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 =?UTF-8?q?=E2=86=92HEAD=20perf=20measurement=20(#155)?=
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Headless benchmark around the native Sponza RT scene: times setup and a
measured Render() loop over the full multi-mesh atrium, prints BENCH
metrics, and exits. Includes run-bench.sh and a README documenting the
methodology and the measured net gain from #40 to current master.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
---
 examples/SponzaBench/README.md       | 131 ++++++++++++
 examples/SponzaBench/closesthit.glsl |  16 ++
 examples/SponzaBench/main.cpp        | 306 +++++++++++++++++++++++++++
 examples/SponzaBench/miss.glsl       |  11 +
 examples/SponzaBench/project.cpp     |  60 ++++++
 examples/SponzaBench/raygen.glsl     |  52 +++++
 examples/SponzaBench/run-bench.sh    |  40 ++++
 7 files changed, 616 insertions(+)
 create mode 100644 examples/SponzaBench/README.md
 create mode 100644 examples/SponzaBench/closesthit.glsl
 create mode 100644 examples/SponzaBench/main.cpp
 create mode 100644 examples/SponzaBench/miss.glsl
 create mode 100644 examples/SponzaBench/project.cpp
 create mode 100644 examples/SponzaBench/raygen.glsl
 create mode 100755 examples/SponzaBench/run-bench.sh

diff --git a/examples/SponzaBench/README.md b/examples/SponzaBench/README.md
new file mode 100644
index 0000000..fdf3426
--- /dev/null
+++ b/examples/SponzaBench/README.md
@@ -0,0 +1,131 @@
+# SponzaBench — measuring the post-#40 performance work
+
+This example exists to answer issue **#155**: *starting with #40 a lot of
+performance-related issues were merged — what is the net performance gain,
+measured in a representative scene (Sponza)?*
+
+It is a headless benchmark harness built around the **native Vulkan**
+Sponza ray-tracing scene. Same asset bundle and camera as
+[`examples/Sponza`](../Sponza), but instead of opening an interactive
+window it times the work and prints machine-readable `BENCH …` lines, then
+exits.
+
+## What it measures
+
+* **setup** — process start through the first command submission: asset
+  decompression, BLAS build per mesh group, the multi-instance TLAS, the
+  RT pipeline, GPU memory placement and the descriptor writes. This is the
+  window most of the post-#40 *native* perf work acts on.
+* **frames** — a warmup followed by a measured loop calling
+  `Window::Render()`, reporting per-frame wall-clock stats and throughput.
+
+Unlike the interactive Sponza example — which is single-material on native
+because of the hit-shader dynamic-`descriptor_heap`-index driver fault
+(see `examples/Sponza/README.md`) — SponzaBench's closest-hit shades from
+barycentric coordinates and samples **no** texture, so it can build the
+**full multi-mesh atrium** (25 mesh groups, ~262 k triangles) as one
+multi-instance TLAS. The albedo is still decompressed and uploaded during
+setup (to keep that path in the measurement) but is not bound.
+
+## Running
+
+```bash
+cd examples/SponzaBench
+crafter-build                       # native Vulkan
+# from the produced bin dir:
+VK_LOADER_LAYERS_DISABLE='~all~' \
+CRAFTER_PRESENT_IMMEDIATE=1 \
+BENCH_WARMUP=200 BENCH_FRAMES=2000 BENCH_MESHES=25 ./SponzaBench
+```
+
+`run-bench.sh <bindir> <label> <meshes> <reps> [--cold]` runs it N times
+and reports the median / min / max of each metric.
+
+Environment knobs:
+
+| var | effect |
+|---|---|
+| `CRAFTER_PRESENT_IMMEDIATE=1` | uncapped present mode — without it FIFO pins frame time to the compositor's vblank (~60 Hz) and steady-state throughput can't be seen. |
+| `VK_LOADER_LAYERS_DISABLE='~all~'` | disable the validation layer. The engine enables Khronos validation **and GPU-assisted validation** unconditionally; that adds large, version-dependent overhead and must be off for a representative measurement. |
+| `BENCH_WARMUP` / `BENCH_FRAMES` | warmup and measured frame counts (default 200 / 2000). |
+| `BENCH_MESHES` | cap on mesh groups loaded (default: all 25). A small cap shrinks GPU work so per-frame **CPU** cost dominates; the full scene is GPU-traversal bound. |
+| `BENCH_CLEAN_EXIT=1` | exit via `std::exit` (runs `atexit`, which writes the #69 pipeline cache) instead of the default hard `_Exit`. Used once to seed `pipeline_cache.bin` for a warm-cache measurement. |
+
+## Results — #40 vs current master
+
+Measured on this repo's CI box: **NVIDIA RTX 4090**, driver `610.43.02`,
+1280×720, validation disabled, `IMMEDIATE` present, 200 warmup + 2000
+measured frames, **median of 9 runs**. "#40" is commit `1451e3a` (the #40
+merge); "HEAD" is current master. The *same* SponzaBench sources were
+built against each library revision (a git worktree at #40).
