diff --git a/deepmd/pt_expt/kernels/triton/sezm/sweep_tile_configs.py b/deepmd/pt_expt/kernels/triton/sezm/sweep_tile_configs.py
index f5da80d603..44c0a91aac 100644
--- a/deepmd/pt_expt/kernels/triton/sezm/sweep_tile_configs.py
+++ b/deepmd/pt_expt/kernels/triton/sezm/sweep_tile_configs.py
@@ -152,6 +152,7 @@
     _flash_bwd_block_kernel,
     _flash_bwd_kernel,
     _flash_bwd_op,
+    _rotation_strides,
 )
 from deepmd.pt_expt.kernels.triton.sezm.so2_stack_fp16x3 import (
     _mixing_stack_fp16x3_bwd_op,
@@ -1056,6 +1057,11 @@ def sweep_flash_bwd(
     grad_pre_gate = torch.randn(n_nodes, dim, c_wide, device=device)
     x_local = torch.randn(n_edge, n_focus, reduced_dim, cf, device=device)
     wigner_dt = _block_diag_wigner(n_edge, lmax, device)
+    # The backward kernels take the rotation layout (``PACKED``) and the
+    # Wigner strides explicitly, exactly as ``_launch_backward`` passes them;
+    # the sweep always builds a dense ``(E, D, D)`` Wigner, so ``packed`` is
+    # False here and the strides are the plain contiguous ones.
+    packed, dt_se, dt_sr, dt_sk = _rotation_strides(wigner_dt)
     rescale = torch.rand(dim, device=device, dtype=torch.float32) + 0.5
     alpha = torch.rand(n_edge, n_focus, n_head, device=device, dtype=torch.float32)
     dst = torch.randint(0, n_nodes, (n_edge,), device=device)
@@ -1086,6 +1092,7 @@ def launch_edge(warps: int, stages: int) -> tuple[torch.Tensor, ...]:
         gxl = torch.empty_like(x_local)
         gdt = torch.zeros_like(wigner_dt)
         gw = torch.empty_like(alpha)
+        _, gdt_se, gdt_sr, gdt_sk = _rotation_strides(gdt)
         wrap_triton(_flash_bwd_kernel.fn)[(n_edge,)](
             grad_pre_gate,
             x_local,
@@ -1105,9 +1112,9 @@ def launch_edge(warps: int, stages: int) -> tuple[torch.Tensor, ...]:
             x_local.stride(1),
             x_local.stride(2),
             x_local.stride(3),
-            wigner_dt.stride(0),
-            wigner_dt.stride(1),
-            wigner_dt.stride(2),
+            dt_se,
+            dt_sr,
+            dt_sk,
             alpha.stride(0),
             alpha.stride(1),
             alpha.stride(2),
@@ -1115,9 +1122,9 @@ def launch_edge(warps: int, stages: int) -> tuple[torch.Tensor, ...]:
             gxl.stride(1),
             gxl.stride(2),
             gxl.stride(3),
-            gdt.stride(0),
-            gdt.stride(1),
-            gdt.stride(2),
+            gdt_se,
+            gdt_sr,
+            gdt_sk,
             gw.stride(0),
             gw.stride(1),
             gw.stride(2),
@@ -1127,6 +1134,7 @@ def launch_edge(warps: int, stages: int) -> tuple[torch.Tensor, ...]:
             NFOCUS=n_focus,
             NHEAD=n_head,
             BLOCK_C=triton.next_power_of_2(c_wide),
+            PACKED=packed,
             num_warps=warps,
             num_stages=stages,
         )
@@ -1163,6 +1171,7 @@ def launch(block_e: int, warps: int, stages: int) -> tuple[torch.Tensor, ...]:
         gxl = torch.empty_like(x_local)
         gdt = torch.zeros_like(wigner_dt)
         gw = torch.empty_like(alpha)
+        _, gdt_se, gdt_sr, gdt_sk = _rotation_strides(gdt)
         wrap_triton(_flash_bwd_block_kernel)[(triton.cdiv(n_edge, block_e),)](
             grad_pre_gate,
             x_local,
@@ -1180,10 +1189,16 @@ def launch(block_e: int, warps: int, stages: int) -> tuple[torch.Tensor, ...]:
             x_local.stride(1),
             x_local.stride(2),
             x_local.stride(3),
+            dt_se,
+            dt_sr,
+            dt_sk,
             gxl.stride(0),
             gxl.stride(1),
             gxl.stride(2),
             gxl.stride(3),
+            gdt_se,
+            gdt_sr,
+            gdt_sk,
             L=lmax,
             CF=cf,
             CW=c_wide,
diff --git a/source/tests/pt/model/test_descriptor_sezm_triton.py b/source/tests/pt/model/test_descriptor_sezm_triton.py
index 796d1c8178..686bab70f3 100644
--- a/source/tests/pt/model/test_descriptor_sezm_triton.py
+++ b/source/tests/pt/model/test_descriptor_sezm_triton.py
@@ -1970,6 +1970,49 @@ def fake_flash_sweep(cf, lmax, **kwargs):
             )
         self.assertEqual(calls, [])
 
+    def test_tune_missing_configs_runs_the_real_flash_bwd_sweep(self):
+        """The flash-backward sweep launches the kernels it tunes.
+
+        The other tuning tests replace every sweep with a fake, so a sweep
+        launch that drifts from its kernel signature (as happened when the
+        ``PACKED`` layout flag and the Wigner strides were added to the
+        flash-attention backward kernels) is only caught by running the real
+        sweep once.  The built-in tables are hidden so the key is uncovered on
+        every GPU, and the edge count is kept tiny because the launch contract,
+        not the timing, is under test; the winners are therefore only checked
+        for membership in the candidate sets.
+        """
+        import itertools
+        from unittest import (
+            mock,
+        )
+
+        from deepmd.pt_expt.kernels.triton.sezm import (
+            sweep_tile_configs,
+        )
+
+        tc = self.tile_configs
+        specs = {"flash_bwd": sweep_tile_configs._SWEEP_SPECS["flash_bwd"]}
+        with (
+            mock.patch.object(tc, "_builtin_tables", return_value={}),
+            mock.patch.dict(sweep_tile_configs._SWEEP_SPECS, specs, clear=True),
+        ):
+            registered = sweep_tile_configs.tune_missing_configs(
+                [(32, 2, 1, 1)], level=2, device="cuda", n_edge=4096
+            )
+        key = (32, 2)
+        self.assertEqual(sorted(registered), ["flash_bwd_block", "flash_bwd_edge"])
+        self.assertIn(
+            registered["flash_bwd_edge"][key],
+            set(itertools.product((1, 2, 4), (1, 2))),
+        )
+        block = registered["flash_bwd_block"][key]
+        self.assertTrue(
+            block is None or block in set(sweep_tile_configs._EDGE_BLOCK_CANDIDATES)
+        )
+        self.assertTrue(tc.has_tile_config("flash_bwd_edge", key))
+        self.assertTrue(tc.has_tile_config("flash_bwd_block", key))
+
 
 if __name__ == "__main__":
     unittest.main()