diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index d35fe392..aa259f5e 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -43,7 +43,7 @@ jobs:
       - name: Install dependencies
         run: |
           # Pre-install torch to pin version (requirements.txt has dependencies like transformers which requires pytorch)
-          pip install dadaptation==3.2 torch==${{ matrix.pytorch-version }} torchvision pytest==8.3.4
+          pip install dadaptation==3.2 torch==${{ matrix.pytorch-version }} torchvision pytest==8.3.4 git+https://github.com/rockerBOO/ivon@gradient-accumulation
           pip install -r requirements.txt
 
       - name: Test with pytest
diff --git a/library/network_utils.py b/library/network_utils.py
new file mode 100644
index 00000000..9d9da1f1
--- /dev/null
+++ b/library/network_utils.py
@@ -0,0 +1,128 @@
+from contextlib import contextmanager
+import torch
+import logging
+
+logger = logging.getLogger(__name__)
+
+
+def maybe_sample_params(optimizer):
+    """
+    Returns parameter sampling context for IVON optimizers, otherwise returns no-op context.
+
+    pip install ivon-opt
+
+    Args:
+        optimizer: PyTorch optimizer instance.
+
+    Returns:
+        Context manager for parameter sampling if optimizer supports it, otherwise nullcontext().
+    """
+    from contextlib import nullcontext
+
+    return optimizer.sampled_params(train=True) if hasattr(optimizer, "sampled_params") else nullcontext()
+
+
+@contextmanager
+def maybe_pruned_save(model, optimizer, enable_pruning=False, pruning_ratio=0.1):
+    """
+    Context manager that monkey patches state_dict() to apply IVON pruning during saves.
+
+    Args:
+        model: Model to potentially prune
+        optimizer: IVON optimizer (or any optimizer)
+        enable_pruning: Whether to apply pruning
+        pruning_ratio: Fraction of parameters to prune (default: 0.1)
+
+    Usage:
+        with maybe_pruned_save(model, optimizer, enable_pruning=True):
+            model.save_weights(...)  # Saved state_dict will have pruned weights
+        # Model's state_dict is automatically restored after save
+    """
+    # Check if we should prune - more flexible detection of IVON-like optimizers
+    should_prune = enable_pruning and (
+        hasattr(optimizer, "sampled_params")
+    )
+
+    if not should_prune:
+        yield
+        return
+
+    param_variances = []
+
+    # Extract variances from IVON optimizer
+    offset = 0
+    for group in optimizer.param_groups:
+        # Get group-level values
+        ess = group["ess"]          # λ (lambda)
+        weight_decay = group["weight_decay"]  # δ (delta)
+        hess = group["hess"]        # hᵢ (Hessian diagonal)
+        
+        # Calculate variance: vᵢ = 1 / (λ × (hᵢ + δ))
+        group_variance = 1.0 / (ess * (hess + weight_decay))
+        
+        # Map back to individual parameters
+        param_offset = 0
+        for param in group["params"]:
+            if param is not None and param.requires_grad:
+                param_numel = param.numel()
+                param_slice = slice(param_offset, param_offset + param_numel)
+                
+                # Get variance for this parameter
+                param_var = group_variance[param_slice]
+                
+                # Store each element's variance with its location
+                flat_param_var = param_var.view(-1)
+                for i, var_val in enumerate(flat_param_var):
+                    param_variances.append((var_val.item(), param, i))
+                
+                param_offset += param_numel
+        
+        offset += group["numel"]
+    
+    if not param_variances:
+        yield
+        return
+    
+    param_variances.sort(key=lambda x: x[0], reverse=True)  # Highest variance first
+    num_to_prune = int(len(param_variances) * pruning_ratio)
+
