diff --git a/python/x402/changelog.d/tvm-jetton-tests.misc.md b/python/x402/changelog.d/tvm-jetton-tests.misc.md
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+++ b/python/x402/changelog.d/tvm-jetton-tests.misc.md
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+Add 27 unit tests for `mechanisms/tvm/codecs/jetton.py` — the only TVM codec source file without a dedicated test module. Covers `build_jetton_transfer_body_fields` (opcode, coins, address, response destination, custom-payload bit, forward ton amount, forward payload ref), `build_jetton_transfer_body` (requirements delegation, string-to-int amount coercion), and `parse_jetton_transfer` (round-trip field extraction, source wallet, body hash, error paths for wrong opcode / custom-payload-bit-set / null destination, forward payload from ref vs slice).
diff --git a/python/x402/tests/unit/mechanisms/tvm/test_jetton.py b/python/x402/tests/unit/mechanisms/tvm/test_jetton.py
new file mode 100644
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+++ b/python/x402/tests/unit/mechanisms/tvm/test_jetton.py
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+"""Unit tests for TVM jetton codec helpers."""
+
+from __future__ import annotations
+
+import base64
+
+import pytest
+
+pytest.importorskip("pytoniq_core")
+
+from pytoniq_core import Address, begin_cell
+
+from x402.mechanisms.tvm.codecs.common import normalize_address
+from x402.mechanisms.tvm.codecs.jetton import (
+    build_jetton_transfer_body,
+    build_jetton_transfer_body_fields,
+    parse_jetton_transfer,
+)
+from x402.mechanisms.tvm.constants import (
+    ERR_EXACT_TVM_INVALID_JETTON_TRANSFER,
+    JETTON_TRANSFER_OPCODE,
+)
+
+from .builders import make_tvm_requirements
+
+DESTINATION = "0:" + "d" * 64
+RESPONSE_DEST = "0:" + "e" * 64
+JETTON_WALLET = "0:" + "4" * 64
+
+
+def _raw_transfer_body(
+    *,
+    opcode: int = JETTON_TRANSFER_OPCODE,
+    amount: int = 100,
+    destination: str | None = DESTINATION,
+    response_destination: str | None = None,
+    custom_payload_bit: bool = False,
+    forward_ton_amount: int = 0,
+    forward_payload_bit: bool = False,
+) -> object:
+    """Build a raw TEP-74 transfer cell allowing edge-case values."""
+    builder = (
+        begin_cell()
+        .store_uint(opcode, 32)
+        .store_uint(0, 64)
+        .store_coins(amount)
+        .store_address(Address(destination) if destination else None)
+        .store_address(Address(response_destination) if response_destination else None)
+        .store_bit(1 if custom_payload_bit else 0)
+        .store_coins(forward_ton_amount)
+        .store_bit(1 if forward_payload_bit else 0)
+    )
+    if forward_payload_bit:
+        builder = builder.store_ref(begin_cell().store_uint(0xAB, 8).end_cell())
+    return builder.end_cell()
+
+
+class TestBuildJettonTransferBodyFields:
+    def test_opcode_stored_as_first_32_bits(self):
+        cell = build_jetton_transfer_body_fields(
+            amount=1, pay_to=DESTINATION, extra={"forwardTonAmount": "0"}
+        )
+        s = cell.begin_parse()
+        assert s.load_uint(32) == JETTON_TRANSFER_OPCODE
+
+    def test_amount_stored_as_coins(self):
+        cell = build_jetton_transfer_body_fields(
+            amount=999, pay_to=DESTINATION, extra={"forwardTonAmount": "0"}
+        )
+        s = cell.begin_parse()
+        s.load_uint(32)
+        s.load_uint(64)
+        assert s.load_coins() == 999
+
+    def test_destination_stored_as_address(self):
+        cell = build_jetton_transfer_body_fields(
+            amount=1, pay_to=DESTINATION, extra={"forwardTonAmount": "0"}
+        )
+        s = cell.begin_parse()
+        s.load_uint(32)
+        s.load_uint(64)
+        s.load_coins()
+        addr = s.load_address()
+        assert normalize_address(addr) == normalize_address(DESTINATION)
+
+    def test_no_response_destination_stores_none_address(self):
+        cell = build_jetton_transfer_body_fields(
+            amount=1, pay_to=DESTINATION, extra={"forwardTonAmount": "0"}
