diff --git a/packages/testing/src/execution_testing/forks/base_fork.py b/packages/testing/src/execution_testing/forks/base_fork.py
index 30fe2fee5b3..f842878c42f 100644
--- a/packages/testing/src/execution_testing/forks/base_fork.py
+++ b/packages/testing/src/execution_testing/forks/base_fork.py
@@ -431,6 +431,15 @@ def __init_subclass__(
         if base_fork_class != BaseFork:
             base_fork_class._children.add(cls)
             cls._enabled_eips |= base_fork_class._enabled_eips
+        # A fork inheriting from more than one fork enables the union of
+        # their EIPs; the first base alone leads the lineage above.
+        for base_class in cls.__bases__:
+            if (
+                issubclass(base_class, BaseFork)
+                and not base_class.is_eip()
+                and base_class is not BaseFork
+            ):
+                cls._enabled_eips |= base_class._enabled_eips
         eip_bases = [
             base_class
             for base_class in cls.__bases__
diff --git a/src/ethereum/forks/monad_eight/exceptions.py b/src/ethereum/forks/monad_eight/exceptions.py
index e74948cb59a..e11cf09929b 100644
--- a/src/ethereum/forks/monad_eight/exceptions.py
+++ b/src/ethereum/forks/monad_eight/exceptions.py
@@ -4,7 +4,7 @@
 
 from typing import TYPE_CHECKING, Final
 
-from ethereum_types.numeric import Uint
+from ethereum_types.numeric import U64, Uint
 
 from ethereum.exceptions import InvalidTransaction
 
@@ -12,6 +12,20 @@
     from .transactions import Transaction
 
 
+class WrongChainIdError(InvalidTransaction):
+    """
+    Chain identifier from a transaction does not match the executing chain. See
+    [EIP-155].
+
+    [EIP-155]: https://eips.ethereum.org/EIPS/eip-155
+    """
+
+    def __init__(self, expected: U64, actual: U64):
+        super().__init__(f"expected chain_id `{expected}` but got `{actual}`")
+        self.expected = expected
+        self.actual = actual
+
+
 class TransactionTypeError(InvalidTransaction):
     """
     Unknown [EIP-2718] transaction type byte.
diff --git a/src/ethereum/forks/monad_eight/fork.py b/src/ethereum/forks/monad_eight/fork.py
index 82e4b0d06d2..0f02c0d8c28 100644
--- a/src/ethereum/forks/monad_eight/fork.py
+++ b/src/ethereum/forks/monad_eight/fork.py
@@ -43,6 +43,7 @@
     NoBlobDataError,
     PriorityFeeGreaterThanMaxFeeError,
     TransactionTypeContractCreationError,
+    WrongChainIdError,
 )
 from .fork_types import Authorization, VersionedHash
 from .requests import (
@@ -72,6 +73,7 @@
     LegacyTransaction,
     SetCodeTransaction,
     Transaction,
+    chain_id,
     decode_transaction,
     encode_transaction,
     get_transaction_hash,
@@ -467,7 +469,14 @@ def check_transaction(
     if tx_blob_gas_used > blob_gas_available:
         raise BlobGasLimitExceededError("blob gas limit exceeded")
 
-    sender_address = recover_sender(block_env.chain_id, tx)
+    tx_chain_id = chain_id(tx)
+    if tx_chain_id is not None and tx_chain_id != block_env.chain_id:
+        raise WrongChainIdError(
+            expected=block_env.chain_id,
+            actual=tx_chain_id,
+        )
+
+    sender_address = recover_sender(tx)
     sender_account = get_account(tx_state, sender_address)
 
     if isinstance(
diff --git a/src/ethereum/forks/monad_eight/transactions.py b/src/ethereum/forks/monad_eight/transactions.py
index 04c4b77388c..24bb4880a74 100644
--- a/src/ethereum/forks/monad_eight/transactions.py
+++ b/src/ethereum/forks/monad_eight/transactions.py
@@ -625,7 +625,25 @@ def calculate_intrinsic_cost(tx: Transaction) -> Tuple[Uint, Uint]:
     )
 
 
-def recover_sender(chain_id: U64, tx: Transaction) -> Address:
+def chain_id(tx: Transaction) -> None | U64:
+    """
+    Extract the chain identifier from a transaction. See [EIP-155].
+
+    [EIP-155]: https://eips.ethereum.org/EIPS/eip-155
+    """
+    if isinstance(tx, LegacyTransaction):
+        if tx.v == 27 or tx.v == 28:
+            return None
+
+        if tx.v < U256(35):
+            raise InvalidSignatureError("bad v")
+
+        return U64((tx.v - U256(35)) >> U256(1))
+    else:
+        return tx.chain_id
+
+
+def recover_sender(tx: Transaction) -> Address:
     """
     Extracts the sender address from a transaction.
 
