rl-list.com · Vendors · Sepal AI
Sepal AI
Commercial medium confidence
www.sepalai.com ↗ · Status: acquired confirmed · Founded 2024
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.
Key facts
Headquarters
San Francisco, USAconfirmed cite
Headcount band
unknown cite
Total raised
$500Kreported cite
Last round
Pre-seed, ~$500K, 2024-09-25 (per Crunchbase aggregator; not independently confirmed by a primary announcement)reported cite
SOC 2
unknown
What they sell
mixedconfirmed cite
Open source
noestimated
Deployment
unknown
Founding team
Robi (Robert) Lin
Co-Founder
At Turing.com, built enterprise workflow products and scaled the LLM-trainer business from 50 to 800+ developers; previously at Bain & Co.
Kat Hu
Co-Founder
Built the go-to-market for Turing's foundational LLM-trainer business and managed 500+ AI trainers; previously at McKinsey.
Fedor Paretsky
Co-Founder
Early engineer at Vercel; built foundational infrastructure at Newfront; also lists Mosaic. Joined Mercor through the Sepal acquisition, per his personal site, which says he is 'currently working on RL environments'.
What practitioners should know
For researchers
- Sepal's main public artifact is SheetBench-50 (2025-10-01, co-built with HUD): 50 expert-validated financial spreadsheet tasks with cell-level verification. It is on Hugging Face as hud-evals/SheetBench-50. The dataset card does not credit Sepal and notes a migration to HUD v6, so legacy v5-format rows may not run on current HUD.
- No Sepal-authored papers or open-source repositories found.
For program managers
- Acquired by Mercor (announced 2026-02-06; terms undisclosed). Engagements now go through Mercor, not Sepal.
- Mercor's announcement calls Sepal 'a trusted partner to frontier AI labs and early enterprise teams' but names no labs. The YC profile says Sepal had 'multiple Fortune 500s and top AI research labs as paying customers' (self-claimed) and links a Sepal X post saying it supported Anthropic's Claude 3.7 Sonnet launch with pre-launch testing. That claim is self-claimed and could not be opened for verification (X returned 402).
- Funding: aggregators report one ~$500K pre-seed round (2024), while the YC profile says 'several million dollars'. Nothing new appeared in the April to October 2026 window, and no Sepal-branded news was found.
For data ops
- sepalai.com, including /careers, returned HTTP 404 on 2026-10-05, so there are no Sepal docs, APIs or security pages to evaluate. Use Mercor's materials instead.
- No SOC 2 or other certification was ever published under the Sepal brand.
Benchmarks & research
SheetBench-50benchmark · 1 Oct 2025
Public benchmark of 50 spreadsheet tasks covering financial-analyst workflows, run in a real Chrome/Google Sheets environment: Data Preparation and Hygiene (29), Derivations & Extraction (16), Modeling & Forecasts (5). Built by HUD and Sepal AI together. Tasks were blind-validated: three experts, finance professionals from PwC, Cisco, Charles Schwab and Fannie Mae (including CFO-level reviewers), solved each task independently so that each has one consensus answer. Answers are checked at the cell level.
The case study publishes no headline score. It links to a HUD leaderboard and an example Claude scorecard.
Products
Sepal AI expert data, evaluation and RL-environment services (legacy, now inside Mercor) ↗
Expert-sourced training data, expert-graded evaluation benchmarks and RL environments. The YC profile also describes a 'Cloud-Native Agent Dataset Factory' and a self-claimed network of 20k+ experts across STEM and professional services. Since the February 2026 acquisition these are no longer offered as a standalone product, and sepalai.com returned HTTP 404 on 2026-10-05.launched 2024
Scale & velocity
Current headcount
~13-15 core team (YC team size 15; getlatka 13 for 2024). LinkedIn public snippet shows 51-200 band (likely includes contract experts)reported cite
Headcount growth
unknown
Open roles
unknown (sepalai.com/careers returns 404; Sepal no longer hires as a standalone company, and hiring presumably runs through Mercor)estimated cite
Other locations
unknown
Distributed / remote
unknown
Research depth
Has researchers
yesreported cite
Researcher count
unknown
Backgrounds
Co-founders ex-Turing (built and scaled the LLM-trainer business; Robi Lin scaled trainers from 50 to 800+; Kat Hu managed 500+ AI trainers), Co-founder Robi Lin formerly at Bain & Co.; co-founder Kat Hu formerly a McKinsey consultant, Co-founder Fedor Paretsky: early engineer at Vercel, also Newfront and Mosaic; now works on RL environments after the Mercor acquisition (self-published on fedor.me), Engages a self-claimed network of 20k+ academic PhDs and domain professionals (STEM, medical, finance, business)reported cite
Capital
Total raised
~$500K disclosed (single pre-seed round, Sep 2024) per aggregators; YC profile separately states 'several million dollars from leading investors' (unresolved conflict)reported cite
Last round
Pre-seed, ~$500K, 2024-09-25 (per Crunchbase aggregator; not independently confirmed by a primary announcement)reported cite
Investors
Y Combinator, Metaplanet Holdings, SID Venture Partners, Sterling Road, Team Ignite Venturesreported cite
Valuation
unknown
Revenue signals
Third-party (getlatka) claims ~$2M revenue with a 13-person team in 2024, single unverified source, not vendor-confirmedreported cite
Security & compliance
SOC 2
unknown
Other certifications
unknown
Security page
unknown
Product
What they sell
mixedconfirmed cite
Open source
noestimated
License
unknown
Deployment model
unknown
Maturity
Discontinued as a standalone offering (absorbed into Mercor after the Feb 2026 acquisition)estimated cite
Notable customers
⚑Top AI research labs (unnamed; frontier-lab ties referenced in Mercor acquisition rationale) self-claimed Multiple Fortune 500 companies (unnamed) self-claimed HUD (co-builder/collaboration partner on SheetBench-50, NOT a customer) verified cite
Buyer analysis
Best fit: Buyers needing expert-validated evaluation environments and RL/training data for complex domains (notably finance/spreadsheet analyst workflows and advanced science), note the team is now part of Mercor following the Feb 2026 acquisition.
