Y Combinator — funding rounds | Tiago's Bookmarks

21 Aug

Cool Company Raises · $9.0M

idler raises a $9.0M Seed round

idler is a frontier data research lab and artificial intelligence evaluation platform based in San Francisco, CA. The company develops a comprehensive evaluation and benchmarking platform that builds advanced evaluation suites, programmatic datasets, and interactive reinforcement learning environments utilized by global AI labs. It focuses on specialized software engineering, cybersecurity, recursive self-improvement, and enterprise safety testing beds.

Software Artificial-Intelligence Cyber-Security Smaiyl Makyshov Nur Bazylbekov Feross Aboukhadijeh+9 more

20 Aug

Cool Company Raises · $31.0M

Apollo Atomics raises a $31.0M Seed round

Apollo Atomics is an MIT spinoff focused on developing the next generation of pressurized water reactors (PWRs) designed for factory-based manufacturing. The company aims to deliver high power density nuclear reactors capable of providing carbon-free energy for various large-scale energy users. Their innovative approach seeks to reduce the overall reactor footprint and accelerate regulatory processes for commercialization. Apollo has established a commercial pipeline with over 20 gigawatts of signed letters of intent.

Manufacturing Energy Renewable-Energy Ray Rothrock Matteo Franceschetti Philip Johnston+11 more

12 Aug

Cool Company Raises · $45.0M

Blacksmith raises a $45.0M Series B round

Blacksmith makes CI faster, more cost-effective, and more reliable by avoiding hyperscaler-based solutions and running GitHub Actions on high-performance hardware with gaming-grade CPUs — tuned for maximum throughput and enhanced with growing observability capabilities. This approach eliminates build bottlenecks, lowers infrastructure costs, and gives teams a clear view into pipeline health. In the AI era, where rapid iteration is critical, Blacksmith keeps development cycles moving — enabling faster validation, safer deployments, and more competitive release schedules. Founded in 2024 by engineers from Faire and Cockroach Labs, Blacksmith is backed by Google Ventures, Y Combinator, and leading dev infrastructure angels.

Software Gv Y Combinator Peak Xv Partners $10M+

11 Aug

Cool Company Raises · $1.1B

River AI raises a $1.1B round

River AI is a full-stack AI company founded by xAI co-founder Igor Babuschkin. The company focuses on building powerful personal AI and providing tools for developers and companies to train, tune, and serve their own AI models. River AI aims to give ownership of AI directly to users.

Software Artificial-Intelligence Machine-Learning Temasek Y Combinator Amd Ventures+7 more

28 Jul

Cool Company Raises · $21.0M

Array Labs raises a $21.0M Series A round

Array Labs is an advanced aerospace company developing the satellites, sensors, and software required to deliver the first real-time, high-fidelity 3D map of Earth. Its innovative approach leverages distributed radar, formation flight, multi-static SAR imaging, and advanced image formation algorithms to provide unprecedented insights into the planet's surface. Raytheon, an RTX business, creates next-generation defense solutions for various applications, including space and surveillance. Umbra Space specializes in high-resolution Earth observation technologies, focusing on delivering advanced mapping capabilities.

Manufacturing Software Aerospace Y Combinator Kompas Vc Catapult Ventures+2 more

27 Jul

Cool Company Raises · YC S26

Gutgutgoose launches at YC (Summer 2026)

AI training infrastructure via custom probiotics

Biotech Personalization Health-Wellness Y Combinator Healthcare YC+1 more

25 Jul

Cool Company Raises · $2.6M

Writesonic raises a $2.6M Seed round

Writesonic, Inc. is an AI Search Visibility Platform that helps brands track and improve their online presence across various AI platforms. Founded in 2021 by Samanyou Garg, the company evolved from a basic AI copywriting tool to encompass SEO content and chatbot functionalities. It has raised between $2.6 million and $3.1 million in total funding and is known for its user-friendly interface and various integrations. The platform offers a 7-day free trial for new users.

Artificial-Intelligence Machine-Learning Natural-Language-Processing Amino Capital Hof Capital Plug And Play+4 more

23 Jul

Cool Company Raises · YC S26