On October 3, 2026, Heidelberg-based artificial intelligence pioneer Aleph Alpha delivered a historic milestone for European technological sovereignty with the release of Kolibri-1. Released under the unencumbered Apache 2.0 license, Kolibri-1 is an open-weight, highly sparse Mixture-of-Experts (MoE) foundation model designed from the ground up to operate within the strict regulatory and data privacy boundaries of the European Union while matching the computational efficiency of global frontier models.
At the heart of Kolibri-1's design is an aggressive fine-grained Mixture-of-Experts architecture. While the model encompasses 78.1 billion total parameters, its router directs incoming token representations to just 6 active experts out of a total pool of 384 routed experts. This results in an active inference footprint of approximately 3.46 billion parameters per token. By combining extreme parameter sparsity with grouped-query attention (GQA) and shared attention heads, Kolibri-1 delivers the expressive capacity of an 80B-class dense model at the inference throughput and FLOP cost of a lightweight 3B edge model.
To solve the chronic 'token tax' that standard English-centric tokenizers impose on European languages, Aleph Alpha engineered a bespoke 128,000-vocabulary UniBPE tokenizer. In German, Dutch, and Nordic languages—where compound noun formation frequently fractures standard Byte-Pair Encodings into 3 to 5 disjoint subwords—the UniBPE tokenizer reduces token count by 34%, drastically lowering latency and context memory pressure during large-scale enterprise document indexing.
Contextually, Kolibri-1 is trained natively on a 262,144-token horizon using YaRN rotary position embedding scaling, with needle-in-a-haystack pass rates validated up to 1,048,576 tokens. Furthermore, the model incorporates native test-time reasoning compute scaling, offering developers four explicit reasoning modes (None, Low, Medium, High) that dynamically expand chain-of-thought scratchpad budgets for complex symbolic and legal analysis.
In standardized academic and STEM benchmarks, Kolibri-1 demonstrated exceptional Pareto efficiency. The model recorded 80.0% on MMLU-Pro, 96.0% on AIME 2026 with high reasoning effort, 92.7% on HumanEval+, and 70.8% on the Aleph Alpha German Enterprise Benchmark, outperforming comparably sized sparse models and establishing a new sovereign open-weights benchmark.
Crucially, the entire training pipeline—encompassing data filtering, synthetic instruction curation, pre-training, and Direct Preference Optimization (DPO)—was executed strictly on European infrastructure across data centers in Germany and Finland. The weights contain zero exposure to proprietary transatlantic telemetry, ensuring complete compliance with Article 53 of the EU AI Act and GDPR cross-border transfer prohibitions. The weights are immediately available on Hugging Face at Aleph-Alpha/Kolibri-1.