# coding=utf-8
# Copyright 2025 The LLAMA4 and HuggingFace Inc. team. All rights reserved.
#
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
import math
from dataclasses import dataclass
from typing import Callable, Optional, Union

import torch
import torch.nn as nn
import torch.nn.functional as F

from transformers.models.llama4.configuration_llama4 import Llama4VisionConfig

from ...activations import ACT2FN
from ...cache_utils import Cache, DynamicCache
from ...generation import GenerationMixin
from ...integrations import use_kernel_forward_from_hub
from ...masking_utils import create_causal_mask, create_chunked_causal_mask
from ...modeling_flash_attention_utils import FlashAttentionKwargs
from ...modeling_layers import GradientCheckpointingLayer
from ...modeling_outputs import BaseModelOutput, BaseModelOutputWithPast, CausalLMOutputWithPast, ModelOutput
from ...modeling_rope_utils import ROPE_INIT_FUNCTIONS, dynamic_rope_update
from ...modeling_utils import ALL_ATTENTION_FUNCTIONS, PreTrainedModel
from ...processing_utils import Unpack
from ...utils import TransformersKwargs, auto_docstring, can_return_tuple, logging
from ...utils.generic import check_model_inputs
from .configuration_llama4 import Llama4Config, Llama4TextConfig


logger = logging.get_logger(__name__)


class Llama4TextExperts(nn.Module):
    def __init__(self, config: Llama4TextConfig):
        super().__init__()
        self.num_experts = config.num_local_experts
        self.intermediate_size = config.intermediate_size
        self.hidden_size = config.hidden_size
        self.expert_dim = self.intermediate_size
        self.gate_up_proj = nn.Parameter(torch.empty(self.num_experts, self.hidden_size, 2 * self.expert_dim))
        self.down_proj = nn.Parameter(torch.empty((self.num_experts, self.expert_dim, self.hidden_size)))
        self.act_fn = ACT2FN[config.hidden_act]

    def forward(self, hidden_states: torch.Tensor) -> torch.Tensor:
        """
        This should really not be run on a single machine, as we are reaching compute bound:
        - the inputs are expected to be "sorted" per expert already.
        - the weights are viewed with another dim, to match num_expert, 1, shape * num_tokens, shape

        Args:
            hidden_states (torch.Tensor): (batch_size * token_num, hidden_size)
            selected_experts (torch.Tensor): (batch_size * token_num, top_k)
            routing_weights (torch.Tensor): (batch_size * token_num, top_k)
        Returns:
            torch.Tensor
        """
        hidden_states = hidden_states.view(self.gate_up_proj.shape[0], -1, self.hidden_size)
        gate_up = torch.bmm(hidden_states, self.gate_up_proj)
        gate, up = gate_up.chunk(2, dim=-1)  # not supported for DTensors
        next_states = torch.bmm((up * self.act_fn(gate)), self.down_proj)
        next_states = next_states.view(-1, self.hidden_size)
        return next_states


# Phi3MLP
class Llama4TextMLP(nn.Module):
    def __init__(self, config, intermediate_size=None):
        super().__init__()

        if intermediate_size is None:
            intermediate_size = config.intermediate_size

        self.config = config
        self.gate_proj = nn.Linear(config.hidden_size, intermediate_size, bias=False)
        self.up_proj = nn.Linear(config.hidden_size, intermediate_size, bias=False)
        self.down_proj = nn.Linear(intermediate_size, config.hidden_size, bias=False)
        self.activation_fn = ACT2FN[config.hidden_act]

    def forward(self, x):
        down_proj = self.activation_fn(self.gate_proj(x)) * self.up_proj(x)
        return self.down_proj(down_proj)


class Llama4TextL2Norm(torch.nn.Module):
    def __init__(self, eps: float = 1e-6):
        super().__init__()
        self.eps = eps

    def _norm(self, x):
        return x * torch.rsqrt(x.pow(2).mean(-1, keepdim=True) + self.eps)

    def forward(self, x):
        return self._norm(x.float()).type_as(x)

    def extra_repr(self):
        return f"eps={self.eps}"


class Llama4TextRMSNorm(nn.Module):
    def __init__(self, hidden_size, eps=1e-5):
        """
        Llama4RMSNorm is equivalent to T5LayerNorm
        """
        super().__init__()
        self.eps = eps
        self.weight = nn.Parameter(torch.ones(hidden_size))

    def _norm(self, x):
        return x * torch.rsqrt(x.pow(2).mean(-1, keepdim=True) + self.eps)

    def forward(self, x):
        output = self._norm(x.float()).type_as(x)
        return output * self.weight

    def extra_repr(self):
        return f"{tuple(self.weight.shape)}, eps={self.eps}"


class Llama4Router(nn.Linear):
    def __init__(self, config):
        super().__init__(config.hidden_size, config.num_local_experts, bias=False)
        self.num_experts = config.num_local_experts
        self.top_k = config.num_experts_per_tok

    def forward(self, hidden_states):
        router_logits = super().forward(hidden_states)
        router_top_value, router_indices = torch.topk(router_logits, self.top_k, dim=1)
        router_scores = torch.full_like(router_logits, float("-inf")).scatter_(1, router_indices, router_top_value)
        router_scores = torch.nn.functional.sigmoid(router_scores.float()).to(router_scores.dtype)
        return router_scores, router_logits


@use_kernel_forward_from_hub("Llama4TextMoe")
class Llama4TextMoe(nn.Module):
    def __init__(self, config):
        super().__init__()
        self.top_k = config.num_experts_per_tok
        self.hidden_dim = config.hidden_size
        self.num_experts = config.num_local_experts
        self.experts = Llama4TextExperts(config)
        self.router = Llama4Router(config)
        self.shared_expert = Llama4TextMLP(config)

    def forward(self, hidden_states):
        hidden_states = hidden_states.reshape(-1, self.hidden_dim)
        router_scores, router_logits = self.router(hidden_states)
        routed_in = hidden_states.repeat(router_scores.shape[1], 1)
        routed_in = routed_in * router_scores.reshape(-1, 1)
        routed_out = self.experts(routed_in)
        out = self.shared_expert(hidden_states)
        out.add_(routed_out.reshape(router_scores.shape[1], -1, routed_out.shape[-1]).sum(dim=0))
        return out, router_logits


class Llama4TextRotaryEmbedding(nn.Module):
    def __init__(self, config: Llama4TextConfig, device=None):
        super().__init__()
        # BC: "rope_type" was originally "type"
        self.rope_type = "llama3" if config.rope_scaling is not None else "default"

        self.max_seq_len_cached = config.max_position_embeddings
        self.original_max_seq_len = config.max_position_embeddings

        self.config = config
        self.rope_init_fn = ROPE_INIT_FUNCTIONS[self.rope_type]

        inv_freq, self.attention_scaling = self.rope_init_fn(self.config, device)
        self.register_buffer("inv_freq", inv_freq, persistent=False)
        self.original_inv_freq = self.inv_freq

