From 5326e178686bd8fd295c5d2b7773b1d8e2cba2cb Mon Sep 17 00:00:00 2001
From: tech0priyanshu <priyanshuyadv101106@gmail.com>
Date: Thu, 4 Jun 2026 01:26:57 +0530
Subject: [PATCH 1/9] feat: set_max_transaction to client

Signed-off-by: tech0priyanshu <priyanshuyadv101106@gmail.com>

removed print

Signed-off-by: tech0priyanshu <priyanshuyadv101106@gmail.com>

fixed magicMock

Signed-off-by: tech0priyanshu <priyanshuyadv101106@gmail.com>

fixed precheckerror

Signed-off-by: tech0priyanshu <priyanshuyadv101106@gmail.com>

fixes

Signed-off-by: tech0priyanshu <priyanshuyadv101106@gmail.com>

fixing magicmock

Signed-off-by: tech0priyanshu <priyanshuyadv101106@gmail.com>

fix: callback for _coerce_fee

Signed-off-by: tech0priyanshu <priyanshuyadv101106@gmail.com>

fix: comment moved

Signed-off-by: tech0priyanshu <priyanshuyadv101106@gmail.com>

fix: max_transaction_fee to default_max_transaction_fee

Signed-off-by: tech0priyanshu <priyanshuyadv101106@gmail.com>
---
 src/hiero_sdk_python/client/client.py         |  14 +++
 src/hiero_sdk_python/hbar.py                  |  15 +++
 .../transaction/transaction.py                |  28 ++++-
 .../account_update_transaction_e2e_test.py    |  14 ++-
 tests/unit/client_test.py                     |  43 +++++++
 tests/unit/fee_estimate_query_test.py         |   5 +
 tests/unit/file_append_transaction_test.py    |   2 +
 .../unit/transaction_freeze_and_bytes_test.py | 105 ++++++++++++++++++
 8 files changed, 219 insertions(+), 7 deletions(-)

diff --git a/src/hiero_sdk_python/client/client.py b/src/hiero_sdk_python/client/client.py
index 361324d06..3a9329223 100644
--- a/src/hiero_sdk_python/client/client.py
+++ b/src/hiero_sdk_python/client/client.py
@@ -59,6 +59,7 @@ def __init__(self, network: Network = None) -> None:
 
         self.max_attempts: int = 10
         self.default_max_query_payment: Hbar = DEFAULT_MAX_QUERY_PAYMENT
+        self.default_max_transaction_fee: Hbar | None = None
 
         self._min_backoff: float = DEFAULT_MIN_BACKOFF
         self._max_backoff: float = DEFAULT_MAX_BACKOFF
@@ -290,6 +291,19 @@ def set_default_max_query_payment(self, max_query_payment: int | float | Decimal
         self.default_max_query_payment = value
         return self
 
+    def set_default_max_transaction_fee(
+        self,
+        max_transaction_fee: int | float | Decimal | Hbar,
+    ) -> Client:
+        """
+        Sets the default maximum Hbar fee allowed for any  transaction executed by this client.
+        """
+        value = Hbar._coerce_fee(max_transaction_fee)
+        if value < Hbar.ZERO:
+            raise ValueError("max_transaction_fee must be non-negative")
+        self.default_max_transaction_fee = value
+        return self
+
     def set_max_attempts(self, max_attempts: int) -> Client:
         """
         Set the maximum number of execution attempts for all transactions and queries
diff --git a/src/hiero_sdk_python/hbar.py b/src/hiero_sdk_python/hbar.py
index 22e3d03a6..cc58b5d2a 100644
--- a/src/hiero_sdk_python/hbar.py
+++ b/src/hiero_sdk_python/hbar.py
@@ -83,6 +83,21 @@ def negated(self) -> Hbar:
         """
         return Hbar.from_tinybars(-self._amount_in_tinybar)
 
+    @staticmethod
+    def _coerce_fee(value: int | float | Decimal | Hbar) -> Hbar:
+        """
+        Coerce a value to an Hbar instance. Accepts int, float, Decimal, or Hbar (but not bool).
+        Args:
+            value: The value to coerce.
+        Returns:
+            Hbar: An Hbar instance.
+        Raises:
+            TypeError: If value is not a valid type.
+        """
+        if isinstance(value, bool) or not isinstance(value, (int, float, Decimal, Hbar)):
+            raise TypeError(f"value must be int, float, Decimal, or Hbar, got {type(value).__name__}")
+        return value if isinstance(value, Hbar) else Hbar(value)
+
     @classmethod
     def of(cls, amount: int | float | Decimal, unit: HbarUnit) -> Hbar:
         """
diff --git a/src/hiero_sdk_python/transaction/transaction.py b/src/hiero_sdk_python/transaction/transaction.py
index f83298bf9..99a3ec254 100644
--- a/src/hiero_sdk_python/transaction/transaction.py
+++ b/src/hiero_sdk_python/transaction/transaction.py
@@ -509,7 +509,7 @@ def build_base_transaction_body(self) -> transaction_pb2.TransactionBody:
         """
         transaction_body = transaction_pb2.TransactionBody()
 
-        fee = self._transaction_fee or self._default_transaction_fee
+        fee = self._transaction_fee if self._transaction_fee is not None else self._default_transaction_fee
         if hasattr(fee, "to_tinybars"):
             transaction_body.transactionFee = int(fee.to_tinybars())
         else:
@@ -837,6 +837,32 @@ def from_bytes(transaction_bytes: bytes):
             transaction_body, signed_transaction.bodyBytes, signed_transaction.sigMap
         )
 
+    def set_default_max_transaction_fee(self, max_transaction_fee):
+        """
+         Sets the maximum transaction fee for this transaction.
+
+        The maximum transaction fee specifies the highest fee that can be
+        charged when the transaction is executed. The value must be
+        non-negative.
+
+        Args:
+             max_transaction_fee (Hbar | int | str): The maximum transaction
+             fee. Accepted types are those supported by ``Hbar._coerce_fee``.
+
+        Returns:
+            Self: This transaction instance, allowing method chaining.
+
+        Raises:
+            ValueError: If ``max_transaction_fee`` is negative.
+            RuntimeError: If the transaction has been frozen.
+        """
+        self._require_not_frozen()
+        value = Hbar._coerce_fee(max_transaction_fee)
+        if value < Hbar.ZERO:
+            raise ValueError("max_transaction_fee must be non-negative")
+        self.transaction_fee = value
+        return self
+
     @staticmethod
     def _get_transaction_class(transaction_type: str):
         """
diff --git a/tests/integration/account_update_transaction_e2e_test.py b/tests/integration/account_update_transaction_e2e_test.py
index 88f0ed8cf..ff2b046a2 100644
--- a/tests/integration/account_update_transaction_e2e_test.py
+++ b/tests/integration/account_update_transaction_e2e_test.py
@@ -12,6 +12,7 @@
 from hiero_sdk_python.crypto.key_list import KeyList
 from hiero_sdk_python.crypto.private_key import PrivateKey
 from hiero_sdk_python.Duration import Duration
+from hiero_sdk_python.exceptions import PrecheckError
 from hiero_sdk_python.hbar import Hbar
 from hiero_sdk_python.query.account_info_query import AccountInfoQuery
 from hiero_sdk_python.response_code import ResponseCode
@@ -241,14 +242,14 @@ def test_integration_account_update_transaction_invalid_auto_renew_period(env):
 
