fix(interpreter): treat invalid glob bracket expressions as literals

crates/bashkit/src/interpreter/glob.rs

@@ -244,6 +244,9 @@ impl Interpreter {
                     }
                 }
                 (Some('['), Some(v)) => {
+                    // Save state before consuming '[' — if bracket expr is
+                    // invalid (e.g. "[]"), we fall back to literal '[' match.
+                    let saved_pattern = pattern_chars.clone();
                     pattern_chars.next(); // consume '['
                     let match_char = if nocase { v.to_ascii_lowercase() } else { v };
                     if let Some(matched) =
@@ -255,8 +258,20 @@ impl Interpreter {
                             return false;
                         }
                     } else {
-                        // Invalid bracket expression, treat '[' as literal
-                        return false;
+                        // Invalid bracket expression — treat '[' as literal
+                        pattern_chars = saved_pattern;
+                        pattern_chars.next(); // consume '[' as literal
+                        let p = '[';
+                        let match_ok = if nocase {
+                            p.eq_ignore_ascii_case(&v)
+                        } else {
+                            p == v
+                        };
+                        if match_ok {
+                            value_chars.next();
+                        } else {
+                            return false;
+                        }
                     }
                 }
                 (Some('['), None) => return false,

crates/bashkit/tests/spec_cases/bash/conditional.test.sh

@@ -181,3 +181,26 @@ correct
 ### expect
 yes
 ### end
+
+### cond_bracket_literal_match
+# Issue #837: [] should be treated as literal when it's an invalid glob
+x="[]"
+if [[ "$x" == "[]" ]]; then echo match; else echo "no match"; fi
+### expect
+match
+### end
+
+### cond_single_bracket_literal
+# Literal [ comparison
+x="["
+[[ "$x" == "[" ]] && echo match || echo "no match"
+### expect
+match
+### end
+
+### cond_valid_glob_bracket
+# Valid glob [a] should still work as pattern
+[[ "a" == [a] ]] && echo match || echo "no match"
+### expect
+match
+### end