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Silmaril

YC X26

San Francisco, US · Founded 2026 · 2 employees · 9 known investors

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Silmaril is a security monitoring and threat detection platform that protects enterprise systems by identifying and blocking malicious tool calls and prompt injection attacks.

Also known as Silmaril Security Inc.

CybersecurityEnterprise SoftwareUnited States of AmericaAmerica / Canada

Founders & leadership· Y Combinator alumni (X26)

Silmaril was founded in 2026 by Aum Upadhyay and Eduardo Velasco.

AUAum Upadhyay
Aum UpadhyayCo-Founder & CEOAum Upadhyay previously worked on security and privacy frameworks at AWS. He is now co-founder and CEO of Silmaril, where he focuses on prompt injection defense.
EVEduardo Velasco
Eduardo VelascoCTOEduardo Velasco is a former tech lead at Amazon with expertise in low-latency machine learning systems. He is co-founder and CTO of Silmaril.

Investors · 9

Y Combinatorlisted by Y CombinatorSan Francisco · $500K

How we know: the Y Combinator directory · open dataset · 5k.vc investor directory · Not right? Tell us

Blast.Clubreported$5.5M

How we know: Y Combinator's founder network · Not right? Tell us

Greylock PartnersreportedSan Francisco · $100K – $10M

How we know: Y Combinator's founder network · Not right? Tell us

Metsu Capitalreported

How we know: Y Combinator's founder network · Not right? Tell us

RobinhoodreportedMenlo Park

How we know: Y Combinator's founder network · Not right? Tell us

Seven Hill VenturesreportedSan Francisco

How we know: Y Combinator's founder network · Not right? Tell us

Spot VCreportedNewark

How we know: Y Combinator's founder network · Not right? Tell us

SV AngelreportedSan Francisco · $150K – $20M

How we know: Y Combinator's founder network · Not right? Tell us

Legal entities · 1

corporate structure
Silmaril Security Inc.

In the news

The 11 standout startups from YC's Demo Day, according to VCstechcrunch.com · Jun 2026Silmaril: Self-healing Prompt Injection Defenseycombinator.com · Apr 2026Silmaril Funding | Complete Analysis | Extruct AIextruct.ai

Frequently asked questions

What does Silmaril do?
Silmaril is a security monitoring and threat detection platform that protects enterprise systems by identifying and blocking malicious tool calls and prompt injection attacks.
Who founded Silmaril?
Silmaril was founded by Aum Upadhyay, Eduardo Velasco in 2026.
Who are Silmaril's investors?
Silmaril's investors include Transpose Platform Management, Y Combinator, Blast.Club, Greylock Partners, Metsu Capital, Robinhood, Seven Hill Ventures, Spot VC and 1 more.
Where is Silmaril headquartered?
Silmaril is headquartered in San Francisco, US.