Commit 9234ad8 for stable-diffusion.cpp

commit 9234ad822a376a4724638467736118ed61d68ee9
Author: leejet <leejet714@gmail.com>
Date:   Sun Nov 8 00:09:48 2026 +0800

    feat: add RelayVSR video upscaling with CUDA window attention (#2285)

diff --git a/README.md b/README.md
index 28af00a..2442865 100644
--- a/README.md
+++ b/README.md
@@ -96,6 +96,7 @@ API and command-line option may change frequently.***
   - Latent Consistency Models support (LCM/LCM-LoRA)
   - Faster and memory efficient latent decoding with [TAESD](./docs/taesd.md)
   - Upscale images generated with [ESRGAN](./docs/esrgan.md)
+  - Upscale videos with [RelayVSR](./docs/relay_vsr.md) (experimental, 2x and 4x)
 - Supported backends
   - CPU (AVX, AVX2 and AVX512 support for x86 architectures)
   - CUDA
diff --git a/docs/relay_vsr.md b/docs/relay_vsr.md
new file mode 100644
index 0000000..1352f41
--- /dev/null
+++ b/docs/relay_vsr.md
@@ -0,0 +1,70 @@
+# RelayVSR video super-resolution
+
+RelayVSR uses a Wan model to sample sparse reference latents, followed by the
+Flash conditional decoder to reconstruct every input frame. The model code
+follows [RelayVSR](https://github.com/kopperx/RelayVSR); the loader maps
+[ComfyUI repackaged weights](https://huggingface.co/Comfy-Org/RelayVSR) to the
+original module names.
+
+Use `-M vid_upscale` with an ordered directory of RGB images. Filenames are
+sorted lexicographically. Supply the source frame rate with `--fps`. Output
+keeps the input frame count. Use a video output supported by the CLI, such as
+`.avi` or `.webm`, or a numbered PNG output such as `output/%04d.png`.
+
+The scale is an explicit, required argument. It is not read from checkpoint
+metadata. Use matching Wan and Flash checkpoints:
+
+| Scale | `--diffusion-model` | `--vae` |
+| --- | --- | --- |
+| 2 | `relayvsr_x2_lightx2v_int8_convrot.safetensors` | `relayvsr_flash_vae_x2_fp32.safetensors` |
+| 4 | `relayvsr_x4_int8_convrot.safetensors` | `relayvsr_flash_vae_x4_fp32.safetensors` |
+
+```sh
+sd-cli -M vid_upscale \
+  --diffusion-model models/diffusion_models/relayvsr_x2_lightx2v_int8_convrot.safetensors \
+  --vae models/vae/relayvsr_flash_vae_x2_fp32.safetensors \
+  --input-frames input_frames --upscale-factor 2 --fps 24 \
+  --vsr-window-size 16 -s 42 -o output.avi
+```
+
+`--vsr-window-size` includes both reference endpoints. The default 16 samples
+references at frame indices 0, 15, 30, and so on, always including the last
+frame. Shared endpoints update Flash history in the following window but are
+emitted only once. Single-frame input is also supported.
+
+Wan performs one flow-matching Euler step at timestep 1000 with guidance 1,
+using the prompt embedding stored in the checkpoint. No text encoder or
+ordinary Wan VAE is needed. Generic generation sampling settings do not
+configure this fixed sampling path.
+
+The Flash scale cannot be verified from its tensor shapes: the x2 and x4 files
+have identical shapes. The caller must select the correct pair. Wan's input
+projection is checked against the requested scale. Inputs are replicate-padded
+internally and outputs are cropped to exactly the input size times the scale.
+
+INT8 convrot uses the existing [quantized-weight execution path](int8_convrot.md).
+Backend and parameter placement use `--backend` and `--params-backend`, with
+Wan assigned to `diffusion` and Flash to `vae`. CUDA builds with CUTLASS use
+fused window attention on compute capability 8.0 or newer. It loads spatial
+neighborhoods directly, with FP16 Q/K/V and FP32 accumulation, and preserves
+Wan's boundary-shifted windows and Flash's boundary-truncated windows.
+Other backends use bounded spatial tiles with ordinary attention operators.
+Set `GGML_CUDA_DISABLE_WINDOW_ATTENTION=1` to use that fallback on CUDA for
+comparison. Floating-point results can differ between these implementations.
+
+Library callers initialize `sd_video_upscaler_ctx_params_t` with
+`sd_video_upscaler_ctx_params_init()`, set the model paths, explicit scale and
+backend options, and create a `video_upscaler_ctx_t` with
+`new_video_upscaler_ctx()`. Model architecture is detected from
+weight names and shapes; the scale remains caller-supplied.
+
+Initialize `sd_video_upscale_params_t` with `sd_video_upscale_params_init()`,
+then set the RGB frames, frame count, FPS, seed and RelayVSR reference window.
+Call `upscale_video()` and free the result with
+`free_sd_video_generation_result()`. Defaults are 24 FPS, seed 42 and a
+16-frame reference window. No sampler or scheduler selection is required.
+
+Each call starts fresh
+temporal state. Model caches are bounded by the temporal windows; the public
+API currently holds the complete input and output frame arrays in host memory.
+Audio is not copied by this path.
diff --git a/examples/cli/main.cpp b/examples/cli/main.cpp
index 591a151..bcf7359 100644
--- a/examples/cli/main.cpp
+++ b/examples/cli/main.cpp
@@ -3,6 +3,7 @@
 #include <time.h>
 #include <algorithm>
 #include <cctype>
+#include <climits>
 #include <filesystem>
 #include <functional>
 #include <iostream>
@@ -33,10 +34,13 @@ const char* previews_str[] = {
 std::regex format_specifier_regex("(?:[^%]|^)(?:%%)*(%\\d{0,3}d)");

 struct SDCliParams {
-    SDMode mode             = IMG_GEN;
-    std::string output_path = "output.png";
-    int output_begin_idx    = -1;
-    int compression_quality = 90;
+    std::string input_frames;
+    int video_upscale_factor = 0;
+    int vsr_window_size      = 16;
+    SDMode mode              = IMG_GEN;
+    std::string output_path  = "output.png";
+    int output_begin_idx     = -1;
+    int compression_quality  = 90;
     std::string image_path;
     std::string metadata_format = "text";

@@ -62,6 +66,7 @@ struct SDCliParams {
         ArgOptions options;

         options.string_options = {
+            {"", "--input-frames", "directory of ordered RGB frames for vid_upscale", 0, &input_frames},
             {"-o",
              "--output",
              "path to write result image to. you can use printf-style %d format specifiers for image sequences (default: ./output.png) (eg. output_%03d.png). Single-file video outputs support .avi, .webm, and animated .webp",
@@ -90,6 +95,8 @@ struct SDCliParams {
         };

         options.int_options = {
+            {"", "--upscale-factor", "required video upscale factor (RelayVSR: 2 or 4)", &video_upscale_factor},
+            {"", "--vsr-window-size", "RelayVSR window including both endpoints (default: 16)", &vsr_window_size},
             {"",
              "--preview-interval",
              "preview interval: in each sampling pass, positive N updates every Nth denoiser step and -N previews only completed logical step N; 0 previews the final completed step of the first pass (base-resolution or high-noise). Default: 1",
@@ -190,7 +197,7 @@ struct SDCliParams {
         options.manual_options = {
             {"-M",
              "--mode",
-             "run mode, one of [img_gen, adetailer, vid_gen, upscale, convert, metadata], default: img_gen",
+             "run mode, one of [img_gen, adetailer, vid_gen, vid_upscale, upscale, convert, metadata], default: img_gen",
              on_mode_arg},
             {"",
              "--preview",
@@ -220,6 +227,10 @@ struct SDCliParams {
     }

     bool validate() {
+        if (mode == VID_UPSCALE && (input_frames.empty() || video_upscale_factor <= 0 || vsr_window_size < 2)) {
+            LOG_ERROR("vid_upscale requires --input-frames, positive --upscale-factor, and --vsr-window-size >= 2");
+            return false;
+        }
         if (mode != METADATA) {
             if (output_path.length() == 0) {
                 LOG_ERROR("error: the following arguments are required: output_path");
@@ -529,7 +540,7 @@ bool save_results(const SDCliParams& cli_params,
         return sucessful_reults != 0;
     }

-    if (cli_params.mode == VID_GEN && num_results > 1) {
+    if ((cli_params.mode == VID_GEN && num_results > 1) || cli_params.mode == VID_UPSCALE) {
         if (ext_lower != ".avi" && ext_lower != ".webp" && ext_lower != ".webm")
             ext = ".avi";
         std::string params = gen_params.embed_image_metadata
@@ -664,6 +675,50 @@ int main(int argc, const char* argv[]) {
         return 0;
     }

+    if (cli_params.mode == VID_UPSCALE) {
+        if (ctx_params.diffusion_model_path.empty() || ctx_params.vae_path.empty() || gen_params.fps <= 0) {
+            LOG_ERROR("vid_upscale requires --diffusion-model, --vae and positive --fps");
+            return 1;
+        }
+        std::vector<SDImageOwner> owned_frames;
+        if (!load_images_from_dir(cli_params.input_frames, owned_frames) || owned_frames.empty()) {
+            LOG_ERROR("vid_upscale input contains no readable frames");
+            return 1;
+        }
+        if (owned_frames.size() > size_t(INT_MAX))
+            return 1;
+        std::vector<sd_image_t> frames;
+        for (const auto& frame : owned_frames)
+            frames.push_back(frame.get());
+        sd_video_upscaler_ctx_params_t params;
+        sd_video_upscaler_ctx_params_init(&params);
+        params.diffusion_model_path = ctx_params.diffusion_model_path.c_str();
+        params.vae_path             = ctx_params.vae_path.c_str();
+        params.upscale_factor       = cli_params.video_upscale_factor;
+        params.n_threads            = ctx_params.n_threads;
+        params.backend              = ctx_params.effective_backend.c_str();
+        params.params_backend       = ctx_params.effective_params_backend.c_str();
+        std::unique_ptr<video_upscaler_ctx_t, decltype(&free_video_upscaler_ctx)> upscaler(
+            new_video_upscaler_ctx(&params),
+            free_video_upscaler_ctx);
+        if (!upscaler)
+            return 1;
+        sd_video_generation_result_t* output = nullptr;
+        sd_video_upscale_params_t upscale_params;
+        sd_video_upscale_params_init(&upscale_params);
+        upscale_params.frames      = frames.data();
+        upscale_params.frame_count = int(frames.size());
+        upscale_params.fps         = gen_params.fps;
+        upscale_params.window_size = cli_params.vsr_window_size;
+        upscale_params.seed        = gen_params.seed;
+        if (!upscale_video(upscaler.get(), &upscale_params, &output))
+            return 1;
+        std::string video_info = output->generation_info;
+        SDImageVec results;
+        results.adopt_video(output);
+        return save_results(cli_params, ctx_params, gen_params, results, int(results.size()), nullptr, video_info) ? 0 : 1;
+    }
+
     if (!gen_params.ad_model_path.empty() && cli_params.mode != IMG_GEN && cli_params.mode != ADETAILER) {
         LOG_ERROR("--ad-model is only supported in image generation and adetailer modes");
         return 1;
diff --git a/examples/common/common.cpp b/examples/common/common.cpp
index 02c3088..7934924 100644
--- a/examples/common/common.cpp
+++ b/examples/common/common.cpp
@@ -35,6 +35,7 @@ const char* const modes_str[] = {
     "convert",
     "upscale",
     "metadata",
+    "vid_upscale",
 };

 static sd_vae_format_t str_to_vae_format(const std::string& value) {
diff --git a/examples/common/common.h b/examples/common/common.h
index 4ecbef4..d4df4fa 100644
--- a/examples/common/common.h
+++ b/examples/common/common.h
@@ -22,7 +22,7 @@ std::string argv_to_utf8(int index, const char** argv);
 #define BOOL_STR(b) ((b) ? "true" : "false")

 extern const char* const modes_str[];
-#define SD_ALL_MODES_STR "img_gen, adetailer, vid_gen, convert, upscale, metadata"
+#define SD_ALL_MODES_STR "img_gen, adetailer, vid_gen, convert, upscale, metadata, vid_upscale"

 enum SDMode {
     IMG_GEN,
@@ -31,6 +31,7 @@ enum SDMode {
     CONVERT,
     UPSCALE,
     METADATA,
+    VID_UPSCALE,
     MODE_COUNT
 };

diff --git a/include/stable-diffusion.h b/include/stable-diffusion.h
index 1c61e4b..a1d82e7 100644
--- a/include/stable-diffusion.h
+++ b/include/stable-diffusion.h
@@ -615,6 +615,37 @@ SD_API int get_upscale_factor(upscaler_ctx_t* upscaler_ctx);
 // Reads model metadata only; returns 0 if the file is not a recognized RGB ESRGAN model.
 SD_API int get_upscaler_model_scale(const char* model_path);

+typedef struct video_upscaler_ctx_t video_upscaler_ctx_t;
+
+typedef struct {
+    const char* diffusion_model_path;
+    const char* vae_path;
+    // Explicit output scale; RelayVSR requires 2 or 4 matching both checkpoints.
+    int upscale_factor;
+    int n_threads;
+    const char* backend;
+    const char* params_backend;
+} sd_video_upscaler_ctx_params_t;
+
+typedef struct {
+    const sd_image_t* frames;
+    int frame_count;
+    int fps;
+    int64_t seed;
+    // RelayVSR reference window, including both endpoints; defaults to 16.
+    int window_size;
+} sd_video_upscale_params_t;
+
+SD_API void sd_video_upscaler_ctx_params_init(sd_video_upscaler_ctx_params_t* params);
+SD_API void sd_video_upscale_params_init(sd_video_upscale_params_t* params);
+SD_API video_upscaler_ctx_t* new_video_upscaler_ctx(const sd_video_upscaler_ctx_params_t* params);
+SD_API void free_video_upscaler_ctx(video_upscaler_ctx_t* ctx);
+// Frames are RGB, have equal dimensions, and remain owned by the caller.
+// Free the result with free_sd_video_generation_result().
+SD_API bool upscale_video(video_upscaler_ctx_t* ctx,
+                          const sd_video_upscale_params_t* params,
+                          sd_video_generation_result_t** result_out);
+
 typedef struct adetailer_ctx_t adetailer_ctx_t;

 typedef struct {
diff --git a/src/core/cuda/cute_attention.cu b/src/core/cuda/cute_attention.cu
index cdafc99..1eaefa4 100644
--- a/src/core/cuda/cute_attention.cu
+++ b/src/core/cuda/cute_attention.cu
@@ -150,7 +150,7 @@ namespace sd_fattn_cute {
         }
     }

