diff --git a/families/eagle_vlm/parallel.py b/families/eagle_vlm/parallel.py
index 77f29d0a80..d639386930 100644
--- a/families/eagle_vlm/parallel.py
+++ b/families/eagle_vlm/parallel.py
@@ -82,9 +82,9 @@ def shard_standard_decoder_weights(
             sharded[key] = value
         elif key.endswith((".w_q", ".w_k", ".w_v", ".q_bias", ".k_bias", ".v_bias")):
             sharded[key] = _slice_last_dim(value, rank, tp_size)
-        elif key.endswith((".w_o", ".w_fc2")):
+        elif key.endswith((".w_o", ".w_fc2", ".w_down")):
             sharded[key] = _slice_first_dim(value, rank, tp_size)
-        elif key.endswith((".w_fc1", ".fc1_bias")):
+        elif key.endswith((".w_fc1", ".fc1_bias", ".w_gate", ".w_up")):
             sharded[key] = _slice_last_dim(value, rank, tp_size)
         else:
             sharded[key] = value
diff --git a/families/eagle_vlm/tests/test_parallel_swiglu.py b/families/eagle_vlm/tests/test_parallel_swiglu.py
new file mode 100644
index 0000000000..6fd6e796cd
--- /dev/null
+++ b/families/eagle_vlm/tests/test_parallel_swiglu.py
@@ -0,0 +1,82 @@
+# SPDX-FileCopyrightText: Copyright (c) 2026 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+# SPDX-License-Identifier: Apache-2.0
+
+"""eagle_vlm SwiGLU weight shards must reconstruct the unsharded computation."""
+
+import numpy as np
+import pytest
+
+from ..checkpoint_mapper import WeightDict
+from ..config import ModelConfig
+from ..parallel import ParallelConfig, shard_standard_decoder_weights
+
+
+@pytest.mark.parametrize("tp_size", [1, 2, 4, 8])
+@pytest.mark.parametrize("dtype", [np.float32, np.float16])
+def test_swiglu_rank_shards_reconstruct_weights_and_output(tp_size, dtype):
+    config = ModelConfig(
+        hidden_size=8,
+        intermediate_size=24,
+        num_attention_heads=8,
+        num_key_value_heads=8,
+    )
+    rng = np.random.default_rng(42)
+    weights = WeightDict(
+        {
+            "_attention_size": 8,
+            "_kv_attention_size": 8,
+            "_mlp_size": 24,
+            "embedding": rng.normal(size=(16, 8)).astype(dtype),
+            "layer.0.w_gate": rng.normal(scale=0.2, size=(8, 24)).astype(dtype),
+            "layer.0.w_up": rng.normal(scale=0.2, size=(8, 24)).astype(dtype),
+            "layer.0.w_down": rng.normal(scale=0.2, size=(24, 8)).astype(dtype),
+            "layer.0.post_attn_norm": np.ones(8, dtype=dtype),
+        }
+    )
+    original = {
+        key: value.copy() for key, value in weights.items() if isinstance(value, np.ndarray)
+    }
+    shards = [
+        shard_standard_decoder_weights(config, weights, ParallelConfig(tp_size, rank))
+        for rank in range(tp_size)
+    ]
+
+    for key, axis in (("w_gate", 1), ("w_up", 1), ("w_down", 0)):
+        full = weights[f"layer.0.{key}"]
+        expected_shape = list(full.shape)
+        expected_shape[axis] //= tp_size
+        for shard in shards:
+            part = shard[f"layer.0.{key}"]
+            assert part.shape == tuple(expected_shape)
+            assert part.dtype == dtype
+            assert part.flags.c_contiguous
+        np.testing.assert_array_equal(
+            np.concatenate([shard[f"layer.0.{key}"] for shard in shards], axis=axis),
+            full,
+        )
+
+    for rank, shard in enumerate(shards):
+        assert shard["_mlp_size"] == 24 // tp_size
+        assert isinstance(shard, WeightDict)
+        for key in ("embedding", "layer.0.post_attn_norm"):
+            np.testing.assert_array_equal(shard[key], weights[key])
+        if tp_size > 1:
+            assert shard["_tensor_parallel_rank"] == rank
+    for key, value in original.items():
+        np.testing.assert_array_equal(weights[key], value)
+    assert weights["_mlp_size"] == 24
+
+    inputs = rng.normal(size=(3, 8))
+
+    def evaluate(rank_weights):
+        gate = inputs @ rank_weights["layer.0.w_gate"].astype(np.float64)
+        up = inputs @ rank_weights["layer.0.w_up"].astype(np.float64)
+        return (gate / (1 + np.exp(-gate)) * up) @ rank_weights["layer.0.w_down"].astype(np.float64)
+
+    # Row-parallel down projections are summed by the runtime ALL_REDUCE.
