@xuster
General Partner @YCombinator, Co-Founder @FutureAdvisor (YC S10), MIT EECS
Y Combinator @ycombinatorApplied Electrodynamics is building cameras that can see through walls and other opaque materials. Using radio waves, they can locate studs, pipes, cables, and junction boxes behind surfaces like drywall or marble and turn it into a dimensionally accurate 3D model.
Y Combinator @ycombinatorWe’re excited to welcome @vivianmshen and @raphaelschaad as YC’s newest General Partners! Vivian and Raphael first came to YC as founders. Vivian co-founded Juni Learning (W18), which teaches kids coding and math, and later founded Acely, an AI tutor for college prep. Raphael founded Cron (W20), the calendar app that became Notion Calendar. They built products used by millions of people, then returned to YC as Visiting Partners to help other founders. Now they're doing it full-time.
Y Combinator @ycombinatorHalluminate is building reinforcement learning environments and benchmarks to help AI models do knowledge work beyond coding, starting with finance. With a team of fewer than 10 people, the company works with four of the top five closed-source US AI labs and recently raised a $30M Series A. In this fireside, co-founders @Jerr_Wu and @wgm752 sit down with YC's @xuster to share how testing browser agents led them to building the environments models now use to practice tasks like financial modeling. They explain why better verification, not just more training tasks, is critical to making models smarter, and how that work could eventually lead to simulated companies where teams of AI agents learn to work together. 00:00 — Halluminate’s Pivot From Evals to Training Environments 03:48 — Teaching AI to Do Financial Work 07:13 — Why Verification Matters More Than Volume 10:13 — From Finance to Simulated Companies 13:30 — AI Safety and Building the Team
Tunga Bayrak @TungaBayrakToday we’re releasing Adam and Eve, the most human-like AI voices ever built. Adam ranks #1 among AI models on @DesignArena’s AudioRealismBench. We believe we’ve crossed the uncanny valley. API access on our Website! Listen: Leaderboard: Special thanks to @alpsencerozturk, @ahmeterdempmk, and the entire Freya team for making this possible. We’re just getting started. Join us!
Alex @alexytungOfficially a YC Alum! Experience of a lifetime. > Met the best mentor ever @xuster > 5x’d ARR > Built something people want > Took 25 flights all over the US > Met many friends and future unicorn founders
Zach AL @zachdotaiWe got into @ycombinator 3 months ago with zero revenue and today @FabraixHQ is at $1.04M annualised run rate. Traditional cybersecurity was built for software that behaves within defined boundaries. AI agents can reason, use tools, take actions, and find ways around those boundaries. The cost asymmetry we're seeing in irl warfare is also now a software problem. So we built autonomous red-teaming agents that find real vulnerabilities in AI agents that work 24/7, powered by our own state-of-the-art offensive models that outperform frontier models. AI agents are automating all knowledge work. @FabraixHQ is the adversarial testing infrastructure that will secure every production agent.
Y Combinator @ycombinatorIntroducing the YC Early Access Network. 4x a year, senior technology leaders get early looks at YC's enterprise AI companies and help shape their roadmaps. Invite-only, by application. Fall '26 kicks off Oct 22 in SF. Apply now:
David Eckstein @davidnecksteinThe momentum continues at @WeAreLegora ...we beat our original Q3 '26 plan a full month early. July was the strongest quarter-opening month in Legora's history, and August was even larger. Total net new ARR grew 36% MoM. But the story of the month is in-house teams. ARR from in-house is up 15x+ YoY, average ARR per in-house customer is up 2.5x+ YoY, and in-house teams are now almost half of our total new customers. Most importantly, you earn ARR by building the best product on the market. Our usage climbs every month: 16+ hours per monthly active user. In September, we expect to add more ARR than in all of Q1 '26 combined, which would make Q3 the best quarter in our history and capture yet another ARR milestone. LFG!
Y Combinator @ycombinatorIn 2013, @cjoneslevy created the SAFE at YC. It's since been used by YC founders to raise $15B+ and has become the standard way startups raise money. So we're launching Send a SAFE: a free tool to generate, sign, & send one in ~2 minutes, built to be used by founders (and their AI agents).
Aerogen Systems @AerogenSystemsWe’re launching Aerogen Systems on YC today. We put modular reactor purifiers inside chipmaking tools to keep wafers clean without a cleanroom. Talos cleans the tools. The Cleanpipe connects them. Find us here:
