diff --git a/scripts/paddle_all_test_cases.sh b/scripts/paddle_all_test_cases.sh
index 7cb473c62f..5b98d13121 100755
--- a/scripts/paddle_all_test_cases.sh
+++ b/scripts/paddle_all_test_cases.sh
@@ -59,3 +59,12 @@ python3 -m pytest tests/utils/test_topk.py --ignore-glob="*test_topk_determinist
 # Skips are environment-level (cuDNN version), not Paddle compat issues.
 # The 4 passing validation tests confirm grouped_mm works cleanly in Paddle compat mode.
 python3 -m pytest tests/grouped_mm/ --tb=no -q
+
+# tests/model_optimizations: 690 PASS, 4164 SKIP (2026-05-19)
+# Fix: torch.sort monkey-patch in conftest.py (§51)
+#   - Paddle compat torch.sort returns values-only Tensor; wraps (values, indices) with _SortResult
+#   - Paddle compat torch.sort does not accept dim= kwarg; patch passes it as positional arg
+#   - MUST use stable=True in argsort for correct bfloat16 tie-breaking semantics
+# All 690 passed tests cover test_dsv3_fused_routing.py and test_dsv3_router_gemm.py
+# 4164 skips are environment-level (SM architecture/hardware constraints), not Paddle compat issues.
+python3.12 -m pytest tests/model_optimizations/ --tb=no -q
diff --git a/tests/model_optimizations/conftest.py b/tests/model_optimizations/conftest.py
new file mode 100644
index 0000000000..1fda696e94
--- /dev/null
+++ b/tests/model_optimizations/conftest.py
@@ -0,0 +1,167 @@
+# Paddle compat patches for tests/model_optimizations/
+# Reuses patterns from tests/utils/conftest.py plus additional fixes.
+#
+# §44/§45: assert_close bfloat16/float16 — paddle.isclose not registered
+# §45: Walk __cause__/__context__ to find inner paddle error
+# §46: torch.equal() returns Tensor not bool
+# §47: tensor.multiply(scalar) — Paddle requires Tensor args
+# §48: tensor.clamp_min/clamp_max — missing on Paddle Tensors
+# §51: torch.sort() in Paddle compat returns only values (no indices);
+#      also does not accept dim= keyword argument (uses axis=).
+#      Fix: monkey-patch to accept dim= kwarg and return proper (values, indices) tuple.
+import functools
+import torch
+
+
+# ── §44/§45: assert_close bfloat16/float16 fix ──────────────────────────────
+
+_orig_assert_close = torch.testing.assert_close
+
+
+def _is_paddle_isclose_dtype_error(exc):
+    seen = set()
+    cur = exc
+    while cur is not None and id(cur) not in seen:
+        seen.add(id(cur))
+        msg = str(cur)
+        if ("bfloat16" in msg or "float16" in msg) and (
+            "isclose" in msg or "NotFound" in msg
+        ):
+            return True
+        cur = getattr(cur, "__cause__", None) or getattr(cur, "__context__", None)
+    return False
+
+
+def _manual_allclose(actual, expected, rtol, atol):
+    import numpy as np
+
+    a = actual.float().detach().cpu().numpy()
+    e = expected.float().detach().cpu().numpy()
+    diff = np.abs(a - e)
+    tol = atol + rtol * np.abs(e)
+    if not np.all(diff <= tol):
+        max_diff = float(diff.max())
+        max_loc = np.unravel_index(diff.argmax(), diff.shape)
+        raise AssertionError(
+            f"Tensors are not close!\n"
+            f"Max absolute diff: {max_diff:.6f} at {max_loc}\n"
+            f"actual[{max_loc}]={float(a[max_loc]):.6f}, "
+            f"expected[{max_loc}]={float(e[max_loc]):.6f}\n"
+            f"rtol={rtol}, atol={atol}"
+        )
+
+
+@functools.wraps(_orig_assert_close)
+def _paddle_compat_assert_close(actual, expected, *args, **kwargs):
+    try:
+        _orig_assert_close(actual, expected, *args, **kwargs)
+    except RuntimeError as e:
+        if _is_paddle_isclose_dtype_error(e):