+        )
+        s = cell.begin_parse()
+        s.load_uint(32)
+        s.load_uint(64)
+        s.load_coins()
+        s.load_address()
+        response_addr = s.load_address()
+        assert response_addr is None
+
+    def test_response_destination_stored_as_address(self):
+        extra = {"forwardTonAmount": "0", "responseDestination": RESPONSE_DEST}
+        cell = build_jetton_transfer_body_fields(amount=1, pay_to=DESTINATION, extra=extra)
+        s = cell.begin_parse()
+        s.load_uint(32)
+        s.load_uint(64)
+        s.load_coins()
+        s.load_address()
+        response_addr = s.load_address()
+        assert normalize_address(response_addr) == normalize_address(RESPONSE_DEST)
+
+    def test_custom_payload_bit_always_zero(self):
+        cell = build_jetton_transfer_body_fields(
+            amount=1, pay_to=DESTINATION, extra={"forwardTonAmount": "0"}
+        )
+        s = cell.begin_parse()
+        s.load_uint(32)
+        s.load_uint(64)
+        s.load_coins()
+        s.load_address()
+        s.load_address()
+        assert s.load_bit() == 0
+
+    def test_forward_ton_amount_stored(self):
+        cell = build_jetton_transfer_body_fields(
+            amount=1, pay_to=DESTINATION, extra={"forwardTonAmount": "50000000"}
+        )
+        s = cell.begin_parse()
+        s.load_uint(32)
+        s.load_uint(64)
+        s.load_coins()
+        s.load_address()
+        s.load_address()
+        s.load_bit()
+        assert s.load_coins() == 50_000_000
+
+    def test_forward_ton_amount_zero_accepted(self):
+        cell = build_jetton_transfer_body_fields(
+            amount=1, pay_to=DESTINATION, extra={"forwardTonAmount": "0"}
+        )
+        s = cell.begin_parse()
+        s.load_uint(32)
+        s.load_uint(64)
+        s.load_coins()
+        s.load_address()
+        s.load_address()
+        s.load_bit()
+        assert s.load_coins() == 0
+
+    def test_negative_forward_ton_amount_raises(self):
+        with pytest.raises(ValueError, match="Forward ton amount should be >= 0"):
+            build_jetton_transfer_body_fields(
+                amount=1, pay_to=DESTINATION, extra={"forwardTonAmount": "-1"}
+            )
+
+    def test_no_forward_payload_stores_two_zero_bits(self):
+        cell = build_jetton_transfer_body_fields(
+            amount=1, pay_to=DESTINATION, extra={"forwardTonAmount": "0"}
+        )
+        s = cell.begin_parse()
+        s.load_uint(32)
+        s.load_uint(64)
+        s.load_coins()
+        s.load_address()
+        s.load_address()
+        s.load_bit()
+        s.load_coins()
+        assert s.load_uint(2) == 0
+
+    def test_forward_payload_stored_as_ref(self):
+        payload_cell = begin_cell().store_uint(0xDE, 8).end_cell()
+        payload_b64 = base64.b64encode(payload_cell.to_boc()).decode()
+        cell = build_jetton_transfer_body_fields(
+            amount=1,
+            pay_to=DESTINATION,
+            extra={"forwardTonAmount": "0", "forwardPayload": payload_b64},
+        )
+        assert len(cell.refs) >= 1
+
+
+class TestBuildJettonTransferBody:
+    def test_delegates_amount_and_pay_to_from_requirements(self):
+        req = make_tvm_requirements(
+            amount="250", pay_to=DESTINATION, extra={"forwardTonAmount": "0"}
+        )
+        cell = build_jetton_transfer_body(req)
+        s = cell.begin_parse()
+        s.load_uint(32)
+        s.load_uint(64)
+        assert s.load_coins() == 250
+        addr = s.load_address()
+        assert normalize_address(addr) == normalize_address(DESTINATION)
+
+    def test_amount_coerced_from_string(self):
+        req = make_tvm_requirements(
+            amount="1000000", pay_to=DESTINATION, extra={"forwardTonAmount": "0"}
+        )
+        cell = build_jetton_transfer_body(req)
+        s = cell.begin_parse()
+        s.load_uint(32)
+        s.load_uint(64)
+        assert s.load_coins() == 1_000_000
+
+    def test_returns_cell(self):
+        from pytoniq_core import Cell as TonCell
