diff --git a/tests/diffusion/models/cosmos3/test_cosmos3_pipeline.py b/tests/diffusion/models/cosmos3/test_cosmos3_pipeline.py
index e73dd7ff6..52762cbf7 100644
--- a/tests/diffusion/models/cosmos3/test_cosmos3_pipeline.py
+++ b/tests/diffusion/models/cosmos3/test_cosmos3_pipeline.py
@@ -1121,7 +1121,7 @@ def test_pipeline_init_passes_tokenizer_attrs_into_transformer(
 def test_preprocess_i2v_image_and_action_video_inputs() -> None:
     from vllm_omni.diffusion.models.cosmos3.pipeline_cosmos3 import get_cosmos3_pre_process_func
 
-    preprocess = get_cosmos3_pre_process_func(SimpleNamespace())
+    preprocess = get_cosmos3_pre_process_func(SimpleNamespace(model_config={"guardrails": False}, tf_model_config=None))
     i2v = SimpleNamespace(
         prompt={"prompt": "A slow camera push.", "multi_modal_data": {"image": Image.new("RGB", (320, 160))}},
         sampling_params=make_sampling_params(height=None, width=None, extra_args={}),
@@ -1155,6 +1155,130 @@ def test_preprocess_i2v_image_and_action_video_inputs() -> None:
     assert additional["condition_frame_indexes_vision"] == [0, 1]
 
 
+def test_preprocess_v2v_decodes_uploaded_video_path(tmp_path) -> None:
+    """Serving may pass multipart uploads as /tmp/...mp4 path lists (#8073)."""
+    imageio = pytest.importorskip("imageio.v3")
+
+    from vllm_omni.diffusion.models.cosmos3.pipeline_cosmos3 import get_cosmos3_pre_process_func
+
+    frames = [np.full((16, 32, 3), i * 40, dtype=np.uint8) for i in range(6)]
+    video_path = tmp_path / "vllm_omni_video_reference_test.mp4"
+    imageio.imwrite(video_path, frames, fps=4, codec="libx264")
+
+    preprocess = get_cosmos3_pre_process_func(SimpleNamespace(model_config={"guardrails": False}, tf_model_config=None))
+    request = SimpleNamespace(
+        prompt={"prompt": "Continue.", "multi_modal_data": {"video": [str(video_path)]}},
+        sampling_params=make_sampling_params(
+            height=16,
+            width=32,
+            extra_args={"condition_frame_indexes_vision": [0, 1], "condition_video_keep": "first"},
+        ),
+    )
+
+    additional = preprocess(request).prompt["additional_information"]
+    # condition_frame_indexes_vision=[0,1] => 5 pixel frames after VAE indexing.
+    assert tuple(additional["preprocessed_video"].shape) == (1, 3, 5, 16, 32)
+    assert additional["condition_frame_indexes_vision"] == [0, 1]
+
+
+def test_decode_path_video_frames_honors_max_frames_and_keep(tmp_path, monkeypatch: pytest.MonkeyPatch) -> None:
+    pytest.importorskip("imageio.v3")
+    import imageio.v3 as iio
+
+    from vllm_omni.diffusion.utils.video_decode import decode_path_video_frames
+
+    source = tmp_path / "clip.mp4"
+    source.write_bytes(b"placeholder")
+    seen = {"n": 0}
+
+    def fake_imiter(_path):
+        for idx in range(20):
+            seen["n"] += 1
+            yield np.full((4, 4, 3), idx, dtype=np.uint8)
+
+    monkeypatch.setattr(iio, "imiter", fake_imiter)
+
+    first = decode_path_video_frames(source, max_frames=5, keep="first")
+    assert len(first) == 5
+    assert seen["n"] == 5
+    assert first[0][0, 0, 0] == 0
+    assert first[-1][0, 0, 0] == 4
+
+    seen["n"] = 0
+    last = decode_path_video_frames(source, max_frames=5, keep="last")
+    assert len(last) == 5
+    assert seen["n"] == 20
+    assert last[0][0, 0, 0] == 15
+    assert last[-1][0, 0, 0] == 19
+
+
+def test_preprocess_v2v_video_path_honors_prompt_level_keep_and_indexes(
+    tmp_path, monkeypatch: pytest.MonkeyPatch
+) -> None:
+    pytest.importorskip("imageio.v3")
+    import imageio.v3 as iio
+
+    from vllm_omni.diffusion.models.cosmos3 import pipeline_cosmos3 as cosmos_pipeline
+    from vllm_omni.diffusion.models.cosmos3.pipeline_cosmos3 import get_cosmos3_pre_process_func
+    from vllm_omni.diffusion.utils.video_decode import decode_path_video_frames
+
+    source = tmp_path / "vllm_omni_video_reference_prompt.mp4"
+    source.write_bytes(b"placeholder")
+    captured: dict[str, Any] = {}
+
+    def fake_imiter(_path):
+        for idx in range(20):
+            yield np.full((16, 32, 3), idx, dtype=np.uint8)
+
+    def spy_decode(*args, **kwargs):
+        frames = decode_path_video_frames(*args, **kwargs)
+        captured["keep"] = kwargs.get("keep")
+        captured["max_frames"] = kwargs.get("max_frames")
+        captured["n"] = len(frames)
+        captured["first"] = int(frames[0][0, 0, 0])
+        captured["last"] = int(frames[-1][0, 0, 0])
+        return frames
+
+    monkeypatch.setattr(iio, "imiter", fake_imiter)
+    monkeypatch.setattr(cosmos_pipeline, "decode_path_video_frames", spy_decode)
+
+    preprocess = get_cosmos3_pre_process_func(SimpleNamespace(model_config={"guardrails": False}, tf_model_config=None))
+    last_keep = SimpleNamespace(
+        prompt={
+            "prompt": "Continue.",
+            "condition_video_keep": "last",
+            "condition_frame_indexes_vision": [0, 1],
+            "multi_modal_data": {"video": [str(source)]},
+        },
+        sampling_params=make_sampling_params(height=16, width=32, extra_args={}),
+    )
+    additional = preprocess(last_keep).prompt["additional_information"]
+    assert captured["keep"] == "last"
+    assert captured["max_frames"] == 5
+    assert captured["n"] == 5
+    assert captured["first"] == 15
+    assert captured["last"] == 19
+    assert tuple(additional["preprocessed_video"].shape) == (1, 3, 5, 16, 32)
+    assert additional["condition_frame_indexes_vision"] == [0, 1]
+
+    wider_indexes = SimpleNamespace(
+        prompt={
+            "prompt": "Continue.",
+            "condition_frame_indexes_vision": [0, 1, 2],
+            "multi_modal_data": {"video": [str(source)]},
+        },
+        sampling_params=make_sampling_params(height=16, width=32, extra_args={}),
+    )
+    additional = preprocess(wider_indexes).prompt["additional_information"]
+    assert captured["keep"] == "first"
+    assert captured["max_frames"] == 9
+    assert captured["n"] == 9
+    assert captured["first"] == 0
+    assert captured["last"] == 8
+    assert tuple(additional["preprocessed_video"].shape) == (1, 3, 9, 16, 32)
+    assert additional["condition_frame_indexes_vision"] == [0, 1, 2]
+
+
 def test_transfer_config_media_helpers_and_preprocess_budget(monkeypatch: pytest.MonkeyPatch) -> None:
     from vllm_omni.diffusion.models.cosmos3 import transfer
     from vllm_omni.diffusion.models.cosmos3.pipeline_cosmos3 import (
@@ -1224,7 +1348,7 @@ def test_transfer_config_media_helpers_and_preprocess_budget(monkeypatch: pytest
     )
     assert tuple(loaded.shape) == (3, 2, 8, 8)
 
-    preprocess = get_cosmos3_pre_process_func(SimpleNamespace())
+    preprocess = get_cosmos3_pre_process_func(SimpleNamespace(model_config={"guardrails": False}, tf_model_config=None))
 
     class FramesWithFps(list):
         fps = 12.5
diff --git a/vllm_omni/diffusion/models/cosmos3/pipeline_cosmos3.py b/vllm_omni/diffusion/models/cosmos3/pipeline_cosmos3.py
index 95ba4767f..7a7de7d70 100644
--- a/vllm_omni/diffusion/models/cosmos3/pipeline_cosmos3.py
+++ b/vllm_omni/diffusion/models/cosmos3/pipeline_cosmos3.py
@@ -72,6 +72,7 @@ from vllm_omni.diffusion.models.schedulers.scheduling_flow_unipc_multistep impor
 from vllm_omni.diffusion.offloader.config import OffloadStrategy, resolve_offload
 from vllm_omni.diffusion.profiler.diffusion_pipeline_profiler import DiffusionPipelineProfilerMixin
 from vllm_omni.diffusion.request import OmniDiffusionRequest
+from vllm_omni.diffusion.utils.video_decode import decode_path_video_frames, is_video_file_path
 from vllm_omni.diffusion.worker.request_batch import DiffusionRequestBatch
 from vllm_omni.entrypoints.openai.video_api_utils import positive_float
 from vllm_omni.experimental.world_models.adapters.state_cosmos3_adapter import (
@@ -465,10 +466,39 @@ def get_cosmos3_pre_process_func(od_config: OmniDiffusionConfig):
                     return nested
         return video
 
-    def _video_payload_to_frames(video: Any) -> list[Any]:
+    def _decode_video_file_to_frames(
+        path: str | os.PathLike,
+        *,
+        max_frames: int | None,
+        keep: str,
+    ) -> list[PIL.Image.Image]:
+        rgb_frames = decode_path_video_frames(path, max_frames=max_frames, keep=keep)
+        return [PIL.Image.fromarray(frame).convert("RGB") for frame in rgb_frames]
+
+    def _expand_video_payload_item(
+        item: Any,
+        *,
+        max_frames: int | None,
+        keep: str,
+    ) -> list[Any]:
+        if is_video_file_path(item):
+            return _decode_video_file_to_frames(item, max_frames=max_frames, keep=keep)
+        return [item]
+
+    def _video_payload_to_frames(
+        video: Any,
+        *,
+        max_frames: int | None,
+        keep: str,
+    ) -> list[Any]:
         video = _unwrap_video_payload(video)
+        if is_video_file_path(video):
+            return _decode_video_file_to_frames(video, max_frames=max_frames, keep=keep)
         if isinstance(video, list):
-            return video
+            frames: list[Any] = []
+            for item in video:
+                frames.extend(_expand_video_payload_item(item, max_frames=max_frames, keep=keep))
+            return frames
         if isinstance(video, torch.Tensor):
             tensor = video.detach().cpu()
             if tensor.ndim == 5:
@@ -531,11 +561,31 @@ def get_cosmos3_pre_process_func(od_config: OmniDiffusionConfig):
         if "additional_information" not in prompt:
             prompt["additional_information"] = {}
 
+        extra = _extra_args(request)
+        transfer_requested = action_mode is None and has_transfer_hints(extra)
+        condition_frame_indexes_vision = normalize_condition_frame_indexes_vision(
+            extra.get("condition_frame_indexes_vision", prompt.get("condition_frame_indexes_vision"))
+        )
+        condition_video_keep = normalize_condition_video_keep(
+            extra.get("condition_video_keep", prompt.get("condition_video_keep"))
+        )
+
         raw_video_frames: list[Any] | None = None
         transfer_input_fps: float | None = None
         if raw_video is not None:
             transfer_input_fps = _video_payload_fps(raw_video)
-            raw_video_frames = _video_payload_to_frames(raw_video)
+            decode_extra = dict(extra)
+            decode_extra["condition_frame_indexes_vision"] = list(condition_frame_indexes_vision)
+            decode_extra["condition_video_keep"] = condition_video_keep
+            decode_spec = Cosmos3OmniDiffusersPipeline.reference_video_decode_spec(
+                num_frames=getattr(request.sampling_params, "num_frames", None),
+                extra_args=decode_extra,
+            )
+            raw_video_frames = _video_payload_to_frames(
+                raw_video,
+                max_frames=decode_spec.max_frames,
+                keep=decode_spec.keep,
+            )
             if not raw_video_frames:
                 raise TypeError("Cosmos3 video input must be a non-empty list of PIL images or image paths.")
 
@@ -544,8 +594,6 @@ def get_cosmos3_pre_process_func(od_config: OmniDiffusionConfig):
             image = _pil_to_rgb(raw_video_frames[0])
         else:
             image = _pil_to_rgb(raw_image)
-        extra = _extra_args(request)
-        transfer_requested = action_mode is None and has_transfer_hints(extra)
 
         # Resolve missing H/W.
         if transfer_requested:
@@ -610,22 +658,13 @@ def get_cosmos3_pre_process_func(od_config: OmniDiffusionConfig):
                     dtype=torch.float32,
                 )
             else:
-                condition_frame_indexes_vision = normalize_condition_frame_indexes_vision(
-                    extra.get(
-                        "condition_frame_indexes_vision",
-                        prompt.get("condition_frame_indexes_vision"),
-                    )
-                )
-                keep = normalize_condition_video_keep(
-                    extra.get("condition_video_keep", prompt.get("condition_video_keep"))
-                )
                 max_frames = condition_pixel_frame_count(condition_frame_indexes_vision)
                 prompt["additional_information"]["preprocessed_video"] = _preprocess_condition_video(
                     raw_video_frames,
                     int(target_h),
                     int(target_w),
                     max_frames,
-                    keep,
+                    condition_video_keep,
                 )
                 prompt["additional_information"]["condition_frame_indexes_vision"] = list(
                     condition_frame_indexes_vision
diff --git a/vllm_omni/diffusion/models/cosmos3/transfer.py b/vllm_omni/diffusion/models/cosmos3/transfer.py
index 65bbbcef8..730a0d44e 100644
--- a/vllm_omni/diffusion/models/cosmos3/transfer.py
+++ b/vllm_omni/diffusion/models/cosmos3/transfer.py
@@ -1,5 +1,5 @@
 # SPDX-License-Identifier: Apache-2.0
-# SPDX-FileCopyrightText: Copyright contributors to the vLLM project
+# SPDX-FileCopyrightText: Copyright contributors to the vLLM-Omni project
 """Cosmos3 transfer inference helpers.
 
 The reference Cosmos Framework transfer path accepts one or more control hints
@@ -25,6 +25,8 @@ import PIL.Image
 import torch
 import torch.nn.functional as F
 
+from vllm_omni.diffusion.utils.video_decode import decode_path_video_frames
+
 TRANSFER_HINT_KEYS: tuple[str, ...] = ("edge", "blur", "depth", "seg", "wsm")
 _TRANSFER_HINT_COMMON_FIELDS = frozenset({"control_path", "control", "control_weight"})
 _TRANSFER_HINT_FIELDS: dict[str, frozenset[str]] = {
@@ -538,23 +540,9 @@ def _path_media_to_uint8_cthw(path: str | Path, max_frames: int | None) -> torch
         array = _pil_to_uint8_rgb(media_path)
         return torch.from_numpy(array).permute(2, 0, 1).unsqueeze(1).contiguous()
 
-    try:
-        import imageio.v3 as iio
-    except ImportError as exc:
-        raise ImportError(
-            "Cosmos3 transfer video control_path loading requires imageio. "
-            "Install imageio[ffmpeg] or provide decoded control frames."
-        ) from exc
-
-    frames: list[torch.Tensor] = []
-    limit = max_frames if max_frames is not None else None
-    for frame in iio.imiter(media_path):
-        frames.append(torch.from_numpy(_pil_to_uint8_rgb(frame)).permute(2, 0, 1))
-        if limit is not None and len(frames) >= int(limit):
-            break
-    if not frames:
-        raise ValueError(f"Cosmos3 transfer control_path produced no frames: {media_path}")
-    return torch.stack(frames, dim=1).contiguous()
+    rgb_frames = decode_path_video_frames(media_path, max_frames=max_frames, keep="first")
+    stacked = [torch.from_numpy(frame).permute(2, 0, 1) for frame in rgb_frames]
+    return torch.stack(stacked, dim=1).contiguous()
 
 
 def media_to_uint8_cthw(value: Any, *, height: int, width: int, max_frames: int | None = None) -> torch.Tensor:
diff --git a/vllm_omni/diffusion/utils/video_decode.py b/vllm_omni/diffusion/utils/video_decode.py
new file mode 100644
index 000000000..888759230
--- /dev/null
+++ b/vllm_omni/diffusion/utils/video_decode.py
@@ -0,0 +1,91 @@
+# SPDX-License-Identifier: Apache-2.0
+# SPDX-FileCopyrightText: Copyright contributors to the vLLM-Omni project
+"""Decode video file paths to RGB frames.
+
+Path suffix checks and bounded first/last-N imageio decoding. Model-specific
+conditioning and decode-budget stay in each pipeline's preprocess layer.
+
+Currently used by Cosmos3 V2V preprocess and transfer ``control_path``.
+Unifying with ``OmniVideoBackend`` / ``_decode_video_bytes`` is a follow-up.
+"""
+
+from __future__ import annotations
+
+import os
+from collections import deque
+from pathlib import Path
+from typing import Any, Literal
+
+import numpy as np
+import PIL.Image
+
+VIDEO_EXTENSIONS = {".avi", ".m4v", ".mkv", ".mov", ".mp4", ".webm"}
+
+
+def is_video_file_path(value: Any) -> bool:
+    """True when ``value`` is a filesystem path with a known video suffix.
+
+    Serving may leave uploaded references as temp paths such as
+    ``/tmp/vllm_omni_video_reference_*.mp4`` instead of decoded frames.
+    """
+    if not isinstance(value, str | os.PathLike):
+        return False
+    suffix = os.path.splitext(os.fspath(value))[1].lower()
+    return suffix in VIDEO_EXTENSIONS
+
+
+def _frame_to_uint8_rgb(value: Any) -> np.ndarray:
+    if isinstance(value, PIL.Image.Image):
+        return np.array(value.convert("RGB"), dtype=np.uint8, copy=True)
+    if isinstance(value, np.ndarray):
+        array = value
+        if array.ndim == 3 and array.shape[0] in (3, 4) and array.shape[-1] not in (3, 4):
+            array = np.transpose(array[:3], (1, 2, 0))
+        if np.issubdtype(array.dtype, np.floating):
+            if array.size and (array.min() < 0.0 or array.max() > 1.0):
+                array = np.clip(array, -1.0, 1.0) * 0.5 + 0.5
+            array = (np.clip(array, 0.0, 1.0) * 255.0).round().astype(np.uint8)
+        return array[..., :3].astype(np.uint8)
+    raise TypeError(f"Video decode expected an RGB frame, got {type(value)!r}.")
+
+
+def decode_path_video_frames(
+    path: str | Path,
+    *,
+    max_frames: int | None = None,
+    keep: Literal["first", "last"] = "first",
+) -> list[np.ndarray]:
+    """Decode a video file to RGB uint8 frames (H, W, C).
+
+    ``keep='first'`` stops after ``max_frames``. ``keep='last'`` still scans the
+    file and retains only the tail window.
+    """
+    media_path = Path(path)
+    if not media_path.exists():
+        raise FileNotFoundError(f"Video path does not exist: {media_path}")
+    if keep not in {"first", "last"}:
+        raise ValueError("Video keep must be either 'first' or 'last'.")
+    if max_frames is not None and int(max_frames) <= 0:
+        raise ValueError("Video max_frames must be positive.")
+    try:
+        import imageio.v3 as iio
+    except ImportError as exc:
+        raise ImportError(
+            "Video path decoding requires imageio. Install imageio[ffmpeg] or provide decoded frames."
+        ) from exc
+
+    limit = None if max_frames is None else int(max_frames)
+    if keep == "last" and limit is not None:
+        window: deque[np.ndarray] = deque(maxlen=limit)
+        for frame in iio.imiter(media_path):
+            window.append(_frame_to_uint8_rgb(frame))
+        frames = list(window)
+    else:
+        frames = []
+        for frame in iio.imiter(media_path):
+            frames.append(_frame_to_uint8_rgb(frame))
+            if limit is not None and len(frames) >= limit:
+                break
+    if not frames:
+        raise ValueError(f"Video path produced no frames: {media_path}")
+    return frames