+
+### Full atrium — 25 meshes / ~262 k triangles (GPU-traversal bound)
+
+| metric | #40 | HEAD | Δ |
+|---|---:|---:|---:|
+| setup (cold) ms | 322.7 | 316.6 | **−1.9 %** |
+| setup (warm pipeline cache, #69) ms | 322.7¹ | 313.9 | **−2.7 %** |
+| throughput fps | 7 560 | 7 637 | **+1.0 %** |
+| frame time p50 ms | 0.1311 | 0.1298 | **−1.0 %** |
+| peak host RSS (cold) MB | 336.0 | 344.2 | +2.4 % |
+| peak host RSS (warm cache) MB | 336.0¹ | 332.0 | **−1.2 %** |
+
+¹ #40 predates the disk pipeline cache (#69), so its setup is always the
+cold-compile path.
+
+### Light scene — 1 mesh (deliberately CPU-bound)
+
+| metric | #40 | HEAD | Δ |
+|---|---:|---:|---:|
+| throughput fps | 15 022 | 15 237 | **+1.4 %** |
+| frame time p50 ms | 0.0662 | 0.0650 | **−1.8 %** |
+
+## Interpretation
+
+**The net measured gain in a static Sponza RT scene is small: ~1–2 %
+faster frames, ~2–3 % faster setup, and roughly flat host memory.** That is
+an honest result, and the reason is *what Sponza exercises*, not that the
+perf work was ineffective:
+
+* **Most post-#40 PRs don't touch this workload.** The largest block is UI
+  / text rendering (shaped-run cache, font-atlas dirty uploads, the UI
+  compute-shader rewrites — #46–#57, #61, #122–#129, #132). Sponza has no
+  UI, so those contribute **zero**. A second block optimises **per-frame
+  dynamic uploads** (TLAS dirty-tracking #118, deforming-mesh refit #119,
+  the staging ring #120). A *static* scene builds its TLAS once and never
+  re-uploads, so these don't fire in steady state either. WebGPU-only
+  (#130/#131/#133) and Win32-only (#134) PRs don't apply to a native
+  Vulkan build at all.
+* **The PRs that *do* apply act on setup and memory, not frame time.**
+  Device-local placement (#65/#72/#73/#75), staging release
+  (#66/#67/#114), the pipeline cache (#69) and the deferred-deletion queue
+  (#101/#116) move setup cost and peak memory — which is exactly where the
+  measured ~2–3 % setup change and the warm-cache RSS drop show up. The
+  pipeline cache itself saves ~3 ms here (one RT pipeline) and, more
+  visibly, ~12 MB of peak RSS by skipping the cold shader-compile
+  allocations.
+* **Steady-state frame time is GPU-traversal bound.** With 262 k triangles
+  the per-frame CPU work (barrier scoping #48/#115, cached heap-bind
+  structs #42/#43) is hidden behind GPU traversal, so it can't move the
+  frame time. Shrinking the scene until it is CPU-bound (the light scene
+  above) surfaces the per-frame CPU savings — and even then they are only
+  ~1.8 %, because that CPU path was already cheap.
+
+**Takeaway:** the post-#40 work is real but concentrated in UI/text and
+per-frame dynamic-upload paths; a static, UI-less RT scene is the wrong
+workload to see most of it. To quantify the UI/text gains a separate
+benchmark over a text-heavy `UIRenderer` scene (or an animated/deforming
+scene for the dynamic-upload PRs) would be needed.
+
+## Caveats / notes
+
+* The stock `examples/Sponza` **native** path does not currently compile
+  against the (unpinned) Vulkan-Headers `main`: the
+  `VkResourceDescriptorDataEXT` union no longer has the
+  `pCombinedImageSampler` member the example uses. SponzaBench sidesteps
+  this by not binding a combined image+sampler. (Pre-existing, unrelated to
+  #155 — worth a follow-up to port Sponza to the split sampled-image +
+  sampler-heap model the engine's own UI renderer already uses.)
