diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 5248321..c5ff2fb 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -47,7 +47,7 @@ jobs:
       - name: Format
         run: uv run ruff format --check
       - name: Test
-        run: uv run pytest -v --cov=patchdiff --cov-report=term-missing
+        run: uv run pytest -v --cov=patchdiff --cov-report=term-missing --cov-fail-under=100
 
   build:
     name: Build and test wheel
diff --git a/patchdiff/produce.py b/patchdiff/produce.py
index f4cb365..e37b085 100644
--- a/patchdiff/produce.py
+++ b/patchdiff/produce.py
@@ -98,6 +98,9 @@ def record_replace(self, path: Pointer, old_value: Any, new_value: Any) -> None:
 class DictProxy:
     """Proxy for dict objects that tracks mutations and generates patches."""
 
+    __slots__ = ("_data", "_path", "_proxies", "_recorder")
+    __hash__ = None  # dicts are unhashable
+
     def __init__(self, data: Dict, recorder: PatchRecorder, path: Pointer):
         self._data = data
         self._recorder = recorder
@@ -217,6 +220,21 @@ def popitem(self):
             del self._proxies[key]
         return key, value
 
+    def values(self):
+        """Return proxied values so nested mutations are tracked."""
+        for key in self._data:
+            yield self._wrap(key, self._data[key])
+
+    def items(self):
+        """Return (key, proxied_value) pairs so nested mutations are tracked."""
+        for key in self._data:
+            yield key, self._wrap(key, self._data[key])
+
+    def __ior__(self, other):
+        """Implement |= operator (merge update)."""
+        self.update(other)
+        return self
+
 
 # Add simple reader methods to DictProxy
 _add_reader_methods(
@@ -226,18 +244,32 @@ def popitem(self):
         "__contains__",
         "__repr__",
         "__iter__",
+        # __reversed__ returns keys (not values), so pass-through is fine
         "__reversed__",
         "keys",
-        "values",
-        "items",
+        # values() and items() are implemented as custom methods above
+        # to return proxied nested objects
         "copy",
+        "__str__",
+        "__format__",
+        "__eq__",
+        "__ne__",
+        "__or__",
+        "__ror__",
     ],
 )
+# Skipped dict methods:
+# - fromkeys: classmethod, not relevant for proxy instances
+# - __class_getitem__: typing support (dict[str, int]), not relevant for instances
+# - __lt__, __le__, __gt__, __ge__: dicts don't support ordering comparisons
 
 
 class ListProxy:
     """Proxy for list objects that tracks mutations and generates patches."""
 
+    __slots__ = ("_data", "_path", "_proxies", "_recorder")
+    __hash__ = None  # lists are unhashable
+
     def __init__(self, data: List, recorder: PatchRecorder, path: Pointer):
         self._data = data
         self._recorder = recorder
@@ -466,6 +498,31 @@ def sort(self, *args, **kwargs) -> None:
         # Invalidate all proxy caches as positions changed
         self._proxies.clear()
 
+    def __iter__(self):
+        """Iterate over list elements, wrapping nested structures in proxies."""
+        for i in range(len(self._data)):
+            yield self._wrap(i, self._data[i])
+
+    def __reversed__(self):
+        """Iterate in reverse, wrapping nested structures in proxies."""
+        for i in range(len(self._data) - 1, -1, -1):
+            yield self._wrap(i, self._data[i])
+
+    def __iadd__(self, other):
+        """Implement += operator (in-place extend)."""
+        self.extend(other)
+        return self
+
+    def __imul__(self, n):
+        """Implement *= operator (in-place repeat)."""
+        if n <= 0:
+            self.clear()
+        elif n > 1:
+            original = list(self._data)
+            for _ in range(n - 1):
+                self.extend(original)
+        return self
+
 
 # Add simple reader methods to ListProxy
 _add_reader_methods(
@@ -474,18 +531,34 @@ def sort(self, *args, **kwargs) -> None:
         "__len__",
         "__contains__",
         "__repr__",
-        "__iter__",
-        "__reversed__",
+        # __iter__ and __reversed__ are implemented as custom methods above
+        # to return proxied nested objects
         "index",
         "count",
         "copy",
+        "__str__",
+        "__format__",
+        "__eq__",
+        "__ne__",
+        "__lt__",
+        "__le__",
+        "__gt__",
+        "__ge__",
+        "__add__",
+        "__mul__",
+        "__rmul__",
     ],
 )
+# Skipped list methods:
+# - __class_getitem__: typing support (list[int]), not relevant for instances
 
 
 class SetProxy:
     """Proxy for set objects that tracks mutations and generates patches."""
 