+    np.testing.assert_allclose(
+        sum(evaluate(shard) for shard in shards),
+        evaluate(weights),
+        rtol=1e-12,
+        atol=1e-12,
+    )
diff --git a/families/glm/parallel.py b/families/glm/parallel.py
index 4d88550d49..9bfc5a21c3 100644
--- a/families/glm/parallel.py
+++ b/families/glm/parallel.py
@@ -82,9 +82,9 @@ def shard_standard_decoder_weights(
             sharded[key] = value
         elif key.endswith((".w_q", ".w_k", ".w_v", ".q_bias", ".k_bias", ".v_bias")):
             sharded[key] = _slice_last_dim(value, rank, tp_size)
-        elif key.endswith((".w_o", ".w_fc2")):
+        elif key.endswith((".w_o", ".w_fc2", ".w_down")):
             sharded[key] = _slice_first_dim(value, rank, tp_size)
-        elif key.endswith((".w_fc1", ".fc1_bias")):
+        elif key.endswith((".w_fc1", ".fc1_bias", ".w_gate", ".w_up")):
             sharded[key] = _slice_last_dim(value, rank, tp_size)
         else:
             sharded[key] = value
diff --git a/families/glm/tests/test_parallel_swiglu.py b/families/glm/tests/test_parallel_swiglu.py
new file mode 100644
index 0000000000..98c3a04a27
--- /dev/null
+++ b/families/glm/tests/test_parallel_swiglu.py
@@ -0,0 +1,82 @@
+# SPDX-FileCopyrightText: Copyright (c) 2026 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+# SPDX-License-Identifier: Apache-2.0
+
+"""glm SwiGLU weight shards must reconstruct the unsharded computation."""
+
+import numpy as np
+import pytest
+
+from ..checkpoint_mapper import WeightDict
+from ..config import ModelConfig
+from ..parallel import ParallelConfig, shard_standard_decoder_weights
+
+
+@pytest.mark.parametrize("tp_size", [1, 2, 4, 8])
+@pytest.mark.parametrize("dtype", [np.float32, np.float16])
+def test_swiglu_rank_shards_reconstruct_weights_and_output(tp_size, dtype):
+    config = ModelConfig(
+        hidden_size=8,
+        intermediate_size=24,
+        num_attention_heads=8,
+        num_key_value_heads=8,
+    )
+    rng = np.random.default_rng(42)
+    weights = WeightDict(
+        {
+            "_attention_size": 8,
+            "_kv_attention_size": 8,
+            "_mlp_size": 24,
+            "embedding": rng.normal(size=(16, 8)).astype(dtype),
+            "layer.0.w_gate": rng.normal(scale=0.2, size=(8, 24)).astype(dtype),
+            "layer.0.w_up": rng.normal(scale=0.2, size=(8, 24)).astype(dtype),
+            "layer.0.w_down": rng.normal(scale=0.2, size=(24, 8)).astype(dtype),
+            "layer.0.post_attn_norm": np.ones(8, dtype=dtype),
+        }
+    )
+    original = {
+        key: value.copy() for key, value in weights.items() if isinstance(value, np.ndarray)
+    }
+    shards = [
+        shard_standard_decoder_weights(config, weights, ParallelConfig(tp_size, rank))
+        for rank in range(tp_size)
+    ]
+
+    for key, axis in (("w_gate", 1), ("w_up", 1), ("w_down", 0)):
+        full = weights[f"layer.0.{key}"]
+        expected_shape = list(full.shape)
+        expected_shape[axis] //= tp_size
+        for shard in shards:
+            part = shard[f"layer.0.{key}"]
+            assert part.shape == tuple(expected_shape)
+            assert part.dtype == dtype
+            assert part.flags.c_contiguous
+        np.testing.assert_array_equal(
+            np.concatenate([shard[f"layer.0.{key}"] for shard in shards], axis=axis),
+            full,
+        )
+
+    for rank, shard in enumerate(shards):
+        assert shard["_mlp_size"] == 24 // tp_size
+        assert isinstance(shard, WeightDict)
+        for key in ("embedding", "layer.0.post_attn_norm"):
+            np.testing.assert_array_equal(shard[key], weights[key])
+        if tp_size > 1:
+            assert shard["_tensor_parallel_rank"] == rank
+    for key, value in original.items():
+        np.testing.assert_array_equal(weights[key], value)
+    assert weights["_mlp_size"] == 24
+
+    inputs = rng.normal(size=(3, 8))
+
+    def evaluate(rank_weights):
+        gate = inputs @ rank_weights["layer.0.w_gate"].astype(np.float64)
+        up = inputs @ rank_weights["layer.0.w_up"].astype(np.float64)
+        return (gate / (1 + np.exp(-gate)) * up) @ rank_weights["layer.0.w_down"].astype(np.float64)
+
+    # Row-parallel down projections are summed by the runtime ALL_REDUCE.