@@ -635,9 +653,9 @@ def recover_sender(chain_id: U64, tx: Transaction) -> Address:
     signing hash of the transaction. The sender's public key can be obtained
     with these two values and therefore the sender address can be retrieved.
 
-    This function takes chain_id and a transaction as parameters and returns
-    the address of the sender of the transaction. It raises an
-    `InvalidSignatureError` if the signature values (r, s, v) are invalid.
+    This function takes a transaction as a parameter and returns the address
+    of the sender of the transaction. It raises an `InvalidSignatureError` if
+    the signature values (r, s, v) are invalid.
     """
     r, s = tx.r, tx.s
     if U256(0) >= r or r >= SECP256K1N:
@@ -652,14 +670,14 @@ def recover_sender(chain_id: U64, tx: Transaction) -> Address:
                 r, s, v - U256(27), signing_hash_pre155(tx)
             )
         else:
-            chain_id_x2 = U256(chain_id) * U256(2)
-            if v != U256(35) + chain_id_x2 and v != U256(36) + chain_id_x2:
-                raise InvalidSignatureError("bad v")
+            assert v >= U256(35), "call chain_id before recover_sender"
+            tx_chain_id = U64((v - U256(35)) >> U256(1))
+            v = (v - U256(35)) & U256(1)
             public_key = secp256k1_recover(
                 r,
                 s,
-                v - U256(35) - chain_id_x2,
-                signing_hash_155(tx, chain_id),
+                v,
+                signing_hash_155(tx, tx_chain_id),
             )
     elif isinstance(tx, AccessListTransaction):
         if tx.y_parity not in (U256(0), U256(1)):
diff --git a/src/ethereum/forks/monad_next/exceptions.py b/src/ethereum/forks/monad_next/exceptions.py
index 3074a1f738f..8d409eaaa02 100644
--- a/src/ethereum/forks/monad_next/exceptions.py
+++ b/src/ethereum/forks/monad_next/exceptions.py
@@ -4,7 +4,7 @@
 
 from typing import TYPE_CHECKING, Final
 
-from ethereum_types.numeric import Uint
+from ethereum_types.numeric import U64, Uint
 
 from ethereum.exceptions import InvalidTransaction
 
@@ -12,6 +12,20 @@
     from .transactions import Transaction
 
 
+class WrongChainIdError(InvalidTransaction):
+    """
+    Chain identifier from a transaction does not match the executing chain. See
+    [EIP-155].
+
+    [EIP-155]: https://eips.ethereum.org/EIPS/eip-155
+    """
+
+    def __init__(self, expected: U64, actual: U64):
+        super().__init__(f"expected chain_id `{expected}` but got `{actual}`")
+        self.expected = expected
+        self.actual = actual
+
+
 class TransactionTypeError(InvalidTransaction):
     """
     Unknown [EIP-2718] transaction type byte.
diff --git a/src/ethereum/forks/monad_next/fork.py b/src/ethereum/forks/monad_next/fork.py
index d743f1169a3..653f05d030f 100644
--- a/src/ethereum/forks/monad_next/fork.py
+++ b/src/ethereum/forks/monad_next/fork.py
@@ -47,6 +47,7 @@
     NoBlobDataError,
     PriorityFeeGreaterThanMaxFeeError,
     TransactionTypeContractCreationError,
+    WrongChainIdError,
 )
 from .fork_types import Authorization, VersionedHash
 from .requests import (
@@ -76,6 +77,7 @@
     LegacyTransaction,
     SetCodeTransaction,
     Transaction,
+    chain_id,
     decode_transaction,
     encode_transaction,
     get_transaction_hash,
@@ -482,7 +484,14 @@ def check_transaction(
     if tx_blob_gas_used > blob_gas_available:
         raise BlobGasLimitExceededError("blob gas limit exceeded")
 
