The story of Basalt started the same way many Hexa companies begin: with a problem everyone felt, but no one had truly owned.
While Guillaume Marquis, CEO & Co-founder of Basalt, was working on Virtual Brain, his previous startup, he noticed that his team was constantly copying and pasting prompts from Notion or Google Sheets into the code whenever they wanted to test a change, even a tiny one. Basalt began as a simple prompt registry to speed up this process and quickly test new LLMs as soon as they were released.
When Matthieu Vaxelaire decided to partner with co-founders Guillaume and Francois de Fitte to launch Basalt, they realized that the real problem wasn’t just adjusting prompts, it was iterating based on what was actually happening with users. They understood that AI engineering has nothing in common with traditional software development: it requires a continuous loop between observation and experimentation, without which quality quickly plateaus.
And without that loop, there is no such thing as reliable AI.
Where AI breaks and why Basalt exists
AI agents fail at scale today for two simple reasons. First, reaching high-quality performance requires continuous iteration, not the linear, predictable workflow of traditional software, but a constant loop between observation and experimentation. Most teams aren’t equipped for that.
Second, the tools meant to evaluate AI quality are built almost exclusively for engineers, shutting out the people who understand the edge cases best: PMs, operators, domain experts.
That’s where Basalt comes in.
Basalt gives teams a shared environment to experiment, evaluate, and monitor their AI agents and products together.
This collaborative approach is already resonating with companies like Swan and HealthHero. Basalt is the first collaborative AI Engineering Platform, designed to help companies reach 99% quality on their AI apps.
Fuel for the mission
To bring this vision to life, Basalt has raised a $5M seed round led by Entourage and Peak, with Alpha Star and Kima joining the journey. It’s still early days, but as with so many Hexa companies, you can feel the momentum: founders who can’t let go of the problem, and a product that quietly converts every team that tries it.
The AI world doesn’t just need more agents. It needs agents you can trust.
Basalt is building exactly that.