Sepal AI C

RL environment · Enterprise Workflows

Domains: Enterprise Workflows Long-Horizon Math
On X: @sepal_ai ↗
Funding: Y Combinator S24 · rounds and investors
Tier: C why
Snapshot: November 5, 2026

About Sepal AI

Sepal AI was a YC-backed (S24) San Francisco data-research company that built high-quality training data, expert-graded evaluation benchmarks, and reinforcement-learning environments for frontier LLMs, drawing on a network of 20k+ domain experts (PhDs, finance, medical, STEM). It was acquired by Mercor in February 2026; the team joined Mercor and its RL-environment and human-data work now sits under Mercor. It is therefore no longer ranked as an independent vendor.

Tier C

Early: a small team.

How much stands behind a tier: usage, who backs it, a confirmed line from its own site or paper, and a clear read on X. High with three of the four, medium with two, low otherwise.

team size unknown
investors: Y Combinator, Metaplanet Holdings, SID Venture Partners
went through Y Combinator Summer 2024
in curated RL directories (2 pts)

How we got to tier C

Adoption: team size unknown; investors: Y Combinator, Metaplanet Holdings, SID Venture Partners; went through Y Combinator Summer 2024. Tier C.
On X: unclear, none buzz No move.
In curated RL directories: 2 points, a floor of none.
Not yet confirmed by a line from its own site or paper.

A clear view on X moves a tier one step up or down; most entries don't move. How tiers work.

Sepal AI funding

Accelerator: Y Combinator S24

Backed byY Combinator Summer 2024

Accelerator

Y Combinator Summer 2024
1. Y Combinator's company directory lists Sepal AI with the website sepalai.com, in its Summer 2024 batch
2. Checkable on YC's page: ycombinator.com/companies/sepal-ai
3. 2 pages read also name Y Combinator
ycombinator.com/companies/sepal-ai

Every figure is quoted from its own site, its accelerator or a funding announcement; a round's amount and lead appear only when its quote states them. Startup databases are never used as evidence. Checked 2026-10-11. How funding is checked.

Not on the map yet: no line from its own site or paper places it in a domain.

Latest from Sepal AI on X

@sepal_ai ↗

At Sepal, we create RL environments and tools for Frontier Labs to evaluate models & build real-world capabilities. This is made possible by working with the world’s leading experts who contribute their skills and domain knowledge to test and evaluate models. Over the last week alone, hundreds of new experts have joined Sepal’s mission: to extend humanity’s knowledge and capabilities through the development of safe AI. If you have years of professional expertise in a domain we’re recruiting for, you want to contribute and learn more about the AI industry while making money working remotely on your own time. Join us! Apply Here:
— sepal_ai (@sepal_ai) Dec 4, 2025
Our team at Sepal AI is at NeurIPS! If you're interested in applying for a role or just want to talk, come say hi! We're hiring across dozens of industries to find the brightest in their fields to contribute to our mission. If you're ready to help develop frontier AI, join us! Apply Here:
— sepal_ai (@sepal_ai) Dec 3, 2025
Always building!
— sepal_ai (@sepal_ai) Nov 27, 2025

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Next: browse all environments. Entry from the RL Research daily scrape of public sources, 2026-11-05 snapshot.