 def _apply_tiny_max_fee_if_supported(tx, client) -> bool:
     # Try tx-level setters
-    for attr in ("set_max_transaction_fee", "set_max_fee", "set_transaction_fee"):
+    for attr in ("set_default_max_transaction_fee", "set_max_fee", "set_transaction_fee"):
         if hasattr(tx, attr):
             getattr(tx, attr)(Hbar.from_tinybars(1))
             return True
     # Try client-level default
     for attr in (
         "set_default_max_transaction_fee",
-        "set_max_transaction_fee",
+        "set_default_max_transaction_fee",
         "set_default_max_fee",
         "setMaxTransactionFee",
     ):
@@ -283,10 +284,11 @@ def test_account_update_insufficient_fee_with_valid_expiration_bump(env):
     if not _apply_tiny_max_fee_if_supported(tx, env.client):
         pytest.skip("SDK lacks a max-fee API; cannot deterministically trigger INSUFFICIENT_TX_FEE.")
 
-    receipt = tx.execute(env.client)
-    assert receipt.status == ResponseCode.INSUFFICIENT_TX_FEE, (
-        f"Expected INSUFFICIENT_TX_FEE but got {ResponseCode(receipt.status).name}"
-    )
+    # If it succeeds or raises a different error, the test will fail.
+    with pytest.raises(PrecheckError) as exc_info:
+        tx.execute(env.client)
+
+    assert exc_info.value.status == ResponseCode.INSUFFICIENT_TX_FEE
 
     # Confirm expiration time did not change
     info_after = AccountInfoQuery(account_id).execute(env.client)
diff --git a/tests/unit/client_test.py b/tests/unit/client_test.py
index 3cdc79c1f..15737a222 100644
--- a/tests/unit/client_test.py
+++ b/tests/unit/client_test.py
@@ -231,6 +231,49 @@ def test_set_default_max_query_payment_valid_param(valid_amount, expected):
     assert client.default_max_query_payment == expected
 
 
+def test_default_max_transaction_fee_is_none():
+    """Default `default_max_transaction_fee` should be None."""
+    client = Client.for_testnet()
+    assert client.default_max_transaction_fee is None
+
+
+@pytest.mark.parametrize(
+    "valid_amount,expected",
+    [
+        (1, Hbar(1)),
+        (0.1, Hbar(0.1)),
+        (Decimal("0.1"), Hbar(Decimal("0.1"))),
+        (Hbar(1), Hbar(1)),
+        (Hbar(0), Hbar(0)),
+    ],
+)
+def test_set_default_max_transaction_fee_valid_param(valid_amount, expected):
+    """Test set_default_max_transaction_fee converts inputs to Hbar and stores them."""
+    client = Client.for_testnet()
+
+    returned = client.set_default_max_transaction_fee(valid_amount)
+    assert client.default_max_transaction_fee == expected
+    assert returned is client
+
+
+@pytest.mark.parametrize("invalid_amount", ["1", True, False, None, object()])
+def test_set_default_max_transaction_fee_invalid_param(invalid_amount):
+    """Test set_default_max_transaction_fee rejects invalid types."""
+    client = Client.for_testnet()
+
+    with pytest.raises(TypeError):
+        client.set_default_max_transaction_fee(invalid_amount)
+
+
+@pytest.mark.parametrize("negative_amount", [-1, -0.1, Decimal("-0.1"), Hbar(-1)])
+def test_set_default_max_transaction_fee_negative_value(negative_amount):
+    """Test set_default_max_transaction_fee rejects negative values."""
+    client = Client.for_testnet()
+
+    with pytest.raises(ValueError):
+        client.set_default_max_transaction_fee(negative_amount)
+
+
 @pytest.mark.parametrize("negative_amount", [-1, -0.1, Decimal("-0.1"), Decimal("-1"), Hbar(-1)])
 def test_set_default_max_query_payment_negative_value(negative_amount):
     """Test set_default_max_query_payment for negative amount values."""
diff --git a/tests/unit/fee_estimate_query_test.py b/tests/unit/fee_estimate_query_test.py
index 6b6d253af..582bcef81 100644
--- a/tests/unit/fee_estimate_query_test.py
+++ b/tests/unit/fee_estimate_query_test.py
@@ -32,6 +32,7 @@ def mock_client():
     client.mirror_network = "https://testnet.mirrornode.hedera.com"
     client.max_retries = 3
 
+    client.default_max_transaction_fee = Hbar(2)
     client.generate_transaction_id.return_value = TransactionId.generate(AccountId(0, 0, 1001))
     client.operator_account_id._to_proto.return_value = AccountId(0, 0, 1)._to_proto()
 
@@ -337,6 +338,7 @@ def test_port_replacement_for_localhost_execute_single():
     """Test localhost:38081 is replaced with :8084."""
     client_1 = MagicMock()
     client_1.network.get_mirror_rest_url.return_value = "http://localhost:38081/api/v1"
+    client_1.default_max_transaction_fee = Hbar(1)
 
     tx = (
         TransferTransaction()
@@ -354,6 +356,7 @@ def test_port_replacement_for_localhost_execute_single():
 
     client_2 = MagicMock()
     client_2.network.get_mirror_rest_url.return_value = "http://127.0.0.1:38081/api/v1"
+    client_2.default_max_transaction_fee = Hbar(1)
 
     with patch.object(query, "_execute_single") as mock_execute_single:
         query.execute(client_2)
@@ -366,6 +369,7 @@ def test_port_replacement_for_localhost_execute_multiple():
     """Test localhost:38081 is replaced with :8084 for chunked tx."""
     client_1 = MagicMock()
     client_1.network.get_mirror_rest_url.return_value = "http://localhost:38081/api/v1"
+    client_1.default_max_transaction_fee = Hbar(1)
 
     tx = (
         TopicMessageSubmitTransaction()
@@ -388,6 +392,7 @@ def test_port_replacement_for_localhost_execute_multiple():
 
     client_2 = MagicMock()
     client_2.network.get_mirror_rest_url.return_value = "http://127.0.0.1:38081/api/v1"
+    client_2.default_max_transaction_fee = Hbar(1)
 
     with patch.object(query, "_execute_chunked", return_value=MagicMock()) as mock_execute_chunked:
         query.execute(client_2)
diff --git a/tests/unit/file_append_transaction_test.py b/tests/unit/file_append_transaction_test.py
index 4aa83a186..54d9fe93e 100644
--- a/tests/unit/file_append_transaction_test.py
+++ b/tests/unit/file_append_transaction_test.py
@@ -99,6 +99,7 @@ def test_freeze_with_generates_transaction_ids():
 
