run lint

fastvideo/v1/configs/models/dits/__init__.py

@@ -1,5 +1,10 @@
+# SPDX-License-Identifier: Apache-2.0
+
+from fastvideo.v1.configs.models.dits.cosmos import CosmosConfig
 from fastvideo.v1.configs.models.dits.hunyuanvideo import HunyuanVideoConfig
 from fastvideo.v1.configs.models.dits.stepvideo import StepVideoConfig
 from fastvideo.v1.configs.models.dits.wanvideo import WanVideoConfig
 
-__all__ = ["HunyuanVideoConfig", "WanVideoConfig", "StepVideoConfig"]
+__all__ = [
+    "HunyuanVideoConfig", "WanVideoConfig", "StepVideoConfig", "CosmosConfig"
+]

fastvideo/v1/configs/models/dits/cosmos.py

@@ -0,0 +1,104 @@
+# SPDX-License-Identifier: Apache-2.0
+from dataclasses import dataclass, field
+
+from fastvideo.v1.configs.models.dits.base import DiTArchConfig, DiTConfig
+
+
+def is_transformer_blocks(n: str, m) -> bool:
+    return "transformer_blocks" in n and str.isdigit(n.split(".")[-1])
+
+
+@dataclass
+class CosmosArchConfig(DiTArchConfig):
+    _fsdp_shard_conditions: list = field(
+        default_factory=lambda: [is_transformer_blocks])
+
+    _param_names_mapping: dict = field(
+        default_factory=lambda: {
+            r"^patch_embed\.(.*)$": r"patch_embed.\1",
+            r"^time_embed\.time_proj\.(.*)$": r"time_embed.time_proj.\1",
+            r"^time_embed\.t_embedder\.(.*)$": r"time_embed.t_embedder.\1",
+            r"^time_embed\.norm\.(.*)$": r"time_embed.norm.\1",
+            r"^transformer_blocks\.(\d+)\.attn1\.to_q\.(.*)$":
+            r"transformer_blocks.\1.attn1.to_q.\2",
+            r"^transformer_blocks\.(\d+)\.attn1\.to_k\.(.*)$":
+            r"transformer_blocks.\1.attn1.to_k.\2",
+            r"^transformer_blocks\.(\d+)\.attn1\.to_v\.(.*)$":
+            r"transformer_blocks.\1.attn1.to_v.\2",
+            r"^transformer_blocks\.(\d+)\.attn1\.to_out\.0\.(.*)$":
+            r"transformer_blocks.\1.attn1.to_out.\2",
+            r"^transformer_blocks\.(\d+)\.attn1\.norm_q\.(.*)$":
+            r"transformer_blocks.\1.attn1.norm_q.\2",
+            r"^transformer_blocks\.(\d+)\.attn1\.norm_k\.(.*)$":
+            r"transformer_blocks.\1.attn1.norm_k.\2",
+            r"^transformer_blocks\.(\d+)\.attn2\.to_q\.(.*)$":
+            r"transformer_blocks.\1.attn2.to_q.\2",
+            r"^transformer_blocks\.(\d+)\.attn2\.to_k\.(.*)$":
+            r"transformer_blocks.\1.attn2.to_k.\2",
+            r"^transformer_blocks\.(\d+)\.attn2\.to_v\.(.*)$":
+            r"transformer_blocks.\1.attn2.to_v.\2",
+            r"^transformer_blocks\.(\d+)\.attn2\.to_out\.0\.(.*)$":
+            r"transformer_blocks.\1.attn2.to_out.\2",
+            r"^transformer_blocks\.(\d+)\.attn2\.norm_q\.(.*)$":
+            r"transformer_blocks.\1.attn2.norm_q.\2",
+            r"^transformer_blocks\.(\d+)\.attn2\.norm_k\.(.*)$":
+            r"transformer_blocks.\1.attn2.norm_k.\2",
+            r"^transformer_blocks\.(\d+)\.ff\.net\.0\.proj\.(.*)$":
+            r"transformer_blocks.\1.ff.fc_in.\2",
+            r"^transformer_blocks\.(\d+)\.ff\.net\.2\.(.*)$":
+            r"transformer_blocks.\1.ff.fc_out.\2",
+            r"^norm_out\.(.*)$": r"norm_out.\1",
+            r"^proj_out\.(.*)$": r"proj_out.\1",
+        })
+
+    _lora_param_names_mapping: dict = field(
+        default_factory=lambda: {
+            r"^transformer_blocks\.(\d+)\.attn1\.to_q\.(.*)$":
+            r"transformer_blocks.\1.attn1.to_q.\2",
+            r"^transformer_blocks\.(\d+)\.attn1\.to_k\.(.*)$":
+            r"transformer_blocks.\1.attn1.to_k.\2",
+            r"^transformer_blocks\.(\d+)\.attn1\.to_v\.(.*)$":
+            r"transformer_blocks.\1.attn1.to_v.\2",
+            r"^transformer_blocks\.(\d+)\.attn1\.to_out\.(.*)$":
+            r"transformer_blocks.\1.attn1.to_out.\2",
+            r"^transformer_blocks\.(\d+)\.attn2\.to_q\.(.*)$":
+            r"transformer_blocks.\1.attn2.to_q.\2",
+            r"^transformer_blocks\.(\d+)\.attn2\.to_k\.(.*)$":
+            r"transformer_blocks.\1.attn2.to_k.\2",
+            r"^transformer_blocks\.(\d+)\.attn2\.to_v\.(.*)$":
+            r"transformer_blocks.\1.attn2.to_v.\2",
+            r"^transformer_blocks\.(\d+)\.attn2\.to_out\.(.*)$":
+            r"transformer_blocks.\1.attn2.to_out.\2",
+            r"^transformer_blocks\.(\d+)\.ff\.(.*)$":
+            r"transformer_blocks.\1.ff.\2",
+        })
+
+    # Cosmos-specific config parameters based on transformer_cosmos.py
+    in_channels: int = 16
+    out_channels: int = 16
+    num_attention_heads: int = 16
+    attention_head_dim: int = 128
+    num_layers: int = 28
+    mlp_ratio: float = 4.0
+    text_embed_dim: int = 1024
+    adaln_lora_dim: int = 256
+    max_size: tuple[int, int, int] = (128, 240, 240)
+    patch_size: tuple[int, int, int] = (1, 2, 2)
+    rope_scale: tuple[float, float, float] = (1.0, 4.0, 4.0)
+    concat_padding_mask: bool = True
+    extra_pos_embed_type: str | None = None
+    qk_norm: str = "rms_norm"
+    eps: float = 1e-6
+    exclude_lora_layers: list[str] = field(default_factory=lambda: ["embedder"])
+
+    def __post_init__(self):
+        super().__post_init__()
+        self.out_channels = self.out_channels or self.in_channels
+        self.hidden_size = self.num_attention_heads * self.attention_head_dim
+        self.num_channels_latents = self.in_channels
+
+
+@dataclass
+class CosmosConfig(DiTConfig):
+    arch_config: DiTArchConfig = field(default_factory=CosmosArchConfig)
+    prefix: str = "Cosmos"

