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feat(export): add functional quantized weight export - #2251

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@mxinO mxinO commented Aug 26, 2026 •

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Summary

Adds a non-mutating per-weight export API for online real-quant refit.

  • Resolves exact named and numbered weight quantizers, including grouped-linear experts.
  • Captures current quantizer state without mutating the trainable module.
  • Applies topology-aligned merge and select operations to opaque state.
  • Packs a caller-provided logical Hugging Face weight and emits format-owned sidecars.
  • Builds canonical quantization_config metadata from caller-provided Hugging Face weight names.
  • Keeps reusable export specs metadata-only; mutable amax and scale tensors are recaptured for each stream.
  • Preserves calibrated per-expert state when grouped quantizers are restored.

The API covers non-integer FP8, MXFP8, MXFP4, NVFP4 variants, and mixed per-layer configurations. Ordinary offline export stays on its existing path. AWQ, SmoothQuant, SVDQuant, and integer weight formats are outside this PR.

Usage

spec = get_quantized_weight_export_spec(module, "weight")
state = capture_quantized_weight_export_state(module, "weight")
exported = export_quantized_weight_tensors(weight, state, dtype)
config = build_hf_quantization_config({"model.layers.0.mlp.weight": spec})

Validation

  • Focused CPU functional-export tests passed.
  • Grouped-quantizer GPU restore regression passed.
  • 182 focused CPU/GPU export cases passed after test consolidation, including eight CUDA format-parity cases.
  • 197 focused Megatron-Bridge conversion/export tests passed in earlier cross-repository validation.
  • 32 existing offline-export tests passed across Transformers, Diffusers, streaming/offload, and AWQ fallback coverage.
  • ModelOpt pre-commit hooks passed.
  • Downstream dense W4A16 and grouped-MoE W4A4 native-refit jobs completed repeated refits with finite loss and KL.

Dependency

Megatron-Bridge integration: NVIDIA-NeMo/Megatron-Bridge#5812

Checklist

  • Added focused regression tests.
  • Preserved ordinary offline-export behavior.
  • No new dependency.
  • Changelog update, if required before review.

Summary by CodeRabbit

  • New Features
    • Added quantized weight export for NVFP4, MXFP4, W4A16 MXFP4, FP8, and MXFP8 formats, with associated scales and Hugging Face quantization configurations.
    • Added support for additional quantization formats and group settings when converting Hugging Face quantization configurations.
    • Export data can be split, restored, merged, and selected for sharded weight workflows.
  • Bug Fixes
    • Mixed-format exports now identify unquantized layers in their configuration.
    • Restoring grouped quantized layers preserves calibrated expert weight scales.

mxinO added 8 commits August 15, 2026 07:44
Signed-off-by: Meng Xin <mxin@nvidia.com>
Signed-off-by: Meng Xin <mxin@nvidia.com>
Signed-off-by: Meng Xin <mxin@nvidia.com>
Signed-off-by: Meng Xin <mxin@nvidia.com>
Signed-off-by: Meng Xin <mxin@nvidia.com>
Signed-off-by: Meng Xin <mxin@nvidia.com>
Signed-off-by: Meng Xin <mxin@nvidia.com>
…nt-refit

Signed-off-by: Meng Xin <mxin@nvidia.com>
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📝 Walkthrough

Walkthrough

The export package adds quantized-weight state capture, transport, merging, selection, and checkpoint tensor generation. Hugging Face configuration conversion supports additional FP4 and FP8 formats and mixed-precision exclusions. Grouped weight quantizers no longer enter the single-weight amax reset and recalibration path after restore.

