diff --git a/pyjsclear/__init__.py b/pyjsclear/__init__.py
index 52fa0af..ee5c57b 100644
--- a/pyjsclear/__init__.py
+++ b/pyjsclear/__init__.py
@@ -12,7 +12,7 @@
 
 __all__ = ['Deobfuscator', 'deobfuscate', 'deobfuscate_file']
 
-__version__ = '0.1.5'
+__version__ = '0.1.6'
 
 
 def deobfuscate(code: str, max_iterations: int = 50) -> str:
diff --git a/pyjsclear/generator.py b/pyjsclear/generator.py
index 8712c6f..d3cfcfb 100644
--- a/pyjsclear/generator.py
+++ b/pyjsclear/generator.py
@@ -298,6 +298,18 @@ def _gen_expr_stmt(node: dict, indent: int) -> str:
     return generate(node['expression'], indent)
 
 
+def _mixes_nullish_and_logical(operator: str, operand: dict | None) -> bool:
+    # ES forbids ?? adjacent to || or && without parens.
+    if not isinstance(operand, dict) or operand.get('type') != 'LogicalExpression':
+        return False
+    operand_operator = operand.get('operator', '')
+    if operator == '??':
+        return operand_operator in ('||', '&&')
+    if operator in ('||', '&&'):
+        return operand_operator == '??'
+    return False
+
+
 def _gen_binary(node: dict, indent: int) -> str:
     operator = node.get('operator', '')
     left = generate(node['left'], indent)
@@ -305,9 +317,13 @@ def _gen_binary(node: dict, indent: int) -> str:
     my_prec = _PRECEDENCE.get(operator, 1)
     left_prec = _expr_precedence(node['left'])
     right_prec = _expr_precedence(node['right'])
-    if left_prec < my_prec:
+    if left_prec < my_prec or _mixes_nullish_and_logical(operator, node['left']):
         left = f'({left})'
-    if right_prec < my_prec or (right_prec == my_prec and operator not in ('+', '*', '|', '&', '^')):
+    if (
+        right_prec < my_prec
+        or (right_prec == my_prec and operator not in ('+', '*', '|', '&', '^'))
+        or _mixes_nullish_and_logical(operator, node['right'])
+    ):
         right = f'({right})'
     return f'{left} {operator} {right}'
 
@@ -385,6 +401,11 @@ def _gen_call(node: dict, indent: int) -> str:
     return f'{callee}({argument_string})'
 
 
+def _gen_chain(node: dict, indent: int) -> str:
+    # ChainExpression wraps an optional chain; the ?. is on the inner node.
+    return generate(node.get('expression'), indent)
+
+
 def _gen_new(node: dict, indent: int) -> str:
     callee = generate(node['callee'], indent)
     arguments = node.get('arguments', [])
@@ -700,7 +721,7 @@ def _expr_precedence(node: dict) -> int:
             | 'TemplateLiteral'
         ):
             return 20
-        case 'MemberExpression' | 'CallExpression' | 'NewExpression' | 'TaggedTemplateExpression':
+        case 'MemberExpression' | 'CallExpression' | 'NewExpression' | 'TaggedTemplateExpression' | 'ChainExpression':
             return 19
         case 'UpdateExpression':
             return 17 if node.get('prefix') else 18
@@ -749,6 +770,7 @@ def _expr_precedence(node: dict) -> int:
     'AssignmentExpression': _gen_assignment,
     'MemberExpression': _gen_member,
     'CallExpression': _gen_call,
+    'ChainExpression': _gen_chain,
     'NewExpression': _gen_new,
     'ConditionalExpression': _gen_conditional,
     'SequenceExpression': _gen_sequence,
diff --git a/pyjsclear/transforms/base.py b/pyjsclear/transforms/base.py
index 9dbd46c..02fc1e8 100644
--- a/pyjsclear/transforms/base.py
+++ b/pyjsclear/transforms/base.py
@@ -52,9 +52,21 @@ def get_parent_map(self) -> dict[int, tuple[dict, str, int | None]]:
         return self._parent_map
 
     def invalidate_parent_map(self) -> None:
-        """Invalidate the cached parent map after AST modifications."""
+        """Drop the cached parent map so the next lookup rebuilds it.
+
+        Prefer record_replacement() for in-place swaps — O(1) vs this O(N) rebuild (quadratic over many).
+        """
         self._parent_map = None
 