+    np.testing.assert_allclose(
+        sum(evaluate(shard) for shard in shards),
+        evaluate(weights),
+        rtol=1e-12,
+        atol=1e-12,
+    )
diff --git a/families/granite/parallel.py b/families/granite/parallel.py
index 998427daf8..d7dc612f10 100644
--- a/families/granite/parallel.py
+++ b/families/granite/parallel.py
@@ -82,9 +82,9 @@ def shard_standard_decoder_weights(
             sharded[key] = value
         elif key.endswith((".w_q", ".w_k", ".w_v", ".q_bias", ".k_bias", ".v_bias")):
             sharded[key] = _slice_last_dim(value, rank, tp_size)
-        elif key.endswith((".w_o", ".w_fc2")):
+        elif key.endswith((".w_o", ".w_fc2", ".w_down")):
             sharded[key] = _slice_first_dim(value, rank, tp_size)
-        elif key.endswith((".w_fc1", ".fc1_bias")):
+        elif key.endswith((".w_fc1", ".fc1_bias", ".w_gate", ".w_up")):
             sharded[key] = _slice_last_dim(value, rank, tp_size)
         else:
             sharded[key] = value
diff --git a/families/granite/tests/test_parallel_swiglu.py b/families/granite/tests/test_parallel_swiglu.py
new file mode 100644
index 0000000000..4cdf6a8b7f
--- /dev/null
+++ b/families/granite/tests/test_parallel_swiglu.py
@@ -0,0 +1,82 @@
+# SPDX-FileCopyrightText: Copyright (c) 2026 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+# SPDX-License-Identifier: Apache-2.0
+
+"""granite SwiGLU weight shards must reconstruct the unsharded computation."""
+
+import numpy as np
+import pytest
+
+from ..checkpoint_mapper import WeightDict
+from ..config import ModelConfig
+from ..parallel import ParallelConfig, shard_standard_decoder_weights
+
+
+@pytest.mark.parametrize("tp_size", [1, 2, 4, 8])
+@pytest.mark.parametrize("dtype", [np.float32, np.float16])
+def test_swiglu_rank_shards_reconstruct_weights_and_output(tp_size, dtype):
+    config = ModelConfig(
+        hidden_size=8,
+        intermediate_size=24,
+        num_attention_heads=8,
+        num_key_value_heads=8,
+    )
+    rng = np.random.default_rng(42)
+    weights = WeightDict(
+        {
+            "_attention_size": 8,
+            "_kv_attention_size": 8,
+            "_mlp_size": 24,
+            "embedding": rng.normal(size=(16, 8)).astype(dtype),
+            "layer.0.w_gate": rng.normal(scale=0.2, size=(8, 24)).astype(dtype),
+            "layer.0.w_up": rng.normal(scale=0.2, size=(8, 24)).astype(dtype),
+            "layer.0.w_down": rng.normal(scale=0.2, size=(24, 8)).astype(dtype),
+            "layer.0.post_attn_norm": np.ones(8, dtype=dtype),
+        }
+    )
+    original = {
+        key: value.copy() for key, value in weights.items() if isinstance(value, np.ndarray)
+    }
+    shards = [
+        shard_standard_decoder_weights(config, weights, ParallelConfig(tp_size, rank))
+        for rank in range(tp_size)
+    ]
+
