diff --git a/src/safe_cli/ethereum_client.py b/src/safe_cli/ethereum_client.py
new file mode 100644
index 00000000..e9bbc792
--- /dev/null
+++ b/src/safe_cli/ethereum_client.py
@@ -0,0 +1,34 @@
+from safe_eth.eth import EthereumClient, TxSpeed
+from web3.types import TxParams, Wei
+
+# Headroom of maxFeePerGas over the forecast base fee. ethers, viem and web3.py's default strategy use the same
+# factor: the base fee can rise 12.5% per block, so 2x keeps a transaction valid for about six full blocks in a row.
+BASE_FEE_MULTIPLIER = 2
+
+
+class SafeCliEthereumClient(EthereumClient):
+    """
+    ``EthereumClient`` whose EIP-1559 fees leave headroom over the forecast base fee.
+
+    ``EthereumClient.set_eip1559_fees`` sets ``maxFeePerGas`` to the next block's forecast base fee plus the tip,
+    with no headroom. If the base fee rises before the transaction is included, the cap falls below it and the
+    transaction waits. A chain that charges more than its fee history forecasts (a fixed-fee chain whose node still
+    projects a falling base fee) refuses the transaction outright.
+
+    ``maxFeePerGas`` is a cap, not a price: the sender still pays the base fee plus the tip. The sender's balance
+    must cover ``gas * maxFeePerGas``, so a higher cap needs a larger balance.
+    """
+
+    def set_eip1559_fees(
+        self, tx: TxParams, tx_speed: TxSpeed = TxSpeed.NORMAL
+    ) -> TxParams:
+        """
+        :return: TxParams in EIP1559 format, with ``maxFeePerGas = BASE_FEE_MULTIPLIER * base fee + tip``
+        :raises: ValueError if EIP1559 not supported
+        """
+        tx = super().set_eip1559_fees(tx, tx_speed)
+        # The parent sets maxFeePerGas = base fee + tip
+        tip = tx["maxPriorityFeePerGas"]
+        base_fee = tx["maxFeePerGas"] - tip
+        tx["maxFeePerGas"] = Wei(BASE_FEE_MULTIPLIER * base_fee + tip)
+        return tx
diff --git a/src/safe_cli/operators/safe_operator.py b/src/safe_cli/operators/safe_operator.py
index 0c94779b..f3e20699 100644
--- a/src/safe_cli/operators/safe_operator.py
+++ b/src/safe_cli/operators/safe_operator.py
@@ -38,6 +38,7 @@
 from web3.contract import Contract
 from web3.exceptions import BadFunctionCallOutput
 
+from safe_cli.ethereum_client import SafeCliEthereumClient
 from safe_cli.ethereum_hd_wallet import get_account_from_words
 from safe_cli.operators.exceptions import (
     AccountNotLoadedException,
@@ -162,7 +163,7 @@ def __init__(
     ):
         self.address = address
         self.node_url = node_url
-        self.ethereum_client = EthereumClient(self.node_url)
+        self.ethereum_client = SafeCliEthereumClient(self.node_url)
         self.ens = ENS.from_web3(self.ethereum_client.w3)
         self.network: EthereumNetwork = self.ethereum_client.get_network()
         try:
diff --git a/tests/test_ethereum_client.py b/tests/test_ethereum_client.py
new file mode 100644
index 00000000..7c70541b
--- /dev/null
+++ b/tests/test_ethereum_client.py
@@ -0,0 +1,103 @@
+import unittest
+from unittest import mock
+
+from eth_account import Account
+from safe_eth.eth import EthereumClient
+from web3 import Web3
+
+from safe_cli.ethereum_client import BASE_FEE_MULTIPLIER, SafeCliEthereumClient
+from safe_cli.operators.hw_wallets.hw_wallet_manager import HwWalletManager
+
+from .safe_cli_test_case_mixin import SafeCliTestCaseMixin
+
+GWEI = 10**9
+
+
+class TestSafeCliEthereumClient(SafeCliTestCaseMixin, unittest.TestCase):
+    def _fees(self, base_fee: int, tip: int) -> dict:
+        ethereum_client = SafeCliEthereumClient(self.ethereum_node_url)
+        with mock.patch.object(
+            EthereumClient, "estimate_fee_eip1559", return_value=(base_fee, tip)
+        ):
+            return ethereum_client.set_eip1559_fees({"gasPrice": 1})
+
+    def test_headroom_over_the_forecast(self):
