Add Qwen3.5 export support for 0.8B/2B/4B (#17800)

## Summary
- add initial Qwen3.5 model integration under examples/models/qwen3_5
- add HF->Meta checkpoint conversion for Qwen3.5 naming/layout
- wire Qwen3.5 model types into llama export config and registry
- add 0.8B, 2B, and 4B configs plus xnnpack fp32 export config
- add unit tests for Qwen3.5 attention path and weight conversion

## Test Plan
- PYTHONPATH=src pytest -q
examples/models/llama/tests/test_qwen3_5_attention.py
examples/models/qwen3_5/tests/test_convert_weights.py
- local smoke export succeeded for Qwen3.5-0.8B:
/tmp/qwen35_test/qwen3_5_0_8b_fp32_smoke.pte


cc @mergennachin @iseeyuan @lucylq @helunwencser @tarun292 @kimishpatel
@jackzhxng

Author: Phineas1500

examples/models/BUCK

@@ -29,6 +29,7 @@ fbcode_target(_kind = python_library,
         "//executorch/examples/models/gemma3:gemma3",  # @manual
         "//executorch/examples/models/qwen2_5:qwen2_5",  # @manual
         "//executorch/examples/models/qwen3:qwen3",  # @manual
+        "//executorch/examples/models/qwen3_5:qwen3_5",  # @manual
         "//executorch/examples/models/phi_4_mini:phi_4_mini",  # @manual
         "//executorch/examples/models/smollm2:smollm2",  # @manual
         "//executorch/examples/models/smollm3:smollm3",  # @manual

examples/models/llama/__init__.py

@@ -4,8 +4,17 @@
 # This source code is licensed under the BSD-style license found in the
 # LICENSE file in the root directory of this source tree.
 
-from .model import Llama2Model
+from typing import TYPE_CHECKING
 
-__all__ = [
-    Llama2Model,
-]
+if TYPE_CHECKING:
+    from .model import Llama2Model
+
+__all__ = ["Llama2Model"]
+
+
+def __getattr__(name):
+    if name == "Llama2Model":
+        from .model import Llama2Model
+
+        return Llama2Model
+    raise AttributeError(f"module '{__name__}' has no attribute '{name}'")

examples/models/llama/attention.py

@@ -7,7 +7,7 @@
 import torch.nn.functional as F
 from executorch.examples.models.llama.lora import LoRALinear
 from executorch.examples.models.llama.model_args import ModelArgs
-from executorch.examples.models.llama.norm import RMSNorm
+from executorch.examples.models.llama.norm import RMSNorm, RMSNormGated
 from executorch.examples.models.llama.rope import Rope
 
 
@@ -347,27 +347,35 @@ def __init__(
         self.attention_qkv_bias = args.attention_qkv_bias
         self.use_qk_norm = args.use_qk_norm
         self.qk_norm_before_rope = args.qk_norm_before_rope
+        self.use_q_gate = args.use_q_gate
         self.enable_dynamic_shape = args.enable_dynamic_shape
+        q_out_dim = self.n_heads * self.head_dim * (2 if self.use_q_gate else 1)
 
         if self.use_qk_norm:
             q_norm_dim = self.head_dim
             k_norm_dim = self.head_dim
-            self.q_norm_fn = RMSNorm(q_norm_dim, eps=args.norm_eps)
-            self.k_norm_fn = RMSNorm(k_norm_dim, eps=args.norm_eps)
+            self.q_norm_fn = RMSNorm(
+                q_norm_dim,
+                eps=args.norm_eps,
+                add_unit_offset=args.rms_norm_add_unit_offset,
+            )
+            self.k_norm_fn = RMSNorm(
+                k_norm_dim,
+                eps=args.norm_eps,
+                add_unit_offset=args.rms_norm_add_unit_offset,
+            )
 
         self.wq = (
             LoRALinear(
                 in_dim=args.dim,
-                out_dim=args.n_heads * args.head_dim,
+                out_dim=q_out_dim,
                 rank=args.r,
                 alpha=args.lora_alpha,
                 dropout=0.0,
                 use_bias=args.attention_qkv_bias,
             )
             if args.target_modules is not None and "q_proj" in args.target_modules
-            else nn.Linear(
-                self.dim, self.n_heads * self.head_dim, bias=self.attention_qkv_bias
-            )
+            else nn.Linear(self.dim, q_out_dim, bias=self.attention_qkv_bias)
         )
         self.wk = (
             LoRALinear(
@@ -452,10 +460,17 @@ def forward(
         input_pos = kwargs.get("input_pos")
         bsz, seqlen, _ = x.shape
 