+    def record_replacement(self, replacement: dict, parent: dict, key: str, index: int | None) -> None:
+        """Patch the cached parent map after an in-place node swap.
+
+        Only for index-preserving swaps; use invalidate_parent_map() for insert/remove. The old subtree's
+        entries and the replacement's descendants stay unregistered (find_parent returns None until a rebuild).
+        """
+        if self._parent_map is not None:
+            self._parent_map[id(replacement)] = (parent, key, index)
+
     def find_parent(self, target_node: dict) -> tuple[dict, str, int | None] | None:
         """Find the parent of a node using the parent map."""
         parent_map = self.get_parent_map()
diff --git a/pyjsclear/transforms/class_static_resolver.py b/pyjsclear/transforms/class_static_resolver.py
index d90c4ef..8f505f6 100644
--- a/pyjsclear/transforms/class_static_resolver.py
+++ b/pyjsclear/transforms/class_static_resolver.py
@@ -227,3 +227,4 @@ def _replace_in_parent(
             parent[key][index] = replacement
         else:
             parent[key] = replacement
+        self.record_replacement(replacement, parent, key, index)
diff --git a/pyjsclear/transforms/object_simplifier.py b/pyjsclear/transforms/object_simplifier.py
index 1049ff6..bd4561c 100644
--- a/pyjsclear/transforms/object_simplifier.py
+++ b/pyjsclear/transforms/object_simplifier.py
@@ -180,7 +180,7 @@ def _replace_node(self, target: dict, replacement: dict) -> bool:
             parent[key][index] = replacement
         else:
             parent[key] = replacement
-        self.invalidate_parent_map()
+        self.record_replacement(replacement, parent, key, index)
         return True
 
     def _inline_function(self, function_node: dict, arguments: list[dict]) -> dict | None:
diff --git a/pyjsclear/transforms/string_revealer.py b/pyjsclear/transforms/string_revealer.py
index 5433f4c..c354fa7 100644
--- a/pyjsclear/transforms/string_revealer.py
+++ b/pyjsclear/transforms/string_revealer.py
@@ -1297,7 +1297,7 @@ def _replace_node_in_ast(self, target: dict, replacement: dict) -> None:
                 parent[key][index] = replacement
             else:
                 parent[key] = replacement
-            self.invalidate_parent_map()
+            self.record_replacement(replacement, parent, key, index)
 
     # ================================================================
     # Strategy 3: Simple static array unpacking
diff --git a/pyjsclear/utils/ast_helpers.py b/pyjsclear/utils/ast_helpers.py
index 1b29009..23e01de 100644
--- a/pyjsclear/utils/ast_helpers.py
+++ b/pyjsclear/utils/ast_helpers.py
@@ -171,6 +171,7 @@ def is_valid_identifier(name: Any) -> bool:
     'AssignmentExpression': ('left', 'right'),
     'MemberExpression': ('object', 'property'),
     'CallExpression': ('callee', 'arguments'),
+    'ChainExpression': ('expression',),
     'NewExpression': ('callee', 'arguments'),
     'ConditionalExpression': ('test', 'consequent', 'alternate'),
     'SequenceExpression': ('expressions',),
diff --git a/pyproject.toml b/pyproject.toml
index 6c25ca8..68966fb 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -9,7 +9,7 @@ description = "Pure Python JavaScript deobfuscator"
 readme = "README.md"
 license = "Apache-2.0"
 requires-python = ">=3.11"
-dependencies = ["esprima2>=5.0.1"]
+dependencies = ["esprima2==6.0.0"]
 keywords = ["javascript", "deobfuscator", "deobfuscation", "security", "malware-analysis", "ast"]
 authors = [
     {name = "Intezer Labs", email = "info@intezer.com"},
diff --git a/requirements.txt b/requirements.txt
index 843a8fa..aa62669 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1 +1 @@
-esprima2>=5.0.0
+esprima2==6.0.0
diff --git a/tests/resources/sample.deobfuscated.js b/tests/resources/sample.deobfuscated.js
index 8a900d0..95064ea 100644
--- a/tests/resources/sample.deobfuscated.js
+++ b/tests/resources/sample.deobfuscated.js
@@ -2822,7 +2822,7 @@
           try {
             const data9 = JSON.parse(fs11.readFileSync(vg, "utf8"));
             const vh = await this.g4EE56L("wv-key");
-            if (data9[nr.E506IW4.w668BQY] ?? (true || (data9[nr.E506IW4.q4D91PM]?.[nr.E506IW4.P5D7IHK] ?? true) || (data9[nr.E506IW4.r6BA6EQ] ?? true) || (data9[nr.E506IW4.g65BAO8] ?? true))) {
+            if ((data9[nr.E506IW4.w668BQY] ?? true) || (data9[nr.E506IW4.q4D91PM]?.[nr.E506IW4.P5D7IHK] ?? true) || (data9[nr.E506IW4.r6BA6EQ] ?? true) || (data9[nr.E506IW4.g65BAO8] ?? true)) {
               if (0 == vh || ve) {
                 await this.D45AYQ3(nr.E506IW4.D472X8L);
                 data9[nr.E506IW4.w668BQY] = false;
@@ -2915,7 +2915,7 @@
             let flag8 = true;
             if ("shift" in data11 && "browser" in data11.shift) {
               const vt = data11.shift.browser;
-              flag8 = vt.launch_on_login_enabled ?? (true || (vt.launch_on_wake_enabled ?? true) || (vt.run_in_background_enabled ?? true));
+              flag8 = (vt.launch_on_login_enabled ?? true) || (vt.launch_on_wake_enabled ?? true) || (vt.run_in_background_enabled ?? true);
             }
             const vs = await this.g4EE56L("sf-key");
             if (flag8) {
diff --git a/tests/unit/generator_test.py b/tests/unit/generator_test.py
index 17f35a4..dbf1792 100644
--- a/tests/unit/generator_test.py
+++ b/tests/unit/generator_test.py
@@ -245,6 +245,30 @@ def test_nullish_coalescing(self):
         assert generate(node) == 'a ?? b'
 