    @torch.no_grad()
    @dynamic_rope_update  # power user: used with advanced RoPE types (e.g. dynamic rope)
    def forward(self, x, position_ids):
        inv_freq_expanded = self.inv_freq[None, :, None].float().expand(position_ids.shape[0], -1, 1)
        position_ids_expanded = position_ids[:, None, :].float()

        device_type = x.device.type if isinstance(x.device.type, str) and x.device.type != "mps" else "cpu"
        with torch.autocast(device_type=device_type, enabled=False):  # Force float32
            freqs = (inv_freq_expanded.to(x.device) @ position_ids_expanded).transpose(1, 2)
            freqs_cis = torch.polar(torch.ones_like(freqs), freqs)  # Convert to complex representation
            freqs_cis = freqs_cis * self.attention_scaling

        return freqs_cis


def apply_rotary_emb(
    xq: torch.Tensor,
    xk: torch.Tensor,
    freqs_cis: torch.Tensor,
) -> tuple[torch.Tensor, torch.Tensor]:
    xq_ = torch.view_as_complex(xq.float().reshape(*xq.shape[:-1], -1, 2))
    xk_ = torch.view_as_complex(xk.float().reshape(*xk.shape[:-1], -1, 2))
    xq_out = torch.view_as_real(xq_ * freqs_cis[:, :, None, :]).flatten(3)
    xk_out = torch.view_as_real(xk_ * freqs_cis[:, :, None, :]).flatten(3)
    return xq_out.type_as(xq), xk_out.type_as(xk)


def repeat_kv(hidden_states: torch.Tensor, n_rep: int) -> torch.Tensor:
    """
    This is the equivalent of torch.repeat_interleave(x, dim=1, repeats=n_rep). The hidden states go from (batch,
    num_key_value_heads, seqlen, head_dim) to (batch, num_attention_heads, seqlen, head_dim)
    """
    batch, num_key_value_heads, slen, head_dim = hidden_states.shape
    if n_rep == 1:
        return hidden_states
    hidden_states = hidden_states[:, :, None, :, :].expand(batch, num_key_value_heads, n_rep, slen, head_dim)
    return hidden_states.reshape(batch, num_key_value_heads * n_rep, slen, head_dim)


# Adapted from transformers.models.llama.modeling_llama.eager_attention_forward -> llama4 doesn't cast attn weights to fp32
def eager_attention_forward(
    module: nn.Module,
    query: torch.Tensor,
    key: torch.Tensor,
    value: torch.Tensor,
    attention_mask: Optional[torch.Tensor],
    scaling: float,
    dropout: float = 0.0,
    **kwargs,
):
    key_states = repeat_kv(key, module.num_key_value_groups)
    value_states = repeat_kv(value, module.num_key_value_groups)

    attn_weights = torch.matmul(query, key_states.transpose(2, 3)) * scaling
    if attention_mask is not None:
        causal_mask = attention_mask[:, :, :, : key_states.shape[-2]]
        attn_weights = attn_weights + causal_mask

    attn_weights = nn.functional.softmax(attn_weights, dim=-1)
    attn_weights = nn.functional.dropout(attn_weights, p=dropout, training=module.training)
    attn_output = torch.matmul(attn_weights, value_states)
    attn_output = attn_output.transpose(1, 2).contiguous()

    return attn_output, attn_weights


# Adapted from transformers.models.llama.modeling_llama.eager_attention_forward -> llama4 doesn't cast attn weights to fp32
def vision_eager_attention_forward(
    module: nn.Module,
    query: torch.Tensor,
    key: torch.Tensor,
    value: torch.Tensor,
    attention_mask: Optional[torch.Tensor],
    scaling: float,
    dropout: float = 0.0,
    **kwargs,
):
    key_states = repeat_kv(key, module.num_key_value_groups)
    value_states = repeat_kv(value, module.num_key_value_groups)

    attn_weights = torch.matmul(query, key_states.transpose(2, 3)) * module.head_dim**-0.5
    if attention_mask is not None:
        causal_mask = attention_mask[:, :, :, : key_states.shape[-2]]
        attn_weights = attn_weights + causal_mask

    attn_weights = nn.functional.softmax(attn_weights, dim=-1)
    attn_weights = nn.functional.dropout(attn_weights, p=dropout, training=module.training)
    attn_output = torch.matmul(attn_weights, value_states)
    attn_output = attn_output.transpose(1, 2).contiguous()

    return attn_output, attn_weights


class Llama4TextAttention(nn.Module):
    """Multi-headed attention from 'Attention Is All You Need' paper"""

    def __init__(self, config: Llama4TextConfig, layer_idx):
        super().__init__()
        self.config = config
        self.layer_idx = layer_idx
        self.head_dim = getattr(config, "head_dim", config.hidden_size // config.num_attention_heads)
        self.num_attention_heads = config.num_attention_heads
        self.num_key_value_groups = config.num_attention_heads // config.num_key_value_heads
        self.num_key_value_heads = config.num_key_value_heads
        self.scaling = self.head_dim**-0.5
        self.attn_scale = config.attn_scale
        self.floor_scale = config.floor_scale
        self.attn_temperature_tuning = config.attn_temperature_tuning
        self.attention_dropout = config.attention_dropout
        self.is_causal = True
        self.use_rope = config.no_rope_layers[layer_idx]
        self.q_proj = nn.Linear(
            config.hidden_size, config.num_attention_heads * self.head_dim, bias=config.attention_bias
        )
        self.k_proj = nn.Linear(
            config.hidden_size, config.num_key_value_heads * self.head_dim, bias=config.attention_bias
        )
        self.v_proj = nn.Linear(
            config.hidden_size, config.num_key_value_heads * self.head_dim, bias=config.attention_bias
        )
        self.o_proj = nn.Linear(
            config.num_attention_heads * self.head_dim, config.hidden_size, bias=config.attention_bias
        )
        if self.config.use_qk_norm and self.use_rope:
            self.qk_norm = Llama4TextL2Norm(config.rms_norm_eps)

    def forward(
        self,
        hidden_states: torch.Tensor,
        position_embeddings: tuple[torch.Tensor, torch.Tensor],
        attention_mask: Optional[torch.Tensor],
        past_key_value: Optional[Cache] = None,
        cache_position: Optional[torch.LongTensor] = None,
        **kwargs: Unpack[FlashAttentionKwargs],
    ) -> tuple[torch.Tensor, Optional[torch.Tensor], Optional[tuple[torch.Tensor]]]:
        input_shape = hidden_states.shape[:-1]
        hidden_shape = (*input_shape, -1, self.head_dim)

        query_states = self.q_proj(hidden_states).view(hidden_shape)
        key_states = self.k_proj(hidden_states).view(*input_shape, -1, self.head_dim)
        value_states = self.v_proj(hidden_states).view(hidden_shape).transpose(1, 2)

        if self.use_rope:  # the 16E model skips rope for long context on certain layers
            query_states, key_states = apply_rotary_emb(
                query_states, key_states, position_embeddings.to(query_states.device)
            )

        if hasattr(self, "qk_norm"):  # the 128E model does not use qk_norm
            query_states = self.qk_norm(query_states)
            key_states = self.qk_norm(key_states)