+    for key, axis in (("w_gate", 1), ("w_up", 1), ("w_down", 0)):
+        full = weights[f"layer.0.{key}"]
+        expected_shape = list(full.shape)
+        expected_shape[axis] //= tp_size
+        for shard in shards:
+            part = shard[f"layer.0.{key}"]
+            assert part.shape == tuple(expected_shape)
+            assert part.dtype == dtype
+            assert part.flags.c_contiguous
+        np.testing.assert_array_equal(
+            np.concatenate([shard[f"layer.0.{key}"] for shard in shards], axis=axis),
+            full,
+        )
+
+    for rank, shard in enumerate(shards):
+        assert shard["_mlp_size"] == 24 // tp_size
+        assert isinstance(shard, WeightDict)
+        for key in ("embedding", "layer.0.post_attn_norm"):
+            np.testing.assert_array_equal(shard[key], weights[key])
+        if tp_size > 1:
+            assert shard["_tensor_parallel_rank"] == rank
+    for key, value in original.items():
+        np.testing.assert_array_equal(weights[key], value)
+    assert weights["_mlp_size"] == 24
+
+    inputs = rng.normal(size=(3, 8))
+
+    def evaluate(rank_weights):
+        gate = inputs @ rank_weights["layer.0.w_gate"].astype(np.float64)
+        up = inputs @ rank_weights["layer.0.w_up"].astype(np.float64)
+        return (gate / (1 + np.exp(-gate)) * up) @ rank_weights["layer.0.w_down"].astype(np.float64)
+
+    # Row-parallel down projections are summed by the runtime ALL_REDUCE.
+    np.testing.assert_allclose(
+        sum(evaluate(shard) for shard in shards),
+        evaluate(weights),
+        rtol=1e-12,
+        atol=1e-12,
+    )
diff --git a/families/olmo/parallel.py b/families/olmo/parallel.py
index f4de318f93..9484cf4c8d 100644
--- a/families/olmo/parallel.py
+++ b/families/olmo/parallel.py
@@ -82,9 +82,9 @@ def shard_standard_decoder_weights(
             sharded[key] = value
         elif key.endswith((".w_q", ".w_k", ".w_v", ".q_bias", ".k_bias", ".v_bias")):
             sharded[key] = _slice_last_dim(value, rank, tp_size)
-        elif key.endswith((".w_o", ".w_fc2")):
+        elif key.endswith((".w_o", ".w_fc2", ".w_down")):
             sharded[key] = _slice_first_dim(value, rank, tp_size)
-        elif key.endswith((".w_fc1", ".fc1_bias")):
+        elif key.endswith((".w_fc1", ".fc1_bias", ".w_gate", ".w_up")):
             sharded[key] = _slice_last_dim(value, rank, tp_size)
         else:
             sharded[key] = value
diff --git a/families/olmo/tests/test_parallel_swiglu.py b/families/olmo/tests/test_parallel_swiglu.py
new file mode 100644
index 0000000000..ee77a49adb
--- /dev/null
+++ b/families/olmo/tests/test_parallel_swiglu.py
@@ -0,0 +1,82 @@
+# SPDX-FileCopyrightText: Copyright (c) 2026 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+# SPDX-License-Identifier: Apache-2.0
+
+"""olmo SwiGLU weight shards must reconstruct the unsharded computation."""
