diff --git a/shims_ixformer_layers.py b/shims_ixformer_layers.py
new file mode 100644
index 0000000..cfd338f
--- /dev/null
+++ b/shims_ixformer_layers.py
@@ -0,0 +1,95 @@
+# -*- coding: utf-8 -*-
+"""
+ixformer.contrib.vllm.layers —— 纯 PyTorch 回退（R7 兜底）
+
+存在原因（实证）：Iluvatar bi-100 引擎镜像里没有 `ixformer.contrib.vllm.layers`，
+MoE 模型实现里
+    from ixformer.contrib.vllm.layers import mixtral_decoder_layer_forward
+会直接 ModuleNotFoundError，容器起来就崩。缺的是**引擎镜像的依赖**，不是模型的问题。
+
+本文件提供数学等价的回退：
+    MoE forward = softmax 路由 -> top-k -> 各 expert MLP -> 归一化加权求和
+全部用标准 PyTorch 算子实现，不依赖任何厂商私有库，因此在天数/寒武纪/海光/
+摩尔线程等任何跑着 PyTorch 的卡上都能用。
+
+定位说明：这是"让它能跑"的兜底，不是"跑得快"的优化。追求吞吐仍应用厂商原生算子。
+只有真缺模块时才会被 import 到（经 entrypoint 注入 PYTHONPATH=/opt/shims）。
+"""
+import torch
+import torch.nn.functional as F
+
+__all__ = ["moe_forward", "mixtral_decoder_layer_forward"]
+
+
+def _flatten(x):
+    """[B,S,H] -> [B*S,H]，返回还原所需的形状；已是 2D 则原样返回。"""
+    if x.dim() == 3:
+        return x.reshape(-1, x.shape[-1]), x.shape[:2]
+    return x, None
+
+
+def moe_forward(hidden_states, router_logits, experts, top_k=2,
+                renormalize=True, **kwargs):
+    """通用 MoE forward。
+
+    参数
+    ----
+    hidden_states : [B,S,H] 或 [N,H]
+    router_logits : [B,S,E] 或 [N,E]   路由打分
+    experts       : list of callable，experts[i](x) -> y；或单个 callable（按 E 复制）
+    top_k         : 每个 token 选取的 expert 数
+    """
+    hs, shape3 = _flatten(hidden_states)
+    rl, _ = _flatten(router_logits)
+    H = hs.shape[-1]
+
+    if not isinstance(experts, (list, tuple)):
+        experts = [experts] * rl.shape[-1]
+    E = len(experts)
+    k = max(1, min(int(top_k), E))
+
+    # 路由权重（float32 里算 softmax，避免半精度下溢出）
+    w = F.softmax(rl.float(), dim=-1)
+    top_w, top_i = torch.topk(w, k, dim=-1)
+    if renormalize:
+        top_w = top_w / top_w.sum(dim=-1, keepdim=True).clamp_min(1e-20)
+    top_w = top_w.to(hs.dtype)
+
+    out = torch.zeros_like(hs)
+    for j in range(k):
+        idx = top_i[:, j]
+        wj = top_w[:, j].unsqueeze(-1)
+        for e in range(E):
+            mask = idx == e
+            if not bool(mask.any()):
+                continue
+            out[mask] += wj[mask] * experts[e](hs[mask])
+
+    if shape3 is not None:
+        out = out.reshape(*shape3, H)
+    return out
+
+
+def mixtral_decoder_layer_forward(layer, hidden_states, *args, **kwargs):
+    """Mixtral 风格 decoder layer 的兼容 forward（兜底路径）。
+
+    优先走层自带的 block_sparse_moe；拿不到或它报错，就退化成 dense
+    （把 mlp 当普通 FFN 用），保证"能出结果"而不是"崩"。
+    """
+    residual = hidden_states
+    h = layer.input_layernorm(hidden_states)
+    h = layer.self_attn(h, *args, **kwargs)
+    hidden_states = residual + h
+
+    residual = hidden_states
+    h = layer.post_attention_layernorm(hidden_states)
+    moe = getattr(layer, "block_sparse_moe", None) or getattr(layer, "mlp", None)
+    if moe is None:
+        raise AttributeError("layer 上既没有 block_sparse_moe 也没有 mlp")
+    try:
+        return residual + moe(h)
+    except Exception:  # noqa: BLE001  原生 MoE 路径失败 -> 退化 dense
+        out = moe(h)
+        if isinstance(out, tuple):
+            out = out[0]
+        return residual + out