diff --git a/README.md b/README.md
index 097ddcc..ad54c95 100644
--- a/README.md
+++ b/README.md
@@ -134,6 +134,13 @@ chartmogul.DataSource.destroy(config, uuid='ds_5915ee5a-babd-406b-b8ce-d207133fb
 chartmogul.Customer.create(config, data={})
 chartmogul.Customer.all(config, cursor='cursor==', per_page=20)
 chartmogul.Customer.retrieve(config, uuid='cus_5915ee5a-babd-406b-b8ce-d207133fb4cb')
+chartmogul.Customer.retrieve(config, uuid='cus_5915ee5a-babd-406b-b8ce-d207133fb4cb',
+                             with_overrides=True, attributes_with_history='company,custom.channel')
+# with_overrides and attributes_with_history only work on retrieve; list and search endpoints ignore them
+# attributes_with_history is a comma-separated string of case-sensitive names;
+# custom attributes take the custom. prefix; unknown names return a 422
+# Overrides and history live at the top level of the customer (customer.overrides,
+# customer.historical_values); customer.attributes.overrides is never populated
 chartmogul.Customer.search(config, email='email@email.com')
 chartmogul.Customer.merge(config, data={
   'from': {'customer_uuid': 'cus_5915ee5a-babd-406b-b8ce-d207133fb4cb'},
@@ -150,6 +157,20 @@ chartmogul.Customer.modify(config, uuid='cus_5915ee5a-babd-406b-b8ce-d207133fb4c
   "country": "US",
   "state": "CA",
 })
+chartmogul.Customer.modify(config, uuid='cus_5915ee5a-babd-406b-b8ce-d207133fb4cb', data={
+  "company": "Pinata Technologies",
+  "overrides": {
+    "company": True,
+    "address": True,
+    "attributes": {"custom": {"channel": True}}
+  }
+})
+# An overrides flag set to True protects the value written by the request from
+# later updates; False removes an existing override and restores the field's
+# most recent value from edit history. API writes to an overridden field are
+# reverted unless the request carries a flag for that field. All write calls accept an overrides entry in data:
+# Customer and Contact create/modify, Customer.createContact, and
+# CustomAttributes add/update/remove (including add by email).
 chartmogul.Customer.destroy(config, uuid='cus_5915ee5a-babd-406b-b8ce-d207133fb4cb')
 chartmogul.Customer.subscriptions(config, uuid='cus_5915ee5a-babd-406b-b8ce-d207133fb4cb')
 chartmogul.Customer.connectSubscriptions(config, uuid='cus_5915ee5a-babd-406b-b8ce-d207133fb4cb', data={
@@ -196,11 +217,18 @@ chartmogul.Customer.createTask(config, uuid='cus_5915ee5a-babd-406b-b8ce-d207133
 chartmogul.Contact.create(config, data={})
 chartmogul.Contact.all(config, cursor='aabbcc', per_page=20, customer_uuid='cus_5915ee5a-babd-406b-b8ce-d207133fb4cb', data_source_uuid='ds_fef05d54-47b4-431b-aed2-eb6b9e545430', email='test@example.com', customer_external_id='cus_0001', external_id='con_0001')
 chartmogul.Contact.retrieve(config, uuid='con_5915ee5a-babd-406b-b8ce-d207133fb4cb')
+chartmogul.Contact.retrieve(config, uuid='con_5915ee5a-babd-406b-b8ce-d207133fb4cb',
+                            with_overrides=True, attributes_with_history='title,email')
+# with_overrides and attributes_with_history only work on retrieve; list endpoints ignore them
 chartmogul.Contact.merge(config, into_uuid='con_5915ee5a-babd-406b-b8ce-d207133fb4cb', from_uuid='con_2123290f-09c8-4628-a205-db5596bd58f7')
 chartmogul.Contact.modify(config, uuid='con_5915ee5a-babd-406b-b8ce-d207133fb4cb', data={
   "email": "test@example.com",
   "last_seen": "2025-04-01T12:00:00Z"
 })
+chartmogul.Contact.modify(config, uuid='con_5915ee5a-babd-406b-b8ce-d207133fb4cb', data={
+  "title": "CTO",
+  "overrides": {"title": True}
+})
 chartmogul.Contact.destroy(config, uuid='con_5915ee5a-babd-406b-b8ce-d207133fb4cb')
 chartmogul.Contact.tasks(config, uuid='con_5915ee5a-babd-406b-b8ce-d207133fb4cb', cursor='aabbcc', per_page=20)
 chartmogul.Contact.createTask(config, uuid='con_5915ee5a-babd-406b-b8ce-d207133fb4cb', data={})
@@ -290,10 +318,14 @@ Date filters take ISO 8601 strings. `Task.patch` returns `None` when the API rep
 
 #### [Customer Attributes](https://dev.chartmogul.com/reference/customers/attributes/)
 
-Note that the returned attributes of type date are not parsed and stay in string.