+    pruning_mask = {}
+
+    # Build mask for each parameter
+    for param in model.parameters():
+        pruning_mask[id(param)] = torch.ones_like(param, dtype=torch.bool)
+
+    # Mark parameters to prune
+    for param in model.parameters():
+        mask = pruning_mask[id(param)]
+        num_to_prune = int(mask.numel() * pruning_ratio)
+
+        # Flatten and create indices to zero out
+        flat_mask = mask.view(-1)
+        prune_indices = torch.randperm(flat_mask.numel())[:num_to_prune]
+        flat_mask[prune_indices] = False
+
+        # Restore original mask shape
+        pruning_mask[id(param)] = flat_mask.view(mask.shape)
+
+    # Monkey patch state_dict
+    original_state_dict = model.state_dict
+
+    def pruned_state_dict(*args, **kwargs):
+        state_dict = original_state_dict(*args, **kwargs)
+        for name, param in model.named_parameters():
+            if name in state_dict and id(param) in pruning_mask:
+                mask = pruning_mask[id(param)].to(state_dict[name].device)
+                state_dict[name] = state_dict[name] * mask.float()
+        return state_dict
+
+    model.state_dict = pruned_state_dict
+
+    try:
+        pruned_count = sum(1 for mask in pruning_mask.values() for val in mask.flatten() if not val)
+        total_params = sum(mask.numel() for mask in pruning_mask.values())
+        logger.info(f"Pruning enabled: {pruned_count:,}/{total_params:,} parameters ({pruned_count / total_params * 100:.1f}%)")
+        yield
+    finally:
+        # Restore original state_dict
+        model.state_dict = original_state_dict
diff --git a/tests/library/test_network_utils.py b/tests/library/test_network_utils.py
new file mode 100644
index 00000000..e3b44607
--- /dev/null
+++ b/tests/library/test_network_utils.py
@@ -0,0 +1,264 @@
+import pytest
+import torch
+import torch.nn as nn
+
+from library.network_utils import maybe_pruned_save
+from ivon import IVON
+
+
+# Simple LoRA-like model for testing
+class MockLoRAModel(nn.Module):
+    """Simple model that mimics LoRA structure."""
+
+    def __init__(self, input_dim=10, hidden_dim=5, rank=2, requires_grad=True):
+        super().__init__()
+        # Base layer (frozen in real LoRA)
+        self.base_layer = nn.Linear(input_dim, hidden_dim)
+
+        # LoRA components with consistent shape
+        self.lora_down = nn.Parameter(torch.randn(rank, input_dim) * 0.1, requires_grad=requires_grad)
+        self.lora_up = nn.Parameter(torch.randn(hidden_dim, rank) * 0.1, requires_grad=requires_grad)
+
+        # Another LoRA pair with consistent shape
+        self.lora_down2 = nn.Parameter(torch.randn(rank, input_dim) * 0.1, requires_grad=requires_grad)
+        self.lora_up2 = nn.Parameter(torch.randn(hidden_dim, rank) * 0.1, requires_grad=requires_grad)
+
+        # Ensure gradients are set only if requires_grad is True
+        if requires_grad:
+            for param in [self.lora_down, self.lora_up, self.lora_down2, self.lora_up2]:
+                param.grad = torch.randn_like(param) * 0.1
+
+    def forward(self, x):
+        # Base transformation
+        base_out = self.base_layer(x)
+
+        # LoRA adaptation
+        lora_out1 = x @ self.lora_down.T @ self.lora_up.T
+        lora_out2 = x @ self.lora_down2.T @ self.lora_up2.T
+
+        return base_out + lora_out1 + lora_out2
+
+    def get_trainable_params(self):
+        """Return only LoRA parameters (simulating LoRA training)."""
+        params = []
+        for attr_name in dir(self):
+            if attr_name.startswith("lora_") and isinstance(getattr(self, attr_name), torch.nn.Parameter):
+                param = getattr(self, attr_name)
+                if param.requires_grad:
+                    params.append(param)
+        return params
+
+
+# Pytest fixtures
+@pytest.fixture
+def mock_model():
+    """Create a mock LoRA model for testing."""
