diff --git a/pkg/parser/frontmatter_helpers_test.go b/pkg/parser/frontmatter_helpers_test.go
index f886a4d87a8..e7288029c59 100644
--- a/pkg/parser/frontmatter_helpers_test.go
+++ b/pkg/parser/frontmatter_helpers_test.go
@@ -148,6 +148,28 @@ engine: claude
 	}
 }
 
+func TestUpdateWorkflowFrontmatterQuotesCronExpressions(t *testing.T) {
+	workflowPath := filepath.Join(testutil.TempDir(t, "test-*"), "scheduled-workflow.md")
+	initialContent := `---
+on:
+  schedule:
+    - cron: "0 14 * * 1-5"
+---
+# Scheduled Workflow`
+	require.NoError(t, os.WriteFile(workflowPath, []byte(initialContent), 0644))
+
+	err := UpdateWorkflowFrontmatter(workflowPath, func(frontmatter map[string]any) error {
+		frontmatter["engine"] = "copilot"
+		return nil
+	}, false)
+	require.NoError(t, err)
+
+	updatedContent, err := os.ReadFile(workflowPath)
+	require.NoError(t, err)
+	assert.Contains(t, string(updatedContent), `cron: "0 14 * * 1-5"`)
+	assert.Contains(t, string(updatedContent), "engine: copilot")
+}
+
 func TestUpdateWorkflowFrontmatterErrorIncludesWorkflowPath(t *testing.T) {
 	tempDir := testutil.TempDir(t, "test-*")
 
diff --git a/pkg/parser/workflow_update.go b/pkg/parser/workflow_update.go
index a527475ce19..735225f5303 100644
--- a/pkg/parser/workflow_update.go
+++ b/pkg/parser/workflow_update.go
@@ -48,6 +48,7 @@ func UpdateWorkflowFrontmatter(workflowPath string, updateFunc func(frontmatter
 	if err != nil {
 		return fmt.Errorf("could not marshal updated frontmatter for %q; ensure updated values are YAML-serializable, then retry: %w", workflowPath, err)
 	}
+	updatedFrontmatter = []byte(QuoteCronExpressions(string(updatedFrontmatter)))
 
 	// Reconstruct the file content
 	updatedContent, err := ReconstructWorkflowFile(string(updatedFrontmatter), result.Markdown)