diff --git a/.github/workflows/cjs.yml b/.github/workflows/cjs.yml
index e7a05561711..6d23498f3b4 100644
--- a/.github/workflows/cjs.yml
+++ b/.github/workflows/cjs.yml
@@ -50,6 +50,9 @@ jobs:
       - name: Install npm dependencies
         run: cd actions/setup/js && npm ci
 
+      - name: Check runtime CJS syntax
+        run: make check-cjs-syntax
+
       - name: Run typecheck
         run: cd actions/setup/js && npm run typecheck
 
diff --git a/Makefile b/Makefile
index a246b46d3d6..6c772f401a9 100644
--- a/Makefile
+++ b/Makefile
@@ -231,6 +231,14 @@ security-govulncheck-sarif:
 	@echo "✓ Govulncheck complete (results in govulncheck-results.sarif)"
 
 # Test JavaScript files
+.PHONY: check-cjs-syntax
+check-cjs-syntax:
+	@echo "→ Checking CommonJS runtime syntax..."
+	@find actions/setup/js \
+		-path 'actions/setup/js/node_modules' -prune -o \
+		-type f -name '*.cjs' ! -name '*.test.cjs' -print0 | xargs -0 -r -n1 node --check
+	@echo "✓ CommonJS runtime syntax validated"
+
 .PHONY: test-js
 test-js: build-js
 	cd actions/setup/js && npm run test:js -- --no-file-parallelism