Arcee AI hits $1B+ valuation with Series B for American open-weight models

Arcee AI said it closed a Series B led by Vista Equity Partners, Cambium Capital, and Emergence Capital that values the company at more than $1 billion. The San Francisco lab builds frontier open-weight models (including Trinity Large) and says the capital will accelerate the next Trinity generation, expand work with the U.S. Department of Energy and national labs, and grow products for customizing and running open models.

SOFTWARE desk — same-day company primary that a U.S. open-weight lab crossed a $1B+ valuation while arguing frontier models can be built for far less than hyperscaler burn, with Vista/Cambium/Emergence and strategic corporates backing the next Trinity generation and DOE work.

Participating investors named on the same company pages, still company: AI10 Ventures, Hitachi, IAG, M12, P7, and Wipro. Fortune’s same-day exclusive, by Allie Garfinkle, names M12 as Microsoft’s M12. None was printed on the company pages.

Use of proceeds, as the company tells it: accelerate the next generation of the Trinity model family, already in training; expand work with the U.S. Department of Energy and its national laboratories, with Genesis-Science-1 as a starting point and the Genesis Open Models Initiative named on the GlobeNewswire; and grow products that help organizations customize, evaluate, deploy, and operate open models.

Product context, still company: Arcee says it builds frontier open-weight foundation models from the ground up in the United States. Open-weight means the trained model weights — the numbers that make the model work — are released so others can run and adapt them. The company says the Trinity family scaled in about six months from a 4.5 billion-parameter dense model to Trinity Large, a 400 billion-parameter mixture-of-experts model. Dense here means every part of the model runs on each token. Mixture-of-experts, or MoE, means only some specialist slices of the model fire for each token, which can cut the compute bill. Arcee calls Trinity Large a permissively licensed U.S. Model, and says it is the first of its kind since Meta stopped releasing Llama models in early 2025.

Build-cost claim, company — not an independent audit: Arcee says its entire 2025 model lineup, including Trinity Large, was built for approximately $20 million. That figure, the company says, includes salaries, compute, data, infrastructure, and operations.

Round size: Arcee did not disclose the dollars raised. Fortune reported the Series B at a $1 billion pre-money valuation and said a source familiar with the matter put the raise at at least $150 million. Pre-money means the implied worth before the new cash is counted in. Secondary write-ups that flatten Fortune’s “at least $150 million” into a confirmed raise stay off the lead.

Their other quotes are color only and stay in Sources. This is not investment advice.

Plain English for the rest of the card: Series B = a growth venture round after Series A. valuation = what investors imply the whole company is worth. open-weight = model weights released so others can run and adapt them. MoE = mixture-of-experts, an architecture that uses only some slices of the model at a time. DOE = U.S. Department of Energy. national lab = a government research lab in that DOE system. pre-money = implied worth before the new cash is counted in. parameter = one of the trained numbers inside a model.