diff --git a/tests/kernels/moe/test_gpt_oss_triton_kernels.py b/tests/kernels/moe/test_gpt_oss_triton_kernels.py
index 630ea2e3f..f659ec56c 100644
--- a/tests/kernels/moe/test_gpt_oss_triton_kernels.py
+++ b/tests/kernels/moe/test_gpt_oss_triton_kernels.py
@@ -21,12 +21,16 @@ from triton_kernels.numerics_details.mxfp import downcast_to_mxfp, upcast_from_m
 from triton_kernels.tensor import FP4, convert_layout, wrap_torch_tensor
 from triton_kernels.tensor_details import layout
 from triton_kernels.testing import assert_close
+from triton_kernels.topk import topk as topk_fn
 
 from vllm.model_executor.layers.fused_moe.config import mxfp4_w4a16_moe_quant_config
 from vllm.model_executor.layers.fused_moe.gpt_oss_triton_kernels_moe import (
+    legacy_routing,
+    make_routing_data,
     triton_kernel_moe_forward,
 )
 from vllm.utils.math_utils import round_up
+from vllm.utils.torch_utils import set_random_seed
 
 from .utils import shuffle_weight
 
@@ -355,3 +359,43 @@ def test_unit_shuffle():
     )
 
     assert_close(ref=out_ref, tri=out)
+
+
+@pytest.mark.parametrize("num_tokens", [2, 8, 64])
+@pytest.mark.parametrize("num_experts", [32, 128])
+@pytest.mark.parametrize("topk", [1, 4])
+@pytest.mark.parametrize("renormalize", [True, False])
+@pytest.mark.parametrize("dtype", [torch.bfloat16])
+def test_legacy_routing(
+    num_tokens: int, num_experts: int, topk: int, renormalize: bool, dtype: torch.dtype
+):
+    set_random_seed(0)
+    gating_output = torch.randn(num_tokens, num_experts, device="cuda", dtype=dtype)
+
+    sm_first = not renormalize
+    logits = gating_output
+    if sm_first:
+        logits = torch.softmax(logits, dim=-1)
+    sparse_logits = topk_fn(logits, topk, apply_softmax=not sm_first)
+    topk_ids = sparse_logits.indx.to(torch.long)
+    topk_weights = sparse_logits.vals
+    routing_data_ref, gather_indx_ref, scatter_indx_ref = make_routing_data(
+        topk_ids, topk_weights, num_experts
+    )
+
+    routing_data, gather_indx, scatter_indx = legacy_routing(
+        gating_output, topk, sm_first=sm_first
+    )
+
+    assert_close(
+        ref=gather_indx_ref.src_indx, tri=gather_indx.src_indx, maxtol=0, rmstol=0
+    )
+    assert_close(
+        ref=gather_indx_ref.dst_indx, tri=gather_indx.dst_indx, maxtol=0, rmstol=0
+    )
+    assert_close(
+        ref=scatter_indx_ref.src_indx, tri=scatter_indx.src_indx, maxtol=0, rmstol=0
+    )
+    assert_close(
+        ref=scatter_indx_ref.dst_indx, tri=scatter_indx.dst_indx, maxtol=0, rmstol=0
+    )
diff --git a/vllm/model_executor/layers/fused_moe/gpt_oss_triton_kernels_moe.py b/vllm/model_executor/layers/fused_moe/gpt_oss_triton_kernels_moe.py
index 82b0a21cb..5e7e7aa46 100644
--- a/vllm/model_executor/layers/fused_moe/gpt_oss_triton_kernels_moe.py
+++ b/vllm/model_executor/layers/fused_moe/gpt_oss_triton_kernels_moe.py
@@ -142,6 +142,33 @@ def legacy_routing_from_bitmatrix(
     return routing_data, gather_idx, scatter_idx
 
 
+def legacy_routing_from_sparsematrix(
+    sparse_logits: "SparseMatrix",
+    n_expts_tot: int,
+    n_expts_act: int,
+) -> tuple["RoutingData", "GatherIndx", "ScatterIndx"]:
+    """
+    Creates routing data from a SparseMatrix representation.
+    """
+    dispatch_indx = sparse_logits.mask_metadata.row_sorted_indx
+    combine_indx = sparse_logits.mask_metadata.col_sorted_indx
+    ragged_batch_metadata = make_ragged_tensor_metadata(
+        sparse_logits.mask_metadata.col_sum,
+        dispatch_indx.shape[0],
+    )
+    gate_scal = sparse_logits.vals.flatten()[combine_indx]
+    routing_data = RoutingData(
+        gate_scal,
+        ragged_batch_metadata.block_sizes,
+        n_expts_tot,
+        n_expts_act,
+        ragged_batch_metadata,
+    )
+    gather_idx = GatherIndx(combine_indx, dispatch_indx)
+    scatter_idx = ScatterIndx(dispatch_indx, combine_indx)
+    return routing_data, gather_idx, scatter_idx
+
+
 def legacy_routing(
     logits: torch.Tensor,
     n_expts_act: int,
@@ -158,10 +185,8 @@ def legacy_routing(
     if sm_first:
         logits = torch.softmax(logits, dim=-1)
     sparse_logits = topk(logits, n_expts_act, apply_softmax=not sm_first)
-    return legacy_routing_from_bitmatrix(
-        sparse_logits.mask,
-        sparse_logits.vals,
-        sparse_logits.indx,
+    return legacy_routing_from_sparsematrix(
+        sparse_logits,
         logits.shape[-1],
         n_expts_act,
     )