diff --git a/common/heights.go b/common/heights.go
index a5c1c418..2ce6639c 100644
--- a/common/heights.go
+++ b/common/heights.go
@@ -34,7 +34,10 @@ const HeightSupportThetaTokenInSmartContract uint64 = 13123789 // approximate ti
 const HeightValidatorStakeChangedTo200K uint64 = 14526120 // approximate time: 12pm Mar 14, 2022 PT
 
 // HeightSupportWrappedTheta specifies the block height to support wrapped Theta
-const HeightSupportWrappedTheta uint64 = 1000000000
+const HeightSupportWrappedTheta uint64 = 17285755 // approximate time: 7pm Sep 28, 2022 PT
+
+// HeightEnableMetachainSupport specifies the block height to enable Theta Metachain support (i.e. Mainnet 4.0)
+const HeightEnableMetachainSupport uint64 = 1000000000
 
 // CheckpointInterval defines the interval between checkpoints.
 const CheckpointInterval = int64(100)
diff --git a/common/result/error_code.go b/common/result/error_code.go
index c579adb4..a0596e4d 100644
--- a/common/result/error_code.go
+++ b/common/result/error_code.go
@@ -5,6 +5,8 @@ type ErrorCode int
 const (
 	CodeOK ErrorCode = 0
 
+	CodeUndecided ErrorCode = 2
+
 	// Common Errors
 	CodeGenericError             ErrorCode = 100000
 	CodeInvalidSignature         ErrorCode = 100001
@@ -29,11 +31,12 @@ const (
 	CodeUnauthorizedToUpdateSplitRule ErrorCode = 104001
 
 	// SmartContract Errors
-	CodeEVMError               ErrorCode = 105001
-	CodeInvalidValueToTransfer ErrorCode = 105002
-	CodeInvalidGasPrice        ErrorCode = 105003
-	CodeFeeLimitTooHigh        ErrorCode = 105004
-	CodeInvalidGasLimit        ErrorCode = 105005
+	CodeEVMError                          ErrorCode = 105001
+	CodeInvalidValueToTransfer            ErrorCode = 105002
+	CodeInvalidGasPrice                   ErrorCode = 105003
+	CodeFeeLimitTooHigh                   ErrorCode = 105004
+	CodeInvalidGasLimit                   ErrorCode = 105005
+	CodeDoNotSupportNativeThetaInSubchain ErrorCode = 105006
 
 	// Stake Deposit/Withdrawal Errors
 	CodeInvalidStakePurpose     ErrorCode = 106001
diff --git a/common/result/result.go b/common/result/result.go
index 20acd550..27baa030 100644
--- a/common/result/result.go
+++ b/common/result/result.go
@@ -16,6 +16,11 @@ func (res Result) IsOK() bool {
 	return res.Code == CodeOK
 }
 
+// IsUndecided indicates if the execution succeeded
+func (res Result) IsUndecided() bool {
+	return res.Code == CodeUndecided
+}
+
 // IsError indicates if the execution results in an error
 func (res Result) IsError() bool {
 	return res.Code != CodeOK
@@ -58,6 +63,18 @@ func OKWith(info Info) Result {
 	return res
 }
 
