTNET), ChainTypeToString(ChainType::SIGNET)}) {
-                            for (const std::string& network : {ChainTypeToString(ChainType::MAIN), ChainTypeToString(ChainType::TESTNET), ChainTypeToString(ChainType::SIGNET)}) {
+                        for (const std::string& section : {ChainTypeToString(ChainType::MAIN), ChainTypeToString(ChainType::TESTNET), ChainTypeToString(ChainType::TESTNET4), ChainTypeToString(ChainType::SIGNET)}) {
+                            for (const std::string& network : {ChainTypeToString(ChainType::MAIN), ChainTypeToString(ChainType::TESTNET), ChainTypeToString(ChainType::TESTNET4), ChainTypeToString(ChainType::SIGNET)}) {
                                 for (bool net_specific : {false, true}) {
                                     fn(arg_actions, conf_actions, soft_set, force_set, section, network, net_specific);
                                 }
@@ -913,7 +921,7 @@ BOOST_FIXTURE_TEST_CASE(util_ArgsMerge, ArgsMergeTestingSetup)
     // Results file is formatted like:
     //
     //   <input> || <IsArgSet/IsArgNegated/GetArg output> | <GetArgs output> | <GetUnsuitable output>
-    BOOST_CHECK_EQUAL(out_sha_hex, "d1e436c1cd510d0ec44d5205d4b4e3bee6387d316e0075c58206cb16603f3d82");
+    BOOST_CHECK_EQUAL(out_sha_hex, "f1ee5ab094cc43d16a6086fa7f2c10389e0f99902616b31bbf29189972ad1473");
 }
 
 // Similar test as above, but for ArgsManager::GetChainTypeString function.
@@ -1016,7 +1024,7 @@ BOOST_FIXTURE_TEST_CASE(util_ChainMerge, ChainMergeTestingSetup)
     // Results file is formatted like:
     //
     //   <input> || <output>
-    BOOST_CHECK_EQUAL(out_sha_hex, "f263493e300023b6509963887444c41386f44b63bc30047eb8402e8c1144854c");
+    BOOST_CHECK_EQUAL(out_sha_hex, "9e60306e1363528bbc19a47f22bcede88e5d6815212f18ec8e6cdc4638dddab4");
 }
 
 BOOST_AUTO_TEST_CASE(util_ReadWriteSettings)
diff --git a/src/test/pow_tests.cpp b/src/test/pow_tests.cpp
index 9aadebbe63..4af66af283 100644
--- a/src/test/pow_tests.cpp
+++ b/src/test/pow_tests.cpp
@@ -198,6 +198,11 @@ BOOST_AUTO_TEST_CASE(ChainParams_TESTNET_sanity)
     sanity_check_chainparams(*m_node.args, ChainType::TESTNET);
 }
 
+BOOST_AUTO_TEST_CASE(ChainParams_TESTNET4_sanity)
+{
+    sanity_check_chainparams(*m_node.args, ChainType::TESTNET4);
+}
+
 BOOST_AUTO_TEST_CASE(ChainParams_SIGNET_sanity)
 {
     sanity_check_chainparams(*m_node.args, ChainType::SIGNET);
diff --git a/src/test/versionbits_tests.cpp b/src/test/versionbits_tests.cpp
index f462895edb..896840b0f3 100644
--- a/src/test/versionbits_tests.cpp
+++ b/src/test/versionbits_tests.cpp
@@ -419,7 +419,7 @@ BOOST_AUTO_TEST_CASE(versionbits_computeblockversion)
 
     // check that any deployment on any chain can conceivably reach both
     // ACTIVE and FAILED states in roughly the way we expect
-    for (const auto& chain_type: {ChainType::MAIN, ChainType::TESTNET, ChainType::SIGNET, ChainType::REGTEST}) {
+    for (const auto& chain_type: {ChainType::MAIN, ChainType::TESTNET, ChainType::TESTNET4, ChainType::SIGNET, ChainType::REGTEST}) {
         const auto chainParams = CreateChainParams(*m_node.args, chain_type);
         uint32_t chain_all_vbits{0};
         for (int i = 0; i < (int)Consensus::MAX_VERSION_BITS_DEPLOYMENTS; ++i) {
diff --git a/src/util/chaintype.cpp b/src/util/chaintype.cpp
index 8a199e352a..272466e7af 100644
--- a/src/util/chaintype.cpp
+++ b/src/util/chaintype.cpp
@@ -15,6 +15,8 @@ std::string ChainTypeToString(ChainType chain)
         return "main";
     case ChainType::TESTNET:
         return "test";
+    case ChainType::TESTNET4:
+        return "testnet4";
     case ChainType::SIGNET:
         return "signet";
     case ChainType::REGTEST:
@@ -29,6 +31,8 @@ std::optional<ChainType> ChainTypeFromString(std::string_view chain)
         return ChainType::MAIN;
     } else if (chain == "test") {
         return ChainType::TESTNET;
+    } else if (chain == "testnet4") {
+        return ChainType::TESTNET4;
     } else if (chain == "signet") {
         return ChainType::SIGNET;
     } else if (chain == "regtest") {
diff --git a/src/util/chaintype.h b/src/util/chaintype.h
index c73985df57..2fe734b64a 100644
--- a/src/util/chaintype.h
+++ b/src/util/chaintype.h
@@ -13,6 +13,7 @@ enum class ChainType {
     TESTNET,
     SIGNET,
     REGTEST,
+    TESTNET4,
 };
 
