diff --git a/hathor/nanocontracts/context.py b/hathor/nanocontracts/context.py
index 2002472fa..6b94b3ba6 100644
--- a/hathor/nanocontracts/context.py
+++ b/hathor/nanocontracts/context.py
@@ -17,11 +17,11 @@
 from collections import defaultdict
 from itertools import chain
 from types import MappingProxyType
-from typing import TYPE_CHECKING, Any, Sequence, final
+from typing import TYPE_CHECKING, Any, Sequence, assert_never, final
 
 from hathor.crypto.util import get_address_b58_from_bytes
 from hathor.nanocontracts.exception import NCFail, NCInvalidContext
-from hathor.nanocontracts.types import Address, ContractId, NCAction, TokenUid
+from hathor.nanocontracts.types import Address, CallerId, ContractId, NCAction, TokenUid
 from hathor.nanocontracts.vertex_data import VertexData
 from hathor.transaction.exceptions import TxValidationError
 
@@ -39,9 +39,9 @@ class Context:
     Deposits and withdrawals are grouped by token. Note that it is impossible
     to have both a deposit and a withdrawal for the same token.
     """
-    __slots__ = ('__actions', '__address', '__vertex', '__timestamp', '__all_actions__')
+    __slots__ = ('__actions', '__caller_id', '__vertex', '__timestamp', '__all_actions__')
     __actions: MappingProxyType[TokenUid, tuple[NCAction, ...]]
-    __address: Address | ContractId
+    __caller_id: CallerId
     __vertex: VertexData
     __timestamp: int
 
@@ -49,7 +49,7 @@ def __init__(
         self,
         actions: Sequence[NCAction],
         vertex: BaseTransaction | VertexData,
-        address: Address | ContractId,
+        caller_id: CallerId,
         timestamp: int,
     ) -> None:
         # Dict of action where the key is the token_uid.
@@ -77,7 +77,7 @@ def __init__(
             self.__vertex = VertexData.create_from_vertex(vertex)
 
         # Address calling the method.
-        self.__address = address
+        self.__caller_id = caller_id
 
         # Timestamp of the first block confirming tx.
         self.__timestamp = timestamp
@@ -87,8 +87,29 @@ def vertex(self) -> VertexData:
         return self.__vertex
 
     @property
-    def address(self) -> Address | ContractId:
-        return self.__address
+    def caller_id(self) -> CallerId:
+        """Get the caller ID which can be either an Address or a ContractId."""
+        return self.__caller_id
+
+    def get_caller_address(self) -> Address | None:
+        """Get the caller address if the caller is an address, None if it's a contract."""
+        match self.caller_id:
+            case Address():
+                return self.caller_id
+            case ContractId():
+                return None
+            case _:
+                assert_never(self.caller_id)
+
+    def get_caller_contract_id(self) -> ContractId | None:
+        """Get the caller contract ID if the caller is a contract, None if it's an address."""
+        match self.caller_id:
+            case Address():
+                return None
+            case ContractId():
+                return self.caller_id
+            case _:
+                assert_never(self.caller_id)
 
     @property
     def timestamp(self) -> int:
@@ -116,7 +137,7 @@ def copy(self) -> Context:
         return Context(
             actions=list(self.__all_actions__),
             vertex=self.vertex,
-            address=self.address,
+            caller_id=self.caller_id,
             timestamp=self.timestamp,
         )
 
@@ -124,6 +145,6 @@ def to_json(self) -> dict[str, Any]:
         """Return a JSON representation of the context."""
         return {
             'actions': [action.to_json() for action in self.__all_actions__],
-            'address': get_address_b58_from_bytes(self.address),
+            'caller_id': get_address_b58_from_bytes(self.caller_id),
             'timestamp': self.timestamp,
         }
diff --git a/hathor/nanocontracts/nc_types/__init__.py b/hathor/nanocontracts/nc_types/__init__.py
index f416d8321..442891305 100644
--- a/hathor/nanocontracts/nc_types/__init__.py
+++ b/hathor/nanocontracts/nc_types/__init__.py
@@ -19,6 +19,7 @@
 from hathor.nanocontracts.nc_types.address_nc_type import AddressNCType
 from hathor.nanocontracts.nc_types.bool_nc_type import BoolNCType
 from hathor.nanocontracts.nc_types.bytes_nc_type import BytesLikeNCType, BytesNCType
+from hathor.nanocontracts.nc_types.caller_id_nc_type import CallerIdNCType
 from hathor.nanocontracts.nc_types.collection_nc_type import DequeNCType, FrozenSetNCType, ListNCType, SetNCType
 from hathor.nanocontracts.nc_types.dataclass_nc_type import DataclassNCType
 from hathor.nanocontracts.nc_types.fixed_size_bytes_nc_type import Bytes32NCType
@@ -56,6 +57,7 @@
     'BoolNCType',
     'BytesLikeNCType',
     'BytesNCType',
+    'CallerIdNCType',
     'DataclassNCType',
     'DequeNCType',
     'DictNCType',
@@ -124,6 +126,7 @@
     TxOutputScript: BytesLikeNCType[TxOutputScript],
     VertexId: Bytes32NCType,
     SignedData: SignedDataNCType,
+    (Address, ContractId): CallerIdNCType,
 }
 