+// UndecidedWith returns a success result with extra information
+func UndecidedWith(info Info) Result {
+	res := Result{
+		Code: CodeUndecided,
+		Info: make(Info),
+	}
+	for k, v := range info {
+		res.Info[k] = v
+	}
+	return res
+}
+
 // Error returns an error result
 func Error(msgFormat string, a ...interface{}) Result {
 	msg := fmt.Sprintf(msgFormat, a...)
diff --git a/common/size.go b/common/size.go
new file mode 100644
index 00000000..097b6304
--- /dev/null
+++ b/common/size.go
@@ -0,0 +1,56 @@
+// Copyright 2014 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+package common
+
+import (
+	"fmt"
+)
+
+// StorageSize is a wrapper around a float value that supports user friendly
+// formatting.
+type StorageSize float64
+
+// String implements the stringer interface.
+func (s StorageSize) String() string {
+	if s > 1099511627776 {
+		return fmt.Sprintf("%.2f TiB", s/1099511627776)
+	} else if s > 1073741824 {
+		return fmt.Sprintf("%.2f GiB", s/1073741824)
+	} else if s > 1048576 {
+		return fmt.Sprintf("%.2f MiB", s/1048576)
+	} else if s > 1024 {
+		return fmt.Sprintf("%.2f KiB", s/1024)
+	} else {
+		return fmt.Sprintf("%.2f B", s)
+	}
+}
+
+// TerminalString implements log.TerminalStringer, formatting a string for console
+// output during logging.
+func (s StorageSize) TerminalString() string {
+	if s > 1099511627776 {
+		return fmt.Sprintf("%.2fTiB", s/1099511627776)
+	} else if s > 1073741824 {
+		return fmt.Sprintf("%.2fGiB", s/1073741824)
+	} else if s > 1048576 {
+		return fmt.Sprintf("%.2fMiB", s/1048576)
+	} else if s > 1024 {
+		return fmt.Sprintf("%.2fKiB", s/1024)
+	} else {
+		return fmt.Sprintf("%.2fB", s)
+	}
+}
diff --git a/core/genesis.go b/core/genesis.go
index fb02b44f..1ec9196c 100644
--- a/core/genesis.go
+++ b/core/genesis.go
@@ -6,4 +6,8 @@ const (
 	MainnetGenesisBlockHash = "0xd8836c6cf3c3ccea0b015b4ed0f9efb0ffe6254db793a515843c9d0f68cbab65"
 
 	GenesisBlockHeight = uint64(0)
+
+	SubchainChainIDPrefix = "tsub"
+
+	MinSubchainID = 1000
 )
diff --git a/ledger/execution/tx_smart_contract.go b/ledger/execution/tx_smart_contract.go
index 6a394712..09cb7624 100644
--- a/ledger/execution/tx_smart_contract.go
+++ b/ledger/execution/tx_smart_contract.go
@@ -161,7 +161,9 @@ func (exec *SmartContractTxExecutor) process(chainID string, view *st.StoreView,
 	// Note: for contract deployment, vm.Execute() might transfer coins from the fromAccount to the
 	//       deployed smart contract. Thus, we should call vm.Execute() before calling getInput().
 	//       Otherwise, the fromAccount returned by getInput() will have incorrect balance.
-	evmRet, contractAddr, gasUsed, evmErr := vm.Execute(exec.state.ParentBlock(), tx, view)
+	pb := exec.state.ParentBlock()
+	parentBlockInfo := vm.NewBlockInfo(pb.Height, pb.Timestamp, pb.ChainID)
+	evmRet, contractAddr, gasUsed, evmErr := vm.Execute(parentBlockInfo, tx, view)
 
 	fromAddress := tx.From.Address
 	fromAccount, success := getInput(view, tx.From)
diff --git a/ledger/types/tx.go b/ledger/types/tx.go
index 790ff0e9..4bc8e5dd 100644
--- a/ledger/types/tx.go
+++ b/ledger/types/tx.go
@@ -5,6 +5,8 @@ import (
 	"encoding/json"
 	"fmt"
 	"math/big"
+	"strconv"
+	"strings"
 	"sync"
 
 	log "github.com/sirupsen/logrus"
@@ -1101,7 +1103,20 @@ func MapChainID(chainIDStr string, blockHeight uint64) *big.Int {
 
