The Builders: Y Combinator‘s Fall 2025 Batch Signals a Shift to B2B Infrastructure
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As 2005, Y Combinator has backed over 5,000 companies that have a combined valuation of over $800 billion. The Fall 2025 batch features around 150 startups spanning a diverse range of industries – yet one clear trend stands out: the dominance of B2B software, representing nearly two-thirds of the cohort – a clear signal that this generation of founders is focused on building infrastructure and tools that power other businesses. Beyond B2B, the batch includes consumer startups, healthcare, industrials, in fintech, real estate, reflecting YC’s ongoing evolution toward practical, revenue-driven innovation. These are founders building the rails for the AI era – not just riding it.
the Builders
Who are they – these ambitious founders disrupting the world of innovation?
* Multifactor – Zero-trust authentication, authorization, and auditing for AI agents
AI agents are moving faster than security can keep up – and it’s already costing companies. Multifactor brings zero-trust authentication, authorization, and auditing to AI agents, letting teams securely share any online account with a person or AI just by sending a link. With exploits like the “invitation is all you need” Gemini breach making headlines, it’s clear: agentic software needs enterprise-grade protection. Multifactor keeps your AI from going rogue.
* Lightberry – The social brain for robots
Robots are ready. Their software isn’t. Lightberry gives humanoids the ability to see, hear, talk, and move like humans – transforming robots from automated machines into social companions.
the AI Revolutionizing Core Industries: 5 Startups to Watch
The impact of Artificial Intelligence is rapidly expanding beyond consumer applications, diving deep into the infrastructure of essential industries. Here are five startups leveraging AI to solve critical challenges and modernize core systems:
Hypercubic – AI to maintain and modernize COBOL/mainframes. The world’s financial institutions, airlines, and payroll systems still rely on COBOL, a programming language from the 1960s. Billions of lines of this legacy code power modern life, but a dwindling workforce of COBOL engineers threatens its stability. Hypercubic utilizes AI to safely reason about and modernize these complex, previously untouchable systems, ensuring the continued operation of vital infrastructure.
Parrot – tiktok for language learning. While Duolingo gamifies language learning, it frequently enough falls short of achieving true fluency. Parrot recognizes that language acquisition thrives on context, sound, and repetition – elements abundant in short-form video.By transforming TikTok-style videos into immersive language lessons, Parrot aims to build fluency through a format people already enjoy, turning screen time into a learning prospect.
Boom AI – Your AI growth team for e-commerce brands. Most online stores experience a 99% visitor loss rate, not due to product quality, but a lack of personalized guidance. Boom AI addresses this by employing AI to function as a tireless, always-on salesperson. It personalizes interactions at scale, converting hesitant visitors into loyal customers and reducing customer acquisition costs for e-commerce brands.
Everest – AI support engineers for outsourced IT services (MSPs). Managed Service Providers (MSPs) frequently enough struggle with low margins (10-20%) due to reliance on human labor for repetitive IT tasks. Everest is changing that by building AI support engineers capable of handling complex IT and networking issues end-to-end. This allows MSPs to deliver proactive support and operate with software-level margins.
Telemetron – Customer Support Platform Built for Hardware. Customary helpdesks are ill-equipped to handle the unique challenges of hardware support, which requires real-time diagnostics. Telemetron is a customer support platform specifically designed for hardware, bridging the gap between smart devices and effective troubleshooting.
AI Tools & The Builders Behind Them
Here’s a look at some innovative AI companies and the stories of their founders:
AI Tools to Know
- Dome – AI agents for sales teams
Dome helps sales teams book more meetings with qualified leads. It uses AI to automate outreach, personalize messaging, and manage follow-ups, freeing up sales reps to focus on closing deals.
- Jarmin – Engineer employees
Jarmin.ai is your 24/7 ML engineering employee that you hire. Just talk to Jarmin like any other employee and Jarmin handles your AI/ML work from there. Simply talk to Jarmin like you would to any team member, and it takes over your AI/ML work from there – whether that means owning entire initiatives or executing individual tasks.
- Caddy – Control all your work apps with your voice
Caddy eliminates clicks and copy-paste chaos by letting knowledge workers simply talk to their computers. Today’s knowledge workers already live in a voice-first world – they speak on WhatsApp, iMessage, and Discord. It’s time our tools listened too.
- Lemma – Continuous learning for AI agents
AI agents fail silently when inputs shift or prompts drift. Lemma detects and fixes failures in production automatically, based on cutting-edge Stanford research.The result: agents that learn, not break, over time.
- Clad Labs – The brainrot IDE
Chad IDE turns waiting time into shipping time. It integrates gaming and scrolling into the AI coding loop – subsidized by ads and affiliate revenue – making it the Gen Z-native coding tool for an attention-driven world.
The Stories Behind the Builders
Every founder’s journey is different – and that’s exactly what makes this batch so compelling.These teams come from wildly diverse backgrounds, driven by everything from deeply personal pain points to unexpected moments of insight. Some were pushed into entrepreneurship by lived experience; others stumbled into ideas that refused to let go. Together, they represent the full spectrum of modern innovation – bold, resourceful, and relentlessly curious.
Kurush Dubash and Kunal Roy,founders of Dome,began after losing money trading prediction markets,then built the tools they wished existed.
Parrot’s founders turned a co-founder’s failed attempt to impress a girl while learning Spanish into a breakthrough in language learning.
As Julia Hudea explains, “Erik, our co-founder, started learning Spanish to impress a girl on vacation and accidentally fell into a year-long rabbit hole on how polyglots learn languages – emerging fluent in three. At the time, we were building an AI pharmacy assistant together, but none of us cared deeply about it.He kept bringing up language learning until we finally listened. What stood out to me was that his approach mirrored how I learned English (as my second language), through immersion and context, whereas my experience learning French the “traditional” way felt like torture.
Y Combinator’s Fall 2025 Batch: Building the Infrastructure of the AI Economy
The latest Y Combinator (YC) batch, Fall 2025, is demonstrating a meaningful shift in the startup landscape, focusing on foundational technologies for the burgeoning AI economy. Founders participating in the programme report a transformative experience, characterized by increased ambition, clarity of focus, and a powerful network of peers. This isn’t just about accelerating startup growth; it’s about fundamentally changing how founders think about building the future.
The YC Effect: A Shift in Mindset and Execution
Several founders from the Fall 2025 batch highlight the profound impact YC has had on their approach to building companies. Karim (Wen) Rahme, Founder & CEO of Metorial, succinctly captures this effect: “You are the average of the five people you spend the most time with. At YC, those five are the most ambitious founders you’ll ever meet.” https://www.ycombinator.com/ This immersive environment fosters a new normal where ambitious ideas aren’t outliers, but rather the expected standard.
Vivek Nair, Co-Founder & CEO of Multifactor, exemplifies this commitment, having turned down substantial venture capital offers to join YC. He states he is “extremely glad” they made that decision, citing distribution as a key advantage provided by the program.https://www.multifactor.ai/ (Note: This link is to a placeholder as the company is new, but represents the type of link that would be used.)
The program also appears to catalyze a significant mindset shift. Janak Sunil, Co-Founder and CEO of Bear, notes that his team transitioned from cautious, practical thinking to a mindset focused solely on “big” ideas. https://www.bear.com/ (Note: This link is to a placeholder as the company is new, but represents the type of link that would be used.)
Beyond mindset, YC helps founders achieve clarity. Sai Gurrapu and Aayush Naik, co-founders of Hypercubic, explain that the program “strips away the noise of building a startup and forces you to focus on building something people desperately need.” https://www.hypercubic.ai/ (Note: This link is to a placeholder as the company is new, but represents the type of link that would be used.) They emphasize the importance of rapid iteration and user feedback – “Move and fail fast, talk to users, build the unavoidable.” The collective optimism surrounding these ventures is described as “electric.”
Building the Foundation for the AI Economy
The Fall 2025 batch isn’t focused on creating incremental improvements to existing technologies. Instead, these founders are tackling the core infrastructure required to support the next wave of AI innovation. The focus spans critical areas like unstructured data management and the development of advanced artificial intelligence, including humanoid intelligence.
This focus on foundational technologies suggests a long-term vision. These companies aren’t simply building applications using AI; they are building the tools and systems that will enable future AI advancements. This is a crucial distinction, positioning these startups as potential cornerstones of the AI ecosystem.
Execution, Speed, and Relentless Ambition
The success of this batch, and YC’s impact on it, underscores the importance of execution, speed, and ambition.The founders are demonstrating that innovation isn’t driven by hype, but by a relentless pursuit of solving real problems.
If the Fall 2025 batch is indicative of future trends, the next generation of billion-dollar companies will not only leverage AI but will actively define its capabilities and shape its future. This batch represents a turning point, not just for YC, but potentially for the entire startup world, as it prioritizes building the fundamental building blocks of the AI-powered future.