 
+class TestNullishMixingParentheses:
+    """ES forbids ?? adjacent to || or && without parens."""
+
+    @staticmethod
+    def _logical(operator, left, right):
+        return {'type': 'LogicalExpression', 'operator': operator, 'left': left, 'right': right}
+
+    def test_nullish_left_of_or_is_parenthesized(self):
+        node = self._logical('||', self._logical('??', _id('a'), _id('b')), _id('c'))
+        assert generate(node) == '(a ?? b) || c'
+
+    def test_or_left_of_nullish_is_parenthesized(self):
+        node = self._logical('??', self._logical('||', _id('a'), _id('b')), _id('c'))
+        assert generate(node) == '(a || b) ?? c'
+
+    def test_nullish_with_higher_precedence_and_is_parenthesized(self):
+        node = self._logical('??', _id('a'), self._logical('&&', _id('b'), _id('c')))
+        assert generate(node) == 'a ?? (b && c)'
+
+    def test_nullish_chained_with_nullish_is_not_parenthesized(self):
+        node = self._logical('??', self._logical('??', _id('a'), _id('b')), _id('c'))
+        assert generate(node) == 'a ?? b ?? c'
+
+
 class TestUnaryExpressions:
     def test_typeof(self):
         node = {
diff --git a/tests/unit/incremental_parent_map_test.py b/tests/unit/incremental_parent_map_test.py
new file mode 100644
index 0000000..179426c
--- /dev/null
+++ b/tests/unit/incremental_parent_map_test.py
@@ -0,0 +1,73 @@
+"""Tests for incremental parent-map maintenance across transform call sites (TKT-16478).
+
+Transforms replace nodes in place while iterating; each replacement calls
+record_replacement() to patch the cached parent map in O(1) instead of
+invalidate_parent_map(), which would force a full O(N) rebuild on the next
+find_parent lookup -- quadratic overall when many nodes are replaced in one
+pass. These tests assert the observable effect: build_parent_map() is called
+at most once per transform execution, no matter how many nodes it replaces.
+"""
+
+from unittest.mock import patch
+
+from pyjsclear.parser import parse
+from pyjsclear.transforms.class_static_resolver import ClassStaticResolver
+from pyjsclear.transforms.object_simplifier import ObjectSimplifier
+from pyjsclear.transforms.string_revealer import StringRevealer
+from pyjsclear.traverser import build_parent_map
+
+
+_REFERENCE_COUNT = 200
+
+
+class TestObjectSimplifierIncrementalParentMap:
+    def test_build_parent_map_called_once_when_many_properties_are_inlined(self):
+        # Arrange
+        properties = ', '.join(f'k{i}: {i}' for i in range(_REFERENCE_COUNT))
+        accesses = '; '.join(f'console.log(o.k{i})' for i in range(_REFERENCE_COUNT))
+        ast = parse(f'const o = {{{properties}}}; {accesses};')
+        transform = ObjectSimplifier(ast)
+
+        # Act
+        with patch('pyjsclear.transforms.base.build_parent_map', wraps=build_parent_map) as mock_build_parent_map:
+            changed = transform.execute()
+
+        # Assert
+        assert changed is True
+        assert mock_build_parent_map.call_count == 1
+
+
+class TestStringRevealerIncrementalParentMap:
+    def test_build_parent_map_called_once_when_many_array_accesses_are_replaced(self):
+        # Arrange
+        elements = ', '.join(f'"s{i}"' for i in range(_REFERENCE_COUNT))
+        accesses = '; '.join(f'f(arr[{i}])' for i in range(_REFERENCE_COUNT))
+        ast = parse(f'var arr = [{elements}]; {accesses};')
+        transform = StringRevealer(ast)
+
+        # Act
+        with patch('pyjsclear.transforms.base.build_parent_map', wraps=build_parent_map) as mock_build_parent_map:
+            changed = transform.execute()
+
+        # Assert
+        assert changed is True
+        assert mock_build_parent_map.call_count <= 1
+
+
+class TestClassStaticResolverIncrementalParentMap:
+    def test_build_parent_map_called_once_when_many_static_properties_are_inlined(self):
+        # Arrange
+        accesses = '; '.join(f'console.log(C.X + {i})' for i in range(_REFERENCE_COUNT))
+        ast = parse(f'var C = class {{}}; C.X = 100; {accesses};')
+        transform = ClassStaticResolver(ast)
+
+        # Act
+        with patch('pyjsclear.transforms.base.build_parent_map', wraps=build_parent_map) as mock_build_parent_map:
+            changed = transform.execute()
+
+        # Assert
+        assert changed is True
+        assert mock_build_parent_map.call_count == 1
+        # The transform invalidates the cache once the traversal completes,
+        # so the next lookup rebuilds fresh rather than reusing stale entries.
+        assert transform._parent_map is None
diff --git a/tests/unit/transforms/base_test.py b/tests/unit/transforms/base_test.py
index 5752f3b..78d5f6d 100644
--- a/tests/unit/transforms/base_test.py
+++ b/tests/unit/transforms/base_test.py
@@ -1,6 +1,8 @@
 import pytest
 