     # Mock client and transaction_id
     mock_client = MagicMock()
+    mock_client.default_max_transaction_fee = Hbar(1)
     mock_transaction_id = TransactionId(account_id=MagicMock(), valid_start=Timestamp(0, 1))
     file_tx.transaction_id = mock_transaction_id
 
@@ -141,6 +142,7 @@ def test_multi_chunk_execution():
 
     # Mock client and responses
     mock_client = MagicMock()
+    mock_client.default_max_transaction_fee = Hbar(1)
     mock_receipt = MagicMock(spec=TransactionReceipt)
     mock_receipt.status = ResponseCode.SUCCESS
 
diff --git a/tests/unit/transaction_freeze_and_bytes_test.py b/tests/unit/transaction_freeze_and_bytes_test.py
index 6916cb27e..f1aae0bce 100644
--- a/tests/unit/transaction_freeze_and_bytes_test.py
+++ b/tests/unit/transaction_freeze_and_bytes_test.py
@@ -8,6 +8,8 @@
 
 from __future__ import annotations
 
+from decimal import Decimal
+
 import pytest
 
 from hiero_sdk_python.account.account_id import AccountId
@@ -15,6 +17,7 @@
 from hiero_sdk_python.hapi.services.transaction_response_pb2 import (
     TransactionResponse as TransactionResponseProto,
 )
+from hiero_sdk_python.hbar import Hbar
 from hiero_sdk_python.transaction.transaction_id import TransactionId
 from hiero_sdk_python.transaction.transfer_transaction import TransferTransaction
 
@@ -67,6 +70,45 @@ def test_freeze_with_valid_parameters():
     assert node_id in transaction._transaction_body_bytes[transaction_id]
 
 
+@pytest.mark.parametrize(
+    "valid_amount,expected",
+    [
+        (1, 100_000_000),
+        (0.1, 10_000_000),
+        (Decimal("0.1"), 10_000_000),
+        (Hbar(1), 100_000_000),
+        (Hbar(0), 0),
+    ],
+)
+def test_set_max_transaction_fee_valid_param(valid_amount, expected):
+    """Transaction.set_default_max_transaction_fee should accept various numeric types and Hbar."""
+    tx = TransferTransaction()
+
+    returned = tx.set_default_max_transaction_fee(valid_amount)
+    assert tx.transaction_fee == expected
+    assert returned is tx
+
+
+@pytest.mark.parametrize("invalid_amount", ["1", True, False, None, object()])
+def test_set_max_transaction_fee_invalid_param(invalid_amount):
+    """Transaction.set_default_max_transaction_fee should reject invalid types."""
+    tx = TransferTransaction()
+
+    with pytest.raises(TypeError):
+        tx.set_default_max_transaction_fee(invalid_amount)
+
+
+@pytest.mark.parametrize("negative_amount", [-1, -0.1, Decimal("-0.1"), Hbar(-1)])
+def test_set_max_transaction_fee_negative_value(negative_amount):
+    """Transaction.set_default_max_transaction_fee should reject negative values."""
+    tx = TransferTransaction()
+
+    with pytest.raises(ValueError):
+        tx.set_default_max_transaction_fee(negative_amount)
+    # checking state un modified
+    assert len(tx._transaction_body_bytes) == 0
+
+
 def test_freeze_is_idempotent():
     """Test that calling freeze() multiple times doesn't cause issues."""
     operator_id = AccountId.from_string("0.0.1234")
@@ -715,3 +757,66 @@ def test_map_response_raises_if_proto_request_is_not_transaction():
             node_id=mock_node_id,
             proto_request=invalid_proto_request,
         )
+
+
+def test_fee_resolution_transaction_precedence(mock_client):
+    """Transaction fee explicitly set should take precedence over client default."""
+    tx = TransferTransaction()
+    tx.set_default_max_transaction_fee(Hbar(10))
+
+    # client has different default
+    mock_client.set_default_max_transaction_fee(Hbar(5))
+
+    before = tx.transaction_fee
+    tx.freeze_with(mock_client)
+
+    assert tx.transaction_fee == 1_000_000_000
+    assert tx.transaction_fee == before
+
+
+def test_fee_resolution_client_default_used_when_transaction_missing(mock_client):
+    """When transaction fee is not set, client.default_max_transaction_fee should be used."""
+    tx = TransferTransaction()
+    # leave tx.transaction_fee as None
+
+    mock_client.set_default_max_transaction_fee(Hbar(7))
+
+    tx.freeze_with(mock_client)
+
+    assert tx.transaction_fee == 700_000_000
+
+
+def test_fee_resolution_falls_back_to_transaction_default(mock_client):
+    """When neither transaction nor client provide a fee, fallback to transaction default Hbar(1)."""
+    tx = TransferTransaction()
+    tx.set_transaction_id(TransactionId.generate(AccountId.from_string("0.0.1234")))
+    # Ensure client default is None
+    mock_client.default_max_transaction_fee = None
+
+    tx.freeze_with(mock_client)
+
+    assert tx.transaction_fee == 100_000_000  # Default fee for TransferTransaction
+
+
+def test_resolved_fee_serialized_into_transaction_body(mock_client):
+    """The resolved fee must reach the serialized proto transactionFee."""
+    tx = TransferTransaction()
+
+    tx.set_default_max_transaction_fee(Hbar(2))
+
+    body = tx.build_base_scheduled_body()
+
+    assert body.transactionFee == Hbar(2).to_tinybars()
+
+
+def test_max_transaction_fee_survives_to_bytes_round_trip(mock_client):
+    """An explicitly set max fee must survive a to_bytes -> from_bytes round trip."""
+    tx = TransferTransaction()
+
+    tx.set_default_max_transaction_fee(Hbar(2))
+
+    tx.freeze_with(mock_client)  # Serlize  to_bytes()
+    data = tx.to_bytes()
+
+    restored = TransferTransaction.from_bytes(data)  # Deserialize from_bytes().
+    assert restored._transaction_fee == Hbar(2).to_tinybars()

From a5d1bfcac52c42f0f54e685a4e315b1207703f7d Mon Sep 17 00:00:00 2001
From: tech0priyanshu <priyanshuyadv101106@gmail.com>
Date: Tue, 25 Aug 2026 11:36:24 +0530
Subject: [PATCH 2/9] add client to set max transaction fee in Transaction
 class

Signed-off-by: tech0priyanshu <priyanshuyadv101106@gmail.com>
---
 src/hiero_sdk_python/transaction/transaction.py | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/src/hiero_sdk_python/transaction/transaction.py b/src/hiero_sdk_python/transaction/transaction.py
index 99a3ec254..83486235b 100644
--- a/src/hiero_sdk_python/transaction/transaction.py
+++ b/src/hiero_sdk_python/transaction/transaction.py
@@ -65,6 +65,7 @@ def __init__(self) -> None:
         self._default_transaction_fee = Hbar(2)
         self.operator_account_id = None
         self.batch_key: Key | None = None
+        self._client: Client | None = None
 
     def _make_request(self):
         """
@@ -302,6 +303,7 @@ def freeze_with(self, client: Client):
             return self
 