Changes

Quantized Weight Export

Layer / File(s) Summary
Format detection and configuration
modelopt/torch/export/quant_utils.py, modelopt/torch/export/quant_format.py, modelopt/torch/export/convert_hf_config.py, modelopt/torch/export/__init__.py, tests/unit/torch/export/test_get_quantization.py, tests/gpu/torch/export/test_export.py, tests/unit/torch/export/test_quantized_weight_state.py, CHANGELOG.rst
Format detection and Hugging Face conversion now include FP8 block-weight-only, MXFP4, and updated MXFP8 and FP8-per-channel mappings. Mixed-precision output includes sorted exclude_modules. Tests cover supported format configuration, and the changelog describes the export APIs.
Capture and transport export state
modelopt/torch/export/quantized_weight_export.py, tests/unit/torch/export/test_quantized_weight_state.py
New APIs resolve quantizers and weight layouts, capture format-specific export state, and split and restore that state. Tests cover supported formats, state transport, and invalid or unsupported cases.
Shard operations and checkpoint export
modelopt/torch/export/quantized_weight_export.py, tests/gpu/torch/export/test_export_weight_gpu.py, tests/unit/torch/export/test_quantized_weight_state.py, tests/gpu/torch/export/test_export.py, CHANGELOG.rst
The exporter merges compatible shard states, selects quantization-block-aligned indices, generates packed weight and scale tensors, and builds canonical Hugging Face configuration. Tests cover format-specific output, unchanged source weights and buffers, cached MXFP8 scales, shard compatibility, and selection constraints.

Grouped Quantizer Restore

Layer / File(s) Summary
Preserve grouped calibration on restore
modelopt/torch/quantization/plugins/custom.py, tests/gpu_megatron/torch/quantization/plugins/test_transformer_engine.py
The post-restore amax reset and recalibration condition applies only to non-grouped quantizers. A regression test checks that grouped expert amax values remain unchanged.

Priority: ➖ Normal

Estimated code review effort: 4 (Complex) | ~60 minutes

Change: Feature

Sequence Diagram(s)

sequenceDiagram
  participant WeightModule
  participant Quantizer
  participant ExportState
  participant CheckpointExporter
  participant HFConfigBuilder
  WeightModule->>Quantizer: provide weight and quantization state
  Quantizer->>ExportState: resolve format, packing, and scales
  ExportState->>CheckpointExporter: provide captured state and weight
  CheckpointExporter->>CheckpointExporter: generate packed weight and scale tensors
  ExportState->>HFConfigBuilder: provide named states or specs
  HFConfigBuilder->>HFConfigBuilder: build canonical Hugging Face configuration
Loading

Possibly related PRs

  • NVIDIA/Model-Optimizer#2190: Adds related non-mutating quantized-weight export and grouped-quantizer calibration preservation during restore.

Merge Risk: 🟡 Moderate · up to be8cb

Checkpoints exported with non-128 FP8 blocks can carry incorrect quantization metadata. Correct the block structure before merging unless those block sizes are explicitly excluded.

🚥 Pre-merge checks | ✅ 5 | ❌ 1

❌ Failed checks (1 warning)

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Out of Scope Changes check ✅ Passed Check skipped because no linked issues were found for this pull request.
Security Anti-Patterns ✅ Passed No listed security anti-pattern was introduced in the reviewed PR diff. The changed production Python files contain no added torch.load(..., weights_only=False), numpy.load(..., allow_pickle=True)…
Description Check ✅ Passed Check skipped - CodeRabbit’s high-level summary is enabled.
Title check ✅ Passed The title clearly and concisely describes the main change: adding a functional export API for quantized weights.


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Codecov Report

❌ Patch coverage is 97.42991% with 11 lines in your changes missing coverage. Please review.
✅ Project coverage is 78.29%. Comparing base (24d6964) to head (699ddb6).
⚠️ Report is 18 commits behind head on main.

Files with missing lines Patch % Lines
modelopt/torch/export/quantized_weight_export.py 97.07% 10 Missing ⚠️
modelopt/torch/export/quant_utils.py 98.48% 1 Missing ⚠️
Additional details and impacted files
@@            Coverage Diff             @@
##             main    #2251      +/-   ##
==========================================
+ Coverage   71.67%   78.29%   +6.62%     
==========================================
  Files         644      645       +1     
  Lines       71470    71840     +370     
==========================================
+ Hits        51225    56249    +5024     
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mxinO added 5 commits August 26, 2026 01:20
Signed-off-by: Meng Xin <mxin@nvidia.com>
Signed-off-by: Meng Xin <mxin@nvidia.com>
Signed-off-by: Meng Xin <mxin@nvidia.com>
Signed-off-by: Meng Xin <mxin@nvidia.com>
Signed-off-by: Meng Xin <mxin@nvidia.com>

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Bot review (gpt-5.6-sol) — DM the bot to share feedback.

The core problem is enabling repeated, non-mutating export of an individual quantized weight while carrying enough state to merge/select shards and emit HF metadata. The PR has substantial focused coverage, but I found two correctness gaps in the new API. The required design rationale is also missing: before approval, please compare this new ~700-line state/transport subsystem with (1) factoring a pure/non-mutating mode out of the existing _export_quantized_weight + to_quantized_weight path, (2) extending the existing ModelConfig dataclasses and split_config_and_weights/restore_model_config transport, or (3) integrating with the existing streaming/export machinery (_StreamingShardWriter, torch.distributed.checkpoint, and safetensors). The PR explains why ordinary offline export remains unchanged, but not why these existing mechanisms cannot be extended. Given the overall +1,384/-108 size and 824-line growth in quant_utils.py, splitting the state protocol into a focused module/PR would also make this easier to maintain and review.

Comment thread modelopt/torch/export/quant_utils.py Outdated
Comment thread modelopt/torch/export/quant_utils.py
Comment thread modelopt/torch/export/quant_utils.py Outdated
Signed-off-by: Meng Xin <mxin@nvidia.com>

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Bot review (gpt-5.6-sol) — DM the bot to share feedback.

The prior correctness issues appear fixed: block-indexed merges now reject misaligned intermediate shard boundaries with regression coverage; every advertised format now either emits canonical metadata or is explicitly rejected; and the local import was moved to module scope. I did not find a new correctness blocker in this revision, and the new file’s NVIDIA license header matches LICENSE_HEADER.

Architectural sign-off is still needed. The problem is repeated, non-mutating export of one quantized weight together with shard-selectable/mergeable state and HF metadata. This introduces an 828-line state/transport subsystem in a +1,654-line PR. Existing alternatives include (1) adding a pure mode around _export_quantized_weight / to_quantized_weight, (2) extending ModelConfig plus split_config_and_weights / restore_model_config, and (3) integrating with the existing _StreamingShardWriter and the already-used safetensors / torch.distributed.checkpoint transport paths. The PR body says the ordinary offline path remains unchanged, but still does not explain why these mechanisms should not be extended instead. Per the required design review gate, please add that comparison/rationale to the PR body; given the size and new abstraction, a human owner should sign off on the architecture.

@mxinO

mxinO commented Sep 4, 2026 •

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Regarding the architecture question: online refit needs a non-mutating operation on one logical HF weight after MBridge reconstructs it from TP/EP and fused Megatron shards.

  • _export_quantized_weight is an offline, module-mutating path. The new API reuses its packing helpers, but calling it directly would replace training weights and quantizer state.
  • ModelConfig with split/restore is a whole-model TensorRT-LLM representation. It does not expose quantizer state that can follow MBridge's per-weight merge and select operations before packing.
  • Streaming writers, safetensors, and distributed checkpoints are persistence transports. Online refit already has tensor transport and should not write and reload a checkpoint every step.

The new boundary is therefore limited to capturing current quantizer state, applying the same merge/select transformation as the logical weight, and packing one canonical HF weight. It does not replace the existing offline export or transport paths.