-    template <int Rows>
+    template <int Rows, bool Masked = false>
     struct Softmax {
         decltype(make_tensor<float>(Shape<Int<Rows>>{})) maximum, sum;
         template <bool First, typename Scores, typename Output>
@@ -180,8 +180,9 @@ namespace sd_fattn_cute {
                 }
 #pragma unroll
                 for (int n = 0; n < size<1>(scores); ++n) {
-                    const float value = exp2f(scores(m, n) * 1.4426950408889634f - next_max * 1.4426950408889634f);
-                    scores(m, n)      = value;
+                    const float safe_max = Masked && next_max == -INFINITY ? 0.f : next_max;
+                    const float value    = exp2f(scores(m, n) * 1.4426950408889634f - safe_max * 1.4426950408889634f);
+                    scores(m, n)         = value;
                     row_sum += value;
                 }
                 // Defer the four-lane sum reduction until the final output normalization.
@@ -196,7 +197,7 @@ namespace sd_fattn_cute {
                 float total = sum(m);
                 total += __shfl_xor_sync(0xffffffff, total, 2);
                 total += __shfl_xor_sync(0xffffffff, total, 1);
-                const float inverse = 1.f / total;
+                const float inverse = Masked && total == 0.f ? 0.f : 1.f / total;
 #pragma unroll
                 for (int n = 0; n < size<1>(output); ++n)
                     output(m, n) *= inverse;
@@ -790,3 +791,5 @@ void sd_ggml_register_cuda_attention(ggml_backend_dev_t device) {
     desc.priority  = 400;
     GGML_ASSERT(ggml_ext_register_kernel_ex(device, &desc, GGML_EXT_KERNEL_CAPTURE_SAFE | GGML_EXT_KERNEL_REPLAY_REUSABLE));
 }
+
+#include "window_attention.cuh"
diff --git a/src/core/cuda/registration.cu b/src/core/cuda/registration.cu
index 1f48174..d92be44 100644
--- a/src/core/cuda/registration.cu
+++ b/src/core/cuda/registration.cu
@@ -4,6 +4,7 @@
 void sd_ggml_register_cuda_i8_gated_residual(ggml_backend_dev_t device);
 void sd_ggml_register_cuda_i8_projection(ggml_backend_dev_t device);
 void sd_ggml_register_cuda_attention(ggml_backend_dev_t device);
+void sd_ggml_register_cuda_window_attention(ggml_backend_dev_t device);
 #endif

 namespace SD_CUDA_NAMESPACE {
@@ -39,6 +40,7 @@ namespace SD_CUDA_NAMESPACE {
         sd_ggml_register_cuda_i8_projection(device);
         sd_ggml_register_cuda_i8_gated_residual(device);
         sd_ggml_register_cuda_attention(device);
+        sd_ggml_register_cuda_window_attention(device);
 #endif
     }
 }
diff --git a/src/core/cuda/window_attention.cuh b/src/core/cuda/window_attention.cuh
new file mode 100644
index 0000000..600cd91
--- /dev/null
+++ b/src/core/cuda/window_attention.cuh
@@ -0,0 +1,284 @@
+/*
+ * Adapted from FlashAttention v2.8.3:
+ * https://github.com/Dao-AILab/flash-attention/tree/v2.8.3/csrc/flash_attn/src
+ * Sources: kernel_traits.h, utils.h, softmax.h, flash_fwd_kernel.h.
+ * Copyright (c) 2023-2024, Tri Dao.
+ *
+ * BSD 3-Clause License
+ *
+ * Copyright (c) 2022, the respective contributors, as shown by the AUTHORS file.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * * Redistributions of source code must retain the above copyright notice, this
+ *   list of conditions and the following disclaimer.
+ *
+ * * Redistributions in binary form must reproduce the above copyright notice,
+ *   this list of conditions and the following disclaimer in the documentation
+ *   and/or other materials provided with the distribution.
+ *
+ * * Neither the name of the copyright holder nor the names of its
+ *   contributors may be used to endorse or promote products derived from
+ *   this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+#ifndef __SD_CORE_CUDA_WINDOW_ATTENTION_CUH__
+#define __SD_CORE_CUDA_WINDOW_ATTENTION_CUH__
+
+namespace sd_fattn_cute {
+    struct WindowRegion {
+        int left, top, width, height;
+    };
+
+    static __device__ WindowRegion window_region(const SDWindowAttentionParams& p, int plane, int x, int y) {
+        int w = p.window_width[plane], h = p.window_height[plane];
+        if (p.preserve_boundary) {
+            w = min(w, p.width);
+            h = min(h, p.height);
+            return {min(max(x - w / 2, 0), p.width - w), min(max(y - h / 2, 0), p.height - h), w, h};
+        }
+        int left = max(x - w / 2, 0), top = max(y - h / 2, 0);
+        return {left, top, min(p.width, x + w / 2) - left, min(p.height, y + h / 2) - top};
+    }
+
+    template <typename Dst, typename Id, typename Index>
+    __device__ __forceinline__ void window_copy(const cutlass::half_t* source, Dst& dst, const Id& id, int dim, Index index) {
+#pragma unroll
+        for (int m = 0; m < size<1>(dst); ++m) {
+            const int row = index(get<0>(id(0, m, 0)));
+#pragma unroll
+            for (int k = 0; k < size<2>(dst); ++k) {
+                if (row >= 0) {
+                    const auto* src        = source + int64_t(row) * dim + get<1>(id(0, m, k));
+                    const unsigned address = unsigned(__cvta_generic_to_shared(&dst(0, m, k)));
+                    asm volatile("cp.async.cg.shared.global [%0], [%1], 16;"
+                                 :
+                                 : "r"(address), "l"(src));
+                } else {
+                    cute::clear(dst(_, m, k));
+                }
+            }
+        }
+    }
+
+    template <int D>
+    __global__ __launch_bounds__(128) void window_kernel(const cutlass::half_t* q, const cutlass::half_t* k, const cutlass::half_t* v, float* output, SDWindowAttentionParams p, int kv_heads) {
+#if defined(__CUDA_ARCH__) && __CUDA_ARCH__ >= 800
+        constexpr int BM = 64, BN = 64, TW = 8;
+        using T       = Traits<BM, BN, D>;
+        using Element = typename T::Element;
+        extern __shared__ char storage[];
+        const int tid = threadIdx.x, head = blockIdx.z;
+        const int qx = blockIdx.x * TW, qy = blockIdx.y * (BM / TW);
+        const int tokens = p.width * p.height;
+        q += int64_t(head) * tokens * D;
+        const int64_t kv_offset = int64_t(head / (p.heads / kv_heads)) * tokens * p.planes * D;
+        k += kv_offset;
+        v += kv_offset;
+        auto sQ      = make_tensor(make_smem_ptr(reinterpret_cast<Element*>(storage)), typename T::QLayout{});
+        auto sK      = make_tensor(sQ.data() + size(sQ), typename T::KVLayout{});
+        auto sV      = make_tensor(sK.data() + size(sK), typename T::KVLayout{});
+        auto sVt     = make_tensor(sV.data(), typename T::VtLayout{});
+        auto sVplain = make_tensor(sV.data().get(), get_nonswizzle_portion(typename T::VtLayout{}));
+        typename T::GlobalCopy global_copy;
+        auto thread_copy = global_copy.get_thread_slice(tid);
+        auto tQsQ        = thread_copy.partition_D(sQ);
+        auto tKsK        = thread_copy.partition_D(sK);
+        auto tVsV        = thread_copy.partition_D(sV);
+        auto q_id        = thread_copy.partition_S(make_identity_tensor(Shape<Int<BM>, Int<D>>{}));
+        auto kv_id       = thread_copy.partition_S(make_identity_tensor(Shape<Int<BN>, Int<D>>{}));
+        auto query_index = [&](int row) {
+            const int x = qx + row % TW, y = qy + row / TW;
+            return x < p.width && y < p.height ? y * p.width + x : -1;
+        };
+        window_copy(q, tQsQ, q_id, D, query_index);
+        cute::cp_async_fence();
+
+        typename T::Mma mma;
+        auto thread_mma = mma.get_thread_slice(tid);
+        auto rQ         = thread_mma.partition_fragment_A(sQ);
+        auto rK         = thread_mma.partition_fragment_B(sK);
+        auto rV         = thread_mma.partition_fragment_B(sVplain);
+        auto acc_o      = partition_fragment_C(mma, Shape<Int<BM>, Int<D>>{});
+        auto copyQ      = make_tiled_copy_A(typename T::CopyAtom{}, mma);
+        auto copyK      = make_tiled_copy_B(typename T::CopyAtom{}, mma);
+        auto copyV      = make_tiled_copy_B(typename T::CopyAtomT{}, mma);
+        auto threadQ    = copyQ.get_thread_slice(tid);
+        auto threadK    = copyK.get_thread_slice(tid);
+        auto threadV    = copyV.get_thread_slice(tid);
+        auto tSsQ       = threadQ.partition_S(sQ);
+        auto tSsK       = threadK.partition_S(sK);
+        auto tOsV       = threadV.partition_S(sVt);
+        auto score_id   = thread_mma.partition_C(make_identity_tensor(Shape<Int<BM>, Int<BN>>{}));
+        clear(acc_o);
+        Softmax<2 * size<1>(acc_o), true> softmax;
+        const float scale = rsqrtf(float(D));
+        for (int plane = 0; plane < p.planes; ++plane) {
+            const auto first = window_region(p, plane, qx, qy);
+            const auto last  = window_region(p, plane, min(qx + TW - 1, p.width - 1), min(qy + BM / TW - 1, p.height - 1));
+            const int kw     = last.left + last.width - first.left;
+            const int kh     = last.top + last.height - first.top;
+            for (int start = 0; start < kw * kh; start += BN) {
+                auto key_index = [&](int row) {
+                    row += start;
+                    return row < kw * kh ? plane * tokens + (first.top + row / kw) * p.width + first.left + row % kw : -1;
+                };
+                window_copy(k, tKsK, kv_id, D, key_index);
+                window_copy(v, tVsV, kv_id, D, key_index);
+                cute::cp_async_fence();
+                cute::cp_async_wait<0>();
+                __syncthreads();
+                auto acc_s = partition_fragment_C(mma, Shape<Int<BM>, Int<BN>>{});
+                clear(acc_s);
+                gemm(acc_s, rQ, rK, tSsQ, tSsK, mma, copyQ, copyK, threadQ, threadK);
+#pragma unroll
+                for (int i = 0; i < size(acc_s); ++i) {
+                    const int qr = get<0>(score_id(i)), kr = start + get<1>(score_id(i));
+                    const int x = qx + qr % TW, y = qy + qr / TW;
+                    const auto region = window_region(p, plane, x, y);
+                    const int kx = first.left + kr % kw, ky = first.top + kr / kw;
+                    const bool valid = x < p.width && y < p.height && kr < kw * kh &&
+                                       kx >= region.left && kx < region.left + region.width &&
+                                       ky >= region.top && ky < region.top + region.height;
+                    acc_s(i)         = valid ? acc_s(i) * scale : -INFINITY;
+                }
+                if (plane == 0 && start == 0)
+                    softmax.template update<true>(acc_s, acc_o);
+                else
+                    softmax.template update<false>(acc_s, acc_o);
+                auto rP   = to_half(acc_s);
+                auto tOrP = make_tensor(rP.data(), convert_layout_acc_Aregs<typename T::Mma>(rP.layout()));
+                gemm_rs(acc_o, tOrP, rV, tOsV, mma, copyV, threadV);
+                __syncthreads();
+            }
+        }
+        softmax.normalize(acc_o);
+        auto output_id = thread_mma.partition_C(make_identity_tensor(Shape<Int<BM>, Int<D>>{}));
+#pragma unroll
+        for (int i = 0; i < size(acc_o); ++i) {
+            const int token = query_index(get<0>(output_id(i)));
+            if (token >= 0)
+                output[(int64_t(token) * p.heads + head) * D + get<1>(output_id(i))] = acc_o(i);
+        }
+#else
+        // This translation unit also targets older GPUs; runtime dispatch excludes this kernel there.
+        asm volatile("trap;");
+#endif
+    }
+}
+
+static bool window_attention_supports(ggml_backend_dev_t device, const ggml_tensor* node, void*) {
+    static const bool disabled = [] {
+        const char* value = std::getenv("GGML_CUDA_DISABLE_WINDOW_ATTENTION");
+        return value && std::atoi(value) != 0;
+    }();
+    SDWindowAttentionParams params;
+    const auto* info = cuda_device(device);
+    return !disabled && info && info->properties.major >= 8 && sd_ggml_window_attn_describe(node, &params);
+}
+
+static ggml_status window_attention_prepare(ggml_backend_t, ggml_tensor* const* nodes, int, void**, size_t* workspace, void*) {
+    *workspace = 0;
+    for (int i = 0; i < 3; ++i)
+        *workspace += (size_t(ggml_nelements(nodes[0]->src[i])) * sizeof(half) + 255) / 256 * 256;
+    return GGML_STATUS_SUCCESS;
+}
+
+static void window_attention_destroy(void*, void*) {}
+
+template <int D>
+static cudaError_t window_attention_launch(const ggml_ext_cuda_context& context, const half* const* inputs, float* output, SDWindowAttentionParams params, int kv_heads) {
+    auto kernel                = sd_fattn_cute::window_kernel<D>;
+    constexpr int shared_bytes = sd_fattn_cute::Traits<64, 64, D>::SharedBytes;
+    static std::mutex mutex;
+    static std::unordered_map<int, bool> initialized;
+    {
+        std::lock_guard<std::mutex> lock(mutex);
+        if (!initialized[context.device]) {
+            auto error = cudaFuncSetAttribute(kernel, cudaFuncAttributeMaxDynamicSharedMemorySize, shared_bytes);
+            if (error != cudaSuccess)
+                return error;
+            initialized[context.device] = true;
+        }
+    }
+    kernel<<<dim3((params.width + 7) / 8, (params.height + 7) / 8, params.heads), 128, shared_bytes, static_cast<cudaStream_t>(context.stream)>>>(
+        reinterpret_cast<const cutlass::half_t*>(inputs[0]), reinterpret_cast<const cutlass::half_t*>(inputs[1]),
+        reinterpret_cast<const cutlass::half_t*>(inputs[2]), output, params, kv_heads);
+    return cudaGetLastError();
+}
+
+static ggml_status window_attention_execute(const ggml_ext_execution_context* execution, ggml_tensor* const* nodes, int, void*, void*) {
+    auto device = ggml_backend_get_device(execution->backend);
+    auto reg    = ggml_backend_dev_backend_reg(device);
+    auto query  = reinterpret_cast<ggml_ext_cuda_context_fn>(ggml_backend_reg_get_proc_address(reg, "ggml_ext_cuda_context_v1"));
+    ggml_ext_cuda_context context;
+    if (!query || !query(execution->backend, &context))
+        return GGML_STATUS_FAILED;
+    SDWindowAttentionParams params;
+    auto* node = nodes[0];
+    if (!sd_ggml_window_attn_describe(node, &params))
+        return GGML_STATUS_FAILED;
+    auto stream   = static_cast<cudaStream_t>(context.stream);
+    auto* base    = static_cast<char*>(ggml_backend_buffer_get_base(execution->workspace));
+    const int dim = int(node->ne[0] / params.heads);
+    const half* inputs[3];
+    for (int i = 0; i < 3; ++i) {
+        const auto* src     = node->src[i];
+        auto* packed        = reinterpret_cast<half*>(base);
+        const int64_t heads = src->ne[0] / dim;
+        copy_to_half<float><<<(ggml_nelements(src) + 255) / 256, 256, 0, stream>>>(static_cast<const char*>(src->data), packed,
+                                                                                   ggml_nelements(src), dim, src->ne[1], heads, src->nb[1], dim * sizeof(float), ggml_nbytes(src), 1.f);
+        if (cudaGetLastError() != cudaSuccess)
+            return GGML_STATUS_FAILED;
+        inputs[i] = packed;
+        base += (size_t(ggml_nelements(src)) * sizeof(half) + 255) / 256 * 256;
+    }
+    const int kv_heads = int(node->src[1]->ne[0] / dim);
+    auto* output       = static_cast<float*>(node->data);
+    const auto error   = dim == 64 ? window_attention_launch<64>(context, inputs, output, params, kv_heads)
+                                   : window_attention_launch<128>(context, inputs, output, params, kv_heads);
+    return error == cudaSuccess ? GGML_STATUS_SUCCESS : GGML_STATUS_FAILED;
+}
+
+void sd_ggml_register_cuda_window_attention(ggml_backend_dev_t device) {
+    const auto* info = cuda_device(device);
+    if (!info || info->properties.major < 8)
+        return;
+    int previous;
+    if (cudaGetDevice(&previous) != cudaSuccess || cudaSetDevice(info->ordinal) != cudaSuccess)
+        return;
+    cudaFuncAttributes attributes64{}, attributes128{};
+    const auto error64  = cudaFuncGetAttributes(&attributes64, sd_fattn_cute::window_kernel<64>);
+    const auto error128 = cudaFuncGetAttributes(&attributes128, sd_fattn_cute::window_kernel<128>);
+    const auto restored = cudaSetDevice(previous);
+    // JIT can produce an SM80+ binary from older PTX containing only the trap.
+    if (restored != cudaSuccess || error64 != cudaSuccess || error128 != cudaSuccess ||
+        std::min(attributes64.binaryVersion, attributes64.ptxVersion) < 80 ||
+        std::min(attributes128.binaryVersion, attributes128.ptxVersion) < 80)
+        return;
+    ggml_ext_kernel_desc desc = {};
+    desc.abi_version          = GGML_EXT_ABI_VERSION;
+    desc.name                 = "sd.window_attention.cuda.v1";
+    desc.op                   = GGML_OP_CUSTOM;
+    desc.custom_op            = sd_ggml_window_attn_op();
+    desc.priority             = 100;
+    desc.supports             = window_attention_supports;
+    desc.prepare              = window_attention_prepare;
+    desc.destroy              = window_attention_destroy;
+    desc.execute              = window_attention_execute;
+    GGML_ASSERT(ggml_ext_register_kernel_ex(device, &desc, GGML_EXT_KERNEL_CAPTURE_SAFE | GGML_EXT_KERNEL_REPLAY_REUSABLE));
+}
+
+#endif
diff --git a/src/core/ggml_extensions.cpp b/src/core/ggml_extensions.cpp
index 25fa222..dfe5bca 100644
--- a/src/core/ggml_extensions.cpp
+++ b/src/core/ggml_extensions.cpp
@@ -501,6 +501,65 @@ ggml_tensor* ggml_sol_attn(ggml_context* ctx, ggml_tensor* q, ggml_tensor* k, gg
     return ggml_ext_op_create(ctx, sd_ggml_sol_attn_op(), inputs, 3, &params);
 }

