[Bugfix] GLM-5.3-Flash: keep FP8 weight/scale pairs across load_weights calls by MadhavJivrajani · Pull Request #56584 · vllm-project/vllm

MadhavJivrajani · 2026-09-12T07:53:45Z

Purpose

Glm5NextModel.load_weights (GLM-5.3-Flash) dequantizes the block-FP8 q_a_proj, kv_a_proj_with_mqa, q_b_proj, o_proj and indexer.wk tensors to BF16 once both the weight and its weight_scale_inv have been seen, parking the first half in a pending dict (_pending_wk_fp8). That dict is a local of one load_weights call.

For more details on repro and where the code comes from, see #56583

Fix. Persist the pending dict on the model instance (self._pending_fp8_pairs), mirroring #46168. Completed pairs are already popped by the helpers, so the dict is empty again after a full load. The single-call path is unchanged.

Related: #43163 / #43464, #41749 / #42244, #38991, sgl-project/sglang#37369 (the sglang loader's version of the same problem), https://huggingface.co/zai-org/GLM-5.3-Flash/discussions/23 (vLLM on H100, resolved by disabling distributed streaming).

Fixes #56583

Test Plan

New CPU-only regression test, in the style of tests/models/kimi_k3/test_weight_loading.py. It drives the real Glm5NextModel.load_weights, Glm5NextForCausalLM.load_weights and Glm5NextForConditionalGeneration.load_weights on a minimal module tree holding layer 7's BF16 fused_qkv_a_proj.weight, with four synthetic checkpoint tensors (FP8 q_a_proj.weight, kv_a_proj_with_mqa.weight, their weight_scale_inv):

pytest tests/models/glm5next/test_weight_loading.py -q

test	stream
`test_fp8_pairs_complete_within_one_call`	weight, scale, weight, scale in one call (control)
`test_fp8_pairs_split_across_load_weights_calls`	weights in call 1, scales in call 2
`…stream_order…[per-shard-order-vision-last]`	HF-named stream through the multimodal wrapper, `model.visual.*` last (control)
`…stream_order…[vision-tensor-between-weight-and-scale]`	same five tensors, `model.visual.*` between the weights and the scales

Also ran ruff check / ruff format --check on both files.

Test Result

Run in unmodified images on a CPU-only VM (docker run --entrypoint bash -e CUDA_VISIBLE_DEVICES= <image>, pip install pytest), then again with this change applied to the image's installed model.py:

image	vLLM	before	after
`vllm/vllm-openai:glm53-flash`	0.28.1rc1.dev580+g385dce36b	2 failed, 2 passed	4 passed
`vllm/vllm-openai:nightly`	0.28.1rc1.dev681+ge7edf17ce	2 failed, 2 passed	4 passed

Before (both images):

FAILED tests/models/glm5next/test_weight_loading.py::test_fp8_pairs_split_across_load_weights_calls
  AssertionError: fused_qkv_a_proj was never written: the FP8 half-pairs parked in the first call were discarded when it returned
  assert 'layers.7.self_attn.fused_qkv_a_proj.weight' in set()
FAILED tests/models/glm5next/test_weight_loading.py::test_multimodal_stream_order_does_not_change_loaded_weights[vision-tensor-between-weight-and-scale]
  AssertionError: fused_qkv_a_proj was never written for this stream order
  assert 'language_model.model.layers.7.self_attn.fused_qkv_a_proj.weight' in {'visual.patch_embed.proj.weight'}
2 failed, 2 passed

After (both images):

PASSED tests/models/glm5next/test_weight_loading.py::test_fp8_pairs_complete_within_one_call
PASSED tests/models/glm5next/test_weight_loading.py::test_fp8_pairs_split_across_load_weights_calls
PASSED tests/models/glm5next/test_weight_loading.py::test_multimodal_stream_order_does_not_change_loaded_weights[per-shard-order-vision-last]
PASSED tests/models/glm5next/test_weight_loading.py::test_multimodal_stream_order_does_not_change_loaded_weights[vision-tensor-between-weight-and-scale]
4 passed

AI assistance: the fix, the regression test and the partition replay were developed with Claude (Anthropic); I reviewed the changed lines and ran the tests and the image verification myself.

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claude

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github-actions · 2026-09-12T07:55:45Z

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mergify · 2026-09-16T09:58:01Z

This pull request has merge conflicts that must be resolved before it can be
merged. Please rebase the PR, @MadhavJivrajani.

https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/working-with-forks/syncing-a-fork

NickLucche

Thanks @MadhavJivrajani

NickLucche · 2026-11-09T14:45:06Z

/ci run

github-actions · 2026-11-09T14:45:13Z

✅ @MadhavJivrajani, CI is now available for this PR.

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github-actions · 2026-11-09T14:45:31Z

❌ This PR is 3342 commits behind upstream main. The bot could not merge upstream main into this branch (API returned 422: expected head sha didn’t match current head ref.). No new CI build was started. Either merge or rebase onto the latest main yourself and rerun /ci run, or use /ci run --allow-stale to test this branch as is.

NickLucche · 2026-11-09T14:45:35Z

/ci run

github-actions · 2026-11-09T14:46:00Z

✅ Triggered Buildkite CI #101127 for commit e00b4155aedc.

mergify · 2026-11-09T14:52:12Z

Hi @MadhavJivrajani, the pre-commit checks have failed. Please run:

uv pip install pre-commit>=4.5.1
pre-commit install
pre-commit run --all-files

Then, commit the changes and push to your branch.

