kaggle-vllm

kaggle-vllm is a lightweight Python SDK and compatibility toolkit around upstream vLLM for Kaggle's NVIDIA Tesla T4 environment. It validates the runtime, protects Kaggle's preinstalled PyTorch/CUDA stack during explicit artifact staging, wraps vllm.LLM, inspects vLLM-native persistent sharded checkpoints, and safely launches vLLM's OpenAI-compatible server.

It is not a fork, reimplementation, or replacement for vLLM. Inference, tensor parallelism, sharded-state persistence, and serving remain upstream vLLM capabilities.

Status: v0.1 release candidate. Functionally validated on the documented Kaggle dual-T4 environment. PyPI publication is pending Trusted Publisher configuration; it is not described as production-ready.

Validated environment

The archived 2026-08-22/23 Kaggle runs recorded:

The generated wheel is:

vllm-0.18.2.dev0+ga26e8dc7f.d20260822.cu128-cp312-cp312-linux_x86_64.whl
SHA256 5a9bd710b8a19fdd23abb3442baad892da977466f996334decd533a225f5fd0c

The source identity and distribution version are not contradictory. The source checkout is upstream v0.18.1 at the commit above; the wheel filename/version is generated build metadata from vLLM's setuptools_scm configuration, which reported the next development version plus Git/date and local CUDA metadata. It does not mean the source was the upstream v0.18.2 release.

Install the lightweight SDK

The SDK is published on PyPI and has no hard dependency on vLLM, Torch, or CUDA. The primary Kaggle flow is:

pip install kaggle_vllm
kaggle-vllm bootstrap

The one-line form is:

pip install kaggle_vllm && kaggle-vllm bootstrap

The canonical distribution spelling is equivalent:

python -m pip install kaggle-vllm

pip install kaggle_vllm installs only the small kaggle-vllm distribution; Python packaging normalizes _ and - in project names. The explicit bootstrap command then downloads the exact native wheel from the Hugging Face Hub/Xet-backed repository, checks its immutable revision and SHA256, stages it with pip --target --no-deps, and creates the validated dependency overlay. It never replaces or reinstalls Kaggle's Torch packages.

Importing kaggle_vllm never downloads or installs anything. The native wheel is CPython 3.12 (cp312) and bootstrap rejects Python 3.11 even though the lightweight SDK itself can be developed and tested with Python 3.11. An immutable Hugging Face SDK fallback is documented in installation.

Inspect the complete plan without network or filesystem changes:

kaggle-vllm bootstrap --dry-run --strict

Python inference API

from kaggle_vllm import KaggleLLM

llm = KaggleLLM(
    model="Qwen/Qwen2.5-3B-Instruct",
    tensor_parallel_size=2,
    max_model_len=2048,
    gpu_memory_utilization=0.70,
)
outputs = llm.generate(["Explain tensor parallelism."], sampling_params)

KaggleLLM lazily imports and wraps upstream vllm.LLM. It validates the TP degree against visible GPUs and forwards advanced keyword arguments. The SDK supplies the conservative settings validated on Kaggle T4 by default:

dtype="float16"
enforce_eager=True
disable_custom_all_reduce=True

These are validated conservative defaults for this Kaggle T4 configuration, not claims of universal optimality. Every value can be overridden explicitly.

Tensor parallelism is not persistent sharding

Runtime tensor parallelism partitions model execution across visible devices:

KaggleLLM(model="Qwen/Qwen2.5-3B-Instruct", tensor_parallel_size=2)

A persistent TP-aware checkpoint is a different artifact. The experiment used vLLM's native save_sharded_state machinery to write rank-specific files:

model-rank-0-part-0.safetensors
model-rank-0-part-1.safetensors
model-rank-1-part-0.safetensors
model-rank-1-part-1.safetensors

Save and inspect one through the wrapper:

inspection = llm.save_sharded_model(
    "/kaggle/working/qwen2.5-3b-t4x2-sharded"
)
print(inspection.rank_count)  # 2

Reload using the topology for which it was created:

llm = KaggleLLM(
    model="/kaggle/input/qwen2.5-3b-t4x2-sharded",
    tensor_parallel_size=2,
    load_format="sharded_state",
    max_model_len=2048,
    gpu_memory_utilization=0.70,
)

This is not arbitrary tensor splitting, uneven 1/3–2/3 GPU allocation, or a claim of topology-independent portability. See persistent sharded state.