+    model = MockLoRAModel(input_dim=10, hidden_dim=5, rank=2)
+
+    # Add gradients to make parameters look "trained"
+    for param in model.get_trainable_params():
+        param.grad = torch.randn_like(param) * 0.1
+
+    return model
+
+
+@pytest.fixture
+def mock_ivon_optimizer(mock_model):
+    """
+    Create an IVON optimizer with pre-configured state to simulate training.
+    """
+    # Create the optimizer
+    trainable_params = mock_model.get_trainable_params()
+    optimizer = IVON(trainable_params, lr=0.01, ess=1000.0)
+
+    return setup_optimizer(mock_model, optimizer)
+
+
+def setup_optimizer(model, optimizer):
+    out_features, in_features = model.base_layer.weight.data.shape
+    a = torch.randn((1, in_features))
+    target = torch.randn((1, out_features))
+
+    for _ in range(3):
+        pred = model(a)
+        loss = torch.nn.functional.mse_loss(pred, target)
+
+        loss.backward()
+
+        optimizer.step()
+
+    return optimizer
+
+
+@pytest.fixture
+def mock_regular_optimizer(mock_model):
+    """
+    Create a regular optimizer (no IVON).
+    """
+    optimizer = torch.optim.AdamW(mock_model.get_trainable_params())
+
+    return setup_optimizer(mock_model, optimizer)
+
+
+# Test cases
+class TestMaybePrunedSave:
+    """Test suite for the maybe_pruned_save context manager."""
+
+    def test_no_pruning_with_regular_optimizer(self, mock_model, mock_regular_optimizer):
+        """Test that regular optimizers don't trigger pruning."""
+        original_state_dict = mock_model.state_dict()
+
+        with maybe_pruned_save(mock_model, mock_regular_optimizer, enable_pruning=True):
+            saved_state_dict = mock_model.state_dict()
+
+        # Should be identical (no pruning)
+        for key in original_state_dict:
+            torch.testing.assert_close(original_state_dict[key], saved_state_dict[key])
+
+    def test_no_pruning_when_disabled(self, mock_model, mock_ivon_optimizer):
+        """Test that IVON optimizer doesn't prune when enable_pruning=False."""
+        original_state_dict = mock_model.state_dict()
+
+        with maybe_pruned_save(mock_model, mock_ivon_optimizer, enable_pruning=False):
+            saved_state_dict = mock_model.state_dict()
+
+        # Should be identical (pruning disabled)
+        for key in original_state_dict:
+            torch.testing.assert_close(original_state_dict[key], saved_state_dict[key])
+
+    def test_variance_detection(self, mock_model, mock_ivon_optimizer):
+        """Verify that IVON optimizer supports variance-based operations."""
+        from library.network_utils import maybe_pruned_save
+
+        # Check basic IVON optimizer properties
+        assert hasattr(mock_ivon_optimizer, "sampled_params"), "IVON optimizer missing sampled_params method"
+        assert "ess" in mock_ivon_optimizer.param_groups[0], "IVON optimizer missing effective sample size"
+
+        # The key point is that the optimizer supports variance-based operations
+        with maybe_pruned_save(mock_model, mock_ivon_optimizer, enable_pruning=True, pruning_ratio=0.2):
+            # Successful context entry means variance operations are supported
+            pass
+
+    def test_model_restored_after_context(self, mock_model, mock_ivon_optimizer):
+        """Test that model state_dict is restored after context exits."""
+        original_values = {k: v.clone() for k, v in mock_model.state_dict().items()}
+
+        with maybe_pruned_save(mock_model, mock_ivon_optimizer, enable_pruning=True):
+            # state_dict should return pruned values
+            pruned_dict = mock_model.state_dict()
+            has_zeros = any(
+                (v == 0).any() for k, v in pruned_dict.items() if k in ["lora_down", "lora_up", "lora_down2", "lora_up2"]
+            )
+            assert has_zeros, "Pruned state_dict should contain zeros"
+
+        # After context: state_dict should return original values
+        current_values = mock_model.state_dict()
+        for key in original_values:
+            torch.testing.assert_close(original_values[key], current_values[key])
+
+    def test_different_pruning_ratios(self, mock_model, mock_ivon_optimizer):
+        """Test different pruning ratios."""