fastvideo/v1/configs/sample/cosmos.py

@@ -0,0 +1,33 @@
+# SPDX-License-Identifier: Apache-2.0
+from dataclasses import dataclass, field
+
+from fastvideo.v1.configs.sample.base import CacheParams
+
+
+@dataclass
+class CosmosTeaCacheParams(CacheParams):
+    cache_type: str = "teacache"
+    teacache_thresh: float = 0.0
+    use_ret_steps: bool = True
+    ret_steps_coeffs: list[float] = field(default_factory=list)
+    non_ret_steps_coeffs: list[float] = field(default_factory=list)
+
+    @property
+    def coefficients(self) -> list[float]:
+        if self.use_ret_steps:
+            return self.ret_steps_coeffs
+        else:
+            return self.non_ret_steps_coeffs
+
+    @property
+    def ret_steps(self) -> int:
+        if self.use_ret_steps:
+            return 5 * 2
+        else:
+            return 1 * 2
+
+    def get_cutoff_steps(self, num_inference_steps: int) -> int:
+        if self.use_ret_steps:
+            return num_inference_steps * 2
+        else:
+            return num_inference_steps * 2 - 2

fastvideo/v1/layers/rotary_embedding.py

@@ -44,6 +44,60 @@ def _rotate_gptj(x: torch.Tensor) -> torch.Tensor:
     return x.flatten(-2)
 
 
+def apply_rotary_emb(
+    x: torch.Tensor,
+    freqs_cis: torch.Tensor | tuple[torch.Tensor],
+    use_real: bool = True,
+    use_real_unbind_dim: int = -1,
+) -> tuple[torch.Tensor, torch.Tensor]:
+    """
+    Apply rotary embeddings to input tensors using the given frequency tensor. This function applies rotary embeddings
+    to the given query or key 'x' tensors using the provided frequency tensor 'freqs_cis'. The input tensors are
+    reshaped as complex numbers, and the frequency tensor is reshaped for broadcasting compatibility. The resulting
+    tensors contain rotary embeddings and are returned as real tensors.
+
+    Args:
+        x (`torch.Tensor`):
+            Query or key tensor to apply rotary embeddings. [B, H, S, D] xk (torch.Tensor): Key tensor to apply
+        freqs_cis (`Tuple[torch.Tensor]`): Precomputed frequency tensor for complex exponentials. ([S, D], [S, D],)
+
+    Returns:
+        Tuple[torch.Tensor, torch.Tensor]: Tuple of modified query tensor and key tensor with rotary embeddings.
+    """
+    if use_real:
+        cos, sin = freqs_cis  # [S, D]
+        cos = cos[None, None]
+        sin = sin[None, None]
+        cos, sin = cos.to(x.device), sin.to(x.device)
+
+        if use_real_unbind_dim == -1:
+            # Used for flux, cogvideox, hunyuan-dit
+            x_real, x_imag = x.reshape(*x.shape[:-1], -1,
+                                       2).unbind(-1)  # [B, S, H, D//2]
+            x_rotated = torch.stack([-x_imag, x_real], dim=-1).flatten(3)
+        elif use_real_unbind_dim == -2:
+            # Used for Stable Audio, OmniGen, CogView4 and Cosmos
+            x_real, x_imag = x.reshape(*x.shape[:-1], 2,
+                                       -1).unbind(-2)  # [B, S, H, D//2]
+            x_rotated = torch.cat([-x_imag, x_real], dim=-1)
+        else:
+            raise ValueError(
+                f"`use_real_unbind_dim={use_real_unbind_dim}` but should be -1 or -2."
+            )
+
+        out = (x.float() * cos + x_rotated.float() * sin).to(x.dtype)
+
+        return out
+    else:
+        # used for lumina
+        x_rotated = torch.view_as_complex(x.float().reshape(
+            *x.shape[:-1], -1, 2))
+        freqs_cis = freqs_cis.unsqueeze(2)
+        x_out = torch.view_as_real(x_rotated * freqs_cis).flatten(3)
+
+        return x_out.type_as(x)
+
+
 def _apply_rotary_emb(
     x: torch.Tensor,
     cos: torch.Tensor,

fastvideo/v1/layers/visual_embedding.py

@@ -173,3 +173,80 @@ def unpatchify(x, t, h, w, patch_size, channels) -> torch.Tensor:
     imgs = x.reshape(shape=(x.shape[0], c, t * pt, h * ph, w * pw))
 
     return imgs
+
+
+def get_timestep_embedding(
+    timesteps: torch.Tensor,
+    embedding_dim: int,
+    flip_sin_to_cos: bool = False,
+    downscale_freq_shift: float = 1,
+    scale: float = 1,
+    max_period: int = 10000,
+) -> torch.Tensor:
+    """
+    This matches the implementation in Denoising Diffusion Probabilistic Models: Create sinusoidal timestep embeddings.
+
+    Args
+        timesteps (torch.Tensor):
+            a 1-D Tensor of N indices, one per batch element. These may be fractional.
+        embedding_dim (int):
+            the dimension of the output.
+        flip_sin_to_cos (bool):
+            Whether the embedding order should be `cos, sin` (if True) or `sin, cos` (if False)
+        downscale_freq_shift (float):
+            Controls the delta between frequencies between dimensions
+        scale (float):
+            Scaling factor applied to the embeddings.
+        max_period (int):
+            Controls the maximum frequency of the embeddings
+    Returns
+        torch.Tensor: an [N x dim] Tensor of positional embeddings.
+    """
+    assert len(timesteps.shape) == 1, "Timesteps should be a 1d-array"
+
+    half_dim = embedding_dim // 2
+    exponent = -math.log(max_period) * torch.arange(
+        start=0, end=half_dim, dtype=torch.float32, device=timesteps.device)
+    exponent = exponent / (half_dim - downscale_freq_shift)
+
+    emb = torch.exp(exponent)
+    emb = timesteps[:, None].float() * emb[None, :]
+
+    # scale embeddings
+    emb = scale * emb
+
+    # concat sine and cosine embeddings
+    emb = torch.cat([torch.sin(emb), torch.cos(emb)], dim=-1)
+
+    # flip sine and cosine embeddings
+    if flip_sin_to_cos:
+        emb = torch.cat([emb[:, half_dim:], emb[:, :half_dim]], dim=-1)
+
+    # zero pad
+    if embedding_dim % 2 == 1:
+        emb = torch.nn.functional.pad(emb, (0, 1, 0, 0))
+    return emb
+
+
+class Timesteps(nn.Module):
+
+    def __init__(self,
+                 num_channels: int,
+                 flip_sin_to_cos: bool,
+                 downscale_freq_shift: float,
+                 scale: int = 1):
+        super().__init__()
+        self.num_channels = num_channels
+        self.flip_sin_to_cos = flip_sin_to_cos
+        self.downscale_freq_shift = downscale_freq_shift
+        self.scale = scale
+
+    def forward(self, timesteps: torch.Tensor) -> torch.Tensor:
+        t_emb = get_timestep_embedding(
+            timesteps,
+            self.num_channels,
+            flip_sin_to_cos=self.flip_sin_to_cos,
+            downscale_freq_shift=self.downscale_freq_shift,
+            scale=self.scale,
+        )
+        return t_emb

