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Callbook AI

YC S26

San Francisco, US · Founded 2025 · 7 employees · 4 known investors

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Callbook AI provides AI agents that contact and negotiate with borrowers across calls, SMS, and email to handle debt collections. It segments accounts by ability and willingness to pay and routes customers to the right next step, serving financial institutions.

AI & Machine LearningEnterprise SoftwareFintechSaaSAIUnited States of AmericaAmerica / CanadaFully Remote

Founders & leadership· Y Combinator alumni (S26)

Callbook AI was founded in 2025 by Diego Avellaneda and Daniel Martinez.

DADiego Avellaneda
Diego AvellanedaCEO & FounderDiego Avellaneda is the founder and CEO of Callbook AI, with over six years in embedded machine learning and two peer-reviewed publications on TinyML and embedded sensing. He holds a master's in IoT focused on applying TinyML to real-time truck telemetry and previously worked as a Senior Software Engineer at CI&T, where he helped build Audi's e-commerce car-purchasing platform.
DMDaniel Martinez
Daniel MartinezFounder & ProductFounder and product lead at Callbook AI, previously CTO there and Chief Product Officer at Treble (YC S19). Has spent over five years leading B2B products.

Investors · 4

Vela Partnerslisted by Vela PartnersSan Francisco · $100K – $500K
Y Combinatorlisted by Y CombinatorSan Francisco · $500K

How we know: the Y Combinator directory · Not right? Tell us

Founders FactoryreportedLondon · $150K – $200K

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

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Companies working in the same space as Callbook AI.

In the news

Callbook AI: The AI collections agency for late stage portfoliosycombinator.com · Aug 2026

Frequently asked questions

What does Callbook AI do?
Callbook AI provides AI agents that contact and negotiate with borrowers across calls, SMS, and email to handle debt collections. It segments accounts by ability and willingness to pay and routes customers to the right next step, serving financial institutions.
Who founded Callbook AI?
Callbook AI was founded by Diego Avellaneda, Daniel Martinez in 2025.
Who are Callbook AI's investors?
Callbook AI's investors include Pygma, Vela Partners, Y Combinator, Founders Factory.
Where is Callbook AI headquartered?
Callbook AI is headquartered in San Francisco, US.