+* Numbers are CPU/GPU specific. Re-run `run-bench.sh` locally for your
+  hardware; the *deltas* between revisions are the point, not the absolute
+  figures.
diff --git a/examples/SponzaBench/closesthit.glsl b/examples/SponzaBench/closesthit.glsl
new file mode 100644
index 0000000..dcd2a45
--- /dev/null
+++ b/examples/SponzaBench/closesthit.glsl
@@ -0,0 +1,16 @@
+#version 460
+#extension GL_EXT_ray_tracing : enable
+
+// Benchmark closest-hit: shade from the hit's barycentric coordinates.
+// SponzaBench deliberately avoids the descriptor-heap texture sample the
+// interactive Sponza example uses — the point here is to measure the
+// ray-tracing traversal + frame-loop cost, not texturing, and a
+// texture-free hit keeps the host setup portable across library
+// revisions (issue #155).
+hitAttributeEXT vec2 hitAttrs;
+layout(location = 0) rayPayloadInEXT vec3 hitValue;
+
+void main() {
+    vec3 bary = vec3(1.0 - hitAttrs.x - hitAttrs.y, hitAttrs.x, hitAttrs.y);
+    hitValue = bary;
+}
diff --git a/examples/SponzaBench/main.cpp b/examples/SponzaBench/main.cpp
new file mode 100644
index 0000000..9df4375
--- /dev/null
+++ b/examples/SponzaBench/main.cpp
@@ -0,0 +1,306 @@
+// SponzaBench — headless benchmark around the native Sponza RT scene.
+//
+// Identical setup to examples/Sponza (native branch): load the Sponza
+// .cmesh + albedo .ctex, build BLAS/TLAS, wire an RTPass. Instead of
+// opening an interactive window and idling in StartSync(), it times two
+// things and exits:
+//
+//   * setup   — process start through the first command submission
+//               (asset decompress + BLAS/TLAS build + pipeline + memory
+//               placement + descriptor writes), which the bulk of the
+//               post-#40 perf work targets (device-local placement,
+//               staging release, pipeline cache, decompress, ...).
+//   * frames  — a warmup then a measured loop calling Window::Render(),
+//               reporting per-frame wall-clock stats. Run with
+//               CRAFTER_PRESENT_IMMEDIATE=1 to uncap from vblank.
+//
+// Tunables (env): BENCH_WARMUP (default 200), BENCH_FRAMES (default 2000).
+// Output lines are prefixed "BENCH " for easy scraping.
+
+#include "vulkan/vulkan.h"
+
+import Crafter.Graphics;
+import Crafter.Asset;
+import Crafter.Math;
+import Crafter.Event;
+import std;
+
+using namespace Crafter;
+namespace fs = std::filesystem;
+using Clock = std::chrono::steady_clock;
+
+namespace {
+    struct RGBA8 { std::uint8_t r, g, b, a; };
+
+    void RequireAssets(const fs::path& mesh, const fs::path& tex) {
+        if (fs::exists(mesh) && fs::exists(tex)) return;
+        std::println(std::cerr, "[SponzaBench] missing asset(s): {} / {}",
+                     mesh.string(), tex.string());
+        std::abort();
+    }
+
+    // Peak resident set size (high-water mark) in kB, from /proc/self/status.
+    long PeakRSSkB() {
+        std::ifstream st("/proc/self/status");
+        std::string line;
+        while (std::getline(st, line)) {
+            if (line.rfind("VmHWM:", 0) == 0) {
+                long kb = 0;
+                std::sscanf(line.c_str(), "VmHWM: %ld", &kb);
+                return kb;
+            }
+        }
+        return -1;
+    }
+
+    std::size_t EnvSize(const char* name, std::size_t fallback) {
+        if (const char* v = std::getenv(name)) {
+            char* end = nullptr;
+            unsigned long parsed = std::strtoul(v, &end, 10);
+            if (end != v) return static_cast<std::size_t>(parsed);
+        }
+        return fallback;
+    }
+
+    double Ms(std::chrono::nanoseconds ns) {
+        return std::chrono::duration<double, std::milli>(ns).count();
+    }
+}
+
+int main() {
+    const std::size_t warmup = EnvSize("BENCH_WARMUP", 200);
+    const std::size_t frames = EnvSize("BENCH_FRAMES", 2000);
+
+    const auto tProcStart = Clock::now();
+
+    const fs::path texPath  = "tex_0.ctex";
+    RequireAssets("mesh_0.cmesh", texPath);
+
+    // scene.txt (from the asset bundle): line 1 albedoCount, line 2
+    // meshCount, then per-mesh albedo index. We render every mesh group —
+    // unlike the interactive Sponza example, which is single-material on
+    // native because of the hit-shader dynamic-heap-index driver fault.
