AI collections agency for late-stage portfolios
HQ: San Francisco, CA, United States | Founded: 2025 | Employees: 7 | Stage: Seed (Y Combinator S26) | Website: https://callbook.ai
Callbook AI is a debt collection agency run by AI. It collects on late-stage portfolios by locating borrowers, contacting them and negotiating repayment. The company's stated method is to research and understand each borrower's situation in depth before negotiating, which it says makes it consistently beat competing collections services. Reported results include negotiating with more than 100,000 people every week, delivering its best recorded recovery at every company it has worked with, and winning 100% of head-to-head pilots against competing services. Founded in 2025 and based in San Francisco with 7 employees. Chief executive Diego Avellaneda is an applied machine learning researcher with two peer-reviewed papers on deep learning and embedded systems — on-device indoor tracking, and low-cost embedded sensing — a master's in IoT applying machine learning to real-time truck telemetry, and more than six years in embedded machine learning. He was previously a senior software engineer at CI&T, where he built Audi's online car-purchasing platform, and is a second-time founder. Daniel Martinez, founder and product lead, was previously chief product officer at Treble (YC S19). Y Combinator's primary partner was Jon Xu.
Collections is a good fit for AI agents: high volume, conversational, paper-heavy, and currently staffed by large human call centres with poor economics. Callbook's approach differs in a way that matters in practice — it researches each borrower's situation first, then negotiates, instead of dialling from a script. That is the difference between a nuisance caller and something a lender will trust with its brand and its legal exposure. The traction claims are specific: more than 100,000 people a week in negotiation and a perfect record in head-to-head pilots. The catch is regulation — collections is one of the most tightly policed consumer finance activities in the United States.
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