How we verified this
2026-10-05 refresh: I re-fetched every draft source. The YC profile confirms status 'Acquired', team size 15, the founders and their backgrounds, and a 'several million dollars' self-claim. Orrick confirms the Mercor acquisition on 2026-02-06 with terms undisclosed. Mercor's LinkedIn post confirms the deal and calls Sepal a partner to 'frontier AI labs and early enterprise teams', which corrects the draft's wording. The HUD case study and the HF dataset card confirm SheetBench-50's details. I tested sepalai.com myself: www, apex and /careers all return 404. Corrections: I dropped the out-of-window acquisition news item, which status_change already covers. I blanked the photos for Robi Lin and Kat Hu: the YC avatars resolve, but one is an obscured grayscale shot and the other a distant full-body hiking photo, neither a clear headshot. I identified the third co-founder as Fedor Paretsky from his personal site, which cross-links the same LinkedIn handle as YC, and added his verified GitHub avatar. I changed the open-roles '0' to unknown. I also added the self-claimed, unverified Claude 3.7 Sonnet pre-launch testing link from the YC profile. Looking for missed items, Mercor's blog (posts through 2026-10-01) has nothing Sepal-specific. The web-search budget was exhausted, so I could not run broad discovery searches, and an in-window Mercor-side mention of the Sepal team could have been missed. Even so, nothing material appears to have happened to Sepal in the window.
Related vendors
Sources
- www.ycombinator.com/companies/sepal-ai · 2026-10-05, YC profile: status Acquired, team size 15, SF, S24. Founders Robi Lin, Kat Hu and Fedor, with backgrounds and LinkedIn links. Self-claims of 'several million dollars' raised and Fortune 500 / AI-lab paying customers. Latest-news link to a Sepal X post on Claude 3.7 Sonnet pre-launch testing.
- www.orrick.com/en/News/2026/02/Mercor-Acquires-Sepal-AI · 2026-10-05, Orrick advised Mercor. Acquisition dated 2026-02-06; terms not disclosed. Describes Sepal as a data development platform for training data, eval benchmarks and RL environments.
- www.linkedin.com/posts/mercor-ai_today-were-welcoming-sepal-ai-to-mercor · 2026-10-05, Mercor post welcoming Sepal: 'trusted partner to frontier AI labs and early enterprise teams'. No labs named.
- www.sepalai.com/ · 2026-10-05, HTTP 404; https://sepalai.com/ and /careers also 404
- www.hud.ai/case-studies/sheetbench-50 · 2026-10-05, SheetBench-50 case study: released 2025-10-01, built by HUD and Sepal AI, task breakdown, three-expert blind validation
- huggingface.co/datasets/hud-evals/SheetBench-50 · 2026-10-05, Dataset card: 50 rows, Parquet, validated by professionals from PwC, Cisco, Schwab and Fannie Mae, migrated to HUD v6; does not mention Sepal
- fedor.me · 2026-10-05, Fedor Paretsky's personal site: co-founder of Sepal AI (YC S24, acquired by Mercor), ex-Vercel, Mosaic and Newfront; links GitHub @f3d0r and LinkedIn @f3d0r
- github.com/f3d0r · 2026-10-05, GitHub profile of Fedor Paretsky (website fedor.me). The avatar is a clear real photo, used as his headshot.
- www.mercor.com/blog/ · 2026-10-05, Mercor blog checked for Sepal-related posts in the window: none found. Latest posts run up to 2026-10-01.
- www.sepalai.com/careers · 2026-06-07, Careers page; open roles incl. Applied Research Engineer, Senior/Fullstack SWE (402 on direct fetch, partial via LinkedIn/YC)
- www.crunchbase.com/organization/sepal-ai · 2026-06-07, Crunchbase profile (403 on fetch; via search) - funding & investors
- www.crunchbase.com/funding_round/sepal-ai-pre-seed--fda22c6a · 2026-06-07, Pre-seed round dated 2024-09-25, ~$500K
- startupintros.com/orgs/sepal-ai · 2026-06-07, Investors: Metaplanet Holdings, SID Venture Partners, Sterling Road, Team Ignite Ventures, YC
- www.linkedin.com/company/sepalai · 2026-06-07, Public snippet: HQ San Francisco, 51-200 employee band (likely incl. contract experts), Technology/Information/Internet
- getlatka.com/companies/sepalai.com · 2026-06-07, Third-party unverified claim: ~$2M revenue, 13-person team, 2024
- pitchbook.com/profiles/company/639950-14 · 2026-06-07, PitchBook profile (valuation/investors/acquisition) - via search snippet
Last updated 2026-10-05 · Every quantitative field carries a source and a confidence tag. Fields we could not source publicly are marked unknown, never estimated. See the methodology.