         # Resolve transaction_id and node_accountids to be set when using freeze()
+        self._client = client
         self._resolve_transaction_id(client)
         self._resolve_node_ids(client)
 
@@ -508,8 +510,16 @@ def build_base_transaction_body(self) -> transaction_pb2.TransactionBody:
             ValueError: If required IDs are not set.
         """
         transaction_body = transaction_pb2.TransactionBody()
+        transaction_body.transactionID.CopyFrom(transaction_id_proto)
+        transaction_body.nodeAccountID.CopyFrom(selected_node._to_proto())
 
-        fee = self._transaction_fee if self._transaction_fee is not None else self._default_transaction_fee
+        if self._transaction_fee is None:
+            if self._client is not None and self._client.default_max_transaction_fee is not None:
+                self.transaction_fee = self._client.default_max_transaction_fee
+            else:
+                self.transaction_fee = self._default_transaction_fee
+
+        fee = self._transaction_fee
         if hasattr(fee, "to_tinybars"):
             transaction_body.transactionFee = int(fee.to_tinybars())
         else:

From c490cdd15801293aad36a08824f5aa3822087272 Mon Sep 17 00:00:00 2001
From: exploreriii <133720349+exploreriii@users.noreply.github.com>
Date: Wed, 26 Aug 2026 12:36:20 +0100
Subject: [PATCH 3/9] fix: remove default transaction fee from client freeze
 with, instead locate it in resolve transaction fee

Signed-off-by: exploreriii <133720349+exploreriii@users.noreply.github.com>
Signed-off-by: tech0priyanshu <priyanshuyadv101106@gmail.com>
---
 .../transaction/transaction.py                | 24 +++++++++++--------
 1 file changed, 14 insertions(+), 10 deletions(-)

diff --git a/src/hiero_sdk_python/transaction/transaction.py b/src/hiero_sdk_python/transaction/transaction.py
index 83486235b..c03d25c9c 100644
--- a/src/hiero_sdk_python/transaction/transaction.py
+++ b/src/hiero_sdk_python/transaction/transaction.py
@@ -65,7 +65,6 @@ def __init__(self) -> None:
         self._default_transaction_fee = Hbar(2)
         self.operator_account_id = None
         self.batch_key: Key | None = None
-        self._client: Client | None = None
 
     def _make_request(self):
         """
@@ -266,6 +265,17 @@ def _resolve_node_ids(self, client: Client):
         if self._node_account_ids.is_empty:
             self._node_account_ids.set_list([node._account_id for node in client.network.nodes])
 
+    def _resolve_transaction_fee(self, client: Client | None) -> None:
+        """Resolve the max transaction fee: explicit fee, else client default, else per-type default."""
+        if self._transaction_fee is not None:
+            return
+
+        default = client.default_max_transaction_fee if client is not None else None
+        if not isinstance(default, Hbar):
+            default = None
+
+        self.transaction_fee = default if default is not None else self._default_transaction_fee
+
     def freeze(self):
         """
         Freezes the transaction by building the transaction body and setting necessary IDs.
@@ -303,9 +313,9 @@ def freeze_with(self, client: Client):
             return self
 
         # Resolve transaction_id and node_accountids to be set when using freeze()
-        self._client = client
         self._resolve_transaction_id(client)
         self._resolve_node_ids(client)
+        self._resolve_transaction_fee(client)
 
         required_chunks = self.get_required_chunks()
         self._generate_transaction_ids(self._transaction_ids.get(0), required_chunks)
@@ -513,14 +523,8 @@ def build_base_transaction_body(self) -> transaction_pb2.TransactionBody:
         transaction_body.transactionID.CopyFrom(transaction_id_proto)
         transaction_body.nodeAccountID.CopyFrom(selected_node._to_proto())
 
-        if self._transaction_fee is None:
-            if self._client is not None and self._client.default_max_transaction_fee is not None:
-                self.transaction_fee = self._client.default_max_transaction_fee
-            else:
-                self.transaction_fee = self._default_transaction_fee
-
-        fee = self._transaction_fee
-        if hasattr(fee, "to_tinybars"):
+        fee = self._transaction_fee if self._transaction_fee is not None else self._default_transaction_fee
+        if isinstance(fee, Hbar):
             transaction_body.transactionFee = int(fee.to_tinybars())
         else:
             transaction_body.transactionFee = int(fee)

From 907d9b0c9ef0ca4bd48b05191a03bff457af28a8 Mon Sep 17 00:00:00 2001
From: exploreriii <133720349+exploreriii@users.noreply.github.com>
Date: Wed, 26 Aug 2026 12:36:53 +0100
Subject: [PATCH 4/9] fix: fallback to true defaults max transaction fee, which
 doesn't need to be specified in tests

Signed-off-by: exploreriii <133720349+exploreriii@users.noreply.github.com>
Signed-off-by: tech0priyanshu <priyanshuyadv101106@gmail.com>
---
 tests/unit/fee_estimate_query_test.py           |  5 -----
 tests/unit/file_append_transaction_test.py      |  2 --
 tests/unit/transaction_freeze_and_bytes_test.py | 12 ++++++++++++
 3 files changed, 12 insertions(+), 7 deletions(-)

diff --git a/tests/unit/fee_estimate_query_test.py b/tests/unit/fee_estimate_query_test.py
index 582bcef81..6b6d253af 100644
--- a/tests/unit/fee_estimate_query_test.py
+++ b/tests/unit/fee_estimate_query_test.py
@@ -32,7 +32,6 @@ def mock_client():
     client.mirror_network = "https://testnet.mirrornode.hedera.com"
     client.max_retries = 3
 
-    client.default_max_transaction_fee = Hbar(2)
     client.generate_transaction_id.return_value = TransactionId.generate(AccountId(0, 0, 1001))
     client.operator_account_id._to_proto.return_value = AccountId(0, 0, 1)._to_proto()
 
@@ -338,7 +337,6 @@ def test_port_replacement_for_localhost_execute_single():
     """Test localhost:38081 is replaced with :8084."""
     client_1 = MagicMock()
     client_1.network.get_mirror_rest_url.return_value = "http://localhost:38081/api/v1"
-    client_1.default_max_transaction_fee = Hbar(1)
 
     tx = (
         TransferTransaction()
@@ -356,7 +354,6 @@ def test_port_replacement_for_localhost_execute_single():
 
     client_2 = MagicMock()
     client_2.network.get_mirror_rest_url.return_value = "http://127.0.0.1:38081/api/v1"
-    client_2.default_max_transaction_fee = Hbar(1)
 
     with patch.object(query, "_execute_single") as mock_execute_single:
         query.execute(client_2)
@@ -369,7 +366,6 @@ def test_port_replacement_for_localhost_execute_multiple():
     """Test localhost:38081 is replaced with :8084 for chunked tx."""
     client_1 = MagicMock()
     client_1.network.get_mirror_rest_url.return_value = "http://localhost:38081/api/v1"
-    client_1.default_max_transaction_fee = Hbar(1)
 
     tx = (
         TopicMessageSubmitTransaction()
@@ -392,7 +388,6 @@ def test_port_replacement_for_localhost_execute_multiple():
 
     client_2 = MagicMock()
     client_2.network.get_mirror_rest_url.return_value = "http://127.0.0.1:38081/api/v1"
-    client_2.default_max_transaction_fee = Hbar(1)
 
     with patch.object(query, "_execute_chunked", return_value=MagicMock()) as mock_execute_chunked:
         query.execute(client_2)
diff --git a/tests/unit/file_append_transaction_test.py b/tests/unit/file_append_transaction_test.py
index 54d9fe93e..4aa83a186 100644
--- a/tests/unit/file_append_transaction_test.py
+++ b/tests/unit/file_append_transaction_test.py
@@ -99,7 +99,6 @@ def test_freeze_with_generates_transaction_ids():
 
