diff --git a/changelog/1263.fixed.md b/changelog/1263.fixed.md
new file mode 100644
index 000000000..f2a23fd7e
--- /dev/null
+++ b/changelog/1263.fixed.md
@@ -0,0 +1 @@
+Fixed `client.branch.validate()` and `infrahubctl branch validate`, which raised a `GraphQLError` against every supported Infrahub server because the mutation requested a `messages` field that was removed from `BranchValidate` in Infrahub 1.1.0.
diff --git a/infrahub_sdk/branch.py b/infrahub_sdk/branch.py
index b310522e4..4d760573d 100644
--- a/infrahub_sdk/branch.py
+++ b/infrahub_sdk/branch.py
@@ -133,14 +133,7 @@ async def validate(self, branch_name: str) -> BranchData:
             }
         }
 
-        query_data = {
-            "ok": None,
-            "messages": None,
-            "object": {
-                "id": None,
-                "name": None,
-            },
-        }
+        query_data = {"ok": None}
 
         query = Mutation(mutation="BranchValidate", input_data=input_data, query=query_data)
         response = await self.client.execute_graphql(query=query.render(), tracker="mutation-branch-validate")
@@ -288,14 +281,7 @@ def validate(self, branch_name: str) -> BranchData:
             }
         }
 
-        query_data = {
-            "ok": None,
-            "messages": None,
-            "object": {
-                "id": None,
-                "name": None,
-            },
-        }
+        query_data = {"ok": None}
 
         query = Mutation(mutation="BranchValidate", input_data=input_data, query=query_data)
         response = self.client.execute_graphql(query=query.render(), tracker="mutation-branch-validate")
diff --git a/tests/integration/test_infrahub_client.py b/tests/integration/test_infrahub_client.py
index 54be643ac..bc39c2320 100644
--- a/tests/integration/test_infrahub_client.py
+++ b/tests/integration/test_infrahub_client.py
@@ -63,6 +63,9 @@ async def test_branch_delete(self, client: InfrahubClient, base_dataset: None) -
         assert async_branch in pre_delete
         assert async_branch not in post_delete
 
+    async def test_branch_validate(self, client: InfrahubClient, base_dataset: None) -> None:
+        assert await client.branch.validate(branch_name="branch01") is True
+
     async def test_get_all(self, client: InfrahubClient, base_dataset: None) -> None:
         nodes = await client.all(kind=TESTING_CAT)
         assert len(nodes) == 2
diff --git a/tests/integration/test_infrahub_client_sync.py b/tests/integration/test_infrahub_client_sync.py
index 34c91a446..57d7c842e 100644
--- a/tests/integration/test_infrahub_client_sync.py
+++ b/tests/integration/test_infrahub_client_sync.py
@@ -59,6 +59,9 @@ def test_branch_delete(self, client_sync: InfrahubClientSync, base_dataset: None
         assert sync_branch in pre_delete
         assert sync_branch not in post_delete
 
+    def test_branch_validate(self, client_sync: InfrahubClientSync, base_dataset: None) -> None:
+        assert client_sync.branch.validate(branch_name="sync-branch01") is True
+
     def test_get_all(self, client_sync: InfrahubClientSync, base_dataset: None) -> None:
         nodes = client_sync.all(kind=TESTING_CAT)
         assert len(nodes) == 2
diff --git a/tests/unit/sdk/test_branch.py b/tests/unit/sdk/test_branch.py
index a86182e9e..87eeadd66 100644
--- a/tests/unit/sdk/test_branch.py
+++ b/tests/unit/sdk/test_branch.py
@@ -49,6 +49,33 @@ async def test_get_branches(clients: BothClients, mock_branches_list_query: HTTP
     assert isinstance(branches["main"], BranchData)
 
 
+@pytest.mark.parametrize("client_type", client_types)
+async def test_branch_validate_query_excludes_removed_fields(
+    httpx_mock: HTTPXMock, clients: BothClients, client_type: str
+) -> None:
+    """validate() must only request fields the BranchValidate mutation still exposes.
+
+    The server removed the `messages` field from BranchValidate, so the rendered
+    mutation must not request it, otherwise the server rejects the whole query.
+    """
+    httpx_mock.add_response(
+        method="POST",
+        json={"data": {"BranchValidate": {"ok": True}}},
+        match_headers={"X-Infrahub-Tracker": "mutation-branch-validate"},
+    )
+
+    if client_type == "standard":
+        result = await clients.standard.branch.validate(branch_name="branch01")
+    else:
+        result = clients.sync.branch.validate(branch_name="branch01")
+
+    assert result is True
+
+    post_requests = [r for r in httpx_mock.get_requests() if r.method == "POST"]
+    assert len(post_requests) == 1
+    assert b"messages" not in post_requests[0].content
+
+
 @pytest.mark.parametrize("client_type", client_types)
 async def test_branch_merge_enforces_minimum_timeout(
     httpx_mock: HTTPXMock, clients: BothClients, client_type: str