+static bool window_attn_infer(ggml_tensor* const* inputs, int count, const void* attributes, ggml_ext_tensor_desc* out) {
+    if (count != 3 || !attributes)
+        return false;
+    SDWindowAttentionParams p;
+    std::memcpy(&p, attributes, sizeof(p));
+    if (p.width <= 0 || p.height <= 0 || int64_t(p.width) * p.height > INT32_MAX / 4 ||
+        p.heads <= 0 || p.planes < 1 || p.planes > 4 || (p.preserve_boundary != 0 && p.preserve_boundary != 1))
+        return false;
+    for (int i = 0; i < p.planes; ++i)
+        if (p.window_height[i] <= 0 || p.window_width[i] <= 0 ||
+            (!p.preserve_boundary && (p.window_height[i] % 2 || p.window_width[i] % 2)))
+            return false;
+    for (int i = 0; i < 3; ++i) {
+        const auto* t = inputs[i];
+        if (!t || t->type != GGML_TYPE_F32 || !ggml_is_contiguous(t) || t->ne[2] != 1 || t->ne[3] != 1 ||
+            t->ne[1] != int64_t(p.width) * p.height * (i ? p.planes : 1))
+            return false;
+    }
+    const auto* q = inputs[0];
+    const auto* k = inputs[1];
+    if (q->ne[0] % p.heads || (q->ne[0] / p.heads != 64 && q->ne[0] / p.heads != 128) ||
+        k->ne[0] <= 0 || k->ne[0] > q->ne[0] || q->ne[0] % k->ne[0] ||
+        k->ne[0] % (q->ne[0] / p.heads) || !ggml_are_same_shape(k, inputs[2]))
+        return false;
+    *out = {GGML_TYPE_F32, {q->ne[0], q->ne[1], 1, 1}};
+    return true;
+}
+
+ggml_ext_op_t sd_ggml_window_attn_op() {
+    static const auto op = [] {
+        const ggml_ext_op_desc desc = {GGML_EXT_ABI_VERSION, "sd.window_attn.v1", sizeof(SDWindowAttentionParams), window_attn_infer};
+        auto result                 = ggml_ext_register_op(&desc);
+        GGML_ASSERT(result);
+        return result;
+    }();
+    return op;
+}
+
+bool sd_ggml_window_attn_describe(const ggml_tensor* node, SDWindowAttentionParams* params) {
+    if (!node || ggml_ext_op_get(node) != sd_ggml_window_attn_op() || node->src[3] || !ggml_is_contiguous(node))
+        return false;
+    const auto* attributes = ggml_ext_op_attributes(node);
+    ggml_ext_tensor_desc out;
+    if (!window_attn_infer(node->src, 3, attributes, &out) || node->type != out.type || std::memcmp(node->ne, out.ne, sizeof(out.ne)))
+        return false;
+    std::memcpy(params, attributes, sizeof(*params));
+    return true;
+}
+
+ggml_tensor* sd_ggml_window_attn(ggml_context* ctx, ggml_backend_t backend, ggml_tensor* q, ggml_tensor* k, ggml_tensor* v, const SDWindowAttentionParams& params) {
+    ggml_tensor* inputs[] = {q, k, v};
+    ggml_ext_tensor_desc out;
+    if (!backend || !window_attn_infer(inputs, 3, &params, &out))
+        return nullptr;
+    sd_ggml_register_extensions(backend);
+    auto result = ggml_ext_op_create(ctx, sd_ggml_window_attn_op(), inputs, 3, &params);
+    return ggml_backend_supports_op(backend, result) ? result : nullptr;
+}
+
 void sd_ggml_register_extensions(ggml_backend_t backend) {
     if (!backend) {
         return;
diff --git a/src/core/ggml_extensions.h b/src/core/ggml_extensions.h
index bc9ee9a..87a51a7 100644
--- a/src/core/ggml_extensions.h
+++ b/src/core/ggml_extensions.h
@@ -80,6 +80,18 @@ struct SDSolAttentionParams {
     float tau;
 };

+struct SDWindowAttentionParams {
+    int32_t width, height, heads, planes;
+    int16_t window_height[4], window_width[4];
+    int32_t preserve_boundary;
+};
+
+ggml_ext_op_t sd_ggml_window_attn_op();
+bool sd_ggml_window_attn_describe(const ggml_tensor* node, SDWindowAttentionParams* params);
+// Contiguous F32 Q [D*heads, W*H], K/V [D*kv_heads, W*H*planes].
+// Returns Q's layout, or nullptr when the backend has no compatible kernel.
+ggml_tensor* sd_ggml_window_attn(ggml_context* ctx, ggml_backend_t backend, ggml_tensor* q, ggml_tensor* k, ggml_tensor* v, const SDWindowAttentionParams& params);
+
 ggml_ext_op_t sd_ggml_sol_attn_op();
 bool sd_ggml_sol_attn_describe(const ggml_tensor* node, SDSolAttentionParams* params);
 // Noncausal Sol-Attn: contiguous F32 Q/K/V [128, tokens, heads, batch], output [128, heads, tokens, batch].
diff --git a/src/core/tensor.hpp b/src/core/tensor.hpp
index a925dbf..715068c 100644
--- a/src/core/tensor.hpp
+++ b/src/core/tensor.hpp
@@ -222,14 +222,28 @@ namespace sd {
                 return result;
             }

-            for (int64_t flat = 0; flat < result.numel(); ++flat) {
-                std::vector<int64_t> out_coord = tensor_unravel_index(flat, out_shape);
-                std::vector<int64_t> src_coord(static_cast<size_t>(dim()), 0);
-                for (size_t i = 0; i < dims.size(); ++i) {
-                    src_coord[dims[i]] = out_coord[i];
+            std::vector<int64_t> source_strides(dims.size(), 1), strides(dims.size());
+            for (size_t i = 1; i < dims.size(); ++i)
+                source_strides[i] = source_strides[i - 1] * shape_[i - 1];
+            for (size_t i = 0; i < dims.size(); ++i)
+                strides[i] = source_strides[dims[i]];
+            parallel_for(0, result.numel(), 65536, [&](int64_t begin, int64_t end) {
+                auto coord     = tensor_unravel_index(begin, out_shape);
+                int64_t source = 0;
+                for (size_t i = 0; i < dims.size(); ++i)
+                    source += coord[i] * strides[i];
+                for (int64_t flat = begin; flat < end; ++flat) {
+                    result.data()[flat] = data_[source];
+                    for (size_t i = 0; i < dims.size(); ++i) {
+                        ++coord[i];
+                        source += strides[i];
+                        if (coord[i] < out_shape[i])
+                            break;
+                        source -= coord[i] * strides[i];
+                        coord[i] = 0;
+                    }
                 }
-                result[flat] = index(src_coord);
-            }
+            });

             return result;
         }
@@ -1037,11 +1051,13 @@ namespace sd {
             auto x_contributors = make_interpolate_contributors(input_width, output_width, mode, antialias);
             auto y_contributors = make_interpolate_contributors(input_height, output_height, mode, antialias);