-    sender_address = recover_sender(block_env.chain_id, tx)
+    tx_chain_id = chain_id(tx)
+    if tx_chain_id is not None and tx_chain_id != block_env.chain_id:
+        raise WrongChainIdError(
+            expected=block_env.chain_id,
+            actual=tx_chain_id,
+        )
+
+    sender_address = recover_sender(tx)
     sender_account = get_account(tx_state, sender_address)
 
     if isinstance(
diff --git a/src/ethereum/forks/monad_next/transactions.py b/src/ethereum/forks/monad_next/transactions.py
index 04c4b77388c..24bb4880a74 100644
--- a/src/ethereum/forks/monad_next/transactions.py
+++ b/src/ethereum/forks/monad_next/transactions.py
@@ -625,7 +625,25 @@ def calculate_intrinsic_cost(tx: Transaction) -> Tuple[Uint, Uint]:
     )
 
 
-def recover_sender(chain_id: U64, tx: Transaction) -> Address:
+def chain_id(tx: Transaction) -> None | U64:
+    """
+    Extract the chain identifier from a transaction. See [EIP-155].
+
+    [EIP-155]: https://eips.ethereum.org/EIPS/eip-155
+    """
+    if isinstance(tx, LegacyTransaction):
+        if tx.v == 27 or tx.v == 28:
+            return None
+
+        if tx.v < U256(35):
+            raise InvalidSignatureError("bad v")
+
+        return U64((tx.v - U256(35)) >> U256(1))
+    else:
+        return tx.chain_id
+
+
+def recover_sender(tx: Transaction) -> Address:
     """
     Extracts the sender address from a transaction.
 
@@ -635,9 +653,9 @@ def recover_sender(chain_id: U64, tx: Transaction) -> Address:
     signing hash of the transaction. The sender's public key can be obtained
     with these two values and therefore the sender address can be retrieved.
 
-    This function takes chain_id and a transaction as parameters and returns
-    the address of the sender of the transaction. It raises an
-    `InvalidSignatureError` if the signature values (r, s, v) are invalid.
+    This function takes a transaction as a parameter and returns the address
+    of the sender of the transaction. It raises an `InvalidSignatureError` if
+    the signature values (r, s, v) are invalid.
     """
     r, s = tx.r, tx.s
     if U256(0) >= r or r >= SECP256K1N:
@@ -652,14 +670,14 @@ def recover_sender(chain_id: U64, tx: Transaction) -> Address:
                 r, s, v - U256(27), signing_hash_pre155(tx)
             )
         else:
-            chain_id_x2 = U256(chain_id) * U256(2)
-            if v != U256(35) + chain_id_x2 and v != U256(36) + chain_id_x2:
-                raise InvalidSignatureError("bad v")
+            assert v >= U256(35), "call chain_id before recover_sender"
+            tx_chain_id = U64((v - U256(35)) >> U256(1))
+            v = (v - U256(35)) & U256(1)
             public_key = secp256k1_recover(
                 r,
                 s,
-                v - U256(35) - chain_id_x2,
-                signing_hash_155(tx, chain_id),
+                v,
+                signing_hash_155(tx, tx_chain_id),
             )
     elif isinstance(tx, AccessListTransaction):
         if tx.y_parity not in (U256(0), U256(1)):
diff --git a/src/ethereum/forks/monad_nine/exceptions.py b/src/ethereum/forks/monad_nine/exceptions.py
index 3074a1f738f..8d409eaaa02 100644
--- a/src/ethereum/forks/monad_nine/exceptions.py
+++ b/src/ethereum/forks/monad_nine/exceptions.py
@@ -4,7 +4,7 @@
 
 from typing import TYPE_CHECKING, Final
 
-from ethereum_types.numeric import Uint
+from ethereum_types.numeric import U64, Uint
 