 std::string ChainTypeToString(ChainType chain);
diff --git a/test/functional/feature_config_args.py b/test/functional/feature_config_args.py
index dc812d224f..bb20e2baa8 100755
--- a/test/functional/feature_config_args.py
+++ b/test/functional/feature_config_args.py
@@ -371,11 +371,44 @@ class ConfArgsTest(BitcoinTestFramework):
     def test_acceptstalefeeestimates_arg_support(self):
         self.log.info("Test -acceptstalefeeestimates option support")
         conf_file = self.nodes[0].datadir_path / "bitcoin.conf"
-        for chain, chain_name in {("main", ""), ("test", "testnet3"), ("signet", "signet")}:
+        for chain, chain_name in {("main", ""), ("test", "testnet3"), ("signet", "signet"), ("testnet4", "testnet4")}:
             util.write_config(conf_file, n=0, chain=chain_name, extra_config='acceptstalefeeestimates=1\n')
             self.nodes[0].assert_start_raises_init_error(expected_msg=f'Error: acceptstalefeeestimates is not supported on {chain} chain.')
         util.write_config(conf_file, n=0, chain="regtest")  # Reset to regtest
 
+    def test_testnet3_deprecation_msg(self):
+        self.log.info("Test testnet3 deprecation warning")
+        t3_warning_log = "Warning: Support for testnet3 is deprecated and will be removed in an upcoming release. Consider switching to testnet4."
+
+        def warning_msg(node, approx_size):
+            return f'Warning: Disk space for "{node.datadir_path / node.chain / "blocks" }" may not accommodate the block files. Approximately {approx_size} GB of data will be stored in this directory.'
+
+        # Testnet3 node will log the warning
+        self.nodes[0].chain = 'testnet3'
+        self.nodes[0].replace_in_config([('regtest=', 'testnet='), ('[regtest]', '[test]')])
+        with self.nodes[0].assert_debug_log([t3_warning_log]):
+            self.start_node(0)
+        # Some CI environments will have limited space and some others won't
+        # so we need to handle both cases as a valid result.
+        self.nodes[0].stderr.seek(0)
+        err = self.nodes[0].stdout.read()
+        self.nodes[0].stderr.seek(0)
+        self.nodes[0].stderr.truncate()
+        if err != b'' and err != warning_msg(self.nodes[0], 42):
+            raise AssertionError("Unexpected stderr after shutdown of Testnet3 node")
+        self.stop_node(0)
+
+        # Testnet4 node will not log the warning
+        self.nodes[0].chain = 'testnet4'
+        self.nodes[0].replace_in_config([('testnet=', 'testnet4='), ('[test]', '[testnet4]')])
+        with self.nodes[0].assert_debug_log([], unexpected_msgs=[t3_warning_log]):
+            self.start_node(0)
+        self.stop_node(0)
+
+        # Reset to regtest
+        self.nodes[0].chain = 'regtest'
+        self.nodes[0].replace_in_config([('testnet4=', 'regtest='), ('[testnet4]', '[regtest]')])
+
     def run_test(self):
         self.test_log_buffer()
         self.test_args_log()
@@ -389,6 +422,7 @@ class ConfArgsTest(BitcoinTestFramework):
         self.test_ignored_conf()
         self.test_ignored_default_conf()
         self.test_acceptstalefeeestimates_arg_support()
+        self.test_testnet3_deprecation_msg()
 
         # Remove the -datadir argument so it doesn't override the config file
         self.nodes[0].args = [arg for arg in self.nodes[0].args if not arg.startswith("-datadir")]
diff --git a/test/functional/wallet_crosschain.py b/test/functional/wallet_crosschain.py
index 3505d33e51..97db84c3e4 100755
--- a/test/functional/wallet_crosschain.py
+++ b/test/functional/wallet_crosschain.py
@@ -11,7 +11,7 @@ class WalletCrossChain(BitcoinTestFramework):
         self.add_wallet_options(parser)
 
     def set_test_params(self):
-        self.num_nodes = 2
+        self.num_nodes = 3
         self.setup_clean_chain = True
 