 # This mapping includes all supported NCType classes, should only be used for parsing function calls
diff --git a/hathor/nanocontracts/nc_types/caller_id_nc_type.py b/hathor/nanocontracts/nc_types/caller_id_nc_type.py
new file mode 100644
index 000000000..5e3dee442
--- /dev/null
+++ b/hathor/nanocontracts/nc_types/caller_id_nc_type.py
@@ -0,0 +1,115 @@
+#  Copyright 2025 Hathor Labs
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from __future__ import annotations
+
+from types import UnionType
+from typing import _UnionGenericAlias as UnionGenericAlias, assert_never, get_args  # type: ignore[attr-defined]
+
+from typing_extensions import Self, override
+
+from hathor.crypto.util import decode_address, get_address_b58_from_bytes
+from hathor.nanocontracts.nc_types.nc_type import NCType
+from hathor.nanocontracts.types import Address, CallerId, ContractId
+from hathor.serialization import Deserializer, Serializer
+from hathor.serialization.compound_encoding.caller_id import decode_caller_id, encode_caller_id
+from hathor.transaction.base_transaction import TX_HASH_SIZE
+from hathor.transaction.headers.nano_header import ADDRESS_LEN_BYTES
+
+
+class CallerIdNCType(NCType[CallerId]):
+    """Represents `CallerID` values, which can be `Address` or `ContractId`."""
+    __slots__ = ()
+    _is_hashable = True
+
+    @override
+    @classmethod
+    def _from_type(cls, type_: type[Address] | type[ContractId], /, *, type_map: NCType.TypeMap) -> Self:
+        if not isinstance(type_, (UnionType, UnionGenericAlias)):
+            raise TypeError('expected type union')
+        args = get_args(type_)
+        assert args, 'union always has args'
+        if len(args) != 2 or Address not in args or ContractId not in args:
+            raise TypeError('type must be either `Address | ContractId` or `ContractId | Address`')
+        return cls()
+
+    @override
+    def _check_value(self, value: CallerId, /, *, deep: bool) -> None:
+        match value:
+            case Address():
+                if len(value) != ADDRESS_LEN_BYTES:
+                    raise ValueError(f'an address must always have {ADDRESS_LEN_BYTES} bytes')
+            case ContractId():
+                if len(value) != TX_HASH_SIZE:
+                    raise ValueError(f'an contract id must always have {TX_HASH_SIZE} bytes')
+            case _:
+                assert_never(value)
+
+    @override
+    def _serialize(self, serializer: Serializer, value: CallerId, /) -> None:
+        encode_caller_id(serializer, value)
+
+    @override
+    def _deserialize(self, deserializer: Deserializer, /) -> CallerId:
+        return decode_caller_id(deserializer)
+
+    @override
+    def _json_to_value(self, json_value: NCType.Json, /) -> CallerId:
+        """
+        >>> nc_type = CallerIdNCType()
+        >>> value = nc_type.json_to_value('HH5As5aLtzFkcbmbXZmE65wSd22GqPWq2T')
+        >>> isinstance(value, Address)
+        True
+        >>> value == Address(bytes.fromhex('2873c0a326af979a12be89ee8a00e8871c8e2765022e9b803c'))
+        True
+        >>> contract_id = ContractId(b'\x11' * 32)
+        >>> value = nc_type.json_to_value(contract_id.hex())
+        >>> isinstance(value, ContractId)
+        True
+        >>> value == contract_id
+        True
+        >>> nc_type.json_to_value('foo')
+        Traceback (most recent call last):
+        ...
+        ValueError: cannot decode "foo" as CallerId
+        """
+        if not isinstance(json_value, str):
+            raise ValueError('expected str')
+
+        if len(json_value) == 34:
+            return Address(decode_address(json_value))
+
+        if len(json_value) == TX_HASH_SIZE * 2:
+            return ContractId(bytes.fromhex(json_value))
+
+        raise ValueError(f'cannot decode "{json_value}" as CallerId')
+
+    @override
+    def _value_to_json(self, value: CallerId, /) -> NCType.Json:
+        """
+        >>> nc_type = CallerIdNCType()
+        >>> address = Address(bytes.fromhex('2873c0a326af979a12be89ee8a00e8871c8e2765022e9b803c'))
+        >>> nc_type.value_to_json(address)
+        'HH5As5aLtzFkcbmbXZmE65wSd22GqPWq2T'
+        >>> contract_id = ContractId(b'\x11' * 32)
+        >>> nc_type.value_to_json(contract_id)
+        '1111111111111111111111111111111111111111111111111111111111111111'
+        """
+        match value:
+            case Address():
+                return get_address_b58_from_bytes(value)
+            case ContractId():
+                return value.hex()
+            case _:
+                assert_never(value)
diff --git a/hathor/nanocontracts/nc_types/utils.py b/hathor/nanocontracts/nc_types/utils.py
index 48cc9a309..0e8799dd3 100644
--- a/hathor/nanocontracts/nc_types/utils.py
+++ b/hathor/nanocontracts/nc_types/utils.py
@@ -33,7 +33,7 @@
 
 T = TypeVar('T')
 TypeAliasMap: TypeAlias = Mapping[type | UnionType, type]
-TypeToNCTypeMap: TypeAlias = Mapping[type | UnionType, type['NCType']]
+TypeToNCTypeMap: TypeAlias = Mapping[type | UnionType | tuple[type, ...], type['NCType']]
 
 
 def get_origin_classes(type_: type) -> Iterator[type]:
@@ -218,7 +218,7 @@ def get_usable_origin_type(
     *,
     type_map: 'NCType.TypeMap',
     _verbose: bool = True,
-) -> type:
+) -> type | tuple[type, ...]:
     """ The purpose of this function is to map a given type into a type that is usable in a NCType.TypeMap
 
     It takes into account type-aliasing according to NCType.TypeMap.alias_map. If the given type cannot be used in the
@@ -243,7 +243,16 @@ def get_usable_origin_type(
 
