diff --git a/scripts/check_layer_imports.py b/scripts/check_layer_imports.py
index 59991561ffd..34a259d7256 100644
--- a/scripts/check_layer_imports.py
+++ b/scripts/check_layer_imports.py
@@ -1,6 +1,5 @@
 import argparse
 import ast
-import subprocess
 import sys
 from collections.abc import Callable, Iterable, Iterator, Sequence
 from dataclasses import dataclass
@@ -9,6 +8,8 @@ from pathlib import Path
 from types import MappingProxyType
 from typing import Final, Literal
 
+from lint_base_counts import REPO_GIT, Git, resolve_base_point
+
 PACKAGE_ROOT: Final = Path("litellm")
 ALLOWLIST: Final = Path("scripts/layer_imports_allowlist.txt")
 LEAF_MODULES: Final = frozenset(
@@ -172,11 +173,10 @@ def report(
     return new + stale + added
 
 
-def git_base_allowlist(ref: str) -> frozenset[str] | None:
-    shown: Final = subprocess.run(
-        ["git", "show", f"{ref}:{ALLOWLIST.as_posix()}"], capture_output=True, text=True, check=False
-    )
-    return parse_allowlist(shown.stdout) if shown.returncode == 0 else None
+def git_base_allowlist(ref: str, git: Git = REPO_GIT) -> frozenset[str] | None:
+    base_point: Final = resolve_base_point(ref, git)
+    tracked: Final = git(["ls-tree", "--name-only", base_point, "--", ALLOWLIST.as_posix()]).strip()
+    return parse_allowlist(git(["show", f"{base_point}:{ALLOWLIST.as_posix()}"])) if tracked else None
 
 
 class Arguments(argparse.Namespace):
@@ -189,7 +189,7 @@ def main(
 ) -> int:
     parser: Final = argparse.ArgumentParser(description="Check SDK/proxy layer import rules")
     parser.add_argument(
-        "--base", help="Also reject allowlist entries missing from the allowlist at this ref (CI passes the merge base)"
+        "--base", help="Also reject allowlist entries missing from the allowlist at the merge base with this ref"
     )
     args: Final = parser.parse_args(argv, namespace=Arguments())
     paths: Final = tuple(sorted(PACKAGE_ROOT.rglob("*.py")))
diff --git a/tests/unit/test_check_layer_imports.py b/tests/unit/test_check_layer_imports.py
index 7d84984c7c6..505ee53ced2 100644
--- a/tests/unit/test_check_layer_imports.py
+++ b/tests/unit/test_check_layer_imports.py
@@ -2,7 +2,7 @@ from pathlib import Path
 
 import pytest
 
-from scripts.check_layer_imports import main
+from scripts.check_layer_imports import git_base_allowlist, main
 
 
 def build_tree(root: Path, files: dict[str, str], allowlist: str = "") -> None:
@@ -194,3 +194,24 @@ def test_missing_base_allowlist_skips_growth_check(
     )
 
     assert run_check(tmp_path, monkeypatch, capsys, None) == (0, "")
+
+
+def test_base_allowlist_is_read_at_the_merge_base_not_the_branch_tip() -> None:
+    allowlist = "scripts/layer_imports_allowlist.txt"
+    outputs = {
+        ("merge-base", "origin/main", "HEAD"): "forkpoint\n",
+        ("ls-tree", "--name-only", "forkpoint", "--", allowlist): f"{allowlist}\n",
+        ("show", f"forkpoint:{allowlist}"): "L3 module litellm/types/foo.py litellm.router\n",
+        ("ls-tree", "--name-only", "origin/main", "--", allowlist): f"{allowlist}\n",
+        ("show", f"origin/main:{allowlist}"): "",
+    }
+
+    assert git_base_allowlist("origin/main", lambda args: outputs.get(tuple(args), "")) == frozenset(
+        {"L3 module litellm/types/foo.py litellm.router"}
+    )
+
+
+def test_base_without_an_allowlist_skips_the_growth_check() -> None:
+    outputs = {("merge-base", "origin/main", "HEAD"): "forkpoint\n"}
+
+    assert git_base_allowlist("origin/main", lambda args: outputs.get(tuple(args), "")) is None