diff --git a/build/fbcode_builder/getdeps/fetcher.py b/build/fbcode_builder/getdeps/fetcher.py
index 102e1bc65..b27d9b91c 100644
--- a/build/fbcode_builder/getdeps/fetcher.py
+++ b/build/fbcode_builder/getdeps/fetcher.py
@@ -646,9 +646,10 @@ class ShipitTransformerFetcher(Fetcher):
             fbcode_path = []
         return www_path + fbcode_path
 
-    def __init__(self, build_options, project_name) -> None:
+    def __init__(self, build_options, project_name, external_branch) -> None:
         self.build_options = build_options
         self.project_name = project_name
+        self.external_branch = external_branch
         self.repo_dir = os.path.join(build_options.scratch_dir, "shipit", project_name)
         self.shipit = None
         for path in ShipitTransformerFetcher._shipit_paths(build_options):
@@ -679,24 +680,27 @@ class ShipitTransformerFetcher(Fetcher):
             if os.path.exists(tmp_path):
                 shutil.rmtree(tmp_path)
             os.makedirs(os.path.dirname(tmp_path), exist_ok=True)
+            cmd = [
+                self.shipit,
+                "shipit",
+                "--project=" + self.project_name,
+                "--create-new-repo",
+                "--source-repo-dir=" + self.build_options.fbsource_dir,
+                "--source-branch=.",
+                "--skip-source-init",
+                "--skip-source-pull",
+                "--skip-source-clean",
+                "--skip-push",
+                "--destination-use-anonymous-https",
+                "--create-new-repo-output-path=" + tmp_path,
+            ]
+            if self.external_branch:
+                cmd += [
+                    f"--external-branch={self.external_branch}",
+                ]
 
             # Run shipit
-            run_cmd(
-                [
-                    self.shipit,
-                    "shipit",
-                    "--project=" + self.project_name,
-                    "--create-new-repo",
-                    "--source-repo-dir=" + self.build_options.fbsource_dir,
-                    "--source-branch=.",
-                    "--skip-source-init",
-                    "--skip-source-pull",
-                    "--skip-source-clean",
-                    "--skip-push",
-                    "--destination-use-anonymous-https",
-                    "--create-new-repo-output-path=" + tmp_path,
-                ]
-            )
+            run_cmd(cmd)
 
             # Remove the .git directory from the repository it generated.
             # There is no need to commit this.
diff --git a/build/fbcode_builder/getdeps/manifest.py b/build/fbcode_builder/getdeps/manifest.py
index 5cec33aab..b1b25cd37 100644
--- a/build/fbcode_builder/getdeps/manifest.py
+++ b/build/fbcode_builder/getdeps/manifest.py
@@ -49,6 +49,7 @@ SCHEMA = {
             "shipit_project": OPTIONAL,
             "shipit_fbcode_builder": OPTIONAL,
             "use_shipit": OPTIONAL,
+            "shipit_external_branch": OPTIONAL,
         },
     },
     "dependencies": {"optional_section": True, "allow_values": False},
@@ -428,7 +429,11 @@ class ManifestParser(object):
             and real_shipit_available
         ):
             # We can use the code from fbsource
-            return ShipitTransformerFetcher(build_options, self.shipit_project)
+            return ShipitTransformerFetcher(
+                build_options,
+                self.shipit_project,
+                self.get("manifest", "shipit_external_branch"),
+            )
 
         # If both of these are None, the package can only be coming from
         # preinstalled toolchain or system packages
diff --git a/build/fbcode_builder/manifests/meta-python-3.12 b/build/fbcode_builder/manifests/meta-python-3.12
new file mode 100644
index 000000000..a216c036f
--- /dev/null
+++ b/build/fbcode_builder/manifests/meta-python-3.12
@@ -0,0 +1,17 @@
+# This is primarily to support CinderX, so it's not heavily configured.
+
+[manifest]
+name = meta-python-3.12
+fbsource_path = third-party/python/3.12
+shipit_project = facebookincubator/cinder
+shipit_fbcode_builder = false
+shipit_external_branch = meta/3.12
+
+[git]
+repo_url = https://github.com/facebookincubator/cinder.git#meta/3.12
+
+[build]
+builder = autoconf
+
+[shipit.pathmap]
+third-party/python/3.12 = .