From 01f7f33635008d38080aa6c3e70c50e582686ff5 Mon Sep 17 00:00:00 2001
From: Aditya Pradhan <contact.adityapradhan.me@gmail.com>
Date: Mon, 23 Feb 2026 15:58:38 +0530
Subject: [PATCH 01/15] fix(multivariate): Handled missing
 default_percentage_allocation in option validation

---
 api/features/multivariate/serializers.py      |  3 +-
 .../test_integration_multivariate.py          | 33 +++++++++++++++++++
 2 files changed, 35 insertions(+), 1 deletion(-)

diff --git a/api/features/multivariate/serializers.py b/api/features/multivariate/serializers.py
index 6c04cb5ac68b..e8daa80cd11a 100644
--- a/api/features/multivariate/serializers.py
+++ b/api/features/multivariate/serializers.py
@@ -65,7 +65,8 @@ def validate(self, attrs):  # type: ignore[no-untyped-def]
             or 0
         )
         total_percentage_allocation = (
-            total_sibling_percentage_allocation + attrs["default_percentage_allocation"]
+            total_sibling_percentage_allocation
+            + attrs.get("default_percentage_allocation", 100)
         )
 
         if total_percentage_allocation > 100:
diff --git a/api/tests/integration/features/multivariate/test_integration_multivariate.py b/api/tests/integration/features/multivariate/test_integration_multivariate.py
index 49effb4c8ff9..a5cfe3d55e85 100644
--- a/api/tests/integration/features/multivariate/test_integration_multivariate.py
+++ b/api/tests/integration/features/multivariate/test_integration_multivariate.py
@@ -39,6 +39,39 @@ def test_can_create_mv_option(client, project, mv_option_50_percent, feature):
     assert response.json()["id"]
     assert set(data.items()).issubset(set(response.json().items()))
 
+@pytest.mark.parametrize(
+    "client",
+    [lazy_fixture("admin_master_api_key_client"), lazy_fixture("admin_client")],
+)
+def test_create_mv_option_without_default_percentage_allocation_uses_default(
+    client: APIClient,
+    project: int,
+    feature: int,
+) -> None:
+    # Given
+    url = reverse(
+        "api-v1:projects:feature-mv-options-list",
+        args=[project, feature],
+    )
+    data = {
+        "type": "unicode",
+        "feature": feature,
+        "string_value": "test_value",
+        # Note: default_percentage_allocation is intentionally omitted
+    }
+
+    # When
+    response = client.post(
+        url,
+        data=json.dumps(data),
+        content_type="application/json",
+    )
+
+    # Then
+    assert response.status_code == status.HTTP_201_CREATED
+    assert response.json()["id"]
+    assert response.json()["default_percentage_allocation"] == 100
+
 
 @pytest.mark.parametrize(
     "client, feature_id",

From 2c2c0422e00e554a7d113692b0b99aecec804921 Mon Sep 17 00:00:00 2001
From: "pre-commit-ci[bot]"
 <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Date: Mon, 23 Feb 2026 10:44:12 +0000
Subject: [PATCH 02/15] [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci
---
 api/features/multivariate/serializers.py                     | 5 ++---
 .../features/multivariate/test_integration_multivariate.py   | 1 +
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/api/features/multivariate/serializers.py b/api/features/multivariate/serializers.py
index e8daa80cd11a..7de804edbf8c 100644
--- a/api/features/multivariate/serializers.py
+++ b/api/features/multivariate/serializers.py
@@ -64,9 +64,8 @@ def validate(self, attrs):  # type: ignore[no-untyped-def]
             )["total_percentage_allocation"]
             or 0
         )
-        total_percentage_allocation = (
-            total_sibling_percentage_allocation
-            + attrs.get("default_percentage_allocation", 100)
+        total_percentage_allocation = total_sibling_percentage_allocation + attrs.get(
+            "default_percentage_allocation", 100
         )
 
         if total_percentage_allocation > 100:
diff --git a/api/tests/integration/features/multivariate/test_integration_multivariate.py b/api/tests/integration/features/multivariate/test_integration_multivariate.py
index a5cfe3d55e85..30aa61b9a798 100644
--- a/api/tests/integration/features/multivariate/test_integration_multivariate.py
+++ b/api/tests/integration/features/multivariate/test_integration_multivariate.py
@@ -39,6 +39,7 @@ def test_can_create_mv_option(client, project, mv_option_50_percent, feature):
     assert response.json()["id"]
     assert set(data.items()).issubset(set(response.json().items()))
 
+
 @pytest.mark.parametrize(
     "client",
     [lazy_fixture("admin_master_api_key_client"), lazy_fixture("admin_client")],

From 69310cfb9079c5d413fb94d6a54acab728fa32c9 Mon Sep 17 00:00:00 2001
From: Aditya Pradhan <contact.adityapradhan.me@gmail.com>
Date: Mon, 23 Feb 2026 16:26:25 +0530
Subject: [PATCH 03/15] fix(multivariate): Handled update operation with
 missing default_percentage_allocation