+
+import numpy as np
+import pytest
+
+from ..checkpoint_mapper import WeightDict
+from ..config import ModelConfig
+from ..parallel import ParallelConfig, shard_standard_decoder_weights
+
+
+@pytest.mark.parametrize("tp_size", [1, 2, 4, 8])
+@pytest.mark.parametrize("dtype", [np.float32, np.float16])
+def test_swiglu_rank_shards_reconstruct_weights_and_output(tp_size, dtype):
+    config = ModelConfig(
+        hidden_size=8,
+        intermediate_size=24,
+        num_attention_heads=8,
+        num_key_value_heads=8,
+    )
+    rng = np.random.default_rng(42)
+    weights = WeightDict(
+        {
+            "_attention_size": 8,
+            "_kv_attention_size": 8,
+            "_mlp_size": 24,
+            "embedding": rng.normal(size=(16, 8)).astype(dtype),
+            "layer.0.w_gate": rng.normal(scale=0.2, size=(8, 24)).astype(dtype),
+            "layer.0.w_up": rng.normal(scale=0.2, size=(8, 24)).astype(dtype),
+            "layer.0.w_down": rng.normal(scale=0.2, size=(24, 8)).astype(dtype),
+            "layer.0.post_attn_norm": np.ones(8, dtype=dtype),
+        }
+    )
+    original = {
+        key: value.copy() for key, value in weights.items() if isinstance(value, np.ndarray)
+    }
+    shards = [
+        shard_standard_decoder_weights(config, weights, ParallelConfig(tp_size, rank))
+        for rank in range(tp_size)
+    ]
+
+    for key, axis in (("w_gate", 1), ("w_up", 1), ("w_down", 0)):
+        full = weights[f"layer.0.{key}"]
+        expected_shape = list(full.shape)
+        expected_shape[axis] //= tp_size
+        for shard in shards:
+            part = shard[f"layer.0.{key}"]
+            assert part.shape == tuple(expected_shape)
+            assert part.dtype == dtype
+            assert part.flags.c_contiguous
+        np.testing.assert_array_equal(
+            np.concatenate([shard[f"layer.0.{key}"] for shard in shards], axis=axis),
+            full,
+        )
+
+    for rank, shard in enumerate(shards):
+        assert shard["_mlp_size"] == 24 // tp_size
+        assert isinstance(shard, WeightDict)
+        for key in ("embedding", "layer.0.post_attn_norm"):
+            np.testing.assert_array_equal(shard[key], weights[key])
+        if tp_size > 1:
+            assert shard["_tensor_parallel_rank"] == rank
+    for key, value in original.items():
+        np.testing.assert_array_equal(weights[key], value)
+    assert weights["_mlp_size"] == 24
+
+    inputs = rng.normal(size=(3, 8))
+
+    def evaluate(rank_weights):
+        gate = inputs @ rank_weights["layer.0.w_gate"].astype(np.float64)
+        up = inputs @ rank_weights["layer.0.w_up"].astype(np.float64)
+        return (gate / (1 + np.exp(-gate)) * up) @ rank_weights["layer.0.w_down"].astype(np.float64)
+
+    # Row-parallel down projections are summed by the runtime ALL_REDUCE.
+    np.testing.assert_allclose(
+        sum(evaluate(shard) for shard in shards),
+        evaluate(weights),
+        rtol=1e-12,
+        atol=1e-12,
+    )
diff --git a/families/qwen_vl/parallel.py b/families/qwen_vl/parallel.py
index 85bff94b95..8e6f6a0d31 100644
--- a/families/qwen_vl/parallel.py
+++ b/families/qwen_vl/parallel.py
@@ -82,9 +82,9 @@ def shard_standard_decoder_weights(
             sharded[key] = value
         elif key.endswith((".w_q", ".w_k", ".w_v", ".q_bias", ".k_bias", ".v_bias")):
             sharded[key] = _slice_last_dim(value, rank, tp_size)
-        elif key.endswith((".w_o", ".w_fc2")):
+        elif key.endswith((".w_o", ".w_fc2", ".w_down")):
             sharded[key] = _slice_first_dim(value, rank, tp_size)
-        elif key.endswith((".w_fc1", ".fc1_bias")):
+        elif key.endswith((".w_fc1", ".fc1_bias", ".w_gate", ".w_up")):
             sharded[key] = _slice_last_dim(value, rank, tp_size)
         else:
             sharded[key] = value
diff --git a/families/qwen_vl/tests/test_parallel_swiglu.py b/families/qwen_vl/tests/test_parallel_swiglu.py
new file mode 100644
index 0000000000..b20d7ec30b
--- /dev/null
+++ b/families/qwen_vl/tests/test_parallel_swiglu.py
@@ -0,0 +1,82 @@
+# SPDX-FileCopyrightText: Copyright (c) 2026 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+# SPDX-License-Identifier: Apache-2.0
+
+"""qwen_vl SwiGLU weight shards must reconstruct the unsharded computation."""
