Top accelerator startups

Startups14,448Programs29

14,448 startups · 29 programs

Osmosis

Active · Reinforcement Learning (RL) for AI Agents

WebsiteYC profile

Why it ranks

How the rank works
10signal of 100 · rising 6
  • team of 6Team size · YC's directory+4.4
  • went through YCProgram · this site+4
  • hiringHiring · Titles (titles.fru.dev), YC+2

A sum of public facts, not a judgement and not investment advice.

Competitors

Developer toolsVmaxShared: reinforcement learning, infrastructureSPC 2025San FranciscoStartup →Developer toolsPreference ModelShared: reinforcement learning, infrastructureSPC 2025San FranciscoStartup →AICartpoleShared: reinforcement learning, training, modelYC X25San FranciscoStartup →AIAutoresearch, Inc.Shared: compute orchestration, post training, reinforcement learningYC S26San FranciscoStartup →AIRunRLShared: reinforcement learning, model, rewardYC X25San FranciscoStartup →OtherPrime IntellectShared: reinforcement learning, compute, agentStartup →OtherTwelveLabsShared: foundation modelStartup →
Companies closest to Osmosis
Company
VmaxShared: reinforcement learning, infrastructureSPC 2025Not statedDevtools
Preference ModelShared: reinforcement learning, infrastructureSPC 2025Not statedDevtools
CartpoleShared: reinforcement learning, training, modelYC X25ActiveAI, Data
Autoresearch, Inc.Shared: compute orchestration, post training, reinforcement learningYC S26ActiveAI, Devtools
RunRLShared: reinforcement learning, model, rewardYC X25ActiveAI, Devtools
Prime Intellectnot in a program hereShared: reinforcement learning, compute, agentElsewhereOther
TwelveLabsnot in a program hereShared: foundation modelElsewhereOther

Adjacent

AIAviroShared: post training, reinforcement learning, modelYC X25San FranciscoStartup →OtherPhantasma LabsShared: reinforcement learningEF 2018BerlinStartup →AITrainLoopShared: reinforcement learning, fine, performanceYC W25San FranciscoStartup →AIUnsloth AIShared: reinforcement learning, infrastructure, trainingYC S24San FranciscoStartup →AICueBenchShared: post training, reinforcement learning, performanceYC S26San FranciscoStartup →
Companies next to Osmosis
Company
AviroShared: post training, reinforcement learning, modelYC X25ActiveAI
Phantasma LabsShared: reinforcement learningEF 2018Not statedOther
TrainLoopShared: reinforcement learning, fine, performanceYC W25ActiveAI, Devtools
Unsloth AIShared: reinforcement learning, infrastructure, trainingYC S24ActiveAI, Devtools
CueBenchShared: post training, reinforcement learning, performanceYC S26ActiveAI, Data

Also from W25 in AI

All of W25
AI.WaveInference for real-time AIYC W25ParisStartup →AIAgentin AIFoundational model researchYC W25San FranciscoStartup →AIBezelDigital AI humans that model clothes for e-commerce brands.YC W25New York CityStartup →AIDextoAWS for AI AgentsYC W25San FranciscoStartup →AIExlaBuilding agents that reads logs and fixes issues on your behalf.YC W25San FranciscoStartup →AIHUDPlatform and marketplace for RL environments and AI dataYC W25San FranciscoStartup →
Company
.WaveInference for real-time AIteam of 2ActiveAI, Devtools
Agentin AIFoundational model researchteam of 2ActiveAI
BezelDigital AI humans that model clothes for e-commerce brands.ActiveAI
DextoAWS for AI Agentsteam of 2ActiveAI, Devtools
ExlaBuilding agents that reads logs and fixes issues on your behalf.team of 2ActiveAI, Devtools
HUDPlatform and marketplace for RL environments and AI datateam of 24hiringActiveAI, Devtools

Founders

  • Kasey ZhangFounder/CEO
  • Andy LyuFounder/CTO

About Osmosis

Osmosis is a post-training platform that helps companies fine-tune language models using reinforcement learning. We work with fast-growing AI companies to train task/domain-specific models that beat foundation models on performance, cost, and latency. Our platform handles compute orchestration, reward modeling, and training run observability as a CLI-based product usable by developers and agents.

YC batch
W25 · Winter 2025
Status, per YC
Active
Category
AI, Developer tools
Team size
6
Location
San Francisco, CA, USA
Founded
2024
Checked
6h ago

YC tags: Machine Learning, Reinforcement Learning, Infrastructure, AI

Changes seen

TagsOct 19, 2026

Newly tagged AI; no longer tagged Artificial Intelligence.

Source ↗

Osmosis in W25: 166 companies, 84% AI

LinkedIn

Osmosis: questions

Which YC batch was Osmosis in?

Osmosis was in Y Combinator's Winter 2025 batch (W25).

Is Osmosis still active?

Y Combinator lists Osmosis as active.

Who founded Osmosis?

Osmosis's founders, as listed on its YC page: Kasey Zhang (Founder/CEO), Andy Lyu (Founder/CTO).

Where is Osmosis based?

Osmosis lists San Francisco, CA, USA as its location on YC's directory.