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14,448 startups · 29 programs

Thirdlayer

Active · Continual learning for enterprise AI

WebsiteYC profile

Why it ranks

How the rank works
9signal of 100 · rising 5
  • went through YCProgram · this site+4
  • team of 2Team size · YC's directory+2.5
  • hiringHiring · Titles (titles.fru.dev), YC+2

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

Competitors

AIMiruvor AIShared: continual learning500 Global SF 37United StatesStartup →AIMonteShared: continual learning, agent, buildingYC S25San FranciscoStartup →AIProper MotionShared: continual learning, agent, interactionspeedrun SR007San FranciscoStartup →AIAshrShared: continual learning, enterprise, continuouslyYC W26San FranciscoStartup →AITraceShared: give agent, productivity, contextYC S25LondonStartup →
Companies closest to Thirdlayer
Company
Miruvor AIShared: continual learning500 Global SF 37Not statedAI
MonteShared: continual learning, agent, buildingYC S25ActiveAI, Devtools
Proper MotionShared: continual learning, agent, interactionspeedrun SR007Not statedAI
AshrShared: continual learning, enterprise, continuouslyYC W26ActiveAI, Data
TraceShared: give agent, productivity, contextYC S25ActiveAI

Adjacent

AIHopperShared: organizational contextBetaworks AI Camp: App LayerStartup →Developer toolsFernShared: continual learning, improveYC W26Startup →AIAutoresearch, Inc.Shared: continual learning, agent, evaluationYC S26San FranciscoStartup →OtherautoneShared: operational processes, complex operational, ingestYC S22LondonStartup →AIKeystrokeShared: internal agent, then, buildingYC W24Salt Lake CityStartup →
Companies next to Thirdlayer
Company
HopperShared: organizational contextBetaworks AI Camp: App LayerNot statedAI
FernShared: continual learning, improveYC W26ActiveDevtools
Autoresearch, Inc.Shared: continual learning, agent, evaluationYC S26ActiveAI, Devtools
autoneShared: operational processes, complex operational, ingestYC S22 +1ActiveOther
KeystrokeShared: internal agent, then, buildingYC W24ActiveAI, Data, Devtools

Also from W25 in AI

All of W25
AIInactiveOliveBuild internal tools with AIYC W25San FranciscoStartup →AI.WaveInference for real-time AIYC W25ParisStartup →AI10xAI Sales Teams for Dental PracticesYC W25San FranciscoStartup →AIa0.devWe make mobile apps using AI.YC W25San FranciscoStartup →AIA1Zap by A1BaseThe social network layer for AI appsYC W25San FranciscoStartup →AIAdamAI Powered CADYC W25San FranciscoStartup →
Company
OliveBuild internal tools with AIteam of 2InactiveAI
.WaveInference for real-time AIteam of 2ActiveAI, Devtools
10xAI Sales Teams for Dental Practicesteam of 3hiringActiveAI, Data
a0.devWe make mobile apps using AI.team of 3hiringActiveAI, Devtools
A1Zap by A1BaseThe social network layer for AI appsteam of 2ActiveAI, Devtools
AdamAI Powered CADteam of 4hiringActiveAI, Devtools

Founders

  • Regina LinFounder/CEO
  • Kevin GuFounder

About Thirdlayer

ThirdLayer is the learning and alignment layer for enterprise AI. We continuously ingest and structure messy organizational context, complex operational processes, and siloed, permission-sensitive data, then grade agents against the outcomes each company cares about. Every interaction becomes feedback that helps agents improve over time. Companies use ThirdLayer to power their internal agents or embed it into the AI products they’re building. We give agents the context, evaluations, and learning loops they need to stay aligned with each organization and deliver better outcomes with every run.

YC batch
W25 · Winter 2025
Status, per YC
Active
Category
AI
Team size
2
Location
San Francisco, CA, USA
Founded
2025
Checked
6h ago

YC tags: Productivity, Consumer Products, AI

Changes seen

TagsOct 19, 2026

No longer tagged Artificial Intelligence.

Source ↗

Thirdlayer in W25: 166 companies, 84% AI

LinkedIn

Thirdlayer: questions

Which YC batch was Thirdlayer in?

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

Is Thirdlayer still active?

Y Combinator lists Thirdlayer as active.

Who founded Thirdlayer?

Thirdlayer's founders, as listed on its YC page: Regina Lin (Founder/CEO), Kevin Gu (Founder).

Where is Thirdlayer based?

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