---
 api/features/multivariate/serializers.py      | 11 +++++--
 .../test_integration_multivariate.py          | 32 +++++++++++++++++++
 2 files changed, 41 insertions(+), 2 deletions(-)

diff --git a/api/features/multivariate/serializers.py b/api/features/multivariate/serializers.py
index 7de804edbf8c..6759b0400abb 100644
--- a/api/features/multivariate/serializers.py
+++ b/api/features/multivariate/serializers.py
@@ -58,14 +58,21 @@ class Meta(NestedMultivariateFeatureOptionSerializer.Meta):
 
     def validate(self, attrs):  # type: ignore[no-untyped-def]
         attrs = super().validate(attrs)
+
+        # For updates, use existing instance value; for creates, use model default
+        default_allocation = (
+            self.instance.default_percentage_allocation if self.instance else 100
+        )
+
         total_sibling_percentage_allocation = (
             self._get_siblings(attrs["feature"]).aggregate(
                 total_percentage_allocation=Sum("default_percentage_allocation")
             )["total_percentage_allocation"]
             or 0
         )
-        total_percentage_allocation = total_sibling_percentage_allocation + attrs.get(
-            "default_percentage_allocation", 100
+        total_percentage_allocation = (
+            total_sibling_percentage_allocation
+            + attrs.get("default_percentage_allocation", default_allocation)
         )
 
         if total_percentage_allocation > 100:
diff --git a/api/tests/integration/features/multivariate/test_integration_multivariate.py b/api/tests/integration/features/multivariate/test_integration_multivariate.py
index 30aa61b9a798..9c16cb27482d 100644
--- a/api/tests/integration/features/multivariate/test_integration_multivariate.py
+++ b/api/tests/integration/features/multivariate/test_integration_multivariate.py
@@ -73,6 +73,38 @@ def test_create_mv_option_without_default_percentage_allocation_uses_default(
     assert response.json()["id"]
     assert response.json()["default_percentage_allocation"] == 100
 
+@pytest.mark.parametrize(
+    "client",
+    [lazy_fixture("admin_master_api_key_client"), lazy_fixture("admin_client")],
+)
+def test_partial_update_mv_option_without_default_percentage_allocation_uses_existing_value(
+    client: APIClient,
+    project: int,
+    feature: int,
+    mv_option_50_percent: int,
+) -> None:
+    # Given
+    url = reverse(
+        "api-v1:projects:feature-mv-options-detail",
+        args=[project, feature, mv_option_50_percent],
+    )
+    data = {
+        "string_value": "updated_value",
+        # Note: default_percentage_allocation is intentionally omitted
+    }
+
+    # When
+    response = client.patch(
+        url,
+        data=json.dumps(data),
+        content_type="application/json",
+    )
+
+    # Then
+    assert response.status_code == status.HTTP_200_OK
+    assert response.json()["string_value"] == "updated_value"
+    # Should retain original 50% allocation, not default to 100
+    assert response.json()["default_percentage_allocation"] == 50
 
 @pytest.mark.parametrize(
     "client, feature_id",

From ea26d31ce9b0a9607c135f9c918884f65053c818 Mon Sep 17 00:00:00 2001
From: "pre-commit-ci[bot]"
 <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Date: Mon, 23 Feb 2026 10:56:44 +0000
Subject: [PATCH 04/15] [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci
---
 api/features/multivariate/serializers.py                     | 5 ++---
 .../features/multivariate/test_integration_multivariate.py   | 2 ++
 2 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/api/features/multivariate/serializers.py b/api/features/multivariate/serializers.py
index 6759b0400abb..bae1ea46a055 100644
--- a/api/features/multivariate/serializers.py
+++ b/api/features/multivariate/serializers.py
@@ -70,9 +70,8 @@ def validate(self, attrs):  # type: ignore[no-untyped-def]
             )["total_percentage_allocation"]
             or 0
         )
-        total_percentage_allocation = (
-            total_sibling_percentage_allocation
-            + attrs.get("default_percentage_allocation", default_allocation)
+        total_percentage_allocation = total_sibling_percentage_allocation + attrs.get(
+            "default_percentage_allocation", default_allocation
         )
 
         if total_percentage_allocation > 100:
diff --git a/api/tests/integration/features/multivariate/test_integration_multivariate.py b/api/tests/integration/features/multivariate/test_integration_multivariate.py
index 9c16cb27482d..ff9067f8a34e 100644
--- a/api/tests/integration/features/multivariate/test_integration_multivariate.py
+++ b/api/tests/integration/features/multivariate/test_integration_multivariate.py
@@ -73,6 +73,7 @@ def test_create_mv_option_without_default_percentage_allocation_uses_default(
     assert response.json()["id"]
     assert response.json()["default_percentage_allocation"] == 100
 
+
 @pytest.mark.parametrize(
     "client",
     [lazy_fixture("admin_master_api_key_client"), lazy_fixture("admin_client")],
@@ -106,6 +107,7 @@ def test_partial_update_mv_option_without_default_percentage_allocation_uses_exi
     # Should retain original 50% allocation, not default to 100
     assert response.json()["default_percentage_allocation"] == 50
 
+
 @pytest.mark.parametrize(
     "client, feature_id",
     [

From 39af977ae01067edf9618f111f04db5df3c6f452 Mon Sep 17 00:00:00 2001
From: Aditya Pradhan <contact.adityapradhan.me@gmail.com>
Date: Mon, 23 Feb 2026 20:45:46 +0530
Subject: [PATCH 05/15] fix(multivariate): Handled update operation with
 missing feature

---
 api/features/multivariate/serializers.py             | 12 +++++++-----
 .../multivariate/test_integration_multivariate.py    |  8 ++------
 2 files changed, 9 insertions(+), 11 deletions(-)

diff --git a/api/features/multivariate/serializers.py b/api/features/multivariate/serializers.py
index bae1ea46a055..9ce98323ae99 100644
--- a/api/features/multivariate/serializers.py
+++ b/api/features/multivariate/serializers.py
@@ -59,19 +59,21 @@ class Meta(NestedMultivariateFeatureOptionSerializer.Meta):
     def validate(self, attrs):  # type: ignore[no-untyped-def]
         attrs = super().validate(attrs)
 
-        # For updates, use existing instance value; for creates, use model default
-        default_allocation = (
+        # For partial updated, use existing instance value as fallback
+        feature = attrs.get("feature", self.instance.feature if self.instance else None)
+        default_allocation = attrs.get(
+            "default_percentage_allocation",
             self.instance.default_percentage_allocation if self.instance else 100
         )
 
         total_sibling_percentage_allocation = (
-            self._get_siblings(attrs["feature"]).aggregate(
+            self._get_siblings(feature).aggregate(
                 total_percentage_allocation=Sum("default_percentage_allocation")
             )["total_percentage_allocation"]
             or 0
         )
-        total_percentage_allocation = total_sibling_percentage_allocation + attrs.get(
-            "default_percentage_allocation", default_allocation
+        total_percentage_allocation = (
+            total_sibling_percentage_allocation + default_allocation
         )
 
         if total_percentage_allocation > 100:
diff --git a/api/tests/integration/features/multivariate/test_integration_multivariate.py b/api/tests/integration/features/multivariate/test_integration_multivariate.py
index ff9067f8a34e..ece02206e620 100644
--- a/api/tests/integration/features/multivariate/test_integration_multivariate.py
+++ b/api/tests/integration/features/multivariate/test_integration_multivariate.py
@@ -39,7 +39,6 @@ def test_can_create_mv_option(client, project, mv_option_50_percent, feature):
     assert response.json()["id"]
     assert set(data.items()).issubset(set(response.json().items()))
 
-
 @pytest.mark.parametrize(
     "client",
     [lazy_fixture("admin_master_api_key_client"), lazy_fixture("admin_client")],
@@ -58,7 +57,6 @@ def test_create_mv_option_without_default_percentage_allocation_uses_default(
         "type": "unicode",
         "feature": feature,
         "string_value": "test_value",
-        # Note: default_percentage_allocation is intentionally omitted
     }
 
     # When
@@ -78,7 +76,7 @@ def test_create_mv_option_without_default_percentage_allocation_uses_default(
     "client",
     [lazy_fixture("admin_master_api_key_client"), lazy_fixture("admin_client")],
 )
-def test_partial_update_mv_option_without_default_percentage_allocation_uses_existing_value(
+def test_partial_update_mv_option_without_feature_and_allocation_uses_existing_values(
     client: APIClient,
     project: int,
     feature: int,
@@ -91,7 +89,6 @@ def test_partial_update_mv_option_without_default_percentage_allocation_uses_exi
     )
     data = {
         "string_value": "updated_value",
-        # Note: default_percentage_allocation is intentionally omitted
     }
 
     # When
@@ -104,9 +101,8 @@ def test_partial_update_mv_option_without_default_percentage_allocation_uses_exi
     # Then
     assert response.status_code == status.HTTP_200_OK
     assert response.json()["string_value"] == "updated_value"
-    # Should retain original 50% allocation, not default to 100
     assert response.json()["default_percentage_allocation"] == 50
-
+    assert response.json()["feature"] == feature
 
 @pytest.mark.parametrize(
     "client, feature_id",

From f706f13b4dc6ad814594a06829525f91dacf9442 Mon Sep 17 00:00:00 2001
From: "pre-commit-ci[bot]"
 <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Date: Mon, 23 Feb 2026 15:16:07 +0000
Subject: [PATCH 06/15] [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci
---
 api/features/multivariate/serializers.py                        | 2 +-
 .../features/multivariate/test_integration_multivariate.py      | 2 ++
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/api/features/multivariate/serializers.py b/api/features/multivariate/serializers.py
index 9ce98323ae99..c708c1b38ae8 100644
--- a/api/features/multivariate/serializers.py
+++ b/api/features/multivariate/serializers.py
@@ -63,7 +63,7 @@ def validate(self, attrs):  # type: ignore[no-untyped-def]
         feature = attrs.get("feature", self.instance.feature if self.instance else None)
         default_allocation = attrs.get(
             "default_percentage_allocation",
-            self.instance.default_percentage_allocation if self.instance else 100
+            self.instance.default_percentage_allocation if self.instance else 100,
         )
 