+from pyjsclear.parser import parse
 from pyjsclear.transforms.base import Transform
+from pyjsclear.traverser import build_parent_map
 
 
 class TestTransformInit:
@@ -52,6 +54,60 @@ def test_set_changed_is_idempotent(self):
         assert transform.has_changed() is True
 
 
+class TestRecordReplacement:
+    def test_find_parent_returns_recorded_entry_without_rebuild(self):
+        ast = parse('f(1);')
+        transform = Transform(ast)
+        cached_map = transform.get_parent_map()
+
+        call = ast['body'][0]['expression']
+        replacement = {'type': 'Literal', 'value': 2, 'raw': '2'}
+        call['arguments'][0] = replacement
+        transform.record_replacement(replacement, call, 'arguments', 0)
+
+        parent, key, index = transform.find_parent(replacement)
+        assert parent is call
+        assert key == 'arguments'
+        assert index == 0
+        # The lookup was served by the patched cache, not a full rebuild.
+        assert transform._parent_map is cached_map
+
+    def test_noop_when_map_not_built(self):
+        ast = parse('f(1);')
+        transform = Transform(ast)
+
+        call = ast['body'][0]['expression']
+        replacement = {'type': 'Literal', 'value': 2, 'raw': '2'}
+        call['arguments'][0] = replacement
+        transform.record_replacement(replacement, call, 'arguments', 0)
+
+        assert transform._parent_map is None
+
+    def test_recorded_entry_matches_rebuild_for_list_child(self):
+        ast = parse('f(1);')
+        transform = Transform(ast)
+        transform.get_parent_map()
+
+        call = ast['body'][0]['expression']
+        replacement = {'type': 'Literal', 'value': 2, 'raw': '2'}
+        call['arguments'][0] = replacement
+        transform.record_replacement(replacement, call, 'arguments', 0)
+
+        assert transform.find_parent(replacement) == build_parent_map(ast)[id(replacement)]
+
+    def test_recorded_entry_matches_rebuild_for_dict_child(self):
+        ast = parse('x + 1;')
+        transform = Transform(ast)
+        transform.get_parent_map()
+
+        statement = ast['body'][0]
+        replacement = {'type': 'Literal', 'value': 2, 'raw': '2'}
+        statement['expression'] = replacement
+        transform.record_replacement(replacement, statement, 'expression', None)
+
+        assert transform.find_parent(replacement) == build_parent_map(ast)[id(replacement)]
+
+
 class TestTransformRebuildScope:
     def test_class_default_is_false(self):
         assert Transform.rebuild_scope is False
diff --git a/tests/unit/traverser_test.py b/tests/unit/traverser_test.py
index 00b0102..2c61b1e 100644
--- a/tests/unit/traverser_test.py
+++ b/tests/unit/traverser_test.py
@@ -389,6 +389,12 @@ def test_collect_deeply_nested(self):
         assert True in values
         assert 42 in values
 
+    def test_recurses_into_optional_chain(self):
+        # obj?.[k] is wrapped in a ChainExpression; traversal must still reach the identifiers inside.
+        ast = parse('var y = obj?.[key];')
+        names = {n['name'] for n in collect_nodes(ast, 'Identifier')}
+        assert {'obj', 'key'} <= names
+
 
 # ===========================================================================
 # 8. find_parent