+    __slots__ = ("_data", "_path", "_recorder")
+    __hash__ = None  # sets are unhashable
+
     def __init__(self, data: Set, recorder: PatchRecorder, path: Pointer):
         self._data = data
         self._recorder = recorder
@@ -564,6 +637,31 @@ def __ixor__(self, other):
                 self.add(value)
         return self
 
+    def difference_update(self, *others):
+        """Remove all elements found in others."""
+        for other in others:
+            for value in other:
+                if value in self._data:
+                    self.remove(value)
+
+    def intersection_update(self, *others):
+        """Keep only elements found in all others."""
+        # Compute the intersection first, then remove what's not in it
+        keep = self._data.copy()
+        for other in others:
+            keep &= set(other)
+        values_to_remove = [v for v in self._data if v not in keep]
+        for value in values_to_remove:
+            self.remove(value)
+
+    def symmetric_difference_update(self, other):
+        """Update with symmetric difference."""
+        for value in other:
+            if value in self._data:
+                self.remove(value)
+            else:
+                self.add(value)
+
 
 # Add simple reader methods to SetProxy
 _add_reader_methods(
@@ -581,8 +679,26 @@ def __ixor__(self, other):
         "issubset",
         "issuperset",
         "copy",
+        "__str__",
+        "__format__",
+        "__eq__",
+        "__ne__",
+        "__le__",
+        "__lt__",
+        "__ge__",
+        "__gt__",
+        "__or__",
+        "__ror__",
+        "__and__",
+        "__rand__",
+        "__sub__",
+        "__rsub__",
+        "__xor__",
+        "__rxor__",
     ],
 )
+# Skipped set methods:
+# - __class_getitem__: typing support (set[int]), not relevant for instances
 
 
 def produce(
diff --git a/tests/test_apply.py b/tests/test_apply.py
index d38c63a..a5df072 100644
--- a/tests/test_apply.py
+++ b/tests/test_apply.py
@@ -34,6 +34,29 @@ def test_apply_list():
     assert a == d
 
 
+def test_apply_empty():
+    a = {
+        "a": [5, 7, 9, {"a", "b", "c"}],
+        "b": 6,
+    }
+    b = {
+        "a": [5, 7, 9, {"a", "b", "c"}],
+        "b": 6,
+    }
+    assert a == b
+
+    ops, rops = diff(a, b)
+
+    assert not ops
+    assert not rops
+
+    c = apply(a, ops)
+    assert c == b
+
+    d = apply(b, rops)
+    assert a == d
+
+
 def test_add_remove_list():
     a = []
     b = [1]
diff --git a/tests/test_produce_core.py b/tests/test_produce_core.py
index 9dff110..4572b2d 100644
--- a/tests/test_produce_core.py
+++ b/tests/test_produce_core.py
@@ -3,6 +3,7 @@
 import pytest
 
 from patchdiff import apply, produce
+from patchdiff.produce import DictProxy, ListProxy, SetProxy
 
 
 def assert_patches_work(base, recipe):
@@ -793,3 +794,78 @@ def recipe(draft):
     assert result["level1"]["sibling"][0]["a"] == 10
 