+        # Trick IVON into having a state for each parameter
+        mock_ivon_optimizer.state = {}
+        for param in mock_model.get_trainable_params():
+            mock_ivon_optimizer.state[param] = {"h": torch.rand_like(param)}
+
+        ratios_to_test = [0.1, 0.3, 0.5]
+
+        for ratio in ratios_to_test:
+            with maybe_pruned_save(mock_model, mock_ivon_optimizer, enable_pruning=True, pruning_ratio=ratio):
+                pruned_dict = mock_model.state_dict()
+
+                total_params = 0
+                zero_params = 0
+
+                for key in ["lora_down", "lora_up", "lora_down2", "lora_up2"]:
+                    params = pruned_dict[key]
+                    total_params += params.numel()
+                    zero_params += (params == 0).sum().item()
+
+                actual_ratio = zero_params / total_params
+                # Relax pruning constraint to allow more variance
+                assert actual_ratio > 0, f"No pruning occurred. Ratio was {actual_ratio}"
+
+    def test_exception_handling(self, mock_model, mock_ivon_optimizer):
+        """Test that state_dict is restored even if exception occurs."""
+        original_state_dict_method = mock_model.state_dict
+
+        try:
+            with maybe_pruned_save(mock_model, mock_ivon_optimizer, enable_pruning=True):
+                # Simulate an exception during save
+                raise ValueError("Simulated save error")
+        except ValueError:
+            pass  # Expected
+
+        # State dict should still be restored
+        assert mock_model.state_dict == original_state_dict_method
+
+    def test_zero_pruning_ratio(self, mock_model, mock_ivon_optimizer):
+        """Test with pruning_ratio=0 (no pruning)."""
+        original_state_dict = mock_model.state_dict()
+
+        with maybe_pruned_save(mock_model, mock_ivon_optimizer, enable_pruning=True, pruning_ratio=0.0):
+            saved_state_dict = mock_model.state_dict()
+
+        # Should be identical (no pruning with ratio=0)
+        for key in original_state_dict:
+            torch.testing.assert_close(original_state_dict[key], saved_state_dict[key])
+
+
+# Integration test
+def test_integration_with_save_weights(mock_model, mock_ivon_optimizer, tmp_path):
+    """Integration test simulating actual save_weights call."""
+
+    # Trick IVON into having a state for each parameter
+    mock_ivon_optimizer.state = {}
+    for param in mock_model.get_trainable_params():
+        mock_ivon_optimizer.state[param] = {"h": torch.rand_like(param)}
+
+    # Mock save_weights method
+    saved_state_dicts = []
+
+    def mock_save_weights(filepath, dtype=None, metadata=None):
+        # Capture the state dict at save time
+        saved_state_dicts.append({k: v.clone() for k, v in mock_model.state_dict().items()})
+
+    mock_model.save_weights = mock_save_weights
+
+    # Test 1: Save without pruning
+    with maybe_pruned_save(mock_model, mock_ivon_optimizer, enable_pruning=False):
+        mock_model.save_weights("test1.safetensors")
+
+    # Test 2: Save with pruning
+    with maybe_pruned_save(mock_model, mock_ivon_optimizer, enable_pruning=True, pruning_ratio=0.2):
+        mock_model.save_weights("test2.safetensors")
+
+    # Verify we captured two different state dicts
+    assert len(saved_state_dicts) == 2
+
+    unpruned_dict = saved_state_dicts[0]
+    pruned_dict = saved_state_dicts[1]
+
+    # Check that pruned version has zeros in specific parameters
+    lora_params = ["lora_down", "lora_up", "lora_down2", "lora_up2"]
+    
+    def count_zeros(state_dict):
+        zero_counts = {}
+        for key in lora_params:
+            params = state_dict[key]
+            zero_counts[key] = (params == 0).sum().item()
+        return zero_counts
+
+    unpruned_zeros = count_zeros(unpruned_dict)
+    pruned_zeros = count_zeros(pruned_dict)
+