 	// For replay attack protection, should NOT use the same chainID as Ethereum
 	chainID := big.NewInt(1).Add(big.NewInt(CHAIN_ID_OFFSET), chainIDWithoutOffset)
-	return chainID
+
+	if blockHeight < common.HeightEnableMetachainSupport {
+		return chainID
+	} else {
+		// attempt to extract the IDs for subchains. ChainID in the form of tsub[1-9][0-9]* is considered as a Theta Subchain
+		subchainID, err := extractSubchainID(chainIDStr) // no need to add offset to the subchainIDs
+		if err == nil {
+			// this is a subchain chainID
+			return subchainID
+		} else {
+			// fallback
+			return chainID
+		}
+	}
 }
 
 func mapChainIDWithoutOffset(chainIDStr string) *big.Int {
@@ -1120,3 +1135,32 @@ func mapChainIDWithoutOffset(chainIDStr string) *big.Int {
 	chainIDBigInt := new(big.Int).Abs(crypto.Keccak256Hash(common.Bytes(chainIDStr)).Big()) // all other chainIDs
 	return chainIDBigInt
 }
+
+// Subchain chainID should have the form tsub[1-9][0-9]*
+func extractSubchainID(chainIDStr string) (*big.Int, error) {
+	if !strings.HasPrefix(chainIDStr, core.SubchainChainIDPrefix) {
+		return nil, fmt.Errorf("invalid subchain ID prefix: %v", chainIDStr)
+	}
+
+	if len(chainIDStr) < 5 {
+		return nil, fmt.Errorf("subchain ID too short: %v", chainIDStr)
+	}
+
+	leadingDigit := chainIDStr[4]
+	if leadingDigit == byte('0') {
+		return nil, fmt.Errorf("the leading digit of the subchain ID should not be zero: %v", chainIDStr)
+	}
+
+	chainIDIntStr := chainIDStr[4:]
+	chainID, err := strconv.Atoi(chainIDIntStr)
+	if err != nil {
+		return nil, err
+	}
+
+	// we require subchain ID to be at least core.MinSubchainID, so it doesn't overlap with the ID of the mainchain
+	if chainID < core.MinSubchainID {
+		return nil, fmt.Errorf("subchain ID too small: %v", chainIDStr)
+	}
+
+	return big.NewInt(int64(chainID)), nil
+}
diff --git a/ledger/types/tx_test.go b/ledger/types/tx_test.go
index 4a6508d2..412f6257 100644
--- a/ledger/types/tx_test.go
+++ b/ledger/types/tx_test.go
@@ -18,6 +18,103 @@ import (
 
 var chainID string = "test_chain"
 
