Borealis 2 26B-A4B (Preview)

Release: August 21st, 2026.

Model summary

NbAiLab/borealis2-26b-a4b-preview is a 26B-parameter (4B active) instruction-tuned preview model intended for early testing and feedback. It is an experiment and should be treated as pre-release quality.

The model starts from google/gemma-4-26B-A4B-it, continued pre-trained on Aurora 2604 data, and then supervised fine-tuned for two epochs on textual instructions from NbAiLab/aurora-sft-2606. SFT loss is calculated on assistant responses only.

Training data

Continuous pre-training uses aurora, a mix of sources both internal and external, including license materials under agreements. Supervised fine-tuning (SFT) uses NbAiLab/aurora-sft-2606. Examples use the Gemma 4 chat template; user and system tokens are masked from the training loss.

The aurora dataset finished building in April 2026 and contained a total of 47B whitespace-separated words with a knowledge cutoff of January 1st 2025.

Sources

Word counts

Source\Language Total nob nno dan swe eng fao isl sme non fin smn sma smj sms fkv sju other
Total 47,588,939,435 24,310,675,244 11,121,117,598 4,635,647,954 2,466,930,277 2,418,581,785 1,534,499,832 618,403,302 136,625,254 130,821,960 115,529,546 26,099,190 25,054,850 19,392,470 11,725,220 10,308,610 42,900 7,483,443
hplt-3.0 15,020,676,845 7,387,980,881 1,650,457,860 3,406,653,847 1,945,721,769 241 386,912,020 161,832,408 509,882 39,453,060 37,167,967 633,100 46,480 152,950 15,170 3,139,210 - -
fineweb-2 14,616,279,115 9,586,371,459 3,739,975,210 - - 91 814,239,570 273,740,521 52,936,570 47,996,140 62,367,474 11,890,230 9,333,600 5,615,090 6,946,090 4,826,690 40,380 -
nb-newspapers-mbl 6,403,459,654 3,222,919,898 3,179,351,370 36,981 12,848 205,425 - 539 76,101 1,090 102 - 551,030 27,710 - 276,560 - -
finepdfs 5,885,083,486 3,031,393,119 1,161,632,350 757,427,249 416,681,332 3,914 280,421,310 181,277,900 16,222,925 13,795,380 15,306,017 2,480,840 1,423,800 4,614,610 2,057,710 345,030 - -
maalfrid-crawl 994,747,286 492,399,964 482,117,030 565,919 39,357 9,450,493 - - 5,264,213 188,860 - - 2,787,440 1,902,390 - 31,620 - -
swallow-code-v2 848,043,875 42,982 12,429 16,500,328 429,047 827,993,226 2,432 10,507 424 - 76,313 - - - - - - 2,976,187
nb-books-ocr 817,147,445 220,740,790 459,992,080 96,760,244 448,854 1,267,865 601,140 - 7,256,662 29,052,580 - - 714,070 313,160 - - - -
megamath 795,092,965 3,201 6,419 858,060 201,115 789,418,493 - - 12,292 - 86,129 - - - - - - 4,507,256
fineweb-2-hq 439,744,102 66 - 344,871,624 94,872,412 - - - - - - - - - - - - -
finewiki 425,260,298 83,273,602 210,355,610 11,313,266 8,520,965 97,669,581 8,341,750 1,526,141 206,149 45,590 525,544 3,482,100 - - - - - -
maalfrid-government 382,884,652 175,367,608 204,521,790 158,061 1,319 602,180 - 1,486 1,204,748 - - - 453,730 236,870 - 336,860 - -
fineweb-edu 358,894,808 - - - - 358,807,998 - - - 86,810 - - - - - - - -
fineweb-hq 290,431,291 1,036 - - 228 290,244,437 - - - 185,590 - - - - - - - -
giellalt 112,384,962 3,616,964 2,479,390 20,829 1,031 - 43,981,610 13,800 34,305,758 16,860 - 7,612,920 9,744,700 6,529,690 2,706,250 1,352,640 2,520 -
parlamint 69,692,697 69,256,627 436,070 - - - - - - - - - - - - - - -
kudos 59,909,727 31,938,952 27,698,540 - - 191,476 - - 80,759 - - - - - - - - -
project-gutenberg 42,718,920 - - - - 42,718,920 - - - - - - - - - - - -
saami-web 18,548,893 - - - - 122 - - 18,548,771 - - - - - - - - -
lovdata 5,748,677 3,702,797 2,045,880 - - - - - - - - - - - - - - -
patents 1,132,943 1,132,671 - 272 - - - - - - - - - - - - - -
nb-digimanus 1,056,794 532,627 35,570 481,274 - 7,323 - - - - - - - - - - - -

Before upsampling

Source\Language Total nob dan swe eng nno isl fao fin sme non smn sma smj sms fkv sju other
Total 35,903,335,353 24,310,675,244 4,635,647,954 2,466,930,277 2,418,581,785 1,112,128,723 618,403,302 153,452,172 115,529,546 42,158,387 13,082,196 2,609,919 2,505,485 1,939,247 1,172,522 1,030,861 4,290 7,483,443
hplt-3.0 13,147,596,474 7,387,980,881 3,406,653,847 1,945,721,769 241 165,045,786 161,832,408 38,691,202 37,167,967 158,376 3,945,306 63,310 4,648 15,295 1,517 313,921 - -
fineweb-2 10,402,853,593 9,586,371,459 - - 91 373,997,521 273,740,521 81,423,957 62,367,474 16,287,748 4,799,614 1,189,023 933,360 561,509 694,609 482,669 4,038 -
finepdfs 4,553,779,407 3,031,393,119 757,427,249 416,681,332 3,914 116,163,235 181,277,900 28,042,131 15,306,017 5,012,773 1,379,538 248,084 142,380 461,461 205,771 34,503 - -
nb-newspapers-mbl 3,541,220,733 3,222,919,898 36,981 12,848 205,425 317,935,137 539 - 102 24,164 109 - 55,103 2,771 - 27,656 - -
swallow-code-v2 848,043,875 42,982 16,500,328 429,047 827,993,226 12,429 10,507 2,432 76,313 424 - - - - - - - 2,976,187
megamath 795,092,965 3,201 858,060 201,115 789,418,493 6,419 - - 86,129 12,292 - - - - - - - 4,507,256
maalfrid-crawl 552,781,457 492,399,964 565,919 39,357 9,450,493 48,211,703 - - - 1,622,990 18,886 - 278,744 190,239 - 3,162 - -
fineweb-2-hq 439,744,102 66 344,871,624 94,872,412 - - - - - - - - - - - - - -
nb-books-ocr 370,533,410 220,740,790 96,760,244 448,854 1,267,865 45,999,208 - 60,114 - 2,248,354 2,905,258 - 71,407 31,316 - - - -
fineweb-edu 358,816,679 - - - 358,807,998 - - - - - 8,681 - - - - - - -
fineweb-hq 290,264,260 1,036 - 228 290,244,437 - - - - - 18,559 - - - - - - -
finewiki 225,114,542 83,273,602 11,313,266 8,520,965 97,669,581 21,035,561 1,526,141 834,175 525,544 62,938 4,559 348,210 - - - - - -
maalfrid-government 197,068,531 175,367,608 158,061 1,319 602,180 20,452,179 1,486 - - 382,952 - - 45,373 23,687 - 33,686 - -
parlamint 69,300,234 69,256,627 - - - 43,607 - - - - - - - - - - - -
project-gutenberg 42,718,920 - - - 42,718,920 - - - - - - - - - - - - -
kudos 34,922,645 31,938,952 - - 191,476 2,769,854 - - - 22,363 - - - - - - - -
giellalt 21,681,541 3,616,964 20,829 1,031 - 247,939 13,800 4,398,161 - 10,586,259 1,686 761,292 974,470 652,969 270,625 135,264 252 -
saami-web 5,736,876 - - - 122 - - - - 5,736,754 - - - - - - - -
lovdata 3,907,385 3,702,797 - - - 204,588 - - - - - - - - - - - -
patents 1,132,943 1,132,671 272 - - - - - - - - - - - - - - -
nb-digimanus 1,024,781 532,627 481,274 - 7,323 3,557 - - - - - - - - - - - -

⚠️ Safety / alignment disclaimer (important)

This is a preview experiment and has not been completely safety-aligned. The model may produce harmful, biased, or insensitive content, including content that is offensive, unsafe, or inappropriate. Do not use it for safety-critical or high-stakes applications, and add your own safety mitigations if deploying.

Intended use

  • Norwegian-centric assistant-style tasks, including drafting, summarization, Q&A, and light reasoning.
  • Assessment of Norwegian writing style and quality.
  • Early evaluation of behaviour, language coverage (Norwegian, Bokmål, Nynorsk, and English), and quality.

Limitations

  • Preview quality; outputs may be unstable and may hallucinate.
  • Not safety-aligned; the model may follow harmful instructions or generate problematic content.
  • This release is an early SFT checkpoint, not a final production model.

Weights & formats

Transformers (original)

  • NbAiLab/borealis2-26b-a4b-preview (safetensors).

License

The license of this model is an adaptation of the Apache 2.0 license with additional use-based restrictions. In particular, users of the model are required to refrain from intentionally using the model to recreate data the model has been trained on. The license also requires users not to use the model or its output to provide end-user services whose primary purpose is to give access to licensed press publications in the training data.

For more information, see the LICENSE and the License FAQ.

Acknowledgements

Thanks to the Gemma team at Google and to everyone contributing feedback on this preview.

Disclaimer

These models may have bias and/or any other undesirable distortions. When third parties, deploy or provide systems and/or services to other parties using any of these models (or using systems based on these models) or become users of the models, they should note that it is their responsibility to mitigate the risks arising from their use and, in any event, to comply with applicable regulations, including regulations regarding the use of artificial intelligence. In no event shall the owner of the models (The National Library of Norway) be liable for any results arising from the use made by third parties of these models.

Contact

For feedback, technical concerns, or collaboration inquiries, please contact ailab@nb.no.

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