Bespoke Labs raises $40M to build the training grounds for reliable AI agents

AI agents can write code and answer questions, but they still fall apart on long, messy jobs. A Mountain View startup just raised $40M to build the training grounds that fix that.

Bespoke Labs, which builds the environments that train and test AI agents, has raised $40 million, the company announced. The total spans a Series A led by Wing VC and an earlier seed led by 8VC. The backer list is unusually pointed: angels who work at Anthropic, OpenAI, and Meta, plus Google DeepMind’s Jeff Dean and dbt Labs chief Tristan Handy.

Practice grounds for agents

Today’s agents are capable but unreliable. They handle short tasks well. They still struggle to work on their own over hours or days, the way a colleague would. Bespoke’s bet is that the fix is not a bigger model but a better place to practise.

So it builds simulated versions of real firms: large codebases, microservices, logs, support tickets, email, and Slack threads. Agents train inside these worlds and learn the long, multi-step workflows that actually earn their keep. Bespoke then helps customers measure and tune them, using an in-house optimiser it calls GEPA to find better prompts and policies faster than hand-tuning allows.

A research lab, not a contractor shop

Founded in 2024 by CEO Mahesh Sathiamoorthy and chief scientist Alex Dimakis, the roughly 40-person team leans academic. It is a core contributor to Terminal-Bench, a widely cited test of agent skill. It also built OpenThoughts, an open reasoning dataset that labs including Meta and Amazon have downloaded more than 500,000 times.

Rather than farm the work out to contractors, Bespoke treats environment-building as research and sells the infrastructure that results.

Why it matters

Bespoke timed this deliberately. Independent tests from METR find the length of tasks agents can reliably finish now doubles roughly every seven months, and Tech Funding News notes some analyses now put that closer to every four. Sustaining that curve means environments that grow harder just as fast, and that is exactly what Bespoke sells.

Rivals crowd the field. They attack agent reliability from every angle, from self-learning agents to firms that stress-test, test, and benchmark them before they ship. Others chase the economics of running agents at scale. Bespoke is wagering that the training ground, not the model, decides which agents reach production.

Whether better environments really beat bigger models is still an open question. The answer will help decide which of these companies survives the next funding cycle.