-        # QKV
-        q, k, v = self.wq(x), self.wk(x), self.wv(x)
-        # We need view_copy elimination
-        q = q.view(bsz, seqlen, self.n_local_heads, self.head_dim)
+        if self.use_q_gate:
+            q_and_gate = self.wq(x).view(
+                bsz, seqlen, self.n_local_heads, self.head_dim * 2
+            )
+            q, gate = torch.chunk(q_and_gate, 2, dim=-1)
+            gate = gate.reshape(bsz, seqlen, -1)
+        else:
+            q = self.wq(x).view(bsz, seqlen, self.n_local_heads, self.head_dim)
+            gate = None
+
+        k, v = self.wk(x), self.wv(x)
         k = k.view(bsz, seqlen, self.n_local_kv_heads, self.head_dim)
         v = v.view(bsz, seqlen, self.n_local_kv_heads, self.head_dim)
 
@@ -492,6 +507,8 @@ def forward(
                     input_pos[0].item(), seqlen
                 )
             output = self.SDPA(input_pos, q, k, v, bsz, seqlen, attn_mask)
+            if gate is not None:
+                output = output * torch.sigmoid(gate)
             return self.wo(output), None
 
         # grouped multiquery attention: expand out keys and values
@@ -505,12 +522,234 @@ def forward(
         output = F.scaled_dot_product_attention(q, k, v, attn_mask=mask, dropout_p=0.0)
 
         output = output.transpose(1, 2).reshape(bsz, seqlen, -1)
+        if gate is not None:
+            output = output * torch.sigmoid(gate)
 
         output = self.wo(output)
 