     assert len(patches) >= 7
+
+
+# -- Proxy API completeness tests --
+# These tests ensure that proxy classes cover all methods of their base types.
+# If a new Python version adds a method to dict/list/set, the corresponding
+# test will fail. To fix it, either:
+# 1. Add the method name to SKIPPED below (if it doesn't need proxying), or
+# 2. Implement it on the proxy class.
+
+# Methods inherited from object that are not part of the container API
+_OBJECT_INTERNALS = {
+    "__class__",
+    "__delattr__",
+    "__dir__",
+    "__doc__",
+    "__getattribute__",
+    "__getstate__",
+    "__init__",
+    "__init_subclass__",
+    "__new__",
+    "__reduce__",
+    "__reduce_ex__",
+    "__setattr__",
+    "__sizeof__",
+    "__subclasshook__",
+}
+
+
+def _unhandled_methods(proxy_cls, base_cls, skipped):
+    """Return methods on base_cls that are missing from proxy_cls and not in skipped."""
+    base_methods = set(dir(base_cls)) - _OBJECT_INTERNALS
+    proxy_methods = set(dir(proxy_cls)) - _OBJECT_INTERNALS
+    return (base_methods - proxy_methods) - set(skipped)
+
+
+# Methods intentionally not implemented on the proxy classes.
+# If a new Python version adds a method to dict/list/set, the test will
+# fail. To fix, either implement the method or add it here.
+_DICT_SKIPPED = {
+    "fromkeys",  # classmethod, not relevant for proxy instances
+    "__class_getitem__",  # typing support (dict[str, int])
+}
+
+_LIST_SKIPPED = {
+    "__class_getitem__",  # typing support (list[int])
+}
+
+_SET_SKIPPED = {
+    "__class_getitem__",  # typing support (set[int])
+}
+
+
+class TestProxyApiCompleteness:
+    """Verify proxy classes implement all methods of their base types."""
+
+    def test_dict_proxy_api_completeness(self):
+        unhandled = _unhandled_methods(DictProxy, dict, _DICT_SKIPPED)
+        assert not unhandled, (
+            f"DictProxy is missing methods from dict: {sorted(unhandled)}. "
+            f"Either implement them on DictProxy or add to _DICT_SKIPPED."
+        )
+
+    def test_list_proxy_api_completeness(self):
+        unhandled = _unhandled_methods(ListProxy, list, _LIST_SKIPPED)
+        assert not unhandled, (
+            f"ListProxy is missing methods from list: {sorted(unhandled)}. "
+            f"Either implement them on ListProxy or add to _LIST_SKIPPED."
+        )
+
+    def test_set_proxy_api_completeness(self):
+        unhandled = _unhandled_methods(SetProxy, set, _SET_SKIPPED)
+        assert not unhandled, (
+            f"SetProxy is missing methods from set: {sorted(unhandled)}. "
+            f"Either implement them on SetProxy or add to _SET_SKIPPED."
+        )
diff --git a/tests/test_produce_dict.py b/tests/test_produce_dict.py
index f785a82..f81504c 100644
--- a/tests/test_produce_dict.py
+++ b/tests/test_produce_dict.py
@@ -102,6 +102,23 @@ def recipe(draft):
     assert patches[0]["op"] == "remove"
 
 
+def test_dict_pop_invalidates_proxy_cache():
+    """Test that pop() invalidates the proxy cache for nested structures."""
+    base = {"nested": {"a": 1}, "other": 2}
+
+    def recipe(draft):
+        # Access nested to populate the proxy cache
+        _ = draft["nested"]["a"]
+        # Pop the key that has a cached proxy
+        draft.pop("nested")
+
+    result, patches, _reverse = produce(base, recipe)
+
+    assert result == {"other": 2}
+    assert len(patches) == 1
+    assert patches[0]["op"] == "remove"
+
+
 def test_dict_update():
     """Test dict.update() operation."""
     base = {"a": 1}
@@ -281,6 +298,23 @@ def recipe(draft):
     assert patches[0]["op"] == "remove"
 