+    // SponzaBench's hit shader samples no texture, so it can build the
+    // full multi-mesh atrium as one multi-instance TLAS.
+    std::uint32_t albedoCount = 0, meshCount = 0;
+    {
+        std::ifstream manifest("scene.txt");
+        if (!manifest) { std::println(std::cerr, "[SponzaBench] missing scene.txt"); std::abort(); }
+        manifest >> albedoCount >> meshCount;
+    }
+    // BENCH_MESHES caps the number of mesh groups loaded (default: all).
+    // A small cap (e.g. 1) shrinks GPU work so per-frame CPU cost dominates;
+    // the full scene is GPU (traversal) bound.
+    meshCount = std::min<std::uint32_t>(meshCount, EnvSize("BENCH_MESHES", meshCount));
+
+    CompressedTextureAsset loadedTex = LoadCompressedTexture(texPath);
+    std::println("[SponzaBench] scene: {} meshes, {} albedos, {}x{} probe albedo",
+                 meshCount, albedoCount, loadedTex.sizeX, loadedTex.sizeY);
+
+    Device::Initialize();
+    Window window(1280, 720, "SponzaBench");
+    VkCommandBuffer cmd = window.StartInit();
+
+    DescriptorHeapVulkan descriptorHeap;
+    descriptorHeap.Initialize(/*images*/ 2, /*buffers*/ 1, /*samplers*/ 0);
+
+    VkSpecializationMapEntry raygenEntry = { .constantID = 0, .offset = 0, .size = sizeof(std::uint16_t) };
+    VkSpecializationInfo raygenSpec = {
+        .mapEntryCount = 1, .pMapEntries = &raygenEntry,
+        .dataSize = sizeof(std::uint16_t), .pData = &descriptorHeap.bufferStartElement,
+    };
+
+    auto imgSlots    = descriptorHeap.AllocateImageSlots(1);
+    auto bufSlots    = descriptorHeap.AllocateBufferSlots(1);
+
+    std::array<VulkanShader, 3> shaders {{
+        { "raygen.spv",     "main", VK_SHADER_STAGE_RAYGEN_BIT_KHR,      &raygenSpec },
+        { "miss.spv",       "main", VK_SHADER_STAGE_MISS_BIT_KHR,        nullptr     },
+        { "closesthit.spv", "main", VK_SHADER_STAGE_CLOSEST_HIT_BIT_KHR, nullptr     },
+    }};
+    ShaderBindingTableVulkan shaderTable;
+    shaderTable.Init(shaders);
+
+    std::array<VkRayTracingShaderGroupCreateInfoKHR, 1> raygenGroups {{ {
+        .sType = VK_STRUCTURE_TYPE_RAY_TRACING_SHADER_GROUP_CREATE_INFO_KHR,
+        .type = VK_RAY_TRACING_SHADER_GROUP_TYPE_GENERAL_KHR,
+        .generalShader = 0, .closestHitShader = VK_SHADER_UNUSED_KHR,
+        .anyHitShader = VK_SHADER_UNUSED_KHR, .intersectionShader = VK_SHADER_UNUSED_KHR,
+    } }};
+    std::array<VkRayTracingShaderGroupCreateInfoKHR, 1> missGroups {{ {
+        .sType = VK_STRUCTURE_TYPE_RAY_TRACING_SHADER_GROUP_CREATE_INFO_KHR,
+        .type = VK_RAY_TRACING_SHADER_GROUP_TYPE_GENERAL_KHR,
+        .generalShader = 1, .closestHitShader = VK_SHADER_UNUSED_KHR,
+        .anyHitShader = VK_SHADER_UNUSED_KHR, .intersectionShader = VK_SHADER_UNUSED_KHR,
+    } }};
+    std::array<VkRayTracingShaderGroupCreateInfoKHR, 1> hitGroups {{ {
+        .sType = VK_STRUCTURE_TYPE_RAY_TRACING_SHADER_GROUP_CREATE_INFO_KHR,
+        .type = VK_RAY_TRACING_SHADER_GROUP_TYPE_TRIANGLES_HIT_GROUP_KHR,
+        .generalShader = VK_SHADER_UNUSED_KHR, .closestHitShader = 2,
+        .anyHitShader = VK_SHADER_UNUSED_KHR, .intersectionShader = VK_SHADER_UNUSED_KHR,
+    } }};
+
+    PipelineRTVulkan pipeline;
+    pipeline.Init(cmd, raygenGroups, missGroups, hitGroups, shaderTable);
+
+    // One Mesh + RenderingElement3D per mesh group → BLAS each, then a
+    // single multi-instance TLAS. Pointers handed to RenderingElement3D
+    // live in the static vectors, so reserve up-front: a reallocation
+    // would dangle every registered element.