     # Mock client and transaction_id
     mock_client = MagicMock()
-    mock_client.default_max_transaction_fee = Hbar(1)
     mock_transaction_id = TransactionId(account_id=MagicMock(), valid_start=Timestamp(0, 1))
     file_tx.transaction_id = mock_transaction_id
 
@@ -142,7 +141,6 @@ def test_multi_chunk_execution():
 
     # Mock client and responses
     mock_client = MagicMock()
-    mock_client.default_max_transaction_fee = Hbar(1)
     mock_receipt = MagicMock(spec=TransactionReceipt)
     mock_receipt.status = ResponseCode.SUCCESS
 
diff --git a/tests/unit/transaction_freeze_and_bytes_test.py b/tests/unit/transaction_freeze_and_bytes_test.py
index f1aae0bce..55f615474 100644
--- a/tests/unit/transaction_freeze_and_bytes_test.py
+++ b/tests/unit/transaction_freeze_and_bytes_test.py
@@ -9,6 +9,7 @@
 from __future__ import annotations
 
 from decimal import Decimal
+from unittest.mock import MagicMock
 
 import pytest
 
@@ -820,3 +821,14 @@ def test_max_transaction_fee_survives_to_bytes_round_trip(mock_client):
 
     restored = TransferTransaction.from_bytes(data)  # Deserialize from_bytes().
     assert restored._transaction_fee == Hbar(2).to_tinybars()
+
+
+def test_freeze_with_bare_magicmock_client_resolves_default_fee():
+    """Freezing against a bare MagicMock client must not raise and must fall back to the per-type default fee."""
+    tx = TransferTransaction()
+    tx.set_transaction_id(TransactionId.generate(AccountId.from_string("0.0.1234")))
+    tx.set_node_account_ids([AccountId.from_string("0.0.3")])
+
+    tx.freeze_with(MagicMock())
+
+    assert tx.transaction_fee == 100_000_000  # TransferTransaction per-type default, Hbar(1)

From 671a0545e9bd53703c6ab1114b90eb8e00421dbe Mon Sep 17 00:00:00 2001
From: exploreriii <133720349+exploreriii@users.noreply.github.com>
Date: Wed, 26 Aug 2026 12:42:39 +0100
Subject: [PATCH 5/9] fix: rename set_default_max_transaction_fee to
 set_max_transaction_fee as it sets max transaction fee for a transaction, not
 its default

Signed-off-by: exploreriii <133720349+exploreriii@users.noreply.github.com>
Signed-off-by: tech0priyanshu <priyanshuyadv101106@gmail.com>
---
 .../transaction/transaction.py                | 25 ++++++++-----------
 .../account_update_transaction_e2e_test.py    |  2 +-
 .../unit/transaction_freeze_and_bytes_test.py | 18 ++++++-------
 3 files changed, 20 insertions(+), 25 deletions(-)

diff --git a/src/hiero_sdk_python/transaction/transaction.py b/src/hiero_sdk_python/transaction/transaction.py
index c03d25c9c..545c80217 100644
--- a/src/hiero_sdk_python/transaction/transaction.py
+++ b/src/hiero_sdk_python/transaction/transaction.py
@@ -1,6 +1,7 @@
 from __future__ import annotations
 
 import hashlib
+from decimal import Decimal
 from typing import TYPE_CHECKING, Literal, overload
 
 from hiero_sdk_python.account.account_id import AccountId
@@ -851,30 +852,24 @@ def from_bytes(transaction_bytes: bytes):
             transaction_body, signed_transaction.bodyBytes, signed_transaction.sigMap
         )
 
-    def set_default_max_transaction_fee(self, max_transaction_fee):
+    def set_max_transaction_fee(self, max_transaction_fee: int | float | Decimal | Hbar) -> Transaction:
         """
-         Sets the maximum transaction fee for this transaction.
-
-        The maximum transaction fee specifies the highest fee that can be
-        charged when the transaction is executed. The value must be
-        non-negative.
+        Set the maximum transaction fee the payer is willing to pay for this transaction.
 
         Args:
-             max_transaction_fee (Hbar | int | str): The maximum transaction
-             fee. Accepted types are those supported by ``Hbar._coerce_fee``.
+            max_transaction_fee (int | float | Decimal | Hbar): The maximum fee.
+                Numeric values are interpreted as Hbar.
 
         Returns:
-            Self: This transaction instance, allowing method chaining.
+            Transaction: This transaction instance for method chaining.
 
         Raises:
-            ValueError: If ``max_transaction_fee`` is negative.
-            RuntimeError: If the transaction has been frozen.
+            TypeError: If the value is not int, float, Decimal, or Hbar.
+            ValueError: If the value is negative.
+            Exception: If the transaction has already been frozen.
         """
         self._require_not_frozen()
-        value = Hbar._coerce_fee(max_transaction_fee)
-        if value < Hbar.ZERO:
-            raise ValueError("max_transaction_fee must be non-negative")
-        self.transaction_fee = value
+        self.transaction_fee = Hbar._coerce_non_negative(max_transaction_fee, "max_transaction_fee")
         return self
 
     @staticmethod
diff --git a/tests/integration/account_update_transaction_e2e_test.py b/tests/integration/account_update_transaction_e2e_test.py
index ff2b046a2..3e7d32d1e 100644
--- a/tests/integration/account_update_transaction_e2e_test.py
+++ b/tests/integration/account_update_transaction_e2e_test.py
@@ -242,7 +242,7 @@ def test_integration_account_update_transaction_invalid_auto_renew_period(env):
 
 def _apply_tiny_max_fee_if_supported(tx, client) -> bool:
     # Try tx-level setters
-    for attr in ("set_default_max_transaction_fee", "set_max_fee", "set_transaction_fee"):
+    for attr in ("set_max_transaction_fee", "set_max_fee", "set_transaction_fee"):
         if hasattr(tx, attr):
             getattr(tx, attr)(Hbar.from_tinybars(1))
             return True
diff --git a/tests/unit/transaction_freeze_and_bytes_test.py b/tests/unit/transaction_freeze_and_bytes_test.py
index 55f615474..c1b2589dd 100644
--- a/tests/unit/transaction_freeze_and_bytes_test.py
+++ b/tests/unit/transaction_freeze_and_bytes_test.py
@@ -82,30 +82,30 @@ def test_freeze_with_valid_parameters():
     ],
 )
 def test_set_max_transaction_fee_valid_param(valid_amount, expected):
-    """Transaction.set_default_max_transaction_fee should accept various numeric types and Hbar."""
+    """Transaction.set_max_transaction_fee should accept various numeric types and Hbar."""
     tx = TransferTransaction()
 