     # if we have a `dict[int, int]` we use `get_origin()` to get the `dict` part, since it's a different instance
     aliased_type: type = get_aliased_type(type_, type_map.alias_map, _verbose=_verbose)
-    origin_aliased_type: type = get_origin(aliased_type) or aliased_type
+    origin_aliased_type: type | tuple[type, ...] = get_origin(aliased_type) or aliased_type
+
+    if origin_aliased_type is UnionType:
+        # When it's an union and None is not in it, it's not Optional,
+        # so we must index by args which is a tuple of types.
+        # This is done for support of specific union types such as CallerId (Address | ContractId)
+        args = get_args(aliased_type)
+        assert args is not None
+        if NoneType not in args:
+            origin_aliased_type = args
 
     if origin_aliased_type in type_map.nc_types_map:
         return origin_aliased_type
diff --git a/hathor/nanocontracts/runner/runner.py b/hathor/nanocontracts/runner/runner.py
index a142c93c0..ebccae7a5 100644
--- a/hathor/nanocontracts/runner/runner.py
+++ b/hathor/nanocontracts/runner/runner.py
@@ -410,7 +410,7 @@ def _unsafe_call_another_contract_public_method(
         ctx = Context(
             actions=actions,
             vertex=first_ctx.vertex,
-            address=last_call_record.contract_id,
+            caller_id=last_call_record.contract_id,
             timestamp=first_ctx.timestamp,
         )
         return self._execute_public_method_call(
diff --git a/hathor/nanocontracts/types.py b/hathor/nanocontracts/types.py
index f0876edd4..115c68c5f 100644
--- a/hathor/nanocontracts/types.py
+++ b/hathor/nanocontracts/types.py
@@ -31,15 +31,26 @@
 from hathor.transaction.util import bytes_to_int, int_to_bytes
 from hathor.utils.typing import InnerTypeMixin
 
+
 # Types to be used by blueprints.
-Address = NewType('Address', bytes)
+class Address(bytes):
+    __slots__ = ()
+
+
+class VertexId(bytes):
+    __slots__ = ()
+
+
+class ContractId(VertexId):
+    __slots__ = ()
+
+
 Amount = NewType('Amount', int)
 Timestamp = NewType('Timestamp', int)
 TokenUid = NewType('TokenUid', bytes)
 TxOutputScript = NewType('TxOutputScript', bytes)
-VertexId = NewType('VertexId', bytes)
 BlueprintId = NewType('BlueprintId', VertexId)
-ContractId = NewType('ContractId', VertexId)
+CallerId: TypeAlias = Address | ContractId
 
 T = TypeVar('T')
 
diff --git a/hathor/serialization/compound_encoding/caller_id.py b/hathor/serialization/compound_encoding/caller_id.py
new file mode 100644
index 000000000..0b29fa24a
--- /dev/null
+++ b/hathor/serialization/compound_encoding/caller_id.py
@@ -0,0 +1,80 @@
+#  Copyright 2025 Hathor Labs
+#
+#  Licensed under the Apache License, Version 2.0 (the "License");
+#  you may not use this file except in compliance with the License.
+#  You may obtain a copy of the License at
+#
+#  http://www.apache.org/licenses/LICENSE-2.0
+#
+#  Unless required by applicable law or agreed to in writing, software
+#  distributed under the License is distributed on an "AS IS" BASIS,
+#  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+#  See the License for the specific language governing permissions and
+#  limitations under the License.
+
+r"""
+A caller ID union type is encoded with a single byte identifier followed by the encoded value according to the type.
+
+Layout:
+
+    [0x00][address] when Address
+    [0x01][contract_id] when ContractId
+
+>>> from hathor.nanocontracts.types import Address, ContractId
+>>> se = Serializer.build_bytes_serializer()
+>>> addr = Address(b'\x11' * 25)
+>>> encode_caller_id(se, addr)
+>>> bytes(se.finalize()).hex()
+'0011111111111111111111111111111111111111111111111111'
+
+>>> se = Serializer.build_bytes_serializer()
+>>> contract_id = ContractId(b'\x22' * 32)
+>>> encode_caller_id(se, contract_id)
+>>> bytes(se.finalize()).hex()
+'012222222222222222222222222222222222222222222222222222222222222222'
+
+>>> de = Deserializer.build_bytes_deserializer(bytes.fromhex('0011111111111111111111111111111111111111111111111111'))
+>>> result = decode_caller_id(de)
+>>> isinstance(result, Address)
+True
+>>> de.finalize()
+
+>>> value = bytes.fromhex('012222222222222222222222222222222222222222222222222222222222222222')
+>>> de = Deserializer.build_bytes_deserializer(value)
+>>> result = decode_caller_id(de)
+>>> isinstance(result, ContractId)
+True
+>>> de.finalize()
+"""
+
+from typing import assert_never
+
+from hathor.nanocontracts.types import Address, CallerId, ContractId
+from hathor.serialization import Deserializer, Serializer
+from hathor.serialization.encoding.bool import decode_bool, encode_bool
+
+from ...transaction.base_transaction import TX_HASH_SIZE
+from ...transaction.headers.nano_header import ADDRESS_LEN_BYTES
+
+
+def encode_caller_id(serializer: Serializer, value: CallerId) -> None:
+    match value:
+        case Address():
+            assert len(value) == ADDRESS_LEN_BYTES
+            encode_bool(serializer, False)
+        case ContractId():
+            assert len(value) == TX_HASH_SIZE
+            encode_bool(serializer, True)
+        case _:
+            assert_never(value)
+    serializer.write_bytes(value)
+
+
+def decode_caller_id(deserializer: Deserializer) -> CallerId:
+    is_contract = decode_bool(deserializer)
+    if is_contract:
+        data = bytes(deserializer.read_bytes(TX_HASH_SIZE))
+        return ContractId(data)
+    else:
+        data = bytes(deserializer.read_bytes(ADDRESS_LEN_BYTES))
+        return Address(data)
diff --git a/hathor/transaction/headers/nano_header.py b/hathor/transaction/headers/nano_header.py
index 709df3031..4d15f96c8 100644
--- a/hathor/transaction/headers/nano_header.py
+++ b/hathor/transaction/headers/nano_header.py
@@ -324,7 +324,7 @@ def get_context(self) -> Context:
         context = Context(
             actions=action_list,
             vertex=self.tx,
-            address=Address(self.nc_address),
+            caller_id=Address(self.nc_address),
             timestamp=timestamp,
         )
         return context
diff --git a/tests/nanocontracts/blueprints/test_swap_demo.py b/tests/nanocontracts/blueprints/test_swap_demo.py
index 059282990..adea38690 100644
--- a/tests/nanocontracts/blueprints/test_swap_demo.py
+++ b/tests/nanocontracts/blueprints/test_swap_demo.py
@@ -37,7 +37,7 @@ def _initialize(
         context = Context(
             actions=[deposit_a, deposit_b],
             vertex=self.tx,
-            address=self.address,
+            caller_id=self.address,
             timestamp=self.now
         )
 
