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Apertus 1.5 8B

Swiss AI Initiative (Apertus) · Apertus · released 2026-07-24 · data checked 2026-11-01 Needs verification

Apertus 1.5 8B is a 8.9B-parameter dense model from Swiss AI Initiative (Apertus) (Europe), released 2026-07-24 under the Apache-2.0 license. It scores 20.1 on the Small LM Index, #24 of 26 small models. It needs about 7.2 GB of memory at 4-bit with an 8K-token context.

Fully open: weights, training data and recipes. Trained for 1,000+ languages by EPFL, ETH Zurich and CSCS.

Small LM Index
20.1
#24 of 26 scored small models
Likely 14.5–27.7 · from 2 of 6 core benchmarks
Parameters
8.9B
Dense
Price per 1M tokens
—
No hosted API on OpenRouter; self-host
Context window
262K
tokens

Benchmarks

Each bar shows this model's score. The tick marks the best small model on that benchmark. Sources: 2 reported by Swiss AI Initiative (Apertus). How we label sources.

MMLU-Pro Lab-reported Knowledge48.8
Class best: Qwen3.5 9B 82.5
GPQA Diamond Lab-reported Knowledge · GPQA (subset not stated)27.2
Class best: Qwen3.5 9B 81.7

Not reported: estimated

What the index model expects from this model's other scores. Not a measurement.

Humanity's Last Exam≈ 1
AIME≈ 16
LiveCodeBench≈ 20
SWE-bench Verified≈ 6

Specifications

Lab
Swiss AI Initiative (Apertus) (CH · Europe)
Architecture
Dense transformer
Total parameters
8.9B
Active parameters
All (dense)
Size class
Small
Context window
262K tokens
Input modalities
text, image, audio
Reasoning
Hybrid (thinking on/off)
License
Apache-2.0
Openness
Fully open: weights, training data and code
Memory to run
~7.2 GB at 4-bit, 8K context (more sizes)
Hugging Face
42K downloads (30 days) · 171 likes

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Sources

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Run it locally

No GGUF build from a well-known publisher yet.

vLLM (GPU server)
vllm serve swiss-ai/Apertus-v1.5-8B
Full-precision weights, for a server GPU.

Memory needed: weights, context cache and runtime buffers (context cache estimated: attention layout not published).

Quantization4K context32K context256K context
16-bit F1619 GB23 GB54 GB
8-bit Q8_011 GB15 GB46 GB
4-bit Q4_K_M6.6 GB11 GB42 GB

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