diff --git a/.github/workflows/lint.yml b/.github/workflows/lint.yml
index a96edf0..1d53a79 100644
--- a/.github/workflows/lint.yml
+++ b/.github/workflows/lint.yml
@@ -26,6 +26,8 @@ jobs:
         run: |
           python -m pip install --upgrade pip
           python -m pip install uv
+          sudo apt-get install npm
+          npm install --global prettier
       - name: Setup
         run: |
           uv venv
@@ -33,6 +35,9 @@ jobs:
       - name: Check formatting with black
         run: |
           uv tool run black --check .
+      - name: Check formatting with prettier
+        run: |
+          prettier . --check
       - name: Run flake8
         run: |
           uv tool run flake8 src/ --ignore=E203,W503,E722,E731 --max-complexity=100 --max-line-length=160
diff --git a/.github/workflows/update-syntax-description.yml b/.github/workflows/update-syntax-description.yml
index 3156c5d..07b6817 100644
--- a/.github/workflows/update-syntax-description.yml
+++ b/.github/workflows/update-syntax-description.yml
@@ -31,6 +31,8 @@ jobs:
         run: |
           python -m pip install --upgrade pip
           python -m pip install cf-remote
+          sudo apt-get install npm
+          npm install --global prettier
       - name: Install cfengine
         run: |
           cf-remote --version master download --edition community ubuntu24 amd64 hub
@@ -41,7 +43,7 @@ jobs:
           (
             sudo cf-promises --syntax-description json
           ) > new.json
-          echo "" >> new.json
+          prettier new.json --write
       - name: Set Git user
         run: |
           git config user.name 'github-actions[bot]'
diff --git a/src/cfengine_cli/syntax-description.json b/src/cfengine_cli/syntax-description.json
index 3fbbc16..b743e3c 100644
--- a/src/cfengine_cli/syntax-description.json
+++ b/src/cfengine_cli/syntax-description.json
@@ -3258,13 +3258,7 @@
       "status": "normal"
     },
     "common": {
-      "promiseTypes": [
-        "classes",
-        "defaults",
-        "meta",
-        "reports",
-        "vars"
-      ],
+      "promiseTypes": ["classes", "defaults", "meta", "reports", "vars"],
       "status": "normal"
     },
     "edit_line": {
diff --git a/tests/shell/004-format-check.sh b/tests/shell/004-format-check.sh
new file mode 100755
index 0000000..f05acc4
--- /dev/null
+++ b/tests/shell/004-format-check.sh
@@ -0,0 +1,41 @@
+#!/bin/bash
+
+set -e
+set -x
+
+# Setup: create a temp directory for test files
+tmpdir=$(mktemp -d)
+trap "rm -rf $tmpdir" EXIT
+
+write_formatted() {
+	printf 'bundle agent main\n{\n  vars:\n    "v" string => "hello";\n}\n' > "$1"
+}
+
+write_unformatted() {
+	printf 'bundle agent main { vars: "v" string => "hello"; }\n' > "$1"
+}
+
+# Case 1: format without --check on already-formatted file -> exit 0
+write_formatted "$tmpdir/good.cf"
+cfengine format "$tmpdir/good.cf"
+
+# Case 2: format without --check on unformatted file -> exit 0 (reformats it)
+write_unformatted "$tmpdir/bad.cf"
+cfengine format "$tmpdir/bad.cf"
+# Verify it was actually reformatted to the correct output
+write_formatted "$tmpdir/expected.cf"
+diff "$tmpdir/expected.cf" "$tmpdir/bad.cf"
+
+# Case 3: --check on already-formatted file -> exit 0
+write_formatted "$tmpdir/good2.cf"
+cfengine format --check "$tmpdir/good2.cf"
+
+# Case 4: --check on unformatted file -> exit 1
+write_unformatted "$tmpdir/bad2.cf"
+cp "$tmpdir/bad2.cf" "$tmpdir/bad2_orig.cf"
+if cfengine format --check "$tmpdir/bad2.cf"; then
+	echo "FAIL: expected exit code 1 for --check on unformatted file"
+	exit 1
+fi
+# Verify the file was NOT modified
+diff "$tmpdir/bad2_orig.cf" "$tmpdir/bad2.cf"