diff --git a/.github/workflows/self-test.yml b/.github/workflows/self-test.yml
index 5de9655..f8c1078 100644
--- a/.github/workflows/self-test.yml
+++ b/.github/workflows/self-test.yml
@@ -31,7 +31,7 @@ jobs:
     strategy:
       matrix:
         os: [ ubuntu-latest, macos-latest, windows-latest ]
-        clang-version: ['8','9','10', '11', '12', '13', '14', '15', '16', '17', '18', '19', '20']
+        clang-version: ['9', '10', '11', '12', '13', '14', '15', '16', '17', '18', '19', '20', '21']
       fail-fast: false
     runs-on: ${{ matrix.os }}
     steps:
diff --git a/action.yml b/action.yml
index 667223d..8794465 100644
--- a/action.yml
+++ b/action.yml
@@ -39,12 +39,12 @@ inputs:
   version:
     description: |
       The desired version of the [clang-tools](https://github.com/cpp-linter/clang-tools-pip) to use.
-      Accepted options are strings which can be 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, or 8.
+      Accepted options are strings which can be 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10 or 9.
 
       - Set this option to a blank string (`''`) to use the platform's default installed version.
       - This value can also be a path to where the clang tools are installed (if using a custom install location).
     required: false
-    default: 16
+    default: 18
   verbosity:
     description: |
       This controls the action's verbosity in the workflow's logs.
@@ -323,6 +323,7 @@ runs:
       if: runner.os == 'macOS'
       shell: nu {0}
       run: |-
+        ^brew update
         let brew_install_arg = 'llvm@${{ inputs.version }}'
         let result = (^brew install $brew_install_arg) | complete
         print $result
diff --git a/pyproject.toml b/pyproject.toml
index efcf4c8..a325f4d 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -6,7 +6,7 @@ dependencies = []
 
 [dependency-groups]
 action = [
-    "clang-tools==0.15.2",
+    "clang-tools==0.15.3",
     "cpp-linter==1.10.7",
 ]
 dev = [
diff --git a/uv.lock b/uv.lock
index 3bd1d3e..56691bf 100644
--- a/uv.lock
+++ b/uv.lock
@@ -202,10 +202,10 @@ wheels = [
 
 [[package]]
 name = "clang-tools"
-version = "0.15.2"
+version = "0.15.3"
 source = { registry = "https://pypi.org/simple" }
 wheels = [
-    { url = "https://files.pythonhosted.org/packages/e9/fd/e35a00d0bbb31a7d9933927b0246a871c0737200d9864c1c11102eb11a17/clang_tools-0.15.2-py3-none-any.whl", hash = "sha256:d6299d8b0564e89b01caaab0bcb58d56b989712657fc2aad6fa36c4e47e0fdbc", size = 11013, upload-time = "2025-08-15T22:44:54.695Z" },
+    { url = "https://files.pythonhosted.org/packages/e9/dc/2a67ca33fafbd50f7b33be4c0221cc9e3f2fb08f04554cdc03c76c6acd1b/clang_tools-0.15.3-py3-none-any.whl", hash = "sha256:9164007e5c503b6044f759916711d5eb50bac9499c0f0378dd139f5ed023a5b4", size = 11060, upload-time = "2025-08-31T18:08:56.623Z" },
 ]
 
 [[package]]
@@ -289,7 +289,7 @@ docs = [
 
 [package.metadata.requires-dev]
 action = [
-    { name = "clang-tools", specifier = "==0.15.2" },
+    { name = "clang-tools", specifier = "==0.15.3" },
     { name = "cpp-linter", specifier = "==1.10.7" },
 ]
 dev = [