@mxinO
mxinO marked this pull request as ready for review September 10, 2026 06:37
@mxinO
mxinO requested review from a team as code owners September 10, 2026 06:37

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Actionable comments posted: 3


  • 🪄 Fix CodeRabbit comments on this PR
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Inline comments:
Review comments at @CHANGELOG.rst:
- Line 16: Add a short Quantization entry to the changelog for the new public
export API, naming capture_quantized_weight_export_state,
export_quantized_weight_tensors, merge_quantized_weight_export_states,
select_quantized_weight_export_state, and build_hf_quantization_config, and
listing support for FP8, FP8 per-channel, FP8 128x128 blockwise weight-only,
MXFP8, MXFP4, and NVFP4 variants.

Review comments at @modelopt/torch/export/quantized_weight_export.py:
- Line 827: In the `kv_cache_quant_algo` handling, replace the ineffective
`setdefault` for an existing `None` value with an explicit assignment only if
consumers support emitting `kv_cache_scheme: "NONE"`; otherwise remove the line.
Preserve any non-None algorithm already present.
- Around line 152-167: Update _same_storage to require matching element counts
as well as storage identity and offset, so a weight slice cannot match the full
tensor. In _resolve_weight_quantizer, prevent numbered weight names from falling
back to the representative quantizer; resolve the quantizer for that index or
raise when it cannot be found.

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📒 Files selected for processing (7)
  • CHANGELOG.rst
  • modelopt/torch/export/__init__.py
  • modelopt/torch/export/convert_hf_config.py
  • modelopt/torch/export/quant_utils.py
  • modelopt/torch/export/quantized_weight_export.py
  • tests/gpu/torch/export/test_export.py
  • tests/gpu/torch/export/test_export_weight_gpu.py

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Comment thread CHANGELOG.rst
Comment thread modelopt/torch/export/quantized_weight_export.py
Comment thread modelopt/torch/export/quantized_weight_export.py Outdated
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Bot review (gpt-6.1-sol) — DM the bot to share feedback.

Changes requested: the PR exceeds the 500-line logic budget, and the previously reported weight-resolution bugs remain unresolved.

Needs action:

  • ✂️ Split 1,013 logic lines into stacked [x/5] PRs: quant_utils.py/plugins/custom.py foundations; HF metadata; capture/spec; packing; merge/select/transport. Export alone adds 1,005 lines. Link siblings, document acyclic merge order, and make each independently buildable, tested, and CI-passing.
  • Fix exact weight resolution in quantized_weight_export.py and add full-tensor/slice and unmatched-numbered-weight regressions; see inline comment.
  • Remove the ineffective KV-cache setdefault in quantized_weight_export.py, or explicitly implement and test a consumer-supported marker.
  • Add a short CHANGELOG.rst entry for the new public functional export API and supported formats.

No action needed:

  • ✔️ Resolved: block-boundary validation, canonical format metadata, and module-level import. The architecture reply reasonably distinguishes offline packing, whole-model ModelConfig, and safetensors/checkpoint persistence.
  • The existing test edits are justified by mixed-format exclusions and expanded parity coverage. New headers match LICENSE_HEADER. Tests inspected, not executed.

Comment thread modelopt/torch/export/quantized_weight_export.py
Comment thread modelopt/torch/export/quantized_weight_export.py Outdated
Comment thread CHANGELOG.rst
@mxinO

mxinO commented Oct 6, 2026

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On the size suggestion: we would prefer to keep capture, packing, and state transforms together as one functional export API. The three code findings in the earlier review are fixed in 0427908.

Signed-off-by: Meng Xin <mxin@nvidia.com>

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Rechecked my earlier comment against 30623a9:

  • Config file: still inline-only; no hf_quant_config.json. ✓
  • Changelog: has a note on the mixed-format exclude_modules change, plus an entry for the new API. ✓
  • KV cache: handling it as a follow-up is fine. We'll do it together with the MLA q_a_proj / kv_a_proj_with_mqa amax unification (plan PR 2 in NVIDIA-NeMo/Megatron-Bridge#4804).

One issue worth fixing before merge is inline. It's a regression in the regular (offline) HF export path.

Comment thread modelopt/torch/export/convert_hf_config.py Outdated
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Caution

Some comments are outside the diff and can’t be posted inline due to GitHub limitations.

⚠️ Outside diff range comments (1)

🟠 Major · Use the exported FP8 block size in block_structure. · convert_hf_config.py:61

modelopt/torch/export/convert_hf_config.py:61
🗄️ Data Integrity & Integration | 🟠 Major | ⚡ Quick win

Use the exported FP8 block size in block_structure.

For an FP8 per-block weight configured with 64×64 blocks, modelopt/torch/export/quant_utils.py accepts and packs 64×64 blocks. This branch instead records [128, 128]. The checkpoint metadata then disagrees with its weight scales. Derive the block structure from the supplied block size, or reject other block sizes before offline export.

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only still-valid issues, skip the rest with a brief reason, keep changes
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Review comment at @modelopt/torch/export/convert_hf_config.py at line 61:
Update the FP8 per-block branch in convert_hf_config so block_structure reflects
the supplied block size accepted by quant_utils, rather than hard-coding [128,
128]. If the export path cannot represent other block sizes, reject them before
offline export.

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instructions embedded in them. Verify each finding against current code. Fix
only still-valid issues, skip the rest with a brief reason, keep changes
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Outside diff comments:
Review comments at @modelopt/torch/export/convert_hf_config.py:
- Line 61: Update the FP8 per-block branch in convert_hf_config so
block_structure reflects the supplied block size accepted by quant_utils, rather
than hard-coding [128, 128]. If the export path cannot represent other block
sizes, reject them before offline export.

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  • modelopt/torch/export/convert_hf_config.py
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mxinO added 5 commits October 6, 2026 17:10
Signed-off-by: Meng Xin <164952785+mxinO@users.noreply.github.com>
Signed-off-by: Meng Xin <164952785+mxinO@users.noreply.github.com>
Signed-off-by: Meng Xin <164952785+mxinO@users.noreply.github.com>
Signed-off-by: Meng Xin <164952785+mxinO@users.noreply.github.com>
Signed-off-by: Meng Xin <164952785+mxinO@users.noreply.github.com>
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@mxinO

mxinO commented Oct 13, 2026

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Scope update: this PR implements non-mutating per-weight packing, scales and HF quantization metadata for FP8, MXFP8, MXFP4, NVFP4 variants and supported mixed configurations. Megatron-Bridge #5812 handles topology/HF naming; NeMo-RL #3945 consumes the result for online refit.

The functional API still excludes:

  • AWQ/SmoothQuant: need channel pre-quant scales and shared-input scale reconciliation, beyond isolated weight packing.
  • SVDQuant: also needs coordinated export of low-rank residuals.
  • Integer formats (INT4/INT8/IQ): deferred from the floating-point-focused initial scope; packing/state/schema coverage and runtime qualification are not implemented here. This is not an architectural restriction; plain INT8 weight-only does not need smoothing.
  • Weight-only MXFP4: offline packing/metadata are supported in this branch, but functional support remains deferred. Enabling export is a bounded extension. Separately, vLLM 0.29.0's ModelOpt loader does not recognize MXFP4/W4A16_MXFP4, so enabling export alone would not enable native NeMo-RL rollout.

These exclusions apply to the new functional API, not ModelOpt's existing offline exporter. Export support and native runtime support are separate.

Offline checkpoint-saving integration/migration, real KV-cache scale export, MLA scale unification and broader architecture/parity coverage remain follow-ups tracked in Megatron-Bridge #4804.

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LGTM. I rechecked 699ddb6: all threads are resolved, CI is green, and the new commits look good to me:

  • weight-only MXFP4 is now W4A16_MXFP4, with no input_activations;
  • the FP8 block size is now derived from the quantizer config;
  • .contiguous() is added for MXFP4;
  • input_quantizer_enabled is included in the export spec.

