tools/clang/scripts/update.py

diff --git a/tools/clang/scripts/update.py b/tools/clang/scripts/update.py
index 11466e8..12e332a4 100755
--- a/tools/clang/scripts/update.py
+++ b/tools/clang/scripts/update.py
@@ -35,11 +35,12 @@
 # https://chromium.googlesource.com/chromium/src/+/main/docs/updating_clang.md
 # Reverting problematic clang rolls is safe, though.
 # This is the output of `git describe` and is usable as a commit-ish.
-CLANG_REVISION = 'llvmorg-19-init-817-g3f5fcb59'
-CLANG_SUB_REVISION = 1
+CLANG_REVISION = 'llvmorg-18-init-17730-gf670112a'
+CLANG_SUB_REVISION = 2
 
 PACKAGE_VERSION = '%s-%s' % (CLANG_REVISION, CLANG_SUB_REVISION)
-RELEASE_VERSION = '19'
+RELEASE_VERSION = '18'
+# TODO(crbug.com/1517549): Bump to 19 in next Clang roll.
 
 CDS_URL = os.environ.get('CDS_CLANG_BUCKET_OVERRIDE',
     'https://commondatastorage.googleapis.com/chromium-browser-clang')
@@ -334,6 +335,11 @@
                       help='Verify that clang has the passed-in version.')
   args = parser.parse_args()
 
+  # TODO(crbug.com/1517549): Remove in next Clang roll.
+  if args.llvm_force_head_revision:
+    global RELEASE_VERSION
+    RELEASE_VERSION = '19'
+
   if args.verify_version and args.verify_version != RELEASE_VERSION:
     print('RELEASE_VERSION is %s but --verify-version argument was %s.' % (
         RELEASE_VERSION, args.verify_version))