        # Use temperature tuning from https://huggingface.co/papers/2501.19399) to NoROPE layers
        if self.attn_temperature_tuning and not self.use_rope:
            attn_scales = (
                torch.log(torch.floor((cache_position.float() + 1.0) / self.floor_scale) + 1.0) * self.attn_scale + 1.0
            )
            attn_scales = attn_scales.view((1, input_shape[-1], 1, 1)).expand((*input_shape, 1, 1))  # batch size > 1
            query_states = (query_states * attn_scales).to(query_states.dtype)

        query_states = query_states.transpose(1, 2)
        key_states = key_states.transpose(1, 2)

        if past_key_value is not None:
            # sin and cos are specific to RoPE models; cache_position needed for the static cache
            cache_kwargs = {"cache_position": cache_position}
            key_states, value_states = past_key_value.update(key_states, value_states, self.layer_idx, cache_kwargs)

        attention_interface: Callable = eager_attention_forward
        if self.config._attn_implementation != "eager":
            attention_interface = ALL_ATTENTION_FUNCTIONS[self.config._attn_implementation]
        attn_output, attn_weights = attention_interface(
            self,
            query_states,
            key_states,
            value_states,
            attention_mask,
            dropout=0.0 if not self.training else self.attention_dropout,
            scaling=self.scaling,
            **kwargs,
        )

        attn_output = attn_output.reshape(*input_shape, -1).contiguous()
        attn_output = self.o_proj(attn_output)
        return attn_output, attn_weights


class Llama4TextDecoderLayer(GradientCheckpointingLayer):
    def __init__(self, config, layer_idx):
        super().__init__()
        self.hidden_size = config.hidden_size
        self.layer_idx = layer_idx
        self.attention_type = config.layer_types[layer_idx]
        self.self_attn = Llama4TextAttention(config, layer_idx)
        self.is_moe_layer = layer_idx in config.moe_layers
        if self.is_moe_layer:  # the 128E model interleaves dense / sparse
            self.feed_forward = Llama4TextMoe(config)
        else:
            self.feed_forward = Llama4TextMLP(config, intermediate_size=config.intermediate_size_mlp)

        self.input_layernorm = Llama4TextRMSNorm(config.hidden_size, eps=config.rms_norm_eps)
        self.post_attention_layernorm = Llama4TextRMSNorm(config.hidden_size, eps=config.rms_norm_eps)

    def forward(
        self,
        hidden_states: torch.Tensor,
        attention_mask: Optional[torch.Tensor] = None,
        position_ids: Optional[torch.LongTensor] = None,
        past_key_value: Optional[tuple[torch.Tensor]] = None,
        use_cache: Optional[bool] = False,
        cache_position: Optional[torch.LongTensor] = None,
        position_embeddings: Optional[tuple[torch.Tensor, torch.Tensor]] = None,  # necessary, but kept here for BC
        **kwargs: Unpack[FlashAttentionKwargs],
    ) -> tuple[torch.FloatTensor, Optional[tuple[torch.FloatTensor, torch.FloatTensor]]]:
        residual = hidden_states

        hidden_states = self.input_layernorm(hidden_states)

        # Self Attention
        attention_states, _ = self.self_attn(
            hidden_states=hidden_states,
            position_embeddings=position_embeddings,
            attention_mask=attention_mask,
            past_key_value=past_key_value,
            use_cache=use_cache,
            cache_position=cache_position,
            **kwargs,
        )
        hidden_states = residual + attention_states

        # Fully Connected
        residual = hidden_states
        hidden_states = self.post_attention_layernorm(hidden_states)
        hidden_states = self.feed_forward(hidden_states)
        if self.is_moe_layer:
            hidden_states, _ = hidden_states
        hidden_states = residual + hidden_states.view(residual.shape)
        return hidden_states


@auto_docstring
class Llama4PreTrainedModel(PreTrainedModel):
    config: Llama4Config
    supports_gradient_checkpointing = True
    _skip_keys_device_placement = ["past_key_values"]
    _supports_flash_attn = False
    _supports_sdpa = True
    _supports_flex_attn = True

    _can_compile_fullgraph = True
    _supports_attention_backend = True

    def _init_weights(self, module):
        std = (
            self.config.initializer_range
            if hasattr(self.config, "initializer_range")
            else self.config.text_config.initializer_range
        )
        if isinstance(module, nn.Linear):
            module.weight.data.normal_(mean=0.0, std=std)
            if module.bias is not None:
                module.bias.data.zero_()
        elif isinstance(module, nn.Embedding):
            module.weight.data.normal_(mean=0.0, std=std)
            if module.padding_idx is not None:
                module.weight.data[module.padding_idx].zero_()
        elif isinstance(module, nn.LayerNorm):
            module.weight.data.fill_(1.0)
            module.bias.data.zero_()
        elif isinstance(module, Llama4TextRMSNorm):
            module.weight.data.fill_(1.0)
        elif isinstance(module, Llama4TextExperts):
            module.gate_up_proj.data.normal_(mean=0.0, std=std)
            module.down_proj.data.normal_(mean=0.0, std=std)
        elif isinstance(module, Llama4VisionModel):
            module.class_embedding.data.normal_(std=module.scale)
            module.positional_embedding_vlm.data.normal_(std=module.scale)


@auto_docstring
class Llama4TextModel(Llama4PreTrainedModel):
    _no_split_modules = ["Llama4TextDecoderLayer"]
    base_model_prefix = "model"
    config: Llama4TextConfig
    _can_record_outputs = {
        "attentions": Llama4TextAttention,
        "hidden_states": Llama4TextDecoderLayer,
        "router_logits": Llama4TextMoe,
    }

    def __init__(self, config: Llama4TextConfig):
        super().__init__(config)
        self.padding_idx = config.pad_token_id
        self.vocab_size = config.vocab_size

        self.embed_tokens = nn.Embedding(config.vocab_size, config.hidden_size, self.padding_idx)
        self.layers = nn.ModuleList(
            [Llama4TextDecoderLayer(config, layer_idx) for layer_idx in range(config.num_hidden_layers)]
        )
        self.norm = Llama4TextRMSNorm(config.hidden_size, eps=config.rms_norm_eps)
        self.rotary_emb = Llama4TextRotaryEmbedding(config=config)
        self.gradient_checkpointing = False

        # Initialize weights and apply final processing
        self.post_init()

    @check_model_inputs
    @auto_docstring
    def forward(
        self,
        input_ids: torch.LongTensor = None,
        attention_mask: Optional[torch.Tensor] = None,
        position_ids: Optional[torch.LongTensor] = None,
        past_key_values: Optional[Cache] = None,
        inputs_embeds: Optional[torch.FloatTensor] = None,
        use_cache: Optional[bool] = None,
        cache_position: Optional[torch.LongTensor] = None,
        **kwargs: Unpack[TransformersKwargs],
    ) -> Union[tuple, BaseModelOutputWithPast]:
        if (input_ids is None) ^ (inputs_embeds is not None):
            raise ValueError("You must specify exactly one of input_ids or inputs_embeds")

        if inputs_embeds is None:
            inputs_embeds = self.embed_tokens(input_ids.to(self.embed_tokens.weight.device))

        if use_cache and past_key_values is None:
            past_key_values = DynamicCache()

        if cache_position is None:
            past_seen_tokens = past_key_values.get_seq_length() if past_key_values is not None else 0
            cache_position = torch.arange(
                past_seen_tokens, past_seen_tokens + inputs_embeds.shape[1], device=inputs_embeds.device
            )

        if position_ids is None:
            position_ids = cache_position.unsqueeze(0)

