[Model] Enable LoRA support for tower and connector in GLM-ASR by JonSnow1807 · Pull Request #53149 · vllm-project/vllm

JonSnow1807 · 2026-08-20T18:26:12Z

Purpose

Part of #31479 (LoRA for the tower and connector of more multimodal models).

Enable tower/connector LoRA for GLM-ASR (GlmAsrForConditionalGeneration). The audio tower (GlmAsrEncoder) and projector (GlmAsrMultiModalProjector) are already vLLM-native linear layers and get_mm_mapping already maps them, so this PR adds the token-count helpers that the LoRA mapping needs:

get_num_mm_encoder_tokens / get_num_mm_connector_tokens: every 30s chunk is padded to 3000 mel frames, which the conv stack downsamples to audio_config.max_position_embeddings (1500) tower rows; the projector runs on the 4x frame-merged output before the padded frames are trimmed, so it sees 375 rows per chunk (also the number of LM tokens a full chunk yields). Only the last chunk of an audio can yield fewer LM tokens, so num_chunks = ceil(num_audio_tokens / 375).
get_mm_lora_token_counts override: derives the exact per-item counts from mm_kwargs["input_features"] (chunks x padded length). num_mm_embeds alone is not invertible when the tail chunk is nearly empty (e.g. a 30.02s audio yields 375 LM tokens but 2 chunks / 3000 tower rows).

Before this change, starting GLM-ASR with --enable-tower-connector-lora fails at engine init (TypeError: empty(): argument 'size' ... NoneType from get_punica_wrapper, because the stub helper returns None).

Not a duplicate: GLM-ASR is not on the done/WIP list of #31479 and no comment claims it (I claimed it on the issue before opening this PR); gh pr list --state open --search "31479 in:body" (LFM2-VL #51498, Intern-S1 #48129, Cosmos3-Edge #51949, Voxtral #45697, Qwen2-Audio #45944, Mistral3 #42228, Llama Nemotron VL #52749), --search "LoRA tower connector", --search "get_num_mm_encoder_tokens" and --search "GLM-ASR" return nothing for this model. Related but not overlapping: #53092 replaces the hasattr-based support detection with an explicit supports_tower_connector_lora flag — if it lands first, this PR just needs that one-line flag added on the class (happy to rebase).

Test Plan

Verified locally on 1x NVIDIA A100-40GB with zai-org/GLM-ASR-Nano-2512 (dedicated test files were included in earlier revisions of this PR and removed at reviewer request; results below are from those runs):

Helper math checked against the real HF processor for 1s, 30s, 30.02s, 55s and 90s audio (chunk counts, tower/connector rows, LM token bound), including the nearly-empty tail-chunk case where num_mm_embeds alone is not invertible.
End-to-end with enable_lora=True, enable_tower_connector_lora=True and synthetic PEFT adapters targeting all 194 tower + projector linears: a zero-lora_B adapter reproduces the base outputs bit-exactly (text + cumulative logprob), tower-only and projector-only perturbing adapters each change the outputs, and a mixed 4-item batch routes each item to its own adapter. Covers 1-chunk (16s) and 2-chunk (55s) audio.
Regression: tests/lora/test_qwenvl.py, tests/lora/test_lora_manager.py, tests/v1/worker/test_gpu_model_runner.py -k mm_lora, tests/models/multimodal/processing/test_common.py -k GLM-ASR, tests/models/test_initialization.py -k GlmAsr, tests/models/multimodal/generation/test_transformers_audio.py -k GLM-ASR.

Test Result

helper/processor checks (18 cases)                                 all passed
e2e tower/connector LoRA (identity/tower/connector/mixed batch)    passed (run 4x)
tests/lora/test_qwenvl.py                                          4 passed, 2 skipped (CUDA skips)
tests/lora/test_lora_manager.py                                    20 passed
tests/v1/worker/test_gpu_model_runner.py -k mm_lora                1 passed
tests/models/multimodal/processing/test_common.py -k GLM-ASR       3 passed
tests/models/test_initialization.py -k GlmAsr                      1 passed
tests/models/multimodal/generation/test_transformers_audio.py -k GLM-ASR  1 passed

Greedy transcription of the mary_had_lamb (16s, 1 chunk) / 55s (2 chunks) assets, cumulative logprob with VLLM_BATCH_INVARIANT=1:

adapter	short	long
none	-3.9606	-5.5061
identity (lora_B = 0, all tower+projector modules)	-3.9606 (identical text)	-5.5061 (identical text)
tower-only perturbation	-3.6926	-5.8229
projector-only perturbation	-3.8078	-5.4760

Mixed batch [identity, tower, connector, identity] reproduces the per-adapter results item-wise.

Disclosure

AI assistance was used in preparing this PR.

Assisted-by: AI coding assistant Signed-off-by: JonSnow1807 <JonSnow1807@users.noreply.github.com>

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github-actions · 2026-08-20T18:26:22Z

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linitra24 · 2026-08-21T02:02:57Z

+
+        # `num_mm_embeds` is not invertible when the last chunk is nearly
+        # empty (it yields zero LM tokens but still occupies a full chunk in
+        # the tower), so derive the counts from the chunks themselves.


If num_mm_embeds is not invertible, are the implementations of get_num_mm_encoder_tokens and get_num_mm_connector_tokens really necessary here?

Yes, they are still needed. The LoRA manager sizes the punica wrappers at engine init via get_mm_lora_token_counts(mm_kwargs=None, ...) (_maybe_init_mm in vllm/lora/model_manager.py), and that path falls back to these two helpers. It is the same call that crashes on current main because the interface stubs return None. The mm_kwargs branch only refines per-item counts at runtime.

linitra24 · 2026-08-21T02:13:20Z

+
+
+@pytest.fixture(scope="module")
+def glmasr_tower_connector_loras(tmp_path_factory) -> dict[str, LoRARequest]:


Could we test this with a real LoRA adapter?

There is no public GLM-ASR tower/connector adapter on the Hub. The synthetic ones also catch something a trained adapter cannot: the zero lora_B adapter has to match base outputs exactly, so any off-by-one in the row counts fails immediately. If the maintainers want a real adapter too, I can train and upload a small one.

please remove this test

Done, removed.

linitra24 · 2026-08-21T02:13:47Z

@@ -0,0 +1,215 @@
+# SPDX-License-Identifier: Apache-2.0


Can we remove this test?

I would prefer to keep it. It is the only CPU-only check of the counts against the real HF processor, including the 30.02s tail-chunk case that motivated the get_mm_lora_token_counts override. I can trim the stub-based cases if it feels long.

please remove this test

Done, removed.

Assisted-by: AI coding assistant Signed-off-by: JonSnow1807 <JonSnow1807@users.noreply.github.com>

JonSnow1807 · 2026-08-22T05:32:38Z

Rebased on the #53092 change: added supports_tower_connector_lora = True so the new detection flag picks this model up. Re-verified on 1x A100-40GB against a merge with current main: engine init with --enable-tower-connector-lora works and the tower/connector adapter e2e check passes.

[Model] Enable LoRA support for tower and connector in GLM-ASR

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Assisted-by: AI coding assistant Signed-off-by: JonSnow1807 <JonSnow1807@users.noreply.github.com>

JonSnow1807 requested review from AndreasKaratzas, DarkLight1337, jeejeelee and ywang96 as code owners August 20, 2026 18:26

claude Bot reviewed Aug 20, 2026

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JonSnow1807 mentioned this pull request Aug 20, 2026

[Feature]: Enable LoRA support for tower and connector in more MM models #31479

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mergify Bot added multi-modality Related to multi-modality (#4194) glm labels Aug 20, 2026

linitra24 reviewed Aug 21, 2026

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JonSnow1807 added 2 commits August 22, 2026 05:24

Remove GLM-ASR LoRA tests per review feedback

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Assisted-by: AI coding assistant Signed-off-by: JonSnow1807 <JonSnow1807@users.noreply.github.com>

Set supports_tower_connector_lora after vllm-project#53092

bf05f01

Assisted-by: AI coding assistant Signed-off-by: JonSnow1807 <JonSnow1807@users.noreply.github.com>

zupengwang mentioned this pull request Aug 24, 2026

[Bugfix][LoRA] Restore tower and connector LoRA support for LFM2-VL #53519

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[Model] Enable LoRA support for tower and connector in GLM-ASR - #53149

[Model] Enable LoRA support for tower and connector in GLM-ASR#53149
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		@pytest.fixture(scope="module")
		def glmasr_tower_connector_loras(tmp_path_factory) -> dict[str, LoRARequest]:

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JonSnow1807 commented Aug 20, 2026 •

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