diff --git a/Cargo.lock b/Cargo.lock
index d5e90e41c..25ae8f30d 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -2066,9 +2066,9 @@ checksum = "19f132c84eca552bf34cab8ec81f1c1dcc229b811638f9d283dceabe58c5569e"
 
 [[package]]
 name = "pklr"
-version = "0.4.1"
+version = "0.4.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "7010962140d2369f8d1d287fa9b8862d4ca9d104621dcf614777efa33fccc545"
+checksum = "46a2a30479b1648d912e1d85b939ccab3813b8fcdd4c3f805f3fb8f2efa95215"
 dependencies = [
  "async-recursion",
  "indexmap 2.14.0",
diff --git a/Cargo.toml b/Cargo.toml
index 55b0350cd..8786dab6b 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -49,7 +49,7 @@ itertools          = "0.14"
 libc               = "0.2"
 log                = "0.4"
 once_cell          = "1"
-pklr               = "0.4.1"
+pklr               = "0.4.2"
 regex              = "1"
 semver             = "1"
 serde              = { version = "1", features = ["derive"] }
diff --git a/scripts/gen_builtins.py b/scripts/gen_builtins.py
index cd7b39ddf..63b92b23e 100644
--- a/scripts/gen_builtins.py
+++ b/scripts/gen_builtins.py
@@ -40,15 +40,48 @@ class meta extends Annotation {
 """
 
 
+# Deprecated aliases. These point at a canonical builtin so loading
+# Builtins.pkl never reads a deprecated property — under pklr's lazy
+# @Deprecated handling (>= 0.4.2) the warning then fires only when a
+# user references e.g. `Builtins.check_byte_order_marker`.
+# (alias_name, canonical_name, since, message)
+DEPRECATED_ALIASES = [
+    (
+        "check_byte_order_marker",
+        "byte_order_marker",
+        "1.30.0",
+        "Use `Builtins.byte_order_marker`",
+    ),
+    (
+        "fix_byte_order_marker",
+        "byte_order_marker",
+        "1.30.0",
+        "Use `Builtins.byte_order_marker`",
+    ),
+]
+
+
 def main():
+    skip = {alias for alias, _, _, _ in DEPRECATED_ALIASES}
+
     # Generate pkl/Builtins.pkl
     with open("pkl/Builtins.pkl", "w", newline="\n") as f:
         f.write(HEADER)
         for filepath in sorted(glob.glob("pkl/builtins/*.pkl")):
             filename = os.path.splitext(os.path.basename(filepath))[0]
             identifier = filename.replace("-", "_")
+            if identifier in skip:
+                continue
             f.write(f'{identifier} = Builtins["builtins/{filename}.pkl"].{identifier}\n')
 
+        for alias, canonical, since, message in DEPRECATED_ALIASES:
+            f.write("\n")
+            f.write("@Deprecated {\n")
+            f.write(f'  since = "{since}"\n')
+            f.write(f'  message = "{message}"\n')
+            f.write("}\n")
+            f.write(f'{alias} = Builtins["builtins/{canonical}.pkl"].{canonical}\n')
+
     # pkl format (exits 11 after formatting, ignore that)
     subprocess.run(["pkl", "format", "--write", "pkl/Builtins.pkl"])
 
diff --git a/src/cli/migrate/pre_commit.rs b/src/cli/migrate/pre_commit.rs
index d75516bbf..7c104d852 100644
--- a/src/cli/migrate/pre_commit.rs
+++ b/src/cli/migrate/pre_commit.rs
@@ -1165,13 +1165,13 @@ impl PreCommit {
             "check_executables_have_shebangs",
         );
         map.insert("check-symlinks", "check_symlinks");
-        map.insert("check-byte-order-marker", "check_byte_order_marker");
+        map.insert("check-byte-order-marker", "byte_order_marker");
         map.insert("check-added-large-files", "check_added_large_files");
         map.insert("check-ast", "python_check_ast");
         map.insert("debug-statements", "python_debug_statements");
         map.insert("detect-private-key", "detect_private_key");
         map.insert("no-commit-to-branch", "no_commit_to_branch");
-        map.insert("fix-byte-order-marker", "fix_byte_order_marker");
+        map.insert("fix-byte-order-marker", "byte_order_marker");
 
         map
     }