        # It may already have been prepared by e.g. `generate`
        if not isinstance(causal_mask_mapping := attention_mask, dict):
            # Prepare mask arguments
            mask_kwargs = {
                "config": self.config,
                "input_embeds": inputs_embeds,
                "attention_mask": attention_mask,
                "cache_position": cache_position,
                "past_key_values": past_key_values,
                "position_ids": position_ids,
            }
            # Create the masks
            causal_mask_mapping = {
                "full_attention": create_causal_mask(**mask_kwargs),
                "chunked_attention": create_chunked_causal_mask(**mask_kwargs),
            }

        hidden_states = inputs_embeds

        # create position embeddings to be shared across the decoder layers
        freq_cis = self.rotary_emb(hidden_states, position_ids)

        for decoder_layer in self.layers[: self.config.num_hidden_layers]:
            hidden_states = decoder_layer(
                hidden_states,
                attention_mask=causal_mask_mapping[decoder_layer.attention_type],
                position_ids=position_ids,
                past_key_value=past_key_values,
                use_cache=use_cache,
                cache_position=cache_position,
                position_embeddings=freq_cis,
                **kwargs,
            )
        hidden_states = self.norm(hidden_states)

        return BaseModelOutputWithPast(
            last_hidden_state=hidden_states,
            past_key_values=past_key_values if use_cache else None,
        )


class Llama4ForCausalLM(Llama4PreTrainedModel, GenerationMixin):
    _no_split_modules = ["Llama4TextDecoderLayer"]
    base_model_prefix = "language_model"
    _tied_weights_keys = ["lm_head.weight"]
    _tp_plan = {"lm_head": "colwise_rep"}
    config: Llama4TextConfig

    def __init__(self, config: Llama4TextConfig):
        super().__init__(config)
        self.model = Llama4TextModel(config)
        self.vocab_size = config.vocab_size
        self.lm_head = nn.Linear(config.hidden_size, config.vocab_size, bias=False)

        # Initialize weights and apply final processing
        self.post_init()

    def set_decoder(self, decoder):
        self.model = decoder

    def get_decoder(self):
        return self.model

    @can_return_tuple
    @auto_docstring
    def forward(
        self,
        input_ids: torch.LongTensor = None,
        attention_mask: Optional[torch.Tensor] = None,
        position_ids: Optional[torch.LongTensor] = None,
        past_key_values: Optional[Union[Cache, list[torch.FloatTensor]]] = None,
        inputs_embeds: Optional[torch.FloatTensor] = None,
        labels: Optional[torch.LongTensor] = None,
        use_cache: Optional[bool] = None,
        cache_position: Optional[torch.LongTensor] = None,
        logits_to_keep: Union[int, torch.Tensor] = 0,
        **kwargs: Unpack[TransformersKwargs],
    ) -> Union[tuple, CausalLMOutputWithPast]:
        r"""
        labels (`torch.LongTensor` of shape `(batch_size, sequence_length)`, *optional*):
            Labels for computing the masked language modeling loss. Indices should either be in `[0, ...,
            config.vocab_size]` or -100 (see `input_ids` docstring). Tokens with indices set to `-100` are ignored
            (masked), the loss is only computed for the tokens with labels in `[0, ..., config.vocab_size]`.

        Example:

        ```python
        >>> from transformers import AutoTokenizer, Llama4ForCausalLM

        >>> model = Llama4ForCausalLM.from_pretrained("meta-llama4/Llama4-2-7b-hf")
        >>> tokenizer = AutoTokenizer.from_pretrained("meta-llama4/Llama4-2-7b-hf")

        >>> prompt = "Hey, are you conscious? Can you talk to me?"
        >>> inputs = tokenizer(prompt, return_tensors="pt")

        >>> # Generate
        >>> generate_ids = model.generate(inputs.input_ids, max_length=30)
        >>> tokenizer.batch_decode(generate_ids, skip_special_tokens=True, clean_up_tokenization_spaces=False)[0]
        "Hey, are you conscious? Can you talk to me?\nI'm not conscious, but I can talk to you."
        ```"""
        outputs = self.model(
            input_ids=input_ids,
            attention_mask=attention_mask,
            position_ids=position_ids,
            past_key_values=past_key_values,
            inputs_embeds=inputs_embeds,
            use_cache=use_cache,
            cache_position=cache_position,
            **kwargs,
        )

        hidden_states = outputs[0]
        # Only compute necessary logits, and do not upcast them to float if we are not computing the loss
        slice_indices = slice(-logits_to_keep, None) if isinstance(logits_to_keep, int) else logits_to_keep
        logits = self.lm_head(hidden_states[:, slice_indices, :])
        loss = None
        if labels is not None:
            loss = self.loss_function(logits=logits, labels=labels, vocab_size=self.config.vocab_size, **kwargs)

        return CausalLMOutputWithPast(
            loss=loss,
            logits=logits,
            past_key_values=outputs.past_key_values,
            hidden_states=outputs.hidden_states,
            attentions=outputs.attentions,
        )


@dataclass
@auto_docstring(
    custom_intro="""
    Base class for Llava causal language model (or autoregressive) outputs.
    """
)
class Llama4CausalLMOutputWithPast(ModelOutput):
    r"""
    loss (`torch.FloatTensor` of shape `(1,)`, *optional*, returned when `labels` is provided):
        Language modeling loss (for next-token prediction).
    logits (`torch.FloatTensor` of shape `(batch_size, sequence_length, config.vocab_size)`):
        Prediction scores of the language modeling head (scores for each vocabulary token before SoftMax).
    past_key_values (`Cache`, *optional*, returned when `use_cache=True` is passed or when `config.use_cache=True`):
        Tuple of `tuple(torch.FloatTensor)` of length `config.n_layers`, with each tuple having 2 tensors of shape
        `(batch_size, num_heads, sequence_length, embed_size_per_head)`)

        Contains pre-computed hidden-states (key and values in the self-attention blocks) that can be used (see
        `past_key_values` input) to speed up sequential decoding.
    image_hidden_states (`torch.FloatTensor`, *optional*):
        A `torch.FloatTensor` of size (batch_size, num_images, sequence_length, hidden_size)`.
        image_hidden_states of the model produced by the vision encoder and after projecting the last hidden state.
    """

    loss: Optional[torch.FloatTensor] = None
    logits: torch.FloatTensor = None
    past_key_values: Optional[list[torch.FloatTensor]] = None
    hidden_states: Optional[tuple[torch.FloatTensor]] = None
    attentions: Optional[tuple[torch.FloatTensor]] = None
    image_hidden_states: Optional[torch.FloatTensor] = None


class Llama4VisionMLP2(torch.nn.Module):
    def __init__(self, config):
        super().__init__()
        self.hidden_size = config.hidden_size
        self.intermediate_size = config.intermediate_size
        self.fc1 = nn.Linear(self.intermediate_size, config.projector_input_dim, bias=False)
        self.fc2 = nn.Linear(config.projector_output_dim, config.projector_output_dim, bias=False)
        self.activation_fn = nn.GELU()  # ACT2FN[config.hidden_act]
        self.dropout = config.projector_dropout