Explicit native bootstrap and activation

Normal dependency resolution can replace Kaggle's tightly coupled Torch/CUDA packages. Bootstrap uses the packaged kaggle-t4x2-cu128 profile and pins the native artifact to Hugging Face commit f6b4f10de54924ed6fe9e28cceab84eca7276ab6:

kaggle-vllm bootstrap --strict
eval "$(kaggle-vllm env)"  # optional for subsequent shell commands

By default it uses /kaggle/working/vllm-staged, /kaggle/working/vllm-runtime-overlay, and /kaggle/working/kaggle-vllm-cache; every path is overridable. The packaged overlay lock is the exact small reproducibility input from the successful Kaggle recovery. Bootstrap rejects torch, torchvision, and torchaudio entries, writes a runtime manifest, and refuses incompatible non-empty runtime directories. KaggleLLM may activate an already-completed default manifest, but it never bootstraps implicitly. See installation.

Kaggle CUDA-driver discovery

The toolkit was at /usr/local/cuda-12.8, while the mounted live driver was /usr/local/nvidia/lib64/libcuda.so. CMake found the toolkit but initially did not expose CUDA::cuda_driver. The successful build made the driver directory visible with:

export CMAKE_LIBRARY_PATH=/usr/local/nvidia/lib64

The source-build scripts retain this workaround. The wheel itself is excluded from Git.

OpenAI-compatible serving

The server helper creates an argument array and invokes upstream vllm serve without a shell:

kaggle-vllm serve /kaggle/input/qwen2.5-3b-t4x2-sharded \
  --served-model-name qwen2.5-3b-kaggle-t4x2 \
  --load-format sharded_state \
  --tensor-parallel-size 2 \
  --dtype float16 \
  --max-model-len 2048 \
  --gpu-memory-utilization 0.70 \
  --host 127.0.0.1 \
  --port 8001

The archived Qwen run returned HTTP 200 from both GET /v1/models and POST /v1/chat/completions. See OpenAI serving.

What was functionally validated

• CUDA-enabled vLLM wheel build and SHA256 verification
• staged native imports (vllm._C, vllm._moe_C, allocator)
• isolated dependency overlay while preserving system PyTorch
• single-T4 FP16 inference with facebook/opt-125m
• raw two-rank NCCL all-reduce (3.0 on both ranks)
• real vLLM TP=2 inference with facebook/opt-125m
• Qwen/Qwen2.5-3B-Instruct FP16 TP=2 inference
• persistent TP=2 sharded-state creation and reload
• OpenAI-compatible TP=2 serving from the sharded Qwen checkpoint

The curated evidence is in artifacts/kaggle-2026-08-23, with the larger immutable evidence and model archives kept outside Git.

Tesla T4 / SM75 behavior

FlashAttention 2 requires compute capability 8.0 or newer and was unavailable on SM75. vLLM selected TRITON_ATTN in the recorded runs. SymmMem communicator warnings are also expected because that capability is unavailable on SM75; ordinary NCCL communication and TP=2 inference still completed successfully.

CLI

kaggle-vllm doctor
kaggle-vllm fingerprint
kaggle-vllm bootstrap [--strict] [--dry-run]
kaggle-vllm env [--manifest PATH]
kaggle-vllm verify-gpus --tensor-parallel-size 2
kaggle-vllm inspect-shards PATH --json
kaggle-vllm verify-wheel PATH [--sha256 DIGEST]
kaggle-vllm stage-wheel PATH --target TARGET [--sha256 DIGEST]
kaggle-vllm serve MODEL ...

Artifact distribution and security

Verified release artifacts are published separately from the source repository:

• validated Kaggle dual-T4 vLLM wheel and metadata
• Qwen2.5-3B-Instruct TP=2 persistent sharded state

Large wheels, archives, safetensors, caches, overlays, and extracted models are ignored by Git. Published artifacts must carry checksums, compatibility data, and upstream attribution. Never commit Kaggle, GitHub, or Hugging Face tokens. The Qwen persistent checkpoint remains governed by the non-commercial Qwen Research License included with the model, not this repository's Apache-2.0 license.

Known limitations

• Validation is specific to the tabled Kaggle environment and CPython 3.12 ABI.
• The SDK supports Python 3.10+, but the published native wheel profile is Linux x86_64 CPython 3.12 only.
• No local GPU test is claimed; GPU results come from archived Kaggle evidence.
• The persistent model is TP-topology-aware and validated only at TP=2.
• The copied upstream HF weight index names original HF shards; standard Transformers loading is not supported. Use vLLM sharded_state.
• Eager execution/custom all-reduce settings were conservative correctness choices, not performance benchmarks.
• No arbitrary or uneven GPU-memory split API is provided.
• Qwen redistribution/use is non-commercial under its included license.

More detail: architecture, runtime, tensor parallelism, validation, and the compatibility matrix.