+
+import numpy as np
+import pytest
+
+from ..checkpoint_mapper import WeightDict
+from ..config import ModelConfig
+from ..parallel import ParallelConfig, shard_standard_decoder_weights
+
+
+@pytest.mark.parametrize("tp_size", [1, 2, 4, 8])
+@pytest.mark.parametrize("dtype", [np.float32, np.float16])
+def test_swiglu_rank_shards_reconstruct_weights_and_output(tp_size, dtype):
+    config = ModelConfig(
+        hidden_size=8,
+        intermediate_size=24,
+        num_attention_heads=8,
+        num_key_value_heads=8,
+    )
+    rng = np.random.default_rng(42)
+    weights = WeightDict(
+        {
+            "_attention_size": 8,
+            "_kv_attention_size": 8,
+            "_mlp_size": 24,
+            "embedding": rng.normal(size=(16, 8)).astype(dtype),
+            "layer.0.w_gate": rng.normal(scale=0.2, size=(8, 24)).astype(dtype),
+            "layer.0.w_up": rng.normal(scale=0.2, size=(8, 24)).astype(dtype),
+            "layer.0.w_down": rng.normal(scale=0.2, size=(24, 8)).astype(dtype),
+            "layer.0.post_attn_norm": np.ones(8, dtype=dtype),
+        }
+    )
+    original = {
+        key: value.copy() for key, value in weights.items() if isinstance(value, np.ndarray)
+    }
+    shards = [
+        shard_standard_decoder_weights(config, weights, ParallelConfig(tp_size, rank))
+        for rank in range(tp_size)
+    ]
+
+    for key, axis in (("w_gate", 1), ("w_up", 1), ("w_down", 0)):
+        full = weights[f"layer.0.{key}"]
+        expected_shape = list(full.shape)
+        expected_shape[axis] //= tp_size
+        for shard in shards:
+            part = shard[f"layer.0.{key}"]
+            assert part.shape == tuple(expected_shape)
+            assert part.dtype == dtype
+            assert part.flags.c_contiguous
+        np.testing.assert_array_equal(
+            np.concatenate([shard[f"layer.0.{key}"] for shard in shards], axis=axis),
+            full,
+        )
+
+    for rank, shard in enumerate(shards):
+        assert shard["_mlp_size"] == 24 // tp_size
+        assert isinstance(shard, WeightDict)
+        for key in ("embedding", "layer.0.post_attn_norm"):
+            np.testing.assert_array_equal(shard[key], weights[key])
+        if tp_size > 1:
+            assert shard["_tensor_parallel_rank"] == rank
+    for key, value in original.items():
+        np.testing.assert_array_equal(weights[key], value)
+    assert weights["_mlp_size"] == 24
+
+    inputs = rng.normal(size=(3, 8))
+
+    def evaluate(rank_weights):
+        gate = inputs @ rank_weights["layer.0.w_gate"].astype(np.float64)
+        up = inputs @ rank_weights["layer.0.w_up"].astype(np.float64)
+        return (gate / (1 + np.exp(-gate)) * up) @ rank_weights["layer.0.w_down"].astype(np.float64)
+
+    # Row-parallel down projections are summed by the runtime ALL_REDUCE.
+    np.testing.assert_allclose(
+        sum(evaluate(shard) for shard in shards),
+        evaluate(weights),
+        rtol=1e-12,
+        atol=1e-12,
+    )
diff --git a/families/stablelm/parallel.py b/families/stablelm/parallel.py
index 160f27582a..a5fd2e60f9 100644
--- a/families/stablelm/parallel.py
+++ b/families/stablelm/parallel.py
@@ -82,9 +82,9 @@ def shard_standard_decoder_weights(
             sharded[key] = value
         elif key.endswith((".w_q", ".w_k", ".w_v", ".q_bias", ".k_bias", ".v_bias")):
             sharded[key] = _slice_last_dim(value, rank, tp_size)
-        elif key.endswith((".w_o", ".w_fc2")):
+        elif key.endswith((".w_o", ".w_fc2", ".w_down")):
             sharded[key] = _slice_first_dim(value, rank, tp_size)
-        elif key.endswith((".w_fc1", ".fc1_bias")):
+        elif key.endswith((".w_fc1", ".fc1_bias", ".w_gate", ".w_up")):
             sharded[key] = _slice_last_dim(value, rank, tp_size)
         else:
             sharded[key] = value
diff --git a/families/stablelm/tests/test_parallel_swiglu.py b/families/stablelm/tests/test_parallel_swiglu.py
new file mode 100644
index 0000000000..e60483e0b3
--- /dev/null
+++ b/families/stablelm/tests/test_parallel_swiglu.py
@@ -0,0 +1,82 @@
+# SPDX-FileCopyrightText: Copyright (c) 2026 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+# SPDX-License-Identifier: Apache-2.0
+
+"""stablelm SwiGLU weight shards must reconstruct the unsharded computation."""