    def forward(self, hidden_states):
        hidden_states = self.fc1(hidden_states)
        hidden_states = self.activation_fn(hidden_states)
        hidden_states = F.dropout(hidden_states, p=self.dropout, training=self.training)
        return self.activation_fn(self.fc2(hidden_states))


class Llama4MultiModalProjector(nn.Module):
    def __init__(self, config):
        super().__init__()
        self.linear_1 = nn.Linear(
            config.vision_config.vision_output_dim,
            config.text_config.hidden_size,
            bias=False,
        )

    def forward(self, image_features):
        hidden_states = self.linear_1(image_features)
        return hidden_states


def pixel_shuffle(input_tensor, shuffle_ratio):
    # input_tensor: [batch_size, num_patches, channels]
    batch_size, num_patches, channels = input_tensor.shape
    patch_size = int(math.sqrt(num_patches))

    input_tensor = input_tensor.view(batch_size, patch_size, patch_size, -1)
    batch_size, height, width, channels = input_tensor.size()

    reshaped_tensor = input_tensor.view(batch_size, height, int(width * shuffle_ratio), int(channels / shuffle_ratio))
    reshaped_tensor = reshaped_tensor.permute(0, 2, 1, 3).contiguous()

    reshaped_tensor = reshaped_tensor.view(
        batch_size, int(height * shuffle_ratio), int(width * shuffle_ratio), int(channels / (shuffle_ratio**2))
    )
    reshaped_tensor = reshaped_tensor.permute(0, 2, 1, 3).contiguous()

    output_tensor = reshaped_tensor.view(batch_size, -1, reshaped_tensor.shape[-1])
    return output_tensor


class Llama4VisionPixelShuffleMLP(nn.Module):
    def __init__(self, config):
        super().__init__()
        self.pixel_shuffle_ratio = config.pixel_shuffle_ratio
        self.inner_dim = int(config.projector_input_dim // (self.pixel_shuffle_ratio**2))
        self.output_dim = config.projector_output_dim
        self.mlp = Llama4VisionMLP2(config)

    def forward(self, encoded_patches: torch.Tensor) -> torch.Tensor:
        encoded_patches = pixel_shuffle(encoded_patches, self.pixel_shuffle_ratio)
        return self.mlp(encoded_patches)


# TODO there is a different RoPE for vision encoder, defined as below
def reshape_for_broadcast(freqs_ci: torch.Tensor, query: torch.Tensor):
    ndim = query.ndim
    shape = [d if i == 1 or i == ndim - 1 else 1 for i, d in enumerate(query.shape)]
    return freqs_ci.view(*shape)


def vision_apply_rotary_emb(
    query: torch.Tensor,
    key: torch.Tensor,
    freqs_ci: torch.Tensor,
) -> tuple[torch.Tensor, torch.Tensor]:
    query_ = torch.view_as_complex(query.float().reshape(*query.shape[:-1], -1, 2))
    key_ = torch.view_as_complex(key.float().reshape(*key.shape[:-1], -1, 2))
    freqs_ci = reshape_for_broadcast(freqs_ci=freqs_ci, query=query_)  # freqs_ci[:,:,None,:]
    freqs_ci = freqs_ci.to(query_.device)
    query_out = torch.view_as_real(query_ * freqs_ci).flatten(3)
    key_out = torch.view_as_real(key_ * freqs_ci).flatten(3)
    return query_out.type_as(query), key_out.type_as(key)  # but this drops to 8e-3


class Llama4VisionAttention(nn.Module):
    def __init__(self, config: Llama4VisionConfig):
        super().__init__()
        self.config = config
        self.embed_dim = config.hidden_size
        self.num_heads = config.num_attention_heads
        self.head_dim = config.hidden_size // config.num_attention_heads
        self.num_key_value_groups = 1
        self.attention_dropout = config.attention_dropout
        self.scaling = self.head_dim**-0.5

        self.q_proj = nn.Linear(self.embed_dim, self.num_heads * self.head_dim, bias=True)
        self.k_proj = nn.Linear(self.embed_dim, self.num_heads * self.head_dim, bias=True)
        self.v_proj = nn.Linear(self.embed_dim, self.num_heads * self.head_dim, bias=True)
        self.o_proj = nn.Linear(self.num_heads * self.head_dim, self.embed_dim, bias=True)

    def forward(
        self,
        hidden_states: torch.Tensor,
        freqs_ci: torch.Tensor,
        attention_mask: Optional[torch.Tensor] = None,
        past_key_value: Optional[Cache] = None,
        **kwargs: Unpack[FlashAttentionKwargs],
    ) -> tuple[torch.Tensor, Optional[torch.Tensor], Optional[tuple[torch.Tensor]]]:
        input_shape = hidden_states.shape[:-1]
        hidden_shape = (*input_shape, -1, self.head_dim)

        query_states = self.q_proj(hidden_states).view(hidden_shape)
        key_states = self.k_proj(hidden_states).view(hidden_shape)
        value_states = self.v_proj(hidden_states).view(hidden_shape)

        query_states, key_states = vision_apply_rotary_emb(query_states, key_states, freqs_ci=freqs_ci)

        query_states = query_states.transpose(1, 2)
        key_states = key_states.transpose(1, 2)
        value_states = value_states.transpose(1, 2)

        attention_interface: Callable = vision_eager_attention_forward
        # flex disable because breaks on TP 8, embed is 88 not power of 2
        if self.config._attn_implementation not in ["eager", "flex_attention"]:
            attention_interface = ALL_ATTENTION_FUNCTIONS[self.config._attn_implementation]

        attn_output, attn_weights = attention_interface(
            self,
            query_states,
            key_states,
            value_states,
            None,
            dropout=0.0 if not self.training else self.attention_dropout,
            scaling=None,  # TODO Might be enforced here for TP compatibility as scaling is not just sqrt(head_dim)
            is_causal=False,  # HAS TO BE ENFORCED
            **kwargs,
        )

        attn_output = attn_output.reshape(*input_shape, -1).contiguous()
        attn_output = self.o_proj(attn_output)
        return attn_output, attn_weights


class Llama4VisionMLP(nn.Module):
    def __init__(self, config):
        super().__init__()
        self.config = config
        self.activation_fn = nn.GELU()  # ACT2FN[config.hidden_act]
        self.fc1 = nn.Linear(config.hidden_size, config.intermediate_size, bias=True)
        self.fc2 = nn.Linear(config.intermediate_size, config.hidden_size, bias=True)

    def forward(self, hidden_states: torch.Tensor) -> torch.Tensor:
        hidden_states = self.fc1(hidden_states)
        hidden_states = self.activation_fn(hidden_states)
        hidden_states = self.fc2(hidden_states)
        return hidden_states


class Llama4VisionEncoderLayer(GradientCheckpointingLayer):
    def __init__(self, config: Llama4VisionConfig):
        super().__init__()
        self.hidden_size = config.hidden_size

        self.self_attn = Llama4VisionAttention(config)
        self.mlp = Llama4VisionMLP(config)

        self.input_layernorm = nn.LayerNorm(config.hidden_size)
        self.post_attention_layernorm = nn.LayerNorm(config.hidden_size)

    def forward(
        self,
        hidden_state: torch.Tensor,
        freqs_ci: torch.Tensor,
        attention_mask: Optional[torch.Tensor] = None,
        output_attentions: Optional[bool] = None,
    ):
        # Self Attention
        residual = hidden_state

        hidden_state = self.input_layernorm(hidden_state)

        hidden_state, attn_weights = self.self_attn(
            hidden_state,
            freqs_ci=freqs_ci,
            attention_mask=attention_mask,
        )
        hidden_state = residual + hidden_state

        # Feed forward
        residual = hidden_state
        hidden_state = self.post_attention_layernorm(hidden_state)
        hidden_state = self.mlp(hidden_state)
        hidden_state = residual + hidden_state

        outputs = (hidden_state,)

        if output_attentions:
            outputs += (attn_weights,)

        return outputs


class Llama4VisionEncoder(nn.Module):
    """
    Transformer encoder consisting of `config.num_hidden_layers` self attention layers. Each layer is a
    [`Llama4VisionEncoderLayer`].