-            for (int64_t plane = 0; plane < plane_count; ++plane) {
-                const int64_t input_plane_offset  = plane * input_plane;
-                const int64_t output_plane_offset = plane * output_plane;
-                for (int64_t y = 0; y < output_height; ++y) {
-                    const auto& y_axis = y_contributors[static_cast<size_t>(y)];
+            parallel_for(0, plane_count * output_height, std::max<int64_t>(1, 16384 / output_width), [&](int64_t begin, int64_t end) {
+                for (int64_t row = begin; row < end; ++row) {
+                    const int64_t plane               = row / output_height;
+                    const int64_t y                   = row % output_height;
+                    const int64_t input_plane_offset  = plane * input_plane;
+                    const int64_t output_plane_offset = plane * output_plane;
+                    const auto& y_axis                = y_contributors[static_cast<size_t>(y)];
                     for (int64_t x = 0; x < output_width; ++x) {
                         const auto& x_axis = x_contributors[static_cast<size_t>(x)];
                         double value       = 0.0;
@@ -1055,7 +1071,7 @@ namespace sd {
                         output.data()[output_plane_offset + y * output_width + x] = static_cast<T>(value);
                     }
                 }
-            }
+            });

             return output;
         }
diff --git a/src/core/util.cpp b/src/core/util.cpp
index a691b42..9de1ace 100644
--- a/src/core/util.cpp
+++ b/src/core/util.cpp
@@ -807,13 +807,11 @@ sd::Tensor<float> sd_image_to_tensor(sd_image_t image,
                                                  static_cast<int64_t>(image.height),
                                                  static_cast<int64_t>(image.channel),
                                                  1});
-    for (uint32_t iw = 0; iw < image.width; ++iw) {
-        for (uint32_t ih = 0; ih < image.height; ++ih) {
-            for (uint32_t ic = 0; ic < image.channel; ++ic) {
-                tensor.index(iw, ih, ic, 0) = sd_image_get_f32(image, iw, ih, ic, scale);
-            }
-        }
-    }
+    const int64_t pixels     = int64_t(image.width) * image.height;
+    sd::tensor_for_each(tensor.numel(), [&](int64_t i) {
+        float value      = image.data[(i % pixels) * image.channel + i / pixels];
+        tensor.data()[i] = scale ? value / 255.f : value;
+    });
     if (target_width >= 0 && target_height >= 0 &&
         (tensor.shape()[0] != target_width || tensor.shape()[1] != target_height)) {
         tensor = sd::ops::interpolate(tensor,
diff --git a/src/model/common/vsr.hpp b/src/model/common/vsr.hpp
new file mode 100644
index 0000000..c203dff
--- /dev/null
+++ b/src/model/common/vsr.hpp
@@ -0,0 +1,221 @@
+#ifndef __SD_MODEL_COMMON_VSR_HPP__
+#define __SD_MODEL_COMMON_VSR_HPP__
+
+#include <array>
+#include <limits>
+#include <map>
+#include <stdexcept>
+#include <unordered_map>
+#include "model/common/ggml_block.hpp"
+#include "model/common/rope.hpp"
+
+namespace VSR {
+
+    struct GraphInputs {
+        std::map<std::vector<int>, sd::Tensor<float>> rotations;
+        mutable std::unordered_map<const void*, ggml_tensor*> bindings;
+
+        void begin_graph() {
+            bindings.clear();
+        }
+
+        void clear() {
+            bindings.clear();
+            rotations.clear();
+        }
+
+        template <typename T>
+        ggml_tensor* input(GGMLRunnerContext* ctx, const sd::Tensor<T>& value) const {
+            auto existing = bindings.find(value.data());
+            if (existing != bindings.end())
+                return existing->second;
+            auto result = sd::make_ggml_tensor(ctx->ggml_ctx, value, false);
+            ctx->set_backend_tensor_data(result, value.data());
+            bindings.emplace(value.data(), result);
+            return result;
+        }
+
+        ggml_tensor* rope(GGMLRunnerContext* ctx, int width, int height, const std::vector<int>& times, const std::vector<int>& axes) {
+            std::vector<int> key = {width, height, axes[0], axes[1], axes[2]};
+            key.insert(key.end(), times.begin(), times.end());
+            auto existing = rotations.find(key);
+            if (existing != rotations.end())
+                return input(ctx, existing->second);
+            const int dim = axes[0] + axes[1] + axes[2];
+            auto& pe      = rotations.emplace(std::move(key), sd::Tensor<float>({2, 2, dim / 2, int64_t(width) * height * int64_t(times.size())})).first->second;
+            float* out    = pe.data();
+            for (int t : times) {
+                for (int y = 0; y < height; ++y) {
+                    for (int x = 0; x < width; ++x) {
+                        const int pos[] = {t, y, x};
+                        for (int a = 0; a < 3; ++a) {
+                            for (int i = 0; i < axes[a]; i += 2) {
+                                const double angle = pos[a] * std::pow(10000.0, -double(i) / axes[a]);
+                                *out++             = float(std::cos(angle));
+                                *out++             = float(-std::sin(angle));
+                                *out++             = float(std::sin(angle));
+                                *out++             = float(std::cos(angle));
+                            }
+                        }
+                    }
+                }
+            }
+            return input(ctx, pe);
+        }
+    };
+
+    static ggml_tensor* tokens(ggml_context* ctx, ggml_tensor* x) {
+        x = ggml_reshape_2d(ctx, x, x->ne[0] * x->ne[1], x->ne[2] * x->ne[3]);
+        return ggml_cont(ctx, ggml_transpose(ctx, x));
+    }
+
+    static ggml_tensor* image(ggml_context* ctx, ggml_tensor* x, int width, int height) {
+        const auto channels = x->ne[0];
+        x                   = ggml_cont(ctx, ggml_transpose(ctx, x));
+        return ggml_reshape_4d(ctx, x, width, height, channels, 1);
+    }
+
+    static ggml_tensor* pixel_shuffle(ggml_context* ctx, ggml_tensor* x, int width, int height, int scale, bool channel_first = true) {
+        const int64_t channels = x->ne[0] / (scale * scale);
+        if (!channel_first) {
+            x = ggml_reshape_4d(ctx, x, channels, scale, scale, width * height);
+            x = ggml_cont(ctx, ggml_permute(ctx, x, 2, 0, 1, 3));
+        }
+        x = ggml_reshape_4d(ctx, x, scale, scale, channels, width * height);
+        x = ggml_cont(ctx, ggml_permute(ctx, x, 0, 2, 3, 1));
+        x = ggml_reshape_4d(ctx, x, scale * width, height, scale, channels);
+        x = ggml_cont(ctx, ggml_permute(ctx, x, 0, 2, 1, 3));
+        return ggml_reshape_4d(ctx, x, scale * width, scale * height, channels, 1);
+    }
+
+    struct AttentionTile {
+        int width;
+        int height;
+        sd::Tensor<int32_t> queries;
+        sd::Tensor<int32_t> keys;
+        sd::Tensor<float> mask;
+    };
+
+    struct LocalAttention {
+        int width;
+        int height;
+        std::vector<std::pair<int, int>> windows;
+        bool preserve_boundary;
+        mutable std::vector<AttentionTile> tiles;
+        GraphInputs inputs;
+
+        void begin_graph() {
+            inputs.begin_graph();
+        }
+
+        LocalAttention(int width, int height, const std::vector<std::pair<int, int>>& windows, bool preserve_boundary)
+            : width(width), height(height), windows(windows), preserve_boundary(preserve_boundary) {}
+
+        void prepare_tiles() const {
+            if (!tiles.empty())
+                return;
+            constexpr int tile_size = 16;
+            for (int y = 0; y < height; y += tile_size) {
+                for (int x = 0; x < width; x += tile_size) {
+                    AttentionTile tile;
+                    tile.width   = std::min(tile_size, width - x);
+                    tile.height  = std::min(tile_size, height - y);
+                    tile.queries = sd::Tensor<int32_t>({tile.width * tile.height});
+                    std::vector<int32_t> keys;
+                    auto bounds = [&](int qy, int qx, int plane) {
+                        auto [wh, ww] = windows[plane];
+                        if (preserve_boundary) {
+                            wh             = std::min(wh, height);
+                            ww             = std::min(ww, width);
+                            const int top  = std::clamp(qy - wh / 2, 0, height - wh);
+                            const int left = std::clamp(qx - ww / 2, 0, width - ww);
+                            return std::array<int, 4>{top, left, top + wh, left + ww};
+                        }
+                        return std::array<int, 4>{std::max(0, qy - wh / 2), std::max(0, qx - ww / 2),
+                                                  std::min(height, qy + wh / 2), std::min(width, qx + ww / 2)};
+                    };
+                    for (int p = 0; p < int(windows.size()); ++p) {
+                        auto begin = bounds(y, x, p);
+                        auto end   = bounds(y + tile.height - 1, x + tile.width - 1, p);
+                        for (int ky = begin[0]; ky < end[2]; ++ky)
+                            for (int kx = begin[1]; kx < end[3]; ++kx)
+                                keys.push_back(p * height * width + ky * width + kx);
+                    }
+                    tile.keys = sd::Tensor<int32_t>({int64_t(keys.size())});
+                    std::copy(keys.begin(), keys.end(), tile.keys.data());
+                    tile.mask = sd::Tensor<float>({int64_t(keys.size()), tile.width * tile.height});
+                    for (int q = 0; q < tile.width * tile.height; ++q) {
+                        int qy                 = y + q / tile.width;
+                        int qx                 = x + q % tile.width;
+                        tile.queries.data()[q] = qy * width + qx;
+                        for (size_t k = 0; k < keys.size(); ++k) {
+                            int p                                 = keys[k] / (width * height);
+                            int ky                                = (keys[k] % (width * height)) / width;
+                            int kx                                = keys[k] % width;
+                            auto b                                = bounds(qy, qx, p);
+                            tile.mask.data()[q * keys.size() + k] = ky >= b[0] && ky < b[2] && kx >= b[1] && kx < b[3]
+                                                                        ? 0.f
+                                                                        : -std::numeric_limits<float>::infinity();
+                        }
+                    }
+                    tiles.push_back(std::move(tile));
+                }
+            }
+        }
+
+        ggml_tensor* forward(GGMLRunnerContext* ctx, ggml_tensor* q, ggml_tensor* k, ggml_tensor* v, int heads) const {
+            auto c = ctx->ggml_ctx;
+#ifndef SD_USE_UPSTREAM_GGML
+            if (ctx->flash_attn_enabled && windows.size() <= 4) {
+                SDWindowAttentionParams params = {};
+                params.width                   = width;
+                params.height                  = height;
+                params.heads                   = heads;
+                params.planes                  = int(windows.size());
+                params.preserve_boundary       = preserve_boundary;
+                for (size_t i = 0; i < windows.size(); ++i) {
+                    params.window_height[i] = windows[i].first;
+                    params.window_width[i]  = windows[i].second;
+                }
+                if (auto out = sd_ggml_window_attn(c, ctx->backend, q, k, v, params))
+                    return out;
+            }
+#endif
+            prepare_tiles();
+            ggml_tensor* output = nullptr;
+            ggml_tensor* row    = nullptr;
+            int row_width       = 0;
+            for (const auto& tile : tiles) {
+                auto qi   = inputs.input(ctx, tile.queries);
+                auto ki   = inputs.input(ctx, tile.keys);
+                auto tq   = ggml_get_rows(c, q, qi);
+                auto tk   = ggml_get_rows(c, k, ki);
+                auto tv   = ggml_get_rows(c, v, ki);
+                auto mask = inputs.input(ctx, tile.mask);
+                auto out  = ggml_ext_attention_ext(c, ctx->backend, tq, tk, tv, heads, mask, false, ctx->flash_attn_enabled);
+                out       = ggml_reshape_3d(c, out, out->ne[0], tile.width, tile.height);
+                row       = row ? ggml_concat(c, row, out, 1) : out;
+                row_width += tile.width;
+                if (row_width == width) {
+                    output    = output ? ggml_concat(c, output, row, 2) : row;
+                    row       = nullptr;
+                    row_width = 0;
+                }
+            }
+            return ggml_reshape_2d(c, output, output->ne[0], width * height);
+        }
+    };
+
+    static ggml_tensor* apply_rope(GGMLRunnerContext* ctx, ggml_tensor* x, ggml_tensor* pe, int heads) {
+        auto c              = ctx->ggml_ctx;
+        const int64_t dim   = x->ne[0];
+        const int64_t count = x->ne[1];
+        x                   = ggml_reshape_4d(c, x, dim / heads, heads, count, 1);
+        x                   = Rope::apply_rope(ctx, x, pe);
+        x                   = ggml_cont(c, ggml_permute(c, x, 0, 2, 1, 3));
+        return ggml_reshape_2d(c, x, dim, count);
+    }
+
+}  // namespace VSR
+
+#endif  // __SD_MODEL_COMMON_VSR_HPP__
diff --git a/src/model/diffusion/relay_vsr.hpp b/src/model/diffusion/relay_vsr.hpp
new file mode 100644
index 0000000..a390aa3
--- /dev/null
+++ b/src/model/diffusion/relay_vsr.hpp
@@ -0,0 +1,293 @@
+#ifndef __SD_MODEL_DIFFUSION_RELAY_VSR_HPP__
+#define __SD_MODEL_DIFFUSION_RELAY_VSR_HPP__
+
+#include "model/common/vsr.hpp"
+
+namespace RelayVSR {
+
+    struct WanVSRConfig {
+        int dim            = 3072;
+        int ffn_dim        = 14336;
+        int num_heads      = 24;
+        int num_layers     = 30;
+        int in_channels    = 48;
+        int text_dim       = 4096;
+        int text_len       = 512;
+        int hidden_dim1    = 768;
+        int hidden_dim2    = 3072;
+        int upscale_factor = 4;
+
+        static WanVSRConfig detect_from_weights(const String2TensorStorage& weights, const std::string& prefix, int scale) {
+            WanVSRConfig config;
+            config.upscale_factor = scale;
+            auto weight           = [&](const std::string& name) -> const TensorStorage& { return weights.at(prefix + "." + name); };
+            config.dim            = int(weight("condition_embedder.time_embedder.linear_1.weight").ne[1]);
+            config.ffn_dim        = int(weight("blocks.0.ffn.net.0.proj.weight").ne[1]);
+            config.num_heads      = config.dim / 128;
+            config.text_dim       = int(weight("prompt_embeds").ne[0]);
+            config.text_len       = int(weight("prompt_embeds").ne[1]);
+            config.hidden_dim1    = int(weight("lq_proj.conv1.weight").ne[3]);
+            config.hidden_dim2    = int(weight("lq_proj.conv2.weight").ne[3]);
+            config.num_layers     = 0;
+            while (weights.count(prefix + ".blocks." + std::to_string(config.num_layers) + ".attn1.to_q.weight"))
+                ++config.num_layers;
+            if ((scale != 2 && scale != 4) || weight("lq_proj.conv1.weight").ne[2] != 3 * (4 * scale) * (4 * scale) ||
+                config.dim != 3072 || config.num_layers != 30 || config.text_dim != 4096 ||
+                weight("proj_out.weight").ne[1] != 192) {
+                throw std::runtime_error("RelayVSR Wan weights do not match the requested scale or architecture");
+            }
+            LOG_VERBOSE("relayvsr: dim = %d, num_layers = %d, ffn_dim = %d, scale = %d", config.dim, config.num_layers, config.ffn_dim, scale);
+            return config;
+        }
+    };
+
+    class LQ4xProj : public GGMLBlock {
