diff --git a/changelog/+async-sync-twin-drift.fixed.md b/changelog/+async-sync-twin-drift.fixed.md
new file mode 100644
index 000000000..4fb0d9fe7
--- /dev/null
+++ b/changelog/+async-sync-twin-drift.fixed.md
@@ -0,0 +1 @@
+Fixed several cases where `InfrahubClientSync` had drifted from `InfrahubClient`: sync `branch.merge` now applies the same 120-second minimum timeout floor as the async client, and sync `create(allow_upsert=True)` now excludes the `hfid` from the mutation payload to avoid server-side upsert overhead. Also corrected an incorrect "feature not supported" message on async artifact fetch and a resource-pool error message typo.
diff --git a/docs/docs/python-sdk/sdk_ref/infrahub_sdk/client.mdx b/docs/docs/python-sdk/sdk_ref/infrahub_sdk/client.mdx
index 038599660..0d9445a17 100644
--- a/docs/docs/python-sdk/sdk_ref/infrahub_sdk/client.mdx
+++ b/docs/docs/python-sdk/sdk_ref/infrahub_sdk/client.mdx
@@ -320,7 +320,7 @@ Retrieve nodes of a given kind based on provided filters.
 
 **Returns:**
 
-- list\[InfrahubNodeSync]: List of Nodes that match the given filters.
+- list\[InfrahubNode]: List of Nodes that match the given filters.
 
 </details>
 
diff --git a/infrahub_sdk/branch.py b/infrahub_sdk/branch.py
index 5f0eb8543..d62ef23df 100644
--- a/infrahub_sdk/branch.py
+++ b/infrahub_sdk/branch.py
@@ -323,7 +323,9 @@ def merge(self, branch_name: str) -> bool:
             }
         }
         query = Mutation(mutation="BranchMerge", input_data=input_data, query=MUTATION_QUERY_DATA)
-        response = self.client.execute_graphql(query=query.render(), tracker="mutation-branch-merge")
+        response = self.client.execute_graphql(
+            query=query.render(), tracker="mutation-branch-merge", timeout=max(120, self.client.default_timeout)
+        )
 
         return response["BranchMerge"]["ok"]
 
diff --git a/infrahub_sdk/client.py b/infrahub_sdk/client.py
index ac61abdc2..7c5c10bbd 100644
--- a/infrahub_sdk/client.py
+++ b/infrahub_sdk/client.py
@@ -1104,7 +1104,7 @@ async def filters(  # noqa: C901
             **kwargs (Any): Additional filter criteria for the query.
 
         Returns:
-            list[InfrahubNodeSync]: List of Nodes that match the given filters.
+            list[InfrahubNode]: List of Nodes that match the given filters.
 
         """
         branch = branch or self.default_branch
diff --git a/infrahub_sdk/node/node.py b/infrahub_sdk/node/node.py
index 9bdaa20cc..b23f6f865 100644
--- a/infrahub_sdk/node/node.py
+++ b/infrahub_sdk/node/node.py
@@ -1034,7 +1034,7 @@ async def artifact_fetch(self, name: str) -> str | dict[str, Any]:
             FeatureNotSupportedError: If this node does not inherit from ``CoreArtifactTarget``.
 
         """
-        self._validate_artifact_support(ARTIFACT_GENERATE_FEATURE_NOT_SUPPORTED_MESSAGE)
+        self._validate_artifact_support(ARTIFACT_FETCH_FEATURE_NOT_SUPPORTED_MESSAGE)
 
         artifact = await self._client.get(kind="CoreArtifact", name__value=name, object__ids=[self.id])
         return await self._client.object_store.get(identifier=artifact._get_attribute(name="storage_id").value)
@@ -2083,7 +2083,7 @@ def from_graphql(
 
         return cls(client=client, schema=schema, branch=branch, data=cls._strip_alias(data))
 
-    def _init_relationships(self, data: dict | None = None) -> None:
+    def _init_relationships(self, data: dict | RelatedNodeSync | None = None) -> None:
         for rel_schema in self._schema.relationships:
             rel_data = data.get(rel_schema.name, None) if isinstance(data, dict) else None
 
@@ -2820,8 +2820,10 @@ def create(
 
         mutation_query = self._generate_mutation_query()
 
+        # Upserting means we may want to create, meaning payload contains all mandatory fields required for a creation,
+        # so hfid is just redundant information. Currently, upsert mutation has performance overhead if `hfid` is filled.
         if allow_upsert:
-            input_data = self._generate_input_data(exclude_hfid=False, request_context=request_context)
+            input_data = self._generate_input_data(exclude_hfid=True, request_context=request_context)
             mutation_name = f"{self._schema.kind}Upsert"
             tracker = f"mutation-{str(self._schema.kind).lower()}-upsert"
         else:
@@ -2993,7 +2995,7 @@ def get_pool_allocated_resources(self, resource: InfrahubNodeSync) -> list[Infra
 
         """
         if not self.is_resource_pool():
-            raise ValueError("Allocate resources can only be fetched from resource pool nodes.")
+            raise ValueError("Allocated resources can only be fetched from resource pool nodes.")
 
         graphql_query_name = "InfrahubResourcePoolAllocated"
         node_ids_per_kind: dict[str, list[str]] = {}
@@ -3089,13 +3091,13 @@ def get_pool_resources_utilization(self) -> list[dict[str, Any]]:
             return [edge["node"] for edge in response[graphql_query_name]["edges"]]
         return []
 