fastvideo/v1/models/dits/cosmos.py

@@ -0,0 +1,731 @@
+# SPDX-License-Identifier: Apache-2.0
+
+import math
+from typing import Any
+
+import numpy as np
+import torch
+import torch.nn as nn
+
+from fastvideo.v1.attention import DistributedAttention, LocalAttention
+from fastvideo.v1.configs.models.dits.cosmos import CosmosConfig
+from fastvideo.v1.forward_context import get_forward_context
+from fastvideo.v1.layers.layernorm import RMSNorm
+from fastvideo.v1.layers.linear import ReplicatedLinear
+from fastvideo.v1.layers.mlp import MLP
+from fastvideo.v1.layers.rotary_embedding import apply_rotary_emb
+from fastvideo.v1.layers.visual_embedding import Timesteps
+from fastvideo.v1.models.dits.base import BaseDiT
+from fastvideo.v1.platforms import AttentionBackendEnum
+
+
+class CosmosPatchEmbed(nn.Module):
+
+    def __init__(self,
+                 in_channels: int,
+                 out_channels: int,
+                 patch_size: tuple[int, int, int],
+                 bias: bool = True) -> None:
+        super().__init__()
+        self.patch_size = patch_size
+
+        self.proj = nn.Linear(in_channels * patch_size[0] * patch_size[1] *
+                              patch_size[2],
+                              out_channels,
+                              bias=bias)
+
+    def forward(self, hidden_states: torch.Tensor) -> torch.Tensor:
+        batch_size, num_channels, num_frames, height, width = hidden_states.shape
+        p_t, p_h, p_w = self.patch_size
+        hidden_states = hidden_states.reshape(batch_size, num_channels,
+                                              num_frames // p_t, p_t,
+                                              height // p_h, p_h, width // p_w,
+                                              p_w)
+        hidden_states = hidden_states.permute(0, 2, 4, 6, 1, 3, 5,
+                                              7).flatten(4, 7)
+        hidden_states = self.proj(hidden_states)
+        return hidden_states
+
+
+class CosmosTimestepEmbedding(nn.Module):
+
+    def __init__(self, in_features: int, out_features: int) -> None:
+        super().__init__()
+        self.linear_1 = nn.Linear(in_features, out_features, bias=False)
+        self.activation = nn.SiLU()
+        self.linear_2 = nn.Linear(out_features, 3 * out_features, bias=False)
+
+    def forward(self, timesteps: torch.Tensor) -> torch.Tensor:
+        emb = self.linear_1(timesteps)
+        emb = self.activation(emb)
+        emb = self.linear_2(emb)
+        return emb
+
+
+class CosmosEmbedding(nn.Module):
+
+    def __init__(self, embedding_dim: int, condition_dim: int) -> None:
+        super().__init__()
+
+        self.time_proj = Timesteps(embedding_dim,
+                                   flip_sin_to_cos=True,
+                                   downscale_freq_shift=0.0)
+        self.t_embedder = CosmosTimestepEmbedding(embedding_dim, condition_dim)
+        self.norm = RMSNorm(embedding_dim, eps=1e-6)
+
+    def forward(self, hidden_states: torch.Tensor,
+                timestep: torch.LongTensor) -> torch.Tensor:
+        timesteps_proj = self.time_proj(timestep).type_as(hidden_states)
+        temb = self.t_embedder(timesteps_proj)
+        embedded_timestep = self.norm(timesteps_proj)
+        return temb, embedded_timestep
+
+
+class CosmosAdaLayerNorm(nn.Module):
+
+    def __init__(self, in_features: int, hidden_features: int) -> None:
+        super().__init__()
+        self.embedding_dim = in_features
+
+        self.activation = nn.SiLU()
+        self.norm = nn.LayerNorm(in_features,
+                                 elementwise_affine=False,
+                                 eps=1e-6)
+        self.linear_1 = nn.Linear(in_features, hidden_features, bias=False)
+        self.linear_2 = nn.Linear(hidden_features, 2 * in_features, bias=False)
+
+    def forward(self,
+                hidden_states: torch.Tensor,
+                embedded_timestep: torch.Tensor,
+                temb: torch.Tensor | None = None) -> torch.Tensor:
+        embedded_timestep = self.activation(embedded_timestep)
+        embedded_timestep = self.linear_1(embedded_timestep)
+        embedded_timestep = self.linear_2(embedded_timestep)
+
+        if temb is not None:
+            embedded_timestep = embedded_timestep + temb[..., :2 *
+                                                         self.embedding_dim]
+
+        shift, scale = embedded_timestep.chunk(2, dim=-1)
+        hidden_states = self.norm(hidden_states)
+
+        if embedded_timestep.ndim == 2:
+            shift, scale = (x.unsqueeze(1) for x in (shift, scale))
+
+        hidden_states = hidden_states * (1 + scale) + shift
+        return hidden_states
+
+
+class CosmosAdaLayerNormZero(nn.Module):
+
+    def __init__(self,
+                 in_features: int,
+                 hidden_features: int | None = None) -> None:
+        super().__init__()
+
+        self.norm = nn.LayerNorm(in_features,
+                                 elementwise_affine=False,
+                                 eps=1e-6)
+        self.activation = nn.SiLU()
+
+        if hidden_features is None:
+            self.linear_1 = nn.Identity()
+        else:
+            self.linear_1 = nn.Linear(in_features, hidden_features, bias=False)
+
+        self.linear_2 = nn.Linear(
+            hidden_features if hidden_features is not None else in_features,
+            3 * in_features,
+            bias=False)
+
+    def forward(
+        self,
+        hidden_states: torch.Tensor,
+        embedded_timestep: torch.Tensor,
+        temb: torch.Tensor | None = None,
+    ) -> torch.Tensor:
+        embedded_timestep = self.activation(embedded_timestep)
+        embedded_timestep = self.linear_1(embedded_timestep)
+        embedded_timestep = self.linear_2(embedded_timestep)
+
+        if temb is not None:
+            embedded_timestep = embedded_timestep + temb
+
+        shift, scale, gate = embedded_timestep.chunk(3, dim=-1)
+        hidden_states = self.norm(hidden_states)
+
+        if embedded_timestep.ndim == 2:
+            shift, scale, gate = (x.unsqueeze(1) for x in (shift, scale, gate))
+
+        hidden_states = hidden_states * (1 + scale) + shift
+        return hidden_states, gate
+
+
+class CosmosSelfAttention(nn.Module):
+
+    def __init__(self,
+                 dim: int,
+                 num_heads: int,
+                 qk_norm=True,
+                 eps=1e-6,
+                 supported_attention_backends: tuple[AttentionBackendEnum, ...]
+                 | None = None,
+                 prefix: str = "") -> None:
+        assert dim % num_heads == 0
+        super().__init__()
+        self.dim = dim
+        self.num_heads = num_heads
+        self.head_dim = dim // num_heads
+        self.qk_norm = qk_norm
+        self.eps = eps
+
+        # layers
+        self.to_q = ReplicatedLinear(dim, dim, bias=False)
+        self.to_k = ReplicatedLinear(dim, dim, bias=False)
+        self.to_v = ReplicatedLinear(dim, dim, bias=False)
+        self.to_out = ReplicatedLinear(dim, dim, bias=False)
+        self.norm_q = RMSNorm(self.head_dim,
+                              eps=eps) if qk_norm else nn.Identity()
+        self.norm_k = RMSNorm(self.head_dim,
+                              eps=eps) if qk_norm else nn.Identity()
+
+        # Attention mechanism
+        self.attn = DistributedAttention(
+            num_heads=num_heads,
+            head_size=self.head_dim,
+            dropout_rate=0,
+            softmax_scale=None,
+            causal=False,
+            supported_attention_backends=supported_attention_backends,