+        int hidden_dim1_;
+        int hidden_dim2_;
+
+    public:
+        explicit LQ4xProj(const WanVSRConfig& config)
+            : hidden_dim1_(config.hidden_dim1), hidden_dim2_(config.hidden_dim2) {
+            const int patch    = 4 * config.upscale_factor;
+            blocks["conv1"]    = std::make_shared<Conv2d>(3 * patch * patch, hidden_dim1_, std::pair<int, int>{1, 1});
+            blocks["norm1"]    = std::make_shared<RMSNorm>(hidden_dim1_, 1e-6f);
+            blocks["conv2"]    = std::make_shared<Conv2d>(hidden_dim1_, hidden_dim2_, std::pair<int, int>{3, 3}, std::pair<int, int>{2, 2}, std::pair<int, int>{1, 1});
+            blocks["norm2"]    = std::make_shared<RMSNorm>(hidden_dim2_, 1e-6f);
+            blocks["out_proj"] = std::make_shared<Linear>(hidden_dim2_, config.dim);
+        }
+
+        ggml_tensor* forward(GGMLRunnerContext* ctx, ggml_tensor* unshuffled) {
+            auto conv1    = std::dynamic_pointer_cast<Conv2d>(blocks["conv1"]);
+            auto conv2    = std::dynamic_pointer_cast<Conv2d>(blocks["conv2"]);
+            auto norm1    = std::dynamic_pointer_cast<RMSNorm>(blocks["norm1"]);
+            auto norm2    = std::dynamic_pointer_cast<RMSNorm>(blocks["norm2"]);
+            auto out_proj = std::dynamic_pointer_cast<Linear>(blocks["out_proj"]);
+            auto c        = ctx->ggml_ctx;
+            auto x        = conv1->forward(ctx, unshuffled);
+            int width = int(x->ne[0]), height = int(x->ne[1]);
+            x = ggml_silu(c, norm1->forward(ctx, VSR::tokens(c, x)));
+            x = conv2->forward(ctx, VSR::image(c, x, width, height));
+            x = ggml_silu(c, norm2->forward(ctx, VSR::tokens(c, x)));
+            return out_proj->forward(ctx, x);
+        }
+    };
+
+    class WanAttention : public GGMLBlock {
+        int dim_;
+        int heads_;
+
+    public:
+        explicit WanAttention(const WanVSRConfig& config)
+            : dim_(config.dim), heads_(config.num_heads) {
+            for (const auto& name : {"to_q", "to_k", "to_v", "to_out.0"})
+                blocks[name] = std::make_shared<Linear>(dim_, dim_);
+            blocks["norm_q"] = std::make_shared<RMSNorm>(dim_, 1e-6f);
+            blocks["norm_k"] = std::make_shared<RMSNorm>(dim_, 1e-6f);
+        }
+
+        ggml_tensor* forward(GGMLRunnerContext* ctx, ggml_tensor* x, ggml_tensor* context, ggml_tensor* query_rope, ggml_tensor* key_rope, const VSR::LocalAttention* local, const std::string& cache_name) {
+            auto to_q      = std::dynamic_pointer_cast<Linear>(blocks["to_q"]);
+            auto to_k      = std::dynamic_pointer_cast<Linear>(blocks["to_k"]);
+            auto to_v      = std::dynamic_pointer_cast<Linear>(blocks["to_v"]);
+            auto to_out_0  = std::dynamic_pointer_cast<Linear>(blocks["to_out.0"]);
+            auto norm_q    = std::dynamic_pointer_cast<RMSNorm>(blocks["norm_q"]);
+            auto norm_k    = std::dynamic_pointer_cast<RMSNorm>(blocks["norm_k"]);
+            auto c         = ctx->ggml_ctx;
+            auto q         = norm_q->forward(ctx, to_q->forward(ctx, x));
+            auto past_k    = ctx->get_cache_tensor(cache_name + ".key");
+            auto past_v    = ctx->get_cache_tensor(cache_name + ".value");
+            ggml_tensor* k = nullptr;
+            ggml_tensor* v = nullptr;
+            if (context && past_k) {
+                k = past_k;
+                v = past_v;
+            } else {
+                k = norm_k->forward(ctx, to_k->forward(ctx, context ? context : x));
+                v = to_v->forward(ctx, context ? context : x);
+                if (!context && past_k) {
+                    k = ggml_concat(c, past_k, k, 1);
+                    v = ggml_concat(c, past_v, v, 1);
+                }
+                auto retained = [&](ggml_tensor* value) {
+                    if (context || value->ne[1] <= x->ne[1] * 3)
+                        return value;
+                    // The next attention window adds its current frame to these three previous frames.
+                    const int64_t keep = x->ne[1] * 3;
+                    return ggml_cont(c, ggml_view_2d(c, value, value->ne[0], keep, value->nb[1], (value->ne[1] - keep) * value->nb[1]));
+                };
+                ctx->cache_tensor(cache_name + ".key", retained(k));
+                ctx->cache_tensor(cache_name + ".value", retained(v));
+            }
+            ggml_tensor* out;
+            if (local) {
+                q   = VSR::apply_rope(ctx, q, query_rope, heads_);
+                k   = VSR::apply_rope(ctx, k, key_rope, heads_);
+                out = local->forward(ctx, q, k, v, heads_);
+            } else {
+                out = ggml_ext_attention_ext(c, ctx->backend, q, k, v, heads_, nullptr, false, ctx->flash_attn_enabled);
+            }
+            return to_out_0->forward(ctx, out);
+        }
+    };
+
+    class WanTransformerBlock : public GGMLBlock {
+        int dim_;
+
+        void init_params(ggml_context* ctx, const String2TensorStorage& weights, const std::string prefix) override {
+            params["scale_shift_table"] = ggml_new_tensor_3d(ctx, GGML_TYPE_F32, dim_, 6, 1);
+        }
+
+    public:
+        explicit WanTransformerBlock(const WanVSRConfig& config)
+            : dim_(config.dim) {
+            blocks["norm1"]          = std::make_shared<LayerNorm>(dim_, 1e-6f, false);
+            blocks["norm2"]          = std::make_shared<LayerNorm>(dim_, 1e-6f, true);
+            blocks["norm3"]          = std::make_shared<LayerNorm>(dim_, 1e-6f, false);
+            blocks["attn1"]          = std::make_shared<WanAttention>(config);
+            blocks["attn2"]          = std::make_shared<WanAttention>(config);
+            blocks["ffn.net.0.proj"] = std::make_shared<Linear>(dim_, config.ffn_dim);
+            blocks["ffn.net.2"]      = std::make_shared<Linear>(config.ffn_dim, dim_);
+        }
+
+        ggml_tensor* forward(GGMLRunnerContext* ctx, ggml_tensor* x, ggml_tensor* text, ggml_tensor* timestep_proj, ggml_tensor* qpe, ggml_tensor* kpe, const VSR::LocalAttention& local, const std::string& name) {
+            auto norm1          = std::dynamic_pointer_cast<LayerNorm>(blocks["norm1"]);
+            auto norm2          = std::dynamic_pointer_cast<LayerNorm>(blocks["norm2"]);
+            auto norm3          = std::dynamic_pointer_cast<LayerNorm>(blocks["norm3"]);
+            auto ffn_net_0_proj = std::dynamic_pointer_cast<Linear>(blocks["ffn.net.0.proj"]);
+            auto ffn_net_2      = std::dynamic_pointer_cast<Linear>(blocks["ffn.net.2"]);
+            auto c              = ctx->ggml_ctx;
+            auto modulation     = ggml_add(c, timestep_proj, params["scale_shift_table"]);
+            auto pieces         = ggml_ext_chunk(c, modulation, 6, 1);
+            auto attn1          = std::dynamic_pointer_cast<WanAttention>(blocks["attn1"]);
+            auto attn2          = std::dynamic_pointer_cast<WanAttention>(blocks["attn2"]);
+            auto y              = attn1->forward(ctx, ggml_ext_modulate(ctx, norm1->forward(ctx, x), pieces[0], pieces[1]), nullptr, qpe, kpe, &local, name + ".attn1");
+            x                   = ggml_add(c, x, ggml_mul(c, y, pieces[2]));
+            x                   = ggml_add(c, x, attn2->forward(ctx, norm2->forward(ctx, x), text, nullptr, nullptr, nullptr, name + ".attn2"));
+            y                   = ggml_ext_modulate(ctx, norm3->forward(ctx, x), pieces[3], pieces[4]);
+            y                   = ffn_net_0_proj->forward(ctx, y);
+            y                   = ffn_net_2->forward(ctx, ggml_ext_gelu(c, y));
+            return ggml_add(c, x, ggml_mul(c, y, pieces[5]));
+        }
+    };
+
+    class WanTransformer3DModel : public GGMLBlock {
+        WanVSRConfig config_;
+
+        void init_params(ggml_context* ctx, const String2TensorStorage&, const std::string) override {
+            params["scale_shift_table"] = ggml_new_tensor_3d(ctx, GGML_TYPE_F32, config_.dim, 2, 1);
+            params["prompt_embeds"]     = ggml_new_tensor_2d(ctx, GGML_TYPE_F32, config_.text_dim, config_.text_len);
+        }
+
+    public:
+        explicit WanTransformer3DModel(const WanVSRConfig& config)
+            : config_(config) {
+            blocks["patch_embedding"]                           = std::make_shared<Conv3d>(config.in_channels, config.dim, std::tuple<int, int, int>{1, 2, 2}, std::tuple<int, int, int>{1, 2, 2});
+            blocks["lq_proj"]                                   = std::make_shared<LQ4xProj>(config);
+            blocks["condition_embedder.time_embedder.linear_1"] = std::make_shared<Linear>(256, config.dim);
+            blocks["condition_embedder.time_embedder.linear_2"] = std::make_shared<Linear>(config.dim, config.dim);
+            blocks["condition_embedder.time_proj"]              = std::make_shared<Linear>(config.dim, config.dim * 6);
+            blocks["condition_embedder.text_embedder.linear_1"] = std::make_shared<Linear>(config.text_dim, config.dim);
+            blocks["condition_embedder.text_embedder.linear_2"] = std::make_shared<Linear>(config.dim, config.dim);
+            for (int i = 0; i < config.num_layers; ++i)
+                blocks["blocks." + std::to_string(i)] = std::make_shared<WanTransformerBlock>(config);
+            blocks["norm_out"] = std::make_shared<LayerNorm>(config.dim, 1e-6f, false);
+            blocks["proj_out"] = std::make_shared<Linear>(config.dim, config.in_channels * 4);
+        }
+
+        ggml_tensor* forward(GGMLRunnerContext* ctx, ggml_tensor* latent, ggml_tensor* lq, ggml_tensor* timestep, ggml_tensor* qpe, ggml_tensor* kpe, const VSR::LocalAttention& local) {
+            auto patch_embedding                           = std::dynamic_pointer_cast<Conv3d>(blocks["patch_embedding"]);
+            auto condition_embedder_time_embedder_linear_1 = std::dynamic_pointer_cast<Linear>(blocks["condition_embedder.time_embedder.linear_1"]);
+            auto condition_embedder_time_embedder_linear_2 = std::dynamic_pointer_cast<Linear>(blocks["condition_embedder.time_embedder.linear_2"]);
+            auto condition_embedder_time_proj              = std::dynamic_pointer_cast<Linear>(blocks["condition_embedder.time_proj"]);
+            auto condition_embedder_text_embedder_linear_1 = std::dynamic_pointer_cast<Linear>(blocks["condition_embedder.text_embedder.linear_1"]);
+            auto condition_embedder_text_embedder_linear_2 = std::dynamic_pointer_cast<Linear>(blocks["condition_embedder.text_embedder.linear_2"]);
+            auto norm_out                                  = std::dynamic_pointer_cast<LayerNorm>(blocks["norm_out"]);
+            auto proj_out                                  = std::dynamic_pointer_cast<Linear>(blocks["proj_out"]);
+            auto c                                         = ctx->ggml_ctx;
+            const int width = int(latent->ne[0]) / 2, height = int(latent->ne[1]) / 2;
+            auto x    = patch_embedding->forward(ctx, latent);
+            x         = VSR::tokens(c, ggml_reshape_4d(c, x, width, height, config_.dim, 1));
+            x         = ggml_add(c, x, std::dynamic_pointer_cast<LQ4xProj>(blocks["lq_proj"])->forward(ctx, lq));
+            auto e    = condition_embedder_time_embedder_linear_1->forward(ctx, timestep);
+            e         = condition_embedder_time_embedder_linear_2->forward(ctx, ggml_silu(c, e));
+            auto e0   = condition_embedder_time_proj->forward(ctx, ggml_silu(c, e));
+            e0        = ggml_reshape_3d(c, e0, config_.dim, 6, 1);
+            auto text = condition_embedder_text_embedder_linear_1->forward(ctx, params["prompt_embeds"]);
+            text      = condition_embedder_text_embedder_linear_2->forward(ctx, ggml_ext_gelu(c, text));
+            for (int i = 0; i < config_.num_layers; ++i) {
+                auto name = "blocks." + std::to_string(i);
+                x         = std::dynamic_pointer_cast<WanTransformerBlock>(blocks[name])->forward(ctx, x, text, e0, qpe, kpe, local, name);
+                sd::ggml_graph_cut::mark_graph_cut(x, "relayvsr." + name, "hidden");
+            }
+            e               = ggml_reshape_3d(c, e, config_.dim, 1, 1);
+            auto modulation = ggml_add(c, params["scale_shift_table"], e);
+            auto pieces     = ggml_ext_chunk(c, modulation, 2, 1);
+            x               = norm_out->forward(ctx, x);
+            x               = ggml_ext_modulate(ctx, x, pieces[0], pieces[1]);
+            x               = proj_out->forward(ctx, x);
+            x               = VSR::pixel_shuffle(c, x, width, height, 2, false);
+            return ggml_reshape_4d(c, x, width * 2, height * 2, 1, config_.in_channels);
+        }
+    };
+
+    struct WanVSRRunner : GGMLRunner {
+        WanVSRConfig config;
+        WanTransformer3DModel model;
+        VSR::GraphInputs inputs;
+        std::map<int, std::unique_ptr<VSR::LocalAttention>> attention;
+        sd::Tensor<float> timestep;
+        int frame = 0;
+
+        WanVSRRunner(ggml_backend_t backend, const String2TensorStorage& weights, int scale, std::shared_ptr<DeviceResidencyManager> manager)
+            : GGMLRunner(backend, manager), config(WanVSRConfig::detect_from_weights(weights, "wan", scale)), model(config), timestep({256}) {
+            model.init(params_ctx, weights, "wan");
+            for (int i = 0; i < 128; ++i) {
+                double angle             = 1000.0 * std::pow(10000.0, -double(i) / 128);
+                timestep.data()[i]       = float(std::cos(angle));
+                timestep.data()[i + 128] = float(std::sin(angle));
+            }
+        }
+
+        std::string get_desc() override { return "RelayVSR Wan"; }
+        void get_param_tensors(std::map<std::string, ggml_tensor*>& tensors) { model.get_param_tensors(tensors, "wan"); }
+        void reset() {
+            runner_end();
+            free_cache_ctx_and_buffer();
+            attention.clear();
+            inputs.clear();
+            frame = 0;
+        }
+
+        sd::Tensor<float> compute(int n_threads, const sd::Tensor<float>& noise, const sd::Tensor<float>& lq) {
+            int width = int(noise.shape()[0]) / 2, height = int(noise.shape()[1]) / 2;
+            int count = std::min(frame + 1, 4);
+            if (!attention.count(count))
+                attention[count] = std::make_unique<VSR::LocalAttention>(width, height, std::vector<std::pair<int, int>>(count, {22, 40}), true);
+            auto graph = [&]() {
+                inputs.begin_graph();
+                attention[count]->begin_graph();
+                auto gf          = new_graph_custom(MAX_GRAPH_SIZE);
+                auto ctx         = get_context(gf);
+                const int origin = std::max(0, frame - 7);
+                std::vector<int> times;
+                for (int i = frame - count + 1; i <= frame; ++i)
+                    times.push_back(i - origin);
+                auto qpe = inputs.rope(&ctx, width, height, {frame - origin}, {44, 42, 42});
+                auto kpe = inputs.rope(&ctx, width, height, times, {44, 42, 42});
+                auto out = model.forward(&ctx, make_input(noise), make_input(lq), make_input(timestep), qpe, kpe, *attention[count]);
+                ggml_build_forward_expand(gf, out);
+                return gf;
+            };
+            auto prediction = restore_trailing_singleton_dims(GGMLRunner::compute(graph, n_threads, false), 4);
+            if (prediction.empty())
+                return {};
+            ++frame;
+            for (int64_t i = 0; i < prediction.numel(); ++i)
+                prediction.data()[i] = noise.data()[i] - prediction.data()[i];
+            return prediction;
+        }
+    };
+
+}  // namespace RelayVSR
+
+#endif  // __SD_MODEL_DIFFUSION_RELAY_VSR_HPP__
diff --git a/src/model/upscaler/flash_vsr.hpp b/src/model/upscaler/flash_vsr.hpp
new file mode 100644
index 0000000..470bfc3
--- /dev/null
+++ b/src/model/upscaler/flash_vsr.hpp