+Note that the returned attributes of type date are not parsed and stay in string. The same applies inside `historical_values` entries: `update_performed_at` stays an ISO 8601 string.
 
 ```python
 chartmogul.Attributes.retrieve(config, uuid='cus_5915ee5a-babd-406b-b8ce-d207133fb4cb')
+chartmogul.Attributes.retrieve(config, uuid='cus_5915ee5a-babd-406b-b8ce-d207133fb4cb',
+                               with_overrides=True, attributes_with_history='custom.channel')
+# attributes_with_history accepts custom attributes only on this endpoint;
+# standard field names like 'company' return a 422
 ```
 
 #### [Tags](https://dev.chartmogul.com/reference/customers/tags/)
@@ -325,6 +357,15 @@ chartmogul.CustomAttributes.add(config, data={
     {'type': 'Integer', 'key': 'age', 'value': 8}
   ]
 })
+chartmogul.CustomAttributes.add(config, uuid='cus_5915ee5a-babd-406b-b8ce-d207133fb4cb', data={
+  'custom': [
+    {'type': 'String', 'key': 'channel', 'value': 'Facebook'}
+  ],
+  'overrides': {'custom': {'channel': True}}
+})
+# Note the overrides shape here is {'custom': {...}} — on Customer create/modify
+# and in Customer.retrieve responses the same flags nest under 'attributes':
+# {'attributes': {'custom': {...}}}
 chartmogul.CustomAttributes.update(config, uuid='cus_5915ee5a-babd-406b-b8ce-d207133fb4cb', data={
   'custom': {
     'age': 20,
@@ -334,6 +375,12 @@ chartmogul.CustomAttributes.update(config, uuid='cus_5915ee5a-babd-406b-b8ce-d20
 chartmogul.CustomAttributes.remove(config, uuid='cus_5915ee5a-babd-406b-b8ce-d207133fb4cb', data={
   'custom': ['CAC']
 })
+chartmogul.CustomAttributes.remove(config, uuid='cus_5915ee5a-babd-406b-b8ce-d207133fb4cb', data={
+  'custom': ['CAC'],
+  'overrides': {'custom': {'CAC': False}}
+})
+# remove keeps overridden attributes unless the request carries a False flag
+# for them; the response message names the ones kept.
 ```
 
 #### [Plans](https://dev.chartmogul.com/reference/plans/)
diff --git a/chartmogul/api/attributes.py b/chartmogul/api/attributes.py
index 3824d8c..a561be7 100644
--- a/chartmogul/api/attributes.py
+++ b/chartmogul/api/attributes.py
@@ -8,12 +8,17 @@ class Attributes(Resource):
     """
 
     _path = "/customers{/uuid}/attributes"
+    _bool_query_params = ["with_overrides"]
 
     class _Schema(Schema):
         tags = fields.List(fields.String())
         stripe = fields.Dict()
         clearbit = fields.Dict()
         custom = fields.Dict()
+        # load_default=None ensures these attributes are always present; the API
+        # omits the keys unless with_overrides / attributes_with_history is passed
+        overrides = fields.Dict(load_default=None)
+        historical_values = fields.Dict(load_default=None)
 
         @post_load
         def make(self, data, **kwargs):
diff --git a/chartmogul/api/contact.py b/chartmogul/api/contact.py
index 7853a20..d293f16 100644
--- a/chartmogul/api/contact.py
+++ b/chartmogul/api/contact.py
@@ -12,6 +12,7 @@ class Contact(Resource):
 
     _path = "/contacts{/uuid}"
     _root_key = "entries"
+    _bool_query_params = ["with_overrides"]
     _many = namedtuple("Contacts", [_root_key, "has_more", "cursor"])
 
     class _Schema(Schema):
@@ -33,6 +34,11 @@ class _Schema(Schema):
         external_id = fields.String(allow_none=True, load_default=None)
         last_seen = fields.DateTime(allow_none=True)
         custom = fields.Dict(allow_none=True)
+        # load_default=None ensures these attributes are always present; on
+        # retrieve the API omits the keys unless with_overrides /
+        # attributes_with_history is passed
+        overrides = fields.Dict(load_default=None)
+        historical_values = fields.Dict(load_default=None)
 
         @post_load
         def make(self, data, **kwargs):
diff --git a/chartmogul/api/custom_attrs.py b/chartmogul/api/custom_attrs.py
index d5b4cc2..a6bf684 100644
--- a/chartmogul/api/custom_attrs.py
+++ b/chartmogul/api/custom_attrs.py
@@ -12,7 +12,12 @@ class CustomAttributes(Resource):
     _path = "/customers{/uuid}/attributes/custom"
 
     class _Schema(Schema):
-        custom = fields.Dict()