@@ -68,7 +68,7 @@ def _swap(
         context = Context(
             actions=[swap_a, swap_b],
             vertex=self.tx,
-            address=self.address,
+            caller_id=self.address,
             timestamp=self.now
         )
 
diff --git a/tests/nanocontracts/blueprints/unittest.py b/tests/nanocontracts/blueprints/unittest.py
index 972b03276..7a4ab9362 100644
--- a/tests/nanocontracts/blueprints/unittest.py
+++ b/tests/nanocontracts/blueprints/unittest.py
@@ -178,6 +178,6 @@ def create_context(
         return Context(
             actions=actions if actions is not None else [],
             vertex=vertex or self.get_genesis_tx(),
-            address=address or self.gen_random_address(),
+            caller_id=address or self.gen_random_address(),
             timestamp=timestamp or self.now,
         )
diff --git a/tests/nanocontracts/test_allowed_actions.py b/tests/nanocontracts/test_allowed_actions.py
index 0841bd2bb..ff7349ce3 100644
--- a/tests/nanocontracts/test_allowed_actions.py
+++ b/tests/nanocontracts/test_allowed_actions.py
@@ -88,7 +88,7 @@ def _get_context(self, *actions: NCAction) -> Context:
         return Context(
             actions=list(actions),
             vertex=self.tx,
-            address=self.address,
+            caller_id=self.address,
             timestamp=self.now,
         )
 
diff --git a/tests/nanocontracts/test_authorities_call_another.py b/tests/nanocontracts/test_authorities_call_another.py
index e4bec4867..27525993a 100644
--- a/tests/nanocontracts/test_authorities_call_another.py
+++ b/tests/nanocontracts/test_authorities_call_another.py
@@ -127,13 +127,13 @@ def _initialize(self, caller_actions: list[NCAction] | None = None) -> None:
         caller_ctx = Context(
             actions=caller_actions or [],
             vertex=self.tx,
-            address=self.address,
+            caller_id=self.address,
             timestamp=self.now
         )
         callee_ctx = Context(
             actions=[],
             vertex=self.tx,
-            address=self.address,
+            caller_id=self.address,
             timestamp=self.now
         )
         self.runner.create_contract(self.caller_id, self.caller_blueprint_id, caller_ctx, other_id=self.callee_id)
@@ -145,7 +145,7 @@ def _grant_to_other(self, *, mint: bool, melt: bool) -> None:
         context = Context(
             actions=[],
             vertex=self.tx,
-            address=self.address,
+            caller_id=self.address,
             timestamp=self.now
         )
         self.runner.call_public_method(
@@ -156,7 +156,7 @@ def _revoke_from_self(self, contract_id: ContractId, *, actions: list[NCAction],
         context = Context(
             actions=actions,
             vertex=self.tx,
-            address=self.address,
+            caller_id=self.address,
             timestamp=self.now
         )
         self.runner.call_public_method(
@@ -167,7 +167,7 @@ def _revoke_from_other(self, *, mint: bool, melt: bool) -> None:
         context = Context(
             actions=[],
             vertex=self.tx,
-            address=self.address,
+            caller_id=self.address,
             timestamp=self.now
         )
         self.runner.call_public_method(
@@ -219,7 +219,7 @@ def test_acquire_mint(self) -> None:
         context = Context(
             actions=[NCGrantAuthorityAction(token_uid=self.token_a, mint=True, melt=False)],
             vertex=self.tx,
-            address=self.address,
+            caller_id=self.address,
             timestamp=self.now
         )
         self.runner.call_public_method(self.callee_id, 'nop', context)
@@ -229,7 +229,7 @@ def test_acquire_mint(self) -> None:
         context = Context(
             actions=[],
             vertex=self.tx,
-            address=self.address,
+            caller_id=self.address,
             timestamp=self.now
         )
         self.runner.call_public_method(
@@ -244,7 +244,7 @@ def test_acquire_melt(self) -> None:
         context = Context(
             actions=[NCGrantAuthorityAction(token_uid=self.token_a, mint=False, melt=True)],
             vertex=self.tx,
-            address=self.address,
+            caller_id=self.address,
             timestamp=self.now
         )
         self.runner.call_public_method(self.callee_id, 'nop', context)
@@ -254,7 +254,7 @@ def test_acquire_melt(self) -> None:
         context = Context(
             actions=[],
             vertex=self.tx,
-            address=self.address,
+            caller_id=self.address,
             timestamp=self.now
         )
         self.runner.call_public_method(
@@ -284,7 +284,7 @@ def test_revoke_then_grant_same_call_another_contract(self) -> None:
         context = Context(
             actions=[],
             vertex=self.tx,
-            address=self.address,
+            caller_id=self.address,
             timestamp=self.now
         )
         self.runner.call_public_method(self.caller_id, 'call_grant_all_to_other_then_revoke', context, self.token_a)
@@ -296,7 +296,7 @@ def test_grant_then_revoke_same_call_another_contract(self) -> None:
         context = Context(
             actions=[NCGrantAuthorityAction(token_uid=self.token_a, mint=True, melt=True)],
             vertex=self.tx,
-            address=self.address,
+            caller_id=self.address,
             timestamp=self.now
         )
         self.runner.call_public_method(self.caller_id, 'call_revoke_all_from_other', context, self.token_a)
diff --git a/tests/nanocontracts/test_blueprint_syntax.py b/tests/nanocontracts/test_blueprint_syntax.py
index ba651d633..6059eacad 100644
--- a/tests/nanocontracts/test_blueprint_syntax.py
+++ b/tests/nanocontracts/test_blueprint_syntax.py
@@ -31,7 +31,7 @@ def setUp(self) -> None:
         self.ctx = Context(
             actions=[],
             vertex=self.get_genesis_tx(),
-            address=Address(self.gen_random_address()),
+            caller_id=Address(self.gen_random_address()),
             timestamp=self.now,
         )
 