+
+import numpy as np
+import pytest
+
+from ..checkpoint_mapper import WeightDict
+from ..config import ModelConfig
+from ..parallel import ParallelConfig, shard_standard_decoder_weights
+
+
+@pytest.mark.parametrize("tp_size", [1, 2, 4, 8])
+@pytest.mark.parametrize("dtype", [np.float32, np.float16])
+def test_swiglu_rank_shards_reconstruct_weights_and_output(tp_size, dtype):
+    config = ModelConfig(
+        hidden_size=8,
+        intermediate_size=24,
+        num_attention_heads=8,
+        num_key_value_heads=8,
+    )
+    rng = np.random.default_rng(42)
+    weights = WeightDict(
+        {
+            "_attention_size": 8,
+            "_kv_attention_size": 8,
+            "_mlp_size": 24,
+            "embedding": rng.normal(size=(16, 8)).astype(dtype),
+            "layer.0.w_gate": rng.normal(scale=0.2, size=(8, 24)).astype(dtype),
+            "layer.0.w_up": rng.normal(scale=0.2, size=(8, 24)).astype(dtype),
+            "layer.0.w_down": rng.normal(scale=0.2, size=(24, 8)).astype(dtype),
+            "layer.0.post_attn_norm": np.ones(8, dtype=dtype),
+        }
+    )
+    original = {
+        key: value.copy() for key, value in weights.items() if isinstance(value, np.ndarray)
+    }
+    shards = [
+        shard_standard_decoder_weights(config, weights, ParallelConfig(tp_size, rank))
+        for rank in range(tp_size)
+    ]
+
+    for key, axis in (("w_gate", 1), ("w_up", 1), ("w_down", 0)):
+        full = weights[f"layer.0.{key}"]
+        expected_shape = list(full.shape)
+        expected_shape[axis] //= tp_size
+        for shard in shards:
+            part = shard[f"layer.0.{key}"]
+            assert part.shape == tuple(expected_shape)
+            assert part.dtype == dtype
+            assert part.flags.c_contiguous
+        np.testing.assert_array_equal(
+            np.concatenate([shard[f"layer.0.{key}"] for shard in shards], axis=axis),
+            full,
+        )
+
+    for rank, shard in enumerate(shards):
+        assert shard["_mlp_size"] == 24 // tp_size
+        assert isinstance(shard, WeightDict)
+        for key in ("embedding", "layer.0.post_attn_norm"):
+            np.testing.assert_array_equal(shard[key], weights[key])
+        if tp_size > 1:
+            assert shard["_tensor_parallel_rank"] == rank
+    for key, value in original.items():
+        np.testing.assert_array_equal(weights[key], value)
+    assert weights["_mlp_size"] == 24
+
+    inputs = rng.normal(size=(3, 8))
+
+    def evaluate(rank_weights):
+        gate = inputs @ rank_weights["layer.0.w_gate"].astype(np.float64)
+        up = inputs @ rank_weights["layer.0.w_up"].astype(np.float64)
+        return (gate / (1 + np.exp(-gate)) * up) @ rank_weights["layer.0.w_down"].astype(np.float64)
+
+    # Row-parallel down projections are summed by the runtime ALL_REDUCE.
+    np.testing.assert_allclose(
+        sum(evaluate(shard) for shard in shards),
+        evaluate(weights),
+        rtol=1e-12,
+        atol=1e-12,
+    )