+        # load_default=None ensures these attributes are always present; the API
+        # omits custom when a DELETE removes the last custom attribute, and
+        # returns message only on DELETE responses
+        custom = fields.Dict(load_default=None)
+        overrides = fields.Dict(load_default=None)
+        message = fields.String(load_default=None)
 
         @post_load
         def make(self, data, **kwargs):
diff --git a/chartmogul/api/customer.py b/chartmogul/api/customer.py
index f4bff27..7facb95 100644
--- a/chartmogul/api/customer.py
+++ b/chartmogul/api/customer.py
@@ -36,6 +36,7 @@ class Customer(Resource):
 
     _path = "/customers{/uuid}"
     _root_key = "entries"
+    _bool_query_params = ["with_overrides"]
     _many = namedtuple("Customers", [_root_key, "has_more", "cursor"], defaults=[None, None])
 
     class _Schema(Schema):
@@ -71,6 +72,11 @@ class _Schema(Schema):
         currency_sign = fields.String(data_key="currency-sign")
         address = fields.Nested(Address._Schema, allow_none=True, unknown=EXCLUDE)
         website_url = fields.String(allow_none=True)
+        # load_default=None ensures these attributes are always present; on
+        # retrieve the API omits the keys unless with_overrides /
+        # attributes_with_history is passed
+        overrides = fields.Dict(load_default=None)
+        historical_values = fields.Dict(load_default=None)
 
         @post_load
         def make(self, data, **kwargs):
diff --git a/test/api/test_attributes.py b/test/api/test_attributes.py
new file mode 100644
index 0000000..610bc48
--- /dev/null
+++ b/test/api/test_attributes.py
@@ -0,0 +1,72 @@
+import unittest
+from chartmogul import Attributes, Config
+import requests_mock
+
+attributesResponse = {
+    "tags": ["engage", "unit loss"],
+    "stripe": {"uid": 7, "coupon": True},
+    "custom": {"CAC": 213, "salesRep": "Gabi"},
+    "overrides": {"custom": {"salesRep": True}},
+    "historical_values": {
+        "custom": {
+            "salesRep": [
+                {
+                    "value": "Gabi",
+                    "update_performed_at": "2026-01-01T16:58:58Z",
+                    "update_performed_by": "API",
+                    "initial": False,
+                }
+            ]
+        }
+    },
+}
+
+
+class AttributesTestCase(unittest.TestCase):
+    @requests_mock.mock()
+    def test_retrieve(self, mock_requests):
+        plainResponse = {key: attributesResponse[key] for key in ("tags", "stripe", "custom")}
+        mock_requests.register_uri(
+            "GET",
+            "https://api.chartmogul.com/v1/customers/CUSTOMER_UUID/attributes",
+            status_code=200,
+            json=plainResponse,
+        )
+
+        config = Config("token")
+        result = Attributes.retrieve(config, uuid="CUSTOMER_UUID").get()
+
+        self.assertEqual(mock_requests.call_count, 1, "expected call")
+        self.assertEqual(mock_requests.last_request.qs, {})
+        self.assertTrue(isinstance(result, Attributes))
+        self.assertEqual(result.custom, attributesResponse["custom"])
+        self.assertIsNone(result.overrides)
+        self.assertIsNone(result.historical_values)
+
+    # case_sensitive asserts that the SDK preserves attribute name casing in the query
+    @requests_mock.Mocker(case_sensitive=True)
+    def test_retrieve_with_overrides_and_history(self, mock_requests):
+        mock_requests.register_uri(
+            "GET",
+            "https://api.chartmogul.com/v1/customers/CUSTOMER_UUID/attributes",
+            status_code=200,
+            json=attributesResponse,
+        )
+
+        config = Config("token")
+        result = Attributes.retrieve(
+            config,
+            uuid="CUSTOMER_UUID",
+            with_overrides=True,
+            attributes_with_history="custom.salesRep",
+        ).get()
+
+        self.assertEqual(mock_requests.call_count, 1, "expected call")
+        self.assertEqual(
+            mock_requests.last_request.qs,
+            {"with_overrides": ["true"], "attributes_with_history": ["custom.salesRep"]},
+        )
+        self.assertTrue(isinstance(result, Attributes))