+func TestChainID(t *testing.T) {
+
+	//
+	// The IDs for the main chains
+	//
+
+	chainIDStrMainnet := "mainnet"
+	chainIDStr := chainIDStrMainnet
+	chainID := MapChainID(chainIDStr, common.HeightRPCCompatibility+1)
+	assert.True(t, chainID.Cmp(big.NewInt(361)) == 0, "mapped chainID for %v is %v", chainIDStr, chainID)
+	fmt.Printf("extracted chainID for %v: %v\n", chainIDStr, chainID)
+
+	chainIDStrTestnet := "testnet"
+	chainIDStr = chainIDStrTestnet
+	chainID = MapChainID(chainIDStr, common.HeightRPCCompatibility+1)
+	assert.True(t, chainID.Cmp(big.NewInt(365)) == 0, "mapped chainID for %v is %v", chainIDStr, chainID)
+	fmt.Printf("extracted chainID for %v: %v\n", chainIDStr, chainID)
+
+	chainIDStrPrivatenet := "privatenet"
+	chainIDStr = chainIDStrPrivatenet
+	chainID = MapChainID(chainIDStr, common.HeightRPCCompatibility+1)
+	assert.True(t, chainID.Cmp(big.NewInt(366)) == 0, "mapped chainID for %v is %v", chainIDStr, chainID)
+	fmt.Printf("extracted chainID for %v: %v\n", chainIDStr, chainID)
+
+	//
+	// Invalid subchain IDs
+	//
+
+	var err error
+	invalidSubchainID0 := "tsub_881" // with an extra underscore
+	chainIDStr = invalidSubchainID0
+	chainID, err = extractSubchainID(chainIDStr)
+	assert.True(t, err != nil, "should be an invalid subchain ID: %v", chainIDStr)
+	chainID = MapChainID(chainIDStr, common.HeightEnableMetachainSupport+1)
+	assert.True(t, chainID.Cmp(big.NewInt(881)) != 0, "mapped chainID for %v is %v", chainIDStr, chainID)
+	fmt.Printf("extracted chainID for %v: %v\n", chainIDStr, chainID)
+
+	invalidSubchainID1 := "ts881"
+	chainIDStr = invalidSubchainID1
+	chainID, err = extractSubchainID(chainIDStr)
+	assert.True(t, err != nil, "should be an invalid subchain ID: %v", chainIDStr)
+	chainID = MapChainID(chainIDStr, common.HeightEnableMetachainSupport+1)
+	assert.True(t, chainID.Cmp(big.NewInt(881)) != 0, "mapped chainID for %v is %v", chainIDStr, chainID)
+	fmt.Printf("extracted chainID for %v: %v\n", chainIDStr, chainID)
+
+	invalidSubchainID2 := "tsub09998" // leading digit should not be 0
+	chainIDStr = invalidSubchainID2
+	chainID, err = extractSubchainID(chainIDStr)
+	assert.True(t, err != nil, "should be an invalid subchain ID: %v", chainIDStr)
+	chainID = MapChainID(chainIDStr, common.HeightEnableMetachainSupport+1)
+	assert.True(t, chainID.Cmp(big.NewInt(9998)) != 0, "mapped chainID for %v is %v", chainIDStr, chainID)
+	fmt.Printf("extracted chainID for %v: %v\n", chainIDStr, chainID)
+
+	invalidSubchainID3 := "tsubabc9" // hex not allowed in chainID
+	chainIDStr = invalidSubchainID3
+	chainID, err = extractSubchainID(chainIDStr)
+	assert.True(t, err != nil, "should be an invalid subchain ID: %v", chainIDStr)
+	chainID = MapChainID(chainIDStr, common.HeightEnableMetachainSupport+1)
+	assert.True(t, chainID.Cmp(big.NewInt(43977)) != 0, "mapped chainID for %v is %v", chainIDStr, chainID)
+	fmt.Printf("extracted chainID for %v: %v\n", chainIDStr, chainID)
+
+	invalidSubchainID4 := "tsub999" // subchain ID needs to be at least 1000
+	chainIDStr = invalidSubchainID4
+	chainID, err = extractSubchainID(chainIDStr)
+	assert.True(t, err != nil, "should be an invalid subchain ID: %v", chainIDStr)
+	chainID = MapChainID(chainIDStr, common.HeightEnableMetachainSupport+1)
+	assert.True(t, chainID.Cmp(big.NewInt(999)) != 0, "mapped chainID for %v is %v", chainIDStr, chainID)
+	fmt.Printf("extracted chainID for %v: %v\n", chainIDStr, chainID)
+
+	invalidSubchainID5 := "tsub34535873957238957239573985728957283957923528357238572893572983457238957238495893" // subchain ID needs to be smaller than uint64.max
+	chainIDStr = invalidSubchainID5
+	chainID, err = extractSubchainID(chainIDStr)
+	assert.True(t, err != nil, "should be an invalid subchain ID: %v", chainIDStr)
+	chainID = MapChainID(chainIDStr, common.HeightEnableMetachainSupport+1)
+	cid, _ := big.NewInt(0).SetString("34535873957238957239573985728957283957923528357238572893572983457238957238495893", 10)
+	assert.True(t, chainID.Cmp(cid) != 0, "mapped chainID for %v is %v", chainIDStr, chainID)
+	fmt.Printf("extracted chainID for %v: %v\n", chainIDStr, chainID)
+
+	//
+	// Valid subchain IDs
+	//
+
+	validSubchainID1 := "tsub1991"
+	chainIDStr = validSubchainID1
+	chainID = MapChainID(chainIDStr, common.HeightEnableMetachainSupport+1)
+	assert.True(t, chainID.Cmp(big.NewInt(1991)) == 0, "mapped chainID for %v is %v", chainIDStr, chainID)
+	fmt.Printf("extracted chainID for %v: %v\n", chainIDStr, chainID)
+
+	validSubchainID2 := "tsub4546325235"
+	chainIDStr = validSubchainID2
+	chainID = MapChainID(chainIDStr, common.HeightEnableMetachainSupport+1)
+	assert.True(t, chainID.Cmp(big.NewInt(4546325235)) == 0, "mapped chainID for %v is %v", chainIDStr, chainID)
+	fmt.Printf("extracted chainID for %v: %v\n", chainIDStr, chainID)
+
+	// assert.True(t, false)
+}
+
 func TestCoinbaseTxSignable(t *testing.T) {
 	chainID := "test_chain_id"
 	va1PrivAcc := PrivAccountFromSecret("validator1")
diff --git a/ledger/vm/exec.go b/ledger/vm/exec.go
index 4e5163a7..31339d3f 100644
--- a/ledger/vm/exec.go
+++ b/ledger/vm/exec.go
@@ -5,14 +5,26 @@ import (
 	"math/big"
 