         total_sibling_percentage_allocation = (
diff --git a/api/tests/integration/features/multivariate/test_integration_multivariate.py b/api/tests/integration/features/multivariate/test_integration_multivariate.py
index ece02206e620..d66dd1d9dc66 100644
--- a/api/tests/integration/features/multivariate/test_integration_multivariate.py
+++ b/api/tests/integration/features/multivariate/test_integration_multivariate.py
@@ -39,6 +39,7 @@ def test_can_create_mv_option(client, project, mv_option_50_percent, feature):
     assert response.json()["id"]
     assert set(data.items()).issubset(set(response.json().items()))
 
+
 @pytest.mark.parametrize(
     "client",
     [lazy_fixture("admin_master_api_key_client"), lazy_fixture("admin_client")],
@@ -104,6 +105,7 @@ def test_partial_update_mv_option_without_feature_and_allocation_uses_existing_v
     assert response.json()["default_percentage_allocation"] == 50
     assert response.json()["feature"] == feature
 
+
 @pytest.mark.parametrize(
     "client, feature_id",
     [

From fcab2815d9d5e830df3b63a8dd10ed6a5fda96b9 Mon Sep 17 00:00:00 2001
From: Aditya Pradhan <contact.adityapradhan.me@gmail.com>
Date: Mon, 23 Feb 2026 21:27:53 +0530
Subject: [PATCH 07/15] fix(multivariate): Handled None feature

---
 api/features/multivariate/serializers.py      |  7 ++
 .../test_integration_multivariate.py          | 84 +++++++++++++++++++
 2 files changed, 91 insertions(+)

diff --git a/api/features/multivariate/serializers.py b/api/features/multivariate/serializers.py
index c708c1b38ae8..f7889ddbca69 100644
--- a/api/features/multivariate/serializers.py
+++ b/api/features/multivariate/serializers.py
@@ -61,6 +61,13 @@ def validate(self, attrs):  # type: ignore[no-untyped-def]
 
         # For partial updated, use existing instance value as fallback
         feature = attrs.get("feature", self.instance.feature if self.instance else None)
+        if feature is None:
+            raise serializers.ValidationError(
+                {
+                    "feature": "Feature is required"
+                }
+            )
+        
         default_allocation = attrs.get(
             "default_percentage_allocation",
             self.instance.default_percentage_allocation if self.instance else 100,
diff --git a/api/tests/integration/features/multivariate/test_integration_multivariate.py b/api/tests/integration/features/multivariate/test_integration_multivariate.py
index d66dd1d9dc66..4fb261f10922 100644
--- a/api/tests/integration/features/multivariate/test_integration_multivariate.py
+++ b/api/tests/integration/features/multivariate/test_integration_multivariate.py
@@ -73,6 +73,41 @@ def test_create_mv_option_without_default_percentage_allocation_uses_default(
     assert response.json()["default_percentage_allocation"] == 100
 
 
+@pytest.mark.parametrize(
+    "client",
+    [lazy_fixture("admin_master_api_key_client"), lazy_fixture("admin_client")],
+)
+def test_create_mv_option_without_default_percentage_allocation_with_existing_sibling_and_total_gt_100_returns_400(  # type: ignore[no-untyped-def]  # noqa: E501
+    client: APIClient,
+    project: int,
+    feature: int,
+    mv_option_50_percent: int,
+) -> None:
+    # Given
+    url = reverse(
+        "api-v1:projects:feature-mv-options-list",
+        args=[project, feature],
+    )
+    data = {
+        "type": "unicode",
+        "feature": feature,
+        "string_value": "another_value",
+    }
+
+    # When
+    response = client.post(
+        url,
+        data=json.dumps(data),
+        content_type="application/json",
+    )
+
+    # Then
+    assert response.status_code == status.HTTP_400_BAD_REQUEST
+    assert response.json()["default_percentage_allocation"] == [
+        "Invalid percentage allocation"
+    ]
+
+
 @pytest.mark.parametrize(
     "client",
     [lazy_fixture("admin_master_api_key_client"), lazy_fixture("admin_client")],
@@ -249,6 +284,55 @@ def test_can_update_default_percentage_allocation(  # type: ignore[no-untyped-de
     assert set(data.items()).issubset(set(response.json().items()))
 
