diff --git a/.github/workflows/docs.yml b/.github/workflows/docs.yml
index 2833fe98ff..8d3c3e10e2 100644
--- a/.github/workflows/docs.yml
+++ b/.github/workflows/docs.yml
@@ -1,7 +1,7 @@
 on:
   pull_request:
     branches:
-      - main
+      - v1
 name: docs
 jobs:
   docs:
diff --git a/.github/workflows/lint.yml b/.github/workflows/lint.yml
index 1051da0bdd..54a39a225a 100644
--- a/.github/workflows/lint.yml
+++ b/.github/workflows/lint.yml
@@ -1,7 +1,7 @@
 on:
   pull_request:
     branches:
-      - main
+      - v1
 name: lint
 jobs:
   lint:
diff --git a/.github/workflows/mypy.yml b/.github/workflows/mypy.yml
index e6a79291d0..4a88a14efa 100644
--- a/.github/workflows/mypy.yml
+++ b/.github/workflows/mypy.yml
@@ -1,7 +1,7 @@
 on:
   pull_request:
     branches:
-      - main
+      - v1
 name: mypy
 jobs:
   mypy:
diff --git a/.github/workflows/unittest.yml b/.github/workflows/unittest.yml
index a7805de447..cfd40c733d 100644
--- a/.github/workflows/unittest.yml
+++ b/.github/workflows/unittest.yml
@@ -1,7 +1,7 @@
 on:
   pull_request:
     branches:
-      - main
+      - v1
 name: unittest
 jobs:
   unit:
diff --git a/bigframes/functions/_function_session.py b/bigframes/functions/_function_session.py
index b0d3ab81eb..ac15199d81 100644
--- a/bigframes/functions/_function_session.py
+++ b/bigframes/functions/_function_session.py
@@ -740,9 +740,12 @@ def udf(
         BigQuery managed function.
 
         .. note::
-            The udf must be self-contained, i.e. it must not contain any
+            This feature is in preview. The code in the udf must be
+            (1) self-contained, i.e. it must not contain any
             references to an import or variable defined outside the function
-            body.
+            body, and
+            (2) Python 3.11 compatible, as that is the environment
+            in which the code is executed in the cloud.
 
         .. note::
             Please have following IAM roles enabled for you:
@@ -794,7 +797,7 @@ def udf(
                 https://pip.pypa.io/en/stable/reference/requirements-file-format/.
         """
 
-        warnings.warn("udf is in preview.", category=bfe.PreviewWarning)
+        warnings.warn("udf is in preview.", category=bfe.PreviewWarning, stacklevel=6)
 
         # Some defaults may be used from the session if not provided otherwise.
         session = self._resolve_session(session)
diff --git a/bigframes/session/__init__.py b/bigframes/session/__init__.py
index 72129d594e..a7ec1d4267 100644
--- a/bigframes/session/__init__.py
+++ b/bigframes/session/__init__.py
@@ -1432,9 +1432,12 @@ def udf(
         BigQuery managed function.
 
         .. note::
-            The udf must be self-contained, i.e. it must not contain any
+            This feature is in preview. The code in the udf must be
+            (1) self-contained, i.e. it must not contain any
             references to an import or variable defined outside the function
-            body.
+            body, and
+            (2) Python 3.11 compatible, as that is the environment
+            in which the code is executed in the cloud.
 
         .. note::
             Please have following IAM roles enabled for you: