diff --git a/tools/validate_sage2_vprep.py b/tools/validate_sage2_vprep.py
new file mode 100644
index 0000000..e644d63
--- /dev/null
+++ b/tools/validate_sage2_vprep.py
@@ -0,0 +1,118 @@
+"""Validate Vortex direct Sage2 V preparation against SageAttention 2.2.0."""
+
+from __future__ import annotations
+
+import argparse
+import json
+from pathlib import Path
+
+import torch
+
+from h3_blackwell_runtime.sage2_entry import prepare_v
+from profile_attention_path import summarize
+
+
+def difference(actual: torch.Tensor, expected: torch.Tensor) -> dict:
+    delta = actual.float() - expected.float()
+    return {
+        "equal": torch.equal(actual, expected),
+        "different_elements": int(torch.count_nonzero(actual != expected).item()),
+        "max_abs": delta.abs().max().item() if delta.numel() else 0.0,
+        "mean_abs": delta.abs().mean().item() if delta.numel() else 0.0,
+    }
+
+
+def measure(fn, *, warmup: int, iterations: int) -> dict:
+    for _ in range(warmup):
+        fn()
+    torch.cuda.synchronize()
+    samples = []
+    for _ in range(iterations):
+        started = torch.cuda.Event(enable_timing=True)
+        finished = torch.cuda.Event(enable_timing=True)
+        started.record()
+        fn()
+        finished.record()
+        finished.synchronize()
+        samples.append(started.elapsed_time(finished) / 1000.0)
+    return summarize(samples)
+
+
+def baseline(v: torch.Tensor):
+    import sageattention.core as sage_core
+
+    return sage_core.per_channel_fp8(
+        v, tensor_layout="NHD", scale_max=2.25, smooth_v=False,
+    )
+
+
+def run_case(sequence: int, heads: int, seed: int, warmup: int, iterations: int) -> dict:
+    generator = torch.Generator(device="cuda").manual_seed(seed)
+    storage = torch.randn(
+        (sequence, heads * 128 * 3),
+        generator=generator,
+        device="cuda",
+        dtype=torch.bfloat16,
+    )
+    v = storage[:, heads * 128 * 2 :].view(1, sequence, heads, 128)
+    reference_fp8, reference_scale, _ = baseline(v)
+    candidate_fp8, candidate_scale = prepare_v(v)
+    torch.cuda.synchronize()
+    result = {
+        "sequence": sequence,
+        "heads": heads,
+        "stride": list(v.stride()),
+        "fp8": difference(candidate_fp8, reference_fp8),
+        "scale": difference(candidate_scale, reference_scale),
+    }
+    if sequence >= 1024:
+        result["baseline_timing"] = measure(
+            lambda: baseline(v), warmup=warmup, iterations=iterations,
+        )
+        result["candidate_timing"] = measure(
+            lambda: prepare_v(v), warmup=warmup, iterations=iterations,
+        )
+    return result
+
+
+def parse_args() -> argparse.Namespace:
+    parser = argparse.ArgumentParser(description=__doc__)
+    parser.add_argument("--output", type=Path, required=True)
+    parser.add_argument(
+        "--lengths",
+        nargs="+",
+        type=int,
+        default=(1, 31, 32, 33, 63, 64, 65, 127, 128, 129, 37760, 37761, 37810),
+    )
+    parser.add_argument("--heads", type=int, default=56)
+    parser.add_argument("--seed", type=int, default=440420)
+    parser.add_argument("--warmup", type=int, default=3)
+    parser.add_argument("--iterations", type=int, default=10)
+    return parser.parse_args()
+
+
+def main() -> None:
+    args = parse_args()
+    cases = [
+        run_case(length, args.heads, args.seed + index, args.warmup, args.iterations)
+        for index, length in enumerate(args.lengths)
+    ]
+    report = {
+        "status": "pass" if all(case["fp8"]["equal"] and case["scale"]["equal"] for case in cases) else "fail",
+        "contract": {
+            "tensor_layout": "NHD",
+            "head_dim": 128,
+            "scale_max": 2.25,
+            "output": "Sage2 padded/permuted E4M3 V and FP32 per-channel scale",
+        },
+        "cases": cases,
+    }
+    args.output.parent.mkdir(parents=True, exist_ok=True)
+    args.output.write_text(json.dumps(report, indent=2) + "\n", encoding="utf-8")
+    print(json.dumps(report, indent=2), flush=True)
+    if report["status"] != "pass":
+        raise RuntimeError("Vortex Sage2 V preparation did not match SageAttention 2.2.0")
+
+
+if __name__ == "__main__":
+    main()