 from ethereum.exceptions import InvalidTransaction
 
@@ -12,6 +12,20 @@
     from .transactions import Transaction
 
 
+class WrongChainIdError(InvalidTransaction):
+    """
+    Chain identifier from a transaction does not match the executing chain. See
+    [EIP-155].
+
+    [EIP-155]: https://eips.ethereum.org/EIPS/eip-155
+    """
+
+    def __init__(self, expected: U64, actual: U64):
+        super().__init__(f"expected chain_id `{expected}` but got `{actual}`")
+        self.expected = expected
+        self.actual = actual
+
+
 class TransactionTypeError(InvalidTransaction):
     """
     Unknown [EIP-2718] transaction type byte.
diff --git a/src/ethereum/forks/monad_nine/fork.py b/src/ethereum/forks/monad_nine/fork.py
index 068442ac1b1..e7c56f8c815 100644
--- a/src/ethereum/forks/monad_nine/fork.py
+++ b/src/ethereum/forks/monad_nine/fork.py
@@ -44,6 +44,7 @@
     NoBlobDataError,
     PriorityFeeGreaterThanMaxFeeError,
     TransactionTypeContractCreationError,
+    WrongChainIdError,
 )
 from .fork_types import Authorization, VersionedHash
 from .requests import (
@@ -73,6 +74,7 @@
     LegacyTransaction,
     SetCodeTransaction,
     Transaction,
+    chain_id,
     decode_transaction,
     encode_transaction,
     get_transaction_hash,
@@ -479,7 +481,14 @@ def check_transaction(
     if tx_blob_gas_used > blob_gas_available:
         raise BlobGasLimitExceededError("blob gas limit exceeded")
 
-    sender_address = recover_sender(block_env.chain_id, tx)
+    tx_chain_id = chain_id(tx)
+    if tx_chain_id is not None and tx_chain_id != block_env.chain_id:
+        raise WrongChainIdError(
+            expected=block_env.chain_id,
+            actual=tx_chain_id,
+        )
+
+    sender_address = recover_sender(tx)
     sender_account = get_account(tx_state, sender_address)
 
     if isinstance(
diff --git a/src/ethereum/forks/monad_nine/transactions.py b/src/ethereum/forks/monad_nine/transactions.py
index 04c4b77388c..24bb4880a74 100644
--- a/src/ethereum/forks/monad_nine/transactions.py
+++ b/src/ethereum/forks/monad_nine/transactions.py
@@ -625,7 +625,25 @@ def calculate_intrinsic_cost(tx: Transaction) -> Tuple[Uint, Uint]:
     )
 
 
-def recover_sender(chain_id: U64, tx: Transaction) -> Address:
+def chain_id(tx: Transaction) -> None | U64:
+    """
+    Extract the chain identifier from a transaction. See [EIP-155].
+
+    [EIP-155]: https://eips.ethereum.org/EIPS/eip-155
+    """
+    if isinstance(tx, LegacyTransaction):
+        if tx.v == 27 or tx.v == 28:
+            return None
+
+        if tx.v < U256(35):
+            raise InvalidSignatureError("bad v")
+
+        return U64((tx.v - U256(35)) >> U256(1))
+    else:
+        return tx.chain_id
+
+
+def recover_sender(tx: Transaction) -> Address:
     """
     Extracts the sender address from a transaction.
 
@@ -635,9 +653,9 @@ def recover_sender(chain_id: U64, tx: Transaction) -> Address:
     signing hash of the transaction. The sender's public key can be obtained
     with these two values and therefore the sender address can be retrieved.
 
-    This function takes chain_id and a transaction as parameters and returns
-    the address of the sender of the transaction. It raises an
-    `InvalidSignatureError` if the signature values (r, s, v) are invalid.
+    This function takes a transaction as a parameter and returns the address
+    of the sender of the transaction. It raises an `InvalidSignatureError` if
+    the signature values (r, s, v) are invalid.
     """
     r, s = tx.r, tx.s
     if U256(0) >= r or r >= SECP256K1N:
@@ -652,14 +670,14 @@ def recover_sender(chain_id: U64, tx: Transaction) -> Address:
                 r, s, v - U256(27), signing_hash_pre155(tx)
             )
         else:
-            chain_id_x2 = U256(chain_id) * U256(2)
-            if v != U256(35) + chain_id_x2 and v != U256(36) + chain_id_x2:
-                raise InvalidSignatureError("bad v")
+            assert v >= U256(35), "call chain_id before recover_sender"
+            tx_chain_id = U64((v - U256(35)) >> U256(1))
+            v = (v - U256(35)) & U256(1)
             public_key = secp256k1_recover(
                 r,
                 s,
-                v - U256(35) - chain_id_x2,
-                signing_hash_155(tx, chain_id),
+                v,
+                signing_hash_155(tx, tx_chain_id),
             )
     elif isinstance(tx, AccessListTransaction):
         if tx.y_parity not in (U256(0), U256(1)):
diff --git a/src/ethereum/forks/monad_ten/exceptions.py b/src/ethereum/forks/monad_ten/exceptions.py
index 3074a1f738f..8d409eaaa02 100644
--- a/src/ethereum/forks/monad_ten/exceptions.py
+++ b/src/ethereum/forks/monad_ten/exceptions.py
@@ -4,7 +4,7 @@
 