+        self.assertEqual(result.custom, attributesResponse["custom"])
+        self.assertEqual(result.overrides, attributesResponse["overrides"])
+        self.assertEqual(result.historical_values, attributesResponse["historical_values"])
diff --git a/test/api/test_contact.py b/test/api/test_contact.py
index 74fd2f6..929662f 100644
--- a/test/api/test_contact.py
+++ b/test/api/test_contact.py
@@ -314,6 +314,8 @@ def test_retrieve(self, mock_requests):
         self.assertTrue(isinstance(expected, Contact))
         self.assertEqual(expected.email, "test@example.com")
         self.assertTrue(isinstance(expected.last_seen, datetime))
+        self.assertIsNone(expected.overrides)
+        self.assertIsNone(expected.historical_values)
 
     @requests_mock.mock()
     def test_tasks(self, mock_requests):
@@ -474,3 +476,77 @@ def test_destroy(self, mock_requests):
         self.assertEqual(mock_requests.call_count, 1, "expected call")
         self.assertEqual(mock_requests.last_request.qs, {})
         self.assertTrue(expected, {})
+
+    @requests_mock.mock()
+    def test_retrieve_with_overrides_and_history(self, mock_requests):
+        overrides = {"title": True}
+        historical_values = {
+            "title": [
+                {
+                    "value": "CEO",
+                    "update_performed_at": "2026-01-01T16:58:58Z",
+                    "update_performed_by": "API",
+                    "initial": False,
+                }
+            ]
+        }
+        mock_requests.register_uri(
+            "GET",
+            "https://api.chartmogul.com/v1/contacts/con_00000000-0000-0000-0000-000000000000",
+            status_code=200,
+            json={**contact, "overrides": overrides, "historical_values": historical_values},
+        )
+
+        config = Config("token")
+        result = Contact.retrieve(
+            config,
+            uuid="con_00000000-0000-0000-0000-000000000000",
+            with_overrides=True,
+            attributes_with_history="title",
+        ).get()
+
+        self.assertEqual(mock_requests.call_count, 1, "expected call")
+        self.assertEqual(
+            mock_requests.last_request.qs,
+            {"with_overrides": ["true"], "attributes_with_history": ["title"]},
+        )
+        self.assertEqual(result.overrides, overrides)
+        self.assertEqual(result.historical_values, historical_values)
+
+    @requests_mock.mock()
+    def test_modify_with_overrides(self, mock_requests):
+        overrides = {"title": True}
+        mock_requests.register_uri(
+            "PATCH",
+            "https://api.chartmogul.com/v1/contacts/con_00000000-0000-0000-0000-000000000000",
+            status_code=200,
+            json={**contact, "overrides": overrides},
+        )
+
+        jsonRequest = {"title": "CTO", "overrides": overrides}
+        config = Config("token")
+        result = Contact.modify(
+            config, uuid="con_00000000-0000-0000-0000-000000000000", data=jsonRequest
+        ).get()
+
+        self.assertEqual(mock_requests.call_count, 1, "expected call")
+        self.assertEqual(mock_requests.last_request.json(), jsonRequest)
+        self.assertEqual(result.overrides, overrides)
+
+    @requests_mock.mock()
+    def test_create_with_overrides(self, mock_requests):
+        overrides = {"title": True}
+        mock_requests.register_uri(
+            "POST",
+            "https://api.chartmogul.com/v1/contacts",
+            status_code=201,
+            json={**contact, "overrides": overrides},
+        )
+
+        jsonRequest = {**createContact, "overrides": overrides}
+        config = Config("token")
+        result = Contact.create(config, data=jsonRequest).get()
+
+        self.assertEqual(mock_requests.call_count, 1, "expected call")
+        self.assertEqual(mock_requests.last_request.json(), jsonRequest)
+        self.assertEqual(result.overrides, overrides)
diff --git a/test/api/test_custom_attrs.py b/test/api/test_custom_attrs.py
index 7b0fa7f..25db21a 100644
--- a/test/api/test_custom_attrs.py
+++ b/test/api/test_custom_attrs.py
@@ -56,6 +56,7 @@