 
+@pytest.mark.parametrize(
+    "client",
+    [lazy_fixture("admin_master_api_key_client"), lazy_fixture("admin_client")],
+)
+def test_partial_update_default_percentage_allocation_that_pushes_the_total_percentage_allocation_over_100_returns_400(  # type: ignore[no-untyped-def]  # noqa: E501
+    project,
+    mv_option_50_percent,
+    client,
+    feature,
+):
+    # First let's create another mv_option with 30 percent allocation
+    url = reverse(
+        "api-v1:projects:feature-mv-options-list",
+        args=[project, feature],
+    )
+    data = {
+        "type": "unicode",
+        "feature": feature,
+        "string_value": "bigger",
+        "default_percentage_allocation": 30,
+    }
+    response = client.post(
+        url,
+        data=json.dumps(data),
+        content_type="application/json",
+    )
+    mv_option_30_percent = response.json()["id"]
+
+    # Next, let's partially update the 30 percent mv option to 51 percent
+    url = reverse(
+        "api-v1:projects:feature-mv-options-detail",
+        args=[project, feature, mv_option_30_percent],
+    )
+    data = {
+        "default_percentage_allocation": 51,
+    }
+    # When
+    response = client.patch(
+        url,
+        data=json.dumps(data),
+        content_type="application/json",
+    )
+    # Then
+    assert response.status_code == status.HTTP_400_BAD_REQUEST
+    assert response.json()["default_percentage_allocation"] == [
+        "Invalid percentage allocation"
+    ]
+
+
 @pytest.mark.parametrize(
     "client",
     [lazy_fixture("admin_master_api_key_client"), lazy_fixture("admin_client")],

From 689c2aa9a8778b6eea849214ba4552808b1f4ead Mon Sep 17 00:00:00 2001
From: "pre-commit-ci[bot]"
 <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Date: Mon, 23 Feb 2026 15:58:14 +0000
Subject: [PATCH 08/15] [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci
---
 api/features/multivariate/serializers.py | 8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

diff --git a/api/features/multivariate/serializers.py b/api/features/multivariate/serializers.py
index f7889ddbca69..cffe8cf72d8f 100644
--- a/api/features/multivariate/serializers.py
+++ b/api/features/multivariate/serializers.py
@@ -62,12 +62,8 @@ def validate(self, attrs):  # type: ignore[no-untyped-def]
         # For partial updated, use existing instance value as fallback
         feature = attrs.get("feature", self.instance.feature if self.instance else None)
         if feature is None:
-            raise serializers.ValidationError(
-                {
-                    "feature": "Feature is required"
-                }
-            )
-        
+            raise serializers.ValidationError({"feature": "Feature is required"})
+
         default_allocation = attrs.get(
             "default_percentage_allocation",
             self.instance.default_percentage_allocation if self.instance else 100,

From 42525554112af12918f4db2347537c491518381c Mon Sep 17 00:00:00 2001
From: Aditya Pradhan <contact.adityapradhan.me@gmail.com>
Date: Mon, 23 Feb 2026 21:35:25 +0530
Subject: [PATCH 09/15] fix(multivariate): Added a clear assertion

---
 .../features/multivariate/test_integration_multivariate.py       | 1 +
 1 file changed, 1 insertion(+)

diff --git a/api/tests/integration/features/multivariate/test_integration_multivariate.py b/api/tests/integration/features/multivariate/test_integration_multivariate.py
index 4fb261f10922..6ee496a4c8d7 100644
--- a/api/tests/integration/features/multivariate/test_integration_multivariate.py
+++ b/api/tests/integration/features/multivariate/test_integration_multivariate.py
@@ -310,6 +310,7 @@ def test_partial_update_default_percentage_allocation_that_pushes_the_total_perc
         data=json.dumps(data),
         content_type="application/json",
     )
+    assert response.status_code == status.HTTP_201_CREATED
     mv_option_30_percent = response.json()["id"]
 
     # Next, let's partially update the 30 percent mv option to 51 percent

From bfbab35fe42fe1f3ab175c2d641f6e2be8dd8e1f Mon Sep 17 00:00:00 2001
From: Aditya Pradhan <contact.adityapradhan.me@gmail.com>
Date: Tue, 24 Feb 2026 22:57:41 +0530
Subject: [PATCH 10/15] fix(multivariate): Review suggestion - Updated the test
 naming convention and added types