+
+        req = make_tvm_requirements(amount="1", pay_to=DESTINATION, extra={"forwardTonAmount": "0"})
+        cell = build_jetton_transfer_body(req)
+        assert isinstance(cell, TonCell)
+
+
+class TestParseJettonTransfer:
+    def test_round_trip_extracts_destination(self):
+        cell = build_jetton_transfer_body_fields(
+            amount=500, pay_to=DESTINATION, extra={"forwardTonAmount": "0"}
+        )
+        result = parse_jetton_transfer(JETTON_WALLET, cell)
+        assert normalize_address(result.destination) == normalize_address(DESTINATION)
+
+    def test_round_trip_extracts_jetton_amount(self):
+        cell = build_jetton_transfer_body_fields(
+            amount=777, pay_to=DESTINATION, extra={"forwardTonAmount": "0"}
+        )
+        result = parse_jetton_transfer(JETTON_WALLET, cell)
+        assert result.jetton_amount == 777
+
+    def test_round_trip_extracts_forward_ton_amount(self):
+        cell = build_jetton_transfer_body_fields(
+            amount=1, pay_to=DESTINATION, extra={"forwardTonAmount": "12345"}
+        )
+        result = parse_jetton_transfer(JETTON_WALLET, cell)
+        assert result.forward_ton_amount == 12345
+
+    def test_source_wallet_set_to_jetton_wallet_arg(self):
+        cell = build_jetton_transfer_body_fields(
+            amount=1, pay_to=DESTINATION, extra={"forwardTonAmount": "0"}
+        )
+        result = parse_jetton_transfer(JETTON_WALLET, cell)
+        assert result.source_wallet == JETTON_WALLET
+
+    def test_body_hash_equals_cell_hash(self):
+        cell = build_jetton_transfer_body_fields(
+            amount=1, pay_to=DESTINATION, extra={"forwardTonAmount": "0"}
+        )
+        result = parse_jetton_transfer(JETTON_WALLET, cell)
+        assert result.body_hash == cell.hash
+
+    def test_attached_ton_amount_always_zero(self):
+        cell = build_jetton_transfer_body_fields(
+            amount=1, pay_to=DESTINATION, extra={"forwardTonAmount": "99"}
+        )
+        result = parse_jetton_transfer(JETTON_WALLET, cell)
+        assert result.attached_ton_amount == 0
+
+    def test_response_destination_none_when_absent(self):
+        cell = build_jetton_transfer_body_fields(
+            amount=1, pay_to=DESTINATION, extra={"forwardTonAmount": "0"}
+        )
+        result = parse_jetton_transfer(JETTON_WALLET, cell)
+        assert result.response_destination is None
+
+    def test_response_destination_normalized_when_present(self):
+        extra = {"forwardTonAmount": "0", "responseDestination": RESPONSE_DEST}
+        cell = build_jetton_transfer_body_fields(amount=1, pay_to=DESTINATION, extra=extra)
+        result = parse_jetton_transfer(JETTON_WALLET, cell)
+        assert normalize_address(result.response_destination) == normalize_address(RESPONSE_DEST)
+
+    def test_wrong_opcode_raises(self):
+        cell = _raw_transfer_body(opcode=0xDEAD_BEEF)
+        with pytest.raises(ValueError, match=ERR_EXACT_TVM_INVALID_JETTON_TRANSFER):
+            parse_jetton_transfer(JETTON_WALLET, cell)
+
+    def test_custom_payload_bit_set_raises(self):
+        cell = _raw_transfer_body(custom_payload_bit=True)
+        with pytest.raises(ValueError, match=ERR_EXACT_TVM_INVALID_JETTON_TRANSFER):
+            parse_jetton_transfer(JETTON_WALLET, cell)
+
+    def test_null_destination_raises(self):
+        cell = _raw_transfer_body(destination=None)
+        with pytest.raises(ValueError, match=ERR_EXACT_TVM_INVALID_JETTON_TRANSFER):
+            parse_jetton_transfer(JETTON_WALLET, cell)
+
+    def test_forward_payload_from_ref_when_bit_one(self):
+        cell = _raw_transfer_body(forward_payload_bit=True)
+        result = parse_jetton_transfer(JETTON_WALLET, cell)
+        assert result.forward_payload is not None
+
+    def test_forward_payload_from_slice_when_bit_zero(self):
+        cell = _raw_transfer_body(forward_payload_bit=False)
+        result = parse_jetton_transfer(JETTON_WALLET, cell)
+        assert result.forward_payload is not None