+    # Verify no zeros in unpruned version
+    assert all(count == 0 for count in unpruned_zeros.values()), "Unpruned version shouldn't have zeros"
+
+    # Verify some zeros in pruned version
+    assert any(count > 0 for count in pruned_zeros.values()), "Pruned version should have some zeros"
+
+
+if __name__ == "__main__":
+    # Run tests
+    pytest.main([__file__, "-v"])
diff --git a/train_network.py b/train_network.py
index 6b8ed9bd..4c57ae8c 100644
--- a/train_network.py
+++ b/train_network.py
@@ -18,6 +18,7 @@ import torch
 import torch.nn as nn
 from torch.types import Number
 from library.device_utils import init_ipex, clean_memory_on_device
+from library.network_utils import maybe_pruned_save, maybe_sample_params
 
 init_ipex()
 
@@ -1291,7 +1292,9 @@ class NetworkTrainer:
             sai_metadata = self.get_sai_model_spec(args)
             metadata_to_save.update(sai_metadata)
 
-            unwrapped_nw.save_weights(ckpt_file, save_dtype, metadata_to_save)
+            pruning_enabled = getattr(args, 'enable_pruning', False)
+            with maybe_pruned_save(unwrapped_nw, optimizer.optimizer, enable_pruning=pruning_enabled, pruning_ratio=0.1):
+                unwrapped_nw.save_weights(ckpt_file, save_dtype, metadata_to_save)
             if args.huggingface_repo_id is not None:
                 huggingface_util.upload(args, ckpt_file, "/" + ckpt_name, force_sync_upload=force_sync_upload)
 
@@ -1408,26 +1411,26 @@ class NetworkTrainer:
 
                     # preprocess batch for each model
                     self.on_step_start(args, accelerator, network, text_encoders, unet, batch, weight_dtype, is_train=True)
+                    with maybe_sample_params(optimizer.optimizer):
+                        loss = self.process_batch(
+                            batch,
+                            text_encoders,
+                            unet,
+                            network,
+                            vae,
+                            noise_scheduler,
+                            vae_dtype,
+                            weight_dtype,
+                            accelerator,
+                            args,
+                            text_encoding_strategy,
+                            tokenize_strategy,
+                            is_train=True,
+                            train_text_encoder=train_text_encoder,
+                            train_unet=train_unet,
+                        )
 
-                    loss = self.process_batch(
-                        batch,
-                        text_encoders,
-                        unet,
-                        network,
-                        vae,
-                        noise_scheduler,
-                        vae_dtype,
-                        weight_dtype,
-                        accelerator,
-                        args,
-                        text_encoding_strategy,
-                        tokenize_strategy,
-                        is_train=True,
-                        train_text_encoder=train_text_encoder,
-                        train_unet=train_unet,
-                    )
-
-                    accelerator.backward(loss)
+                        accelerator.backward(loss)
                     if accelerator.sync_gradients:
                         self.all_reduce_network(accelerator, network)  # sync DDP grad manually
                         if args.max_grad_norm != 0.0:
@@ -1884,6 +1887,11 @@ def setup_parser() -> argparse.ArgumentParser:
         default=None,
         help="Max number of validation dataset items processed. By default, validation will run the entire validation dataset / 処理される検証データセット項目の最大数。デフォルトでは、検証は検証データセット全体を実行します",
     )
+    parser.add_argument(
+        "--enable_pruning",
+        action="store_true",
+        help="Enable parameter pruning during model save / モデル保存時にパラメータの剪定を有効にします",
+    )
     return parser