From 13f54e8bf2c91b75f374afee39997644aa9673cd Mon Sep 17 00:00:00 2001
From: RAHUL KUMAR <hellorahul@google.com>
Date: Thu, 5 Mar 2026 16:31:11 +0530
Subject: [PATCH 1/2] Fix nested list/dict layers not being saved/loaded
 correctly

When a layer stores sub-layers in nested containers (e.g.
self.blocks = [[Dense, Dense], [Dense, Dense]]), the save/load
functions silently skipped inner containers because
_save_container_state and _load_container_state only handled
KerasSaveable items, not nested list/dict/tuple/set.

Add recursive handling of nested containers with index-based
namespacing (_container, _container_1, etc.) to avoid HDF5 path
collisions.

Fixes https://github.com/keras-team/keras/issues/20598
---
 keras/src/saving/saving_lib.py      | 31 ++++++++++++++++++++++++++
 keras/src/saving/saving_lib_test.py | 34 +++++++++++++++++++++++++++++
 2 files changed, 65 insertions(+)

diff --git a/keras/src/saving/saving_lib.py b/keras/src/saving/saving_lib.py
index e73390c28ea3..a0f1b4c5e2b1 100644
--- a/keras/src/saving/saving_lib.py
+++ b/keras/src/saving/saving_lib.py
@@ -893,6 +893,20 @@ def _save_container_state(
                 inner_path=file_utils.join(inner_path, name).replace("\\", "/"),
                 visited_saveables=visited_saveables,
             )
+        elif isinstance(saveable, (list, dict, tuple, set)):
+            name = "_container"
+            if name in used_names:
+                used_names[name] += 1
+                name = f"{name}_{used_names[name]}"
+            else:
+                used_names[name] = 0
+            _save_container_state(
+                saveable,
+                weights_store,
+                assets_store,
+                inner_path=file_utils.join(inner_path, name).replace("\\", "/"),
+                visited_saveables=visited_saveables,
+            )
 
 
 def _load_container_state(
@@ -929,6 +943,23 @@ def _load_container_state(
                 failed_saveables=failed_saveables,
                 error_msgs=error_msgs,
             )
+        elif isinstance(saveable, (list, dict, tuple, set)):
+            name = "_container"
+            if name in used_names:
+                used_names[name] += 1
+                name = f"{name}_{used_names[name]}"
+            else:
+                used_names[name] = 0
+            _load_container_state(
+                saveable,
+                weights_store,
+                assets_store,
+                inner_path=file_utils.join(inner_path, name).replace("\\", "/"),
+                skip_mismatch=skip_mismatch,
+                visited_saveables=visited_saveables,
+                failed_saveables=failed_saveables,
+                error_msgs=error_msgs,
+            )
 
 
 class DiskIOStore:
diff --git a/keras/src/saving/saving_lib_test.py b/keras/src/saving/saving_lib_test.py
index 59f7c3473aed..67e7fb5c123a 100644
--- a/keras/src/saving/saving_lib_test.py
+++ b/keras/src/saving/saving_lib_test.py
@@ -1132,6 +1132,40 @@ def test_bidirectional_lstm_saving(self):
         out = new_model(x)
         self.assertAllClose(ref_out, out)
 
+    def test_nested_list_layer_saving(self):
+        """Test that layers stored in nested lists are saved/loaded."""
+
+        @keras.saving.register_keras_serializable(package="test")
+        class NestedBlockModel(keras.Model):
+            def __init__(self, **kwargs):
+                super().__init__(**kwargs)
+                self.blocks = [
+                    [keras.layers.Dense(8), keras.layers.Dense(8)],
+                    [keras.layers.Dense(8), keras.layers.Dense(8)],
+                ]
+                self.out_layer = keras.layers.Dense(2)
+
+            def call(self, x):
+                for block in self.blocks:
+                    for layer in block:
+                        x = layer(x)
+                return self.out_layer(x)
+
+            def get_config(self):
+                return super().get_config()
+
+        model = NestedBlockModel()
+        x = np.random.random((2, 4))
+        ref_out = model(x)
+
+        temp_filepath = os.path.join(
+            self.get_temp_dir(), "nested_list.keras"
+        )
+        model.save(temp_filepath)
+        new_model = keras.saving.load_model(temp_filepath)
+        out = new_model(x)
+        self.assertAllClose(ref_out, out)
+
     def test_remove_weights_only_saving_and_loading(self):
         def is_remote_path(path):
             return True

From 92c8aa5fe83e22c3ba51c52dd72c7e4a58c8e5b4 Mon Sep 17 00:00:00 2001
From: RAHUL KUMAR <hellorahul@google.com>
Date: Thu, 5 Mar 2026 17:25:39 +0530
Subject: [PATCH 2/2] style: run pre-commit hooks (ruff formatting)

---
 keras/src/saving/saving_lib_test.py | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/keras/src/saving/saving_lib_test.py b/keras/src/saving/saving_lib_test.py
index 67e7fb5c123a..1e8d097886b5 100644
--- a/keras/src/saving/saving_lib_test.py
+++ b/keras/src/saving/saving_lib_test.py
@@ -1158,9 +1158,7 @@ def get_config(self):
         x = np.random.random((2, 4))
         ref_out = model(x)
 
-        temp_filepath = os.path.join(
-            self.get_temp_dir(), "nested_list.keras"
-        )
+        temp_filepath = os.path.join(self.get_temp_dir(), "nested_list.keras")
         model.save(temp_filepath)
         new_model = keras.saving.load_model(temp_filepath)
         out = new_model(x)