+            prefix=prefix)
+
+    def forward(self,
+                hidden_states: torch.Tensor,
+                encoder_hidden_states: torch.Tensor | None = None,
+                attention_mask: torch.Tensor | None = None,
+                image_rotary_emb: torch.Tensor | None = None) -> torch.Tensor:
+
+        if encoder_hidden_states is None:
+            encoder_hidden_states = hidden_states
+
+        # Get QKV
+        query, _ = self.to_q(hidden_states)
+        key, _ = self.to_k(encoder_hidden_states)
+        value, _ = self.to_v(encoder_hidden_states)
+
+        # Reshape for multi-head attention
+        query = query.unflatten(2, (self.num_heads, -1)).transpose(1, 2)
+        key = key.unflatten(2, (self.num_heads, -1)).transpose(1, 2)
+        value = value.unflatten(2, (self.num_heads, -1)).transpose(1, 2)
+
+        # Apply normalization
+        if self.norm_q is not None:
+            query = self.norm_q.forward_native(query)
+        if self.norm_k is not None:
+            key = self.norm_k.forward_native(key)
+
+        # Apply RoPE if provided
+        if image_rotary_emb is not None:
+            query = apply_rotary_emb(query,
+                                     image_rotary_emb,
+                                     use_real=True,
+                                     use_real_unbind_dim=-2)
+            key = apply_rotary_emb(key,
+                                   image_rotary_emb,
+                                   use_real=True,
+                                   use_real_unbind_dim=-2)
+
+        # Attention computation
+        attn_output, _ = self.attn(query, key, value)
+        # attn_output = attn_output.flatten(2)
+        attn_output = attn_output.transpose(1, 2).flatten(2, 3).type_as(query)
+
+        # Output projection
+        attn_output, _ = self.to_out(attn_output)
+        return attn_output
+
+
+class CosmosCrossAttention(nn.Module):
+
+    def __init__(self,
+                 dim: int,
+                 cross_attention_dim: int,
+                 num_heads: int,
+                 qk_norm=True,
+                 eps=1e-6,
+                 supported_attention_backends: tuple[AttentionBackendEnum, ...]
+                 | None = None,
+                 prefix: str = "") -> None:
+        assert dim % num_heads == 0
+        super().__init__()
+        self.dim = dim
+        self.cross_attention_dim = cross_attention_dim
+        self.num_heads = num_heads
+        self.head_dim = dim // num_heads
+        self.qk_norm = qk_norm
+        self.eps = eps
+
+        # layers
+        self.to_q = ReplicatedLinear(dim, dim, bias=False)
+        self.to_k = ReplicatedLinear(cross_attention_dim, dim, bias=False)
+        self.to_v = ReplicatedLinear(cross_attention_dim, dim, bias=False)
+        self.to_out = ReplicatedLinear(dim, dim, bias=False)
+        self.norm_q = RMSNorm(self.head_dim,
+                              eps=eps) if qk_norm else nn.Identity()
+        self.norm_k = RMSNorm(self.head_dim,
+                              eps=eps) if qk_norm else nn.Identity()
+
+        # Attention mechanism
+        self.attn = LocalAttention(
+            num_heads=num_heads,
+            head_size=self.head_dim,
+            dropout_rate=0,
+            softmax_scale=None,
+            causal=False,
+            supported_attention_backends=supported_attention_backends)
+
+    def forward(self,
+                hidden_states: torch.Tensor,
+                encoder_hidden_states: torch.Tensor,
+                attention_mask: torch.Tensor | None = None) -> torch.Tensor:
+
+        # Get QKV
+        query, _ = self.to_q(hidden_states)
+        key, _ = self.to_k(encoder_hidden_states)
+        value, _ = self.to_v(encoder_hidden_states)
+
+        # Reshape for multi-head attention
+        query = query.unflatten(2, (self.num_heads, -1))
+        key = key.unflatten(2, (self.num_heads, -1))
+        value = value.unflatten(2, (self.num_heads, -1))
+
+        # Apply normalization
+        if self.norm_q is not None:
+            query = self.norm_q.forward_native(query)
+        if self.norm_k is not None:
+            key = self.norm_k.forward_native(key)
+
+        # Attention computation
+        attn_output = self.attn(query, key, value)
+        attn_output = attn_output.flatten(2, 3).type_as(query)
+
+        # Output projection
+        attn_output, _ = self.to_out(attn_output)
+        return attn_output
+
+
+class CosmosTransformerBlock(nn.Module):
+
+    def __init__(
+        self,
+        num_attention_heads: int,
+        attention_head_dim: int,
+        cross_attention_dim: int,
+        mlp_ratio: float = 4.0,
+        adaln_lora_dim: int = 256,
+        qk_norm: str = "rms_norm",
+        out_bias: bool = False,
+        supported_attention_backends: tuple[AttentionBackendEnum, ...]
+        | None = None,
+        prefix: str = "",
+    ) -> None:
+        super().__init__()
+
+        hidden_size = num_attention_heads * attention_head_dim
+
+        self.norm1 = CosmosAdaLayerNormZero(in_features=hidden_size,
+                                            hidden_features=adaln_lora_dim)
+        self.attn1 = CosmosSelfAttention(
+            dim=hidden_size,
+            num_heads=num_attention_heads,
+            qk_norm=(qk_norm == "rms_norm"),
+            supported_attention_backends=supported_attention_backends,
+            prefix=f"{prefix}.attn1")
+
+        self.norm2 = CosmosAdaLayerNormZero(in_features=hidden_size,
+                                            hidden_features=adaln_lora_dim)
+        self.attn2 = CosmosCrossAttention(
+            dim=hidden_size,
+            cross_attention_dim=cross_attention_dim,
+            num_heads=num_attention_heads,
+            qk_norm=(qk_norm == "rms_norm"),
+            supported_attention_backends=supported_attention_backends,
+            prefix=f"{prefix}.attn2")
+
+        self.norm3 = CosmosAdaLayerNormZero(in_features=hidden_size,
+                                            hidden_features=adaln_lora_dim)
+        self.ff = MLP(hidden_size,
+                      int(hidden_size * mlp_ratio),
+                      act_type="gelu",
+                      bias=False)
+
+    def forward(
+        self,
+        hidden_states: torch.Tensor,
+        encoder_hidden_states: torch.Tensor,
+        embedded_timestep: torch.Tensor,
+        temb: torch.Tensor | None = None,
+        image_rotary_emb: torch.Tensor | None = None,
+        extra_pos_emb: torch.Tensor | None = None,
+        attention_mask: torch.Tensor | None = None,
+    ) -> torch.Tensor:
+        if extra_pos_emb is not None:
+            hidden_states = hidden_states + extra_pos_emb
+
+        # 1. Self Attention
+        norm_hidden_states, gate = self.norm1(hidden_states, embedded_timestep,
+                                              temb)
+        attn_output = self.attn1(norm_hidden_states,
+                                 image_rotary_emb=image_rotary_emb)
+        hidden_states = hidden_states + gate * attn_output
+
+        # 2. Cross Attention
+        norm_hidden_states, gate = self.norm2(hidden_states, embedded_timestep,
+                                              temb)
+        attn_output = self.attn2(norm_hidden_states,
+                                 encoder_hidden_states=encoder_hidden_states,
+                                 attention_mask=attention_mask)
+        hidden_states = hidden_states + gate * attn_output
+
+        # 3. Feed Forward
+        norm_hidden_states, gate = self.norm3(hidden_states, embedded_timestep,
+                                              temb)
+        ff_output = self.ff(norm_hidden_states)
+        hidden_states = hidden_states + gate * ff_output
+
+        return hidden_states
+
+
+class CosmosRotaryPosEmbed(nn.Module):
+
+    def __init__(
+            self,
+            hidden_size: int,
+            max_size: tuple[int, int, int] = (128, 240, 240),
+            patch_size: tuple[int, int, int] = (1, 2, 2),
+            base_fps: int = 24,
+            rope_scale: tuple[float, float, float] = (2.0, 1.0, 1.0),
+    ) -> None:
+        super().__init__()
+
+        self.max_size = [
+            size // patch
+            for size, patch in zip(max_size, patch_size, strict=False)
+        ]
+        self.patch_size = patch_size
+        self.base_fps = base_fps
+
+        self.dim_h = hidden_size // 6 * 2
+        self.dim_w = hidden_size // 6 * 2
+        self.dim_t = hidden_size - self.dim_h - self.dim_w
+
+        self.h_ntk_factor = rope_scale[1]**(self.dim_h / (self.dim_h - 2))
+        self.w_ntk_factor = rope_scale[2]**(self.dim_w / (self.dim_w - 2))
+        self.t_ntk_factor = rope_scale[0]**(self.dim_t / (self.dim_t - 2))
+
+    def forward(self,
+                hidden_states: torch.Tensor,
+                fps: int | None = None) -> tuple[torch.Tensor, torch.Tensor]:
+        batch_size, num_channels, num_frames, height, width = hidden_states.shape
+        pe_size = [
+            num_frames // self.patch_size[0], height // self.patch_size[1],
+            width // self.patch_size[2]
+        ]
+        device = hidden_states.device
+
+        h_theta = 10000.0 * self.h_ntk_factor
+        w_theta = 10000.0 * self.w_ntk_factor
+        t_theta = 10000.0 * self.t_ntk_factor
+
+        seq = torch.arange(max(self.max_size),
+                           device=device,
+                           dtype=torch.float32)
+        dim_h_range = (
+            torch.arange(0, self.dim_h, 2, device=device,
+                         dtype=torch.float32)[:(self.dim_h // 2)] / self.dim_h)
+        dim_w_range = (
+            torch.arange(0, self.dim_w, 2, device=device,
+                         dtype=torch.float32)[:(self.dim_w // 2)] / self.dim_w)
+        dim_t_range = (
+            torch.arange(0, self.dim_t, 2, device=device,
+                         dtype=torch.float32)[:(self.dim_t // 2)] / self.dim_t)
+        h_spatial_freqs = 1.0 / (h_theta**dim_h_range)
+        w_spatial_freqs = 1.0 / (w_theta**dim_w_range)
+        temporal_freqs = 1.0 / (t_theta**dim_t_range)
+
+        emb_h = torch.outer(seq[:pe_size[1]],
+                            h_spatial_freqs)[None, :, None, :].repeat(
+                                pe_size[0], 1, pe_size[2], 1)
+        emb_w = torch.outer(seq[:pe_size[2]],
+                            w_spatial_freqs)[None, None, :, :].repeat(
+                                pe_size[0], pe_size[1], 1, 1)
+
+        # Apply sequence scaling in temporal dimension
+        if fps is None:
+            # Images
+            emb_t = torch.outer(seq[:pe_size[0]], temporal_freqs)
+        else:
+            # Videos
+            emb_t = torch.outer(seq[:pe_size[0]] / fps * self.base_fps,
+                                temporal_freqs)
+
+        emb_t = emb_t[:, None, None, :].repeat(1, pe_size[1], pe_size[2], 1)
+        freqs = torch.cat([emb_t, emb_h, emb_w] * 2, dim=-1).flatten(0,
+                                                                     2).float()
+        cos = torch.cos(freqs)
+        sin = torch.sin(freqs)
+        return cos, sin
+
+
+class CosmosLearnablePositionalEmbed(nn.Module):
+
+    def __init__(
+        self,
+        hidden_size: int,
+        max_size: tuple[int, int, int],
+        patch_size: tuple[int, int, int],
+        eps: float = 1e-6,
+    ) -> None:
+        super().__init__()
+
+        self.max_size = [
+            size // patch
+            for size, patch in zip(max_size, patch_size, strict=False)
+        ]
+        self.patch_size = patch_size
+        self.eps = eps
+
+        self.pos_emb_t = nn.Parameter(torch.zeros(self.max_size[0],
+                                                  hidden_size))
+        self.pos_emb_h = nn.Parameter(torch.zeros(self.max_size[1],
+                                                  hidden_size))
+        self.pos_emb_w = nn.Parameter(torch.zeros(self.max_size[2],
+                                                  hidden_size))
+
+    def forward(self, hidden_states: torch.Tensor) -> torch.Tensor:
+        batch_size, num_channels, num_frames, height, width = hidden_states.shape
+        pe_size = [
+            num_frames // self.patch_size[0], height // self.patch_size[1],
+            width // self.patch_size[2]
+        ]
+
+        emb_t = self.pos_emb_t[:pe_size[0]][None, :, None, None, :].repeat(
+            batch_size, 1, pe_size[1], pe_size[2], 1)
+        emb_h = self.pos_emb_h[:pe_size[1]][None, None, :, None, :].repeat(
+            batch_size, pe_size[0], 1, pe_size[2], 1)
+        emb_w = self.pos_emb_w[:pe_size[2]][None, None, None, :, :].repeat(
+            batch_size, pe_size[0], pe_size[1], 1, 1)
+        emb = emb_t + emb_h + emb_w
+        emb = emb.flatten(1, 3)
+
+        norm = torch.linalg.vector_norm(emb,
+                                        dim=-1,
+                                        keepdim=True,
+                                        dtype=torch.float32)
+        norm = torch.add(self.eps,
+                         norm,
+                         alpha=np.sqrt(norm.numel() / emb.numel()))
+        return (emb / norm).type_as(hidden_states)
+
+
+class CosmosTransformer3DModel(BaseDiT):
+    _fsdp_shard_conditions = CosmosConfig()._fsdp_shard_conditions
+    _compile_conditions = CosmosConfig()._compile_conditions
+    _supported_attention_backends = CosmosConfig()._supported_attention_backends
+    _param_names_mapping = CosmosConfig()._param_names_mapping
+    _lora_param_names_mapping = CosmosConfig()._lora_param_names_mapping
+
+    def __init__(self, config: CosmosConfig, hf_config: dict[str, Any]) -> None:
+        super().__init__(config=config, hf_config=hf_config)
+
+        inner_dim = config.num_attention_heads * config.attention_head_dim
+        self.hidden_size = config.hidden_size
+        self.num_attention_heads = config.num_attention_heads
+        self.in_channels = config.in_channels
+        self.out_channels = config.out_channels
+        self.num_channels_latents = config.num_channels_latents
+        self.patch_size = config.patch_size
+        self.max_size = config.max_size
+        self.rope_scale = config.rope_scale
+        self.concat_padding_mask = config.concat_padding_mask
+        self.extra_pos_embed_type = config.extra_pos_embed_type
+
+        # 1. Patch Embedding
+        patch_embed_in_channels = config.in_channels + 1 if config.concat_padding_mask else config.in_channels
+        self.patch_embed = CosmosPatchEmbed(patch_embed_in_channels,
+                                            inner_dim,
+                                            config.patch_size,
+                                            bias=False)
+
+        # 2. Positional Embedding
+        self.rope = CosmosRotaryPosEmbed(hidden_size=config.attention_head_dim,
+                                         max_size=config.max_size,
+                                         patch_size=config.patch_size,
+                                         rope_scale=config.rope_scale)
+
+        self.learnable_pos_embed = None
+        if config.extra_pos_embed_type == "learnable":