+    static std::vector<Mesh> meshes;
+    static std::vector<RenderingElement3D> renderers;
+    meshes.reserve(meshCount);
+    renderers.reserve(meshCount);
+    std::uint64_t totalVerts = 0, totalIdx = 0;
+    for (std::uint32_t i = 0; i < meshCount; ++i) {
+        const fs::path mp = std::format("mesh_{}.cmesh", i);
+        if (!fs::exists(mp)) continue;
+        CompressedMeshAsset loaded = LoadCompressedMesh(mp);
+        totalVerts += loaded.vertexCount;
+        totalIdx   += loaded.indexCount;
+        meshes.emplace_back();
+        meshes.back().Build(loaded, cmd);
+
+        renderers.emplace_back();
+        RenderingElement3D& r = renderers.back();
+        r.instance = {
+            .transform                              = {},
+            .instanceCustomIndex                    = 0,
+            .mask                                   = 0xFF,
+            .instanceShaderBindingTableRecordOffset = 0,
+            .flags                                  = VK_GEOMETRY_INSTANCE_FORCE_OPAQUE_BIT_KHR,
+            .accelerationStructureReference         = meshes.back().blasAddr,
+        };
+        MatrixRowMajor<float, 4, 3, 1>::Identity()
+            .Store(reinterpret_cast<float*>(r.instance.transform.matrix));
+        RenderingElement3D::Add(&r);
+    }
+    std::println("[SponzaBench] built {} BLAS, {} verts, {} idx total",
+                 renderers.size(), totalVerts, totalIdx);
+
+    Image2D<RGBA8> albedo;
+    albedo.Create(loadedTex.sizeX, loadedTex.sizeY, /*mipLevels*/ 1, cmd,
+                  VK_FORMAT_R8G8B8A8_UNORM,
+                  VK_IMAGE_USAGE_TRANSFER_DST_BIT | VK_IMAGE_USAGE_SAMPLED_BIT,
+                  VK_IMAGE_LAYOUT_SHADER_READ_ONLY_OPTIMAL);
+    albedo.Update(loadedTex, cmd, VK_IMAGE_LAYOUT_SHADER_READ_ONLY_OPTIMAL);
+    // The albedo is uploaded to keep the texture-decompress + staging
+    // setup path in the measured "setup" window, but is not bound — the
+    // closest-hit shades from barycentrics, so only the TLAS + per-frame
+    // output image need descriptors.
+
+    for (std::uint32_t f = 0; f < Window::numFrames; ++f)
+        RenderingElement3D::BuildTLAS(cmd, f);
+
+    window.FinishInit();
+
+    VkDeviceAddressRangeKHR tlasRanges[Window::numFrames];
+    VkImageDescriptorInfoEXT outImgInfos[Window::numFrames];
+    for (std::uint32_t f = 0; f < Window::numFrames; ++f) {
+        tlasRanges[f] = { .address = RenderingElement3D::tlases[f].address };
+        outImgInfos[f] = {
+            .sType = VK_STRUCTURE_TYPE_IMAGE_DESCRIPTOR_INFO_EXT,
+            .pView = &window.imageViews[f],
+            .layout = VK_IMAGE_LAYOUT_GENERAL,
+        };
+    }
+
+    std::vector<VkResourceDescriptorInfoEXT> resources;
+    std::vector<VkHostAddressRangeEXT>       destinations;
+    resources.reserve(Window::numFrames * 2);
+    destinations.reserve(Window::numFrames * 2);
+    for (std::uint32_t f = 0; f < Window::numFrames; ++f) {
+        resources.push_back({
+            .sType = VK_STRUCTURE_TYPE_RESOURCE_DESCRIPTOR_INFO_EXT,
+            .type = VK_DESCRIPTOR_TYPE_ACCELERATION_STRUCTURE_KHR,
+            .data = { .pAddressRange = &tlasRanges[f] },
+        });
+        destinations.push_back({
+            .address = descriptorHeap.resourceHeap[f].value
+                     + descriptorHeap.BufferByteOffset(bufSlots.firstElement),
+            .size = Device::descriptorHeapProperties.bufferDescriptorSize,
+        });
+        resources.push_back({
+            .sType = VK_STRUCTURE_TYPE_RESOURCE_DESCRIPTOR_INFO_EXT,
+            .type = VK_DESCRIPTOR_TYPE_STORAGE_IMAGE,