+        self.assertEqual(BASE_FEE_MULTIPLIER, 2)
+        fees = self._fees(20 * GWEI, 2 * GWEI)
+        self.assertEqual(fees["maxFeePerGas"], 42 * GWEI)
+        self.assertEqual(fees["maxPriorityFeePerGas"], 2 * GWEI)
+        self.assertNotIn("gasPrice", fees)
+
+        fees = self._fees(0, 0)
+        self.assertEqual(fees["maxFeePerGas"], 0)
+
+    def test_chain_charging_more_than_it_forecasts(self):
+        # A node that forecasts 625,625 gwei for the next block and charges 715,000: the cap clears it
+        fees = self._fees(625_625 * GWEI, 0)
+        self.assertEqual(fees["maxFeePerGas"], 1_251_250 * GWEI)
+        self.assertEqual(fees["maxPriorityFeePerGas"], 0)
+
+    def _sent_to(self, address: str, since_block: int) -> list:
+        return [
+            transaction
+            for number in range(since_block + 1, self.w3.eth.block_number + 1)
+            for transaction in self.w3.eth.get_block(number, True)["transactions"]
+            if transaction["to"] == address
+        ]
+
+    def _assert_included_with_headroom(self, transaction, forecast: int):
+        self.assertEqual(transaction["type"], 2)
+        self.assertEqual(
+            transaction["maxFeePerGas"],
+            BASE_FEE_MULTIPLIER * forecast + transaction["maxPriorityFeePerGas"],
+        )
+        self.assertGreaterEqual(
+            transaction["maxFeePerGas"],
+            self.w3.eth.get_block(transaction["blockNumber"])["baseFeePerGas"],
+        )
+
+    def test_every_way_of_sending_uses_it(self):
+        safe_operator = self.setup_operator()
+        owner = self.ethereum_test_account
+        safe_operator.accounts.add(owner)
+        safe_operator.default_sender = owner
+        self.w3.eth.send_transaction(
+            {"from": owner.address, "to": safe_operator.address, "value": 10}
+        )
+        # A fee history that forecasts 0.6 x the base fee the chain charges. Without headroom the cap is below
+        # the base fee and the node refuses the transaction: "max fee per gas less than block base fee".
+        forecast = self.w3.eth.get_block("latest")["baseFeePerGas"] * 6 // 10
+        with mock.patch.object(
+            EthereumClient, "estimate_fee_eip1559", return_value=(forecast, 0)
+        ):
+            # Executing a Safe transaction with a local key
+            block = self.w3.eth.block_number
+            self.assertTrue(safe_operator.send_ether(Account.create().address, 1))
+            (transaction,) = self._sent_to(safe_operator.address, block)
+            self._assert_included_with_headroom(transaction, forecast)
+
+            # approve_hash
+            block = self.w3.eth.block_number
+            self.assertTrue(
+                safe_operator.approve_hash(Web3.keccak(text="headroom"), owner.address)
+            )
+            (transaction,) = self._sent_to(safe_operator.address, block)
+            self._assert_included_with_headroom(transaction, forecast)
+
+            # Executing a Safe transaction with a hardware wallet
+            sender = mock.Mock()
+            sender.address = owner.address
+            sender.get_signed_raw_transaction.side_effect = lambda tx, chain_id: (
+                self.w3.eth.account.sign_transaction(tx, owner.key).raw_transaction
+            )
+            safe_operator.default_sender = None
+            safe_operator.hw_wallet_manager = HwWalletManager()
+            safe_operator.hw_wallet_manager.sender = sender
+            block = self.w3.eth.block_number
+            self.assertTrue(safe_operator.send_ether(Account.create().address, 1))
+            (transaction,) = self._sent_to(safe_operator.address, block)
+            self._assert_included_with_headroom(transaction, forecast)
+
+
+if __name__ == "__main__":
+    unittest.main()