+            self.learnable_pos_embed = CosmosLearnablePositionalEmbed(
+                hidden_size=inner_dim,
+                max_size=config.max_size,
+                patch_size=config.patch_size,
+            )
+
+        # 3. Time Embedding
+        self.time_embed = CosmosEmbedding(inner_dim, inner_dim)
+
+        # 4. Transformer Blocks
+        self.transformer_blocks = nn.ModuleList([
+            CosmosTransformerBlock(
+                num_attention_heads=config.num_attention_heads,
+                attention_head_dim=config.attention_head_dim,
+                cross_attention_dim=config.text_embed_dim,
+                mlp_ratio=config.mlp_ratio,
+                adaln_lora_dim=config.adaln_lora_dim,
+                qk_norm=config.qk_norm,
+                out_bias=False,
+                supported_attention_backends=self._supported_attention_backends,
+                prefix=f"{config.prefix}.transformer_blocks.{i}",
+            ) for i in range(config.num_layers)
+        ])
+
+        # 5. Output norm & projection
+        self.norm_out = CosmosAdaLayerNorm(inner_dim, config.adaln_lora_dim)
+        self.proj_out = nn.Linear(inner_dim,
+                                  config.out_channels *
+                                  math.prod(config.patch_size),
+                                  bias=False)
+
+        self.gradient_checkpointing = False
+
+        # For TeaCache
+        self.previous_e0_even = None
+        self.previous_e0_odd = None
+        self.previous_residual_even = None
+        self.previous_residual_odd = None
+        self.is_even = True
+        self.should_calc_even = True
+        self.should_calc_odd = True
+        self.accumulated_rel_l1_distance_even = 0
+        self.accumulated_rel_l1_distance_odd = 0
+        self.cnt = 0
+        self.__post_init__()
+
+    def forward(self,
+                hidden_states: torch.Tensor,
+                timestep: torch.Tensor,
+                encoder_hidden_states: torch.Tensor | list[torch.Tensor],
+                attention_mask: torch.Tensor | None = None,
+                fps: int | None = None,
+                condition_mask: torch.Tensor | None = None,
+                padding_mask: torch.Tensor | None = None,
+                **kwargs) -> torch.Tensor:
+        forward_batch = get_forward_context().forward_batch
+        enable_teacache = forward_batch is not None and forward_batch.enable_teacache
+
+        orig_dtype = hidden_states.dtype
+        if not isinstance(encoder_hidden_states, torch.Tensor):
+            encoder_hidden_states = encoder_hidden_states[0]
+
+        batch_size, num_channels, num_frames, height, width = hidden_states.shape
+
+        # 1. Concatenate padding mask if needed & prepare attention mask
+        if condition_mask is not None:
+            hidden_states = torch.cat([hidden_states, condition_mask], dim=1)
+
+        if self.concat_padding_mask and padding_mask is not None:
+            from torchvision import transforms
+            padding_mask = transforms.functional.resize(
+                padding_mask,
+                list(hidden_states.shape[-2:]),
+                interpolation=transforms.InterpolationMode.NEAREST)
+            hidden_states = torch.cat([
+                hidden_states,
+                padding_mask.unsqueeze(2).repeat(batch_size, 1, num_frames, 1,
+                                                 1)
+            ],
+                                      dim=1)
+            # # Resize padding mask to match hidden states spatial dimensions
+            # padding_mask_resized = F.interpolate(
+            #     padding_mask.float().unsqueeze(1),
+            #     size=(height, width),
+            #     mode='nearest'
+            # ).squeeze(1)
+            # hidden_states = torch.cat(
+            #     [hidden_states, padding_mask_resized.unsqueeze(1).unsqueeze(2).repeat(1, 1, num_frames, 1, 1)], dim=1
+            # )
+
+        if attention_mask is not None:
+            attention_mask = attention_mask.unsqueeze(1).unsqueeze(
+                1)  # [B, 1, 1, S]
+
+        # 2. Generate positional embeddings
+        image_rotary_emb = self.rope(hidden_states, fps=fps)
+        extra_pos_emb = self.learnable_pos_embed(
+            hidden_states) if self.extra_pos_embed_type == "learnable" else None
+
+        # 3. Patchify input
+        p_t, p_h, p_w = self.patch_size
+        post_patch_num_frames = num_frames // p_t
+        post_patch_height = height // p_h
+        post_patch_width = width // p_w
+        hidden_states = self.patch_embed(hidden_states)
+        hidden_states = hidden_states.flatten(
+            1, 3)  # [B, T, H, W, C] -> [B, THW, C] codespell:ignore
+
+        # 4. Timestep embeddings
+        if timestep.ndim == 1:
+            temb, embedded_timestep = self.time_embed(hidden_states, timestep)
+        elif timestep.ndim == 5:
+            assert timestep.shape == (batch_size, 1, num_frames, 1, 1), (
+                f"Expected timestep to have shape [B, 1, T, 1, 1], but got {timestep.shape}"
+            )
+            timestep = timestep.flatten()
+            temb, embedded_timestep = self.time_embed(hidden_states, timestep)
+            # We can do this because num_frames == post_patch_num_frames, as p_t is 1
+            temb, embedded_timestep = (
+                x.view(batch_size, post_patch_num_frames, 1, 1,
+                       -1).expand(-1, -1, post_patch_height, post_patch_width,
+                                  -1).flatten(1, 3)
+                for x in (temb, embedded_timestep)
+            )  # [BT, C] -> [B, T, 1, 1, C] -> [B, T, H, W, C] -> [B, THW, C] codespell:ignore
+        else:
+            raise ValueError(f"Unsupported timestep shape: {timestep.shape}")
+
+        # 6. Transformer blocks
+        if torch.is_grad_enabled() and self.gradient_checkpointing:
+            for block in self.transformer_blocks:
+                hidden_states = self._gradient_checkpointing_func(
+                    block,
+                    hidden_states,
+                    encoder_hidden_states,
+                    embedded_timestep,
+                    temb,
+                    image_rotary_emb,
+                    extra_pos_emb,
+                    attention_mask,
+                )
+        else:
+            for block in self.transformer_blocks:
+                hidden_states = block(
+                    hidden_states=hidden_states,
+                    encoder_hidden_states=encoder_hidden_states,
+                    embedded_timestep=embedded_timestep,
+                    temb=temb,
+                    image_rotary_emb=image_rotary_emb,
+                    extra_pos_emb=extra_pos_emb,
+                    attention_mask=attention_mask,
+                )
+
+        # 7. Output norm & projection & unpatchify
+        hidden_states = self.norm_out(hidden_states, embedded_timestep, temb)
+        hidden_states = self.proj_out(hidden_states)
+        hidden_states = hidden_states.unflatten(2, (p_h, p_w, p_t, -1))
+        hidden_states = hidden_states.unflatten(
+            1, (post_patch_num_frames, post_patch_height, post_patch_width))
+        # NOTE: The permutation order here is not the inverse operation of what happens when patching as usually expected.
+        # It might be a source of confusion to the reader, but this is correct
+        hidden_states = hidden_states.permute(0, 7, 1, 6, 2, 4, 3, 5)
+        hidden_states = hidden_states.flatten(6, 7).flatten(4, 5).flatten(2, 3)
+
+        return hidden_states