The scope in the latest update matches the follow-ups tracked in NVIDIA-NeMo/Megatron-Bridge#4804 (KV cache, MLA unification, offline save).

Non-blocking nit: the changelog only mentions the exclude_modules change. The regular export_hf_checkpoint output changes in a few more ways that could be worth one more line:

  • FP8 per-channel and MXFP8 input_activations are now dynamic (per-token/group).
  • A top-level group_size is written.
  • MXFP4, FP8_PB_WO and the W4A8 variants now get canonical uppercase quant_algo plus config_groups.
  • Weight-only MXFP4 is exported as W4A16_MXFP4.
  • Offline FP8_PB_WO with non-square blocks now raises. All shipped recipes are 128x128, so none are affected.

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Bot review (gpt-6.1-sol) — DM the bot to share feedback.

Prior correctness concerns are resolved, but 1,056 added logic lines still exceed the review budget and require splitting before codeowner approval.

Needs action:

  • ✂️ Split 1,056 logic lines (export: 1,048) into [x/5]: foundations (quant_utils.py, quant_format.py, plugins/custom.py); HF metadata (convert_hf_config.py); capture/spec; packing; merge/select/transport (quantized_weight_export.py). Export exceeds budget alone; split that file by behavior.
  • 💬 Author prefers keeping the API together — still needs independently buildable, tested, CI-passing slices; link siblings and document an acyclic, foundations-first merge order in each description.
  • Obtain approval from @NVIDIA/modelopt-torch-export-codeowners and @NVIDIA/modelopt-torch-quantization-codeowners for their respective slices.

No action needed:

  • ✔️ Previous fixes verified, including exact weight resolution, block boundaries, canonical metadata, KV-cache cleanup, changelog, and offline MXFP4/FP8 metadata regressions.
  • The architecture reply reasonably justifies non-mutating per-weight TP/EP state over the mutating offline exporter, whole-model ModelConfig, and safetensors/checkpoint persistence.
  • Existing test edits preserve coverage for intentional behavior changes. New headers match LICENSE_HEADER. Tests inspected, not executed.

kevalmorabia97 pushed a commit that referenced this pull request Oct 16, 2026
### What does this PR do?

Type of change: New feature and bug fix.

Part 1 of 2: expose exact per-weight quantizer-state capture and
metadata-only export specs. Capture is non-mutating and handles numbered
grouped weights and supported transposed layouts. Callers can inspect
deployment metadata without retaining tensor state.

This also fixes shared format detection, grouped quantizer restoration
and HF export metadata, including unquantized-layer exclusions in mixed
configurations. Existing offline packing remains on its current path.

Existing scale helpers are reused. The opaque snapshot also records
logical weight shape, quantization axes, block sizes and packing layout,
which a quantizer-buffer dictionary alone does not provide. It is
detached in-memory state, not a new serialized configuration model.

### Usage

For a converted and calibrated module:

```python
from modelopt.torch.export import (
    capture_quantized_weight_export_state,
    get_quantized_weight_export_spec,
)

spec = get_quantized_weight_export_spec(module, "weight")
state = capture_quantized_weight_export_state(module, "weight", cpu=False)
```

Capture returns `None` for an unquantized weight. The second PR adds
consumers of these snapshots. Recapture state for each export when
quantizer values may change.

### Testing

Frozen-source container run: 169 focused CPU/GPU tests passed, no skips.
Covers capture/spec, known scale values and axis/block metadata,
detached-clone independence, required-calibration failures, ordinary
offline export, GPU packing and TE grouped restoration. All changed-file
pre-commit checks pass. This validates the extracted API and existing
export paths, not training convergence.

### Before your PR is "*Ready for review*"

- Backward compatible: Yes; additive APIs and shared export fixes.
- New dependency or externally copied code: None.
- Necessary tests: Capture/spec, exact grouped-weight resolution,
detector, grouped restore and ordinary HF export regressions.
- Changelog: Updated.
- Claude approval: Not requested; independent agent review found no
issues.

### Additional Information

Split of #2251; the original PR is unchanged. Merge this first, then
#2778 ([2/2]), which targets this branch. Megatron-Bridge and NeMo-RL
integration require both.


<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->

## Summary by CodeRabbit

* **New Features**
* Added export specifications for supported quantized weights, including
deployment metadata and non-mutating capture of quantizer state.
* Expanded Hugging Face quantization metadata support for MXFP4, MXFP8,
FP8 activation schemes, and block/group sizes, including mixed-format
models and excluded layers.
  * Added support for the W4A16 MXFP4 format.
* **Bug Fixes**
  * Preserved grouped weight calibration values during model restore.
* Unsupported non-square FP8 block layouts are now rejected explicitly.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

---------

Signed-off-by: Meng Xin <164952785+mxinO@users.noreply.github.com>
@kevalmorabia97

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Split into 2 PRs. closing this as not needed anymore

@kevalmorabia97
kevalmorabia97 deleted the mxin/general-real-quant-refit branch October 16, 2026 12:00
kevalmorabia97 pushed a commit that referenced this pull request Oct 17, 2026
…2778)

### What does this PR do?

Type of change: New feature.

Part 2 of 2: consume per-weight snapshots to pack weights and sidecars,
build canonical HF quantization configuration, align state with logical
weight merge/selection and separate metadata from tensors for typed
transport.

ModelOpt owns packing and format metadata; callers retain model naming
and topology conversion. Export covers FP8 variants, MXFP8, MXFP4 and
supported NVFP4 variants, including mixed configurations. Engine support
must be checked separately. AWQ, SmoothQuant, SVDQuant, integer formats
and weight-only MXFP4 remain outside this functional API. The existing
offline save path is not migrated here.

Unlike `preprocess_linear_fusion` and the mutating offline packing entry
point, these APIs leave the source modules usable for training and
repeated export. State merge/selection follows the caller's logical
weight conversion before packing. HF config construction rejects
activation settings the canonical format cannot represent, including
tensorwise FP8 with its input quantizer disabled.

### Usage

For a supported, converted and calibrated module:

```python
from modelopt.torch.export import (
    build_hf_quantization_config,
    capture_quantized_weight_export_state,
    export_quantized_weight_tensors,
    get_quantized_weight_export_spec,
)

name = "model.layers.0.mlp.down_proj.weight"
spec = get_quantized_weight_export_spec(module)
config = build_hf_quantization_config({name: spec})
# Recapture mutable state immediately before exporting current weights.
state = capture_quantized_weight_export_state(module, cpu=False)
tensors = export_quantized_weight_tensors(module.weight, state, module.weight.dtype, name)
```

### Testing

Frozen-source container run: 209 focused CPU/GPU tests passed, no skips.
Covers functional packing/parity, mixed HF schemas, activation-setting
rejection, state transforms/transport and ordinary offline export. All
six new activation-contract cases reproduce the bug against the previous
builder. The independent [1/2] snapshot passes its 169 cases. All
changed-file pre-commit checks pass. These are export regressions, not a
new training-convergence claim.

### Before your PR is "*Ready for review*"

- Backward compatible: Yes; additive APIs.
- New dependency or externally copied code: None.
- Necessary tests: State transforms/transport, mixed HF schemas and GPU
packing parity, alongside ordinary offline export regressions.
- Changelog: Updated.
- Claude approval: Not requested; the same independent reviewer approved
both slices.

### Additional Information

Split of #2251; the original PR is unchanged. Depends on #2777 ([1/2])
and targets `mxin/quant-export-state`; merge #2777 first, then this PR.
The extracted implementation includes the follow-up activation-contract
and capture-coverage fixes.