                 "clearbit": {"name": "Acme"},
                 "custom": {"channel": "Facebook"},
             },
+            "overrides": {"attributes": {"custom": {"channel": True}}},
         },
         {
             "id": 13456,
@@ -71,6 +72,7 @@
                 "clearbit": {"name": "Umbrella Corp."},
                 "custom": {"channel": "Facebook"},
             },
+            "overrides": {},
         },
     ]
 }
@@ -87,7 +89,7 @@ def test_add(self, mock_requests):
             "POST",
             "https://api.chartmogul.com/v1/customers/CUSTOMER_UUID/attributes/custom",
             status_code=200,
-            json=simpleJSONResult,
+            json={**simpleJSONResult, "overrides": {}},
         )
 
         expected = CustomAttributes(**simpleJSONResult)
@@ -104,21 +106,109 @@ def test_add(self, mock_requests):
         self.assertEqual(result.custom["convertedAt"], expected.custom["convertedAt"])
         self.assertEqual(result.custom["pro"], expected.custom["pro"])
         self.assertEqual(result.custom["salesRep"], expected.custom["salesRep"])
+        self.assertEqual(result.overrides, {})
+        self.assertIsNone(result.message)
 
     @requests_mock.mock()
     def test_add_to_email(self, mock_requests):
         mock_requests.register_uri(
             "POST",
-            "https://api.chartmogul.com/v1/customers/CUSTOMER_UUID/attributes/custom",
+            "https://api.chartmogul.com/v1/customers/attributes/custom",
             status_code=200,
             json=jsonResponse2,
         )
 
         config = Config("token")
-        result = CustomAttributes.add(config, uuid="CUSTOMER_UUID", data=jsonRequest2).get()
+        result = CustomAttributes.add_by_email(config, data=jsonRequest2).get()
 
         self.assertEqual(mock_requests.call_count, 1, "expected call")
         self.assertEqual(mock_requests.last_request.qs, {})
         self.assertEqual(mock_requests.last_request.json(), jsonRequest2)
-        # No comparison, because unicode strings, dates, serialization order etc.
-        # vary on different Python versions.
+        self.assertEqual(result.entries[0].overrides, {"attributes": {"custom": {"channel": True}}})
+        self.assertEqual(result.entries[1].overrides, {})
+
+    @requests_mock.mock()
+    def test_add_with_overrides(self, mock_requests):
+        overrides = {"custom": {"channel": True}}
+        mock_requests.register_uri(
+            "POST",
+            "https://api.chartmogul.com/v1/customers/CUSTOMER_UUID/attributes/custom",
+            status_code=200,
+            json={"custom": {"channel": "Facebook"}, "overrides": overrides},
+        )
+
+        jsonRequest = {
+            "custom": [{"type": "String", "key": "channel", "value": "Facebook"}],
+            "overrides": overrides,
+        }
+        config = Config("token")
+        result = CustomAttributes.add(config, uuid="CUSTOMER_UUID", data=jsonRequest).get()
+
+        self.assertEqual(mock_requests.call_count, 1, "expected call")
+        self.assertEqual(mock_requests.last_request.json(), jsonRequest)
+        self.assertEqual(result.custom, {"channel": "Facebook"})
+        self.assertEqual(result.overrides, overrides)
+
+    @requests_mock.mock()
+    def test_update_with_overrides(self, mock_requests):
+        overrides = {"custom": {"channel": True}}
+        mock_requests.register_uri(
+            "PUT",
+            "https://api.chartmogul.com/v1/customers/CUSTOMER_UUID/attributes/custom",
+            status_code=200,
+            json={"custom": {"channel": "Twitter"}, "overrides": overrides},
+        )
+
+        jsonRequest = {"custom": {"channel": "Twitter"}, "overrides": overrides}
+        config = Config("token")
+        result = CustomAttributes.update(config, uuid="CUSTOMER_UUID", data=jsonRequest).get()
+
+        self.assertEqual(mock_requests.call_count, 1, "expected call")
+        self.assertEqual(mock_requests.last_request.json(), jsonRequest)
+        self.assertEqual(result.custom, {"channel": "Twitter"})
+        self.assertEqual(result.overrides, overrides)
+
+    @requests_mock.mock()