+            .data = { .pImage = &outImgInfos[f] },
+        });
+        destinations.push_back({
+            .address = descriptorHeap.resourceHeap[f].value
+                     + descriptorHeap.ImageByteOffset(imgSlots.firstElement),
+            .size = Device::descriptorHeapProperties.imageDescriptorSize,
+        });
+    }
+    Device::vkWriteResourceDescriptorsEXT(Device::device,
+        static_cast<std::uint32_t>(resources.size()),
+        resources.data(), destinations.data());
+    for (std::uint32_t f = 0; f < Window::numFrames; ++f) {
+        descriptorHeap.resourceHeap[f].FlushDevice();
+    }
+
+    window.descriptorHeap = &descriptorHeap;
+    RTPass rtPass(&pipeline);
+    window.passes.push_back(&rtPass);
+
+    // ── Setup complete. Everything above is the per-run, one-time cost. ──
+    const auto tSetupDone = Clock::now();
+    const double setupMs = Ms(tSetupDone - tProcStart);
+
+    // ── Warmup: let the pipeline fill (frames-in-flight), caches warm. ──
+    for (std::size_t i = 0; i < warmup; ++i) window.Render();
+
+    // ── Measured loop: per-frame wall-clock around Render(). ────────────
+    std::vector<double> frameMs;
+    frameMs.reserve(frames);
+    const auto tLoopStart = Clock::now();
+    for (std::size_t i = 0; i < frames; ++i) {
+        const auto a = Clock::now();
+        window.Render();
+        const auto b = Clock::now();
+        frameMs.push_back(Ms(b - a));
+    }
+    const auto tLoopEnd = Clock::now();
+    // Drain so the loop's wall-clock isn't charged the GPU tail of the
+    // last few in-flight frames inconsistently across runs.
+    vkQueueWaitIdle(Device::queue);
+
+    const long peakRSS = PeakRSSkB();
+
+    // ── Stats. throughput uses the loop wall-clock (steady-state FPS);
+    //    per-frame percentiles use the sorted per-frame samples. ─────────
+    const double loopWallMs = Ms(tLoopEnd - tLoopStart);
+    std::sort(frameMs.begin(), frameMs.end());
+    auto pct = [&](double p) {
+        if (frameMs.empty()) return 0.0;
+        std::size_t idx = static_cast<std::size_t>(p * (frameMs.size() - 1));
+        return frameMs[idx];
+    };
+    double sum = 0.0; for (double v : frameMs) sum += v;
+    const double meanMs = frameMs.empty() ? 0.0 : sum / frameMs.size();
+
+    std::println("");
+    std::println("BENCH setup_ms        {:.3f}", setupMs);
+    std::println("BENCH frames          {}", frames);
+    std::println("BENCH loop_wall_ms    {:.3f}", loopWallMs);
+    std::println("BENCH fps             {:.1f}", frames / (loopWallMs / 1000.0));
+    std::println("BENCH frame_mean_ms   {:.4f}", meanMs);
+    std::println("BENCH frame_min_ms    {:.4f}", pct(0.0));
+    std::println("BENCH frame_p50_ms    {:.4f}", pct(0.50));
+    std::println("BENCH frame_p99_ms    {:.4f}", pct(0.99));
+    std::println("BENCH frame_max_ms    {:.4f}", pct(1.0));
+    std::println("BENCH peak_rss_kb     {}", peakRSS);
+
+    // The interactive Sponza example never tears Device/Window down (it
+    // loops in StartSync forever); doing so here races GPU-still-in-flight
+    // resources at static-destruction time. The measurement is already
+    // printed, so skip destructors entirely with a hard exit.
+    //
+    // BENCH_CLEAN_EXIT=1 instead exits via std::exit, which runs atexit
+    // handlers (on builds that have the disk pipeline cache, #69, this is
+    // where it is written) before the destructor teardown. Used once to
+    // seed pipeline_cache.bin for a warm-cache setup measurement; the
+    // subsequent destructor race is irrelevant since the data is flushed.
