From a120958b0601412df7cf1becb9f457e2ce96d51f Mon Sep 17 00:00:00 2001
From: kanywst <niwatakuma@icloud.com>
Date: Thu, 18 Jun 2026 01:39:45 +0900
Subject: [PATCH] fix(lexer): prevent panic on unterminated string literal

---
 pkg/dsl/lexer/lexer.go      |  8 +++++++-
 pkg/dsl/lexer/lexer_test.go | 13 +++++++++++++
 2 files changed, 20 insertions(+), 1 deletion(-)

diff --git a/pkg/dsl/lexer/lexer.go b/pkg/dsl/lexer/lexer.go
index 5a8b38fe4..eb4e0de5b 100644
--- a/pkg/dsl/lexer/lexer.go
+++ b/pkg/dsl/lexer/lexer.go
@@ -228,7 +228,13 @@ func (l *Lexer) lexString() string {
 		}
 		l.readChar()
 	}
-	str += l.input[position:l.position]
+	end := l.position
+	if end > len(l.input) {
+		end = len(l.input)
+	}
+	if position < end {
+		str += l.input[position:end]
+	}
 	if l.ch == '"' {
 		l.readChar()
 	}
diff --git a/pkg/dsl/lexer/lexer_test.go b/pkg/dsl/lexer/lexer_test.go
index 969054738..1ee6f7ef2 100644
--- a/pkg/dsl/lexer/lexer_test.go
+++ b/pkg/dsl/lexer/lexer_test.go
@@ -1189,4 +1189,17 @@ rule test_rule(created_at time, started_at time) {
 		Expect(hasBoolean).Should(BeTrue())
 		Expect(hasComparison).Should(BeTrue())
 	})
+
+	It("Case 4 - should not panic on an unterminated string", func() {
+		for _, input := range []string{`"\`, `"`, `"abc\`, `"\\`} {
+			Expect(func() {
+				l := NewLexer(input)
+				for {
+					if l.NextToken().Type == token.EOF {
+						break
+					}
+				}
+			}).ShouldNot(Panic())
+		}
+	})
 })