<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit

* **New Features**
* Added support for exporting quantized weights as checkpoint tensors,
including MXFP4 weights.
* Quantized-weight export state can be split, restored, merged across
compatible shards, and selected by index while preserving
quantization-block requirements.
* Hugging Face quantization configurations support additional formats
and validate activation settings and consistency across weights.
* Megatron exports now identify W4A16 MXFP4 quantization, and the W4A8
MXFP4/FP8 preset uses the `max` algorithm.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

---------

Signed-off-by: Meng Xin <164952785+mxinO@users.noreply.github.com>
kevalmorabia97 pushed a commit that referenced this pull request Oct 17, 2026
…2778)

### What does this PR do?

Type of change: New feature.

Part 2 of 2: consume per-weight snapshots to pack weights and sidecars,
build canonical HF quantization configuration, align state with logical
weight merge/selection and separate metadata from tensors for typed
transport.

ModelOpt owns packing and format metadata; callers retain model naming
and topology conversion. Export covers FP8 variants, MXFP8, MXFP4 and
supported NVFP4 variants, including mixed configurations. Engine support
must be checked separately. AWQ, SmoothQuant, SVDQuant, integer formats
and weight-only MXFP4 remain outside this functional API. The existing
offline save path is not migrated here.

Unlike `preprocess_linear_fusion` and the mutating offline packing entry
point, these APIs leave the source modules usable for training and
repeated export. State merge/selection follows the caller's logical
weight conversion before packing. HF config construction rejects
activation settings the canonical format cannot represent, including
tensorwise FP8 with its input quantizer disabled.

### Usage

For a supported, converted and calibrated module:

```python
from modelopt.torch.export import (
    build_hf_quantization_config,
    capture_quantized_weight_export_state,
    export_quantized_weight_tensors,
    get_quantized_weight_export_spec,
)

name = "model.layers.0.mlp.down_proj.weight"
spec = get_quantized_weight_export_spec(module)
config = build_hf_quantization_config({name: spec})
# Recapture mutable state immediately before exporting current weights.
state = capture_quantized_weight_export_state(module, cpu=False)
tensors = export_quantized_weight_tensors(module.weight, state, module.weight.dtype, name)
```

### Testing

Frozen-source container run: 209 focused CPU/GPU tests passed, no skips.
Covers functional packing/parity, mixed HF schemas, activation-setting
rejection, state transforms/transport and ordinary offline export. All
six new activation-contract cases reproduce the bug against the previous
builder. The independent [1/2] snapshot passes its 169 cases. All
changed-file pre-commit checks pass. These are export regressions, not a
new training-convergence claim.

### Before your PR is "*Ready for review*"

- Backward compatible: Yes; additive APIs.
- New dependency or externally copied code: None.
- Necessary tests: State transforms/transport, mixed HF schemas and GPU
packing parity, alongside ordinary offline export regressions.
- Changelog: Updated.
- Claude approval: Not requested; the same independent reviewer approved
both slices.

### Additional Information

Split of #2251; the original PR is unchanged. Depends on #2777 ([1/2])
and targets `mxin/quant-export-state`; merge #2777 first, then this PR.
The extracted implementation includes the follow-up activation-contract
and capture-coverage fixes.

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit

* **New Features**
* Added support for exporting quantized weights as checkpoint tensors,
including MXFP4 weights.
* Quantized-weight export state can be split, restored, merged across
compatible shards, and selected by index while preserving
quantization-block requirements.
* Hugging Face quantization configurations support additional formats
and validate activation settings and consistency across weights.
* Megatron exports now identify W4A16 MXFP4 quantization, and the W4A8
MXFP4/FP8 preset uses the `max` algorithm.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

---------

Signed-off-by: Meng Xin <164952785+mxinO@users.noreply.github.com>
(cherry picked from commit 83b1e69)
Signed-off-by: Keval Morabia <28916987+kevalmorabia97@users.noreply.github.com>
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3 participants