diff --git a/tests/nanocontracts/test_blueprints/bet.py b/tests/nanocontracts/test_blueprints/bet.py
index fe81332b8..69aa94abf 100644
--- a/tests/nanocontracts/test_blueprints/bet.py
+++ b/tests/nanocontracts/test_blueprints/bet.py
@@ -191,7 +191,9 @@ def withdraw(self, ctx: Context) -> None:
         assert isinstance(action, NCWithdrawalAction)
         self.fail_if_result_is_not_available()
         self.fail_if_invalid_token(action)
-        address = Address(ctx.address)
+        caller_address = ctx.get_caller_address()
+        assert caller_address is not None
+        address = Address(caller_address)
         allowed = self.get_max_withdrawal(address)
         if action.amount > allowed:
             raise InsufficientBalance(f'withdrawal amount is greater than available (max: {allowed})')
diff --git a/tests/nanocontracts/test_caller_id.py b/tests/nanocontracts/test_caller_id.py
new file mode 100644
index 000000000..73aade0ef
--- /dev/null
+++ b/tests/nanocontracts/test_caller_id.py
@@ -0,0 +1,90 @@
+#  Copyright 2025 Hathor Labs
+#
+#  Licensed under the Apache License, Version 2.0 (the "License");
+#  you may not use this file except in compliance with the License.
+#  You may obtain a copy of the License at
+#
+#  http://www.apache.org/licenses/LICENSE-2.0
+#
+#  Unless required by applicable law or agreed to in writing, software
+#  distributed under the License is distributed on an "AS IS" BASIS,
+#  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+#  See the License for the specific language governing permissions and
+#  limitations under the License.
+
+from hathor.nanocontracts import Blueprint, Context, public
+from hathor.nanocontracts.types import Address, BlueprintId, CallerId, ContractId
+from tests.nanocontracts.blueprints.unittest import BlueprintTestCase
+
+
+class MyBlueprint(Blueprint):
+    address: Address | None
+    contract_id: ContractId | None
+    caller_id: CallerId
+
+    @public
+    def initialize(self, ctx: Context) -> None:
+        self.caller_id = ctx.caller_id
+
+        if address := ctx.get_caller_address():
+            self.address = address
+            self.contract_id = None
+        elif contract_id := ctx.get_caller_contract_id():
+            self.address = None
+            self.contract_id = contract_id
+        else:
+            raise AssertionError
+
+    @public
+    def create_another(self, ctx: Context, blueprint_id: BlueprintId) -> ContractId:
+        contract_id, _ = self.syscall.create_contract(blueprint_id, b'1', [])
+        return contract_id
+
+    @public
+    def test_args_and_return(self, ctx: Context, caller_id: CallerId) -> CallerId:
+        return caller_id
+
+
+class TestCallerId(BlueprintTestCase):
+    def setUp(self) -> None:
+        super().setUp()
+        self.blueprint_id = self._register_blueprint_class(MyBlueprint)
+        self.contract_id1 = self.gen_random_contract_id()
+
+    def test_callers(self) -> None:
+        address = self.gen_random_address()
+        ctx = self.create_context(address=address)
+        self.runner.create_contract(self.contract_id1, self.blueprint_id, ctx)
+        contract1 = self.get_readonly_contract(self.contract_id1)
+
+        # Caller is an address (a tx)
+        assert isinstance(contract1, MyBlueprint)
+        assert contract1.address == address
+        assert contract1.contract_id is None
+        assert contract1.caller_id == address
+
+        contract_id2 = self.runner.call_public_method(self.contract_id1, 'create_another', ctx, self.blueprint_id)
+        contract2 = self.get_readonly_contract(contract_id2)
+
+        # Caller is another contract
+        assert isinstance(contract2, MyBlueprint)
+        assert contract2.address is None
+        assert contract2.contract_id == self.contract_id1
+        assert contract2.caller_id == self.contract_id1
+
+    def test_args_and_return(self) -> None:
+        self.runner.create_contract(self.contract_id1, self.blueprint_id, self.create_context())
+
+        # Receive and return an address
+        address = self.gen_random_address()
+        ret = self.runner.call_public_method(
+            self.contract_id1, 'test_args_and_return', self.create_context(), address
+        )
+        assert ret == address
+
+        # Receive and return a contract id
+        contract_id = self.gen_random_contract_id()
+        ret = self.runner.call_public_method(
+            self.contract_id1, 'test_args_and_return', self.create_context(), contract_id
+        )
+        assert ret == contract_id
diff --git a/tests/nanocontracts/test_contract_upgrade.py b/tests/nanocontracts/test_contract_upgrade.py
index 909947aef..c06b43f88 100644
--- a/tests/nanocontracts/test_contract_upgrade.py
+++ b/tests/nanocontracts/test_contract_upgrade.py
@@ -113,7 +113,7 @@ def test_basic(self) -> None:
 
