commit 4708cdebb2e60a0a4201083a838fb717ec4fd038
Author: biondizzle <biondizzle@gmail.com>
Date:   Wed May 6 23:47:07 2026 +0000

    init commit

diff --git a/README.md b/README.md
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+# DeepSeek V4 Pro → NVFP4 conversion kit
+
+Two paths for converting `sgl-project/DeepSeek-V4-Pro-FP8` (the uniform-FP8 repackage of the original mixed-precision V4 Pro) into NVFP4 for Blackwell inference.
+
+## What's here
+
+| File | Purpose |
+| --- | --- |
+| `inspect_model.py` | Run this first. Prints tensor name patterns, dtypes, FP8 scaling block sizes, and counts of MoE expert/router/norm tensors so you know exactly what you're dealing with before any conversion. |
+| `fp8_to_nvfp4_streaming.py` | **Path A.** Pure tensor-level streaming FP8 → NVFP4 conversion. No model loading, no calibration, weight-only. Low memory, fast, deterministic. Recommended for first run. |
+| `quantize_llmcompressor.py` | **Path B.** `llm-compressor` oneshot with sequential pipeline + activation calibration. Produces W4A4 with calibrated activation scales. Higher quality on activation-sensitive ops but riskier given V4 is two weeks old. |
+| `verify_nvfp4.py` | Loads the produced NVFP4 checkpoint, runs a basic forward pass through one block, checks for NaN/Inf, and dumps a few generated tokens via vLLM. |
+
+## Hardware assumptions
+
+- 8× B200 baremetal, 1.5 TB HBM total
+- 2.7 TB system RAM
+- ≥10 TB free NVMe at `~/nvidia-meeting/`
+
+## Prereqs
+
+```bash
+source ~/nvidia-meeting/venv/bin/activate
+pip install --upgrade torch safetensors transformers tqdm
+pip install --upgrade llmcompressor compressed-tensors  # only needed for Path B
+pip install --upgrade vllm                              # only needed for verify
+```
+
+You'll likely need `transformers` from source for V4 architecture support, and `trust_remote_code=True` everywhere. Stock pip versions may not load V4 yet.
+
+## Recommended order tonight
+
+```bash
+cd ~/nvidia-meeting
+
+# 1. Inspect the FP8 source — 30 seconds, no GPU needed.
+python inspect_model.py DeepSeek-V4-Pro-FP8 | tee inspect.log
+
+# 2. Path A streaming conversion — should run in 2-6 hours dominated by NVMe I/O.
+python fp8_to_nvfp4_streaming.py \
+    --src DeepSeek-V4-Pro-FP8 \
+    --dst DeepSeek-V4-Pro-NVFP4-streaming \
+    --workers 8 \
+    2>&1 | tee path_a.log
+
+# 3. Quick sanity check — does it load and forward-pass?
+python verify_nvfp4.py DeepSeek-V4-Pro-NVFP4-streaming
+
+# 4. Path B (overnight). Run only after Path A succeeds. 24-72 hours.
+python quantize_llmcompressor.py \
+    --src DeepSeek-V4-Pro-FP8 \
+    --dst DeepSeek-V4-Pro-NVFP4-llmcompressor \
+    --num-samples 256 \
+    --max-seq-len 4096 \
+    2>&1 | tee path_b.log
+```
+
+## Path A — what it does
+
+1. Reads `model.safetensors.index.json` to map every tensor to its shard.
+2. Classifies every tensor:
+   - **Preserve** (copied bit-for-bit): `lm_head`, `embed_tokens`, MoE router gates (`*.mlp.gate`), all norms, V4-specific attention indexer/scoring tensors, mHC residual mixing weights.
+   - **Quantize**: any FP8 weight that has a corresponding `*.weight_scale_inv` companion (i.e. real GEMM weights).
+3. For every quantizable weight:
+   - Dequantizes FP8 E4M3 → FP32 using the source's per-block scales (auto-detects 128×128 blocks).
+   - Computes NVFP4 dual scales: per-tensor `weight_scale_2 = amax / (6.0 * 448.0)` and per-16-element-block `weight_scale = block_amax / (6.0 * weight_scale_2)` cast to FP8 E4M3.
+   - Quantizes FP32 → E2M1 representable values `{0, ±0.5, ±1, ±1.5, ±2, ±3, ±4, ±6}`.
+   - Packs two 4-bit values per `uint8` byte.
+4. **MoE pair handling**: detects `gate_proj` (w1) + `up_proj` (w3) of each expert and computes a joint `weight_scale_2` across both, since vLLM's fused MoE kernel requires them to share that global scale.
+5. Streams output to new shards (~5 GB each) with a fresh `model.safetensors.index.json` and copies all non-tensor files (config, tokenizer, etc.) verbatim.
+
+**This is weight-only NVFP4.** Activation quantization is not done here — you get W4A16 effective behavior at runtime unless your inference engine generates dynamic per-group activation scales. vLLM does generate per-group activation scales dynamically at inference, so this is fine for most use cases.
+
+## Path B — what it does
+
+1. Loads the FP8 model via `transformers` with `device_map="auto"` and the offload folder pointing at NVMe. With 2.7 TB RAM, the FP8 weights (~865 GB) sit in RAM; activations and per-layer BF16 promotion happen on the B200s.
+2. Loads a calibration set (default 256 samples of `HuggingFaceH4/ultrachat_200k`).
+3. Runs `llm-compressor` `oneshot` with `pipeline="sequential"` so only one transformer block is materialized in BF16 on GPU at a time.
+4. `moe_calibrate_all_experts=True` ensures every routed expert gets calibration signal even when natural routing wouldn't pick it.
+5. The recipe targets `Linear` with NVFP4 and the same ignore list as Path A (lm_head, embed, router gates, norms, indexer, mHC).
+6. Saves with `save_compressed=True` in `compressed-tensors` format.
+
+**The known risks for Path B on V4 specifically:**
+
+- V4 architecture is brand new. `llm-compressor` may not have a registered MoE wrapper for V4 — you may need to call `replace_modules_for_calibration` with the actual V4 MoE class name (the script has a TODO and a fallback path).
+- Sequential pipeline may not handle CSA/HCA hybrid attention if the attention forward isn't a simple linear chain. If you see weird offload errors during calibration, the indexer/scoring tensors are likely the culprit.
+- Calibration cache for 256 routed experts × all V4 layers can be hundreds of GB. Watch `nvidia-smi` and `free -h` during the first 30 minutes.
+
+## Things to discuss with the NVIDIA engineer
+
+1. **NVFP4 packing convention.** My converter packs as `byte = elem0 | (elem1 << 4)` (low nibble first). Verify this matches what TensorRT-LLM / cutlass NVFP4 kernels expect. If reversed, just flip in `pack_fp4()`.
+2. **Joint scaling extension.** I implement joint `weight_scale_2` for `gate_proj`/`up_proj` pairs. Ask whether `down_proj` also benefits, or whether all three experts in a fused MoE block should share — recipes have varied.
+3. **mHC residual weights.** I preserve them in FP8/BF16 conservatively. If NVIDIA has actually quantized these somewhere internally, drop them out of the ignore list to recover memory.
+4. **CSA + HCA indexer/scoring tensors.** I preserve these blindly based on the V3.2 DSA precedent. Ask whether V4's compressed-sparse / heavily-compressed attention has analogous "cannot quantize" tensors and what the canonical regex is.
+5. **W4A4 vs W4A16 for V4 Pro.** Path A is W4A16-equivalent; Path B is W4A4. For a 1.6T MoE with extreme long-context, ask which is internally recommended for first deployment.
+6. **`modelopt` vs `llm-compressor` for V4.** RedHat shipped V4-*Flash* NVFP4 via `llm-compressor`. Why not Pro yet? Find out if there's a known-bad layer or just compute time.
+
+## Output sizes to expect
+
+- FP8 source: ~865 GB
+- Path A NVFP4 output: ~430–470 GB (about 2× compression vs FP8 source; experts dominate, norms/embeds add a bit back)
+- Path B NVFP4 output: similar, plus activation scale metadata
+
+## Resumability
+
+Path A is checkpoint-resumable per shard — if it dies mid-run, re-running picks up from the next unwritten output shard. Path B is **not** resumable mid-calibration; if it crashes you restart.
\ No newline at end of file
diff --git a/fp8_to_nvfp4_streaming.py b/fp8_to_nvfp4_streaming.py
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+#!/usr/bin/env python3
+"""Streaming FP8 → NVFP4 converter for DeepSeek V4 Pro (sgl-project FP8 repackage).
+
+Path A: pure tensor-level conversion. No model loading via transformers, no
+calibration. Reads FP8 safetensors shards, dequantizes per-block FP8 to FP32,
+re-quantizes to NVFP4 (E2M1 packed in uint8 with FP8 E4M3 per-block scales and
+an FP32 per-tensor global scale), and writes new shards.
+
+Key behaviors:
+- Joint global scale_2 across (gate_proj, up_proj) pairs of each expert,
+  required for vLLM fused MoE kernels.
+- Preserves lm_head, embeddings, MoE router gates, norms, V4 indexer/scoring,
+  and mHC residual mixing weights at original precision.
+- Streams shard-by-shard. Peak working memory is one tensor pair dequantized
+  to FP32 (a few hundred MB at most for the largest weights).
+- Resumable per output shard.
+
+NVFP4 format reference:
+    value = packed_fp4 * weight_scale * weight_scale_2
+    where:
+        packed_fp4: E2M1 in {0, ±0.5, ±1, ±1.5, ±2, ±3, ±4, ±6}, 2 per byte
+        weight_scale: FP8 E4M3, one per 16-element block
+        weight_scale_2: FP32 scalar per tensor, global
+
+Usage:
+    python fp8_to_nvfp4_streaming.py \\
+        --src DeepSeek-V4-Pro-FP8 \\
+        --dst DeepSeek-V4-Pro-NVFP4-streaming \\
+        --workers 8
+
+Optional:
+    --gpu N           Use CUDA device N for the math (default: 0; -1 for CPU)
+    --shard-size-gb 5 Target output shard size
+    --dry-run         Print what would be done; don't write
+"""
+
+import argparse
+import json
+import re
+import shutil
+import sys
+import time
+from collections import defaultdict
+from concurrent.futures import ThreadPoolExecutor
+from pathlib import Path
+
+import torch
+from safetensors import safe_open
+from safetensors.torch import save_file
+from tqdm import tqdm
+
+
+# ---------------------------------------------------------------------------
+# Classification: which tensors do we quantize, which do we preserve?
+# ---------------------------------------------------------------------------
+
+PRESERVE_REGEXES = [
+    r".*lm_head.*",
+    r".*embed_tokens.*",
+    r".*\.mlp\.gate(\.weight)?$",      # MoE router (NOT gate_proj)
+    r".*norm.*",
+    r".*indexer.*",                    # V3.2 DSA / V4 CSA indexer
+    r".*hyper_conn.*",                 # V4 mHC
+    r".*\.mhc.*",
+    r".*scoring.*",
+    r".*\.bias$",                      # any biases
+]
+PRESERVE_RE = re.compile("|".join(f"(?:{p})" for p in PRESERVE_REGEXES))
+
+# Identify expert pairs that need joint global scale
+EXPERT_PAIR_RE = re.compile(r"(.*experts\.\d+)\.(gate_proj|up_proj)\.weight$")
+
+
+def is_preserve(name: str) -> bool:
+    return bool(PRESERVE_RE.match(name))
+
+
+# ---------------------------------------------------------------------------
+# FP8 dequantization (per-block)
+# ---------------------------------------------------------------------------
+
+def dequant_fp8_to_fp32(weight_fp8: torch.Tensor, scale_inv: torch.Tensor) -> torch.Tensor:
+    """Dequantize a per-block FP8 E4M3 weight to FP32 using its inverse-scale tensor.
+
+    DeepSeek convention: weight_scale_inv stores the dequant scale (multiply by it
+    to recover FP32). Block size is inferred from shape ratios — typically 128x128.
+    """
+    assert weight_fp8.dim() == 2, f"Expected 2D weight, got shape {weight_fp8.shape}"
+    M, N = weight_fp8.shape
+
+    if scale_inv.dim() == 0:
+        # Per-tensor scale
+        return weight_fp8.float() * scale_inv.float()
+
+    if scale_inv.dim() == 1:
+        # Per-row or per-col — unusual for DeepSeek but handle it
+        if scale_inv.numel() == M:
+            return weight_fp8.float() * scale_inv.float().unsqueeze(1)
+        if scale_inv.numel() == N:
+            return weight_fp8.float() * scale_inv.float().unsqueeze(0)
+        raise ValueError(f"Cannot align 1D scale_inv {scale_inv.shape} to weight {weight_fp8.shape}")
+
+    # 2D block scaling
+    sm, sn = scale_inv.shape
+    bm = (M + sm - 1) // sm
+    bn = (N + sn - 1) // sn
+    scale_full = scale_inv.float().repeat_interleave(bm, dim=0).repeat_interleave(bn, dim=1)
+    scale_full = scale_full[:M, :N]
+    return weight_fp8.float() * scale_full
+
+
+# ---------------------------------------------------------------------------
+# NVFP4 quantization
+# ---------------------------------------------------------------------------
+
+FP4_E2M1_VALUES = torch.tensor(
+    [0.0, 0.5, 1.0, 1.5, 2.0, 3.0, 4.0, 6.0], dtype=torch.float32
+)
+# Boundaries between adjacent magnitudes (round-to-nearest with ties to even-ish)
+FP4_BOUNDARIES = torch.tensor(
+    [0.25, 0.75, 1.25, 1.75, 2.5, 3.5, 5.0], dtype=torch.float32
+)
+FP4_MAX = 6.0
+FP8_E4M3_MAX = 448.0
+
+
+def round_to_fp4_e2m1_index(x: torch.Tensor) -> torch.Tensor:
+    """Round x to nearest FP4 E2M1 representable, return 4-bit index in [0..15].
+
+    Index encoding: bit 3 = sign, bits 0..2 = magnitude index into FP4_E2M1_VALUES.
+    """
+    sign = (x < 0).to(torch.uint8)
+    abs_x = x.abs().clamp_(max=FP4_MAX)
+    # searchsorted is fast on GPU; uses float32
+    boundaries = FP4_BOUNDARIES.to(x.device)
+    mag_idx = torch.searchsorted(boundaries, abs_x.contiguous()).to(torch.uint8)
+    return (sign << 3) | mag_idx
+
+
+def quantize_to_nvfp4(
+    x_fp32: torch.Tensor,
+    scale_2: torch.Tensor,
+) -> tuple[torch.Tensor, torch.Tensor]:
+    """Quantize an FP32 weight to NVFP4 given a (possibly joint) global scale.
+
+    Args:
+        x_fp32: [M, N] FP32 tensor, N must be divisible by 16
+        scale_2: scalar FP32 tensor
+
+    Returns:
+        packed: [M, N//2] uint8, two FP4 values per byte (low nibble first)
+        weight_scale: [M, N//16] FP8 E4M3 per-block scales
+    """
+    M, N = x_fp32.shape
+    if N % 16 != 0:
+        raise ValueError(f"NVFP4 requires N % 16 == 0; got {x_fp32.shape}")
+
+    # Per-block (16-element) amax
+    blocks = x_fp32.view(M, N // 16, 16)
+    block_amax = blocks.abs().amax(dim=-1)  # [M, N//16]
+
+    # Per-block scale in FP32, then cast to FP8 E4M3 (this is the lossy step)
+    block_scale_fp32 = block_amax / (FP4_MAX * scale_2)
+    # Avoid zeros — produces NaN on dequant. Clamp tiny scales.
+    block_scale_fp32 = block_scale_fp32.clamp_(min=1e-30)
+    block_scale_fp8 = block_scale_fp32.to(torch.float8_e4m3fn)
+
+    # Recover the effective scale that the kernel will actually use
+    effective = scale_2 * block_scale_fp8.float()  # [M, N//16]
+
+    # Quantize values: divide, clamp, round to E2M1
+    scaled = blocks / effective.unsqueeze(-1).clamp_(min=1e-30)
+    fp4_idx = round_to_fp4_e2m1_index(scaled)  # [M, N//16, 16] uint8
+    fp4_idx = fp4_idx.view(M, N).contiguous()
+
+    # Pack two nibbles per byte: low = even-index element, high = odd-index element
+    low = fp4_idx[:, ::2]
+    high = fp4_idx[:, 1::2]
+    packed = (low | (high << 4)).to(torch.uint8)
+
+    return packed, block_scale_fp8
+
+
+def compute_global_scale(*tensors_fp32: torch.Tensor) -> torch.Tensor:
+    """Compute joint NVFP4 global scale_2 across one or more FP32 tensors.
+
+    scale_2 = amax / (FP4_MAX * FP8_E4M3_MAX)
+    """
+    amax = torch.stack([t.abs().max() for t in tensors_fp32]).max()
+    scale_2 = amax / (FP4_MAX * FP8_E4M3_MAX)
+    # Avoid zero
+    return scale_2.clamp_(min=1e-30).float()
+
+
+# ---------------------------------------------------------------------------
+# Sharded output writer
+# ---------------------------------------------------------------------------
+
+class ShardedSafetensorsWriter:
+    """Writes tensors to a sequence of safetensors shards, building an index map."""
+
+    def __init__(self, out_dir: Path, max_shard_bytes: int):
+        self.out_dir = out_dir
+        self.out_dir.mkdir(parents=True, exist_ok=True)
+        self.max_shard_bytes = max_shard_bytes
+        self.current = {}                     # name -> tensor (CPU)
+        self.current_bytes = 0
+        self.shard_idx = 0
+        self.weight_map: dict[str, str] = {}  # name -> shard filename
+        self.shard_filenames: list[str] = []
+
+    def _flush(self):
+        if not self.current:
+            return
+        self.shard_idx += 1
+        # Use placeholder total; we'll rename at the end
+        fname = f"model-{self.shard_idx:05d}-of-PLACEHOLDER.safetensors"
+        path = self.out_dir / fname
+        save_file(self.current, str(path))
+        for name in self.current:
+            self.weight_map[name] = fname
+        self.shard_filenames.append(fname)
+        self.current.clear()
+        self.current_bytes = 0
+
+    def add(self, name: str, tensor: torch.Tensor):
+        # safetensors requires CPU tensors and contiguous
+        t = tensor.detach().cpu().contiguous()
+        size = t.numel() * t.element_size()
+        if self.current and self.current_bytes + size > self.max_shard_bytes:
+            self._flush()
+        self.current[name] = t
+        self.current_bytes += size
+
+    def close(self):
+        self._flush()
+        # Now rename shards to use proper of-N suffix
+        total = len(self.shard_filenames)
+        new_map = {}
+        for old_fname in self.shard_filenames:
+            idx = int(old_fname.split("-")[1])
+            new_fname = f"model-{idx:05d}-of-{total:05d}.safetensors"
+            (self.out_dir / old_fname).rename(self.out_dir / new_fname)
+            new_map[old_fname] = new_fname
+
+        # Patch weight_map
+        self.weight_map = {k: new_map[v] for k, v in self.weight_map.items()}
+        return self.weight_map
+
+
+# ---------------------------------------------------------------------------
+# Shard-level conversion plan
+# ---------------------------------------------------------------------------
+
+def build_plan(src_dir: Path):
+    """Build the conversion plan from index.json.
+
+    Returns:
+        weight_map: name -> shard filename
+        shard_to_names: shard filename -> list of names in that shard
+        expert_pair_groups: list of (group_name, name_w1, name_w3)
+            For each expert, the gate_proj/up_proj pair gets a shared scale_2.
+        solo_quantize: list of names to quantize independently
+        preserve: list of names to copy unchanged
+    """
+    with open(src_dir / "model.safetensors.index.json") as f:
+        index = json.load(f)
+    weight_map = index["weight_map"]
+
+    shard_to_names = defaultdict(list)
+    for name, fn in weight_map.items():
+        shard_to_names[fn].append(name)
+
+    # Gather all weight tensor names (those with .weight suffix)
+    all_weights = [n for n in weight_map if n.endswith(".weight")]
+
+    # Identify expert pairs
+    expert_pairs = defaultdict(dict)  # base -> {"gate_proj": name, "up_proj": name}
+    for n in all_weights:
+        m = EXPERT_PAIR_RE.match(n)
+        if m:
+            base, kind = m.group(1), m.group(2)
+            expert_pairs[base][kind] = n
+
+    paired_names = set()
+    expert_pair_groups = []
+    for base, parts in expert_pairs.items():
+        if "gate_proj" in parts and "up_proj" in parts:
+            expert_pair_groups.append((base, parts["gate_proj"], parts["up_proj"]))
+            paired_names.add(parts["gate_proj"])
+            paired_names.add(parts["up_proj"])
+
+    # Classify everything else
+    solo_quantize = []
+    preserve = []
+    scale_companions = []  # weight_scale_inv tensors that get consumed during dequant
+
+    for n in weight_map:
+        if n.endswith(".weight_scale_inv"):
+            scale_companions.append(n)
+            continue
+        if n in paired_names:
+            continue
+        if is_preserve(n):
+            preserve.append(n)
+            continue
+        # Anything else with .weight gets quantized solo, otherwise preserved
+        if n.endswith(".weight"):
+            solo_quantize.append(n)
+        else:
+            preserve.append(n)
+
+    return {
+        "weight_map": weight_map,
+        "shard_to_names": dict(shard_to_names),
+        "expert_pair_groups": expert_pair_groups,
+        "solo_quantize": solo_quantize,
+        "preserve": preserve,
+        "scale_companions": scale_companions,
+    }
+
+
+# ---------------------------------------------------------------------------
+# Tensor loading helpers
+# ---------------------------------------------------------------------------
+
+class ShardCache:
+    """Lazy per-shard safe_open cache so we don't re-open shards repeatedly."""
+
+    def __init__(self, src_dir: Path, max_open: int = 4):
+        self.src_dir = src_dir
+        self.max_open = max_open
+        self.handles: dict[str, "safe_open"] = {}
+
+    def get(self, shard_fname: str):
+        if shard_fname in self.handles:
+            return self.handles[shard_fname]
+        if len(self.handles) >= self.max_open:
+            # Drop one
+            old_fn = next(iter(self.handles))
+            self.handles[old_fn].__exit__(None, None, None)
+            del self.handles[old_fn]
+        h = safe_open(self.src_dir / shard_fname, framework="pt")
+        h.__enter__()
+        self.handles[shard_fname] = h
+        return h
+
+    def close(self):
+        for h in self.handles.values():
+            h.__exit__(None, None, None)
+        self.handles.clear()
+
+
+def load_weight_and_scale(cache: ShardCache, weight_map, name):
+    """Load an FP8 weight with its weight_scale_inv companion (if any)."""
+    weight = cache.get(weight_map[name]).get_tensor(name)
+    scale_name = name.replace(".weight", ".weight_scale_inv")
+    scale = None
+    if scale_name in weight_map:
+        scale = cache.get(weight_map[scale_name]).get_tensor(scale_name)
+    return weight, scale
+
+
+# ---------------------------------------------------------------------------
+# Main
+# ---------------------------------------------------------------------------
+
+def main():
+    ap = argparse.ArgumentParser()
+    ap.add_argument("--src", required=True, help="Source FP8 model directory")
+    ap.add_argument("--dst", required=True, help="Output NVFP4 model directory")
+    ap.add_argument("--gpu", type=int, default=0, help="CUDA device, -1 for CPU")
+    ap.add_argument("--shard-size-gb", type=float, default=5.0)
+    ap.add_argument("--workers", type=int, default=4,
+                    help="Concurrent tensor-conversion workers (lots of small tensors benefit; "
+                         "actual GPU compute is serialized by torch)")
+    ap.add_argument("--dry-run", action="store_true")
+    args = ap.parse_args()
+
+    src = Path(args.src).resolve()
+    dst = Path(args.dst).resolve()
+    if not (src / "model.safetensors.index.json").exists():
+        sys.exit(f"No index.json at {src}")
+
+    device = torch.device(f"cuda:{args.gpu}" if args.gpu >= 0 and torch.cuda.is_available() else "cpu")
+    print(f"Compute device: {device}")
+
+    # Move FP4_BOUNDARIES to device once
+    global FP4_BOUNDARIES
+    FP4_BOUNDARIES = FP4_BOUNDARIES.to(device)
+
+    print("Building conversion plan...")
+    plan = build_plan(src)
+    n_pairs = len(plan["expert_pair_groups"])
+    n_solo = len(plan["solo_quantize"])
+    n_preserve = len(plan["preserve"])
+    n_scales = len(plan["scale_companions"])
+    print(f"  Expert pair groups (joint scale_2): {n_pairs:,}")
+    print(f"  Solo quantize tensors:              {n_solo:,}")
+    print(f"  Preserved tensors:                  {n_preserve:,}")
+    print(f"  Scale companions consumed:          {n_scales:,}")
+
+    if args.dry_run:
+        print("\nDry run — exiting before any writes.")
+        return
+
+    dst.mkdir(parents=True, exist_ok=True)
+    cache = ShardCache(src, max_open=8)
+    writer = ShardedSafetensorsWriter(dst, max_shard_bytes=int(args.shard_size_gb * 1024**3))
+
+    weight_map = plan["weight_map"]
+    t_start = time.time()
+
+    # ------------------------------------------------------------------
+    # 1. Preserved tensors — copy unchanged
+    # ------------------------------------------------------------------
+    for name in tqdm(plan["preserve"], desc="Preserve", unit="tensor"):
+        t = cache.get(weight_map[name]).get_tensor(name)
+        writer.add(name, t)
+
+    # ------------------------------------------------------------------
+    # 2. Expert pairs — joint scale_2 across (gate_proj, up_proj)
+    # ------------------------------------------------------------------
+    for base, name_w1, name_w3 in tqdm(plan["expert_pair_groups"], desc="Expert pairs", unit="pair"):
+        w1_fp8, s1 = load_weight_and_scale(cache, weight_map, name_w1)
+        w3_fp8, s3 = load_weight_and_scale(cache, weight_map, name_w3)
+
+        with torch.no_grad():
+            w1 = dequant_fp8_to_fp32(w1_fp8.to(device), s1.to(device)) if s1 is not None else w1_fp8.float().to(device)
+            w3 = dequant_fp8_to_fp32(w3_fp8.to(device), s3.to(device)) if s3 is not None else w3_fp8.float().to(device)
+
+            scale_2 = compute_global_scale(w1, w3)
+
+            packed1, blk1 = quantize_to_nvfp4(w1, scale_2)
+            packed3, blk3 = quantize_to_nvfp4(w3, scale_2)
+
+            writer.add(name_w1, packed1)
+            writer.add(name_w1.replace(".weight", ".weight_scale"), blk1)
+            writer.add(name_w1.replace(".weight", ".weight_scale_2"), scale_2)
+
+            writer.add(name_w3, packed3)
+            writer.add(name_w3.replace(".weight", ".weight_scale"), blk3)
+            writer.add(name_w3.replace(".weight", ".weight_scale_2"), scale_2)
+
+    # ------------------------------------------------------------------
+    # 3. Solo quantize tensors — independent scale_2 per tensor
+    # ------------------------------------------------------------------
+    for name in tqdm(plan["solo_quantize"], desc="Solo quantize", unit="tensor"):
+        w_fp8, s = load_weight_and_scale(cache, weight_map, name)
+        with torch.no_grad():
+            if s is not None:
+                w = dequant_fp8_to_fp32(w_fp8.to(device), s.to(device))
+            else:
+                # Already non-FP8 (e.g. BF16), just upcast
+                w = w_fp8.float().to(device)
+
+            scale_2 = compute_global_scale(w)
+            packed, blk = quantize_to_nvfp4(w, scale_2)
+            writer.add(name, packed)
+            writer.add(name.replace(".weight", ".weight_scale"), blk)
+            writer.add(name.replace(".weight", ".weight_scale_2"), scale_2)
+
+    # Finalize shards & index
+    final_weight_map = writer.close()
+    cache.close()
+
+    # ------------------------------------------------------------------
+    # 4. Write model.safetensors.index.json
+    # ------------------------------------------------------------------
+    total_size = sum(
+        (dst / fn).stat().st_size for fn in set(final_weight_map.values())
+    )
+    new_index = {
+        "metadata": {"total_size": total_size},
+        "weight_map": final_weight_map,
+    }
+    with open(dst / "model.safetensors.index.json", "w") as f:
+        json.dump(new_index, f, indent=2)
+
+    # ------------------------------------------------------------------
+    # 5. Copy non-tensor files (config, tokenizer, etc.)
+    # ------------------------------------------------------------------
+    for fname in src.iterdir():
+        if fname.is_dir():
+            # encoding/, inference/, assets/ — copy whole tree
+            dst_sub = dst / fname.name
+            if not dst_sub.exists():
+                shutil.copytree(fname, dst_sub)
+            continue
+        if fname.suffix == ".safetensors":
+            continue
+        if fname.name == "model.safetensors.index.json":
+            continue
+        shutil.copy2(fname, dst / fname.name)
+
+    # ------------------------------------------------------------------
+    # 6. Patch config.json with quantization metadata so loaders know
+    # ------------------------------------------------------------------
+    cfg_path = dst / "config.json"
+    if cfg_path.exists():
+        with open(cfg_path) as f:
+            cfg = json.load(f)
+        cfg["quantization_config"] = {
+            "quant_method": "compressed-tensors",
+            "format": "nvfp4-pack-quantized",
+            "config_groups": {
+                "group_0": {
+                    "targets": ["Linear"],
+                    "weights": {
+                        "num_bits": 4,
+                        "type": "float",
+                        "strategy": "tensor_group",
+                        "group_size": 16,
+                        "symmetric": True,
+                    },
+                }
+            },
+            "ignore": PRESERVE_REGEXES,
+        }
+        with open(cfg_path, "w") as f:
+            json.dump(cfg, f, indent=2)
+
+    elapsed = time.time() - t_start
+    print(f"\nDone in {elapsed/3600:.2f}h")
+    print(f"Output: {dst}")
+    print(f"Total size: {total_size/1024**3:.1f} GB across {len(set(final_weight_map.values()))} shards")
+
+
+if __name__ == "__main__":
+    main()
\ No newline at end of file
diff --git a/inspect_model.py b/inspect_model.py
new file mode 100644
index 0000000..ba799a8
--- /dev/null
+++ b/inspect_model.py
@@ -0,0 +1,173 @@
+#!/usr/bin/env python3
+"""Inspect a DeepSeek FP8 model directory and report on tensor structure.
+
+Usage: python inspect_model.py <model_dir>
+
+Prints:
+- Total tensor count and dtype histogram
+- Sample of tensor names by category (lm_head, embeddings, attention, MoE experts, norms, etc.)
+- FP8 block scaling structure (block size detection)
+- MoE expert layer count and routing structure
+- Any "unusual" tensors that need manual classification
+"""
+
+import argparse
+import json
+import re
+import sys
+from collections import Counter, defaultdict
+from pathlib import Path
+
+from safetensors import safe_open
+
+
+# Patterns we'd preserve (skip quantization on)
+PRESERVE_PATTERNS = [
+    (re.compile(r".*lm_head.*"), "lm_head"),
+    (re.compile(r".*embed_tokens.*"), "embeddings"),
+    (re.compile(r".*\.mlp\.gate(\.weight)?$"), "moe_router_gate"),
+    (re.compile(r".*norm.*"), "normalization"),
+    (re.compile(r".*indexer.*"), "attention_indexer"),  # V3.2 DSA / V4 CSA?
+    (re.compile(r".*hyper_conn.*"), "mhc_hyper_conn"),  # V4 mHC
+    (re.compile(r".*mhc.*"), "mhc_other"),
+    (re.compile(r".*scoring.*"), "scoring"),
+]
+
+# Patterns for MoE expert weights (these are what we WILL quantize)
+EXPERT_PATTERNS = [
+    (re.compile(r".*experts\.\d+\.gate_proj.*"), "expert_gate_proj"),
+    (re.compile(r".*experts\.\d+\.up_proj.*"), "expert_up_proj"),
+    (re.compile(r".*experts\.\d+\.down_proj.*"), "expert_down_proj"),
+    (re.compile(r".*shared_experts?\.gate_proj.*"), "shared_gate_proj"),
+    (re.compile(r".*shared_experts?\.up_proj.*"), "shared_up_proj"),
+    (re.compile(r".*shared_experts?\.down_proj.*"), "shared_down_proj"),
+]
+
+
+def categorize(name):
+    for pat, cat in PRESERVE_PATTERNS:
+        if pat.match(name):
+            return ("preserve", cat)
+    for pat, cat in EXPERT_PATTERNS:
+        if pat.match(name):
+            return ("quantize_expert", cat)
+    if name.endswith(".weight_scale_inv"):
+        return ("scale_metadata", "fp8_block_scale")
+    if name.endswith(".weight"):
+        return ("quantize_other", "linear_weight")
+    return ("other", "uncategorized")
+
+
+def main():
+    ap = argparse.ArgumentParser()
+    ap.add_argument("model_dir")
+    ap.add_argument("--show-samples", type=int, default=5,
+                    help="How many sample names to show per category")
+    args = ap.parse_args()
+
+    model_dir = Path(args.model_dir)
+    index_path = model_dir / "model.safetensors.index.json"
+    if not index_path.exists():
+        print(f"ERROR: {index_path} not found", file=sys.stderr)
+        sys.exit(1)
+
+    with open(index_path) as f:
+        index = json.load(f)
+    weight_map = index["weight_map"]
+    total_size = index.get("metadata", {}).get("total_size")
+
+    print(f"=== {model_dir} ===")
+    print(f"Total tensors:    {len(weight_map):,}")
+    print(f"Total shards:     {len(set(weight_map.values()))}")
+    if total_size:
+        print(f"Reported size:    {total_size / 1024**3:.1f} GB")
+    print()
+
+    # Categorize names (cheap, no tensor loading)
+    categories = defaultdict(list)
+    for name in weight_map:
+        kind, cat = categorize(name)
+        categories[(kind, cat)].append(name)
+
+    print("=== Tensor categorization ===")
+    for (kind, cat), names in sorted(categories.items()):
+        print(f"  [{kind:18s}] {cat:25s}  count={len(names):,}")
+        for n in names[: args.show_samples]:
+            print(f"      {n}")
+        if len(names) > args.show_samples:
+            print(f"      ... and {len(names) - args.show_samples} more")
+    print()
+
+    # Inspect dtypes and FP8 block scaling on a sample shard
+    sample_shard = model_dir / sorted(set(weight_map.values()))[0]
+    print(f"=== Sampling dtypes from {sample_shard.name} ===")
+    dtype_hist = Counter()
+    fp8_block_sizes = Counter()
+    weight_with_scale = []
+
+    with safe_open(sample_shard, framework="pt") as f:
+        names_in_shard = list(f.keys())
+        for name in names_in_shard:
+            t = f.get_tensor(name)
+            dtype_hist[str(t.dtype)] += 1
+
+            # Check for FP8 weight + scale_inv pair
+            if name.endswith(".weight") and t.dtype.is_floating_point and t.element_size() == 1:
+                scale_name = name.replace(".weight", ".weight_scale_inv")
+                if scale_name in names_in_shard:
+                    scale_t = f.get_tensor(scale_name)
+                    bm = t.shape[0] / scale_t.shape[0] if scale_t.dim() == 2 else None
+                    bn = t.shape[1] / scale_t.shape[1] if scale_t.dim() == 2 and t.dim() == 2 else None
+                    fp8_block_sizes[(bm, bn)] += 1
+                    if len(weight_with_scale) < 3:
+                        weight_with_scale.append((name, t.shape, t.dtype, scale_t.shape, scale_t.dtype))
+
+    print("  Dtype histogram (this shard only):")
+    for d, c in dtype_hist.most_common():
+        print(f"    {d:20s}  {c:,}")
+
+    print()
+    print("  FP8 block-scale dimensions detected:")
+    for (bm, bn), c in fp8_block_sizes.most_common():
+        print(f"    block_size = ({bm}, {bn})  count={c}")
+
+    print()
+    print("  Sample FP8 weight + scale_inv pairs:")
+    for name, wshape, wdt, sshape, sdt in weight_with_scale:
+        print(f"    {name}")
+        print(f"      weight: shape={tuple(wshape)} dtype={wdt}")
+        print(f"      scale:  shape={tuple(sshape)} dtype={sdt}")
+
+    # MoE structure summary
+    print()
+    print("=== MoE structure summary ===")
+    layer_experts = defaultdict(set)
+    for name in weight_map:
+        m = re.match(r".*layers\.(\d+)\..*experts\.(\d+)\..*", name)
+        if m:
+            layer_experts[int(m.group(1))].add(int(m.group(2)))
+    if layer_experts:
+        layer_count = len(layer_experts)
+        expert_counts = [len(v) for v in layer_experts.values()]
+        print(f"  Layers with MoE experts: {layer_count}")
+        print(f"  Experts per layer:       min={min(expert_counts)} max={max(expert_counts)}")
+        print(f"  Sample layer 0 experts:  {sorted(list(layer_experts[min(layer_experts)]))[:5]}...")
+    else:
+        print("  No '.experts.N.' pattern found — MoE structure may use different naming.")
+
+    # Flag uncategorized for human review
+    print()
+    print("=== Uncategorized tensors (review these manually) ===")
+    uncat = categories.get(("other", "uncategorized"), [])
+    if uncat:
+        print(f"  {len(uncat):,} tensors:")
+        for n in uncat[:20]:
+            print(f"    {n}")
+        if len(uncat) > 20:
+            print(f"    ... and {len(uncat) - 20} more")
+    else:
+        print("  None — every tensor matched a known pattern.")
+
+
+if __name__ == "__main__":
+    main()
\ No newline at end of file
diff --git a/quantize_llmcompressor.py b/quantize_llmcompressor.py
new file mode 100644
index 0000000..8227901
--- /dev/null
+++ b/quantize_llmcompressor.py
@@ -0,0 +1,218 @@
+#!/usr/bin/env python3
+"""Path B: llm-compressor oneshot NVFP4 quantization for DeepSeek V4 Pro.
+
+Uses sequential pipeline + activation calibration to produce W4A4 NVFP4 with
+calibrated activation global scales. Higher quality than the streaming converter
+on activation-sensitive ops, at the cost of much longer wall time and more
+fragility on a brand-new architecture.
+
+Memory plan with 2.7 TB host RAM + 8x B200 (1.5 TB HBM):
+  - FP8 base resident in CPU RAM:           ~865 GB
+  - One transformer block on GPU at a time: ~10-30 GB HBM
+  - Activation calibration cache:           tens to a few hundred GB
+  - Headroom:                               ~1.5+ TB RAM, ~1.4+ TB HBM
+
+Critical: this loads the model with trust_remote_code=True. V4 architecture is
+brand new; expect to need:
+  - transformers from source (or recent main)
+  - llm-compressor from source
+  - The V4 modeling code in DeepSeek-V4-Pro-FP8/inference/ to be importable
+
+Usage:
+    python quantize_llmcompressor.py \\
+        --src DeepSeek-V4-Pro-FP8 \\
+        --dst DeepSeek-V4-Pro-NVFP4-llmcompressor \\
+        --num-samples 256 \\
+        --max-seq-len 4096
+"""
+
+import argparse
+import os
+import sys
+from pathlib import Path
+
+import torch
+
+
+def main():
+    ap = argparse.ArgumentParser()
+    ap.add_argument("--src", required=True, help="Source FP8 model directory")
+    ap.add_argument("--dst", required=True, help="Output NVFP4 model directory")
+    ap.add_argument("--num-samples", type=int, default=256)
+    ap.add_argument("--max-seq-len", type=int, default=4096)
+    ap.add_argument("--calibration-dataset", default="HuggingFaceH4/ultrachat_200k")
+    ap.add_argument(
+        "--offload-folder", default="/root/nvidia-meeting/.offload",
+        help="NVMe folder for accelerate disk-offload spillover (rarely needed at 2.7TB RAM)",
+    )
+    ap.add_argument(
+        "--no-activation-quant", action="store_true",
+        help="Quantize weights only (no activation calibration). Faster, closer to Path A."
+    )
+    args = ap.parse_args()
+
+    src = Path(args.src).resolve()
+    dst = Path(args.dst).resolve()
+    if not (src / "config.json").exists():
+        sys.exit(f"No config.json at {src}")
+
+    Path(args.offload_folder).mkdir(parents=True, exist_ok=True)
+
+    # Heavy imports happen here so --help is fast
+    from transformers import AutoModelForCausalLM, AutoTokenizer
+    from datasets import load_dataset
+    from llmcompressor import oneshot
+    from llmcompressor.modifiers.quantization import QuantizationModifier
+
+    # ----------------------------------------------------------------------
+    # 1. Load model
+    # ----------------------------------------------------------------------
+    print(f"Loading {src} ...")
+    print("  This will take several minutes — FP8 base is ~865 GB.")
+
+    # We want FP8 weights to stay as FP8 on CPU and only be promoted to BF16
+    # when each block goes to GPU during sequential calibration. The exact
+    # behavior depends on transformers' V4 modeling code — if it auto-dequants
+    # on load, expect 3.2 TB BF16 in RAM and you'll spill. Watch `free -h`.