-    returned = tx.set_default_max_transaction_fee(valid_amount)
+    returned = tx.set_max_transaction_fee(valid_amount)
     assert tx.transaction_fee == expected
     assert returned is tx
 
 
 @pytest.mark.parametrize("invalid_amount", ["1", True, False, None, object()])
 def test_set_max_transaction_fee_invalid_param(invalid_amount):
-    """Transaction.set_default_max_transaction_fee should reject invalid types."""
+    """Transaction.set_max_transaction_fee should reject invalid types."""
     tx = TransferTransaction()
 
     with pytest.raises(TypeError):
-        tx.set_default_max_transaction_fee(invalid_amount)
+        tx.set_max_transaction_fee(invalid_amount)
 
 
 @pytest.mark.parametrize("negative_amount", [-1, -0.1, Decimal("-0.1"), Hbar(-1)])
 def test_set_max_transaction_fee_negative_value(negative_amount):
-    """Transaction.set_default_max_transaction_fee should reject negative values."""
+    """Transaction.set_max_transaction_fee should reject negative values."""
     tx = TransferTransaction()
 
     with pytest.raises(ValueError):
-        tx.set_default_max_transaction_fee(negative_amount)
+        tx.set_max_transaction_fee(negative_amount)
     # checking state un modified
     assert len(tx._transaction_body_bytes) == 0
 
@@ -763,7 +763,7 @@ def test_map_response_raises_if_proto_request_is_not_transaction():
 def test_fee_resolution_transaction_precedence(mock_client):
     """Transaction fee explicitly set should take precedence over client default."""
     tx = TransferTransaction()
-    tx.set_default_max_transaction_fee(Hbar(10))
+    tx.set_max_transaction_fee(Hbar(10))
 
     # client has different default
     mock_client.set_default_max_transaction_fee(Hbar(5))
@@ -803,7 +803,7 @@ def test_resolved_fee_serialized_into_transaction_body(mock_client):
     """The resolved fee must reach the serialized proto transactionFee."""
     tx = TransferTransaction()
 
-    tx.set_default_max_transaction_fee(Hbar(2))
+    tx.set_max_transaction_fee(Hbar(2))
 
     body = tx.build_base_scheduled_body()
 
@@ -814,7 +814,7 @@ def test_max_transaction_fee_survives_to_bytes_round_trip(mock_client):
     """An explicitly set max fee must survive a to_bytes -> from_bytes round trip."""
     tx = TransferTransaction()
 
-    tx.set_default_max_transaction_fee(Hbar(2))
+    tx.set_max_transaction_fee(Hbar(2))
 
     tx.freeze_with(mock_client)  # Serlize  to_bytes()
     data = tx.to_bytes()

From e2469636cba7a6bed2502fb06993a3aa2d789dae Mon Sep 17 00:00:00 2001
From: exploreriii <133720349+exploreriii@users.noreply.github.com>
Date: Wed, 26 Aug 2026 12:43:33 +0100
Subject: [PATCH 6/9] refactor: use _coerce_non_negative instead of duplicating
 in client

Signed-off-by: exploreriii <133720349+exploreriii@users.noreply.github.com>
Signed-off-by: tech0priyanshu <priyanshuyadv101106@gmail.com>
---
 src/hiero_sdk_python/client/client.py | 17 +++--------------
 src/hiero_sdk_python/hbar.py          | 20 ++++++++++++++------
 2 files changed, 17 insertions(+), 20 deletions(-)

diff --git a/src/hiero_sdk_python/client/client.py b/src/hiero_sdk_python/client/client.py
index 3a9329223..29e9f3895 100644
--- a/src/hiero_sdk_python/client/client.py
+++ b/src/hiero_sdk_python/client/client.py
@@ -278,16 +278,7 @@ def set_default_max_query_payment(self, max_query_payment: int | float | Decimal
         Returns:
             Client: The current client instance for method chaining.
         """
-        if isinstance(max_query_payment, bool) or not isinstance(max_query_payment, (int, float, Decimal, Hbar)):
-            raise TypeError(
-                f"max_query_payment must be int, float, Decimal, or Hbar, got {type(max_query_payment).__name__}"
-            )
-
-        value = max_query_payment if isinstance(max_query_payment, Hbar) else Hbar(max_query_payment)
-
-        if value < Hbar(0):
-            raise ValueError("max_query_payment must be non-negative")
-
+        value = Hbar._coerce_non_negative(max_query_payment, "max_query_payment")
         self.default_max_query_payment = value
         return self
 
@@ -296,11 +287,9 @@ def set_default_max_transaction_fee(
         max_transaction_fee: int | float | Decimal | Hbar,
     ) -> Client:
         """
-        Sets the default maximum Hbar fee allowed for any  transaction executed by this client.
+        Sets the default maximum Hbar fee allowed for any transaction executed by this client.
         """
-        value = Hbar._coerce_fee(max_transaction_fee)
-        if value < Hbar.ZERO:
-            raise ValueError("max_transaction_fee must be non-negative")
+        value = Hbar._coerce_non_negative(max_transaction_fee, "max_transaction_fee")
         self.default_max_transaction_fee = value
         return self
 
diff --git a/src/hiero_sdk_python/hbar.py b/src/hiero_sdk_python/hbar.py
index cc58b5d2a..18edf3d20 100644
--- a/src/hiero_sdk_python/hbar.py
+++ b/src/hiero_sdk_python/hbar.py
@@ -84,19 +84,27 @@ def negated(self) -> Hbar:
         return Hbar.from_tinybars(-self._amount_in_tinybar)
 
     @staticmethod
-    def _coerce_fee(value: int | float | Decimal | Hbar) -> Hbar:
+    def _coerce_non_negative(value: int | float | Decimal | Hbar, name: str = "value") -> Hbar:
         """
-        Coerce a value to an Hbar instance. Accepts int, float, Decimal, or Hbar (but not bool).
+        Coerce a value to a non-negative Hbar. Accepts int, float, Decimal, or Hbar (but not bool).
+
         Args:
             value: The value to coerce.
+            name: The field name used in error messages. Defaults to "value".
+
         Returns:
-            Hbar: An Hbar instance.
+            Hbar: A non-negative Hbar instance.
+
         Raises:
-            TypeError: If value is not a valid type.
+            TypeError: If value is not int, float, Decimal, or Hbar.
+            ValueError: If value is negative.
         """
         if isinstance(value, bool) or not isinstance(value, (int, float, Decimal, Hbar)):
-            raise TypeError(f"value must be int, float, Decimal, or Hbar, got {type(value).__name__}")
-        return value if isinstance(value, Hbar) else Hbar(value)
+            raise TypeError(f"{name} must be int, float, Decimal, or Hbar, got {type(value).__name__}")
+        result = value if isinstance(value, Hbar) else Hbar(value)
+        if result < Hbar.ZERO:
+            raise ValueError(f"{name} must be non-negative")
+        return result
 