    Args:
        config: Llama4VisionConfig
    """

    def __init__(self, config: Llama4VisionConfig):
        super().__init__()
        self.config = config
        self.layers = nn.ModuleList([Llama4VisionEncoderLayer(config) for _ in range(config.num_hidden_layers)])
        self.gradient_checkpointing = False
        self.config = config

    def forward(
        self,
        hidden_states: torch.Tensor,
        freqs_ci: torch.Tensor,  # TODO move this to an attribute instead of keeping it around
        attention_mask: Optional[torch.Tensor] = None,
        output_attentions: Optional[bool] = None,
        output_hidden_states: Optional[bool] = None,
        return_dict: Optional[bool] = None,
    ) -> Union[tuple, BaseModelOutput]:
        r"""
        Args:
            inputs_embeds (`torch.FloatTensor` of shape `(batch_size, sequence_length, hidden_size)`):
                Optionally, instead of passing `input_ids` you can choose to directly pass an embedded representation.
                This is useful if you want more control over how to convert `input_ids` indices into associated vectors
                than the model's internal embedding lookup matrix.
            attention_mask (`torch.Tensor` of shape `(batch_size, sequence_length)`, *optional*):
                Mask to avoid performing attention on padding token indices. Mask values selected in `[0, 1]`:

                - 1 for tokens that are **not masked**,
                - 0 for tokens that are **masked**.

                [What are attention masks?](../glossary#attention-mask)
            output_attentions (`bool`, *optional*):
                Whether or not to return the attentions tensors of all attention layers. See `attentions` under
                returned tensors for more detail.
            output_hidden_states (`bool`, *optional*):
                Whether or not to return the hidden states of all layers. See `hidden_states` under returned tensors
                for more detail.
            return_dict (`bool`, *optional*):
                Whether or not to return a [`~utils.ModelOutput`] instead of a plain tuple.
        """
        output_attentions = output_attentions if output_attentions is not None else self.config.output_attentions
        output_hidden_states = (
            output_hidden_states if output_hidden_states is not None else self.config.output_hidden_states
        )
        return_dict = return_dict if return_dict is not None else self.config.use_return_dict

        encoder_states = () if output_hidden_states else None
        all_attentions = () if output_attentions else None

        for encoder_layer in self.layers:
            if output_hidden_states:
                encoder_states = encoder_states + (hidden_states,)

            layer_outputs = encoder_layer(
                hidden_state=hidden_states,
                attention_mask=attention_mask,
                output_attentions=output_attentions,
                freqs_ci=freqs_ci,
            )

            if output_attentions:
                all_attentions = all_attentions + (layer_outputs[1],)

            hidden_states = layer_outputs[0]

        if output_hidden_states:
            encoder_states = encoder_states + (hidden_states,)

        if not return_dict:
            return tuple(v for v in [hidden_states, encoder_states, all_attentions] if v is not None)
        return BaseModelOutput(
            last_hidden_state=hidden_states, hidden_states=encoder_states, attentions=all_attentions
        )


class Llama4UnfoldConvolution(nn.Module):
    def __init__(self, config):
        super().__init__()
        kernel_size = config.patch_size
        if isinstance(kernel_size, int):
            kernel_size = (kernel_size, kernel_size)
        self.unfold = torch.nn.Unfold(kernel_size=kernel_size, stride=config.patch_size)
        self.linear = nn.Linear(
            config.num_channels * kernel_size[0] * kernel_size[1],
            config.hidden_size,
            bias=False,
        )

    def forward(self, hidden_states: torch.Tensor) -> torch.Tensor:
        hidden_states = self.unfold(hidden_states)
        hidden_states = hidden_states.permute(0, 2, 1)
        hidden_states = self.linear(hidden_states)
        return hidden_states


class Llama4VisionRotaryEmbedding(nn.Module):
    def __init__(self, config):
        super().__init__()
        idx = config.image_size // config.patch_size
        img_idx = torch.arange(idx**2, dtype=torch.int32).reshape(idx**2, 1)
        img_idx = torch.cat([img_idx, img_idx[:1]], dim=0)
        img_idx[-1, -1] = -2  # ID_CLS_TOKEN
        frequencies_x = img_idx % idx  # get the coordinates of the 2d matrix along x
        frequencies_y = img_idx // idx  # get the coordinates of the 2d matrix along y
        freq_dim = config.hidden_size // config.num_attention_heads // 2
        rope_freq = 1.0 / (config.rope_theta ** (torch.arange(0, freq_dim, 2)[: (freq_dim // 2)].float() / freq_dim))
        freqs_x = ((frequencies_x + 1)[..., None] * rope_freq[None, None, :]).repeat_interleave(2, dim=-1)
        freqs_y = ((frequencies_y + 1)[..., None] * rope_freq[None, None, :]).repeat_interleave(2, dim=-1)
        freqs = torch.cat([freqs_x, freqs_y], dim=-1).float().contiguous()[..., ::2]
        freqs = freqs.masked_fill(img_idx.reshape(-1, 1, 1) < 0, 0)
        freq_cis = torch.view_as_complex(torch.stack([torch.cos(freqs), torch.sin(freqs)], dim=-1))
        self.freqs_ci = freq_cis  # idx**2, idx**2, idx * 2

    def forward(self, hidden_states):
        return self.freqs_ci.to(hidden_states.device)


class Llama4VisionModel(Llama4PreTrainedModel):
    base_model_prefix = "vision_model"
    _no_split_modules = ["Llama4VisionEncoderLayer"]
    config: Llama4VisionConfig

    def __init__(self, config: Llama4VisionConfig):
        super().__init__(config)
        self.image_size = config.image_size
        self.patch_size = config.patch_size
        self.hidden_size = config.hidden_size
        self.num_channels = config.num_channels

        self.num_patches = (self.image_size // self.patch_size) ** 2 + 1
        self.scale = config.hidden_size**-0.5

        self.patch_embedding = Llama4UnfoldConvolution(config)

        self.class_embedding = nn.Parameter(self.scale * torch.randn(self.hidden_size))
        self.positional_embedding_vlm = nn.Parameter(self.scale * torch.randn(self.num_patches, self.hidden_size))
        self.rotary_embedding = Llama4VisionRotaryEmbedding(config)

        # layer norms
        self.layernorm_pre = nn.LayerNorm(self.hidden_size)
        self.layernorm_post = nn.LayerNorm(self.hidden_size)