+    def test_remove_with_overrides_and_message(self, mock_requests):
+        mock_requests.register_uri(
+            "DELETE",
+            "https://api.chartmogul.com/v1/customers/CUSTOMER_UUID/attributes/custom",
+            status_code=202,
+            json={
+                "custom": {"channel": "Facebook"},
+                "overrides": {},
+                "message": "Custom attributes deleted from customer",
+            },
+        )
+
+        jsonRequest = {"custom": ["age"], "overrides": {"custom": {"age": False}}}
+        config = Config("token")
+        result = CustomAttributes.remove(config, uuid="CUSTOMER_UUID", data=jsonRequest).get()
+
+        self.assertEqual(mock_requests.call_count, 1, "expected call")
+        self.assertEqual(mock_requests.last_request.json(), jsonRequest)
+        self.assertEqual(result.custom, {"channel": "Facebook"})
+        self.assertEqual(result.overrides, {})
+        self.assertEqual(result.message, "Custom attributes deleted from customer")
+
+    @requests_mock.mock()
+    def test_remove_last_attribute_omits_custom(self, mock_requests):
+        mock_requests.register_uri(
+            "DELETE",
+            "https://api.chartmogul.com/v1/customers/CUSTOMER_UUID/attributes/custom",
+            status_code=202,
+            json={
+                "overrides": {},
+                "message": "Custom attributes deleted from customer",
+            },
+        )
+
+        config = Config("token")
+        result = CustomAttributes.remove(
+            config, uuid="CUSTOMER_UUID", data={"custom": ["age"]}
+        ).get()
+
+        self.assertEqual(mock_requests.call_count, 1, "expected call")
+        self.assertIsNone(result.custom)
+        self.assertEqual(result.overrides, {})
+        self.assertEqual(result.message, "Custom attributes deleted from customer")
diff --git a/test/api/test_customer.py b/test/api/test_customer.py
index 7cf6f2e..6536920 100644
--- a/test/api/test_customer.py
+++ b/test/api/test_customer.py
@@ -521,15 +521,35 @@ def test_create(self, mock_requests):
         mock_requests.register_uri(
             "POST",
             "https://api.chartmogul.com/v1/customers",
+            status_code=201,
+            json={**entry, "overrides": {}},
+        )
+
+        config = Config("token")
+        result = Customer.create(config, data=createCustomer).get()
+        self.assertEqual(mock_requests.call_count, 1, "expected call")
+        self.assertEqual(mock_requests.last_request.qs, {})
+        self.assertEqual(mock_requests.last_request.json(), sentCreateExpected)
+        self.assertEqual(result.overrides, {})
+        self.assertIsNone(result.historical_values)
+
+    @requests_mock.mock()
+    def test_retrieve(self, mock_requests):
+        mock_requests.register_uri(
+            "GET",
+            "https://api.chartmogul.com/v1/customers/cus_5915ee5a-babd-406b-b8ce-d207133fb4cb",
             status_code=200,
             json=entry,
         )
 
         config = Config("token")
-        Customer.create(config, data=createCustomer).get()
+        result = Customer.retrieve(config, uuid="cus_5915ee5a-babd-406b-b8ce-d207133fb4cb").get()
+
         self.assertEqual(mock_requests.call_count, 1, "expected call")
         self.assertEqual(mock_requests.last_request.qs, {})
-        self.assertEqual(mock_requests.last_request.json(), sentCreateExpected)
+        self.assertTrue(isinstance(result, Customer))
+        self.assertIsNone(result.overrides)
+        self.assertIsNone(result.historical_values)
 
     @requests_mock.mock()
     def test_search(self, mock_requests):
@@ -928,3 +948,109 @@ def test_createTask(self, mock_requests):
         self.assertEqual(mock_requests.last_request.qs, {})
         self.assertEqual(mock_requests.last_request.json(), createTask)
         self.assertTrue(isinstance(expected, Task))
+
+    # case_sensitive asserts that the SDK preserves attribute name casing in the query
+    @requests_mock.Mocker(case_sensitive=True)
+    def test_retrieve_with_overrides_and_history(self, mock_requests):
+        overrides = {"company": True, "attributes": {"custom": {"salesRep": True}}}
