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14,448 startups · 29 programs

ReasonBlocks

Active · Specialized models that make your AI agents cheaper and more reliable.

WebsiteYC profile

Why it ranks

How the rank works
7signal of 100 · rising 7
  • went through YCProgram · this site+4
  • team of 2Team size · YC's directory+2.5

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

Competitors

AIThirdBrain LabsShared: specialized model, training, productionspeedrun SR006San FranciscoStartup →AIFreesoloShared: specialized modelYC X25San FranciscoStartup →AIMorphShared: specialized model, routing, inferenceYC S23ColumbusStartup →AIGuide LabsShared: sacrificing performance, model, traceYC W24San FranciscoStartup →AIHopperShared: production trace, model, inferenceYC F26San FranciscoStartup →OtherSmallest.aiShared: specialized, model, agentStartup →OtherOLIXShared: model, serving, inferenceStartup →
Companies closest to ReasonBlocks
Company
ThirdBrain LabsShared: specialized model, training, productionspeedrun SR006Not statedAI
FreesoloShared: specialized modelYC X25ActiveAI, Devtools
MorphShared: specialized model, routing, inferenceYC S23ActiveAI, Devtools
Guide LabsShared: sacrificing performance, model, traceYC W24ActiveAI, Devtools
HopperShared: production trace, model, inferenceYC F26ActiveAI, Devtools
Smallest.ainot in a program hereShared: specialized, model, agentElsewhereOther
OLIXnot in a program hereShared: model, serving, inferenceElsewhereOther

Adjacent

AIZoa ResearchShared: specialized model, agentYC S24New York CityStartup →AIMatXShared: specializedAI Grant Batch 2Startup →AIInactiveSylvianShared: specialized, agentYC F25San FranciscoStartup →AIThetaShared: specializedYC X25San FranciscoStartup →AIisoquantShared: cheaper, inferenceYC F26San FranciscoStartup →
Companies next to ReasonBlocks
Company
Zoa ResearchShared: specialized model, agentYC S24ActiveAI, Data
MatXShared: specializedAI Grant Batch 2Not statedAI
SylvianShared: specialized, agentYC F25InactiveAI
ThetaShared: specializedYC X25ActiveAI
isoquantShared: cheaper, inferenceYC F26ActiveAI

Also from X26 in AI

All of X26
AIAbInitio BioThe Intelligence layer for Drug ManufacturingYC X26BostonStartup →AIAdvanced Metal ResearchMachine intelligence for American WeldingYC X26Los AngelesStartup →AIAgentPhonePhone Numbers for AI AgentsYC X26San FranciscoStartup →AIAGI Deploy CoDiffusing AI into critical industriesYC X26San FranciscoStartup →AIAkkariAutonomous Customer OperationsYC X26San FranciscoStartup →AIAlchemizeBuilding AI Native Customs BrokeragesYC X26San FranciscoStartup →
Company
AbInitio BioThe Intelligence layer for Drug Manufacturingteam of 2ActiveAI
Advanced Metal ResearchMachine intelligence for American Weldingteam of 3ActiveAI
AgentPhonePhone Numbers for AI AgentshiringActiveAI
AGI Deploy CoDiffusing AI into critical industriesteam of 2ActiveAI
AkkariAutonomous Customer Operationsteam of 5ActiveAI
AlchemizeBuilding AI Native Customs Brokeragesteam of 2ActiveAI

Founders

  • Sajeev MageshFounder/CEO

About ReasonBlocks

ReasonBlocks turns your agents’ production traces into specialized models, delivering 10× cheaper inference without sacrificing performance. We handle training, routing, and serving.

YC batch
X26 · Spring 2026
Status, per YC
Active
Category
AI
Team size
2
Location
San Francisco, CA, USA
Checked
7h ago

ReasonBlocks in X26: 194 companies, 84% AI

LinkedIn

ReasonBlocks: questions

Which YC batch was ReasonBlocks in?

ReasonBlocks was in Y Combinator's Spring 2026 batch (X26).

Is ReasonBlocks still active?

Y Combinator lists ReasonBlocks as active.

Who founded ReasonBlocks?

ReasonBlocks's founders, as listed on its YC page: Sajeev Magesh (Founder/CEO).

Where is ReasonBlocks based?

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