        # encoders
        self.model = Llama4VisionEncoder(config)
        self.vision_adapter = Llama4VisionPixelShuffleMLP(config)
        self.post_init()

    def get_input_embeddings(self):
        """
        This function is used to fetch the first embedding layer to activate grads on inputs.
        """
        return self.patch_embedding

    def forward(
        self,
        pixel_values: torch.Tensor,
        attention_mask: Optional[torch.Tensor] = None,
        output_attentions: Optional[bool] = None,
        output_hidden_states: Optional[bool] = None,
        return_dict: Optional[bool] = None,
    ) -> Union[BaseModelOutput, tuple[torch.Tensor, ...]]:
        r"""

        Example:

        ```python
        >>> from PIL import Image
        >>> import requests
        >>> from transformers import AutoProcessor, MllamaVisionModel

        >>> checkpoint = "meta-llama/Llama-3.2-11B-Vision"
        >>> model = MllamaVisionModel.from_pretrained(checkpoint)
        >>> processor = AutoProcessor.from_pretrained(checkpoint)

        >>> url = "https://www.ilankelman.org/stopsigns/australia.jpg"
        >>> image = Image.open(requests.get(url, stream=True).raw)
        >>> inputs = processor(images=image, return_tensors="pt")

        >>> output = model(**inputs)

        >>> print(output.last_hidden_state.shape)
        torch.Size([1, 1, 4, 1025, 7680])
        ```
        """
        output_attentions = output_attentions if output_attentions is not None else self.config.output_attentions
        output_hidden_states = (
            output_hidden_states if output_hidden_states is not None else self.config.output_hidden_states
        )
        return_dict = return_dict if return_dict is not None else self.config.use_return_dict

        # num_concurrent_media and num_chunks are both currently 1
        batch_size_times_num_tiles, num_channels, height, width = pixel_values.shape
        num_concurrent_media = 1
        num_chunks = 1
        hidden_state = self.patch_embedding(pixel_values)
        _, num_patches, hidden_dim = hidden_state.shape

        # Add cls token
        hidden_state = hidden_state.reshape(
            batch_size_times_num_tiles * num_concurrent_media * num_chunks, num_patches, hidden_dim
        )
        class_embedding = self.class_embedding.expand(hidden_state.shape[0], 1, hidden_state.shape[-1])
        hidden_state = torch.cat([hidden_state, class_embedding], dim=1)
        num_patches += 1

        # Position embeddings
        hidden_state = hidden_state.reshape(
            batch_size_times_num_tiles * num_concurrent_media, num_chunks, num_patches, hidden_dim
        )
        positional_embedding = self.positional_embedding_vlm.to(dtype=hidden_state.dtype, device=hidden_state.device)
        hidden_state = hidden_state + positional_embedding

        hidden_state = self.layernorm_pre(hidden_state)

        hidden_state = hidden_state.view(batch_size_times_num_tiles, -1, hidden_dim)
        freqs_ci = self.rotary_embedding(pixel_values)

        output = self.model(
            hidden_state,
            attention_mask=None,
            output_hidden_states=output_hidden_states,
            output_attentions=output_attentions,
            freqs_ci=freqs_ci,
        )

        hidden_state = output.last_hidden_state

        hidden_state = self.layernorm_post(hidden_state)

        hidden_state = hidden_state[:, :-1, :]

        # now, we use Llama4VisionPixelShuffle + mlp to project embeddings
        hidden_state = self.vision_adapter(hidden_state)

        hidden_states = output.hidden_states if output_hidden_states else None

        if output_attentions:
            attentions = output[2]
        else:
            attentions = None

        if not return_dict:
            return tuple(v for v in [hidden_state, hidden_states, attentions] if v is not None)

        return BaseModelOutput(
            last_hidden_state=hidden_state,
            hidden_states=hidden_states,
            attentions=attentions,
        )


class Llama4ForConditionalGeneration(Llama4PreTrainedModel, GenerationMixin):
    _no_split_modules = ["Llama4TextDecoderLayer", "Llama4VisionEncoderLayer"]
    _tp_plan = {}
    base_model_prefix = ""
    config: Llama4Config

    def __init__(self, config: Llama4Config):
        super().__init__(config)
        self.vision_model = Llama4VisionModel(config.vision_config)

        self.multi_modal_projector = Llama4MultiModalProjector(config)
        self.language_model = Llama4ForCausalLM(config.text_config)
        self.vocab_size = config.text_config.vocab_size
        self.pad_token_id = self.config.pad_token_id if self.config.pad_token_id is not None else -1

        self.post_init()

    def get_input_embeddings(self):
        return self.language_model.get_input_embeddings()

    def set_input_embeddings(self, value):
        self.language_model.set_input_embeddings(value)

    def get_output_embeddings(self):
        return self.language_model.get_output_embeddings()

    def set_output_embeddings(self, new_embeddings):
        self.language_model.set_output_embeddings(new_embeddings)

    def set_decoder(self, decoder):
        self.language_model.set_decoder(decoder)

    def get_decoder(self):
        return self.language_model.get_decoder()

    def get_image_features(
        self,
        pixel_values: torch.FloatTensor,
        vision_feature_layer: Union[int, list[int]],
        vision_feature_select_strategy: str,
        **kwargs,
    ):
        """
        Obtains image last hidden states from the vision tower and apply al projection.

        Args:
            pixel_values (`torch.FloatTensor]` of shape `(batch_size, channels, height, width)`)
               The tensors corresponding to the input images.
            vision_feature_layer (`Union[int, list[int]]`):
                The index of the layer to select the vision feature. If multiple indices are provided,
                the vision feature of the corresponding indices will be concatenated to form the
                vision features.
            vision_feature_select_strategy (`str`):
                The feature selection strategy used to select the vision feature from the vision backbone.
                Can be one of `"default"` or `"full"`
        Returns:
            image_features (`torch.Tensor`): Image feature tensor of shape `(num_images, image_length, embed_dim)`).
        """
        if vision_feature_select_strategy not in ["default", "full"]:
            raise ValueError(f"Unexpected select feature strategy: {self.vision_feature_select_strategy}")
        kwargs = {k: v for k, v in kwargs.items() if v is not None}
        image_outputs = self.vision_model(pixel_values, output_hidden_states=False, **kwargs)
        hidden_state = image_outputs.last_hidden_state
        return hidden_state

    def get_placeholder_mask(
        self, input_ids: torch.LongTensor, inputs_embeds: torch.FloatTensor, image_features: torch.FloatTensor
    ):
        """
        Obtains multimodal placeholdr mask from `input_ids` or `inputs_embeds`, and checks that the placeholder token count is
        equal to the length of multimodal features. If the lengths are different, an error is raised.
        """
        if input_ids is None:
            special_image_mask = inputs_embeds == self.get_input_embeddings()(
                torch.tensor(self.config.image_token_id, dtype=torch.long, device=inputs_embeds.device)
            )
            special_image_mask = special_image_mask.all(-1)
        else:
            special_image_mask = input_ids == self.config.image_token_id

        n_image_tokens = special_image_mask.sum()
        special_image_mask = special_image_mask.unsqueeze(-1).expand_as(inputs_embeds).to(inputs_embeds.device)
        if inputs_embeds[special_image_mask].numel() != image_features.numel():
            raise ValueError(
                f"Image features and image tokens do not match: tokens: {n_image_tokens}, features {image_features.shape[0]}"
            )
        return special_image_mask