 
+def test_dict_popitem_invalidates_proxy_cache():
+    """Test that popitem() invalidates the proxy cache for nested structures."""
+    base = {"a": {"x": 1}}
+
+    def recipe(draft):
+        # Access nested to populate the proxy cache
+        _ = draft["a"]["x"]
+        # popitem removes the only key which has a cached proxy
+        draft.popitem()
+
+    result, patches, _reverse = produce(base, recipe)
+
+    assert result == {}
+    assert len(patches) == 1
+    assert patches[0]["op"] == "remove"
+
+
 def test_dict_popitem_empty():
     """Test popitem() on empty dict raises KeyError."""
     base = {}
@@ -567,6 +601,98 @@ def recipe(draft):
     assert result == {"a": 1}
 
 
+def test_dict_values_returns_proxied_nested():
+    """Test that values() returns proxied nested objects."""
+    base = {"a": {"x": 1}, "b": {"x": 2}}
+
+    def recipe(draft):
+        for v in draft.values():
+            v["x"] = 99
+
+    result, patches, _reverse = produce(base, recipe)
+
+    assert result == {"a": {"x": 99}, "b": {"x": 99}}
+    assert len(patches) == 2
+
+
+def test_dict_items_returns_proxied_nested():
+    """Test that items() returns proxied nested objects."""
+    base = {"a": {"x": 1}, "b": {"x": 2}}
+
+    def recipe(draft):
+        for k, v in draft.items():
+            v["x"] = 99
+
+    result, patches, _reverse = produce(base, recipe)
+
+    assert result == {"a": {"x": 99}, "b": {"x": 99}}
+    assert len(patches) == 2
+
+
+def test_dict_ior_operator():
+    """Test |= operator (merge update) on dict proxy."""
+    base = {"a": 1}
+
+    def recipe(draft):
+        draft |= {"b": 2, "c": 3}
+
+    result, patches, _reverse = produce(base, recipe)
+
+    assert result == {"a": 1, "b": 2, "c": 3}
+    assert len(patches) == 2
+
+
+def test_dict_or_operator():
+    """Test | operator (merge) on dict proxy returns new dict."""
+    base = {"a": 1}
+
+    def recipe(draft):
+        merged = draft | {"b": 2}
+        assert isinstance(merged, dict)
+        assert merged == {"a": 1, "b": 2}
+
+    _result, patches, _reverse = produce(base, recipe)
+
+    assert patches == []  # No mutations to draft
+
+
+def test_dict_eq():
+    """Test __eq__ on dict proxy."""
+    base = {"a": 1, "b": 2}
+
+    def recipe(draft):
+        assert draft == {"a": 1, "b": 2}
+        assert not (draft == {"a": 1})
+
+    produce(base, recipe)
+
+
+def test_dict_ne():
+    """Test __ne__ on dict proxy."""
+    base = {"a": 1}
+
+    def recipe(draft):
+        assert draft != {"b": 2}
+        assert not (draft != {"a": 1})
+
+    produce(base, recipe)
+
+
+def test_dict_bool():
+    """Test __bool__ on dict proxy."""
+    base_empty = {}
+    base_full = {"a": 1}
+
+    def recipe_empty(draft):
+        assert not draft
+
+    def recipe_full(draft):
+        assert draft
+
+    produce(base_empty, recipe_empty)
+    produce(base_full, recipe_full)
+
+
 def test_dict_get_none_explicit():
     """Test get() with explicit None default."""
     base = {"a": 1}
diff --git a/tests/test_produce_list.py b/tests/test_produce_list.py
index 6e455e9..cd11301 100644
--- a/tests/test_produce_list.py
+++ b/tests/test_produce_list.py
@@ -982,3 +982,160 @@ def recipe(draft):
     result, _patches, _reverse = produce(base, recipe)
 