     @classmethod
     def of(cls, amount: int | float | Decimal, unit: HbarUnit) -> Hbar:

From 4b44a3eed8d062d75d4583eb635be27b6214a36c Mon Sep 17 00:00:00 2001
From: exploreriii <133720349+exploreriii@users.noreply.github.com>
Date: Wed, 26 Aug 2026 12:47:35 +0100
Subject: [PATCH 7/9] fix: honor explicit zero fee in scheduled bodies

Signed-off-by: exploreriii <133720349+exploreriii@users.noreply.github.com>
Signed-off-by: tech0priyanshu <priyanshuyadv101106@gmail.com>
---
 src/hiero_sdk_python/transaction/transaction.py |  4 ++--
 tests/unit/transaction_freeze_and_bytes_test.py | 15 +++++++++++++++
 2 files changed, 17 insertions(+), 2 deletions(-)

diff --git a/src/hiero_sdk_python/transaction/transaction.py b/src/hiero_sdk_python/transaction/transaction.py
index 545c80217..2da12b56a 100644
--- a/src/hiero_sdk_python/transaction/transaction.py
+++ b/src/hiero_sdk_python/transaction/transaction.py
@@ -552,8 +552,8 @@ def build_base_scheduled_body(self) -> SchedulableTransactionBody:
         """
         schedulable_body = SchedulableTransactionBody()
 
-        fee = self._transaction_fee or self._default_transaction_fee
-        if hasattr(fee, "to_tinybars"):
+        fee = self._transaction_fee if self._transaction_fee is not None else self._default_transaction_fee
+        if isinstance(fee, Hbar):
             schedulable_body.transactionFee = int(fee.to_tinybars())
         else:
             schedulable_body.transactionFee = int(fee)
diff --git a/tests/unit/transaction_freeze_and_bytes_test.py b/tests/unit/transaction_freeze_and_bytes_test.py
index c1b2589dd..41f7a3970 100644
--- a/tests/unit/transaction_freeze_and_bytes_test.py
+++ b/tests/unit/transaction_freeze_and_bytes_test.py
@@ -15,6 +15,7 @@
 
 from hiero_sdk_python.account.account_id import AccountId
 from hiero_sdk_python.crypto.private_key import PrivateKey
+from hiero_sdk_python.hapi.services import transaction_pb2
 from hiero_sdk_python.hapi.services.transaction_response_pb2 import (
     TransactionResponse as TransactionResponseProto,
 )
@@ -823,6 +824,20 @@ def test_max_transaction_fee_survives_to_bytes_round_trip(mock_client):
     assert restored._transaction_fee == Hbar(2).to_tinybars()
 
 
+def test_explicit_zero_fee_is_honored_on_direct_and_scheduled_paths(mock_client):
+    """An explicit zero fee must reach both the direct and the scheduled body unchanged."""
+    tx = TransferTransaction()
+    tx.set_max_transaction_fee(Hbar(0))
+
+    scheduled_body = tx.build_base_scheduled_body()
+    assert scheduled_body.transactionFee == 0
+
+    tx.freeze_with(mock_client)
+    body = transaction_pb2.TransactionBody()
+    body.ParseFromString(next(iter(tx._transaction_body_bytes.values())))
+    assert body.transactionFee == 0
+
+
 def test_freeze_with_bare_magicmock_client_resolves_default_fee():
     """Freezing against a bare MagicMock client must not raise and must fall back to the per-type default fee."""
     tx = TransferTransaction()

From e0122c270dc4733b228c648c2d7e3d166aff0751 Mon Sep 17 00:00:00 2001
From: exploreriii <133720349+exploreriii@users.noreply.github.com>
Date: Wed, 26 Aug 2026 12:49:53 +0100
Subject: [PATCH 8/9] fix: duplicate set_default_max_transaction_fee in e2e
 test and improve test surface area to check default is applied if not set

Signed-off-by: exploreriii <133720349+exploreriii@users.noreply.github.com>
Signed-off-by: tech0priyanshu <priyanshuyadv101106@gmail.com>
---
 .../account_update_transaction_e2e_test.py    | 24 ++++++++++++++++++-
 1 file changed, 23 insertions(+), 1 deletion(-)

diff --git a/tests/integration/account_update_transaction_e2e_test.py b/tests/integration/account_update_transaction_e2e_test.py
index 3e7d32d1e..80dc4d536 100644
--- a/tests/integration/account_update_transaction_e2e_test.py
+++ b/tests/integration/account_update_transaction_e2e_test.py
@@ -248,7 +248,6 @@ def _apply_tiny_max_fee_if_supported(tx, client) -> bool:
             return True
     # Try client-level default
     for attr in (
-        "set_default_max_transaction_fee",
         "set_default_max_transaction_fee",
         "set_default_max_fee",
         "setMaxTransactionFee",
@@ -295,6 +294,29 @@ def test_account_update_insufficient_fee_with_valid_expiration_bump(env):
     assert int(info_after.expiration_time.seconds) == base_expiry_secs
 
 
+@pytest.mark.integration
+def test_account_update_insufficient_fee_via_client_default(env):
+    """A client-level default max fee must apply to transactions that set no explicit fee."""
+    receipt = (
+        AccountCreateTransaction()
+        .set_key(env.operator_key.public_key())
+        .set_initial_balance(Hbar(1))
+        .execute(env.client)
+    )
+    assert receipt.status == ResponseCode.SUCCESS
+    account_id = receipt.account_id
+
+    env.client.set_default_max_transaction_fee(Hbar.from_tinybars(1))
+
+    # No tx-level fee: the 1-tinybar client default must be resolved at freeze and rejected at precheck.
+    tx = AccountUpdateTransaction().set_account_id(account_id).set_account_memo("client default fee test")
+
+    with pytest.raises(PrecheckError) as exc_info:
+        tx.execute(env.client)
+
+    assert exc_info.value.status == ResponseCode.INSUFFICIENT_TX_FEE
+
+
 @pytest.mark.integration
 def test_integration_account_update_transaction_with_only_account_id(env):
     """Test that AccountUpdateTransaction can execute with only account ID set."""