 	"github.com/thetatoken/theta/common"
-	"github.com/thetatoken/theta/core"
-	"github.com/thetatoken/theta/ledger/state"
 	"github.com/thetatoken/theta/ledger/types"
 	"github.com/thetatoken/theta/ledger/vm/params"
 )
 
+type BlockInfo struct {
+	Height    uint64
+	Timestamp *big.Int
+	ChainID   string
+}
+
+func NewBlockInfo(height uint64, timestamp *big.Int, chainID string) *BlockInfo {
+	return &BlockInfo{
+		Height:    height,
+		Timestamp: timestamp,
+		ChainID:   chainID,
+	}
+}
+
 // Execute executes the given smart contract
-func Execute(parentBlock *core.Block, tx *types.SmartContractTx, storeView *state.StoreView) (evmRet common.Bytes,
+func Execute(parentBlockInfo *BlockInfo, tx *types.SmartContractTx, statedb StateDB) (evmRet common.Bytes,
 	contractAddr common.Address, gasUsed uint64, evmErr error) {
 	context := Context{
 		CanTransfer: CanTransfer,
@@ -20,16 +32,16 @@ func Execute(parentBlock *core.Block, tx *types.SmartContractTx, storeView *stat
 		Origin:      tx.From.Address,
 		GasPrice:    tx.GasPrice,
 		GasLimit:    tx.GasLimit,
-		BlockNumber: new(big.Int).SetUint64(parentBlock.Height + 1),
-		Time:        parentBlock.Timestamp,
+		BlockNumber: new(big.Int).SetUint64(parentBlockInfo.Height + 1),
+		Time:        parentBlockInfo.Timestamp,
 		Difficulty:  new(big.Int).SetInt64(0),
 	}
-	chainIDBigInt := types.MapChainID(parentBlock.ChainID, context.BlockNumber.Uint64())
+	chainIDBigInt := types.MapChainID(parentBlockInfo.ChainID, context.BlockNumber.Uint64())
 	chainConfig := &params.ChainConfig{
 		ChainID: chainIDBigInt,
 	}
 	config := Config{}
-	evm := NewEVM(context, storeView, chainConfig, config)
+	evm := NewEVM(context, statedb, chainConfig, config)
 