+    std::cout.flush();
+    if (std::getenv("BENCH_CLEAN_EXIT")) std::exit(0);
+    std::_Exit(0);
+}
diff --git a/examples/SponzaBench/miss.glsl b/examples/SponzaBench/miss.glsl
new file mode 100644
index 0000000..909d9ca
--- /dev/null
+++ b/examples/SponzaBench/miss.glsl
@@ -0,0 +1,11 @@
+#version 460
+#extension GL_EXT_ray_tracing : enable
+
+layout(location = 0) rayPayloadInEXT vec3 hitValue;
+
+void main() {
+    // Soft sky gradient based on ray direction Y. The actual ray dir
+    // isn't accessible without an extra payload field; use a flat warm
+    // tone that matches Sponza's interior lighting.
+    hitValue = vec3(0.10, 0.08, 0.06);
+}
diff --git a/examples/SponzaBench/project.cpp b/examples/SponzaBench/project.cpp
new file mode 100644
index 0000000..3557174
--- /dev/null
+++ b/examples/SponzaBench/project.cpp
@@ -0,0 +1,60 @@
+import std;
+import Crafter.Build;
+namespace fs = std::filesystem;
+using namespace Crafter;
+
+// SponzaBench — a headless benchmark harness around the native Sponza
+// ray-tracing scene. Same asset bundle and shaders as examples/Sponza,
+// but main.cpp times setup + a fixed measured frame loop instead of
+// opening an interactive window. Native (Vulkan) only — the point is to
+// measure the native renderer's per-frame and setup cost across library
+// revisions (issue #155: net perf gain from #40 to now).
+constexpr std::string_view kSponzaGitUrl    = "https://github.com/jimmiebergmann/Sponza.git";
+constexpr std::string_view kSponzaCommitSHA = "222338979d32f4f4818466291bdbc29f192b86ba";
+constexpr std::uint16_t    kAlbedoSize      = 1024u;
+
+extern "C" Configuration CrafterBuildProject(std::span<const std::string_view> args) {
+    std::vector<std::string> graphicsArgs(args.begin(), args.end());
+    Configuration* graphics = LocalProject({
+        .projectFile = "../../project.cpp",
+        .args = graphicsArgs,
+    });
+
+    Configuration cfg;
+    cfg.path = "./";
+    cfg.name = "SponzaBench";
+    cfg.outputName = "SponzaBench";
+    cfg.type = ConfigurationType::Executable;
+    ApplyStandardArgs(cfg, args);
+    cfg.dependencies = { graphics };
+
+    std::array<fs::path, 0> ifaces = {};
+    std::array<fs::path, 1> impls = { "main" };
+    cfg.GetInterfacesAndImplementations(ifaces, impls);
+
+    fs::path sponzaRoot = GitFetch({
+        .url    = std::string(kSponzaGitUrl),
+        .commit = std::string(kSponzaCommitSHA),
+    });
+    std::string bundleKey = std::format("{}|{}", kSponzaCommitSHA, kAlbedoSize);
+    auto bundleHash = std::hash<std::string>{}(bundleKey);
+    fs::path bundleDir = fs::path("build") / std::format("sponza-bundle-{:016x}", bundleHash);
+
+    if (auto err = BuildOBJBundle(
+            sponzaRoot / "sponza.obj",
+            sponzaRoot / "sponza.mtl",
+            bundleDir,
+            kAlbedoSize); !err.empty()) {
+        std::println(std::cerr, "Sponza bundle error: {}", err);
+        std::exit(1);
+    }
+
+    for (const auto& entry : fs::directory_iterator(bundleDir)) {
+        if (entry.is_regular_file()) cfg.files.push_back(entry.path());
+    }
+
+    cfg.shaders.emplace_back(fs::path("raygen.glsl"),     std::string("main"), ShaderType::RayGen);
+    cfg.shaders.emplace_back(fs::path("closesthit.glsl"), std::string("main"), ShaderType::ClosestHit);
+    cfg.shaders.emplace_back(fs::path("miss.glsl"),       std::string("main"), ShaderType::Miss);
+    return cfg;
+}
diff --git a/examples/SponzaBench/raygen.glsl b/examples/SponzaBench/raygen.glsl
new file mode 100644
index 0000000..7eafa4b
--- /dev/null
+++ b/examples/SponzaBench/raygen.glsl
@@ -0,0 +1,52 @@
+#version 460
+#extension GL_EXT_ray_tracing : enable
+#extension GL_EXT_shader_image_load_formatted : enable
+#extension GL_EXT_shader_explicit_arithmetic_types_int16 : enable
+#extension GL_EXT_descriptor_heap : enable
+#extension GL_EXT_nonuniform_qualifier : enable
+
+// Specialization constant set from descriptorHeap.bufferStartElement —
+// shared with closesthit.glsl. The TLAS lives at descriptor_heap slot
+// `bufferStart` (it's an SSBO-typed entry), the per-frame output image
+// at heap slot 0.