---
 .../test_integration_multivariate.py           | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/api/tests/integration/features/multivariate/test_integration_multivariate.py b/api/tests/integration/features/multivariate/test_integration_multivariate.py
index 6ee496a4c8d7..317a1e6a5544 100644
--- a/api/tests/integration/features/multivariate/test_integration_multivariate.py
+++ b/api/tests/integration/features/multivariate/test_integration_multivariate.py
@@ -44,7 +44,7 @@ def test_can_create_mv_option(client, project, mv_option_50_percent, feature):
     "client",
     [lazy_fixture("admin_master_api_key_client"), lazy_fixture("admin_client")],
 )
-def test_create_mv_option_without_default_percentage_allocation_uses_default(
+def test_create_mv_option__without_default_percentage_allocation__uses_default(
     client: APIClient,
     project: int,
     feature: int,
@@ -77,7 +77,7 @@ def test_create_mv_option_without_default_percentage_allocation_uses_default(
     "client",
     [lazy_fixture("admin_master_api_key_client"), lazy_fixture("admin_client")],
 )
-def test_create_mv_option_without_default_percentage_allocation_with_existing_sibling_and_total_gt_100_returns_400(  # type: ignore[no-untyped-def]  # noqa: E501
+def test_create_mv_option__without_default_percentage_allocation_with_existing_sibling_and_total_gt_100__returns_400(  # noqa: E501
     client: APIClient,
     project: int,
     feature: int,
@@ -112,7 +112,7 @@ def test_create_mv_option_without_default_percentage_allocation_with_existing_si
     "client",
     [lazy_fixture("admin_master_api_key_client"), lazy_fixture("admin_client")],
 )
-def test_partial_update_mv_option_without_feature_and_allocation_uses_existing_values(
+def test_partial_update_mv_option__without_feature_and_allocation__uses_existing_values(
     client: APIClient,
     project: int,
     feature: int,
@@ -288,12 +288,12 @@ def test_can_update_default_percentage_allocation(  # type: ignore[no-untyped-de
     "client",
     [lazy_fixture("admin_master_api_key_client"), lazy_fixture("admin_client")],
 )
-def test_partial_update_default_percentage_allocation_that_pushes_the_total_percentage_allocation_over_100_returns_400(  # type: ignore[no-untyped-def]  # noqa: E501
-    project,
-    mv_option_50_percent,
-    client,
-    feature,
-):
+def test_partial_update_default_percentage_allocation__sibling_total_gt_100__returns_400(  # noqa: E501
+    project: int,
+    mv_option_50_percent: int,
+    client: APIClient,
+    feature: int,
+) -> None:
     # First let's create another mv_option with 30 percent allocation
     url = reverse(
         "api-v1:projects:feature-mv-options-list",

From eef3806aa812ff786b040d3045b164c923ff7fab Mon Sep 17 00:00:00 2001
From: Aditya Pradhan <contact.adityapradhan.me@gmail.com>
Date: Wed, 25 Feb 2026 00:05:44 +0530
Subject: [PATCH 11/15] fix(multivariate): Added support for path param feature
 name

---
 api/features/multivariate/serializers.py      | 20 +++++++++--
 .../test_integration_multivariate.py          | 34 +++++++++++++++++++
 2 files changed, 52 insertions(+), 2 deletions(-)

diff --git a/api/features/multivariate/serializers.py b/api/features/multivariate/serializers.py
index cffe8cf72d8f..817a06fa73e4 100644
--- a/api/features/multivariate/serializers.py
+++ b/api/features/multivariate/serializers.py
@@ -59,11 +59,27 @@ class Meta(NestedMultivariateFeatureOptionSerializer.Meta):
     def validate(self, attrs):  # type: ignore[no-untyped-def]
         attrs = super().validate(attrs)
 
-        # For partial updated, use existing instance value as fallback
-        feature = attrs.get("feature", self.instance.feature if self.instance else None)
+        # For partial updates or nested routes, use existing instance or URL value as fallback
+        feature = attrs.get("feature")
+        if feature is None and self.instance is not None:
+            feature = self.instance.feature
+
+        if feature is None:
+            view = self.context.get("view")
+            feature_pk = getattr(view, "kwargs", {}).get("feature_pk") if view else None
+            project_pk = getattr(view, "kwargs", {}).get("project_pk") if view else None
+            if feature_pk is not None:
+                qs = Feature.objects.filter(pk=feature_pk)
+                if project_pk is not None:
+                    qs = qs.filter(project__id=project_pk)
+                feature = qs.first()
+
         if feature is None:
             raise serializers.ValidationError({"feature": "Feature is required"})
 
+        # Ensure feature is always present in validated data (e.g. for creates via nested routes)
+        attrs["feature"] = feature
+
         default_allocation = attrs.get(
             "default_percentage_allocation",
             self.instance.default_percentage_allocation if self.instance else 100,
diff --git a/api/tests/integration/features/multivariate/test_integration_multivariate.py b/api/tests/integration/features/multivariate/test_integration_multivariate.py
index 317a1e6a5544..fbf03ad482c0 100644
--- a/api/tests/integration/features/multivariate/test_integration_multivariate.py
+++ b/api/tests/integration/features/multivariate/test_integration_multivariate.py
@@ -40,6 +40,40 @@ def test_can_create_mv_option(client, project, mv_option_50_percent, feature):
     assert set(data.items()).issubset(set(response.json().items()))
 
 
+@pytest.mark.parametrize(
+    "client",
+    [lazy_fixture("admin_master_api_key_client"), lazy_fixture("admin_client")],
+)
+def test_create_mv_option__without_feature_in_payload__uses_feature_from_url(
+    client: APIClient,
+    project: int,
+    feature: int,
+) -> None:
+    # Given
+    url = reverse(
+        "api-v1:projects:feature-mv-options-list",
+        args=[project, feature],
+    )
+    data = {
+        "type": "unicode",
+        "string_value": "bigger",
+        "default_percentage_allocation": 50,
+    }
+    # When
+    response = client.post(
+        url,
+        data=json.dumps(data),
+        content_type="application/json",
+    )
+    # Then
+    assert response.status_code == status.HTTP_201_CREATED
+    body = response.json()
+    assert body["id"]
+    assert body["feature"] == feature
+    assert body["string_value"] == "bigger"
+    assert body["default_percentage_allocation"] == 50
+
+
 @pytest.mark.parametrize(
     "client",
     [lazy_fixture("admin_master_api_key_client"), lazy_fixture("admin_client")],