@@ -0,0 +1,253 @@
+#ifndef __SD_MODEL_UPSCALER_FLASH_VSR_HPP__
+#define __SD_MODEL_UPSCALER_FLASH_VSR_HPP__
+
+#include "model/common/vsr.hpp"
+
+namespace RelayVSR {
+
+    struct FlashVSRConfig {
+        int dim            = 512;
+        int depth          = 10;
+        int num_heads      = 8;
+        int num_kv_groups  = 2;
+        int hidden_dim     = 1408;
+        int head_dim       = 1024;
+        int upscale_factor = 4;
+
+        static FlashVSRConfig detect_from_weights(const String2TensorStorage& weights, const std::string& prefix, int scale) {
+            FlashVSRConfig config;
+            config.upscale_factor = scale;
+            auto weight           = [&](const std::string& name) -> const TensorStorage& { return weights.at(prefix + "." + name); };
+            config.dim            = int(weight("backbone.blocks.0.attention.query.weight").ne[1]);
+            config.num_heads      = config.dim / 64;
+            config.num_kv_groups  = int(weight("backbone.blocks.0.attention.key.weight").ne[1]) / 64;
+            config.hidden_dim     = int(weight("backbone.blocks.0.feed_forward.down.weight").logical_ne0());
+            config.head_dim       = int(weight("spatial_head.0.weight").ne[1]);
+            config.depth          = 0;
+            while (weights.count(prefix + ".backbone.blocks." + std::to_string(config.depth) + ".attention.query.weight"))
+                ++config.depth;
+            if ((scale != 2 && scale != 4) || config.dim != 512 || config.depth != 10 || config.num_kv_groups != 2 ||
+                weight("condition_encoder.projection.weight").ne[2] != 48 || weight("residual_projection.weight").ne[1] != 768)
+                throw std::runtime_error("Unsupported RelayVSR Flash architecture");
+            LOG_VERBOSE("flashvsr: dim = %d, depth = %d, hidden_dim = %d, scale = %d", config.dim, config.depth, config.hidden_dim, scale);
+            return config;
+        }
+    };
+
+    class LRFrameEncoder : public GGMLBlock {
+    public:
+        explicit LRFrameEncoder(const FlashVSRConfig& config) {
+            int channels[] = {3, 64, 128, 128};
+            for (int i = 0; i < 3; ++i) {
+                int stride                                = i < 2 ? 2 : 4 / config.upscale_factor;
+                blocks["layers." + std::to_string(i * 2)] = std::make_shared<Conv2d>(channels[i], channels[i + 1], std::pair<int, int>{3, 3}, std::pair<int, int>{stride, stride}, std::pair<int, int>{1, 1});
+            }
+            blocks["layers.6"] = std::make_shared<Conv2d>(128, config.dim, std::pair<int, int>{1, 1});
+            blocks["norm"]     = std::make_shared<RMSNorm>(config.dim, 1e-5f);
+        }
+
+        ggml_tensor* forward(GGMLRunnerContext* ctx, ggml_tensor* x) {
+            auto layers_6 = std::dynamic_pointer_cast<Conv2d>(blocks["layers.6"]);
+            auto norm     = std::dynamic_pointer_cast<RMSNorm>(blocks["norm"]);
+            for (int i = 0; i < 3; ++i)
+                x = ggml_silu(ctx->ggml_ctx, std::dynamic_pointer_cast<Conv2d>(blocks["layers." + std::to_string(i * 2)])->forward(ctx, x));
+            x = layers_6->forward(ctx, x);
+            return norm->forward(ctx, VSR::tokens(ctx->ggml_ctx, x));
+        }
+    };
+
+    class ConditionEncoder : public GGMLBlock {
+    public:
+        explicit ConditionEncoder(const FlashVSRConfig& config) {
+            blocks["projection"] = std::make_shared<Conv2d>(48, config.dim, std::pair<int, int>{1, 1});
+            blocks["norm"]       = std::make_shared<RMSNorm>(config.dim, 1e-5f);
+        }
+
+        ggml_tensor* forward(GGMLRunnerContext* ctx, ggml_tensor* x) {
+            auto projection = std::dynamic_pointer_cast<Conv2d>(blocks["projection"]);
+            auto norm       = std::dynamic_pointer_cast<RMSNorm>(blocks["norm"]);
+            return norm->forward(ctx, VSR::tokens(ctx->ggml_ctx, projection->forward(ctx, x)));
+        }
+    };
+
+    class ConditionedGroupedQueryAttention : public GGMLBlock {
+        FlashVSRConfig config_;
+
+    public:
+        explicit ConditionedGroupedQueryAttention(const FlashVSRConfig& config)
+            : config_(config) {
+            blocks["query"]  = std::make_shared<Linear>(config.dim, config.dim);
+            blocks["output"] = std::make_shared<Linear>(config.dim, config.dim);
+            for (const auto& name : {"key", "value", "condition_key", "condition_value"})
+                blocks[name] = std::make_shared<Linear>(config.dim, 64 * config.num_kv_groups);
+            blocks["key_norm"]   = std::make_shared<RMSNorm>(64, 1e-5f);
+            blocks["value_norm"] = std::make_shared<RMSNorm>(64, 1e-5f);
+        }
+
+        ggml_tensor* forward(GGMLRunnerContext* ctx, ggml_tensor* x, ggml_tensor* qpe, ggml_tensor* kpe, const VSR::LocalAttention& local, const std::string& name, int condition_slot, int start_slot, int end_slot, bool history) {
+            auto query           = std::dynamic_pointer_cast<Linear>(blocks["query"]);
+            auto output          = std::dynamic_pointer_cast<Linear>(blocks["output"]);
+            auto key_norm        = std::dynamic_pointer_cast<RMSNorm>(blocks["key_norm"]);
+            auto value_norm      = std::dynamic_pointer_cast<RMSNorm>(blocks["value_norm"]);
+            auto c               = ctx->ggml_ctx;
+            const bool condition = condition_slot >= 0;
+            auto key             = std::dynamic_pointer_cast<Linear>(blocks[condition ? "condition_key" : "key"]);
+            auto value           = std::dynamic_pointer_cast<Linear>(blocks[condition ? "condition_value" : "value"]);
+            auto q               = query->forward(ctx, x);
+            auto k               = key->forward(ctx, x);
+            auto v               = value->forward(ctx, x);
+            const int64_t count  = x->ne[1];
+            k                    = key_norm->forward(ctx, ggml_reshape_3d(c, k, 64, config_.num_kv_groups, count));
+            v                    = value_norm->forward(ctx, ggml_reshape_3d(c, v, 64, config_.num_kv_groups, count));
+            k                    = ggml_reshape_2d(c, k, 64 * config_.num_kv_groups, count);
+            v                    = ggml_reshape_2d(c, v, 64 * config_.num_kv_groups, count);
+            auto cache_prefix    = name + (condition ? ".condition." + std::to_string(condition_slot) : ".video");
+            auto past_k          = history ? ctx->get_cache_tensor(name + ".video.key") : nullptr;
+            auto past_v          = history ? ctx->get_cache_tensor(name + ".video.value") : nullptr;
+            ctx->cache_tensor(cache_prefix + ".key", k);
+            ctx->cache_tensor(cache_prefix + ".value", v);
+            if (!condition) {
+                auto join = [&](ggml_tensor* current, ggml_tensor* past, const char* suffix) {
+                    auto start = ctx->get_cache_tensor(name + ".condition." + std::to_string(start_slot) + suffix);
+                    auto end   = ctx->get_cache_tensor(name + ".condition." + std::to_string(end_slot) + suffix);
+                    if (!start || !end)
+                        throw std::runtime_error("RelayVSR Flash endpoint cache is missing");
+                    auto value = ggml_concat(c, start, end, 1);
+                    if (past)
+                        value = ggml_concat(c, value, past, 1);
+                    return ggml_concat(c, value, current, 1);
+                };
+                k = join(k, past_k, ".key");
+                v = join(v, past_v, ".value");
+            }
+            q = VSR::apply_rope(ctx, q, qpe, config_.num_heads);
+            k = VSR::apply_rope(ctx, k, kpe, config_.num_kv_groups);
+            return output->forward(ctx, local.forward(ctx, q, k, v, config_.num_heads));
+        }
+    };
+
+    class ConditionedTransformerBlock : public GGMLBlock {
+    public:
+        explicit ConditionedTransformerBlock(const FlashVSRConfig& config) {
+            blocks["attention_norm"]            = std::make_shared<RMSNorm>(config.dim, 1e-5f);
+            blocks["attention"]                 = std::make_shared<ConditionedGroupedQueryAttention>(config);
+            blocks["feed_forward_norm"]         = std::make_shared<RMSNorm>(config.dim, 1e-5f);
+            blocks["feed_forward.gate_up_proj"] = std::make_shared<Linear>(config.dim, config.hidden_dim * 2, false);
+            blocks["feed_forward.down"]         = std::make_shared<Linear>(config.hidden_dim, config.dim, false);
+        }
+
+        ggml_tensor* forward(GGMLRunnerContext* ctx, ggml_tensor* x, ggml_tensor* qpe, ggml_tensor* kpe, const VSR::LocalAttention& local, const std::string& name, int condition_slot, int start_slot, int end_slot, bool history) {
+            auto attention_norm            = std::dynamic_pointer_cast<RMSNorm>(blocks["attention_norm"]);
+            auto feed_forward_norm         = std::dynamic_pointer_cast<RMSNorm>(blocks["feed_forward_norm"]);
+            auto feed_forward_gate_up_proj = std::dynamic_pointer_cast<Linear>(blocks["feed_forward.gate_up_proj"]);
+            auto feed_forward_down         = std::dynamic_pointer_cast<Linear>(blocks["feed_forward.down"]);
+            auto c                         = ctx->ggml_ctx;
+            auto attention                 = std::dynamic_pointer_cast<ConditionedGroupedQueryAttention>(blocks["attention"]);
+            auto y                         = attention->forward(ctx, attention_norm->forward(ctx, x), qpe, kpe, local, name, condition_slot, start_slot, end_slot, history);
+            x                              = ggml_add(c, x, y);
+            y                              = feed_forward_gate_up_proj->forward(ctx, feed_forward_norm->forward(ctx, x));
+            auto parts                     = ggml_ext_chunk(c, y, 2, 0);
+            y                              = ggml_mul(c, ggml_silu(c, parts[0]), parts[1]);
+            return ggml_add(c, x, feed_forward_down->forward(ctx, y));
+        }
+    };
+
+    class FlashVSRConditionNet : public GGMLBlock {
+        FlashVSRConfig config_;
+
+        void init_params(ggml_context* ctx, const String2TensorStorage&, const std::string) override {
+            params["video_type_embedding"]     = ggml_new_tensor_3d(ctx, GGML_TYPE_F32, config_.dim, 1, 1);
+            params["condition_type_embedding"] = ggml_new_tensor_3d(ctx, GGML_TYPE_F32, config_.dim, 1, 1);
+        }
+
+    public:
+        explicit FlashVSRConditionNet(const FlashVSRConfig& config)
+            : config_(config) {
+            blocks["lr_encoder"]        = std::make_shared<LRFrameEncoder>(config);
+            blocks["condition_encoder"] = std::make_shared<ConditionEncoder>(config);
+            for (int i = 0; i < config.depth; ++i)
+                blocks["backbone.blocks." + std::to_string(i)] = std::make_shared<ConditionedTransformerBlock>(config);
+            blocks["spatial_head.0"]      = std::make_shared<Linear>(config.dim, config.head_dim);
+            blocks["residual_projection"] = std::make_shared<Linear>(config.head_dim, 768);
+        }
+
+        ggml_tensor* forward(GGMLRunnerContext* ctx, ggml_tensor* input, ggml_tensor* qpe, ggml_tensor* kpe, const VSR::LocalAttention& local, int condition_slot, int start_slot, int end_slot, bool history) {
+            auto spatial_head_0      = std::dynamic_pointer_cast<Linear>(blocks["spatial_head.0"]);
+            auto residual_projection = std::dynamic_pointer_cast<Linear>(blocks["residual_projection"]);
+            auto c                   = ctx->ggml_ctx;
+            const bool condition     = condition_slot >= 0;
+            ggml_tensor* x;
+            if (condition)
+                x = std::dynamic_pointer_cast<ConditionEncoder>(blocks["condition_encoder"])->forward(ctx, input);
+            else
+                x = std::dynamic_pointer_cast<LRFrameEncoder>(blocks["lr_encoder"])->forward(ctx, input);
+            x = ggml_add(c, x, params[condition ? "condition_type_embedding" : "video_type_embedding"]);
+            for (int i = 0; i < config_.depth; ++i) {
+                auto name = "backbone.blocks." + std::to_string(i);
+                x         = std::dynamic_pointer_cast<ConditionedTransformerBlock>(blocks[name])->forward(ctx, x, qpe, kpe, local, name, condition_slot, start_slot, end_slot, history);
+                sd::ggml_graph_cut::mark_graph_cut(x, "flashvsr." + name, "hidden");
+            }
+            if (condition)
+                return x;
+            x = residual_projection->forward(ctx, ggml_silu(c, spatial_head_0->forward(ctx, x)));
+            return VSR::pixel_shuffle(c, x, local.width, local.height, 16);
+        }
+    };
+
+    struct FlashVSRRunner : GGMLRunner {
+        FlashVSRConfig config;
+        FlashVSRConditionNet model;
+        VSR::GraphInputs inputs;
+        std::map<int, std::unique_ptr<VSR::LocalAttention>> attention;
+        bool history = false;
+
+        FlashVSRRunner(ggml_backend_t backend, const String2TensorStorage& weights, int scale, std::shared_ptr<DeviceResidencyManager> manager)
+            : GGMLRunner(backend, manager), config(FlashVSRConfig::detect_from_weights(weights, "flash", scale)), model(config) {
+            model.init(params_ctx, weights, "flash");
+        }
+        std::string get_desc() override { return "RelayVSR Flash"; }
+        void get_param_tensors(std::map<std::string, ggml_tensor*>& tensors) { model.get_param_tensors(tensors, "flash"); }
+        void reset() {
+            runner_end();
+            free_cache_ctx_and_buffer();
+            attention.clear();
+            inputs.clear();
+            history = false;
+        }
+
+        sd::Tensor<float> compute(int n_threads, const sd::Tensor<float>& input, int condition_slot, int start_slot = 0, int end_slot = 1) {
+            const bool condition = condition_slot >= 0;
+            const int stride     = condition ? 1 : 16 / config.upscale_factor;
+            const int width = int(input.shape()[0]) / stride, height = int(input.shape()[1]) / stride;
+            const int planes = condition ? 1 : history ? 4
+                                                       : 3;
+            if (!attention.count(planes)) {
+                std::vector<std::pair<int, int>> windows(planes, {24, 24});
+                windows[0] = {48, 48};
+                if (!condition)
+                    windows[1] = {48, 48};
+                attention[planes] = std::make_unique<VSR::LocalAttention>(width, height, windows, false);
+            }
+            auto graph = [&]() {
+                inputs.begin_graph();
+                attention[planes]->begin_graph();
+                auto gf                = new_graph_custom(MAX_GRAPH_SIZE);
+                auto ctx               = get_context(gf);
+                auto qpe               = inputs.rope(&ctx, width, height, {0}, {16, 24, 24});
+                std::vector<int> times = condition ? std::vector<int>{0} : history ? std::vector<int>{0, 0, -1, 0}
+                                                                                   : std::vector<int>{0, 0, 0};
+                auto kpe               = inputs.rope(&ctx, width, height, times, {16, 24, 24});
+                auto out               = model.forward(&ctx, make_input(input), qpe, kpe, *attention[planes], condition_slot, start_slot, end_slot, history && !condition);
+                ggml_build_forward_expand(gf, out);
+                return gf;
+            };
+            auto result = restore_trailing_singleton_dims(GGMLRunner::compute(graph, n_threads, false), condition ? 2 : 4);
+            if (!condition && !result.empty())
+                history = true;
+            return result;
+        }
+    };
+
+}  // namespace RelayVSR
+
+#endif  // __SD_MODEL_UPSCALER_FLASH_VSR_HPP__
diff --git a/src/name_conversion.cpp b/src/name_conversion.cpp
index 1f19b11..78a5e10 100644
--- a/src/name_conversion.cpp
+++ b/src/name_conversion.cpp
@@ -5,6 +5,39 @@
 #include "core/util.h"
 #include "name_conversion.h"