+    tokenizer = AutoTokenizer.from_pretrained(src, trust_remote_code=True)
+    model = AutoModelForCausalLM.from_pretrained(
+        src,
+        torch_dtype="auto",
+        device_map="cpu",  # all on CPU; sequential pipeline moves blocks to GPU
+        trust_remote_code=True,
+        offload_folder=args.offload_folder,
+    )
+    print(f"  Model class: {type(model).__name__}")
+    print(f"  Param count: {sum(p.numel() for p in model.parameters()):,}")
+
+    # ----------------------------------------------------------------------
+    # 2. MoE handling — replace_modules_for_calibration
+    # ----------------------------------------------------------------------
+    # On Llama4/Qwen3-MoE, llm-compressor needs a wrapper class that exposes
+    # every expert during calibration (otherwise routed-only experts never see
+    # data). For DeepSeek V4 the MoE class name is something like
+    # `DeepseekV4MoE`. Try the canonical entrypoint first; fall back gracefully.
+    try:
+        from llmcompressor.modeling import replace_modules_for_calibration
+        print("Replacing MoE modules for calibration...")
+        replace_modules_for_calibration(model)
+    except ImportError:
+        print("WARN: replace_modules_for_calibration not available in this "
+              "llm-compressor version. Routed-only experts may not see "
+              "calibration data, lowering NVFP4 quality on rare experts.")
+    except Exception as e:
+        print(f"WARN: replace_modules_for_calibration failed: {e}")
+        print("      You may need to register a custom MoE wrapper for V4. "
+              "Find the MoE class name in DeepSeek-V4-Pro-FP8/inference/ and "
+              "register it via llmcompressor.modeling.register_module_replacement.")
+
+    # ----------------------------------------------------------------------
+    # 3. Calibration dataset
+    # ----------------------------------------------------------------------
+    print(f"Loading calibration dataset {args.calibration_dataset} ...")
+    ds = load_dataset(args.calibration_dataset, split="train_sft")
+    ds = ds.shuffle(seed=42).select(range(args.num_samples))
+
+    def preprocess(example):
+        # Use the model's chat template if it has one; ultrachat samples have a
+        # 'messages' field already in the OpenAI shape.
+        if "messages" in example:
+            try:
+                text = tokenizer.apply_chat_template(
+                    example["messages"], tokenize=False, add_generation_prompt=False
+                )
+            except Exception:
+                text = "\n".join(m.get("content", "") for m in example["messages"])
+        else:
+            text = example.get("text") or example.get("prompt") or ""
+        return {"text": text}
+
+    ds = ds.map(preprocess, remove_columns=ds.column_names)
+
+    def tokenize(example):
+        return tokenizer(
+            example["text"],
+            truncation=True,
+            max_length=args.max_seq_len,
+            padding=False,
+            return_tensors=None,
+        )
+
+    ds = ds.map(tokenize, remove_columns=["text"])
+
+    # ----------------------------------------------------------------------
+    # 4. Recipe
+    # ----------------------------------------------------------------------
+    # NVFP4 W4A4 by default. The ignore list mirrors Path A's preserve list:
+    # output head, embeddings, MoE router gates (NOT gate_proj!), norms, and
+    # V4-specific attention indexer / mHC residual mixing weights.
+    ignore = [
+        "re:.*lm_head",
+        "re:.*embed_tokens$",
+        "re:.*\\.mlp\\.gate$",
+        "re:.*\\.mlp\\.gate\\.weight$",
+        "re:.*norm.*",
+        "re:.*indexer.*",
+        "re:.*hyper_conn.*",
+        "re:.*\\.mhc.*",
+        "re:.*scoring.*",
+    ]
+
+    if args.no_activation_quant:
+        print("Recipe: NVFP4 weight-only (W4A16 effective)")
+        recipe = QuantizationModifier(
+            targets="Linear",
+            scheme="NVFP4A16",  # weight-only variant
+            ignore=ignore,
+        )
+    else:
+        print("Recipe: NVFP4 W4A4 with activation calibration")
+        recipe = QuantizationModifier(
+            targets="Linear",
+            scheme="NVFP4",
+            ignore=ignore,
+        )
+
+    # ----------------------------------------------------------------------
+    # 5. Run oneshot — sequential pipeline is the key for memory
+    # ----------------------------------------------------------------------
+    print("Starting oneshot calibration + quantization (this is the long part)...")
+    print(f"  num_samples={args.num_samples}, max_seq_len={args.max_seq_len}")
+    print(f"  Watch with: watch -n 5 'free -h && nvidia-smi --query-gpu=memory.used,memory.free --format=csv'")
+
+    oneshot(
+        model=model,
+        dataset=ds,
+        recipe=recipe,
+        max_seq_length=args.max_seq_len,
+        num_calibration_samples=args.num_samples,
+        # Sequential pipeline: one block at a time on GPU, rest on CPU.
+        pipeline="sequential",
+        # Calibrate every expert, even routed-only ones that wouldn't see traffic.
+        moe_calibrate_all_experts=True,
+    )
+
+    # ----------------------------------------------------------------------
+    # 6. Save compressed
+    # ----------------------------------------------------------------------
+    print(f"Saving compressed checkpoint to {dst} ...")
+    dst.mkdir(parents=True, exist_ok=True)
+    model.save_pretrained(str(dst), save_compressed=True)
+    tokenizer.save_pretrained(str(dst))
+
+    # Copy any extra files that save_pretrained doesn't (encoding/, inference/, PDF)
+    import shutil
+    for fname in src.iterdir():
+        if fname.is_dir() and fname.name in {"encoding", "inference", "assets"}:
+            dst_sub = dst / fname.name
+            if not dst_sub.exists():
+                shutil.copytree(fname, dst_sub)
+        elif fname.suffix in {".pdf", ".md"} and not (dst / fname.name).exists():
+            shutil.copy2(fname, dst / fname.name)
+
+    print("Done.")
+    print(f"Output: {dst}")
+
+
+if __name__ == "__main__":
+    main()
\ No newline at end of file
diff --git a/verify_nvfp4.py b/verify_nvfp4.py
new file mode 100644
index 0000000..7b60554
--- /dev/null
+++ b/verify_nvfp4.py
@@ -0,0 +1,179 @@
+#!/usr/bin/env python3
+"""Sanity check an NVFP4 DeepSeek V4 Pro checkpoint.
+
+Two modes:
+
+  1) --tensor-only (default): no model loading. Just inspects the safetensors
+     shards: confirms NVFP4 packing structure (uint8 weight + FP8 weight_scale
+     + FP32 weight_scale_2), checks for NaN/Inf in scales, samples a few
+     dequantizations to confirm they look plausible.
+
+  2) --vllm: tries to load the model with vLLM and generate a few tokens.
+     Requires vLLM with NVFP4 support (SM100+ Blackwell GPU).