         tx = self.get_genesis_tx()
         address = self.gen_random_address()
-        ctx = Context(actions=[], vertex=tx, address=address, timestamp=0)
+        ctx = Context(actions=[], vertex=tx, caller_id=address, timestamp=0)
 
         self.runner.create_contract(code1_id, self.code1_bp_id, ctx)
         self.runner.create_contract(code2_id, self.code2_bp_id, ctx)
diff --git a/tests/nanocontracts/test_execution_order.py b/tests/nanocontracts/test_execution_order.py
index 4d8d83c3d..0252d0429 100644
--- a/tests/nanocontracts/test_execution_order.py
+++ b/tests/nanocontracts/test_execution_order.py
@@ -140,7 +140,7 @@ def _get_context(self, *actions: NCAction) -> Context:
         return Context(
             actions=list(actions),
             vertex=self.tx,
-            address=self.address,
+            caller_id=self.address,
             timestamp=self.now,
         )
 
diff --git a/tests/nanocontracts/test_exposed_properties.py b/tests/nanocontracts/test_exposed_properties.py
index 2c6718f65..9d3afe336 100644
--- a/tests/nanocontracts/test_exposed_properties.py
+++ b/tests/nanocontracts/test_exposed_properties.py
@@ -47,8 +47,10 @@
     'hathor.nanocontracts.blueprint.Blueprint.syscall',
     'hathor.nanocontracts.context.Context.actions',
     'hathor.nanocontracts.context.Context.actions_list',
-    'hathor.nanocontracts.context.Context.address',
+    'hathor.nanocontracts.context.Context.caller_id',
     'hathor.nanocontracts.context.Context.copy',
+    'hathor.nanocontracts.context.Context.get_caller_address',
+    'hathor.nanocontracts.context.Context.get_caller_contract_id',
     'hathor.nanocontracts.context.Context.get_single_action',
     'hathor.nanocontracts.context.Context.some_new_attribute',
     'hathor.nanocontracts.context.Context.timestamp',
@@ -58,10 +60,94 @@
     'hathor.nanocontracts.exception.NCFail.args',
     'hathor.nanocontracts.exception.NCFail.some_new_attribute',
     'hathor.nanocontracts.exception.NCFail.with_traceback',
+    'hathor.nanocontracts.types.Address.capitalize',
+    'hathor.nanocontracts.types.Address.center',
+    'hathor.nanocontracts.types.Address.count',
+    'hathor.nanocontracts.types.Address.decode',
+    'hathor.nanocontracts.types.Address.endswith',
+    'hathor.nanocontracts.types.Address.expandtabs',
+    'hathor.nanocontracts.types.Address.find',
+    'hathor.nanocontracts.types.Address.fromhex',
+    'hathor.nanocontracts.types.Address.hex',
+    'hathor.nanocontracts.types.Address.index',
+    'hathor.nanocontracts.types.Address.isalnum',
+    'hathor.nanocontracts.types.Address.isalpha',
+    'hathor.nanocontracts.types.Address.isascii',
+    'hathor.nanocontracts.types.Address.isdigit',
+    'hathor.nanocontracts.types.Address.islower',
+    'hathor.nanocontracts.types.Address.isspace',
+    'hathor.nanocontracts.types.Address.istitle',
+    'hathor.nanocontracts.types.Address.isupper',
+    'hathor.nanocontracts.types.Address.join',
+    'hathor.nanocontracts.types.Address.ljust',
+    'hathor.nanocontracts.types.Address.lower',
+    'hathor.nanocontracts.types.Address.lstrip',
+    'hathor.nanocontracts.types.Address.maketrans',
+    'hathor.nanocontracts.types.Address.partition',
+    'hathor.nanocontracts.types.Address.removeprefix',
+    'hathor.nanocontracts.types.Address.removesuffix',
+    'hathor.nanocontracts.types.Address.replace',
+    'hathor.nanocontracts.types.Address.rfind',
+    'hathor.nanocontracts.types.Address.rindex',
+    'hathor.nanocontracts.types.Address.rjust',
+    'hathor.nanocontracts.types.Address.rpartition',
+    'hathor.nanocontracts.types.Address.rsplit',
+    'hathor.nanocontracts.types.Address.rstrip',
     'hathor.nanocontracts.types.Address.some_new_attribute',
+    'hathor.nanocontracts.types.Address.split',
+    'hathor.nanocontracts.types.Address.splitlines',
+    'hathor.nanocontracts.types.Address.startswith',
+    'hathor.nanocontracts.types.Address.strip',
+    'hathor.nanocontracts.types.Address.swapcase',
+    'hathor.nanocontracts.types.Address.title',
+    'hathor.nanocontracts.types.Address.translate',
+    'hathor.nanocontracts.types.Address.upper',
+    'hathor.nanocontracts.types.Address.zfill',
     'hathor.nanocontracts.types.Amount.some_new_attribute',
     'hathor.nanocontracts.types.BlueprintId.some_new_attribute',
+    'hathor.nanocontracts.types.ContractId.capitalize',
+    'hathor.nanocontracts.types.ContractId.center',
+    'hathor.nanocontracts.types.ContractId.count',
+    'hathor.nanocontracts.types.ContractId.decode',
+    'hathor.nanocontracts.types.ContractId.endswith',
+    'hathor.nanocontracts.types.ContractId.expandtabs',
+    'hathor.nanocontracts.types.ContractId.find',
+    'hathor.nanocontracts.types.ContractId.fromhex',
+    'hathor.nanocontracts.types.ContractId.hex',
+    'hathor.nanocontracts.types.ContractId.index',
+    'hathor.nanocontracts.types.ContractId.isalnum',
+    'hathor.nanocontracts.types.ContractId.isalpha',
+    'hathor.nanocontracts.types.ContractId.isascii',
+    'hathor.nanocontracts.types.ContractId.isdigit',
+    'hathor.nanocontracts.types.ContractId.islower',
+    'hathor.nanocontracts.types.ContractId.isspace',
+    'hathor.nanocontracts.types.ContractId.istitle',