 	value := tx.From.Coins.TFuelWei
 	if value == nil {
@@ -49,7 +61,10 @@ func Execute(parentBlock *core.Block, tx *types.SmartContractTx, storeView *stat
 	// if gasLimit > maxGasLimit {
 	// 	return common.Bytes{}, common.Address{}, 0, ErrInvalidGasLimit
 	// }
-	blockHeight := storeView.Height() + 1
+
+	// blockHeight := storeView.Height() + 1
+	blockHeight := statedb.GetBlockHeight() // GetBlockHeight() returns storeView.Height() + 1 so it is equivalent to the above commented line
+
 	maxGasLimit := types.GetMaxGasLimit(blockHeight)
 	if new(big.Int).SetUint64(gasLimit).Cmp(maxGasLimit) > 0 {
 		return common.Bytes{}, common.Address{}, 0, ErrInvalidGasLimit
diff --git a/ledger/vm/params/protocol_params.go b/ledger/vm/params/protocol_params.go
index 9c860578..af0fa387 100644
--- a/ledger/vm/params/protocol_params.go
+++ b/ledger/vm/params/protocol_params.go
@@ -69,7 +69,8 @@ const (
 	MemoryGas        uint64 = 3     // Times the address of the (highest referenced byte in memory + 1). NOTE: referencing happens on read, write and in instructions such as RETURN and CALL.
 	TxDataNonZeroGas uint64 = 68    // Per byte of data attached to a transaction that is not equal to zero. NOTE: Not payable on data of calls between transactions.
 
-	MaxCodeSize = 24576 // Maximum bytecode to permit for a contract
+	MaxCodeSize             = 24576 // Maximum bytecode to permit for a contract
+	MaxCodeSizeForMetachain = 49152 // Maximum bytecode to permit for a contract
 
 	// Precompiled contract gas prices
 
diff --git a/ledger/vm/vm.go b/ledger/vm/vm.go
index 913565aa..47d28cf9 100644
--- a/ledger/vm/vm.go
+++ b/ledger/vm/vm.go
@@ -624,7 +624,12 @@ func (evm *EVM) create(caller ContractRef, codeAndHash *codeAndHash, gas uint64,
 	ret, err := run(evm, contract, nil, false)
 
 	// check whether the max code size has been exceeded
-	maxCodeSizeExceeded := len(ret) > params.MaxCodeSize
+	maxCodeSize := params.MaxCodeSize
+	if blockHeight >= common.HeightEnableMetachainSupport {
+		maxCodeSize = params.MaxCodeSizeForMetachain
+	}
+
+	maxCodeSizeExceeded := len(ret) > maxCodeSize
 	// if the contract creation ran successfully and no errors were returned
 	// calculate the gas required to store the code. If the code could not
 	// be stored due to not enough gas set an error and let it be handled
diff --git a/rpc/call.go b/rpc/call.go
index 08d806b3..32739faa 100644
--- a/rpc/call.go
+++ b/rpc/call.go
@@ -52,8 +52,9 @@ func (t *ThetaRPCService) CallSmartContract(args *CallSmartContractArgs, result
 		return fmt.Errorf("Failed to parse SmartContractTx: %v", args.SctxBytes)
 	}
 
-	parentBlock := t.ledger.State().ParentBlock()
-	vmRet, contractAddr, gasUsed, vmErr := vm.Execute(parentBlock, sctx, ledgerState)
+	pb := t.ledger.State().ParentBlock()
+	parentBlockInfo := vm.NewBlockInfo(pb.Height, pb.Timestamp, pb.ChainID)
+	vmRet, contractAddr, gasUsed, vmErr := vm.Execute(parentBlockInfo, sctx, ledgerState)
 	ledgerState.Save()
 
 	result.VmReturn = hex.EncodeToString(vmRet)
diff --git a/version/version_number.txt b/version/version_number.txt
index 18091983..0c89fc92 100644
--- a/version/version_number.txt
+++ b/version/version_number.txt
@@ -1 +1 @@
-3.4.0
+4.0.0
\ No newline at end of file