+std::string convert_relayvsr_tensor_name(std::string name) {
+    if (!starts_with(name, "wan."))
+        return name;
+    const std::vector<std::pair<std::string, std::string>> mappings = {
+        {"positive_conditioning", "prompt_embeds"},
+        {"lq_proj_in.linear.", "lq_proj.out_proj."},
+        {"lq_proj_in.", "lq_proj."},
+        {"text_embedding.0.", "condition_embedder.text_embedder.linear_1."},
+        {"text_embedding.2.", "condition_embedder.text_embedder.linear_2."},
+        {"time_embedding.0.", "condition_embedder.time_embedder.linear_1."},
+        {"time_embedding.2.", "condition_embedder.time_embedder.linear_2."},
+        {"time_projection.1.", "condition_embedder.time_proj."},
+        {"head.head.", "proj_out."},
+        {"head.modulation", "scale_shift_table"},
+        {".norm3.", ".norm2."},
+        {".modulation", ".scale_shift_table"},
+        {".ffn.0.", ".ffn.net.0.proj."},
+        {".ffn.2.", ".ffn.net.2."},
+        {".self_attn.", ".attn1."},
+        {".cross_attn.", ".attn2."},
+        {".q.", ".to_q."},
+        {".k.", ".to_k."},
+        {".v.", ".to_v."},
+        {".o.", ".to_out.0."},
+    };
+    for (const auto& mapping : mappings) {
+        auto pos = name.find(mapping.first);
+        if (pos != std::string::npos)
+            name.replace(pos, mapping.first.size(), mapping.second);
+    }
+    return name;
+}
+
 void replace_with_name_map(std::string& name, const std::vector<std::pair<std::string, std::string>>& name_map) {
     for (auto kv : name_map) {
         size_t pos = name.find(kv.first);
diff --git a/src/name_conversion.h b/src/name_conversion.h
index 3fefcf7..8d90c7e 100644
--- a/src/name_conversion.h
+++ b/src/name_conversion.h
@@ -10,5 +10,6 @@ bool is_diffusion_model_name(const std::string& name);
 bool is_first_stage_model_name(const std::string& name);