         return output, None
 
 
+def _l2norm(x: torch.Tensor, dim: int = -1, eps: float = 1e-6) -> torch.Tensor:
+    inv_norm = torch.rsqrt((x * x).sum(dim=dim, keepdim=True) + eps)
+    return x * inv_norm
+
+
+@register_attention("gated_deltanet")
+class AttentionGatedDeltaNet(Attention):
+    """Qwen3.5 linear-attention (Gated DeltaNet) block with internal state."""
+
+    def __init__(
+        self,
+        args: ModelArgs,
+        layer_id: int,
+        rope: Rope,
+        **_kwargs: Any,
+    ):
+        super().__init__()
+        del rope  # DeltaNet layers do not use RoPE.
+
+        self.hidden_size = args.dim
+        self.max_batch_size = args.max_batch_size
+        self.layer_id = layer_id
+
+        assert args.linear_num_key_heads is not None
+        assert args.linear_num_value_heads is not None
+        assert args.linear_key_head_dim is not None
+        assert args.linear_value_head_dim is not None
+
+        self.num_k_heads = args.linear_num_key_heads
+        self.num_v_heads = args.linear_num_value_heads
+        self.head_k_dim = args.linear_key_head_dim
+        self.head_v_dim = args.linear_value_head_dim
+        self.key_dim = self.head_k_dim * self.num_k_heads
+        self.value_dim = self.head_v_dim * self.num_v_heads
+        self.conv_kernel_size = args.linear_conv_kernel_dim
+
+        assert (
+            self.num_v_heads % self.num_k_heads == 0
+        ), "linear_num_value_heads must be divisible by linear_num_key_heads."
+        self.head_repeat = self.num_v_heads // self.num_k_heads
+
+        self.conv_dim = self.key_dim * 2 + self.value_dim
+        self.in_proj_qkv = nn.Linear(self.hidden_size, self.conv_dim, bias=False)
+        self.in_proj_z = nn.Linear(self.hidden_size, self.value_dim, bias=False)
+        self.in_proj_b = nn.Linear(self.hidden_size, self.num_v_heads, bias=False)
+        self.in_proj_a = nn.Linear(self.hidden_size, self.num_v_heads, bias=False)
+
+        self.conv1d = nn.Conv1d(
+            in_channels=self.conv_dim,
+            out_channels=self.conv_dim,
+            kernel_size=self.conv_kernel_size,
+            groups=self.conv_dim,
+            bias=False,
+            padding=0,
+        )
+
+        self.dt_bias = nn.Parameter(torch.ones(self.num_v_heads))
+        A = torch.empty(self.num_v_heads).uniform_(0, 16)
+        self.A_log = nn.Parameter(torch.log(A))
+        self.norm = RMSNormGated(self.head_v_dim, eps=args.norm_eps)
+        self.out_proj = nn.Linear(self.value_dim, self.hidden_size, bias=False)
+
+        self.register_buffer(
+            "conv_state",
+            torch.zeros(
+                self.max_batch_size,
+                self.conv_dim,
+                self.conv_kernel_size,
+                dtype=torch.float32,
+                device="cpu",
+            ),
+        )
+        self.register_buffer(
+            "recurrent_state",
+            torch.zeros(
+                self.max_batch_size,
+                self.num_v_heads,
+                self.head_k_dim,
+                self.head_v_dim,
+                dtype=torch.float32,
+                device="cpu",
+            ),
+        )
+
+    def _maybe_reset_state(
+        self, input_pos: Optional[torch.Tensor], batch_size: int
+    ) -> None:
+        if input_pos is None:
+            self.conv_state[:batch_size].zero_()
+            self.recurrent_state[:batch_size].zero_()
+            return
+        reset = (input_pos[0] == 0).to(self.conv_state.dtype)
+        keep = 1.0 - reset
+        self.conv_state[:batch_size].mul_(keep)
+        self.recurrent_state[:batch_size].mul_(keep)
+
+    def _apply_causal_conv(self, mixed_qkv: torch.Tensor) -> torch.Tensor:
+        # mixed_qkv: (batch, seq_len, conv_dim)
+        batch_size, seq_len, _ = mixed_qkv.shape
+        mixed_qkv = mixed_qkv.transpose(1, 2)
+        state_len = self.conv_state.shape[-1]
+        hidden_states_new = torch.cat([self.conv_state[:batch_size], mixed_qkv], dim=-1)
+        new_conv_state = hidden_states_new[:, :, -state_len:]
+        with torch.no_grad():
+            self.conv_state[:batch_size].copy_(new_conv_state.to(self.conv_state.dtype))
+        out = F.conv1d(
+            hidden_states_new,
+            self.conv1d.weight,
+            self.conv1d.bias,
+            padding=0,
+            groups=self.conv_dim,
+        )
+        out = F.silu(out[:, :, -seq_len:]).to(mixed_qkv.dtype)
+        return out.transpose(1, 2).contiguous()
+
+    def _recurrent_gated_delta_rule(
+        self,
+        query: torch.Tensor,
+        key: torch.Tensor,
+        value: torch.Tensor,
+        g: torch.Tensor,
+        beta: torch.Tensor,
+    ) -> torch.Tensor:
+        # query/key/value: (batch, seq_len, num_heads, head_dim)
+        # g/beta: (batch, seq_len, num_heads)
+        initial_dtype = query.dtype
+        query = _l2norm(query, dim=-1, eps=1e-6)
+        key = _l2norm(key, dim=-1, eps=1e-6)
+        query, key, value, beta, g = [
+            x.transpose(1, 2).contiguous().to(torch.float32)
+            for x in (query, key, value, beta, g)
+        ]
+
+        batch_size, num_heads, sequence_length, k_head_dim = key.shape
+        v_head_dim = value.shape[-1]
+        scale = 1.0 / (query.shape[-1] ** 0.5)
+        query = query * scale
+
+        core_attn_out = torch.zeros(
+            batch_size,
+            num_heads,
+            sequence_length,
+            v_head_dim,
+            device=value.device,
+            dtype=value.dtype,
+        )
+        last_recurrent_state = self.recurrent_state[:batch_size].to(value.dtype)
+
+        for i in range(sequence_length):
+            q_t = query[:, :, i]
+            k_t = key[:, :, i]
+            v_t = value[:, :, i]
+            g_t = g[:, :, i].exp().unsqueeze(-1).unsqueeze(-1)
+            beta_t = beta[:, :, i].unsqueeze(-1)
+
+            last_recurrent_state = last_recurrent_state * g_t
+            kv_mem = (last_recurrent_state * k_t.unsqueeze(-1)).sum(dim=-2)
+            delta = (v_t - kv_mem) * beta_t
+            last_recurrent_state = last_recurrent_state + k_t.unsqueeze(
+                -1
+            ) * delta.unsqueeze(-2)
+            core_attn_out[:, :, i] = (last_recurrent_state * q_t.unsqueeze(-1)).sum(
+                dim=-2
+            )
+
+        with torch.no_grad():
+            self.recurrent_state[:batch_size].copy_(
+                last_recurrent_state.to(self.recurrent_state.dtype)
+            )
+
+        return core_attn_out.transpose(1, 2).contiguous().to(initial_dtype)
+
+    def forward(
+        self,
+        x: torch.Tensor,
+        freqs_cos: torch.Tensor,
+        freqs_sin: torch.Tensor,
+        **kwargs: ForwardOptions,
+    ) -> Tuple[torch.Tensor, Optional[Any]]:
+        del freqs_cos
+        del freqs_sin
+        input_pos = kwargs.get("input_pos")
+        batch_size, seq_len, _ = x.shape
+        assert (
+            batch_size <= self.max_batch_size
+        ), f"batch_size ({batch_size}) exceeds max_batch_size ({self.max_batch_size})"
+
+        self._maybe_reset_state(input_pos, batch_size)
+
+        mixed_qkv = self.in_proj_qkv(x)
+        z = self.in_proj_z(x).reshape(batch_size, seq_len, -1, self.head_v_dim)
+        b = self.in_proj_b(x)
+        a = self.in_proj_a(x)
+
+        mixed_qkv = self._apply_causal_conv(mixed_qkv)
+        query, key, value = torch.split(
+            mixed_qkv,
+            [self.key_dim, self.key_dim, self.value_dim],
+            dim=-1,
+        )
+        query = query.reshape(batch_size, seq_len, -1, self.head_k_dim)
+        key = key.reshape(batch_size, seq_len, -1, self.head_k_dim)
+        value = value.reshape(batch_size, seq_len, -1, self.head_v_dim)
+
+        if self.head_repeat > 1:
+            query = query.repeat_interleave(self.head_repeat, dim=2)
+            key = key.repeat_interleave(self.head_repeat, dim=2)
+
+        beta = b.sigmoid()
+        g = -self.A_log.float().exp() * F.softplus(a.float() + self.dt_bias)
+        core_attn_out = self._recurrent_gated_delta_rule(query, key, value, g, beta)
+
+        core_attn_out = core_attn_out.reshape(-1, self.head_v_dim)
+        z = z.reshape(-1, self.head_v_dim)
+        core_attn_out = self.norm(core_attn_out, z)
+        core_attn_out = core_attn_out.reshape(batch_size, seq_len, -1)
+
+        return self.out_proj(core_attn_out), None
+
+
 @register_attention("skip")
 class AttentionSkip(Attention):
     def __init__(self, *args, **kwargs):