     assert result == []
+
+
+def test_list_iter_returns_proxied_nested():
+    """Test that __iter__ returns proxied nested objects."""
+    base = [{"x": 1}, {"x": 2}]
+
+    def recipe(draft):
+        for item in draft:
+            item["x"] = 99
+
+    result, patches, _reverse = produce(base, recipe)
+
+    assert result == [{"x": 99}, {"x": 99}]
+    assert len(patches) == 2
+
+
+def test_list_reversed_returns_proxied_nested():
+    """Test that __reversed__ returns proxied nested objects."""
+    base = [{"x": 1}, {"x": 2}]
+
+    def recipe(draft):
+        for item in reversed(draft):
+            item["x"] = 99
+
+    result, patches, _reverse = produce(base, recipe)
+
+    assert result == [{"x": 99}, {"x": 99}]
+    assert len(patches) == 2
+
+
+def test_list_iadd_operator():
+    """Test += operator (in-place add, like extend) on list proxy."""
+    base = [1, 2]
+
+    def recipe(draft):
+        draft += [3, 4]
+
+    result, patches, _reverse = produce(base, recipe)
+
+    assert result == [1, 2, 3, 4]
+    assert len(patches) == 2
+
+
+def test_list_imul_operator():
+    """Test *= operator (in-place repeat) on list proxy."""
+    base = [1, 2]
+
+    def recipe(draft):
+        draft *= 3
+
+    result, patches, _reverse = produce(base, recipe)
+
+    assert result == [1, 2, 1, 2, 1, 2]
+    assert len(patches) == 4  # 4 new elements added
+
+
+def test_list_imul_zero():
+    """Test *= 0 clears the list."""
+    base = [1, 2, 3]
+
+    def recipe(draft):
+        draft *= 0
+
+    result, patches, _reverse = produce(base, recipe)
+
+    assert result == []
+    assert len(patches) == 3  # 3 elements removed
+
+
+def test_list_add_operator():
+    """Test + operator returns new list, not a proxy."""
+    base = [1, 2]
+
+    def recipe(draft):
+        new = draft + [3, 4]  # noqa: RUF005
+        assert isinstance(new, list)
+        assert new == [1, 2, 3, 4]
+
+    _result, patches, _reverse = produce(base, recipe)
+
+    assert patches == []
+
+
+def test_list_mul_operator():
+    """Test * operator returns new list, not a proxy."""
+    base = [1, 2]
+
+    def recipe(draft):
+        new = draft * 3
+        assert isinstance(new, list)
+        assert new == [1, 2, 1, 2, 1, 2]
+
+    _result, patches, _reverse = produce(base, recipe)
+
+    assert patches == []
+
+
+def test_list_rmul_operator():
+    """Test reverse * operator (int * list) returns new list."""
+    base = [1, 2]
+
+    def recipe(draft):
+        new = 3 * draft
+        assert isinstance(new, list)
+        assert new == [1, 2, 1, 2, 1, 2]
+
+    _result, patches, _reverse = produce(base, recipe)
+
+    assert patches == []
+
+
+def test_list_eq():
+    """Test __eq__ on list proxy."""
+    base = [1, 2, 3]
+
+    def recipe(draft):
+        assert draft == [1, 2, 3]
+        assert not (draft == [1, 2])
+
+    produce(base, recipe)
+
+
+def test_list_ne():
+    """Test __ne__ on list proxy."""
+    base = [1, 2, 3]
+
+    def recipe(draft):
+        assert draft != [1, 2]
+        assert not (draft != [1, 2, 3])
+
+    produce(base, recipe)
+
+
+def test_list_bool():
+    """Test __bool__ on list proxy."""
+
+    def recipe_empty(draft):
+        assert not draft
+
+    def recipe_full(draft):
+        assert draft
+
+    produce([], recipe_empty)
+    produce([1], recipe_full)
+
+
+def test_list_lt_le_gt_ge():
+    """Test comparison operators on list proxy."""
+    base = [1, 2, 3]
+
+    def recipe(draft):
+        assert draft < [1, 2, 4]
+        assert draft <= [1, 2, 3]
+        assert draft > [1, 2, 2]
+        assert draft >= [1, 2, 3]
+
+    produce(base, recipe)
diff --git a/tests/test_produce_set.py b/tests/test_produce_set.py
index dda53b6..89e8208 100644
--- a/tests/test_produce_set.py
+++ b/tests/test_produce_set.py
@@ -535,3 +535,148 @@ def recipe(draft):
     result, _patches, _reverse = produce(base, recipe)
 