+    'hathor.nanocontracts.types.ContractId.isupper',
+    'hathor.nanocontracts.types.ContractId.join',
+    'hathor.nanocontracts.types.ContractId.ljust',
+    'hathor.nanocontracts.types.ContractId.lower',
+    'hathor.nanocontracts.types.ContractId.lstrip',
+    'hathor.nanocontracts.types.ContractId.maketrans',
+    'hathor.nanocontracts.types.ContractId.partition',
+    'hathor.nanocontracts.types.ContractId.removeprefix',
+    'hathor.nanocontracts.types.ContractId.removesuffix',
+    'hathor.nanocontracts.types.ContractId.replace',
+    'hathor.nanocontracts.types.ContractId.rfind',
+    'hathor.nanocontracts.types.ContractId.rindex',
+    'hathor.nanocontracts.types.ContractId.rjust',
+    'hathor.nanocontracts.types.ContractId.rpartition',
+    'hathor.nanocontracts.types.ContractId.rsplit',
+    'hathor.nanocontracts.types.ContractId.rstrip',
     'hathor.nanocontracts.types.ContractId.some_new_attribute',
+    'hathor.nanocontracts.types.ContractId.split',
+    'hathor.nanocontracts.types.ContractId.splitlines',
+    'hathor.nanocontracts.types.ContractId.startswith',
+    'hathor.nanocontracts.types.ContractId.strip',
+    'hathor.nanocontracts.types.ContractId.swapcase',
+    'hathor.nanocontracts.types.ContractId.title',
+    'hathor.nanocontracts.types.ContractId.translate',
+    'hathor.nanocontracts.types.ContractId.upper',
+    'hathor.nanocontracts.types.ContractId.zfill',
     'hathor.nanocontracts.types.NCAcquireAuthorityAction.melt',
     'hathor.nanocontracts.types.NCAcquireAuthorityAction.mint',
     'hathor.nanocontracts.types.NCAcquireAuthorityAction.name',
@@ -137,7 +223,49 @@
     'hathor.nanocontracts.types.Timestamp.some_new_attribute',
     'hathor.nanocontracts.types.TokenUid.some_new_attribute',
     'hathor.nanocontracts.types.TxOutputScript.some_new_attribute',
+    'hathor.nanocontracts.types.VertexId.capitalize',
+    'hathor.nanocontracts.types.VertexId.center',
+    'hathor.nanocontracts.types.VertexId.count',
+    'hathor.nanocontracts.types.VertexId.decode',
+    'hathor.nanocontracts.types.VertexId.endswith',
+    'hathor.nanocontracts.types.VertexId.expandtabs',
+    'hathor.nanocontracts.types.VertexId.find',
+    'hathor.nanocontracts.types.VertexId.fromhex',
+    'hathor.nanocontracts.types.VertexId.hex',
+    'hathor.nanocontracts.types.VertexId.index',
+    'hathor.nanocontracts.types.VertexId.isalnum',
+    'hathor.nanocontracts.types.VertexId.isalpha',
+    'hathor.nanocontracts.types.VertexId.isascii',
+    'hathor.nanocontracts.types.VertexId.isdigit',
+    'hathor.nanocontracts.types.VertexId.islower',
+    'hathor.nanocontracts.types.VertexId.isspace',
+    'hathor.nanocontracts.types.VertexId.istitle',
+    'hathor.nanocontracts.types.VertexId.isupper',
+    'hathor.nanocontracts.types.VertexId.join',
+    'hathor.nanocontracts.types.VertexId.ljust',
+    'hathor.nanocontracts.types.VertexId.lower',
+    'hathor.nanocontracts.types.VertexId.lstrip',
+    'hathor.nanocontracts.types.VertexId.maketrans',
+    'hathor.nanocontracts.types.VertexId.partition',
+    'hathor.nanocontracts.types.VertexId.removeprefix',
+    'hathor.nanocontracts.types.VertexId.removesuffix',
+    'hathor.nanocontracts.types.VertexId.replace',
+    'hathor.nanocontracts.types.VertexId.rfind',
+    'hathor.nanocontracts.types.VertexId.rindex',
+    'hathor.nanocontracts.types.VertexId.rjust',
+    'hathor.nanocontracts.types.VertexId.rpartition',
+    'hathor.nanocontracts.types.VertexId.rsplit',
+    'hathor.nanocontracts.types.VertexId.rstrip',
     'hathor.nanocontracts.types.VertexId.some_new_attribute',
+    'hathor.nanocontracts.types.VertexId.split',
+    'hathor.nanocontracts.types.VertexId.splitlines',
+    'hathor.nanocontracts.types.VertexId.startswith',
+    'hathor.nanocontracts.types.VertexId.strip',
+    'hathor.nanocontracts.types.VertexId.swapcase',
+    'hathor.nanocontracts.types.VertexId.title',
+    'hathor.nanocontracts.types.VertexId.translate',
+    'hathor.nanocontracts.types.VertexId.upper',
+    'hathor.nanocontracts.types.VertexId.zfill',
     'hathor.nanocontracts.types.fallback.some_new_attribute',
     'hathor.nanocontracts.types.public.some_new_attribute',
     'hathor.nanocontracts.types.view.some_new_attribute',
diff --git a/tests/nanocontracts/test_fallback_method.py b/tests/nanocontracts/test_fallback_method.py
index 30c7f2242..d1d17d860 100644
--- a/tests/nanocontracts/test_fallback_method.py
+++ b/tests/nanocontracts/test_fallback_method.py
@@ -84,7 +84,7 @@ def setUp(self) -> None:
         self.ctx = Context(
             actions=[NCDepositAction(token_uid=TokenUid(HATHOR_TOKEN_UID), amount=123)],
             vertex=self.get_genesis_tx(),
-            address=self.gen_random_address(),
+            caller_id=self.gen_random_address(),
             timestamp=self.now,
         )
         self.runner.create_contract(self.contract_id, self.blueprint_id, self.ctx)
diff --git a/tests/nanocontracts/test_reentrancy.py b/tests/nanocontracts/test_reentrancy.py
index c5f94df81..434f23b59 100644
--- a/tests/nanocontracts/test_reentrancy.py
+++ b/tests/nanocontracts/test_reentrancy.py
@@ -21,7 +21,7 @@ def initialize(self, ctx: Context) -> None:
 