    @auto_docstring
    def forward(
        self,
        input_ids: torch.LongTensor = None,
        pixel_values: torch.FloatTensor = None,
        attention_mask: Optional[torch.Tensor] = None,
        position_ids: Optional[torch.LongTensor] = None,
        past_key_values: Optional[Cache] = None,
        inputs_embeds: Optional[torch.FloatTensor] = None,
        vision_feature_layer: Optional[Union[int, list[int]]] = None,
        vision_feature_select_strategy: Optional[str] = None,
        labels: Optional[torch.LongTensor] = None,
        use_cache: Optional[bool] = None,
        output_attentions: Optional[bool] = None,
        output_hidden_states: Optional[bool] = None,
        return_dict: Optional[bool] = None,
        cache_position: Optional[torch.LongTensor] = None,
        logits_to_keep: Union[int, torch.Tensor] = 0,
        image_sizes: torch.Tensor = None,
        **kwargs: Unpack[TransformersKwargs],
    ) -> Union[tuple, Llama4CausalLMOutputWithPast]:
        r"""
        labels (`torch.LongTensor` of shape `(batch_size, sequence_length)`, *optional*):
            Labels for computing the masked language modeling loss. Indices should either be in `[0, ...,
            config.vocab_size]` or -100 (see `input_ids` docstring). Tokens with indices set to `-100` are ignored
            (masked), the loss is only computed for the tokens with labels in `[0, ..., config.vocab_size]`.

        Example:

        ```python
        >>> from PIL import Image
        >>> import requests
        >>> from transformers import AutoProcessor, LlavaForConditionalGeneration

        >>> model = LlavaForConditionalGeneration.from_pretrained("llava-hf/llava-1.5-7b-hf")
        >>> processor = AutoProcessor.from_pretrained("llava-hf/llava-1.5-7b-hf")

        >>> prompt = "USER: <image>\nWhat's the content of the image? ASSISTANT:"
        >>> url = "https://www.ilankelman.org/stopsigns/australia.jpg"
        >>> image = Image.open(requests.get(url, stream=True).raw)

        >>> inputs = processor(images=image, text=prompt, return_tensors="pt")

        >>> # Generate
        >>> generate_ids = model.generate(**inputs, max_new_tokens=15)
        >>> processor.batch_decode(generate_ids, skip_special_tokens=True, clean_up_tokenization_spaces=False)[0]
        "USER:  \nWhat's the content of the image? ASSISTANT: The image features a busy city street with a stop sign prominently displayed"
        ```"""

        output_attentions = output_attentions if output_attentions is not None else self.config.output_attentions
        output_hidden_states = (
            output_hidden_states if output_hidden_states is not None else self.config.output_hidden_states
        )
        return_dict = return_dict if return_dict is not None else self.config.use_return_dict
        vision_feature_layer = (
            vision_feature_layer
            if vision_feature_layer is not None
            else self.config.vision_config.vision_feature_layer
        )
        vision_feature_select_strategy = (
            vision_feature_select_strategy
            if vision_feature_select_strategy is not None
            else self.config.vision_config.vision_feature_select_strategy
        )

        if (input_ids is None) ^ (inputs_embeds is not None):
            raise ValueError("You must specify exactly one of input_ids or inputs_embeds")

        if pixel_values is not None and inputs_embeds is not None:
            raise ValueError(
                "You cannot specify both pixel_values and inputs_embeds at the same time, and must specify either one"
            )

        if inputs_embeds is None:
            inputs_embeds = self.get_input_embeddings()(input_ids)

        if pixel_values is not None:
            image_features = self.get_image_features(
                pixel_values=pixel_values,
                vision_feature_layer=vision_feature_layer,
                vision_feature_select_strategy=vision_feature_select_strategy,
                image_sizes=image_sizes,
            )

            vision_flat = image_features.view(-1, image_features.size(-1))
            projected_vision_flat = self.multi_modal_projector(vision_flat).to(
                inputs_embeds.device, inputs_embeds.dtype
            )
            special_image_mask = self.get_placeholder_mask(
                input_ids, inputs_embeds=inputs_embeds, image_features=projected_vision_flat
            )
            inputs_embeds = inputs_embeds.masked_scatter(special_image_mask, projected_vision_flat)

        outputs = self.language_model(
            attention_mask=attention_mask,
            position_ids=position_ids,
            past_key_values=past_key_values,
            inputs_embeds=inputs_embeds,
            use_cache=use_cache,
            output_attentions=output_attentions,
            output_hidden_states=output_hidden_states,
            return_dict=return_dict,
            cache_position=cache_position,
            logits_to_keep=logits_to_keep,
            **kwargs,
        )

        logits = outputs[0]

        loss = None
        if labels is not None:
            # Shift so that tokens < n predict n
            if attention_mask is not None:
                # we use the input attention mask to shift the logits and labels, because it is 2D.
                # we also crop attn mask in case it is longer, which happens in PrefixTuning with peft
                shift_attention_mask = attention_mask[:, -(logits.shape[1] - 1) :].to(logits.device)
                shift_logits = logits[..., :-1, :][shift_attention_mask.to(logits.device) != 0].contiguous()
                shift_labels = labels[..., 1:][shift_attention_mask.to(labels.device) != 0].contiguous()
            else:
                shift_logits = logits[..., :-1, :].contiguous()
                shift_labels = labels[..., 1:].contiguous()
            # Flatten the tokens
            loss_fct = nn.CrossEntropyLoss()
            loss = loss_fct(
                shift_logits.view(-1, shift_logits.size(-1)), shift_labels.view(-1).to(shift_logits.device)
            )

        if not return_dict:
            output = (logits,) + outputs[1:]
            return (loss,) + output if loss is not None else output

        return Llama4CausalLMOutputWithPast(
            loss=loss,
            logits=logits,
            past_key_values=outputs.past_key_values,
            hidden_states=outputs.hidden_states,
            attentions=outputs.attentions,
            image_hidden_states=image_features if pixel_values is not None else None,
        )

    def prepare_inputs_for_generation(
        self,
        input_ids,
        past_key_values=None,
        inputs_embeds=None,
        pixel_values=None,
        attention_mask=None,
        cache_position=None,
        logits_to_keep=None,
        **kwargs,
    ):
        # Overwritten -- in specific circumstances we don't want to forward image inputs to the model

        model_inputs = self.language_model.prepare_inputs_for_generation(
            input_ids,
            past_key_values=past_key_values,
            inputs_embeds=inputs_embeds,
            attention_mask=attention_mask,
            cache_position=cache_position,
            logits_to_keep=logits_to_keep,
            **kwargs,
        )

        if cache_position[0] == 0:
            # If we're in cached decoding stage, pixel values should be None because input ids do not contain special image token anymore
            # Otherwise we need pixel values to be passed to model
            model_inputs["pixel_values"] = pixel_values

        return model_inputs


__all__ = [
    "Llama4PreTrainedModel",
    "Llama4TextModel",
    "Llama4VisionModel",
    "Llama4ForCausalLM",
    "Llama4ForConditionalGeneration",
]