     assert result == base
+
+
+def test_set_difference_update_method():
+    """Test difference_update() method on set proxy."""
+    base = {1, 2, 3, 4}
+
+    def recipe(draft):
+        draft.difference_update({2, 4})
+
+    result, patches, _reverse = produce(base, recipe)
+
+    assert result == {1, 3}
+    assert len(patches) == 2
+
+
+def test_set_intersection_update_method():
+    """Test intersection_update() method on set proxy."""
+    base = {1, 2, 3, 4}
+
+    def recipe(draft):
+        draft.intersection_update({2, 3, 5})
+
+    result, patches, _reverse = produce(base, recipe)
+
+    assert result == {2, 3}
+    assert len(patches) == 2  # Removed 1 and 4
+
+
+def test_set_symmetric_difference_update_method():
+    """Test symmetric_difference_update() method on set proxy."""
+    base = {1, 2, 3}
+
+    def recipe(draft):
+        draft.symmetric_difference_update({2, 3, 4})
+
+    result, patches, _reverse = produce(base, recipe)
+
+    assert result == {1, 4}
+    assert len(patches) == 3  # Removed 2, 3, added 4
+
+
+def test_set_or_operator():
+    """Test | operator (union) returns new set, not a proxy."""
+    base = {1, 2, 3}
+
+    def recipe(draft):
+        new = draft | {3, 4, 5}
+        assert isinstance(new, set)
+        assert new == {1, 2, 3, 4, 5}
+
+    _result, patches, _reverse = produce(base, recipe)
+
+    assert patches == []
+
+
+def test_set_and_operator():
+    """Test & operator (intersection) returns new set."""
+    base = {1, 2, 3}
+
+    def recipe(draft):
+        new = draft & {2, 3, 4}
+        assert isinstance(new, set)
+        assert new == {2, 3}
+
+    _result, patches, _reverse = produce(base, recipe)
+
+    assert patches == []
+
+
+def test_set_sub_operator():
+    """Test - operator (difference) returns new set."""
+    base = {1, 2, 3}
+
+    def recipe(draft):
+        new = draft - {2, 4}
+        assert isinstance(new, set)
+        assert new == {1, 3}
+
+    _result, patches, _reverse = produce(base, recipe)
+
+    assert patches == []
+
+
+def test_set_xor_operator():
+    """Test ^ operator (symmetric difference) returns new set."""
+    base = {1, 2, 3}
+
+    def recipe(draft):
+        new = draft ^ {2, 3, 4}
+        assert isinstance(new, set)
+        assert new == {1, 4}
+
+    _result, patches, _reverse = produce(base, recipe)
+
+    assert patches == []
+
+
+def test_set_eq():
+    """Test __eq__ on set proxy."""
+    base = {1, 2, 3}
+
+    def recipe(draft):
+        assert draft == {1, 2, 3}
+        assert not (draft == {1, 2})
+
+    produce(base, recipe)
+
+
+def test_set_ne():
+    """Test __ne__ on set proxy."""
+    base = {1, 2, 3}
+
+    def recipe(draft):
+        assert draft != {1, 2}
+        assert not (draft != {1, 2, 3})
+
+    produce(base, recipe)
+
+
+def test_set_bool():
+    """Test __bool__ on set proxy."""
+
+    def recipe_empty(draft):
+        assert not draft
+
+    def recipe_full(draft):
+        assert draft
+
+    produce(set(), recipe_empty)
+    produce({1}, recipe_full)
+
+
+def test_set_le_lt_ge_gt():
+    """Test comparison operators on set proxy (subset/superset)."""
+    base = {1, 2, 3}
+
+    def recipe(draft):
+        assert draft <= {1, 2, 3, 4}  # subset
+        assert draft <= {1, 2, 3}  # equal is also <=
+        assert draft < {1, 2, 3, 4}  # proper subset
+        assert not (draft < {1, 2, 3})  # not proper subset of equal
+        assert draft >= {1, 2}  # superset
+        assert draft > {1, 2}  # proper superset
+
+    produce(base, recipe)