From 06c79d096a0fc6cb914fcfa62bcb7ca389fbb8f1 Mon Sep 17 00:00:00 2001
From: Aditya Pradhan <contact.adityapradhan.me@gmail.com>
Date: Wed, 25 Feb 2026 14:02:29 +0530
Subject: [PATCH 12/15] fix(multivariate): Added support for null
 default_percentage_allocation from database

---
 api/features/multivariate/serializers.py      |  8 +++-
 .../test_integration_multivariate.py          | 39 +++++++++++++++++++
 2 files changed, 46 insertions(+), 1 deletion(-)

diff --git a/api/features/multivariate/serializers.py b/api/features/multivariate/serializers.py
index 817a06fa73e4..f080ce346bd3 100644
--- a/api/features/multivariate/serializers.py
+++ b/api/features/multivariate/serializers.py
@@ -80,9 +80,15 @@ def validate(self, attrs):  # type: ignore[no-untyped-def]
         # Ensure feature is always present in validated data (e.g. for creates via nested routes)
         attrs["feature"] = feature
 
+        # Handle legacy records where default_percentage_allocation may be NULL in the database.
+        if self.instance and self.instance.default_percentage_allocation is not None:
+            instance_default_allocation = self.instance.default_percentage_allocation
+        else:
+            instance_default_allocation = 100
+
         default_allocation = attrs.get(
             "default_percentage_allocation",
-            self.instance.default_percentage_allocation if self.instance else 100,
+            instance_default_allocation,
         )
 
         total_sibling_percentage_allocation = (
diff --git a/api/tests/integration/features/multivariate/test_integration_multivariate.py b/api/tests/integration/features/multivariate/test_integration_multivariate.py
index fbf03ad482c0..69df3e1bad26 100644
--- a/api/tests/integration/features/multivariate/test_integration_multivariate.py
+++ b/api/tests/integration/features/multivariate/test_integration_multivariate.py
@@ -7,6 +7,7 @@
 from rest_framework.test import APIClient
 
 from features.models import Feature
+from features.multivariate.models import MultivariateFeatureOption
 from organisations.models import Organisation
 from projects.models import Project
 from users.models import FFAdminUser
@@ -175,6 +176,44 @@ def test_partial_update_mv_option__without_feature_and_allocation__uses_existing
     assert response.json()["feature"] == feature
 
 
+@pytest.mark.parametrize(
+    "client",
+    [lazy_fixture("admin_master_api_key_client"), lazy_fixture("admin_client")],
+)
+def test_partial_update_mv_option__handles_legacy_null_default_percentage_allocation(  # noqa: E501
+    client: APIClient,
+    project: int,
+    feature: int,
+    mv_option_50_percent: int,
+) -> None:
+    # Given
+    # Simulate a legacy database record with a NULL default_percentage_allocation.
+    MultivariateFeatureOption.objects.filter(
+        id=mv_option_50_percent,
+    ).update(default_percentage_allocation=None)
+
+    url = reverse(
+        "api-v1:projects:feature-mv-options-detail",
+        args=[project, feature, mv_option_50_percent],
+    )
+    data = {
+        "string_value": "updated_legacy_value",
+    }
+
+    # When
+    response = client.patch(
+        url,
+        data=json.dumps(data),
+        content_type="application/json",
+    )
+    # Then
+    assert response.status_code == status.HTTP_200_OK
+    body = response.json()
+    assert body["string_value"] == "updated_legacy_value"
+    assert body["default_percentage_allocation"] == 100
+    assert body["feature"] == feature
+
+
 @pytest.mark.parametrize(
     "client, feature_id",
     [

From bd5508b6bcab0485f49340a227ce1bf49daf1a7a Mon Sep 17 00:00:00 2001
From: Aditya Pradhan <contact.adityapradhan.me@gmail.com>
Date: Wed, 25 Feb 2026 14:20:21 +0530
Subject: [PATCH 13/15] fix(multivariate): Added default allocation write

---
 api/features/multivariate/serializers.py | 1 +
 1 file changed, 1 insertion(+)

diff --git a/api/features/multivariate/serializers.py b/api/features/multivariate/serializers.py
index f080ce346bd3..516f7c8f0ef2 100644
--- a/api/features/multivariate/serializers.py
+++ b/api/features/multivariate/serializers.py
@@ -90,6 +90,7 @@ def validate(self, attrs):  # type: ignore[no-untyped-def]
             "default_percentage_allocation",
             instance_default_allocation,
         )
+        attrs["default_percentage_allocation"] = default_allocation
 
         total_sibling_percentage_allocation = (
             self._get_siblings(feature).aggregate(

From 60196d75526a1656eb3183723aadd597dac5e90d Mon Sep 17 00:00:00 2001
From: Aditya Pradhan <contact.adityapradhan.me@gmail.com>
Date: Wed, 25 Feb 2026 14:38:07 +0530
Subject: [PATCH 14/15] fix(multivariate): align MV option validation with
 persistence and add coverage