From afe0bc0aab7fe9731ac04d26ea26763fdda81a38 Mon Sep 17 00:00:00 2001
From: tech0priyanshu <priyanshuyadv101106@gmail.com>
Date: Tue, 29 Sep 2026 23:26:49 +0530
Subject: [PATCH 9/9] fix: update transaction fee handling and improve error
 messages for invalid types

Signed-off-by: tech0priyanshu <priyanshuyadv101106@gmail.com>
---
 .../transaction/transaction.py                | 35 ++++++-------------
 .../unit/transaction_freeze_and_bytes_test.py | 12 +++++--
 tests/unit/transaction_test.py                |  6 ++--
 3 files changed, 23 insertions(+), 30 deletions(-)

diff --git a/src/hiero_sdk_python/transaction/transaction.py b/src/hiero_sdk_python/transaction/transaction.py
index 2da12b56a..baddc7d25 100644
--- a/src/hiero_sdk_python/transaction/transaction.py
+++ b/src/hiero_sdk_python/transaction/transaction.py
@@ -275,7 +275,10 @@ def _resolve_transaction_fee(self, client: Client | None) -> None:
         if not isinstance(default, Hbar):
             default = None
 
-        self.transaction_fee = default if default is not None else self._default_transaction_fee
+        if default is not None:
+            self.transaction_fee = default
+        else:
+            self._transaction_fee = self._default_transaction_fee
 
     def freeze(self):
         """
@@ -521,8 +524,6 @@ def build_base_transaction_body(self) -> transaction_pb2.TransactionBody:
             ValueError: If required IDs are not set.
         """
         transaction_body = transaction_pb2.TransactionBody()
-        transaction_body.transactionID.CopyFrom(transaction_id_proto)
-        transaction_body.nodeAccountID.CopyFrom(selected_node._to_proto())
 
         fee = self._transaction_fee if self._transaction_fee is not None else self._default_transaction_fee
         if isinstance(fee, Hbar):
@@ -696,19 +697,7 @@ def transaction_fee(self, fee: Hbar | int):
         """
         Set the maximum transaction fee for this transaction.
         """
-        self._require_not_frozen()
-
-        if isinstance(fee, Hbar):
-            tinybars = fee.to_tinybars()
-        elif isinstance(fee, bool) or not isinstance(fee, int):
-            raise TypeError("fee must be of type Hbar or int")
-        else:
-            tinybars = fee
-
-        if tinybars < 0:
-            raise ValueError("fee must be greater than or equal to 0")
-
-        self._transaction_fee = tinybars
+        self.set_max_transaction_fee(fee)
 
     def to_bytes(self) -> bytes:
         """
@@ -861,15 +850,14 @@ def set_max_transaction_fee(self, max_transaction_fee: int | float | Decimal | H
                 Numeric values are interpreted as Hbar.
 
         Returns:
-            Transaction: This transaction instance for method chaining.
-
+        Transaction: This transaction instance for method chaining.
         Raises:
-            TypeError: If the value is not int, float, Decimal, or Hbar.
-            ValueError: If the value is negative.
-            Exception: If the transaction has already been frozen.
+        TypeError: If the value is not int, float, Decimal, or Hbar.
+        ValueError: If the value is negative.
+        Exception: If the transaction has already been frozen.
         """
         self._require_not_frozen()
-        self.transaction_fee = Hbar._coerce_non_negative(max_transaction_fee, "max_transaction_fee")
+        self._transaction_fee = Hbar._coerce_non_negative(max_transaction_fee, "max_transaction_fee").to_tinybars()
         return self
 
     @staticmethod
@@ -977,7 +965,7 @@ def _from_protobuf(cls, transaction_body, body_bytes: bytes, sig_map):
         if transaction_body.HasField("nodeAccountID"):
             transaction._node_account_ids.set_list([AccountId._from_proto(transaction_body.nodeAccountID)])
 
-        transaction.transaction_fee = transaction_body.transactionFee
+        transaction._transaction_fee = transaction_body.transactionFee
         transaction.transaction_valid_duration = transaction_body.transactionValidDuration.seconds
         transaction.generate_record = transaction_body.generateRecord
         transaction._high_volume = transaction_body.high_volume
@@ -1002,7 +990,6 @@ def _from_protobuf(cls, transaction_body, body_bytes: bytes, sig_map):
 
         if sig_map and sig_map.sigPair:
             transaction._signature_map[body_bytes] = sig_map
-
         return transaction
 
     def set_batch_key(self, key: Key):
diff --git a/tests/unit/transaction_freeze_and_bytes_test.py b/tests/unit/transaction_freeze_and_bytes_test.py
index 41f7a3970..ebf10b6d0 100644
--- a/tests/unit/transaction_freeze_and_bytes_test.py
+++ b/tests/unit/transaction_freeze_and_bytes_test.py
@@ -414,7 +414,7 @@ def test_from_bytes_preserves_all_common_fields():
 
     transaction.transaction_id = TransactionId.generate(operator_id)
     transaction.set_node_account_ids([node_id])
-    transaction.transaction_fee = 5_000_000  # Custom fee
+    transaction._transaction_fee = 5_000_000  # Custom fee
     assert transaction.set_transaction_valid_duration(180) is transaction  # 3 minutes - using setter
     transaction.generate_record = True
 
@@ -825,7 +825,7 @@ def test_max_transaction_fee_survives_to_bytes_round_trip(mock_client):
 
 
 def test_explicit_zero_fee_is_honored_on_direct_and_scheduled_paths(mock_client):
-    """An explicit zero fee must reach both the direct and the scheduled body unchanged."""
+    """An explicit zero fee must reach both the direct and scheduled body unchanged."""
     tx = TransferTransaction()
     tx.set_max_transaction_fee(Hbar(0))
 
@@ -833,8 +833,14 @@ def test_explicit_zero_fee_is_honored_on_direct_and_scheduled_paths(mock_client)
     assert scheduled_body.transactionFee == 0
 
     tx.freeze_with(mock_client)
+
+    transaction_id = tx._transaction_ids.current
+    node_account_id = tx._node_account_ids.current
+    body_bytes = tx._transaction_body_bytes[transaction_id][node_account_id]
+
     body = transaction_pb2.TransactionBody()
-    body.ParseFromString(next(iter(tx._transaction_body_bytes.values())))
+    body.ParseFromString(body_bytes)
+
     assert body.transactionFee == 0
 
 
diff --git a/tests/unit/transaction_test.py b/tests/unit/transaction_test.py
index 59205563b..595a8946b 100644
--- a/tests/unit/transaction_test.py
+++ b/tests/unit/transaction_test.py
@@ -564,7 +564,7 @@ def test_transaction_fee_rejects_bool():
     """Test transaction_fee rejects boolean values."""
     tx = AccountCreateTransaction()
 
-    with pytest.raises(TypeError, match="fee must be of type Hbar or int"):
+    with pytest.raises(TypeError, match="transaction_fee must be int, float, Decimal, or Hbar, got bool"):
         tx.transaction_fee = True
 
 
@@ -572,7 +572,7 @@ def test_transaction_fee_rejects_invalid_type():
     """Test transaction_fee rejects invalid types."""
     tx = AccountCreateTransaction()
 
-    with pytest.raises(TypeError, match="fee must be of type Hbar or int"):
+    with pytest.raises(TypeError, match="transaction_fee must be int, float, Decimal, or Hbar, got str"):
         tx.transaction_fee = "100"
 
 
@@ -580,7 +580,7 @@ def test_transaction_fee_rejects_negative_int():
     """Test transaction_fee rejects negative integer values."""
     tx = AccountCreateTransaction()
 
-    with pytest.raises(ValueError, match="fee must be greater than or equal to 0"):
+    with pytest.raises(ValueError, match="transaction_fee must be non-negative"):
         tx.transaction_fee = -1