fastvideo/v1/models/registry.py

@@ -23,7 +23,8 @@ _TEXT_TO_VIDEO_DIT_MODELS = {
     "HunyuanVideoTransformer3DModel":
     ("dits", "hunyuanvideo", "HunyuanVideoTransformer3DModel"),
     "WanTransformer3DModel": ("dits", "wanvideo", "WanTransformer3DModel"),
-    "StepVideoModel": ("dits", "stepvideo", "StepVideoModel")
+    "StepVideoModel": ("dits", "stepvideo", "StepVideoModel"),
+    "CosmosTransformer3DModel": ("dits", "cosmos", "CosmosTransformer3DModel")
 }
 
 _IMAGE_TO_VIDEO_DIT_MODELS = {

fastvideo/v1/tests/transformers/test_cosmos2.py

@@ -0,0 +1,222 @@
+# SPDX-License-Identifier: Apache-2.0
+import os
+
+import numpy as np
+import pytest
+import torch
+from diffusers import CosmosTransformer3DModel
+
+from fastvideo.v1.configs.pipelines import PipelineConfig
+from fastvideo.v1.forward_context import set_forward_context
+from fastvideo.v1.fastvideo_args import FastVideoArgs
+from fastvideo.v1.logger import init_logger
+from fastvideo.v1.models.loader.component_loader import TransformerLoader
+from fastvideo.v1.utils import maybe_download_model
+from fastvideo.v1.configs.models.dits import CosmosConfig
+from fastvideo.v1.pipelines.pipeline_batch_info import ForwardBatch
+
+
+logger = init_logger(__name__)
+
+os.environ["MASTER_ADDR"] = "localhost"
+os.environ["MASTER_PORT"] = "29504"
+
+BASE_MODEL_PATH = "nvidia/Cosmos-Predict2-2B-Text2Image"
+MODEL_PATH = maybe_download_model(BASE_MODEL_PATH,
+                                  local_dir=os.path.join(
+                                      'data', BASE_MODEL_PATH))
+TRANSFORMER_PATH = os.path.join(MODEL_PATH, "transformer")
+
+
+@pytest.mark.usefixtures("distributed_setup")
+def test_cosmos2_transformer():
+    device = torch.device("cuda:0" if torch.cuda.is_available() else "cpu")
+    precision = torch.bfloat16
+    precision_str = "bf16"
+    args = FastVideoArgs(model_path=TRANSFORMER_PATH,
+                         use_cpu_offload=False,
+                         pipeline_config=PipelineConfig(dit_config=CosmosConfig(), dit_precision=precision_str))
+    args.device = device
+
+    loader = TransformerLoader()
+    model2 = loader.load(TRANSFORMER_PATH, "", args).to(device, dtype=precision)
+
+    model1 = CosmosTransformer3DModel.from_pretrained(
+        TRANSFORMER_PATH, device=device,
+        torch_dtype=precision).to(device, dtype=precision).requires_grad_(False)
+
+    total_params = sum(p.numel() for p in model1.parameters())
+    # Calculate weight sum for model1 (converting to float64 to avoid overflow)
+    weight_sum_model1 = sum(
+        p.to(torch.float64).sum().item() for p in model1.parameters())
+    # Also calculate mean for more stable comparison
+    weight_mean_model1 = weight_sum_model1 / total_params
+    logger.info("Model 1 weight sum: %s", weight_sum_model1)
+    logger.info("Model 1 weight mean: %s", weight_mean_model1)
+
+    # Calculate weight sum for model2 (converting to float64 to avoid overflow)
+    total_params_model2 = sum(p.numel() for p in model2.parameters())
+    weight_sum_model2 = sum(
+        p.to(torch.float64).sum().item() for p in model2.parameters())
+    # Also calculate mean for more stable comparison
+    weight_mean_model2 = weight_sum_model2 / total_params_model2
+    logger.info("Model 2 weight sum: %s", weight_sum_model2)
+    logger.info("Model 2 weight mean: %s", weight_mean_model2)
+
+    weight_sum_diff = abs(weight_sum_model1 - weight_sum_model2)
+    logger.info("Weight sum difference: %s", weight_sum_diff)
+    weight_mean_diff = abs(weight_mean_model1 - weight_mean_model2)
+    logger.info("Weight mean difference: %s", weight_mean_diff)
+
+    # Set both models to eval mode
+    model1 = model1.eval()
+    model2 = model2.eval()
+
+    # Create identical inputs for both models
+    batch_size = 1
+    seq_len = 30
+
+    # Video latents [B, C, T, H, W] - Cosmos2 specific dimensions
+    hidden_states = torch.randn(batch_size,
+                                16,
+                                1,  # Single frame for image generation
+                                32,  # Height patches
+                                32,  # Width patches
+                                device=device,
+                                dtype=precision)
+
+    # Text embeddings [B, L, D] - Cosmos2 uses T5 embeddings with 1024 dim
+    encoder_hidden_states = torch.randn(batch_size,
+                                        seq_len,
+                                        1024,  # T5 embedding dimension
+                                        device=device,
+                                        dtype=precision)
+
+    # Timestep
+    timestep = torch.tensor([500], device=device, dtype=precision)
+
+    # padding mask
+    padding_mask = hidden_states.new_zeros(1, 1, 32, 32, device=device, dtype=precision)
+    # print(padding_mask.shape)
+
+    forward_batch = ForwardBatch(
+        data_type="dummy",
+    )
+
+    with torch.amp.autocast('cuda', dtype=precision):
+        output1 = model1(
+            hidden_states=hidden_states,