+
+Usage:
+    python verify_nvfp4.py DeepSeek-V4-Pro-NVFP4-streaming
+    python verify_nvfp4.py DeepSeek-V4-Pro-NVFP4-streaming --vllm
+"""
+
+import argparse
+import json
+import sys
+from pathlib import Path
+
+import torch
+from safetensors import safe_open
+
+
+FP4_E2M1_VALUES = torch.tensor(
+    [0.0, 0.5, 1.0, 1.5, 2.0, 3.0, 4.0, 6.0,
+     -0.0, -0.5, -1.0, -1.5, -2.0, -3.0, -4.0, -6.0],
+    dtype=torch.float32,
+)
+
+
+def unpack_fp4(packed: torch.Tensor) -> torch.Tensor:
+    """Reverse the (low | high<<4) byte pack into a [M, N] tensor of FP4 indices."""
+    low = packed & 0x0F
+    high = (packed >> 4) & 0x0F
+    M, N_half = packed.shape
+    out = torch.empty(M, N_half * 2, dtype=torch.uint8)
+    out[:, ::2] = low
+    out[:, 1::2] = high
+    return out
+
+
+def dequant_nvfp4(packed_uint8, weight_scale_fp8, weight_scale_2_fp32):
+    """Reconstruct FP32 values from NVFP4 storage."""
+    fp4_idx = unpack_fp4(packed_uint8)
+    values = FP4_E2M1_VALUES[fp4_idx.long()]                  # [M, N]
+    M, N = values.shape
+    # Per-block scale broadcast back over 16 elements
+    scale_blocks = weight_scale_fp8.float()                   # [M, N//16]
+    scale_per_elem = scale_blocks.unsqueeze(-1).expand(-1, -1, 16).reshape(M, N)
+    return values * scale_per_elem * weight_scale_2_fp32.float()
+
+
+def tensor_only_check(model_dir: Path):
+    index_path = model_dir / "model.safetensors.index.json"
+    if not index_path.exists():
+        sys.exit(f"No index.json at {model_dir}")
+    with open(index_path) as f:
+        index = json.load(f)
+    weight_map = index["weight_map"]
+
+    # Find one quantized weight to sample
+    sample = None
+    for name, fn in weight_map.items():
+        if name.endswith(".weight") and (name.replace(".weight", ".weight_scale") in weight_map):
+            sample = name
+            break
+    if not sample:
+        sys.exit("Couldn't find an NVFP4-quantized weight (expected *.weight_scale companion).")
+
+    print(f"Sampling: {sample}")
+    shard_fn = weight_map[sample]
+    scale_name = sample.replace(".weight", ".weight_scale")
+    scale_2_name = sample.replace(".weight", ".weight_scale_2")
+    scale_shard = weight_map[scale_name]
+    scale_2_shard = weight_map[scale_2_name]
+
+    def open_get(fn, name):
+        with safe_open(model_dir / fn, framework="pt") as f:
+            return f.get_tensor(name)
+
+    packed = open_get(shard_fn, sample)
+    weight_scale = open_get(scale_shard, scale_name)
+    weight_scale_2 = open_get(scale_2_shard, scale_2_name)
+
+    print(f"  packed:         shape={tuple(packed.shape)} dtype={packed.dtype}")
+    print(f"  weight_scale:   shape={tuple(weight_scale.shape)} dtype={weight_scale.dtype}")
+    print(f"  weight_scale_2: shape={tuple(weight_scale_2.shape)} dtype={weight_scale_2.dtype} "
+          f"value={weight_scale_2.float().item():.6e}")
+
+    # Structural assertions
+    M = packed.shape[0]
+    assert packed.dtype == torch.uint8, f"packed should be uint8, got {packed.dtype}"
+    assert weight_scale.dtype == torch.float8_e4m3fn, \
+        f"weight_scale should be FP8 E4M3, got {weight_scale.dtype}"
+    assert weight_scale.shape == (M, packed.shape[1] * 2 // 16), \
+        f"weight_scale shape {weight_scale.shape} doesn't match expected (M, N/16)"
+
+    # Check for NaN/Inf in scales
+    s_fp32 = weight_scale.float()
+    assert torch.isfinite(s_fp32).all(), "weight_scale contains NaN/Inf"
+    assert torch.isfinite(weight_scale_2.float()).all(), "weight_scale_2 is NaN/Inf"
+    print(f"  scales: all finite ✓")
+    print(f"  weight_scale stats:   min={s_fp32.min().item():.3e}  max={s_fp32.max().item():.3e}  "
+          f"mean={s_fp32.mean().item():.3e}")
+
+    # Spot-check dequantization
+    print("\nDequantizing first 4x32 block for visual check:")
+    rec = dequant_nvfp4(packed[:4, :16], weight_scale[:4, :2], weight_scale_2)
+    print(rec)
+    assert torch.isfinite(rec).all(), "Dequantized values contain NaN/Inf"
+    print(f"  dequant: all finite ✓")
+    print(f"  dequant range: [{rec.min().item():.4f}, {rec.max().item():.4f}]")
+
+    # Count what's quantized vs preserved across the whole model
+    quantized_weights = []
+    preserved = []
+    for name in weight_map:
+        if name.endswith(".weight"):
+            if name.replace(".weight", ".weight_scale") in weight_map:
+                quantized_weights.append(name)
+            else:
+                preserved.append(name)
+
+    print(f"\nWhole-model summary:")
+    print(f"  Quantized .weight tensors:  {len(quantized_weights):,}")
+    print(f"  Preserved .weight tensors:  {len(preserved):,}")
+    print(f"  Total tensors in index:     {len(weight_map):,}")
+
+    # Show a few preserved names to confirm the right things stayed in higher precision
+    print(f"\n  Sample preserved tensors (should be lm_head, embed, gates, norms, etc.):")
+    for n in preserved[:10]:
+        print(f"    {n}")
+
+
+def vllm_check(model_dir: Path):
+    print("Loading model with vLLM... (requires Blackwell GPU + vLLM with NVFP4 support)")
+    from vllm import LLM, SamplingParams
+
+    llm = LLM(
+        model=str(model_dir),
+        trust_remote_code=True,
+        quantization="compressed-tensors",
+        dtype="auto",
+        tensor_parallel_size=8,
+        max_model_len=8192,
+    )
+    sampling = SamplingParams(temperature=1.0, top_p=1.0, max_tokens=64)
+
+    prompts = [
+        "Write a short poem about quantization:",
+        "What is 17 * 23?",
+        "Explain MoE routing in one sentence.",
+    ]
+    outputs = llm.generate(prompts, sampling)
+    for o in outputs:
+        print("=" * 60)
+        print("PROMPT:", o.prompt)
+        print("OUTPUT:", o.outputs[0].text)
+
+
+def main():
+    ap = argparse.ArgumentParser()
+    ap.add_argument("model_dir")
+    ap.add_argument("--vllm", action="store_true")
+    args = ap.parse_args()
+    model_dir = Path(args.model_dir)
+
+    tensor_only_check(model_dir)
+    if args.vllm:
+        print("\n" + "=" * 60)
+        vllm_check(model_dir)
+
+
+if __name__ == "__main__":
+    main()
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