 std::string convert_tensor_name(std::string name, SDVersion version);
+std::string convert_relayvsr_tensor_name(std::string name);

-#endif  // __NAME_CONVERSTION_H__
\ No newline at end of file
+#endif  // __NAME_CONVERSTION_H__
diff --git a/src/pipeline/relay_vsr.cpp b/src/pipeline/relay_vsr.cpp
new file mode 100644
index 0000000..bc5cad7
--- /dev/null
+++ b/src/pipeline/relay_vsr.cpp
@@ -0,0 +1,209 @@
+#include "pipeline/video_upscale.h"
+
+#include <climits>
+
+#include "core/rng_philox.hpp"
+#include "generation_info.h"
+#include "model/diffusion/relay_vsr.hpp"
+#include "model/upscaler/flash_vsr.hpp"
+#include "name_conversion.h"
+
+namespace sd {
+    namespace pipeline {
+
+        static sd::Tensor<float> prepare_vsr_frame(const sd_image_t& frame, int width, int height) {
+            auto result = sd_image_to_tensor(frame, -1, -1, false);
+            result /= 127.5f;
+            result -= 1.f;
+            if (width > int(frame.width)) {
+                auto edge    = sd::ops::slice(result, 0, frame.width - 1, frame.width);
+                auto padding = sd::zeros<float>({width - frame.width, frame.height, 3, 1}) + edge;
+                result       = sd::ops::concat(result, padding, 0);
+            }
+            if (height > int(frame.height)) {
+                auto edge    = sd::ops::slice(result, 1, frame.height - 1, frame.height);
+                auto padding = sd::zeros<float>({width, height - frame.height, 3, 1}) + edge;
+                result       = sd::ops::concat(result, padding, 1);
+            }
+            return result;
+        }
+
+        static sd::Tensor<float> prepare_vsr_lq(const sd::Tensor<float>& frame, int scale) {
+            auto input = frame;
+            if (scale == 4)
+                input = sd::ops::interpolate(frame, {frame.shape()[0] * 4, frame.shape()[1] * 4, 3, 1}, sd::ops::InterpolateMode::Bilinear);
+            const int patch = 4 * scale;
+            const int width = int(input.shape()[0]), height = int(input.shape()[1]);
+            input.reshape_({patch, width / patch, patch, height / patch, 3, 1});
+            input.permute_({1, 3, 0, 2, 4, 5});
+            input.reshape_({width / patch, height / patch, 3 * patch * patch, 1});
+            return input;
+        }
+
+        class RelayVSRUpscaler : public VideoUpscaleModel {
+            std::unique_ptr<RelayVSR::WanVSRRunner> wan_;
+            std::unique_ptr<RelayVSR::FlashVSRRunner> flash_;
+            int scale_     = 0;
+            int n_threads_ = 1;
+
+        public:
+            bool init(VideoUpscaleRuntime& runtime, const String2TensorStorage& source_weights, int upscale_factor) override {
+                if (upscale_factor != 2 && upscale_factor != 4) {
+                    LOG_ERROR("RelayVSR requires an explicit upscale factor of 2 or 4 matching both checkpoints");
+                    return false;
+                }
+                scale_             = upscale_factor;
+                n_threads_         = runtime.n_threads;
+                auto wan_backend   = runtime.backends.runtime_backend(SDBackendModule::DIFFUSION);
+                auto flash_backend = runtime.backends.runtime_backend(SDBackendModule::VAE);
+                auto wan_params    = runtime.backends.params_backend(SDBackendModule::DIFFUSION);
+                auto flash_params  = runtime.backends.params_backend(SDBackendModule::VAE);
+                String2TensorStorage weights;
+                std::map<std::string, std::string> source_names;
+                for (const auto& [name, storage] : source_weights) {
+                    auto canonical = name;
+                    if (starts_with(canonical, "diffusion."))
+                        canonical = "wan." + canonical.substr(10);
+                    else if (starts_with(canonical, "vae."))
+                        canonical = "flash." + canonical.substr(4);
+                    canonical = convert_relayvsr_tensor_name(canonical);
+                    if (!source_names.emplace(canonical, name).second)
+                        throw std::runtime_error("Duplicate RelayVSR weight name: " + canonical);
+                    weights[canonical]      = storage;
+                    weights[canonical].name = canonical;
+                }
+                wan_                = std::make_unique<RelayVSR::WanVSRRunner>(wan_backend, weights, upscale_factor, runtime.manager);
+                flash_              = std::make_unique<RelayVSR::FlashVSRRunner>(flash_backend, weights, upscale_factor, runtime.manager);
+                auto register_model = [&](auto& runner, ModelComponent component, SDBackendModule module, ggml_backend_t compute, ggml_backend_t params) {
+                    std::map<std::string, ggml_tensor*> tensors, sources;
+                    runner->get_param_tensors(tensors);
+                    for (const auto& [name, tensor] : tensors) {
+                        auto source = source_names.find(name);
+                        if (source == source_names.end())
+                            throw std::runtime_error("Missing RelayVSR tensor: " + name);
+                        sources.emplace(source->second, tensor);
+                        ggml_set_name(tensor, source->second.c_str());
+                    }
+                    runner->set_flash_attention_enabled(true);
+                    return runtime.manager->register_param_tensors(component, std::move(sources),
+                                                                   runtime.backends.params_backend_is_disk(module) ? ModelManager::ResidencyMode::Disk : ModelManager::ResidencyMode::ParamBackend,
+                                                                   compute, params);
+                };
+                if (!register_model(wan_, ModelComponent::Diffusion, SDBackendModule::DIFFUSION, wan_backend, wan_params) ||
+                    !register_model(flash_, ModelComponent::VAE, SDBackendModule::VAE, flash_backend, flash_params) ||
+                    !runtime.manager->validate_registered_tensors())
+                    return false;
+                return true;
+            }
+
+            void end() override {
+                if (wan_)
+                    wan_->runner_end();
+                if (flash_)
+                    flash_->runner_end();
+            }
+
+            bool upscale(const sd_video_upscale_params_t& params, sd_video_generation_result_t* result) override {
+                const auto* frames    = params.frames;
+                const int frame_count = params.frame_count, fps = params.fps, window_size = params.window_size;
+                const int64_t seed = params.seed;
+                if (window_size < 2) {
+                    LOG_ERROR("RelayVSR requires a reference window of at least two frames");
+                    return false;
+                }
+                if (frames[0].width > uint32_t(INT_MAX / scale_ - 32) || frames[0].height > uint32_t(INT_MAX / scale_ - 32))
+                    return false;
+                struct Reset {
+                    RelayVSRUpscaler* model;
+                    ~Reset() {
+                        model->wan_->reset();
+                        model->flash_->reset();
+                    }
+                } reset{this};
+                wan_->reset();
+                flash_->reset();
+                const int stride    = 16 / scale_;
+                const int alignment = 2 * stride;
+                const int width     = (int(frames[0].width) + alignment - 1) / alignment * alignment;
+                const int height    = (int(frames[0].height) + alignment - 1) / alignment * alignment;
+                PhiloxRNG rng;
+                rng.manual_seed(uint64_t(seed));
+                auto keyframe = [&](int index, int slot) {
+                    LOG_INFO("RelayVSR reference frame %d/%d", index + 1, frame_count);
+                    auto input = prepare_vsr_frame(frames[index], width, height);
+                    sd::Tensor<float> noise({width / stride, height / stride, 1, 48});
+                    auto values = rng.randn(uint32_t(noise.numel()));
+                    std::copy(values.begin(), values.end(), noise.data());
+                    auto latent = wan_->compute(n_threads_, noise, prepare_vsr_lq(input, scale_));
+                    if (latent.empty())
+                        return false;
+                    latent.reshape_({width / stride, height / stride, 48, 1});
+                    return !flash_->compute(n_threads_, latent, slot).empty();
+                };
+                int start_slot = 0;
+                if (!keyframe(0, start_slot))
+                    return false;
+                for (int first = 0; first < frame_count;) {
+                    const int last = first + std::min(window_size - 1, frame_count - 1 - first);
+                    int end_slot   = last == first ? start_slot : 1 - start_slot;
+                    if (last != first && !keyframe(last, end_slot))
+                        return false;
+                    flash_->history = false;
+                    for (int i = first; i <= last; ++i) {
+                        auto input    = prepare_vsr_frame(frames[i], width, height);
+                        auto residual = flash_->compute(n_threads_, input, -1, start_slot, end_slot);
+                        if (residual.empty())
+                            return false;
+                        if (first != 0 && i == first)
+                            continue;
+                        auto output   = sd::ops::interpolate(input, {width * scale_, height * scale_, 3, 1}, sd::ops::InterpolateMode::Bicubic);
+                        auto& image   = result->frames[i];
+                        image.width   = frames[i].width * scale_;
+                        image.height  = frames[i].height * scale_;
+                        image.channel = 3;
+                        output += residual;
+                        output += 1.f;
+                        output *= 127.5f;
+                        output = sd::ops::slice(sd::ops::slice(output, 0, 0, image.width), 1, 0, image.height);
+                        if (!std::all_of(output.values().begin(), output.values().end(), [](float value) { return std::isfinite(value); }))
+                            throw std::runtime_error("RelayVSR produced non-finite pixels");
+                        output = sd::ops::clamp(output, 0.f, 255.f);
+                        output.permute_({2, 0, 1, 3});
+                        image.data = static_cast<uint8_t*>(malloc(size_t(image.width) * image.height * 3));
+                        if (!image.data)
+                            throw std::bad_alloc();
+                        std::transform(output.values().begin(), output.values().end(), image.data, [](float value) { return uint8_t(value); });
+                        LOG_INFO("RelayVSR output frame %d/%d", i + 1, frame_count);
+                        if (auto progress = sd_get_progress_callback())
+                            progress(i + 1, frame_count, 0.f, sd_get_progress_callback_data());
+                    }
+                    if (last == frame_count - 1)
+                        break;
+                    first      = last;
+                    start_slot = end_slot;
+                }
+                auto info                      = sd::upscale_generation_info(scale_);
+                info["kind"]                   = "video";
+                info["upscale"]["model"]       = "relayvsr";
+                info["upscale"]["window_size"] = window_size;
+                info["seed"]                   = seed;
+                info["fps"]                    = fps;
+                info["video_frames"]           = frame_count;
+                result->generation_info        = sd::copy_generation_info(info);
+                if (!result->generation_info)
+                    throw std::bad_alloc();
+                return true;
+            }
+        };
+
+        bool is_relay_vsr_model(const String2TensorStorage& weights) {
+            return (weights.count("diffusion.positive_conditioning") || weights.count("diffusion.prompt_embeds")) &&
+                   (weights.count("diffusion.lq_proj_in.conv1.weight") || weights.count("diffusion.lq_proj.conv1.weight"));
+        }
+
+        std::unique_ptr<VideoUpscaleModel> create_relay_vsr_upscaler() {
+            return std::make_unique<RelayVSRUpscaler>();
+        }
+
+    }  // namespace pipeline
+}  // namespace sd
diff --git a/src/pipeline/video_upscale.cpp b/src/pipeline/video_upscale.cpp
new file mode 100644
index 0000000..5b34a92
--- /dev/null
+++ b/src/pipeline/video_upscale.cpp
@@ -0,0 +1,143 @@
+#include "pipeline/video_upscale.h"
+
+#include <climits>
+
+#include "core/util.h"
+
+namespace sd {
+    namespace pipeline {
+
+        VideoUpscaler::~VideoUpscaler() {
+            if (model_)
+                model_->end();
+            // ModelManager retains parameter pointers owned by the model runners.
+            runtime_.manager.reset();
+            model_.reset();
+        }
+
+        bool VideoUpscaler::init(const sd_video_upscaler_ctx_params_t& params) {
+            if (!params.diffusion_model_path || !*params.diffusion_model_path ||
+                !params.vae_path || !*params.vae_path || params.upscale_factor <= 0) {
+                LOG_ERROR("video upscale requires diffusion and decoder model paths and a positive upscale factor");
+                return false;
+            }
+            upscale_factor_    = params.upscale_factor;
+            runtime_.n_threads = params.n_threads > 0 ? params.n_threads : sd_get_num_physical_cores();
+            executor_          = std::make_unique<sd::ParallelExecutor>(runtime_.n_threads);
+            sd::ParallelScope scope(executor_.get());
+            std::string error;
+            if (!runtime_.backends.init(params.backend, params.params_backend, nullptr, &error)) {
+                LOG_ERROR("video upscaler backend: %s", error.c_str());
+                return false;
+            }
+            for (auto module : {SDBackendModule::DIFFUSION, SDBackendModule::VAE}) {
+                if (!runtime_.backends.runtime_backend(module) || !runtime_.backends.params_backend(module))
+                    return false;
+            }
+            ModelLoader loader;
+            if (!loader.init_from_file(params.diffusion_model_path, "diffusion.") ||
+                !loader.init_from_file(params.vae_path, "vae."))
+                return false;
+            const auto& weights = loader.get_tensor_storage_map();
+            if (is_relay_vsr_model(weights))
+                model_ = create_relay_vsr_upscaler();
+            else {
+                LOG_ERROR("unsupported video upscale model architecture");
+                return false;
+            }
+            runtime_.manager = std::make_shared<ModelManager>();
+            runtime_.manager->set_n_threads(runtime_.n_threads);
+            if (!runtime_.manager->set_loader(loader))
+                return false;
+            return model_->init(runtime_, weights, upscale_factor_);
+        }
+
+        bool VideoUpscaler::upscale(const sd_video_upscale_params_t& params, sd_video_generation_result_t** result_out) {
+            if (!result_out)
+                return false;
+            *result_out = nullptr;
+            if (!model_ || !params.frames || params.frame_count <= 0 || params.fps <= 0) {
+                LOG_ERROR("video upscale requires nonempty RGB frames and positive FPS");
+                return false;
+            }
+            const auto& first = params.frames[0];
+            if (!first.width || !first.height || first.width > uint32_t(INT_MAX / upscale_factor_) ||
+                first.height > uint32_t(INT_MAX / upscale_factor_))
+                return false;
+            for (int i = 0; i < params.frame_count; ++i) {
+                const auto& frame = params.frames[i];
+                if (!frame.data || frame.channel != 3 || frame.width != first.width || frame.height != first.height) {
+                    LOG_ERROR("video upscale input frames must have equal dimensions and three RGB channels");
+                    return false;
+                }
+            }
+            sd::ParallelScope scope(executor_.get());
+            auto result = std::unique_ptr<sd_video_generation_result_t, decltype(&free_sd_video_generation_result)>(
+                static_cast<sd_video_generation_result_t*>(calloc(1, sizeof(sd_video_generation_result_t))), free_sd_video_generation_result);
+            if (!result)
+                return false;
+            result->frames = static_cast<sd_image_t*>(calloc(params.frame_count, sizeof(sd_image_t)));
+            if (!result->frames)
+                return false;
+            result->frame_count = params.frame_count;
+            result->fps         = params.fps;
+            if (!model_->upscale(params, result.get()))
+                return false;
+            *result_out = result.release();
+            return true;
+        }
+
+    }  // namespace pipeline
+}  // namespace sd
+
+struct video_upscaler_ctx_t {
+    sd::pipeline::VideoUpscaler upscaler;
+};
+
+void sd_video_upscaler_ctx_params_init(sd_video_upscaler_ctx_params_t* params) {
+    if (!params)
+        return;
+    *params           = {};
+    params->n_threads = sd_get_num_physical_cores();
+}
+
+void sd_video_upscale_params_init(sd_video_upscale_params_t* params) {
+    if (!params)
+        return;
+    *params             = {};
+    params->fps         = 24;
+    params->seed        = 42;
+    params->window_size = 16;
+}
+
+video_upscaler_ctx_t* new_video_upscaler_ctx(const sd_video_upscaler_ctx_params_t* params) {
+    if (!params)
+        return nullptr;
+    try {
+        auto ctx = std::make_unique<video_upscaler_ctx_t>();
+        if (!ctx->upscaler.init(*params))
+            return nullptr;
+        return ctx.release();
+    } catch (const std::exception& error) {
+        LOG_ERROR("video upscaler initialization failed: %s", error.what());
+        return nullptr;
+    }
+}
+
+bool upscale_video(video_upscaler_ctx_t* ctx, const sd_video_upscale_params_t* params, sd_video_generation_result_t** result_out) {
+    if (!result_out)
+        return false;
+    *result_out = nullptr;
+    if (!ctx || !params)
+        return false;
+    try {
+        return ctx->upscaler.upscale(*params, result_out);
+    } catch (const std::exception& error) {
+        LOG_ERROR("video upscale failed: %s", error.what());
+        return false;
+    }
+}
+
+void free_video_upscaler_ctx(video_upscaler_ctx_t* ctx) {
+    delete ctx;
+}
diff --git a/src/pipeline/video_upscale.h b/src/pipeline/video_upscale.h
new file mode 100644
index 0000000..62d0af1
--- /dev/null
+++ b/src/pipeline/video_upscale.h
@@ -0,0 +1,46 @@
+#ifndef __SD_PIPELINE_VIDEO_UPSCALE_H__
+#define __SD_PIPELINE_VIDEO_UPSCALE_H__
+
+#include <memory>
+
+#include "core/ggml_extend_backend.h"
+#include "core/tensor.hpp"
+#include "model_manager.h"
+#include "stable-diffusion.h"
+
+namespace sd {
+    namespace pipeline {
+
+        struct VideoUpscaleRuntime {
+            SDBackendManager backends;
+            std::shared_ptr<ModelManager> manager;
+            int n_threads = 1;
+        };
+
+        class VideoUpscaleModel {
+        public:
+            virtual ~VideoUpscaleModel()                                                                             = default;
+            virtual bool init(VideoUpscaleRuntime& runtime, const String2TensorStorage& weights, int upscale_factor) = 0;
+            virtual void end()                                                                                       = 0;
+            virtual bool upscale(const sd_video_upscale_params_t& params, sd_video_generation_result_t* result)      = 0;
+        };
+
+        bool is_relay_vsr_model(const String2TensorStorage& weights);
+        std::unique_ptr<VideoUpscaleModel> create_relay_vsr_upscaler();
+
+        class VideoUpscaler {
+            VideoUpscaleRuntime runtime_;
+            int upscale_factor_ = 0;
+            std::unique_ptr<sd::ParallelExecutor> executor_;
+            std::unique_ptr<VideoUpscaleModel> model_;
+
+        public:
+            ~VideoUpscaler();
+            bool init(const sd_video_upscaler_ctx_params_t& params);
+            bool upscale(const sd_video_upscale_params_t& params, sd_video_generation_result_t** result_out);
+        };
+
+    }  // namespace pipeline
+}  // namespace sd
+
+#endif  // __SD_PIPELINE_VIDEO_UPSCALE_H__