     @public(allow_deposit=True)
     def deposit(self, ctx: Context) -> None:
-        address = ctx.address
+        address = ctx.caller_id
         action = ctx.get_single_action(HTR_TOKEN_UID)
         assert isinstance(action, NCDepositAction)
         amount = action.amount
@@ -33,7 +33,7 @@ def deposit(self, ctx: Context) -> None:
 
     @public
     def transfer_to(self, ctx: Context, amount: Amount, contract: ContractId, method: str) -> None:
-        address = ctx.address
+        address = ctx.caller_id
         if amount > self.balances.get(address, 0):
             raise InsufficientBalance('insufficient balance')
 
@@ -45,7 +45,7 @@ def transfer_to(self, ctx: Context, amount: Amount, contract: ContractId, method
 
     @public
     def fixed_transfer_to(self, ctx: Context, amount: Amount, contract: ContractId, method: str) -> None:
-        address = ctx.address
+        address = ctx.caller_id
         if amount > self.balances.get(address, 0):
             raise InsufficientBalance('insufficient balance')
 
diff --git a/tests/nanocontracts/test_syscalls.py b/tests/nanocontracts/test_syscalls.py
index cc14ddc71..6bb6574a3 100644
--- a/tests/nanocontracts/test_syscalls.py
+++ b/tests/nanocontracts/test_syscalls.py
@@ -102,7 +102,7 @@ def test_authorities(self) -> None:
                 NCDepositAction(token_uid=token_a_uid, amount=1000),
             ],
             vertex=self.get_genesis_tx(),
-            address=self.gen_random_address(),
+            caller_id=self.gen_random_address(),
             timestamp=0,
         )
 
@@ -112,7 +112,7 @@ def test_authorities(self) -> None:
         ctx_grant = Context(
             actions=[NCGrantAuthorityAction(token_uid=token_a_uid, mint=True, melt=True)],
             vertex=self.get_genesis_tx(),
-            address=self.gen_random_address(),
+            caller_id=self.gen_random_address(),
             timestamp=0,
         )
         self.runner.call_public_method(nc_id, 'nop', ctx_grant)
@@ -120,7 +120,7 @@ def test_authorities(self) -> None:
         ctx = Context(
             actions=[],
             vertex=self.get_genesis_tx(),
-            address=self.gen_random_address(),
+            caller_id=self.gen_random_address(),
             timestamp=0,
         )
 
diff --git a/tests/nanocontracts/test_syscalls_in_view.py b/tests/nanocontracts/test_syscalls_in_view.py
index 3058d4958..e1e0866c2 100644
--- a/tests/nanocontracts/test_syscalls_in_view.py
+++ b/tests/nanocontracts/test_syscalls_in_view.py
@@ -124,7 +124,7 @@ def setUp(self) -> None:
         self.ctx = Context(
             actions=[],
             vertex=self.get_genesis_tx(),
-            address=self.gen_random_address(),
+            caller_id=self.gen_random_address(),
             timestamp=self.now,
         )
 
diff --git a/tests/nanocontracts/test_violations.py b/tests/nanocontracts/test_violations.py
index c17cb0cac..4e716fd4e 100644
--- a/tests/nanocontracts/test_violations.py
+++ b/tests/nanocontracts/test_violations.py
@@ -43,7 +43,7 @@ def test_modify_actions(self) -> None:
         context = Context(
             actions=[],
             vertex=self.tx,
-            address=self.address,
+            caller_id=self.address,
             timestamp=self.now
         )
         self.runner.create_contract(self.contract_id, self.blueprint_id, context)
@@ -57,7 +57,7 @@ def test_modify_vertex(self) -> None:
         context = Context(
             actions=[],
             vertex=self.tx,
-            address=self.address,
+            caller_id=self.address,
             timestamp=self.now
         )
         self.runner.create_contract(self.contract_id, self.blueprint_id, context)
@@ -70,7 +70,7 @@ def test_assign_non_declared_attribute(self) -> None:
         context = Context(
             actions=[],
             vertex=self.tx,
-            address=self.address,
+            caller_id=self.address,
             timestamp=self.now
         )
         self.runner.create_contract(self.contract_id, self.blueprint_id, context)