-    def _get_relationship_many(self, name: str) -> RelationshipManager | RelationshipManagerSync:
+    def _get_relationship_many(self, name: str) -> RelationshipManagerSync:
         if name in self._relationship_cardinality_many_data:
             return self._relationship_cardinality_many_data[name]
 
         raise ResourceNotDefinedError(message=f"The node doesn't have a cardinality=many relationship for {name}")
 
-    def _get_relationship_one(self, name: str) -> RelatedNode | RelatedNodeSync:
+    def _get_relationship_one(self, name: str) -> RelatedNodeSync:
         if name in self._relationship_cardinality_one_data:
             return self._relationship_cardinality_one_data[name]
 
diff --git a/infrahub_sdk/schema/__init__.py b/infrahub_sdk/schema/__init__.py
index 82292e2a3..5343f24cd 100644
--- a/infrahub_sdk/schema/__init__.py
+++ b/infrahub_sdk/schema/__init__.py
@@ -408,7 +408,7 @@ async def check(self, schemas: list[dict], branch: str | None = None) -> tuple[b
 
     async def _get_kind_and_attribute_schema(
         self, kind: str | InfrahubNodeTypes, attribute: str, branch: str | None = None
-    ) -> tuple[str, AttributeSchema]:
+    ) -> tuple[str, AttributeSchemaAPI]:
         node_kind: str = kind._schema.kind if not isinstance(kind, str) else kind
         node_schema = await self.client.schema.get(kind=node_kind, branch=branch)
         schema_attr = node_schema.get_attribute(name=attribute)
diff --git a/tests/unit/sdk/test_branch.py b/tests/unit/sdk/test_branch.py
index 88f4a5305..a86182e9e 100644
--- a/tests/unit/sdk/test_branch.py
+++ b/tests/unit/sdk/test_branch.py
@@ -47,3 +47,27 @@ async def test_get_branches(clients: BothClients, mock_branches_list_query: HTTP
 
     assert len(branches) == 2
     assert isinstance(branches["main"], BranchData)
+
+
+@pytest.mark.parametrize("client_type", client_types)
+async def test_branch_merge_enforces_minimum_timeout(
+    httpx_mock: HTTPXMock, clients: BothClients, client_type: str
+) -> None:
+    """Both clients must apply the 120s minimum timeout floor when merging a branch.
+
+    The default client timeout is 60s, so a correct merge sends max(120, 60) == 120.
+    """
+    httpx_mock.add_response(
+        method="POST",
+        json={"data": {"BranchMerge": {"ok": True}}},
+        match_headers={"X-Infrahub-Tracker": "mutation-branch-merge"},
+    )
+
+    if client_type == "standard":
+        await clients.standard.branch.merge(branch_name="branch01")
+    else:
+        clients.sync.branch.merge(branch_name="branch01")
+
+    post_requests = [r for r in httpx_mock.get_requests() if r.method == "POST"]
+    assert len(post_requests) == 1
+    assert post_requests[0].extensions["timeout"]["read"] == 120
diff --git a/tests/unit/sdk/test_node.py b/tests/unit/sdk/test_node.py
index ab0d72ec0..0a30cb7e3 100644
--- a/tests/unit/sdk/test_node.py
+++ b/tests/unit/sdk/test_node.py
@@ -2,6 +2,7 @@
 
 import inspect
 import ipaddress
+import json
 import tempfile
 from io import BytesIO
 from pathlib import Path
@@ -177,6 +178,38 @@ async def test_node_hfid(client: InfrahubClient, schema_with_hfid: dict[str, Nod
     assert rack.hfid_str == "BuiltinRack__RACK1__JFK1"
 
 
+@pytest.mark.parametrize("client_type", client_types)
+async def test_node_create_upsert_excludes_hfid(
+    httpx_mock: HTTPXMock,
+    clients: BothClients,
+    schema_with_hfid: dict[str, NodeSchemaAPI],
+    client_type: str,
+) -> None:
+    """Upsert must never send the hfid in the mutation payload, for both async and sync clients.
+
+    Sending the hfid on an upsert adds server-side performance overhead, so create(allow_upsert=True)
+    excludes it. The async and sync clients must behave identically here.
+    """
+    httpx_mock.add_response(
+        method="POST",
+        json={"data": {"BuiltinLocationUpsert": {"ok": True, "object": {"id": "abcabc"}}}},
+        match_headers={"X-Infrahub-Tracker": "mutation-builtinlocation-upsert"},
+    )
+    location_data = {"name": {"value": "JFK1"}, "description": {"value": "JFK Airport"}, "type": {"value": "SITE"}}
+
+    if client_type == "standard":
+        location = InfrahubNode(client=clients.standard, schema=schema_with_hfid["location"], data=location_data)
+        await location.create(allow_upsert=True)
+    else:
+        location = InfrahubNodeSync(client=clients.sync, schema=schema_with_hfid["location"], data=location_data)
+        location.create(allow_upsert=True)
+
+    post_requests = [r for r in httpx_mock.get_requests() if r.method == "POST"]
+    assert len(post_requests) == 1
+    payload = json.loads(post_requests[0].content)
+    assert "hfid" not in payload["query"]
+
+
 @pytest.mark.parametrize("client_type", client_types)
 async def test_init_node_data_user(client: InfrahubClient, location_schema: NodeSchemaAPI, client_type: str) -> None:
     data = {