     def skip_test_if_missing_module(self):
@@ -24,6 +24,12 @@ class WalletCrossChain(BitcoinTestFramework):
         self.nodes[1].chain = 'testnet3'
         self.nodes[1].extra_args = ['-maxconnections=0', '-prune=550'] # disable testnet sync
         self.nodes[1].replace_in_config([('regtest=', 'testnet='), ('[regtest]', '[test]')])
+
+        # Switch node 2 to testnet4 before starting it.
+        self.nodes[2].chain = 'testnet4'
+        self.nodes[2].extra_args = ['-maxconnections=0', '-prune=550'] # disable testnet4 sync
+        self.nodes[2].replace_in_config([('regtest=', 'testnet4='), ('[regtest]', '[testnet4]')])
+
         self.start_nodes()
 
     def run_test(self):
@@ -39,19 +45,40 @@ class WalletCrossChain(BitcoinTestFramework):
         self.nodes[1].createwallet(node1_wallet)
         self.nodes[1].backupwallet(node1_wallet_backup)
         self.nodes[1].unloadwallet(node1_wallet)
+        node2_wallet = self.nodes[2].datadir_path / 'node2_wallet'
+        node2_wallet_backup = self.nodes[0].datadir_path / 'node2_wallet.bak'
+        self.nodes[2].createwallet(node2_wallet)
+        self.nodes[2].backupwallet(node2_wallet_backup)
+        self.nodes[2].unloadwallet(node2_wallet)
 
         self.log.info("Loading/restoring wallets into nodes with a different genesis block")
 
         if self.options.descriptors:
             assert_raises_rpc_error(-18, 'Wallet file verification failed.', self.nodes[0].loadwallet, node1_wallet)
+            assert_raises_rpc_error(-18, 'Wallet file verification failed.', self.nodes[0].loadwallet, node2_wallet)
             assert_raises_rpc_error(-18, 'Wallet file verification failed.', self.nodes[1].loadwallet, node0_wallet)
+            assert_raises_rpc_error(-18, 'Wallet file verification failed.', self.nodes[2].loadwallet, node0_wallet)
+            assert_raises_rpc_error(-18, 'Wallet file verification failed.', self.nodes[1].loadwallet, node2_wallet)
+            assert_raises_rpc_error(-18, 'Wallet file verification failed.', self.nodes[2].loadwallet, node1_wallet)
             assert_raises_rpc_error(-18, 'Wallet file verification failed.', self.nodes[0].restorewallet, 'w', node1_wallet_backup)
+            assert_raises_rpc_error(-18, 'Wallet file verification failed.', self.nodes[0].restorewallet, 'w', node2_wallet_backup)
             assert_raises_rpc_error(-18, 'Wallet file verification failed.', self.nodes[1].restorewallet, 'w', node0_wallet_backup)
+            assert_raises_rpc_error(-18, 'Wallet file verification failed.', self.nodes[2].restorewallet, 'w', node0_wallet_backup)
+            assert_raises_rpc_error(-18, 'Wallet file verification failed.', self.nodes[1].restorewallet, 'w', node2_wallet_backup)
+            assert_raises_rpc_error(-18, 'Wallet file verification failed.', self.nodes[2].restorewallet, 'w', node1_wallet_backup)
         else:
             assert_raises_rpc_error(-4, 'Wallet files should not be reused across chains.', self.nodes[0].loadwallet, node1_wallet)
+            assert_raises_rpc_error(-4, 'Wallet files should not be reused across chains.', self.nodes[0].loadwallet, node2_wallet)
             assert_raises_rpc_error(-4, 'Wallet files should not be reused across chains.', self.nodes[1].loadwallet, node0_wallet)
+            assert_raises_rpc_error(-4, 'Wallet files should not be reused across chains.', self.nodes[2].loadwallet, node0_wallet)
+            assert_raises_rpc_error(-4, 'Wallet files should not be reused across chains.', self.nodes[1].loadwallet, node2_wallet)
+            assert_raises_rpc_error(-4, 'Wallet files should not be reused across chains.', self.nodes[2].loadwallet, node1_wallet)
             assert_raises_rpc_error(-4, 'Wallet files should not be reused across chains.', self.nodes[0].restorewallet, 'w', node1_wallet_backup)
+            assert_raises_rpc_error(-4, 'Wallet files should not be reused across chains.', self.nodes[0].restorewallet, 'w', node2_wallet_backup)
             assert_raises_rpc_error(-4, 'Wallet files should not be reused across chains.', self.nodes[1].restorewallet, 'w', node0_wallet_backup)
+            assert_raises_rpc_error(-4, 'Wallet files should not be reused across chains.', self.nodes[2].restorewallet, 'w', node0_wallet_backup)
+            assert_raises_rpc_error(-4, 'Wallet files should not be reused across chains.', self.nodes[1].restorewallet, 'w', node2_wallet_backup)
+            assert_raises_rpc_error(-4, 'Wallet files should not be reused across chains.', self.nodes[2].restorewallet, 'w', node1_wallet_backup)
 
         if not self.options.descriptors:
             self.log.info("Override cross-chain wallet load protection")