+            encoder_hidden_states=encoder_hidden_states,
+            timestep=timestep,
+            padding_mask=padding_mask,
+            return_dict=False,
+        )[0]
+        with set_forward_context(
+                current_timestep=0,
+                attn_metadata=None,
+                forward_batch=forward_batch,
+        ):
+            output2 = model2(hidden_states=hidden_states,
+                             encoder_hidden_states=encoder_hidden_states,
+                             timestep=timestep,
+                             padding_mask=padding_mask)
+
+    # Check if outputs have the same shape
+    assert output1.shape == output2.shape, f"Output shapes don't match: {output1.shape} vs {output2.shape}"
+    assert output1.dtype == output2.dtype, f"Output dtype don't match: {output1.dtype} vs {output2.dtype}"
+
+    # Check if outputs are similar (allowing for small numerical differences)
+    max_diff = torch.max(torch.abs(output1 - output2))
+    mean_diff = torch.mean(torch.abs(output1 - output2))
+    logger.info("Max Diff: %s", max_diff.item())
+    logger.info("Mean Diff: %s", mean_diff.item())
+    assert max_diff < 1e-1, f"Maximum difference between outputs: {max_diff.item()}"
+    # mean diff
+    assert mean_diff < 1e-2, f"Mean difference between outputs: {mean_diff.item()}"
+
+
+@pytest.mark.usefixtures("distributed_setup")
+def test_cosmos2_transformer_video2world():
+    """Test Cosmos2 Video2World variant"""
+    device = torch.device("cuda:0" if torch.cuda.is_available() else "cpu")
+    precision = torch.bfloat16
+    precision_str = "bf16"
+    
+    # Use Video2World model path
+    base_model_path = "nvidia/Cosmos-Predict2-2B-Video2World"
+    model_path = maybe_download_model(base_model_path,
+                                      local_dir=os.path.join(
+                                          'data', base_model_path))
+    transformer_path = os.path.join(model_path, "transformer")
+    
+    args = FastVideoArgs(model_path=transformer_path,
+                         use_cpu_offload=False,
+                         pipeline_config=PipelineConfig(dit_config=CosmosConfig(), dit_precision=precision_str))
+    args.device = device
+
+    loader = TransformerLoader()
+    model2 = loader.load(transformer_path, "", args).to(device, dtype=precision)
+
+    model1 = CosmosTransformer3DModel.from_pretrained(
+        transformer_path, device=device,
+        torch_dtype=precision).to(device, dtype=precision).requires_grad_(False)
+
+    # Set both models to eval mode
+    model1 = model1.eval()
+    model2 = model2.eval()
+
+    # Create identical inputs for both models
+    batch_size = 1
+    seq_len = 30
+
+    # Video latents [B, C, T, H, W] - Video2World has additional condition channel
+    hidden_states = torch.randn(batch_size,
+                                17,  # 16 + 1 for condition channel
+                                8,   # Multiple frames for video
+                                32,  # Height patches
+                                32,  # Width patches
+                                device=device,
+                                dtype=precision)
+
+    # Text embeddings [B, L, D]
+    encoder_hidden_states = torch.randn(batch_size,
+                                        seq_len,
+                                        1024,  # T5 embedding dimension
+                                        device=device,
+                                        dtype=precision)
+
+    # Timestep
+    timestep = torch.tensor([500], device=device, dtype=precision)
+
+    forward_batch = ForwardBatch(
+        data_type="dummy",
+    )
+
+    with torch.amp.autocast('cuda', dtype=precision):
+        output1 = model1(
+            hidden_states=hidden_states,
+            encoder_hidden_states=encoder_hidden_states,
+            timestep=timestep,
+            return_dict=False,
+        )[0]
+        with set_forward_context(
+                current_timestep=0,
+                attn_metadata=None,
+                forward_batch=forward_batch,
+        ):
+            output2 = model2(hidden_states=hidden_states,
+                             encoder_hidden_states=encoder_hidden_states,
+                             timestep=timestep)
+
+    # Check if outputs have the same shape
+    assert output1.shape == output2.shape, f"Output shapes don't match: {output1.shape} vs {output2.shape}"
+    assert output1.dtype == output2.dtype, f"Output dtype don't match: {output1.dtype} vs {output2.dtype}"
+
+    # Check if outputs are similar (allowing for small numerical differences)
+    max_diff = torch.max(torch.abs(output1 - output2))
+    mean_diff = torch.mean(torch.abs(output1 - output2))
+    logger.info("Max Diff: %s", max_diff.item())
+    logger.info("Mean Diff: %s", mean_diff.item())
+    assert max_diff < 1e-1, f"Maximum difference between outputs: {max_diff.item()}"
+    # mean diff
+    assert mean_diff < 1e-2, f"Mean difference between outputs: {mean_diff.item()}"