---
 api/features/multivariate/serializers.py      |  3 ++
 .../test_integration_multivariate.py          | 54 ++++++++++---------
 2 files changed, 31 insertions(+), 26 deletions(-)

diff --git a/api/features/multivariate/serializers.py b/api/features/multivariate/serializers.py
index 516f7c8f0ef2..399d48ece8e6 100644
--- a/api/features/multivariate/serializers.py
+++ b/api/features/multivariate/serializers.py
@@ -55,6 +55,9 @@ def get_control_value(self, obj: dict[str, typing.Any]) -> str | int | bool | No
 class MultivariateFeatureOptionSerializer(NestedMultivariateFeatureOptionSerializer):
     class Meta(NestedMultivariateFeatureOptionSerializer.Meta):
         fields = NestedMultivariateFeatureOptionSerializer.Meta.fields + ("feature",)  # type: ignore[assignment]
+        extra_kwargs = {
+            "feature": {"required": False},
+        }
 
     def validate(self, attrs):  # type: ignore[no-untyped-def]
         attrs = super().validate(attrs)
diff --git a/api/tests/integration/features/multivariate/test_integration_multivariate.py b/api/tests/integration/features/multivariate/test_integration_multivariate.py
index 69df3e1bad26..39969a54ced9 100644
--- a/api/tests/integration/features/multivariate/test_integration_multivariate.py
+++ b/api/tests/integration/features/multivariate/test_integration_multivariate.py
@@ -8,6 +8,7 @@
 
 from features.models import Feature
 from features.multivariate.models import MultivariateFeatureOption
+from features.multivariate.serializers import MultivariateFeatureOptionSerializer
 from organisations.models import Organisation
 from projects.models import Project
 from users.models import FFAdminUser
@@ -181,37 +182,38 @@ def test_partial_update_mv_option__without_feature_and_allocation__uses_existing
     [lazy_fixture("admin_master_api_key_client"), lazy_fixture("admin_client")],
 )
 def test_partial_update_mv_option__handles_legacy_null_default_percentage_allocation(  # noqa: E501
-    client: APIClient,
     project: int,
     feature: int,
     mv_option_50_percent: int,
 ) -> None:
     # Given
-    # Simulate a legacy database record with a NULL default_percentage_allocation.
-    MultivariateFeatureOption.objects.filter(
-        id=mv_option_50_percent,
-    ).update(default_percentage_allocation=None)
-
-    url = reverse(
-        "api-v1:projects:feature-mv-options-detail",
-        args=[project, feature, mv_option_50_percent],
-    )
-    data = {
-        "string_value": "updated_legacy_value",
-    }
-
-    # When
-    response = client.patch(
-        url,
-        data=json.dumps(data),
-        content_type="application/json",
-    )
-    # Then
-    assert response.status_code == status.HTTP_200_OK
-    body = response.json()
-    assert body["string_value"] == "updated_legacy_value"
-    assert body["default_percentage_allocation"] == 100
-    assert body["feature"] == feature
+    # Simulate a legacy instance in memory where default_percentage_allocation is NULL.
+    mv_option = MultivariateFeatureOption.objects.get(id=mv_option_50_percent)
+    mv_option.default_percentage_allocation = None
+
+    serializer = MultivariateFeatureOptionSerializer(
+        instance=mv_option,
+        data={"string_value": "updated_legacy_value"},
+        partial=True,
+        context={
+            "view": type(
+                "View",
+                (),
+                {
+                    "kwargs": {
+                        "project_pk": project,
+                        "feature_pk": feature,
+                    },
+                },
+            )(),
+        },
+    )
+    assert serializer.is_valid(), serializer.errors
+    instance = serializer.save()
+
+    assert instance.string_value == "updated_legacy_value"
+    assert instance.default_percentage_allocation == 100
+    assert instance.feature_id == feature
 
 
 @pytest.mark.parametrize(

From 2929c71482e47634d70bd971d75d9b9f252efd14 Mon Sep 17 00:00:00 2001
From: Aditya Pradhan <contact.adityapradhan.me@gmail.com>
Date: Wed, 25 Feb 2026 15:11:30 +0530
Subject: [PATCH 15/15] fix(multivariate): Added missing test arg

---
 .../features/multivariate/test_integration_multivariate.py       | 1 +
 1 file changed, 1 insertion(+)

diff --git a/api/tests/integration/features/multivariate/test_integration_multivariate.py b/api/tests/integration/features/multivariate/test_integration_multivariate.py
index 39969a54ced9..864370233658 100644
--- a/api/tests/integration/features/multivariate/test_integration_multivariate.py
+++ b/api/tests/integration/features/multivariate/test_integration_multivariate.py
@@ -182,6 +182,7 @@ def test_partial_update_mv_option__without_feature_and_allocation__uses_existing
     [lazy_fixture("admin_master_api_key_client"), lazy_fixture("admin_client")],
 )
 def test_partial_update_mv_option__handles_legacy_null_default_percentage_allocation(  # noqa: E501
+    client: APIClient,
     project: int,
     feature: int,
     mv_option_50_percent: int,