 from typing import TYPE_CHECKING, Final
 
-from ethereum_types.numeric import Uint
+from ethereum_types.numeric import U64, Uint
 
 from ethereum.exceptions import InvalidTransaction
 
@@ -12,6 +12,20 @@
     from .transactions import Transaction
 
 
+class WrongChainIdError(InvalidTransaction):
+    """
+    Chain identifier from a transaction does not match the executing chain. See
+    [EIP-155].
+
+    [EIP-155]: https://eips.ethereum.org/EIPS/eip-155
+    """
+
+    def __init__(self, expected: U64, actual: U64):
+        super().__init__(f"expected chain_id `{expected}` but got `{actual}`")
+        self.expected = expected
+        self.actual = actual
+
+
 class TransactionTypeError(InvalidTransaction):
     """
     Unknown [EIP-2718] transaction type byte.
diff --git a/src/ethereum/forks/monad_ten/fork.py b/src/ethereum/forks/monad_ten/fork.py
index d743f1169a3..653f05d030f 100644
--- a/src/ethereum/forks/monad_ten/fork.py
+++ b/src/ethereum/forks/monad_ten/fork.py
@@ -47,6 +47,7 @@
     NoBlobDataError,
     PriorityFeeGreaterThanMaxFeeError,
     TransactionTypeContractCreationError,
+    WrongChainIdError,
 )
 from .fork_types import Authorization, VersionedHash
 from .requests import (
@@ -76,6 +77,7 @@
     LegacyTransaction,
     SetCodeTransaction,
     Transaction,
+    chain_id,
     decode_transaction,
     encode_transaction,
     get_transaction_hash,
@@ -482,7 +484,14 @@ def check_transaction(
     if tx_blob_gas_used > blob_gas_available:
         raise BlobGasLimitExceededError("blob gas limit exceeded")
 
-    sender_address = recover_sender(block_env.chain_id, tx)
+    tx_chain_id = chain_id(tx)
+    if tx_chain_id is not None and tx_chain_id != block_env.chain_id:
+        raise WrongChainIdError(
+            expected=block_env.chain_id,
+            actual=tx_chain_id,
+        )
+
+    sender_address = recover_sender(tx)
     sender_account = get_account(tx_state, sender_address)
 
     if isinstance(
diff --git a/src/ethereum/forks/monad_ten/transactions.py b/src/ethereum/forks/monad_ten/transactions.py
index 04c4b77388c..24bb4880a74 100644
--- a/src/ethereum/forks/monad_ten/transactions.py
+++ b/src/ethereum/forks/monad_ten/transactions.py
@@ -625,7 +625,25 @@ def calculate_intrinsic_cost(tx: Transaction) -> Tuple[Uint, Uint]:
     )
 
 
-def recover_sender(chain_id: U64, tx: Transaction) -> Address:
+def chain_id(tx: Transaction) -> None | U64:
+    """
+    Extract the chain identifier from a transaction. See [EIP-155].
+
+    [EIP-155]: https://eips.ethereum.org/EIPS/eip-155
+    """
+    if isinstance(tx, LegacyTransaction):
+        if tx.v == 27 or tx.v == 28:
+            return None
+
+        if tx.v < U256(35):
+            raise InvalidSignatureError("bad v")
+
+        return U64((tx.v - U256(35)) >> U256(1))
+    else:
+        return tx.chain_id
+
+
+def recover_sender(tx: Transaction) -> Address:
     """
     Extracts the sender address from a transaction.
 
@@ -635,9 +653,9 @@ def recover_sender(chain_id: U64, tx: Transaction) -> Address:
     signing hash of the transaction. The sender's public key can be obtained
     with these two values and therefore the sender address can be retrieved.
 