examples/models/llama/export_llama_lib.py

@@ -107,6 +107,9 @@
     "qwen3_0_6b",
     "qwen3_1_7b",
     "qwen3_4b",
+    "qwen3_5_0_8b",
+    "qwen3_5_2b",
+    "qwen3_5_4b",
     "phi_4_mini",
     "smollm2",
     "lfm2_350m",  # hybrid
@@ -124,6 +127,9 @@
     "qwen3_0_6b": "Qwen/Qwen3-0.6B",
     "qwen3_1_7b": "Qwen/Qwen3-1.7B",
     "qwen3_4b": "Qwen/Qwen3-4B",
+    "qwen3_5_0_8b": "Qwen/Qwen3.5-0.8B",
+    "qwen3_5_2b": "Qwen/Qwen3.5-2B",
+    "qwen3_5_4b": "Qwen/Qwen3.5-4B",
     "lfm2_350m": "LiquidAI/LFM2-350M",
     "lfm2_700m": "LiquidAI/LFM2-700M",
     "lfm2_1_2b": "LiquidAI/LFM2-1.2B",
@@ -622,7 +628,7 @@ def canonical_path(path: Union[str, Path], *, dir: bool = False) -> str:
         return return_val
 
 
-def export_llama(
+def export_llama(  # noqa: C901
     export_options: Union[argparse.Namespace, LlmConfig, DictConfig],
 ) -> str:
     if isinstance(export_options, argparse.Namespace):
@@ -645,6 +651,8 @@ def export_llama(
         repo_id = HUGGING_FACE_REPO_IDS[model_name]
         if model_name.startswith("qwen2_5"):
             from executorch.examples.models.qwen2_5 import convert_weights
+        elif model_name.startswith("qwen3_5"):
+            from executorch.examples.models.qwen3_5 import convert_weights
         elif model_name.startswith("qwen3"):
             from executorch.examples.models.qwen3 import convert_weights
         elif model_name == "phi_4_mini":