🔍 Read the full analysis: LFM2.5-VL-DSpark And The Drive To Accelerate Vision-Language AI on ThorstenMeyerAI.com
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TL;DR
Liquid AI released LFM2.5-VL-DSpark, an experimental 280M-parameter speculative-decoding drafter that accelerates its LFM2.5-VL-3B vision-language model by up to 3.13x on Apple silicon and 2.66x on H100 without changing outputs. It ships with day-one llama.cpp, MLX-VLM and SGLang support and is available on Hugging Face.
Liquid AI has released LFM2.5-VL-DSpark, an experimental 280M-parameter draft model that accelerates inference of the company’s open-weight LFM2.5-VL-3B vision-language model using speculative decoding. According to the company, the drafter adds just 8.9% to the target model’s parameter count while delivering decoding speedups of up to 3.13x on Apple silicon and up to 2.66x on an NVIDIA H100 — without changing output quality. The model is available now on Hugging Face in Safetensors and GGUF formats, with day-one support in llama.cpp, MLX-VLM and SGLang.
The release extends Liquid AI’s DSpark recipe — previously applied to its text-only LFM2.5 models — to a multimodal target for the first time. The drafter captures the target model’s hidden states at a fixed set of tapped layers and drafts blocks of candidate tokens conditioned on those states. Because image patches and text tokens are projected into a shared representation before the tapped layers, the drafter operates on hidden-state vectors of identical dimensionality regardless of input modality, and the inference algorithm is unchanged from the text models.
The final drafter is a simplified attention-only model with 4 layers, selected via ablations across 3, 4, and 5 layers, with a block size of 9. It was trained on a mixture of vision-language supervised fine-tuning data weighted toward expected serving workloads; Liquid AI reports that acceptance improved over 10 training epochs before reaching diminishing returns. The 280M parameters break down as a 193.0M-parameter decoder stack, a 21.0M hidden-state projection, a 65.5M Markov head, and roughly 6.4k parameters in norms and a confidence head — about 279.5M in total.
Benchmarks follow the MMSpec protocol across six vision tasks: general VQA, text VQA, image captioning, chart VQA, complex reasoning, and multi-turn conversation. On-device with MLX on an M5 Max, decoding runs 2.30x to 3.13x faster and end-to-end latency improves 1.56x to 2.62x. With llama.cpp on an M3 Ultra, decoding improves 1.57x to 2.14x and end-to-end 1.30x to 1.77x. On H100, the company reports decoding speedups ranging up to 2.66x and end-to-end gains of 1.64x to 2.27x, using a DSpark block size of 8.
Faster Vision AI on Consumer Hardware
The release targets a persistent bottleneck for local and edge AI: vision-language models are slower than text models because images must pass through a vision encoder and then be processed as hundreds of visual tokens alongside the text prompt. A drafter that roughly doubles or triples decode speed — for under 9% more parameters — could make 3B-class multimodal models practical on laptops and phones, where users feel latency directly.
Day-one integration matters as much as the speedup itself. DSpark support in llama.cpp, MLX-VLM and SGLang means the acceleration works in the toolchains hobbyists and deployers already use, rather than requiring custom inference code. Combined with Liquid AI’s open-weight licensing — download, fine-tune and deploy without restrictions, per the company — the release positions the LFM2.5 family for on-device multimodal applications.
The company is also candid about the ceiling: speculative decoding accelerates only the decode phase, not vision encoding or prefill. On edge devices with limited compute, those stages consume a larger share of wall-clock time, so end-to-end gains (1.30x–2.62x) trail decode gains — an illustration of Amdahl’s law that Liquid AI itself highlights.
From Text Drafters to Multimodal
Speculative decoding is an established technique in which a small, fast “draft” model proposes candidate tokens that the larger target model verifies in batch, accepting matching tokens and discarding the rest. Because verification is cheaper than sequential generation, accepted drafts translate into net speedup with identical outputs under greedy decoding.
Liquid AI released its first LFM2.5-DSpark drafter models for text-only LFM2.5 targets earlier in 2026. The new vision drafter reuses the same architecture and inference algorithm, differing mainly in training data and the shared multimodal representation. The LFM2.5 family spans base models, audio and vision variants, with the 3B vision model positioned as an edge-capable multimodal option.
“It adds a speculative decoding path that trades a minimal increase in memory footprint for a larger speedup without changing output quality.”
— Liquid AI, announcement post
Experimental Status and Benchmark Gaps
The release is explicitly labeled experimental, and the company has not indicated when or whether the drafter will be promoted to a stable release. The reported speedups are Liquid AI’s own measurements, not independently verified third-party benchmarks, and results will vary with hardware, prompt composition and image resolution.
One figure in the company’s GPU results appears internally inconsistent — a lower bound described as “20.4x” in a range stated as “20.4x to 2.66x” — which reads as a typo, likely for 2.04x; Liquid AI has not clarified the figure. It is also unclear how acceptance rates behave on out-of-distribution vision tasks, how the drafter affects sampling-based (non-greedy) generation quality, and what the memory footprint increase is in runtime terms beyond parameter count. Details of the training data mixture have not been published.
Community Uptake and Clarifications
The model and required integration patches are public: SGLang support requires a build with DSpark for LFM2.5 targets (PR #40651), llama.cpp requires PR #29339, and MLX-VLM requires PR #2280. Early adopters will likely publish independent benchmarks in the coming weeks, which should clarify how the company’s figures hold up across varied hardware and workloads. Whether Liquid AI promotes the drafter from experimental to stable — and whether it extends DSpark to larger or additional multimodal targets in the LFM2.5 family — remains to be seen.
Key Questions
What is LFM2.5-VL-DSpark?
An experimental 280M-parameter draft model from Liquid AI that accelerates inference of the LFM2.5-VL-3B vision-language model through speculative decoding, adding 8.9% to the target’s parameter count.
Does speculative decoding change the model’s outputs?
No — the target model verifies every proposed token, so greedy output matches the target alone. Effects on sampling-based (non-greedy) generation quality have not been characterized.
How much faster is it?
According to Liquid AI’s own benchmarks: decoding up to 3.13x faster on an M5 Max (end-to-end up to 2.62x), 1.57x–2.14x decoding on an M3 Ultra with llama.cpp, and up to 2.66x decoding on an H100. These figures are not independently verified.
Where can I use it?
The model is on Hugging Face in Safetensors and GGUF formats, with day-one support in llama.cpp (PR #29339), MLX-VLM (PR #2280) and SGLang (PR #40651). The licensing permits download, fine-tuning and deployment without restrictions, per the company.
Why are end-to-end gains smaller than decoding gains?
Speculative decoding speeds up only the decode phase, not vision encoding or prefill. On edge devices those stages take a larger share of total time, so overall latency improvements trail decode speedups — an Amdahl’s law effect Liquid AI itself notes.
Primary source: Hugging Face · via ThorstenMeyerAI.com
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