fix: quote TOON array elements containing semicolons

oq/format.go

@@ -350,12 +350,24 @@ func toonValue(v expr.Value) string {
 	case expr.KindBool:
 		return strconv.FormatBool(v.Bool)
 	case expr.KindArray:
-		return toonEscape(strings.Join(v.Arr, ";"))
+		return toonArrayValue(v.Arr)
 	default:
 		return "null"
 	}
 }
 
+func toonArrayValue(values []string) string {
+	parts := make([]string, len(values))
+	for i, value := range values {
+		if strings.Contains(value, ";") {
+			parts[i] = toonQuote(value)
+			continue
+		}
+		parts[i] = toonEscape(value)
+	}
+	return strings.Join(parts, ";")
+}
+
 // toonEscape quotes a string if it needs escaping for TOON format.
 // A string must be quoted if it: is empty, contains comma/colon/quote/backslash/
 // brackets/braces/control chars, has leading/trailing whitespace, or matches
@@ -387,7 +399,10 @@ func toonEscape(s string) string {
 	if !needsQuote {
 		return s
 	}
-	// Quote with escaping
+	return toonQuote(s)
+}
+
+func toonQuote(s string) string {
 	var sb strings.Builder
 	sb.WriteByte('"')
 	for _, ch := range s {

oq/format_test.go

@@ -0,0 +1,18 @@
+package oq
+
+import (
+	"testing"
+
+	"github.com/speakeasy-api/openapi/oq/expr"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestToonValue_ArrayEscapesSemicolonElements(t *testing.T) {
+	t.Parallel()
+
+	value := expr.ArrayVal([]string{"v1;deprecated", "v2;current"})
+
+	encoded := toonValue(value)
+
+	assert.Equal(t, `"v1;deprecated";"v2;current"`, encoded, "array elements containing the delimiter should be quoted individually")
+}