+            rtol = kwargs.get("rtol")
+            atol = kwargs.get("atol")
+            dt = actual.dtype if isinstance(actual, torch.Tensor) else torch.float32
+            if rtol is None:
+                rtol = (
+                    0.016
+                    if dt == torch.bfloat16
+                    else (0.001 if dt == torch.float16 else 1.3e-6)
+                )
+            if atol is None:
+                atol = 1e-5
+            _manual_allclose(actual, expected, rtol=rtol, atol=atol)
+        else:
+            raise
+
+
+torch.testing.assert_close = _paddle_compat_assert_close
+
+
+# ── §46: torch.equal returns Tensor instead of bool ─────────────────────────
+
+_orig_equal = torch.equal
+
+
+@functools.wraps(_orig_equal)
+def _paddle_compat_equal(input, other):
+    if isinstance(input, torch.Tensor) and isinstance(other, torch.Tensor):
+        if input.shape != other.shape:
+            return False
+    result = _orig_equal(input, other)
+    if isinstance(result, torch.Tensor):
+        return bool(result.all().item()) if result.numel() > 1 else bool(result.item())
+    return bool(result)
+
+
+torch.equal = _paddle_compat_equal
+
+
+# ── §47: tensor.multiply(scalar) ─────────────────────────────────────────────
+
+_orig_tensor_multiply = torch.Tensor.multiply
+
+
+def _paddle_compat_tensor_multiply(self, other):
+    if isinstance(other, (int, float)):
+        other = torch.tensor(other, dtype=self.dtype, device=self.device)
+    return _orig_tensor_multiply(self, other)
+
+
+torch.Tensor.multiply = _paddle_compat_tensor_multiply
+
+
+# ── §48: clamp_min / clamp_max ───────────────────────────────────────────────
+
+torch.Tensor.clamp_min = lambda self, v: torch.clamp(self, min=v)
+torch.Tensor.clamp_max = lambda self, v: torch.clamp(self, max=v)
+
+
+# ── §51: torch.sort — dim= kwarg unsupported; returns values-only Tensor ─────
+# Paddle's sort uses axis= not dim=, and returns only the sorted values tensor.
+# Fix: accept dim= kwarg (pass as positional), and wrap result to return
+# a proper (values, indices) pair when Paddle returns only values.
+
+_orig_sort = torch.sort
+
+
+class _SortResult:
+    """Mimics torch.return_types.sort for Paddle compat."""
+
+    __slots__ = ("values", "indices")
+
+    def __init__(self, values, indices):
+        self.values = values
+        self.indices = indices
+
+    def __iter__(self):
+        return iter((self.values, self.indices))
+
+    def __getitem__(self, i):
+        return (self.values, self.indices)[i]
+
+    def __len__(self):
+        return 2
+
+
+def _paddle_compat_sort(input, dim=-1, descending=False, stable=False, *, out=None):
+    # Paddle sort does not accept dim= as keyword; pass as positional.
+    # Also ignores stable= (Paddle sort is always stable).
+    try:
+        result = _orig_sort(input, dim, descending=descending)
+    except TypeError:
+        # Fallback: try without dim (1-D case)
+        result = _orig_sort(input, descending=descending)
+
+    if isinstance(result, torch.Tensor):
+        # Paddle returned values-only tensor; compute indices via argsort.
+        # Use stable=True to match PyTorch's default stable sort behavior.
+        try:
+            indices = torch.argsort(input, dim, descending=descending, stable=True)
+        except TypeError:
+            indices = torch.argsort(input, descending=descending, stable=True)
+        return _SortResult(result, indices)
+
+    # Already a proper (values, indices) pair
+    return result
+
+
+torch.sort = _paddle_compat_sort