For future commits, pre-commit will run automatically on changed files before each commit.

…ts calls Glm5NextModel.load_weights dequantizes the block-FP8 q_a_proj, kv_a_proj_with_mqa, q_b_proj, o_proj and indexer.wk tensors to BF16 once both the weight and its weight_scale_inv have been seen, parking the first half in a pending dict. That dict was local to one load_weights call. AutoWeightsLoader invokes a child's load_weights once per contiguous run of a top-level prefix (itertools.groupby), so a stream such as `language_model..., visual..., language_model...` calls it twice, and any pair whose halves land in different calls was silently dropped: the fused parameter was never written and nothing was reported. Streaming loaders that reorder tensors hit this. With the Run:ai Model Streamer in distributed mode (runai-model-streamer 0.16.1, default partition policy `chunks`), tensors are dealt to ranks by size and each rank emits its slice of the vision-tower shard as a separate burst, so a replay of the real partition over GLM-5.3-Flash's 62 shard headers puts a weight and its scale in different load_weights calls for 18 of the 48 FP8 pairs, across 10 of the 12 MLA layers. Per-shard loading splits none, which is why the same checkpoint served correctly from disk and produced garbled output when streamed. Persist the pending dict on the model instance, as vllm-project#46168 did for DeepSeek-V2. Completed pairs are popped by the helpers, so the dict is empty again after a full load. Add tests/models/glm5next/test_weight_loading.py, which drives the real load_weights implementations on a minimal module tree on CPU: a pair delivered in one call, the same pair split across two calls, and the same five checkpoint-named tensors through Glm5NextForConditionalGeneration with and without a model.visual.* tensor between a weight and its scale. The split-call and vision-between cases fail before this change and pass after it on vllm/vllm-openai:glm53-flash (0.28.1rc1.dev580+g385dce36b) and vllm/vllm-openai:nightly (0.28.1rc1.dev681+ge7edf17ce). Co-authored-by: Claude Signed-off-by: Madhav Jivrajani <madhav.jiv@gmail.com>

Rewrite ``code`` as `code` in the test docstrings (check-docstring-style) and ignore mypy's type-abstract on the two object.__new__ calls that build the model stubs without running __init__. Co-authored-by: Claude Signed-off-by: Madhav Jivrajani <madhav.jiv@gmail.com>

mergify · 2026-11-13T20:19:52Z

Hi @MadhavJivrajani, the pre-commit checks have failed. Please run:

uv pip install pre-commit>=4.5.1
pre-commit install
pre-commit run --all-files

Then, commit the changes and push to your branch.

For future commits, pre-commit will run automatically on changed files before each commit.

…pairs Signed-off-by: Madhav Jivrajani <madhav.jiv@gmail.com>

MadhavJivrajani · 2026-11-13T20:44:17Z

Thanks @NickLucche! Looks like CI was failing on main, fixed in #67549

Do you mind enabling merge again?

MadhavJivrajani requested review from AndreasKaratzas, DarkLight1337 and ywang96 as code owners September 12, 2026 07:53

claude Bot reviewed Sep 12, 2026

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mergify Bot added glm bug Something isn't working labels Sep 12, 2026

MadhavJivrajani requested a review from 22quinn as a code owner September 12, 2026 08:06

MadhavJivrajani force-pushed the glm5next-persist-fp8-pairs branch from d029450 to f3f43be Compare September 12, 2026 08:19

mergify Bot added the needs-rebase label Sep 16, 2026

MadhavJivrajani force-pushed the glm5next-persist-fp8-pairs branch from f3f43be to f194383 Compare September 18, 2026 22:11

mergify Bot removed the needs-rebase label Sep 18, 2026

NaccOll mentioned this pull request Sep 28, 2026

[Bug][ROCm] v0.30.0: GLM-5.3-Flash cannot boot on gfx942 — ROCMAiterMLASparseImpl missing record_logical_topk_ready (#57252 not in the release) #59027

Closed

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pllopis mentioned this pull request Sep 29, 2026

[Bugfix] Preserve FP8 indexer WK pairs across load_weights calls #59223

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NickLucche approved these changes Nov 9, 2026

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NickLucche added the ready ONLY add when PR is ready to merge/full CI is needed label Nov 9, 2026

NickLucche enabled auto-merge (squash) November 9, 2026 14:45

MadhavJivrajani added 2 commits November 13, 2026 12:14

auto-merge was automatically disabled November 13, 2026 20:15
Head branch was pushed to by a user without write access

MadhavJivrajani force-pushed the glm5next-persist-fp8-pairs branch from e00b415 to 5430b76 Compare November 13, 2026 20:15

Merge remote-tracking branch 'origin/main' into glm5next-persist-fp8-…

006f10d

…pairs Signed-off-by: Madhav Jivrajani <madhav.jiv@gmail.com>

MadhavJivrajani requested a review from NickLucche November 13, 2026 20:44

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[Bugfix] GLM-5.3-Flash: keep FP8 weight/scale pairs across load_weights calls - #56584

[Bugfix] GLM-5.3-Flash: keep FP8 weight/scale pairs across load_weights calls#56584
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