+        historical_values = {
+            "company": [
+                {
+                    "value": "Example Company",
+                    "update_performed_at": "2026-01-01T16:58:58Z",
+                    "update_performed_by": "API",
+                    "initial": False,
+                }
+            ],
+            "attributes": {
+                "custom": {
+                    "salesRep": [
+                        {
+                            "value": "Gabi",
+                            "update_performed_at": None,
+                            "update_performed_by": None,
+                            "initial": True,
+                        }
+                    ]
+                }
+            },
+        }
+        mock_requests.register_uri(
+            "GET",
+            "https://api.chartmogul.com/v1/customers/cus_00000000-0000-0000-0000-000000000000",
+            status_code=200,
+            json={**entry, "overrides": overrides, "historical_values": historical_values},
+        )
+
+        config = Config("token")
+        result = Customer.retrieve(
+            config,
+            uuid="cus_00000000-0000-0000-0000-000000000000",
+            with_overrides=True,
+            attributes_with_history="company,custom.salesRep",
+        ).get()
+
+        self.assertEqual(mock_requests.call_count, 1, "expected call")
+        self.assertEqual(
+            mock_requests.last_request.qs,
+            {"with_overrides": ["true"], "attributes_with_history": ["company,custom.salesRep"]},
+        )
+        self.assertEqual(result.overrides, overrides)
+        self.assertEqual(result.historical_values, historical_values)
+
+    @requests_mock.mock()
+    def test_create_with_overrides(self, mock_requests):
+        overrides = {"company": True, "attributes": {"custom": {"channel": True}}}
+        mock_requests.register_uri(
+            "POST",
+            "https://api.chartmogul.com/v1/customers",
+            status_code=201,
+            json={**entry, "overrides": overrides},
+        )
+
+        config = Config("token")
+        result = Customer.create(config, data={**createCustomer, "overrides": overrides}).get()
+
+        self.assertEqual(mock_requests.call_count, 1, "expected call")
+        self.assertEqual(mock_requests.last_request.json()["overrides"], overrides)
+        self.assertEqual(result.overrides, overrides)
+
+    @requests_mock.mock()
+    def test_modify_with_overrides(self, mock_requests):
+        overrides = {"company": True, "attributes": {"custom": {"channel": True}}}
+        mock_requests.register_uri(
+            "PATCH",
+            "https://api.chartmogul.com/v1/customers/cus_5915ee5a-babd-406b-b8ce-d207133fb4cb",
+            status_code=200,
+            json={**entry, "overrides": overrides},
+        )
+
+        jsonRequest = {"company": "Pinata Technologies", "overrides": overrides}
+        config = Config("token")
+        result = Customer.modify(
+            config, uuid="cus_5915ee5a-babd-406b-b8ce-d207133fb4cb", data=jsonRequest
+        ).get()
+
+        self.assertEqual(mock_requests.call_count, 1, "expected call")
+        self.assertEqual(mock_requests.last_request.json(), jsonRequest)
+        self.assertEqual(result.overrides, overrides)
+
+    @requests_mock.mock()
+    def test_createContact_with_overrides(self, mock_requests):
+        overrides = {"title": True}
+        mock_requests.register_uri(
+            "POST",
+            "https://api.chartmogul.com/v1/customers/cus_00000000-0000-0000-0000-000000000000/contacts",
+            status_code=201,
+            json={**contact, "overrides": overrides},
+        )
+
+        jsonRequest = {**createContact, "overrides": overrides}
+        config = Config("token")
+        result = Customer.createContact(
+            config, uuid="cus_00000000-0000-0000-0000-000000000000", data=jsonRequest
+        ).get()
+
+        self.assertEqual(mock_requests.call_count, 1, "expected call")
+        self.assertEqual(mock_requests.last_request.json(), jsonRequest)
+        self.assertEqual(result.overrides, overrides)