+layout(constant_id = 0) const uint16_t bufferStart = 0us;
+layout(descriptor_heap) uniform accelerationStructureEXT topLevelAS[];
+layout(descriptor_heap) uniform writeonly image2D image[];
+
+layout(location = 0) rayPayloadEXT vec3 hitValue;
+
+void main() {
+    uvec2 pixel      = gl_LaunchIDEXT.xy;
+    uvec2 resolution = gl_LaunchSizeEXT.xy;
+    vec2  uv         = (vec2(pixel) + 0.5) / vec2(resolution);
+    vec2  ndc        = uv * 2.0 - 1.0;
+
+    // Camera positioned to look down the Sponza atrium axis. Sponza-OBJ
+    // from McGuire's archive is roughly 30 units wide × 13 tall × 18 deep,
+    // axis-aligned, with the floor near y=0 and the atrium centered on
+    // origin. -X faces the long end, so we sit inside looking +X.
+    vec3  origin    = vec3(-10.0, 5.0, 0.0);
+    float aspect    = float(resolution.x) / float(resolution.y);
+    float fov       = radians(70.0);
+    float tanHalf   = tan(fov * 0.5);
+    vec3  direction = normalize(vec3(
+        ndc.x * aspect * tanHalf,
+        -ndc.y * tanHalf,
+        1.0));
+
+    // Rotate +Z forward → +X forward (90° about Y).
+    direction = vec3(direction.z, direction.y, -direction.x);
+
+    traceRayEXT(
+        topLevelAS[bufferStart],
+        gl_RayFlagsNoneEXT,
+        0xff,
+        0, 0, 0,
+        origin,
+        0.001,
+        direction,
+        10000.0,
+        0);
+
+    imageStore(image[0], ivec2(pixel), vec4(hitValue, 1.0));
+}
diff --git a/examples/SponzaBench/run-bench.sh b/examples/SponzaBench/run-bench.sh
new file mode 100755
index 0000000..aafa913
--- /dev/null
+++ b/examples/SponzaBench/run-bench.sh
@@ -0,0 +1,40 @@
+#!/usr/bin/env bash
+# Repeated-measurement harness for SponzaBench. Runs the binary in $BINDIR
+# REPS times for a given mesh cap and reports the median (and min/max) of
+# each BENCH metric. Validation is force-disabled via the loader (it adds
+# huge, version-dependent overhead) and present mode is uncapped so frame
+# time reflects real work rather than the compositor's vblank.
+#
+# Usage: run-bench.sh <bindir> <label> <meshes> <reps> [--cold]
+#   --cold deletes pipeline_cache.bin before EACH run (cold-compile path).
+set -u
+BINDIR="$1"; LABEL="$2"; MESHES="$3"; REPS="$4"; COLD="${5:-}"
+cd "$BINDIR" || exit 1
+
+declare -A vals
+metrics="setup_ms fps frame_mean_ms frame_p50_ms frame_p99_ms peak_rss_kb"
+for m in $metrics; do vals[$m]=""; done
+
+for ((i=0;i<REPS;i++)); do
+  [ "$COLD" = "--cold" ] && rm -f pipeline_cache.bin
+  out=$(VK_LOADER_LAYERS_DISABLE='~all~' CRAFTER_PRESENT_IMMEDIATE=1 \
+        BENCH_WARMUP=200 BENCH_FRAMES=2000 BENCH_MESHES="$MESHES" \
+        ./SponzaBench 2>/dev/null)
+  for m in $metrics; do
+    v=$(echo "$out" | awk -v k="$m" '$1=="BENCH" && $2==k {print $3}')
+    vals[$m]="${vals[$m]} $v"
+  done
+done
+
+med() { tr ' ' '\n' | grep -v '^$' | sort -n | awk '{a[NR]=$1} END{print a[int((NR+1)/2)]}'; }
+lo()  { tr ' ' '\n' | grep -v '^$' | sort -n | head -1; }
+hi()  { tr ' ' '\n' | grep -v '^$' | sort -n | tail -1; }
+
+echo "## $LABEL  (meshes=$MESHES reps=$REPS ${COLD})"
+printf "%-15s %12s %12s %12s\n" metric median min max
+for m in $metrics; do
+  echo -n "$(printf '%-15s' "$m") "
+  printf "%12s %12s %12s\n" \
+    "$(echo "${vals[$m]}" | med)" "$(echo "${vals[$m]}" | lo)" "$(echo "${vals[$m]}" | hi)"
+done
+echo