-    This function takes chain_id and a transaction as parameters and returns
-    the address of the sender of the transaction. It raises an
-    `InvalidSignatureError` if the signature values (r, s, v) are invalid.
+    This function takes a transaction as a parameter and returns the address
+    of the sender of the transaction. It raises an `InvalidSignatureError` if
+    the signature values (r, s, v) are invalid.
     """
     r, s = tx.r, tx.s
     if U256(0) >= r or r >= SECP256K1N:
@@ -652,14 +670,14 @@ def recover_sender(chain_id: U64, tx: Transaction) -> Address:
                 r, s, v - U256(27), signing_hash_pre155(tx)
             )
         else:
-            chain_id_x2 = U256(chain_id) * U256(2)
-            if v != U256(35) + chain_id_x2 and v != U256(36) + chain_id_x2:
-                raise InvalidSignatureError("bad v")
+            assert v >= U256(35), "call chain_id before recover_sender"
+            tx_chain_id = U64((v - U256(35)) >> U256(1))
+            v = (v - U256(35)) & U256(1)
             public_key = secp256k1_recover(
                 r,
                 s,
-                v - U256(35) - chain_id_x2,
-                signing_hash_155(tx, chain_id),
+                v,
+                signing_hash_155(tx, tx_chain_id),
             )
     elif isinstance(tx, AccessListTransaction):
         if tx.y_parity not in (U256(0), U256(1)):
diff --git a/tests/cancun/eip6780_selfdestruct/test_dynamic_create2_selfdestruct_collision.py b/tests/cancun/eip6780_selfdestruct/test_dynamic_create2_selfdestruct_collision.py
index 66d4597204f..9682a5d5b1a 100644
--- a/tests/cancun/eip6780_selfdestruct/test_dynamic_create2_selfdestruct_collision.py
+++ b/tests/cancun/eip6780_selfdestruct/test_dynamic_create2_selfdestruct_collision.py
@@ -89,9 +89,7 @@ def test_dynamic_create2_selfdestruct_collision(
     # Constants
     address_zero = Address(0x00)
     create2_salt = 1
-    subcall_gas = 100_000
-    if fork.is_eip_enabled(8037):
-        subcall_gas = 500_000
+    subcall_gas = 100_000 + fork_extra_gas
 
     # Create EOA for sendall destination (receives selfdestruct funds)
     sendall_destination = pre.fund_eoa(0)  # Will be funded by selfdestruct
@@ -317,9 +315,7 @@ def test_dynamic_create2_selfdestruct_collision_two_different_transactions(
     # Constants
     address_zero = Address(0x00)
     create2_salt = 1
-    subcall_gas = 100_000
-    if fork.is_eip_enabled(8037):
-        subcall_gas = 500_000
+    subcall_gas = 100_000 + fork_extra_gas
 
     # Create EOA for sendall destination (receives selfdestruct funds)
     sendall_destination = pre.fund_eoa(0)  # Will be funded by selfdestruct
@@ -593,9 +589,7 @@ def test_dynamic_create2_selfdestruct_collision_multi_tx(
 
     # Constants
     create2_salt = 1
-    subcall_gas = 100_000
-    if fork.is_eip_enabled(8037):
-        subcall_gas = 500_000
+    subcall_gas = 100_000 + fork_extra_gas
 
     # Create EOA for sendall destination (receives selfdestruct funds)
     sendall_destination = pre.fund_eoa(0)  # Will be funded by selfdestruct
diff --git a/tests/prague/eip7702_set_code_tx/test_set_code_txs_2.py b/tests/prague/eip7702_set_code_tx/test_set_code_txs_2.py
index 05bc9cbdef4..2cbe05b6b12 100644
--- a/tests/prague/eip7702_set_code_tx/test_set_code_txs_2.py
+++ b/tests/prague/eip7702_set_code_tx/test_set_code_txs_2.py
@@ -1973,6 +1973,10 @@ def test_pointer_resets_an_empty_code_account_with_storage(
         value=1000,
         nonce=6,
         sender=sender,
+        # The automatic gas limits fill the first block, which raises the
+        # base fee for this block on forks that count the gas limit
+        # rather than the gas used towards the block gas used.
+        max_fee_per_gas=100,
         authorization_list=[
             AuthorizationTuple(
                 address=newly_created_address,